Società Italiana di EEG e Neurofisiologia clinica, annual autumn meeting

Società Italiana di EEG e Neurofisiologia clinica, annual autumn meeting

76P Electroencephalography and clinical Neurophysiologr', 1989, 72: 76P-86P Elsevier Scientific Publishers Ireland, Ltd. EEG 02291 Society proceedi...

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76P

Electroencephalography and clinical Neurophysiologr', 1989, 72: 76P-86P Elsevier Scientific Publishers Ireland, Ltd.

EEG 02291

Society proceedings

Societh Italiana di EEG e Neurofisiologia Clinica, annual autumn meeting Parma, 8-10 October 1987

Secretary: Dr. Luigi Murri Servizio di Neurofisiopatologia, l/)Tiversity ,~[ Pisa, Via Roma, 56100 Pisa (Italy) (Received for publication: 5 September 1988)

1. Selective micro-structural modifications of sleep under conditions of acoustic perturbation. - M.G. Terzano, L. Parrino, G. Fioriti, M.C. Spaggiari, S. Anelli, T. Arcelloni and G. Ambiveri (Dept. of Neurology and U S L N4, Parma)

Within the organization of normal N R E M sleep, it is possible to distinguish 2 complementary functional states, each characterized by a peculiar EEG arrangement: (a) the cyclic alternating pattern (CAP), correlated with long-lasting fluctuations of arousal level and autonomic activities ('excited state'); (b) n o n - C A P (NCAP), closely related to a relatively marked stability of the biological rhythms ('stationary state'). Since C A P may be evoked during N C A P by means of subawakening stimuli, the ratio CAP time to sleep time (CAP rate) can be enhanced through a controlled perturbation. After an adaptation night to the sleep lab, 12 healthy young adults underwent randomly 2 polysomnographic recordings under: (1) basal ambient conditions (Leq < 30 dBA); (2) continuous 45 dBA white noise. Although no remarkable variations emerged in the classical sleep variables and MSLT, the acoustic perturbation induced a deterioration of subjective sleep quality correlated with a significant increase of C A P rate during total N R E M sleep ( + 120%, P < 0.0001), and during deep sleep ( + 216% in $4). Environmental perturbation, even of mild degree, may therefore induce significant micro-structural changes, which are reflected in an impairment of the restorative functions of sleep. 2. Functional EEG: cognitive functions - assessment with taskdependent EEG asymmetry with focal brain lesions. - L. Murri, E. Bonanni, R. Massetani, M. Mancino, C. Navona and 17. Denoth (Dept. of Neurology and IEI-CNR, Pisa)

E E G asymmetry in normal right-handed subjects during cognitive tasks has long been used to study the functional specialization of the two hemispheres. In this study, the asymmetry technique was used in patients with left brain lesions following acute supratentorial unilateral infarction. Twenty-six right-handed patients (14 males and 12 females, age range 62-78 years), all with right hemiplegia, were studied:

14 showed very severe receptive or global aphasia and 12 were without language disorders. EEG activity was recorded from P4-O2 and P3-O1, analysing total power and power associated with single frequency bands for 5 sec epochs. During EEG recording meaningful and non-meaningful auditory stimuli were applied (white noise, verbal and musical tasks, foreign language) and a right/left index was computed. Performance of the verbal task provoked an asymmetric reduction in power, particularly in the alpha band, in the normal subjects and non-aphasic patients with left brain lesions, indicating a prevalent left hemisphere involvement. The absence of this trend was observed in the patients with language disorders. 3. Paroxysmal EEG abnormalities genetically transmitted one family description. - R. Silvestri, R. Ciliberto, N. l_~mbardo, P. De Domenico, G. Longo, W. Cavallari and R. Di Perri (Depts. of Neurology and Pediatrics, Messina)

A 10-year-old girl came to our observation since an EEG had shown, in the absence of any clinical manifestation, generalized and symmetrical 3 c / s e c spike and wave bursts, whose duration was longer than 3 sec. The subject, the only daughter born of the first marriage of her mother, had no family history of neurological diseases; her physical and neuropsychological examinations were within normal limits. Polysomnographic recording showed, during SWS, the same abnormalities observed during wakefulness, while, during R E M sleep, EEG activity was characterized by frequent diffuse polyspike and wave complexes, prominent in the anterior leads. Also on this occasion there were no related clinical manifestations. Subsequent recordings were performed on her 33-year-old mother and 2 siblings, 3 and 2 years old respectively, born of the mother's second marriage, all normal by physical and neuropsychological examinations. A m o n g them, only the 3year-old sister showed asymptomatic left rolandic spikes. The possible genetic transmission of paroxysmal EEG abnormalities is discussed.

0013-4649/89/$03.50 © 1989 Elsevier Scientific Publishers Ireland, Ltd.

I T A L I A N EEG SOCIETY, A U T U M N M E E T I N G 4. A serial EEG study in a case of progressive rubella panencephalitis (PRP). - F. Bravaccio, A. Guizzaro, M.R. Tata, M. Trabucco and R. Cotrufo (Chair of Neurophysiopathology, Naples) A 20-year-old young m a n presented a subacute encephalopathy, with initial signs characterized by mental deterioration, and subsequently epileptic fits, diffuse progressive pyramidoextrapyramidal syndrome, myoclonus, impairment of consciousness until coma, and exitus after l l months. Although some clinical signs suggested SSPE, serum and CSF immunological findings demonstrated the diagnosis of PRP. In the advanced phase of the disease a cycle of therapy with interferon, intramuscular and intrathecal, was tried, with a mild and transient clinical improvement. Serial EEGs showed: (1) at onset the conservation of a good organization of the background activity; (2) soon after, the appearance of irregular periodic complexes with 'long periodicity' (about 14 sec), constantly synchronous with the myoclonus, and progressive deterioration of background activity; (3) presence of paroxysmal epileptogenic abnormalities (spikes and spike-waves), at first occasional, then - - while interferon was administered - - subcontinuous, with 'short periodicity' and with major expression in the frontal areas; (4) interferon, together with the clinical improvement, led to better organization of the background EEG activity. In our case of PRP we must emphasize some unusual clinical signs and the concurrence of two distinct types of periodic EEG activities. 5. Polygraphic study of night sleep in older Down's subjects. R.M. Colognola, G. Mennuni, R. Ferri, S.A. Musumeci, P. Tomassetti and P. Bergonzi (Troina, Rome and Gagliari) In this study, the authors try to correlate night sleep disruption that has been found in two groups of patients affected with Alzheimer's and Down's syndromes, these latter advanced in age. Down's and Alzheimer's syndromes present a c o m m o n anatomo-pathological finding: in fact, it is well known that amyloid plaques, of the same kind as those observed in the brains of Down's subjects advanced in age after the 4th decade of life, are present in the brains of Alzheimer's subjects; the gene alterations that have been found in these two syndromes seem to be located on identical chromosome segments. Four female institutionalized Down's subjects, with a mean age of 42.25 years, have been studied; spontaneous night sleep records were made during 3 consecutive nights and sleep patterns were calculated from the second and third nights. Comparison was made with a group of subjects with Alzheimer's syndrome, with a control group of normal subjects matched for age and with a group of children with Down's syndrome. Some conclusions seem possible: (1) in comparison with Down's children, older Down's subjects show a more severe sleep disruption; (2) in comparison with normal subjects

