Society proceedings societa Italiana di elettroencefalografia e neurofisiologia

Society proceedings societa Italiana di elettroencefalografia e neurofisiologia

Electroencephalography and Clinical Neurophysiology, 1973, 35: 435-440 ©Elsevier Scientific Publishing Company, Amsterdam-Printed in The Netherlands ...

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Electroencephalography and Clinical Neurophysiology, 1973, 35: 435-440 ©Elsevier Scientific Publishing Company, Amsterdam-Printed in The Netherlands





Secretary;. D R . C. A . TASSrNARI Neurological Clinic of the University of Bologna, Bologna (Italy)

i. Cortical projections and transcommissural reactivity of neurones sampled from the thalamic relay-nucleus of the cerebello-cortical pathway ( V L ) . - - A . Bava, F. Cicirata and M. Maricchiolo (Catania).

2. The organization of eleetrocortieal activity during wakefuiness and sleep in the c a t . - - R . Amore, B. Cavazza, F. Ferriilo, B. Gasparetto, G. Rosadini and W. Sannita (Genoa).

It has already been observed that conditioning subliminal stimulation of the thalamic nucleus ventralis lateralis (VL) of the cat greatly enhances the relaying ability of the contralateral homonymous nucleus, as shown by a two-fold increase of the cortical evoked potentials obtained by stimulation of the corresponding brachium conjunctivum. On the other hand, unitary analysis has shown less than one third of VL neurones were excited by contralateral homotopic stimuli and one tenth more were inhibited. The present investigation was carried out to ascertain the reason for this seeming inconsistency by studying the nature of VL elements subjected to transcommissural influence. The experiments were performed on curarized, artificially ventilated cats (PCO 2 monitored in expired air) under chloralose anaesthesia (80 mg/kg i.p.). Routine preparation included wide section of sensory-motor cortex (I and II) ipsilateral to the VL to be stimulated. Concentric, stereotaxically oriented electrodes were used for stimulating the VL, single or repetitive shocks (l-100/sec; 0.2-0.5 msec; 6-11 V) or short trains of shocks (3-4 shocks at 320/sec; 0.1-0.2 msec; 5-10 V). An array of 9-24 switchable stainlesssteel electrodes (100 k,O resistance) delivering single or repetitive shocks (l-300/sec; 0.05-0.5 msec; 5-20 V) were thrust 1-3 mm deep into contralateral sensory-motor cortex, thus allowing excitation of the output from the contralateral VL. This nucleus was explored by tungsten wires, thinned down to 3-5/~ at their tips, between planes A9.5 and AI 1.5. Of the 183 VL neurones explored with 38 penetrations, 46.4~ proved to be sensitive to "transversal" stimuli (68 excited, 17 inhibited). Over one half (54~) of the 183 neurones reacted to cortical stimulation which fired antidromically one third of VL-VL activated units sensitive to cortical stimuli (thalamo-cortical relay cells TCR), but only one tenth of cortically drivable VL-VL inhibited units. The remainder were either undrivable by cortical stimuli or transsynaptically activated. The cortically drivable VL-VL insensitive population consisted of 20 ~ TCR cells and 80 transsynaptically activated cells. These asymmetries in TCR cell distribution might well explain the difference in effects pointed out at the beginning.

