Phenomenology of simple partial seizures

Phenomenology of simple partial seizures

Seizure 1996; 5: 283-289 Phenomenology of simple partial seizures R. ERKWOH & E.M. STEINMEYER Clinic of Psychiatry and Psychoterapy, RWTH Aach...

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Seizure 1996; 5: 283-289

Phenomenology

of simple

partial

seizures

R. ERKWOH & E.M. STEINMEYER Clinic

of Psychiatry

and Psychoterapy,

RWTH Aachen,

Germany

Based on a sampleof 325 inpatients we present the subjective experiencesduring simple partial seizures. In a majority of cases,auras comprisedcomposedforms of different symptomatic qualities. We describerules which seem to govern sequenciesof aura phenomena. Autonomous and vestibular sensationswere shown to have preceding positions related to others, olfactory and gustatory sensationspreferred a following position. The tentative explanation of the findings favours the idea of heterogeneity rather than the concept of a focal discharge in a simplepartial seizures.

INTRODUCTION According to Hughlings

Jackson’, the onset of the epileptic aura indicates the focus of the discharge, and the succession of aura symptoms demonstrates the pathway of the propagation of discharges. “What we call the warning, this being the first event from, or during, the onset of the local, sudden, rapid, and excessive (or briefly the ‘epileptic’) discharge, is the clue to the seat of the ‘discharging lesion’.” Epileptic seizure auras are characterized as simple partial seizures mostly preceding a complex partial seizure*. The fundamental division into partial and generalized is based mainly on whether or not consciousness (responsiveness) is impaired in the attack. In a simple partial seizure, consciousness is retained. The word ‘partial’ is deliberately chosen to avoid the implication that a discrete focus exists, even if for this seizure type clinical or EEG changes suggest a focal onset. Nevertheless, Palmini and Gloo? stated recently that the type of aura, when elicited by careful history-taking, provides localizing information as useful as given by EEG and modern hightechnology procedures such as CT, MRI, and PET. If this is accurate, a phenomenological analysis of aura symptoms and symptom sequencing should warrant a rebirth of the ‘via regia’ denoted by Hughlings Jackson. However, some auras may unfold a complexity of phenomena. The problem addressed by our study is: if auras consist of a phenomenal polymorphism there would be a marked decrement of their localizing value. But testing them for certain 1059-131

l/96/040283

+ 07

$12.0010

orders or rules of co-occurrences may re-establish hints to possible foci. So we have two hypotheses to test: (1) even monosymptomatic simple partial seizures are not unambiguous in origin; (2) even if any rule in co-occurrences of elements is detected, it will not be clear to interpret. MATERIALS

AND METHODS

The files of 1563 epileptic inpatients (912 females, 651 males) of the Nervous Disease Center of the University of Bonn (including Epileptologic, Neurologic and Psychiatric clinics) between 1968 and 1983 were examined. During this period archives of all files have been structured in an equal manner. Three hundred and twenty-five patients exhibited auras in isolation or preceding complex partial seizures. Diagnoses of epilepsy had been confirmed clinically and by EEG. Twenty-seven per cent of the patients with auras showed the complex partial (psychomotor) type of seizures, 24% generalized tonic-clonic seizures (Grand Mal), 4.5% other focal seizures and 29.5% showed a mixed type of complex partial and generalized seizures. Primary data collection was based on documentations of seizure events generated by observing doctors of the wards, most of them in the employ of the Epileptologic clinic. Precise and detailed reports of all patients were guaranteed by high educational standards of all coworkers due to mutual exchange between the three branches. The mode of data collection was retrospective. We evaluated all the notes taken by medical staff at the time of post-hoc 0

1996

British

Epilepsy

Association

FL Erkwoh

284

interviews as well as all objectively documented peri/postictal incidents at the time of hospitalization. For simplification, each symptom included in a simple partial seizure was documented once, even if several identical seizures were reported by the medical file. Ten per cent of the patients revealed different types of simple partial seizures. Repeated identical symptoms again were recorded as occuring once. Because data collection started in 1984, none of the date collectors were privy to the goal of the study. The descriptions of the aura symptoms and the sequencing were not obtained from a checklist. By using the patient’s own words to describe the various symptoms experienced during a seizure (written down at the time by medical staff), we were able to preserve objectivity.