77P matched for age, older Down's subjects show a sleep organization impairment with an SWS increase (stages 3 and 4) and a R E M sleep decrease; (3) in comparison with subjects with Alzheimer's syndrome, these same alterations are present, but only as a trend, not always with statistical significance. 6. Neurophysiological investigations in HIV immunocompetent patients free from clinical symptumatulogy or with AIDS-related complex (ARC). Preliminary data. - F.A. De Faleo, G. Vacca, R. De Mercato, S. Natale, G. Mastroroberto, C. Crisci, B. LanzUlo and k Bianchi (Naples and Campoli M.T.) Neurological manifestations which are seen in over 30% of AIDS patients were initially thought secondary to opportunistic central nervous system infections. In 1985, HIV-specific antibodies were identified in the cerebrospinal fluid, and the virus itself was isolated from it or neural tissue of symptomatic AIDS or A R C patients. The virus can cause neurological diseases related to its localization in the nervous system even in patients not yet suffering from evident AIDS symptomatology. We used EEG and computerized spectral analysis (CSA) to study 20 HIV subjects (85% drug addicts), free from clinical neurological symptoms, to detect early instrumental changes indicating a neurological involvement secondary to HIV localization in the nervous system. Several patients were also submitted to an E M G and a conduction velocity study. Mild diffuse EEG changes and a low spectral power CSA were found in 8 patients (40%), highly significant in comparison with the age- and sex-matched control group ( P < 0.003) anti the remaining 12 HIV patients with normal EEGs ( P = 0.05). Five patients showed electrophysiological changes of the peripheral nervous system. Neurophysiological testing could be an early diagnostic tool in asymptomatic patients with HIV infection of the nervous system. 7. The use of nicergoline in cerebrovascular diseases. - N.V. Lebedeva, V.G. Vytoskaya, I.V. Musatova, I.A. Suchkova, T.A. Sharypova and V.A. Chukhrova (Moscow, U.S.S.R.) The effect of nicergoline was studied in 62 patients with disorders of the cerebral circulation. Nicergoline was injected intramuscularly or intravenously in a dose of 4 - 8 m l / d a y with subsequent oral administration. The study of platelet aggregation revealed a decrease of the parameter from 71.8% under tile influence of A D P and from 69% under the influence of adrenaline to normal values. In TIA patients administration of nicergoline in 80% of cases resulted in cessation of attacks or a significant decrease of their number. When no improvement was observed, platelet aggregation after treatment with nicergoline differed little from the initial value. No significant effect of nicergoline on regression of focal neurological symptoms in patients with acute ischaemic stroke was seen. General cerebral symptoms (state of consciousness, headache) considerably improved. There was a tendency to a lowering of arterial blood pressure. The study of the cerebral haemodynamics

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SOCIETY P R O C E E D I N G S

(rheoencephalography) failed to reveal the steal phenomenon. Nicergoline therapy caused various changes in the cerebral blood flow that could be due to a different reactivity of vascular receptors. No significant side effects were noted during treatment with nicergoline. 8. Topographic mapping of scalp electrical activity on P C / A T IBM compatible. - O. Scarpino, M. Guidi, V. Barone, E. Pistoli and F. Angeleri (lstituto delle Malattie del Sistema Nervoso, Universith di Ancona, Ancona) Topographic EEG mapping has become c o m m o n in the last 2 years, although methods and procedures have not yet been standardized. We have developed a mapping system with the following characteristics: (i) flexibility in programming that allows its use in routine and research studies; (ii) possible expansion of hardware configuration; (iii) low cost. For this purpose a P C / A T IBM compatible is equipped with an A / D converter to sample simultaneously 16-24 channels. EEG signals can be displayed on the monitor, analysed in the C P U to obtain power spectra or evoked potentials and stored on hard disk. Topographic reconstruction of the scalp potential distribution can be derived from the 10-20 electrode locations or other arbitrary arrays. Two different algorithms, k-nearest neighbours (k-NN) and surface splines, can be used to interpolate among values obtained from each recording point. The number of the nearest electrodes and the weighting coefficient can be selected as a function of the interpolation method. A 16-colour scale is used in the display, with autoranging over the m i n i m u m and m a x i m u m values; alternatively a chosen range of values can be selected as well as the size of each colour step. Each m a p is constructed by using a matrix of 2 8 0 x 2 8 8 pixels as m a x i m u m value. The system is also provided with statistical tests for computation of significance probability maps. A preliminary study was carried out to compare the different interpolation algorithms. For this purpose, simulated dipoles were used as input data. Our results demonstrate that the spline method allows more precise estimation of the field distribution. 9. Thyrotoxic encephalopathy and recurrent seizures. Primavera (Genoa)

A.

Epilepsy is a rare but possible manifestation of thyrotoxicosis. The patient reported here developed recurrent, generalized and focal, seizures as presenting symptoms of a thyrotoxic encephalopathy. EEGs performed soon after convulsive fits revealed an unusually prolonged postictal cortical depression, while interictal EEG records showed diffuse slowing, spike discharges and sometimes bilateral triphasic waves. The patient was treated with phenobarbital and clonazepam, but seizures and signs of encephalopathy disappeared only after treatment of the thyroid hyperfunction. The anticonvulsants were gradually withdrawn: 4 years later no further seizures were reported and the EEG was almost normal. We wish to emphasize that thyroid function should be evaluated in cases of otherwise unexplained encephalopathy