An attempt to characterize with mathematical criteria the electrocortical activity of the cat has been made by a computer analysis of the records obtained during wakefulness and sleep. Seven animals have been studied and the following parameters considered: (1) Total power of EEG spectrum, calculated on consecutive shorts segments (8 sec) and on a long sample, statistically apt to define the average aspect of the different situations. (2) Frequency and power value of dominant peaks. (3) Percentage ratio of 4 frequency bands (0--4, 4-8, 8-12 and 12 c/sec). The results obtained can be summarized as follows: (a) During wakefulness the cortical electrical activity is characterized by one peak only, centred on the low frequencies (2-3 c/see); progressively decreasing power values correspond to successive frequencies up to 25 c/see, above which any activity is exceptional. (b) During synchronized sleep the dominant peak characteristic of wakefulness is still present and enhanced in power. A second peak around 12 c/see appears in the anterior leads. The total power is also increased and no significant alterations occur in the percentage ratios of the considered bands. (c) Results strictly similar to those seen in the waking state have been obtained in the REM phase of sleep. In all the considered conditions the EEG organization is different in the various structures simultaneously explored and in the time yariable for each structure. Peculiar rhythmically organized activities do not seem characteristic of the "msidered functions, and alterations, mostly quantitative of the whole spectrum, accompany the transition from one to the other. The 12 c/see peak occurring in synchronized sleep indicates that a second generator is operating in this situation only. 3. Postsynaptic responses of buibo-pontine and mesencephalic reticular neurones induced by stimulation of limbic structures.- M. Margneili, A. Grantyn, R. M. Grantyn and M. Mancia (Leipzig, D.D.R., and Milan ). In enc~phale isol~ cats, cerebellectomized, curarized and artificially ventilated, an intraeeUular study has been under-

436 taken to clarify the postsynaplic response~ of hulho-pontinc (BP) and mesencephalic (MES} reticular netmmcs to ~timulation of hippocampus, entorhimd cortex, scptum, lateral hypothalamus, medial forebrain bundle (MFB) and reticulo-spinal tract (RST). Both BP and MES reticular neurones were found to be prevalently of excitatory type: hippocampus was effective in 43'~', of BP and in 68"/o of MES, entorhinal cortex in 555';, PB and in 61".i; MES, septum in 59 ~,,, BP and 78 'YooMES, lateral hypothalamus and MFB in 76',, BP and in 810/,~ MES neurones. The postsynaptic responses of BP neurones were mainly of "'phasic'" type with short lasting and quick rising phase EPSPs while MES neurones responded with long lasting EPSPs and prolonged discharges outlasting the stimulus, characteristics of a "tonic" type response. The latencies of responses were longer for MES (18.3 msec) as compared to BP (7.8 msec). On the basis of previous findings (A. Grantyn 1971) our results suggest the presence of a limbic brain-stem feed-back circuit essentially positive in character. The excitato: y influences on BP and MES reticular neurones with different electrophysiological features suggest that the limbic system may have a functional role influencing the brain-stem mechanism of arousal and sleep (synchronous and desynchronized). 4. lntracellular study of intralaminar thalamic neurones during mesencephalic reticular stimulation.--M. Maneia and J. Otero-Costas (Milan).

In enc~phale isol~ curarized cats intracellular recording from intralaminar thalamic neurones during high frequency mesencephalic reticular stimulation has revealed an inhibitory effect on spontaneous discharges with or without increase of membrane potential (of the order of 5 8 mV). The injection of a hyperpolarizing current induced reduction or complete blockade of firing together with increase of membrane potential. Mesencephalic stimulation performed during the anodal pulse did not change or slightly increased the amplitude of the pulse, indicating that the inhibitory mesencephalic effect was not due to IPSPs. Similar effects were found in cats with chronic spinal hemisection or chronic hemicerebellectomy The results suggest that the mesencephalic reticular inhibition on intralaminar thalamic neurones is due to removal of a background tonic facilitatory impingement on thalamic neurones,, i.e., to "disfacilitation". 5. A statistical comparison of the temporal pattern of focal interictal dischange induced in cats by three epileptogenic drugs.--F. Angeleri, S. Giaquinto, G. F, Marchesi, C. !. Cianchetti and V. Gallai (Perugia). Under light pentobarbital anaesthesia, epileptic foci were induced in the parietal associative area in 16 cats, using topical application of penicillin powder, strychnine sulphate {I '~/,,) and premarin (1 'Yo). Following the application of each drug, focal electrical activity was continuously recorded on paper and on magnetic tape until induced spikes were no longer seen. In the case of penicillin, however, only the period preceding the first seizure was studied, in order that the data related to this drug might be comparable to those obtained using strychnine and premarin. Two parameters were

