Clinical significance of the photomyoclonic response in psychiatric patients

CLINICAL SIGNIFICANCE OF THE PHOTOMYOCLONIC RESPONSE IN PSYCHIATRIC PATIENTS 1 CHAaLES SHAOASS, M.D. Al/an Memorial Institute of Psychiatry and McGill University, Montrea/ (Received for publication: January 29, 1954) INTRODUCTION In some individuals, intermittent photie stimulation produces muscular jerking, affecting principally the facial muscles, and associated, in the E E G tracing, with "frontal polyspikes", which are probably of palpebral origin (Gastaut 1950, 1952). Bickford, SereJacobsen, White and Daly (1952) have designated this the "photomyoclonic response" and have set forth a number of criteria which distinguish it from the "photoconvulsive response". The photomyoclonic response has also been termed the "photooeuloclonic reflex" by R~mond (1952) and the "fronto-polar response" by Gastaut (1952). The clinical significance of the photomyoclonie response has remained uncertain. Gastaut (1952) stated that the response is elicited with particular ease in patients suffering from certain psychopathic states and in those with neurologie disorders affecting, directly or indirectly, meso-diencephalic structures. Dongier (1951) found the response more frequently in a mixed group of psychiatric patients than in normal controls. On the other hand, Bickford et al. (1952) concluded that the photomyoclonic response may be considered a normal one to high intensity light stimulation and that, as such, its occurrence would have little clinical significance. Since the reported correlations between susceptibility to photomyoclonic response and presence of certain psychiatric disorders (Gastaut 1950; Dongier 1951) have important practical and theoretical implications, further study along these lines seemed indicated. The

purpose of the present investigation was to determine, for a psychiatric population, the clinical significance of a photomyoelonic response to light stimulation alone, i.e. without Metrazol. The relationship of the following clinical factors to incidence of photomyoelonic responses was studied: type of psychiatric disorders, E E G abnormality, age, sex, personal and family history of seizures, electroconvulsive therapy, drug intoxication and addiction. MATERIAL AND METHOD

Patient material consisted of 411 consecutive admissions to the Allan Memorial Institute who received routine E E G examinations and photic tests, The period of study was about one year. There were 162 males and 249 females. Age range was 17 to 74; median age was 36.8 years. The two sexes were approximately equal in age. Details of diagnosis will be presented in description of results (tables I, II). Thirty non-patient subjects were also tested in order to obtain some idea of the frequency of photomyoelonic responses in a presumably normal group. There were 13 male and 17 female control subjects, drawn mainly from hospital staff. Ages ranged from 18 to 45 years, with a median of 27.1 years. The male group was somewhat older than the female (medians of 29.3 and 24.2 years respectively). Records were taken with a six channel Grass Model III-C instrument. Bentonite paste leads were used. The light source was a strobotron-type flash tube (GE FT 110), activated by a 1000 volt charge in a 1 microfarad condenser. The light was kept about 4 to 5 inches from the eye and stimulation 1 This researeh was supported by a grant from was carried out with the eyes closed. The the Department of National Health and Welfare, apparatus was not noiseless, each flash being Canada. accompanied by a click. Perhaps the term, [445 ]

446

CHARLES SHAOASS

"combined photic and sonic stimulation", would be more descriptive of the procedure. The sequence of stimulation was as follows: (a) 5 per sec. single flashes for 5 to 10 sec.; (b) 2 to 3 sequences of 10 per sec. single flashes lasting 10 to 15 sec. each; (c) 2 to 3 sequences of 15 per sec. single flashes lasting 10 to 15 sec. each; (d) 2 sequences of 5 per sec. twin flash stimulation (interval between paired flashes, 65 msec.) lasting 30 to 40 sec. each; (e) a rapid scanning of the entire frequency range from 5 to 20 flashes per see. 1 In each ease of suspected photomyoelonic response, clinical eonfirmation was sought by inspection, palpation and questioning of the patient. At the time records were taken, the author classed them as negative, borderline or definite with respect to photomyoclonic responses and noted degree of body involvement in the response. Borderline responses were those in which a minor degree of palpebral fluttering was clinically noted, but where the E E G artifact was not typical (fig. 1). Definite responses involved a clear clinical effect and typical E E G artifact (fig. 1) ; these were f u r t h e r subdivided into (a) those in which facial structures only participated, and (b) those where structures below the neck were also involved in muscular jerking at the flash rate. At the time of data analysis all records not clearly negative were re-examined without knowledge of clinical findings. With a f e w exceptions in the borderline group no change in the original classification was found necessary. Clinical information was obtained from hospital records by a second 1 It is recognized that standardization of the photic stimulation procedure, while highly desirable, is very difficult to achieve, and was achieved in only a limited sense in the present study. Even when such factors as intensity, duration, and frequency of stimulation are controlled, stimuli may not be considered exactly comparable from one person to another due to variations in thickness of eyelids and degree of eyelid tension. These considerations make it difficult to compare incidence of responses from one laboratory to another. They necessitate a statistical approach to data from a single laboratory, where different types of subjects are studied by a reasonably standardized procedure. Conclusions derived from such an approach should, however, be qualitatively the same, even though quantitative details may vary.