with seizures and triphasic waves, because epileptic fits may be the presenting symptoms of thyrotoxicosis. 10. EEG and evoked potentials (F-VEP and BAEP) during phenylalanine load in phenylketonuric patients. - A. Loizzo, F. Cardona, P. Caseioli, V. Leuzzi, S. Palazzesi, P. Valente and S. Vergari (University and lstituto Superiore di Sanith, Rome) Six early treated phenylketonuric (PKU) children underwent a standard phenylalanine (Phe) load in the 6th m o n t h of life, while on a low Phe diet. At time - 3 days, the EEG was recorded on paper and on magnetic tape, and BAEPs and F-VEPs were evaluated. During the 3 following days the children received a Phe load (180 m g / k g / d a y p.o.), and on the 4th day the same parameters were recorded. Blood samples were collected before, during and after the load. Plasma Phe and tyrosine increased consistently during the load (mean before load: 310 and 53 ffmoles/l respectively; mean of peaks during the load: 2100 and 98). In some children (2 out of the 3 analysed to date) the EEG power spectrum became more symmetrical, particularly as concerned sleep spindle power; moreover BAEPs showed reduction in inter-peak 1-V latency in 4 children out of 6, and P100 reduction in latency in 3 out of 6, while the remainder showed no variations ( 1 / 6 and 2 / 6 respectively) or increase in latency. These data indicate that such an approach may be useful to study the pathogenesis of neurochemical-neurophysiological alterations and also to give indications for the follow-up in P K U patients. 11. EEG findings in spasmophilia. - R. Lisi, P. Lisi, S. Passeri and A. Saginario (Dept. of Neurology, Fidenza) This study concerns ]46 subjects affected by spasmophilia, a disorder of calcium metabolism known as hyperventilation syndrome. All our subjects with clinical signs of spasmophilia were investigated by E M G and EEG. The EEG seems to be less important in the diagnosis of spasmophilia in comparison to EMG. In our patients the EEG was normal in 52 cases (35%) and pathological in 94 cases (65%). Bursts of theta activity at rest have been observed in 30 cases (38.4%). Bursts of focal activity have been found in 4 cases (2.7%) and bilateral paroxysms in 13 cases (8.9%). We conclude that in a high percentage of spasmophilic patients it is possible to find non-specific EEG abnormalities, especially bursts of theta activity at rest or during hyperpnoea. However, the EEG is useful in the diagnosis of spasmophilia because it permits the exclusion of an epileptic syndrome. 12. Occipital epilepsy: a non-benign infantile syndrome. - F. De Romanis and M. Feliciani (Dept. of Neurology, Rome) The EEG observation of occipital spike-wave complexes, suppressed by eye opening, is a rare finding in the infantile age. Its good prognosis is a much debated question.

I T A L I A N EEG SOCIETY, A U T U M N M E E T I N G Eleven patients (5 males, 6 females; mean age = 6.7 years) presenting an EEG pattern of occipital spike-wave complexes associated with epilepsy have been observed from the clinical and electroencephalographic points of view for a period ranging from 7 to 14 years, since the onset of the epileptic symptomatology. All patients were given anticonvulsant medication. Psychomotor retardation was present in 2 cases, who showed speech and behavioural disturbances, alexia, low scores at the WISC test. Visual p h e n o m e n a were present in 10 patients: elementary or complex visual hallucinations, amaurosis, rnetamorphopsia, which either preceded seizures or occurred as an isolated paroxysmal phenomenon. At the end of the follow-up period the ages of the patients ranged from 12 to 21 years (mean age =15.9 years). A complete remission of epilepsy was seen in only 1 case, in which the anticonvulsant treatment was discontinued after a crisis-free period of 4 years. In all other cases medication was maintained, as the epileptic crises, though less frequent, were still present. Our data do not confirm a benign prognosis of infantile occipital epilepsy and agree with the observation of Newton and Aicardi, who found in 16 affected children with a mean age of 16 years a poor response to anticonvulsant treatment in 11 cases, and learning difficulties in 10 cases. 13. The effects of short-term acetyI-L-carnitine therapy on sleep in parkinsonism. - F.M. Puca, S. Genco, L.M. Specchio, B. Brancasi, R. D'Ursi, R. Martino, V. Napoletano, A. Prudenzano and F. Scivittaro (Dept. of Neurology, Bari) Acetyl-L-carnitine (LAC) is an endogenous substance which acts as a carrrier of acetyl groups and a storage system for these. We report the results obtained comparing 2 groups of 10 parkinsonian patients, the former treated with LAC 1000 m g / day and the latter with LAC 2000 r a g / d a y for 7 days. The evaluation of the basic symptoms as well as of the clinical improvement after therapy was according to the Webster scale. Psychological and psychometric evaluations were conducted by m e a n s of various tests. Electropolygraphic records during spontaneous night sleep were obtained for each patient before and after therapy. LAC induces a decrease in akinesia rigidity and tremor, and an increase in autonomy in parkinsonian patients. Clinical improvement was clearer in those patients who showed initial symptoms of Parkinson's disease, who had never been treated before and when they were given LAC in doses of 2000 rag/day. Our results show that LAC, when intravenously administered, especially in doses of 2000 rag/day, is useful to normalize clinical symptoms in Parkinson's disease and improves the performance of psychometric tests and sleep parameters when these were impaired in basal conditions. 14. H b S A O 2 variations during sleep in Duchenne muscular dystrophy. - R. Manni, A. Ottolini, !. Cerveri, C. Bruschi, C. Zoia, G. Lanzi and A. Tartara (Depts. of Neurology, Child Neurology and Respiratory Diseases, Pavia) Patients with Duchenne muscular dystrophy ( D M D ) are considered to be at risk of developing arterial oxyhaemoglobin

79P desaturation during sleep. The magnitude of nocturnal desaturation, however, has not been fully established. We monitored night-time sleep, breathing patterns and arterial oxyhaemoglobin saturation (SAO2) according to the standard criteria in 8 consecutive D M D patients aged 10-20 years. All patients were scoliotic and chair-bound. Respiratory function tests showed a severe restrictive lung disease with reduction of vital capacity ( - 5 5 % of the normal predicted value), functional residual capacity ( - 2 6 . 6 % ) and maximal inspiratory pressure at the mouth ( - 6 5 % ) . During wakefulness, SAO 2 (98_+0.9%), arterial pO 2 (87.9_+5 m m Hg) and p C O 2 (38.9___ 1.9 m m Hg) were within the normal ranges. Mean total sleep was 363.1_+86.6 min, 18_+6.6% of which was R E M sleep. In 4 subjects HbSAO z desaturations ( 7 / n i g h t on average) were recorded, not prolonged, and were linked to the occurrence of central hypopnoeas or apnoeas, mostly during R E M sleep. Their magnitude was 7.5% on average (range 5-16%). The mean lowest SAO 2 value recorded was 88.7% (range 83-92%). Since the nocturnal HbSAO 2 desaturations observed appeared to be sporadic and mild, they are unlikely to have any prognostic and clinical significance. 15. Awake and sleep EEG features in 9 cases of Rett's syndrome. - A. Magaudda, M. Bureau, C. Dravet and B. Dalla Bernardina (Messina, Verona; and Marseilles, France) The results of an electro-clinical longitudinal study of 9 patients suffering from Rett's syndrome were reported. Mean age of the patients was 11 years 6 months. 109 standard EEG and 30 awake and sleep video-polygraphic records were analysed. The mean EEG follow-up was of 7.4 years. Slow progressive modifications of awake and sleep EEG patterns have been noted and subdivided into 3 stages: Stage 1: awake EEG was normal for the age. Rare epileptiform focal abnormalities were present at times during sleep. In this stage epileptic seizures had not yet appeared. Stage 2: a theta, medium voltage, monomorphic, non-reacting background activity characterized the awake EEG. Generalized high voltage pseudoperiodic bursts of theta activity, at 4 - 6 Hz, were present. These were not related to the peculiar periodic breathing of the g e t t syndrome. Spikes and spikes and waves were present in the awake EEG. Sleep activated epileptiform abnormalities; spindles and K complexes were rare and the different stages of sleep were difficult to differentiate. Stage 3: background activity slackened and diminished in voltage. Epileptiform abnormalities were in some cases less evident. Sleep organization destructured, with extreme poverty of sleep figures. Epilepsy appeared at the mean age of 5 years 9 months. Seizures were partial-complex. In 4 cases a transient worsening of the epilepsy was noted, characterized by the appearance of frequent absence seizures and generalized slow spikes and waves, above all during sleep. The slow evolution of the EEG is well related to the slow progression of the disease, and subdivision into the stages corresponds well with the stages of the clinical symptomatology proposed by Hagberg (1986).