STATISTICS

A considerable amount of time elapsed before adequate statistic methods (E.M.St.) were available for the large data set. Most of the data has ordinal level. Since it cannot be expected that interval-scaled variables will have unimodal, symmetric distributions with homogeneous variances, nonparametric test procedures were preferred. We applied: nominal data: exact tests in 2 X k contingency tables (Fisher). Frequency/ contingency tables with ordered rows/columns: exact test (Jonckheere-Terpstra [In: StatXac. Statistical Software for exact non-parametric Inference. Cytel Software Corporation, Cambridge. For more details see: Hollander and Wolfe4. Level of significance for all tests was 2a = 0.05. To compare r populations that generate either continuous or ordinal categorical data, we used the Jonckheere-Terpstra test (similar to the Kruskall-Wallis test); this is a generalized version of the Wilcoxon rank-sum test applicable to more than two populations. This test is more effective than the Kruskall-Wallis test if the r populations have a natural ordering, i.e. if they are defined by the different levels of a quantitative variable. It is important to note that the hypothesis tested by the Jonckheere-Terpstra test is that the r rows (not the c columns) of the r X c contingency table come from the same underlying distribution. Pairwise co-occurrences of aura qualities (Table 3) were taken as similarity coefficients and subjected to a non-metric (ordinal) multidimensional scaling procedure (smallest space analysis = SSA’. The matrix of the coefficients was given a spatial representation such that the distances between points representing the aura

81 EM

Steinmeyer

qualities reflect their similarity in as few dimensions as possible. To analyse the similarity matrix we used the SSA-I-program, one of a series of computer programs in the Guttman-Lingoes Nonmetric Program Series of MDS [email protected] This analysis provides a geometric representation of the different aura qualities as points in a Euclidian space. The distance between pairs of points in the space corresponds to the cooccurrences of the variables. Hence, two points are closer if the co-occurrence between the corresponding aura qualities is higher. There is a stress measure, which is known as the coefficient of alienation. This is a rank-order correlation between the variable’s inter-correlations and the corresponding spatial distances. The smaller the correlation, the better the fit. Smallest space analysis functions in a sequential manner to provide the minimum number of dimensions needed to obtain a geometric representation with a good fit. Following this method, the MDSanalysis shows that for the matrix only two dimensional are sufficient to adequately represent the co-occurrence patterns. For the matrix the measurement of the fit (the coefficient of alienation K) is sufficiently close to zero: K = 0.16153.

DEFINITIONS

The aura symptoms described by the patients were classified into eight categories:

Visual phenomena

These included blurred vision, diplopia, micropsia, macropsia, metamorphopsia, and elementary optic hallucinations colourless or chromatic (photoma, paropsias), as well as formed hallucinations such as moving like scenery.

Auditory

phenomena

These symptoms consisted of altered acoustic perceptions, hearing all of the sounds in a muflled way, and hearing hallucinated noises like roaring water or the firing of shots.

Autonomous

phenomena

Autonomous phenomena (synonymous to vegetative aura) are described as being like a sensation of warm feelings, a narrowing, a

Phenomenology

of simple partial seizures

pressing, or simply strange sensations which are wandering and in typical cases, ascending. ‘Crude’ sensations arise from or pass through the region around the stomach, the chest and often ascending to the throat and head. Vestibular phenomena

These comprised all kinds of epileptic vertigo. Patients experienced dizziness, the feeling of things turning around them and the sensation that they themselves are turning.

Olfactory and gustatory phenomena

These were summed because most of the patients could not clearly differentiate these qualities; their experiences consisted of strange or nasty smell/taste.