psychiatrist who did not know the classifi-cation of photomyoclonic responses. Control subjects were questioned directly concerning personal or family history of seizures, fainting spells and use of sedatives. RESULTS

Incidence of Photomyoclonic Responses. Some form of photomyoclonic response was observed in 83 (20.2 per cent) of the 411 patients studied. The response involved both face and body in 14 cases (3.4 per cent), was definite but confined to the face in 41 cases (10.0 per cent), and was classed as borderline in 28 cases (6.8 per cent). One borderline and two definite facial responses were elicited in the 30 controls. This incidence of 10 per cent in the controls was statistically not significantly lower than the incidence in the patients. Present data on controls demonstrate only that, under the conditions of this study, photomyoclonic responses could be elicited in non-patient subjects. A valid comparison of psychiatric patients and normals would require a much larger control group matched for sex and age. Age. There was no significant age difference between patients with and without photomyoclonic responses, the median ages being 35.8 and 37.1 years respectively. Sex. Photomyoclonic responses of each type occurred with greater frequency in female patients. While 62 or 24.8 per cent of the females showed some form of response, only 21 or 13.0 per cent of the males did. This difference was statistically significant by the chi square test (P ~.01). The 3 control subjects with a response were all females. Resting EEG. Eight (9.6 per cent) of the patients with photomyoclonic responses and only 13 (4.0 per cent) of the negative group had abnormal E E G findings. This difference was significant at the 5 per cent level of confidence. Most of the abnormalities in the photomyoclonic group were bilateral paroxysmal dysrhythmias, while most of those in the negative group involved either diffuse slowing of background rhythms or asymmetries related to previous vascular accidents, etc. The relatively low proportion of EEGs considered abnormal in this psychiatric popula-

SIGNIFICANCE OF PHOTOMYOCLONIC RESPONSE

tion as compared with others (e.g. Kennard 1953) may probably be attributed to application of stricter criteria of abnormality. Psychiatric Diagnosis. Table I shows the incidence of photomyoclonic responses by

447

3 of 6 patients showed the response. The small number of conversion hysterics permits no definite conclusions. There were no statistically significant differences between any of the other groups. The type of response J

slight twitching; of eyelids

R(SPONS(

!

- FAGE ONLY

eyelids twitching

~!5 p.,. ~ , f~,~,,

jerking of heod ond body

Fig. 1 Examples illustrating classification of photomyoelonic responses. cruiting effect where response was definite.

psychiatric diagnosis. The 2 patients with a primary diagnosis of epilepsy, idiopathic type, both had a photomyoclonie response. Apart from the epileptics, the only diagnosis with a high incidence of photomyoclonic responses was conversion hysteria, in which

Note re-

(definite or borderline) was not related to psychiatric diagnosis. A special analysis was made of the incidence of responses with respeet to sub-type of schizophrenia, since a zero threshold has been reported in catatonics (Hill 1952). The

448

CHARLES SHAGASS

r e s u l t s a r e s h o w n in t a b l e I I . T h e r e w e r e no s t a t i s t i c a l l y r e l i a b l e d i f f e r e n c e s b e t w e e n a n y o f t h e s u b - t y p e s . O f t h e 10 c a t a t o n i c

episodes of i m p a i r e d c o n s c i o u s n e s s ; seizure~, a s s o c i a t e d w i t h i n s u l i n t h e r a p y , d r u g withd r a w a l or a l c o h o l i s m ; f a m i l y h i s t o r y of sei-