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16. Turns and amplitude analysis in comparison with muscle biopsy in neuromuscular diseases. - R. Schoenhuber, P. Sorgato and A. Colombo (Dept. of Neurology, Modena) Turns and amplitude analysis (TAA) was first introduced by Willison in 1967 but it was not until 1983, with the availability of computer support, that it became more widely known. However, its use is still relatively limited and its value disputed. In the present study the results of the muscle biopsy of 26 patients with neuromuscular diseases were compared with resuits obtained by TAA and conventional electromyography of the corresponding muscles. Of 10 patients with a myopathic biopsy, 9 (90%) also had a myopathic TAA. Of 14 patients with a neurogenic biopsy, only 8 (57%) also had a neurogenic TAA. Of the 2 remaining patients with normal muscle biopsy, in one there was a normal TAA, in the other the TAA was myopathic. Conventional EMG gave only slightly, but statistically not significantly, better results in the neurogenic group. Our results, therefore, confirm the sensitivity of the TAA method and recommend, in view of the ease and speed of the analysis, a more widespread use of the technique.

17. Eiectrophysiological monitoring of a group of bromocwptine-resistant aeromegalic patients. Response to treatment with synthetic somatostatin. - V. Bonito, E. Ubiali, M. Salmoiraghi, D. Gianola and C.A. Defanti (Neurophysiological Unit and Division of Endocrinology, Bergamo) Carpal tunnel syndrome (CTS) is a common phenomenon in acromegaly. We recently studied a selected group of acromegalic patients whose plasma level of GH did not respond to the administration of bromocryptine; to evaluate the prevalence of CTS we performed an electroneurographic examination (SCV, MCV) of this population (22 patients, 13 females, 9 males, 24-77 years old). Twelve patients were treated with a synthetic analogue of somatostatin during 6 months (SMS 201-995, 50-300 #g 3 times daily, subcutaneously). An electroneurographic follow-up was performed after 6 months. Results. In 19/22 cases (86%) we found, at least unilaterally, electrophysiological signs of CTS (increase of distal motor latency, DML, a n d / o r slowing of SCV of the median nerve at wrist). In 16/22 cases (73%) there were bilateral signs of CTS. The most sensitive test was DML: we found it increased in 5 / 2 2 cases without concomitant slowing of SCV; however, in 2 patients slowing of SCV was the only abnormality. We did not find any evidence of polyneuropathy (slowing of MCV and SCV in the ulnar and tibial nerves). The response of the neurophysiological data to the treatment with SMS was related to the response of G H plasma level. In 5/12 cases this level normalized; in these cases we found a significant increase of SCV (from 39.7 to 43.8 m/sec, P < 0.05) and a decrease of DML (from 4.6 to 4.1 msec, P < 0.02). In 6 patients whose G H fell, but not to normal, we observed only a significant increase of SCV (from 35.5 to 38

SOCIETY P R O C E E D I N G S m/sec, P < 0.05). Only in 1 patient was there no response at all of G H level and the SCV and DML deteriorated. Our data demonstrate: (1) a very high prevalence (86%) of electrophysiological signs of CTS; (2) a response to the treatment with SMS roughly proportional to the reduction of GH plasma level; (3) no evidence of so-called 'acromegalic polyneuropathy'; we speculate that most of the cases described in the literature are really cases of diabetic polyneuropathy.

18. SEPs from single derrnatome stimulation of the upper limbs. - F. D'Alpa, L. Sicurella, G. Pulvirenti, A. Serofani and A. Grasso (Dept. of Neurology, Catania) Cervical and cortical SEP components from digital nerve stimulation are of smaller amplitude than mixed nerve SEPs. At least 3000-4000 responses could be averaged to resolve the smallest components. In 7 subjects we were able to recognize in all trials both P l l and P13 and, in most cases, also some P l l subcomponents. In many subjects the P13-P14 wave form was similar to that of the corresponding mixed nerve SEP. By stimulating the digital nerves of the upper limb, relative to one peripheral nerve and a single spinal segmental level, we were able to define cervical responses that clearly showed all the components already observed for the mixed nerve SEPs. By PI1 onset-P13 onset interval determination, a cervical transit time could be evaluated. Although this technique is time consuming, we have found it to be of practical value in the analysis of cervical radiculopathies.

19. Autonomic diabetic neuropathy: comparison between neurovegetative cardiovascular functionality tests and sympathetic response of the skin. - R. Dellantonio, D. Paladini, G. Sirocchi, L. Giannini, P. Fumelli, M. Badiali, G. Di Tommaso, I. Testa and A. Festa (Dept. of Neurology, University of Ancona and Hospital of Sinigallia) Ninety-two diabetics (40 women and 52 men, from 15 to 75 years, mean age 46; 50 of type I and 42 of type II L were examined using the following neurovegetative cardiovascular functionality tests: postural hypotension for sympathetic component; lying-to-standing, standing-to-lying, deep breathing and the Valsalva ratio for the parasympathetic component. We added another sympathetic test: the sweating skin response (SSR). This test was performed on 15 controls and the diabetics using Shahani's technique. It revealed no significant alterations in conduction velocity in diabetics compared to the healthy cases. The amplitude of the response at the foot level in the controls was 650 ~V+300 #V; cases were considered pathological when no response was evoked, and borderline when the response amplitude was between 0 and 350 p.V. The pathological responses to the parasympathetic functionality tests occurred earlier and more frequently than the sympathetic tests, except for the Valsalva ratio (8%). The SSR test was pathological in 28% of the cases, and the postural hypotension test in 8%. On analysing these data we noticed that the SSR was the earliest and most frequently positive of the sympathetic tests.