SOCIETY PROCEEDINGS rneasured, using an IBM computer: (i) number of spikes during each 10 sec period, and (ii) duration of each interspike interval. Analysis of the data was made by the following statistical tests: serial array, frequency distribution, joint test, run test, 90th order correlogram. The statistical analysis showed that each of the three tested drugs produces a characteristic pattern of activity, significantly different from that produced by the other two agents. 6. Bilateral synchrony of epileptic discharge originating from chronic asymmetrical cortical foci. - - R. Mutani, L. Bergamini, R. Farieilo and G. Quattrocolo (Turin). Two asymmetrical foci were induced by intracortical injection of cobalt-alumina in the cat. After an initial period of asynchronous epileptic activity, a steady EEG pattern of time-locked discharges was seen until the cat was killed (2 4 months after surgery). In most cats bilaterally synchronous and symmetrical spike and wave or polyspike and wave discharges occurred, accompanied by massive myoclonic jerks. The degree of interhemispheric synchrony was 50100 msec. Splitting the corpus callosum disrupted bilateral synchrony which, however, was not affected by bilateral cortical-callosal isolation. This suggests that the callosal commissural pathways were essential for the maintenance of the functional interaction between the chronic asymmetrical loci responsible for the bilateral synchrony of the epileptic discharge. The role of the cortico-subcortical pathways and subcortical structures was not essential, Modifications of EMG activity in cat intestine during generalized and focal epileptic seizures. - - J. Gonella, E. Cherubini, D. Mancia and C. A. Tassinari (Marseilles, France, Parma and Rome ). Experiments have been carried out on 38 cats anaesthetized ~¢ith Fluothane and immobilized with Flaxedil. Simultaneous recordings have been made of the EEG, arterial pressure, ISCG and intestinal EMG, using a suction electrode. The a iln of this work was to study the changes of intestinal activity during various types of attack provoked with Cardiazol and electrical stimulation of the nuclei in the amygdala and the cortex. The nature of the modifications of intestinal contraction depend on the type of attack. In generalized attacks, however provoked, there is an increase in arterial pressure and abolition of the contractions in the post-ictal phase because of the inlerplay of sympathetic inteslineinhibitory and adrenaline secreting efferents. In local seizures induced by electrical stimulation of the amygdala, intestinal contractions appear or increase at the beginning of the after-discharge and sometimes also after the end of the after-discharge. This effect is abolished by section of the two vagi. In focal seizures induced by electrical stimulation of various zones of the cortex there is an appearance or increase of intestinal contractions at the time of the seizure onset. These effects are also abolished by section of the two rag1. In conclusion the results indicate that at least two types of epileptic seizure exist, different at the level of the vegetative manifestations they induce. (1) A generalized seizure that, however produced, activates massive sympathetic activity

ITALIAN EEG SOCIETY with parallel effects (inhibition of the intestinal mobility, hypertension etc.). (2) Focal seizure that induces mechanisms of parasympathetic type with effects prevelantly of intestinal excitation. 8. Morphoiog~ and temporal relationships of human epileptic potentials during physiological sleep. - - B. Cavazza, G. Rosadini and A. Siccardi (Genoa). Interactions between epilepsy and sleep have been studied by a computer technique designed to define the average morphology of epileptic spikes and to establish the temporal relationship between epileptic potentials simultaneously recorded from different leads. The EEG scalp records of 10 patients during wakefulness and different EEG phases of physiological sleep have been analysed with the following results: (1) There are epileptic prototypes represented with the same morphological characteristics in the waking state and in all sleep phases. There are, on the contrary, some other prototypes limited to a few conditions. As a consequence, sleep seems to interfere with the generation of the epileptic potential by modifying the discharge pattern of certain neuronal populations. (2) The time intervals between epileptic potentials simultaneously recorded from different leads may increase as well as decrease; the direction and the amount of such alteration may vary not only from subject to subject but also in the same subject. Sleep may interfere with transmission mechanisms of epileptic potentials. 9. The action of light on the facial spasm experimentally induced in photosensitive baboons.--E. Cherubini, E. Carlier and R. Naquet (Marseilles, France, and Rome). In 4 baboons (Papio papio) which were photosensitive to a greater or lesser degree, bilateral section of the facial nerve produced after about 2 months the appearance of a syndrome which resembled the post-paralytic facial spasm known in man. This spasm, which was clinically manifested by clonic jerks of the facial muscles, sometimes associated with eyeblinks, was elicited by various sensory stimuli, such as flashes of light, clicks and tapping of the forehead. The clonic jerks followed flashes at up to 5/see and were not accompanied by EEG changes. No responses were obtained to flashes at higher frequencies. When flash rates of 25/sec were used the clonic jerks reappeared, but on these occasions were accompanied by fronto-rolandic epileptic activity in the EEG. 10. Differential effects of cutaneous myelinated afferents on spinal reflexes in the decerebrate cat.--N. C. Accornero, G. L. Lenzi and M. Manfredi (Rome). The monosynaptic reflexes of extensor (gastrocnemius) and flexor (peroneus, PBST) muscles were recorded from ventral roots of decerebrate cats at different intervals (from 5 up to 1000 msec) after a conditioning stimulus of the sural nerve. Differential blockade of myelinated afferents and continuous monitoring of sural nerve afferent discharge allowed selective activation of beta, beta plus delta and only delta fibres of the cutaneous nerve. Extensor reflexes constantly