TABLE I INCIDENCE OF PHOTOMYOCLONIC RESPONSE BY PSYCHIATRIC DIAGNOSIS No. Cases Diagnosis

Schizophrenias 98 Depressions 143 Anxiety states 67 Mixed psychoneuroses 17 Obsessive-compulsives 15 Organic and senile states 16 Character disorders (psychopaths) 13 Alcoholism 11 Paranoid states 7 Conversion hysteria 6 Hypomanie states 5 Idiopathic epilepsy 2 Miscellaneous 1 11 Total

411

No. with PMlt

Per cent PMtt (All types)

Definite

Borderline

All type.~

18 17 8 1 0 1 2 1 1 3 1 2 0

7 8 5 2 2 1 1 2 0 0 0 0 0

25 25 13 3 2 2 3 3 1 3 1 2 0

9,5.6 17.5 19.4 17.6 13.3 12.5 23.1 27.3 14.3 50.0 20.0

55

28

83

20.9,

0.0

l Includes: psychogenic headache (3 cases) and one each of: asthma in a schizoid personality, hyperi~nlinim~a, hypoehondriasie, tortieollis in a deaf mute, compensation neurosis, demerol addiction, Meni~re's syndrome, and simple inadequate personality. s c h i z o p h r e n i c s o n l y 3 g a v e a response. T h e borderline schizophrenic group showed the h i g h e s t i n c i d e n c e of r e s p o n s e . H o w e v e r , t h i s g r o u p also c o n t a i n e d t h e g r e a t e s t n u m b e r o f cases w i t h a h i s t o r y o f seizures. H i s t o r y o f Seizures, Coma, A d d i c t i o n , or Intoxication. Experience with photic stimulation prior to a n a l y s i s of p r e s e n t d a t a h a d l e d to t h e impression that photomyoclonic responses were c o m m o n in p a t i e n t s w i t h o u t c l i n i c a l e p i l e p s y , b u t w i t h a h i s t o r y of c o n v u l s i o n s u n d e r special c o n d i t i o n s , e.g. i n s u l i n t h e r a p y . T h e response h a d also b e e n n o t e d in p a t i e n t s who h a d r e c e n t l y r e c o v e r e d f r o m c o m a d u e to a suicide attempt with barbiturates. Following t h i s l e a d , a l l case h i s t o r i e s w e r e c a r e f u l l y c h e c k e d f o r e v i d e n c e o f d e v i a n t c e r e b r a l excitability, of either a constitutional or induced n a t u r e . F o r p u r p o s e s o f s t a t i s t i c a l a n a l ysis, t h e p r e s e n c e o r a b s e n c e o f each o f t h e following items was noted: epileptic seizures;

z u r e s ; d r u g a d d i c t i o n o r i n t o x i c a t i o n ; alcoholism; previous eleetroconvulsive therapy (ECT). T a b l e I I I shows t h e i n c i d e n c e of these h i s t o r y f i n d i n g s in p a t i e n t s w i t h a n d w i t h o u t p h o t o m y o c l o n i c responses. D a t a a r e also s h o w n f o r a g r o u p of p a t i e n t s w i t h o u t phoTABLE I I PHOTOMYOCLONIC RESPONSES IN SUB-TYPES OF SCHIZOPHRENIA Type of Schizophrenia

No. Gases

No. PMR 's

Per teat PMR 's

Paranoid Borderline Catatonic Simple Hebephrenic

42 16 10 11 1

8 7 3 2 1

19.1 43.7 30.0 18.2

Mixed

9

1

Sehizo-affective Post-partum

6 3

1 2

11.1 16.7

98

9,5

Total:

9,5.6

SIGNIFICANCE OF PHOTOMYOCLONIC RESPONSE tomyoclonic responses selected to m a t c h the response g r o u p for age (within 5 years), sex, psychiatric diagnosis, and insulin t h e r a p y d u r i n g hospitalization. The d a t a indicate that almost all of the history items were more frequent in the photomyoelonic group. Results for the unselected and matched negative groups were about the same, indicating that the results were not u n d u l y influenced by a n y of the factors considered in matching. ( a ) S e i z u r e s . The incidence of a personal or family history of seizures of any 'kind (ex-