I T A L I A N EEG SOCIETY, A U T U M N M E E T I N G 20. Our experience in laryngeal EMG. - F. Rasi, C. Vicini, W. Neri and C. Guidi (Dept. of Neurology, Cesena and Forli) The authors show their results on selected cases examined by transcutaneous laryngeal E M G according to the technique of Blair et al. (1977). Specific attention is given to a detailed anatomical study of the region which has to be explored in order to standardize a rapid and safe technique of examining the cricothyroideus and thyroaritenoideus muscles. On the basis of these cases, the transcutaneous laryngeal E M G can supply useful information about: (a) neurogenic palsy in case of fixed vocal cord, (b) the localization of nerve lesions involving either the upper or the recurrent laryngeal nerve, at the nuclear or brain-stem level. This examination is easy and does not require endoscopic devices; therefore it m a y be carried out on outpatients without risk. 21. Associated central and peripheral demyelination: an electrophysiological study. - A. Uncini, M. Treviso, M. Basciani, M. Onofrj and D. Gambl (Dept. of Neurology, Chieti) A case is reported in which retrobulbar neuritis preceded by 4 weeks a clinically typical Guillain-Barr6 syndrome (GBS). By the onset of GBS, VEP latencies were prolonged bilaterally (R.E. = 145 msec; L.E. = 155 msec) and worsened at the nadir phase (R.E. =159; L.E. = no response). Motor conduction velocities were slow and F wave latencies prolonged. At this stage scalp components of the median and peroneal SEPs were delayed (N20 = 23 msec; P27 = 43 msec). No reliable cervical responses and cauda equina potentials could be obtained thereby not allowing calculation of the central conduction times. Eight m o n t h s later, after peripheral nervous system signs had cleared, the median SEP showed prolonged N13-N20 conduction time (7.6 msec). A normal latency cauda equina potential was now recordable but L3-scalp conduction time was strikingly prolonged (36 msec). This case emphasizes the possible occurrence of central and peripheral demyelination, probably owing to antigenic crossreactivity between the two myelins. Furthermore, in this case SEPs were shown to be a useful tool in the detection of CNS demyelinating lesions in addition to those in the optic nerves. 22. Electrophysiological evaluation of the long thoracic nerve after mastectomy. - A. Moglia, C. Zandrini, E. Dalla Toffola, S. Bergonzoli, D. Bar and A. Arrlgo (Service of Neurophysiopathology and Neurorehabilitation and Institute of Physical Therapy and Rehabilitation, Pavia) After mastectomy a deficit of the serratus anterior muscle can remain, owing to a lesion of the long thoracic nerve. In order to plan the techniques and duration of the rehabilitation therapy, E M G s of the serratus anterior and E N G of the long thoracic nerve were performed in 14 mastectomized patients. Ten patients were investigated after 1 m o n t h from mastectomy and 4 after more than I year. In the cases observed early, the

81P electrophysiological study permitted to assess the neurological deficit and to plan the appropriate therapy. The follow-up, at a distance of 1 year, showed a good correlation between clinical and electrophysiological recovery. It was not possible to obtain good clinical improvement of motility of the shoulder in the cases observed later. 23. Electrophysiological study of trigeminal-facial reflexes in cluster headache. - G. Sandrini, E. Alfonsi, L. Ruiz, G. Micieli, A. Moglia and G. Nappi (Neurologic Institute 'C. Mondino,' Headache Center, University of Pavia, Pavia) Electrically elicited blink and corneal reflexes were both investigated in patients with cluster headaches during active and remission periods. The reflex threshold and the pain threshold were examined. In all C H patients, responses with normal values of latency, duration and amplitude were obtained bilaterally for both blink and corneal reflexes. However, the corneal reflex showed a significant reduction of the pain threshold on the pain side during the active periods when compared to the pain-free side. The same results were obtained when comparing the values recorded from the pain-free side with those of the control group. Normal values were observed a m o n g the patients during the remission periods. These results suggest that a reversible dysfunction of the antinociceptive trigeminal system may be present in cluster headache. 24. Effects on axon regeneration of doxorubicin microinjected into the sciatic nerve of rats. - L. Santoro, J. England, E. Rehee, G. Caruso and A.J. Sumner (Naples, and Philadelphia, PA, U.S.A.) Replication of Schwann cells after wallerian degeneration is an important step for subsequent axon regeneration and remyelination. Thirty-four rat tibial nerves were ligated. Below the ligature 18 nerves were microinjected with 0.38 p,g of doxorubicin (a dose that has been shown to intoxicate Schwann cells selectively without significantly affecting axons or basal laminae), and 16 were microinjected with an equal volume (30 p.l) of saline solution. Within 8 - 1 0 days Schwann cells were severely depleted in the doxorubicin segments whereas active Schwann cell proliferation was evident in the control segments. Axon regeneration, as indicated by electrophysiological evidence of reinnervation of intrinsic foot muscles, was significantly ( P > 10 - 6 ) delayed along the doxorubicin injected nerve sheaths (mean rate = 1.65 ram/day_+ S.D. 0.26; mean time = 40.4 d a y s + S . D . 6.03) when compared to the control sheaths (mean rate = 2.27 r a m / d a y + S.D. 0.37 m m ; mean time = 28.7 days + 4.19). These findings provide further evidence that non-neuronal elements in the nerve microenvironment are important for axon regeneration. Proliferating Schwann cells m a y be indispensable in providing support, guidance, and trophic influences for axons, beyond that provided by the basal lamina,

82P 25. isaacs-Mertens syndrome as a late complication of acute polyneuritis. Clinical observation and electrophysiological study. - G.F. Perticoni, R. Urciuoli and T.A. Cantisani (Perugia) A 47-year-old patient was examined because of acute diffuse sensorimotor neuritis. A marked allodynia was present. R O T were normal. Laboratory investigations revealed considerable eosinophilia (28% in 11,500 leucocytes). CSF proteins were normal. E M G disclosed marked signs of denervation in all muscular areas, a moderate reduction in the voluntary interference pattern, polyphasia and fragmentation of MUAPs. Nerve conduction velocity was normal or only slightly reduced. A progressive improvement in the clinical, laboratory and E M G pictures followed. Muscular contracture and spontaneous cramps arose after 4 - 5 months, with evident diffuse fasciculations, myokymia and slow muscular decontraction. Curare and 200 mg phenytoin i.v. stopped the muscular activity, which had not benefitted greatly from anaesthetic truncal block of the nerve. The case described, which presents a picture of IsaacsMertens syndrome, helps to understand the physio-pathological processes that lie at the basis of this syndrome, in the present case clearly correlated with reinnervation. The presence of ectopic pacemakers mainly localized in nerve terminals associated with a rich, but at the same time dysfunctional, network of axons (collateral sprouting, antidromic impulse propagation, anomalous axon reflexes) would seem to lie at the basis of the muscular disturbance typical of this syndrome. 26. Automatic analysis of the spontaneous E M G activity in subjects affected by idiopathic tetany. - B. Rossi, F. Sartucci and A. Starita (Depts. of Neurology and Computer Sciences, Pisa) Idiopathic tetany (IT) represents a rather difficult syndrome to define. The only objective d a t u m is the E M G spontaneous activity, due to the increased neuromuscular excitability, recorded during the ischaemic and hyperventilation tests. We set up a method of automatic computing of this activity and by this we examined subjects with the clinical diagnosis of IT and controls, attempting to correlate symptoms and humoral parameters with electrophysiological findings. 30 subjects with tetanic syndromes have been studied: 15 normocalcaemic, 10 hypocalcaemic and 5 with a low level of intracellular red cell magnesium. The E M G activity was picked up by surface electrodes from the thenar eminence during and after ischaemia and recorded on a magnetic analog tape, then processed on a Hewlett Packard Fourier Analyzer System 5450C. The terminal output is two histograms, representing the time and a m o u n t distribution of E M G activity. By statistical analysis of distribution functions of activity (onset, duration, quantity and skewness), differences in the behaviour of both periods in each group of subjects were found and a distinction a m o n g the different classes of patients appears possible. This method of automatic analysis gives a way