437 showed a powerful initial inhibition lasting 20 msec for the pure delta volley, followed by facilitation lasting 50 msec. Flexor reflexes were generally facilitated. A transient inhibitory phase coinciding with the peak of the ventral root discharge evoked by the sural volley was probably related to occlusive phenomena at the level oftbe flexor motoneurones. The recovery curves after pure beta as well as delta conditioning were similar, the main difference consisting of a delayed effect of the delta volley related to the slower conduction velocity of these fibres in the peripheral nerve. The combined action of beta plus delta conditioning simply showed a summation of effects between the two sets of fibres. 11. Postsynaptic responses induced in bulhe-pontine and mesencephalic reticular neurones by intralaminar thalamic and medial forehrain bundle stimulation. - - M. Margnelli, R. Spreafico, M. Mariotti and M. Mancia (Milan). In enc~phale isol~ curarized cats, low and high frequency stimulation of intralaminar thalamic nuclei (Mth) induced EPSPs in bulbo-pontine (BP) neurones with various latencies and with increased firing rate. EPSPs of shorter latencies and with stronger synaptic links were also induced in the same BP neurones by low and high frequency stimulation of the medial forebrain bundle (MFB). Mth stimulation induced EPSPs of short latency in MES neurones. MES neurones were often antidromically activated by Mth stimulation. The latter neurones responded also to low and high frequency MFB stimulation with EPSPs with or without spikes of short latency and strong synaptic linkage. Similar effects were observed in BP and MES neurones after acute bilateral fronto-parietal decortication. The results indicate that on the same BP and MES neurones there is a convergence from the Mth and MFB. This result, together with the synaptic influences of MFB on the MES neurones antidromically activated by Mth, suggests the participation of a large percentage of brain-stem neurones in a more complex feed-back circuit whose input comes through the MFB from the limbic system. 12. Recovery curves of the H reflex in normal man after cutaneous stimulation of toes and their modification by voluntary contraction of foot extensor and flexor muscle~ - - E. Pierrot-Deseiiligny, B. Bussei, G. Sideri, H. P. Cathala and P. Castaigne (Paris, France, and Rome ). The effect of cutaneous stimulation of the 5th and 1st toe on the amplitude of the soleus H reflex has been studied in 12 normal volunteers. The recovery curves have been investigated at rest and during voluntary contraction of gastrocnemius and tibialis anterior of both sides. (1) The cutaneous stimulus delivered during muscular relaxation was followed by an inhibition of the ipsilateral H reflex, lasting from 50 to 70 msec, which was more evident after 5th toe stimulation. The contralateral reflex was instead facilitated after cutaneous stimulation. (2) During voluntary contraction of agonist or antagonist of both sides the inhibitory phase following 5th toe stimulation was significantly reduced; the effects of gastrocnemius and tibialis anterior contraction were similar. Voluntary contraction did not alter the recovery curves after

43N 1st toe stimulation. (3) These results could be explained by a differential effect of the pyramidal tract on the interneuronal chains activated by the cutaneous afferents. 13. The recovery cycle of blink reflexes and sensory discrimination of stimuli in man. - - C. Messina (Messina).