Sensory phenomena

Sensory phenomena (somatosensory phenomena) were prickling, tingling, paresthetical, or ‘electrical’ sensations, or pain in a limb, a part or one side of the body.

Dreamy states

These have been defined by Hughlings Jackson’ as a compound form of ‘intellectual aura’. They included particular variants of cognitive disturbances like deja-vu illusions, depersonalizations and derealizations. Most of the features closely resemble the descriptions of ‘experimental phenomena’ given by Penfield and Perot’.

lctal fear

Ictal fear was recorded separately because some patients suffered from anxiety not connected with the anticipation of further aura symptoms or seizures.

RESULTS

On the basis of these definitions, the reports of 325 patients having experienced auras yielded a sample of 516 symptoms. Most auras were composed of a list of a maximum of 13

phenomena. One hundred and forty-four patients were reported to have had at least two symptoms, 114 patients at least three, and 50 patients remembered at least four different symptoms. On the other hand, 134 patients (41.2%) suffered from apparently monosymptomatic seizures. For the isolated phenomena (see Table 1) we calculated the actual frequencies compared to the expected frequencies. There was a positive excess of visual and autonomous signs that were isolated. The negative excess of auditory and vestibular phenomena, as well as of ictal fear, indicates that they have the tendency to occur combined rather than being isolated. To discover the structure of combined phenomena (see Table l), we determined the transition steps from one symptom to the other. We expected that symptoms had a tendency to precede or to follow the other. This was based on the reports of 114 patients who had experienced at least three symptoms, in each series the symptoms were numbered following the order of appearance. The position within each series determined whether the symptom is subsummed under the feature ‘preceding’ or ‘following’ or both. To detect any trends in these features, we calculated ratios of the frequencies of symptoms subsummed under the columns. The most frequent signs of all aura qualities, autonomous phenomena, predominate in preceding phenomena and in isolated forms. Vestibular phenomena, significantly rare among isolated forms, represent the strongest preceding feature. Visual, olfactory/gustatory and dreamy state symptoms tend to finish an aura set, whereas auditory signs and fearful feelings tend to be framed by neighbouring phenomena. To test the second hypothesis, we grouped phenomena with ‘preceding’ and ‘following’ features against those without pronounced tendencies (see Fig. 1). The numbers associated with the arrows show how often transition steps from one group to the other have been observed. Differences between the numbers represent strong trends (Jonckheere-Terpstra, P = 0.06). Further information on properties of polymorph simple partial seizures are to be gained from the analysis of a co-occurrence pattern of aura phenomena. Ih Table 2 combinations of separate signs observed in all patients are listed independently from time sequence. Every number in the data space of Table 2 represents a pairwise co-occurrence of two aura qualities which were taken as similarity coefficiencies for the Smallest Space Analysis (numbers on the top of every column repeat

286

Ft. Erkwoh & EM. Steinmeyer

Table 1: Aura features in sequencies in 325 patients. comparision to total sum of each observed quality

Aura quality

Phenomena isolated n

Visual Auditory Autonomous Vestibular Olfact/gust. Sensory Dreamy state Fear Total

Frequencies

31 1 53 5 11 14 I7 2 134

of isolated

phenomena

and cf those

connected

to others

in

Phenomena connected to others total

(bi - eJ*

ei 9.31*t 16.06*$ 68.06*$ 9.31** 2.72 0.89 0.06 14.22*$

Preceding5

[email protected]

Ratio

n

29 20 36 24 8 38 20 16 191

37 19 27 17 19 30 26 I6 I91

0.78 1.00 1.33 1.41 0.50 I .06 0.77 1.00

97 40 116 46 38 82 63 34 516

*, Critical value: Chi-Square (1.1 - a/8) = 7.62; t, value > expected: $, value
noncombined symptoms). As the co-ordinates of the aura qualities (see Table 3) and their plotted solution (see Fig. 2) demonstrate, the twodimensional representation of the matrix shows an ordinal radex: Axes dividing the space according to elements of the circle and segments are drawn. The circle which reflects the partitioning according to the ‘centrality’ of the aura qualities points out that the visual, autonomous, and sensory signs are at the centre of the configuration, whereas the vestibular, olfactory/gustatory, auditory, dreamy states, and fear qualities occupy the outer regions. Similarly, the wedge-like shapes conform to regions in which different aspects of aura qualities can be differentiated. There is strong evidence that the aura signs located in the centre of the radex tend to show higher similarity (regardless of the particular symptomatology) than is the case

preceding tendencies:

another:

with the signs in the outer regions. The sectored syndrome facet has a polarizing nature differentiating the aura qualities where the similarity is not large.