SOCIETY P R O C E E D I N G S to evaluate objectively the neuromuscular hyperexcitability and distinguish different tetanic syndromes. 27. E M G evaluation of normal values of neuromuscular excitability for the diagnosis of idiopathic tetany. - M. Abbruzzese, P. Lisi, B. Jandolo, O. Ronchi, B. Rossi and M. Saginario (Dept. of Neurology, Genova, Fidenza, Rome, Florence, Pisa) Idiopathic tetany is not universally accepted as an independent morbid entity, but as a chronic hyperventilation syndrome from psychogenic causes. A contribution to the delimitation of specific abnormal neuromuscular hyperexcitability derives from EMG analysis with ischaemia and hyperventilation tests. Moreover, from analysis of the literature, differences in the quantity of spontaneous postischaemic activity (dipletsmultiplets) in controls are pointed out. In a multicentric trial we analysed 80 subjects (19-39 years), free from tetanic symptoms: the first interosseous muscle with a concentric needle electrode was analysed during a 10 min ischaemic test, 10 post-ischaemic min and during 3 min hyperventilation. Diplets-multiplets were observed in 3.7% of subjects during hyperpnoea (onset after 2 min 20 sec_+ 5 sec, duration 1 rain 15 sec+_ 30 sec) and in 31% after 2 min 40 sec_+ 1 min 30 sec from the end of ischaemia, lasting 3 min_+ 1 min 30 sec. A diagnosis of tetanic neuromuscular hyperexcitability may be suggested only when a specific E M G activity appears in basal conditions or after the ischaemic test (10 min), lasting at least 6 rain (mean_+ 2 S.D.), but especially after hyperpnoea (3 min), lasting at least 2 rain 15 sec (mean_+2 S.D.). Nevertheless, a simple measurement of E M G specific activity duration may still be insufficient to define the real existence of a tetanic syndrome, and a more objective computation of the quantity and time course of diplets-multiplets might be necessary. 28. Evaluation of N70 and PI00 variability in the pattern visual evoked potential. - G. Comi, V. Martinelli, M. Merenda, M. Filippi, M. Lacerenza and N. Canal (Dept. of Neurology, San Raffaele Hospital, Milan) The major positive wave (P100) of the VEP is usually considered the first reliable cortical response. The N70 wave is of less importance because it is often undetectable at the spatial frequencies generally used in clinical routine and because its real generator is still unknown. In this study we have evaluated the variability of the amplitude and of the latency of N70 and P100, after checkerboard and grating pattern stimulalion, both monocular and binocular. Ten normal subjects were investigated. Monocular check stimulation was performed with checks subtending fundamental spatial frequencies of 8, 6, 4, 3, 2, 1.4, 0.7, 0.35 c / d e g . Only 3 spatial frequencies (4.2, 2.7, 2.0 c / d e g ) were tested by monocular and binocular grating stimulation. The N70 presents a mean larger amplitude at higher spatial frequencies, while it is often undetectable at lower spatial frequencies. Both checkerboard and grating binocular

ITALIAN EEG SOCIETY, A U T U M N M E E T I N G stimulation induce a remarkable increase in N70 amplitude. The amplitude of P100 (measured from the baseline) is not significantly increased by binocular stimulation, nor is there an important variability with spatial frequencies below 4 c/deg. Therefore the well-known variability of P100 amplitude (peakto-peak amplitude) is mainly due to N70 variability. Our results suggest that N70 may be the first cortical postsynaptic potential, evoked predominantly by foveal stimulation, and PI00 seems to be generated by activation of both foveal and parafoveal cortical areas.

29. Low voltage bifocal stimulation of cerebral motor areas. G.F. Sau, I. Aiello, S. Traccis, R. Cacciotto, S. Patraskakis, M. Bissakou and G. Rosati (Dept of Neurology, Sassari) Currently, non-invasive cerebral motor area stimulation is performed by magnetic or high voltage bifocal electrical stimulation, techniques which require non-conventional stimulators. The present study, performed on 20 normal subjects between 18 and 60 years of age, was designed to standardize a motor cortex bifocal stimulation .method which could use low voltage conventional stimulators. The hand motor area was stimulated by surface electrodes applied at Cz (cathode) and 8 cm lateral on the bimeatal line (anode). Xylocaine 2% was infiltrated under the electrodes. The duration and intensity of the rectangular pulses were 0.15 msec and 200-250 V, respectively. The motor evoked potential (MEP) was recorded from opponens pollicis muscle by concentric needle electrodes and a slight voluntary contraction was made to facilitate the motor response. The MEP latency and the central motor conduction time were calculated for both sides. The linear regression equations of these two parameters and their normal variability between the two sides were computed.

30. Computer monitoring of the treatment of S A H cerebral vasospasm. - S. Cusumano *, D. Billeci, G. Trincia, P.L. Longatti and A. Carteri (Dept. of * Neurology and Neurosurgery, Gen. Hosp., Treviso) Thirty-two subjects affected by subarachnoid haemorrhage (SAH) have been monitored in their clinical course. Cerebral vasospasm occurred in 76.2% of the cases causing 60% of the poor outcomes while it was associated with rebleeding and hydrocephalus in the remaining 40%. SEPs (early responses) and BAEPs were bilaterally determined: concerning SEPs we measure not only the CCT but also the amplitude of the N13, N20 and P25 waves, while concerning the BAEPs we measure the I-1II and I - V interpeak latencies and the V t h / I s t amplitudes ratio. All these data were accompanied by clinical grading, Glasgow Coma Scale score, surgical timing, CT grading of bleeding, angiographic grading of vasospasm, CT quantitative evaluation of ischaemic lesions, transcranial Doppler data and the medical treatment adopted. Ventricular ratios and PIC values were also required if hydrocephalus occurred.

83P All parameters were submitted to the multiple regression test which extracted a hierarchical list of parameters highly predicting the final outcome. This test clearly showed that some of our parameters reached a good predictive level (74%), but only after the 10th day of the illness. Although Symon (1986) found that in SEPs the CCT only correlates with extreme degrees of Hunt grading, the CCT value has been rejected by our test while the amplitude values of the N20 and P25 components and the BAEPs I - V interpeak latency reached the highest coefficient levels in predicting the final outcome. Transcranial Doppler data and the gradings of CT scan ischaemic lesions and bleeding also had predictive value but at some distance after neurophysiological tests.