The present study contributes to a better understanding of both the functional organization of blink reflexes and the inhibitory mechanisms underlying habituation. The recovery cycle of blink reflexes has been tested by a double stimulus technique in 15 adult healthy subjects. The test stimulus was applied to the supraorbital nerve, The conditioning stimulus was applied to the same nerve, the contralateral supraorbital nerve, the ipsilateral infraorbital, medial or ulnar nerve. Sensations evoked by the stimuli were also recorded. When conditioning and test stimuli were applied to the same supraorbital nerve, the early response did not show any inhibitory phenomenon. In contrast, the late response was completely inhibited for 280 msec followed by a period of partial inhibition; it was not noticed by the subjects. These findings suggest that the site of inhibition is the ascending tract of the polysynaptic chain. Presynaptic inhibition at the level of the trigeminal afferent is ruled out because of the complete inhibition still observed when the conditioning stimulus is applied to the different nerves. During partial inhibition the perception of stimuli is not altered. This suggests that, at this time, the site of inhibition is in the descending tract of the polysynaptic chain. Since this partial inhibition is still present 2-3 sec after applying the stimulus, it can be surmised that it is responsible for habituation as it ,:an be induced by trains of stimuli at 0.2 - 0.4/see. 14. Responses evoked by vestibular stimulation recorded from the scalp in man. - - S. Mingrino and G. A. Molinari (Padua).

Galvanic stimulation of constant voltage, 10 msec duration, and from 1 to 6 mA intensity is applied to the auricular region. The responses are recorded from electrodes placed at the vertex and at the occipital region. The evoked response has a delay of 60-80 msec and consists of one or more series of biphasic waves with an amplitude from a few to 15 #V. The strict correlation of the response to the vestibular stimulation is demonstrated by the following facts: (1) The response is evoked only when vestibular function is preserved; in fact it is recorded in anacusic patients but is absent in vestibular areflexia. (2) The response persists after curarization. The evoked potential probably represents a vestibular non-specific response. 15. The "expectancy wave" (CNV) in normal children. - - M. Papini and R. Zappoli (Florence).

The characteristics o f the CNV in children of different ages have not yet been sufficiently identified. In the present study some of the features of the CNV have been investigated in 15 normal children ranging from 5.5 to 8 years. In all subjects examined, very ample CNVs (at times as much as 50 #V) were observed over the frontal areas and at the vertex, independent of the children's age, with a mean amplitude

SOCIETY PROCEEDINGS of 23 itV at the vertex. The w)ltages almost always appeared lower over the posterior areas. In the children from 5.5 to 7 years the CNV mostly showed a tent-like shape (slow ascending limb and descending limb with a general absence of plateau), while with the 8-year-olds the shape was like a boot (fairly rapid ascending limb, presence of a brief plateau. descending limb still fairly slow). Reaction times to $2, more especially in the younger children, were always long m comparison with normal adult subjects. Inconstancy and variability of the C N V , the presence of too many artefacts owing to restlessness of the subjects, were largely corrected by the projection of a slide following the operant response according to our previously described technique, with greater homogeneity of the CNV in the controls. 16. Electro-clinical study of a mesencephalic syndrome due to a bullet: neurnanatomical considerations. - - A. Bricolo, G. Turella and A. Bazzan (Verona).