DISCUSSION

Jane’ and Kanemoto and Janz’ administered the method of phenomenological analysis for the exploration of composed auras with the result that their multiple symptomatology involves cortical and subcortical networks. They recognized a crucial problem also shared by our study-the memory of the patients whose files are used may be unreliable in reproducing the correct symptoms in exact sequence. We found no motor signs documented in auras. This was probably because they were not self-experienced, but it is

following tendencies:

autonomous Fig. 1: Transitional directions of aura qualities of 114 patients with at least 3 symptoms. Phenomena with ‘preceding’ and ‘following’ features were grouped against those without pronounced tendencies. The arrows show the directions of sequencing symptoms. The numbers associated with the arrows note how often these steps from one group to the othr have been observed. Differences between the numbers represent strong trends (Jonckheere-Terpstra, P = 0.06).

Phenomenology Table

2: Aura

Quality

of aura

Visual Auditory Autonomous Vestibular Olfact./gustaL Sensory Dreamy state Fear

of simple partial seizures qualities

in 325 patients

287

combined

with each

Auditory

Autonomous

Vestibuiar

OlfactJgustat.

Sensory

Dreamy state

Fear

31 10 12 12 6 14 6 6

1 8 4 5 4 6 2

53 6 4 15 9 9

-

11 5 4 1

14 11 8

17 5

2

evident that they do exist. This problem is inevitable. Thus, all conclusions have to be interpreted with caution. Autonomous signs labelled vegetative, gastric, epigastric, abdominal or cardial auras by others, show a leading position which is in line with statistics found by Gowers’” and Lennox and Cobb”. The localizing value of this type is rather low. It is reported by patients with proven extratemporal, particularly frontal lobe epilepsy’*. Abdominal sensations can be reproduced by experimental stimulations in several cerebral regions: posterior central gyrus13, inferior precentral region14, supplementary motor region’4.‘“, in three studies from the insular cortex’S-‘6, from fornix”, amygdala, hippocampus including uncus and furtheron area olfactoria, inferior and medial pallidum, capsula interna, centrum medianum of thalamus’“. The other qualities wth preceding features in aura sequences seem to be less variable in origin: vestibular sensation, derived from parietal or temporoparietal areas’5*‘y-2’ more rarely from frontal sites”.**, and sensory phenomena which are mostly referred to the postcentral gyrus’s*23. There is some evidence of somatosensory auras occurring in frontal lobe epilepsy3.*‘. The occurrence of psychic symptoms in dreamy states, a compound form of an ‘intellectual aura”, Table 3: Co-ordinates of aura qualities in two dimensions. Values for each quality (= variable) calculated for the plotted figure (see Fig. 2) by Smallest Space Analysis

Variable

Visual Auditory Autonomous Vestibular Olfact./gustat. Sensory Dreamy stale Fear

other

Visual

Dimension I

I1

-0.07 -0.55 0.36 -0.42 -1.38 0.28 0.37 1.40

-0.26 0.93 -0.14 - 1.26 0.25 -0.41 0.74 0.15

5 2 11 5 I

as the sole manifestation of a simple partial seizure is uncommon, probably because most psychic symptoms occur as part of complex-not simple-partial seizures. In our study dreamy states tend to be escorted by forerunners, so that their localizing value is doubtful. Illusions of familiarity were associated with stimulation of the non-dominant temporal lobe*‘. The remaining qualities show more clear links to cerebral substrates: visual perceptions, especially elementary photomas (so-called paropsias) are referred to the contralateral area striata if they appear unilaterally and in a coloured or moving shape”.*‘. Olfactory hallucinations may result