31. Somatosensory and motor spinal potentials: intraoperative recording. - L. Pelosi, G. Caruso and P. Balbi (Naples and Campoli M.T.) As part of a more extensive programme concerning the monitoring of spinal cord function during surgery for scoliosis through extradural recording of short latency somatosensory (SSEPs) and motor evoked potentials (MEPs), we studied conduction characteristics along the ascending and descending spinal pathways. Both SSEPs and MEPs were recorded at 4 spinal levels from cauda equina to rostral thoracic cord. Conduction velocities (CVsl of SSEPs to sural nerve stimulatton at the ankle and to tibial nerve stimulation at the knee and ankle were determined and compared. Whether the pure cutaneous or the mixed nerve was stimulated, CV along the spine was non-linear: it was significantly lower over the caudal spinal cord than over the cauda equina and mid-thoracic spinal cord segments in either case. When nerves were stimulated at the ankle, similar CV values were obtained all along the mid-thoracic cord; however, they were significantly lower than those obtained with knee stimulation. MEPs to unifocal transcranial electrical stimulation over the leg motor cortex area consisted of a triphasic potential with positive onset, and a progressively decreasing amplitude from rostral to caudal recordings. CV values along the spinal cord ranged from 59 to 68 m/sec, and this is compatible with propagation along the fast cortico-spinal tract axons.

32. Early trigeminal evoked potentials in multiple sclerosis. M. Leandri, C.I. Parudi and E. Favale (Dept. of Neurology, University of Genoa, Genoa) In multiple sclerosis 'tic douloureux' and other clinical signs of trigeminal nerve involvement may occur, usually due to a plaque at the entrance of the nerve into the pons. Recent works have shown that stimulation of the infraorbital nerve evokes a scalp response, whose first 3 components have been named W1, W2 and W3. Their respective origins have been demonstrated to be the Gasserian ganglion, the proximal portion of the trigeminal root and the presynaptic portion of the trigeminal spinal tract. In the present study these components

84P

SOCIETY P R O C E E D I N G S

have been investigated in 20 patients with a diagnosis of definite multiple sclerosis; 7 of them had clinical signs of trigeminal involvement. Limits for definition of abnormality were obtained from a population of 30 healthy volunteers; these were 1.13 and 1.83 msec for the W I - W 2 and W 1 - W 3 intervals, 0.22 and 0.18 msec for the side-to-side asymmetry of the same intervals, and 0.32 msec for the side-to-side asymmetry of W l . All the 7 patients affected by multiple sclerosis with clinical signs within the trigeminal area had the W 1 - W 3 interval prolonged on the involved side; this alteration suggests that conduction along the nerve is impaired at a site around the entrance of the trigeminal root into the pons, a result which is in good agreement with the pathological data from the literature.

spontaneous intrasubject fluctuations of the indices; the second factor F2 (2 levels) was the expression of intersubject differences as the subjects were divided into groups having a low (below median) or high mean value of the indices. TA had only an F2 effect on N1-P2 amplitude, which was larger in subjects with high mean TA. SWI had an F2 effect on N1 latency (greater in subjects with high SWI) and an F2 effect both on N1 latency (increasing from quartile 1 to 4) and N1-P2 amplitude (decreasing from quartile 1 to 4). This last effect was limited to the subjects with high mean SWI.

33. Transcranial electrical stimulation in epUepsia partialis continua. C . A . T a s s i n a r i *, R. M i c h e l u c c i *, G. Ambrosetto *, M. D e Mattei * * , R. Pantieri * * * , P. Chauvel * * * and C. Munari * * * ( * Bologna, * * Turin, • * * Paris, France)

Visual (flash: FVEP. pattern: PVEP), auditory (BAEP), and somatosensory (SEP) evoked potentials were compared in an overall group (OGE) of 100 treated epileptics (mean age 12.6, range 1.3-65 years) and in an age-matched group of 50 controls. Parameters retained for statistical analysis were: maximal amplitude of FVEPs and of PVEPs, latency and amplitude of the P100 wave of PVEPs, I - V interpeak latency (IPL) of BAEPs and, finally, maximal amplitude, total (TCT) and central (CCT) conduction times of SEPs. Five subgroups of epileptics were singled out: idiopathic generalized epilepsy (IGE), symptomatic generalized epilepsy (SGE), SGE with myoclonus (SGE-m), idiopathic partial epilepsy (IPE) and symptomatic partial epilepsy (SPE). N o significant difference between controls and O G E was found for the P100 wave. BAEP IPL was increased in O G E even though few (7%) clearly pathological values were found. Significant increases in O G E were found for all the other later components. Analysis of subgroups showed that the SGEm group had abnormal values for all parameters. Symptomatic epileptic groups showed delayed SEP conduction times compared to idiopathic epilepsies. Conversely, only the idiopathic groups showed abnormally increased amplitudes of FVEP. Thus, early evoked potentials, although not a diagnostic criterion, could be a useful contribution to differentiating symptomatic from idiopathic epilepsy, especially for symptomatic types with myoclonus.

A female patient, aged 19 years, suffered from epilepsia partialis continua, with right central cortical spikes tightly locked to myoclonic jerks of the left deltoid muscle. Repeated single electrical shocks to the motor cortex through the intact scalp, with peripheral recording from the thenar muscles, demonstrated a clear-cut electrical threshold asymmetry between the two hemispheres. The peripheral motor responses (of normal latency and analogous amplitude) were evoked by shocks of 175 V on right hemisphere stimulation and of 375 V on left hemisphere stimulation. SEEG investigations led to surgical removal of the affected area of the right motor cortex, resulting in the disappearance of seizures. To our knowledge, this is the first case of epilepsia partialis continua studied by means of transcranial electrical stimulation of the motor cortex. Two hypotheses may be considered to explain the results of our study: (1) the threshold asymmetry m a y result from a local cortical hyperexcitability; (2) the presence of repetitive focal muscle jerks m a y lead to an afferent sensory input lowering the threshold for cortical stimulation. 34. Effects of prestimulus spectral E E G patterns on the auditory cortical evoked response. - A. Romani, G. Apih, G. T a r a and V. Cosi (Pavia)

Two indices computed from the amplitude spectrum of the 1 sec prestimulus EEG have been related to latencies and amplitudes of the auditory cortical evoked response (EP) in 12 healthy subjects. The indices were: total amplitude (TA) between 1.5 and 25 Hz and relative delta + theta amplitude (slow wave index, SWI). Stimuli were 70 dB SL tone bursts delivered at 10 sec ISI. Four selective averages were obtained for each subject according to the subdivision of T A into quartiles. The same was done for SWl. The association between EEG and EP has been tested separately for TA and SWI by means of a 2-way analysis of variance. The first factor F1 (4 levels corresponding to the 4 index quartiles) represented the effect of