This paper reports the main findings of a longitudinal clinical, electroencephalographic and radiological study in a child of 8 with a cranio-cerebral wound due to an air-gun bullet which penetrated the left temporal region and stopped against the right parietal bone, Prolonged rigidity due to decerebration, deep coma, transitory hemiballismus and a remarkable dyskinetic syndrome were the predominant symptoms of the first weeks. The EEG patterns resembled those of cerveau isol~. T h e activity at 11 12 c/see anteriorly, clustered in bursts lasting 3-4 sec. was unaffected by stimuli. in contrast to the sleep spindles recorded in the same patient during recovery. This raises some neurophysiological hypotheses: (I) The lessening of the desynchronizing influences from the impaired rostro-mesencephalic reticular formation induces, at cortical level, slowing of the spindling of thalamic origin. (2) The thalamic generator, freed from influence of the activating reticular formation, produces spindles of greater duration and slower in frequency. (3) The cortex, suffering in toto, because of metabolic impairment, is not able to achieve the frequencies at which it is physiologically driven from the thalamic generator. After a year this child, who was at first in deep coma. made a good recovery showing only dyskinesia. The neurological, radiographic and electroencephalographic findings are discussed in relation to the anatomy of the subthalamus and rostral brain-stem 17. The effects of a new benzodiazepine (Bromazepam) on the nocturnal sleep of subjects affected by compulsive-obsessive neurosis. - - R. Di Perri and M. Meduri (Messina).

Eight subjects affected by compulsive-obsessive neurosis have been treated with RO 5/3350, a new compound of the benzodiazepine series. The drug was given orally in doses of 24 mg per day. The effects of this drug on the EEG during wakefulness and during nocturnal sleep were observed by means of serial polygraphic controls taken for 3 consecutive nights before the onset of therapy and repeated 1 week and 2 weeks after therapy. Before therapy all subjects showed a normal EEG during wakefulness and during sleep there was a normal percentage of sleep time with the presence of all

ITALIAN EEG SOCIETY sleep stages, a good REM-NREM ratio and a normal number of sleep cycles. After therapy, no clear differences were observed in the waking EEG. An increase in stage I and II and a decrease in stage IV sleep were seen, while no statistically valid changes in the total sleep time, the REM stage and stage III were noted. The results are discussed and compared to similar findings obtained by other authors with the use of different benzodiazepines. The meaning of stage IV sleep is also discussed in relation to its decrease observed in a great variety of clinical syndromes. 18. A polygraphic analysis of nocturnal sleep in enuretic children. - - D. Gambi, F. Pinto and F. Vacchini (Rome).

29 polygraphic records of night sleep in 8 childeren with idiopathic enuresis have been made. These records (4 consecutive nights in 5 children and 3 nights in 3 cases) have been carried out with methods previously described by Gastaut and Broughton and were part of an interdisciplinary research program investigating psychodynamic problems of the personal and family history of children examined. The results can be summarized as follows: (1) Enuresis is a nocturnal non-epileptic event which appears in every sleep stage but more frequently in stages 2, 3 and 4, not always with coexisting transitory awakening. (2) In the same case nights with enuretic episodes show: (a) deep sleep stages and REM sleep more regularly scattered in cyclic organization; (b) REM stages appearing early in the night; (c) smaller amount of wakefulness and stage I; (d) larger amount of REM stage. All these findings seem to indicate that enuresis is an event able to determine a more harmonic organization of night sleep and facilitation of REM sleep. The relationship with REM stage recalls psychodynamic theories on enuresis. 19. EEG changes and facilitation of hysterical attacks during antiepileptic therapy. - - P. Rovetta (Bustu Arsizio).

The case of a woman with hysterical attacks in whom antiepileptic therapy was administered in error is described. The sodium dilantin and phenobarbital enhanced the number of hysterical attacks. At the same time there was slowing of the basic rhythm of the EEG together with transient high amplitude slow potentials. Primidone was administered after some weeks, without results. High doses of intravenous and oral diazepam induced fast rhythms in the EEG, but the frequency of the hysterical attacks was unaffected. After discontinuation of all drugs there was total remission of clinical events. At the same time there was a decrease in the slow transients of the EEG. The improvement was observed in a follow-up of 2.5 years. 20. Treatment of different kinds of infantile epilepsy by synthetic A C T H (Synacthen Depot®). - - F. Brambiila, M. Ginrdini and C. Lenti (Milan).