0

-1.5

-2.0

I

I

-1.5

-1.0

I

I

I

-0.5 0.0 0.5 Dimension I

I I.0

I I.5

2.0

Fig. 2: Radex figure of aura qualities. The points representing each aura quality are calculated from the coordinates of Table 3. The distance between pairs of points corresponds to the co-occurrences of the variables in Table 3. Two points are closer if the co-occurrence between the corresponding aura qualities is higher. The two-dimensional representation of the matrix shows an ordinal radex. Axes divide the space according to elements of the circle and segments. The circle reflects the ‘centrality’ of the aura qualities. It demonstrates that the visual, autonomous, and sensory signs at the centre of the configuration tend to show higher similarity than is the case with the signs in the outer regions. Similarly, the wedge-like shapes conform to regions in which different aspects of aura qualities can be differentiated. The vestibular, olfactory/gustatory, auditory, dreamy states, and fear qualities occupying the outer regions tend to be less similar to each other as well as to the central symptoms.

Ft. Erkwoh 81 EM Steinmeyer

288

from stimulations of the uncus gyri hippocampi, bulbus olfactorius, hippocampus and of amygdala via mediotemporal transitional cortex26. They are often combined to gustatory sensations by forming the so-called ‘uncinate fits’. Our study suggests that the difference between aura qualities with preceding tendencies and those with following tendencies is of some importance. The difference is not significant but a strong trend exists (P = 0.06) probably because here, autonomous signs and there dreamy states are both difficult to define. With great caution the impact of the literature may be interpreted that some symptoms with more ‘preceding’ features in our sense (vestibular, sensory) more often point to cortical structures while some with ‘following’ properties involve more subcortical, limbic areas (olfactory/gustatory). Auditory perceptions show the highest localizing value of all simple partial seizures. They are linked to the transverse gyri of Heschl and to posterior sections of the first temporal convolutions*‘. Ictal fear is experimentally obtained by stimulation or rises from discharges in limbic structures of the temporal lobe. Amygdala more likely produced sensations of fear than does the hippocampu?. The first temporal convolution and adjacent limbic circuits may be neural candidates for propagation of ictal activity, as phenomena ascribed to these tissues prefer to mediate between symptoms. A facet theoretical interpretation of the regions of the spatial representation groups together visual, sensory and autonomous signs, the latter two probably referring to the postcentral gyrus including thalamo-postcentral projections. Creutzfeldt29 described thalamic projecting neurons to the visual cortex in area 17. Our study has been a retrospective evalaution using a classification of symptoms more elaborate than the usual system of the ILAE. Our conclusions may not therefore be supported by a prospective study. Criticism may be justified with respect to a catalogue of phenomena possibly too elaborated, but this procedure seemed to be most useful for portraying the authentic polymorphism of simple partial seizures.

CONCLUSIONS

Hughlings Jackson’s hypothesis’ suggested that the onset of the epileptic aura indicates the focus of the discharge and that the succession of symptoms demonstrates the pathways of dis-

charge propagation. Thus, the idea of studying aura phenomena by determining their different elements in terms of their temporal sequence, and to infer from this sequence the origin and possible propagation pathways is not new. By putting the emphasis on a scrutinizing phenomenological study, we rule out speculation on anatomical generators in the absence of EEG controls and without anatomical, lesion or stimulating experiments. From our results, however, we can see that there are 191 patients with composed simple partial seizures vs. 134 patients with monosymptomatic auras; there is a predominance of multi-faceted phenomena, like autonomous phenomena occurring in isolated forms as well as in composed auras; a high inclination of autonomous signs to be combined with visual and sensory phenomena. We conclude that for the attempt of neural localization of simple partial seizures the idea of heterogeneity does fit, rather than that of a strongly restricted focal discharge.

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