35. Multimodal early evoked potentials in a group of 100 epileptics. - R. Pantieri *'* *, G. Farnarier * * and C.A. Tassinari * ( * Bologna, and * * Marseilles, France)

36. Recovery cycle of the cerebral cortex in man: preliminary findings. - G.F. Rossi, M[. Palestini and R. Pallini (Rome)

A method for the study of the 'recovery' (or 'excitability') cycle of the cerebral cortex in m a n has been developed with the aim of providing a further means to explore cerebral epileptogenicity in epileptic candidates for surgical treatment. The research has been performed on 7 epileptic patients, in several sessions, during chronic stereo-EEG examination. Pairs of square monophasic pulses of 0.2 msec, 1 - 5 #A, separated by 5, 10, 20, 30, 50, 80, 100, 150, 200 and 400 msec (S1 and $2) were applied to the white matter 1-3 cm below the cortical surface. Bipolar recording of the responses (R1 and R2) was performed by using the intracortical leads of the same multi-

ITALIAN EEG SOCIETY, A U T U M N M E E T I N G electrode used for stimulation or plate electrodes on the adjacent cortical surface. The cortical responses are characterized by 3 constant components which, in basic conditions (quiet wakefulness, moderate antiepileptic pharmacotherapy), have the following peak latencies: 3-9 (component 1), 10-18 (component 2) and 28-64 (component 3) msec. The study of the 'recovery' cycle has been based on the amplitude variations of the wave 2-3, with the following results: (1) early phase of facilitation, up to S1-$2 interval of 10 msec; (2) subsequent phase of depression, between 20 and 100 msec; (3) phase of recovery, around 150 msec. These preliminary findings and the possibility of practical use of the method are discussed. 37. Age and sex effects on brain-stem auditory evoked potentials. - P. Costa, B. Bergamasco, C. Bianco, E. Bo, M. Scibelli and P. Benna (Dept. of Neurology, University of Turin, Turin) When technical and otological factors are excluded, age and sex are the most important variables which influence the brain-stem auditory evoked potentials (BAEPs). As far as sex effects are concerned, it is generally agreed that absolute latencies (LAs) and interpeak latencies (IPLs) of the compounds are shorter for females, while males show smaller amplitudes. On the contrary, age-related changes in BAEPs are still debated: some authors find an increase in LA or IPL with age, while others fail to demonstrate such an effect. We recorded BAEPs in 121 healthy subjects (53 males and 68 females) with ages ranging from 11 to 81 years; Student's t test was used for statistical analysis. Our data are in agreement with the other authors, showing differences between the two sexes; the differences in LA and IPL appear to be more noticeable than those in amplitude. Regarding age effects we found, starting from the 35th year, a marked increase of LA of the I wave and a slight increase in the V, whereas the III wave did not show any significant age-related change. These variations of LA of the I wave produce a significant decrease of IPL I - I I l in over 35-year-old subjects, while I - V and I I I - V show no significant age-related variation. 38. Multlmodal evoked potentials in amyotrophic lateral sclerosis. - A. Ghezzi, E. Mazzalovo, C. Locatelli, A. Zibetti and R. Montanini (Gallarate) Twenty-seven patients affected by amyotrophic lateral sclerosis (ALS) were submitted to recording of visual (VEPs), brain-stem auditory (BAEPs) and somatosensory (SEPs) evoked potentials to medial nerve stimulation with standard techniques (Ghezzi et al., J. Neurol. Neurosurg. Psychiat., 1986, 49: 931). They were 15 females and 12 males, mean age 53.6 years (range 36-66), mean disease duration 16.4 months (range 9-28). The following parameters were considered: VEP: N75, P100, N140 latencies, interwave latencies, P100 amplitude;

85P BAEP: waves 1, Ill, V and interpeak latencies; SEP: cervical N9, N l l , N13 and N20 latencies, N 9 - N 1 3 and N 1 3 - N 2 0 interpeak latencies. Results were compared with the standard normal values of our laboratory. VEP and BAEP results were not statistically different in ALS group with respect to the controls: no patient had responses beyond the upper normal limit at + 3 S.D. SEP NI3 and N 9 - N 1 3 were slightly delayed ( P = 0.07), N20 and N13-N20 statistically more delayed (respectively P = 0.003 and P = 0.04) in ALS patients. N 9 - N I 3 was delayed in 3 arms, N13-N20 in 8 arms. Our results confirm the finding that SEPs are abnormal in 20-30% of ALS patients, whereas VEPs and BAEPs are always v, ithin normal limits. 39. Somatosensory evoked potentials and sensory conduction velocity to physiological stimuli in man. - M, Treviso *, P. Simone *, F. Apollo * R. Castiglia *, P. Di Viesti * and P. Tonali * * (Depts. of Neurophysiopathology, * S. Giovanni, Rotondo and * * Rome) In most cases SEP and SNCV evaluation is not carried out through direct stimulation of specific receptors, but by means of transcutaneous stimulation of nerve branches. In such a case the fibres are recruited on the basis of their diameter and not of their functional meaning. Electrical stimulation has the following drawbacks: (1) lack of specificity as to activated fibres; (2) sensation of discomfort that subject can feel; (3) bypassing of peripheral receptors and more distal nerve portions which ignores changes in these structures. We describe SEPs and SNCVs obtained with mechanical stJmuli by comparing our measurements with results obtained with electrical stimuli to a distal phalanx. The SEPs and SNCVs to mechanical stimuli have similar morphologies to the electrically stimulated ones, but a lesser amplitude and a 2 msec longer latency, owing to the larger distance from stimulation point, the stimulator electromechanical delay and the activation time of peripheral receptors. 40. Automatic detection of spike and wave discharges during long-term EEG monitoring. - G.F. Testa, A. Pellegrini, L. Zanotto, R. Curro Dossi and M. Ermani (Dept. of Neurology, Padua) We describe a method for automatic recognition of spike and wave discharges, recorded in a conventional cassette for long-term EEG monitoring (Medilog 9000). A 128 K microcomputer with an A / D converter was used for digital analysis of the records in real time. Four parameters were considered to define a spike and wave discharge: (1) frequency, which was fixed at 1.5-4.5 Hz; (12) rhythm, defined as a comparable duration of at least 2 consecutive spike and wave complexes; (3) amplitude, which had to be at least twice that of the desynchronized background activity; (4) second derivative of the analysed period, which led to discard high accelerations due to rhythmic muscle artifacts.

86P The system also stored the recognized discharges, their time of occurrence and their location on the scalp, in a floppy disk for further visual evaluation. The EEG records of 20 patients with absence seizures were processed for a total time of 276 h.

SOCIETY P R O C E E D I N G S The sensitivity of the system, defined as the percentage of the total n u m b e r of spike and wave discharges recognized by two independent electroencephalographists by visual inspection, was 95% +4.5, while the percentage of false recognitions was 18%+ 15~