The authors illustrate the results obtained by the therapeutic use of synthetic ACTH in about 60 children suffering from different kinds of epilepsy, especially West syndrome and Lennox Gastaut syndrome, as well as cases of focal and

439 psychomotor epilepsy. In most cases the treatment lasted a long time, from a minimum of 3 months to a maximum of 2 years (therapy is still continuing in 3 children). Decreasing dosages have been used, down to 0.10 mg, and intervals between injections reached 6 days. The main humoral and clinical parameters have been controlled periodically, and in 22 cases periodic checks of urinary corticosteroids were done before and after administering the drug. The results allowed adjustment of the treatment, especially in relation to intervals between one administration and the next not exeeding 4--6 days. The drug proved effective particularly in West syndrome, secondly in psychomotor epilepsy and thirdly in Lennox-Gastaut syndrome. Also, in all children, the urinary 17-OH-corticoids before the administration of Synacthen Depot were found to be very low, and the effect of the drug on the adrenals, also found after treatment, lasted many years (possibly related to hypothalamic or diencephalic dysfunction). 21. Slow wave sleep deprivation in epileptics. - - P. Bergonzi, C. Chiurnlla and C. Cianchetti (Perugia).

Five patients with generalized epilepsy underwent selective deprivation during the fourth sleep stage. Two basic nocturnal records were taken in each patient, two with deprivation of stage IV and two during recovery. In each of these records the percentages of wakefulness and sleep stages were calculated, as well as the epileptic spikes per minute and the average duration of sleep cycles. The following observations were made: (1) slow sleep lost during the fourth stage must be recovered; (2) a REM stage rebound is observed during the nights when the patients are recovering from the lost fourth stage; (3) during the two recovery nights, a relative fourth stage rebound prevails in the first, whereas in the second a REM stage rebound can be observed; (4) during the nights of fourth stage deprivation the sleep shifts towards both the other slow stages (I and III) as well as the REM stage: [5) recovery of the fourth sleep stage replaces the second and third stages. It was noted that epileptic activity remained constant in all groups of nocturnal records, both before and after fourth stage deprivation, which leads us to believe that the desynchronized sleep stage is responsible for the activation of epileptic spikes after total deprivation of sleep. The sleep cycles were different during the control nights from the recovery nights; in the first case there was a tendency for the cycles to decrease in duration, starting with the first cycle and gradually proceeding to the following ones; in the second case, the opposite was observed. This may depend either on a greater persistence of slow sleep, even during the latter hours of the night, or on a longer duration of the REM stages. 22. Some remarks on 100 cases of Lennox syndrome. - - L. Cappella, G. Gatti and G. B. Cavazzuti (Modena).

A longitudinal study has been carried out on 100 patients, with particular reference to the onset and long term evolution of Lennox syndrome. 26 cases were regarded as idiopathic with normal neuropsychiatric development before the onset of the syndrome and 74 patients had secondary forms (13 cases with cerebral neonatal injury, 22 cases had suffered

44~) severe acute encephalopathies, 2 cases of tuberous sclerosis, 1 case of congenital toxoplasmosis, 20 cases had West syndrome and in 16 cases there was an unidentified cerebral pathology). The idiopathic forms began at different ages between 5 months and 10 years of age, but were mostly seen between 1 and 4 years; the secondary forms began between 6 months and 8 years of age but in general occurred between 2 and 3 years. The forms following West syndrome usually occurred after an interval of 1-6 months (this interval was generally related to ACTH therapy); the forms following severe encephalopathies (meningitis, encephalitis, HH syndrome) occured either during the encephalopathic illness or, more often, after an interval of 3--5 months. In more than half of our cases we also observed a pre-Lennox syndrome which was characterized by an incomplete symptomatology without slow spikes and waves and typical seizures, The syndrome became complete in a period of 6-12 months, but took longer if therapy had already been initiated. 27 patients were observed for a period varying between 7 and 17 years; 17 of them still suffer from the typical syndrome, in 7 the seizures have disappeared but EEG abnormalities and psychiatric problems are still present, and in the other 3 patients there has been good mental development although focal epileptic seizures occur. Therapy with ACTH, benzodiazepines and DPA had a different effect on some cases. 3 of the patients, who were idiopathic and had been treated early, became normal. 23. Contribution of electro-physiological techniques in the control of prolonged post-traumatic comas. - - D. Mancia, R. Vigouroux and R. Naqnet (Parma and Marseilles, France ). One hundred cases of prolonged coma had EEG studies immediately after the trauma, in the subsequent days and often for several years afterwards. The contribution of the EEG to the prognosis of life or death is compared with the evaluation of a functional prognosis, not only during the first few days after the trauma, but also on the twenty-first day and in the following years. Even though important data m relation to a life or death prognosis are obtained from the I~EG, the data for evaluation of a functional prognosis are, with few exceptions, deceptive. We have tried in some cases to see if recording of the circadian rhythm and visual potentials could give some information about residual cerebral damage. However, the information provided by these techniques considered separately is, with few exceptions, useless, probably because these methods are not yet fully developed. In spite of these findings, it is considered that all these three parameters (routine EEG, circadian cycle and visual potentials) often provide useful data in the period during which the clinical study of the patient is still difficult. 24. Reconstruction of compound action potential of oculomotor nerve of the cat (with a comparison between geometrical and arithmetical methods). - - N. Dagnino, M, Manfredi and G. Sideri (Genoa-Sestri and Rome). The fibre size distribution of peripheral nerves and central tracts has .been widely investigated and their compound action potentials successfully reconstructed. Similar data

SOCIETY PROCEEDINGS are still lacking for cranial nerves. During an investigation on the excitability of the motor neurones of the lllrd nucleus o1 the cat during sleep, we attempted to reconstruct the compound action potential of the oculomotor nerve and to identify the neuronal population responsible for the summated nerve potential evoked by stimulation o f its nucleus. Compound action potentials of the oculomotor nerve have been recorded in awake animals and enc~phale isolk cats: in addition, a monophasic "killed end" record was obtained in a nerve chamber after dissection of the intracranial tract of the nerve. The external diameter of the axons of this nerve (9,253 fibres, representing all fibre spectra) was measured on photographs of an osmic stained section magnified 1000 times, and plotted on a histogram. The reconstruction of the action potential was performed with the classical geometrical method of Gasser and Erlanger (1926) and with the recent arithmetical method of Landau, Clare and Bishop (1968). The results have been satisfactory in both cases, but the arithmetical method proved on the whole more adequate and practical since the complex geometry of the classical procedure is avoided. It was concluded that the compound action potential o f the Illrd nerve represents the activity of the oculomotor alpha motor neurones. 25. Focal spikes induced by blinking. - - C. A. Tassinari, B. Dalla Bernardina, G. Ambrosetto, M. R. PeraitaAdrados, L. Robaglia and J. Roger (Bologna and Marseilles, France). It is known that closing or opening of the eyes. looking at patterns can facilitate the appearance of epileptic discharges or seizures. Similarly, adequate proprioceptive stimulalion (tendon percussion, cutaneous stimulation) can provoke epileptic seizures or evoked potentials which can be recorded from the scalp. A case showing a phenomenon not previously described in the literature is presented. In this subject high voltage spikes, predominantly in the central regions, were provoked by blinking. The latency between the b[ink, recorded electromyographically from the orbicularis oculi, and the spikes was 50 reset, This phenomenon was not influenced by the presence or absence of light. The subiecl was a 12-year-old boy with severe amblyopia, a visual acuity of l~10, nystagmus and a marked optic atrophy. He suffered from severe anoxia with convulsions at birth, and subsequently developped an hypsarhythmic syndrome followed by "Petit Mal Variant'" (Lennox-Gastaut syndrome t. 26. Contribution to the EEG study of cerebral tumours in infancy. - - E. Scanabissi and G. Neri (Bologna). An electro-clinical examination has been carried out on 27 children with cerebral tumours, 16 of which were of the infratentorial type and 11 of the supratentorial type. After describing the clinical features of the two groups of patients, the authors underline the high incidence of EEG changes. In the patients with infratentorial tumours, posterior delta activity and bursts of slow frequency were the most frequent EEG abnormality. Abnormalities of a slow type, diffuse or local, were prevalant in supratentorial tumours. The bioelectric abnormalities of greatest diagnostic value were observed in a case of hemispheral tumour.