449

The results also suggest a relationship between incidence of responses and dose of barbiturates. Most of the negative history group had probably received barbiturates in therapeutic dosage some time prior to testing. Response incidence in this g r o u p was 12.9 per cent, compared with 44.4 per cent in the group with barbiturate addiction or intoxication and 80.0 per cent in the recent coma group. ( c ) E C T . A history of previous E C T was found in 51 patients, of whom 14 (27.4 per

TABLE I I I INCIDENCE OF HISTORY OF SEIZURES, COMA, ADDICTION OR INTOXICATION IN PATIENTS WITH AND WITHOUT PHOTOMYOCLONIC RESPONSE All Patients with no P M R History FOrding

Negative history ' ' Spontaneous'

' seizures

or

Pafieats toith P M R

No.

Percent

1~o.

Percent

No.

P ereea t

251

76.5

67

81.8

37

44.6

2 3 8

0.8 0.9 2.4

1 1 1

1.2 1.2 1.2

6 5 7

7.2 6.0 8.4

2

0.6

1

1.2

0

0.0

1

0.3

0

0.0

4

4.8

5 1 18 7 30

1.5 0.3 5.5 2.1 9.2

1 0 3 1 6

1.2 0.0 3.7 1.2 7.3

4 0 6 7 7

4.8 0.0 7.2 8.4 8.4

328

99.9

82

100.0

83

im-

paired consciousness Family history epilepsy Seizures with insulin Seizures after drug withdrawal 2 Barbiturate coma (within 3 wks.) Barbiturate addiction or intoxication Bromide intoxication Alcoholism ECT within past 4 mos. ECT more than 4 mos. before Total:

Matched Group with no P M R 1

99.8

1 One patient in PMR group (toxic state) could not be matched. 2 Dilantin, I; alcohol, I. eluding those due to E C T ) was 21.7 per cent in patients showing photomyoclonie responses, compared with only 4.6 per cent in the negative group. This difference was highly significant statistically ( P <.001). (b) B a r b i t u r a t e s . The 5 cases of recent barbiturate coma had recovered clinically when tested, so that the resting E E G was normal. Nevertheless, 4 of them gave a photomyoclonic response, suggesting a residual cerebral effect of massive barbiturate dosage.

cent) showed a photomyoclonie response. Analysis of incidence of responses with respect to number and recency of E C T was carried out. Number of treatments bore no significant relationship to incidence of response. However, there seemed to be a critical time factor at about 4 months. I n 14 patients receiving E C T within 4 months of testing, incidence of photomyoclonic responses was 50.0 per cent, while in 37 patients treated more than 4 months before it was only 18.9

450

CHARLES SHAGASS

per cent. This difference of incidence with relation to time of t r e a t m e n t in the E C T group was statistically reliable (P ( . 0 5 ) . (d) Alcoholism. There were 24 cases in which alcoholism was a problem; in ]1 cases it was the p r i m a r y problem and in 13 cases it was secondary to another diagnosis. The incidence of alcoholism was somewhat higher in the group with photomyoclonic responses, but the difference was not statistically reliable. The histories in the control group were almost entirely negative. Two subjects, one of whom gave a response, reported fainting spells under special circumstances such as p r e g n a n c y and excessive heat. The father of one subject with no response had had seizures for seven years before his death. Degree of Body Participation in Photomyoclonic Response. The type of photomyoclonic response borderline, facial, body) gives a rough index

of deviant cerebral excitability. Statistically, this association was highly reliable (P <.001). Table I V suggests t h a t borderline r e sponses were of little clinical significance. On the other hand, definite responses were found in 45.2 per cent of all cases with a positive history. F u r t h e r m o r e , a definite response signified a 1:2 chance of a positive history, while a negative or borderline response i n dicated a 1:]0 chance. A definite photomyoclonic response could then be interpreted as a sign of deviant cerebral excitability. Stimulus Frequency and Duration. The frequency at which the photomyoclonic response was first elicited and the dura~ tion of preceding stimulation were compared with type of response and history findings in order to determine the influence of these stimulation variables. This analysis showed only two trends, neither of which was statistically significant: (1) a relatively greater

TABLE IV TYPE OF PHOTOMYOCLONIC RESPONSE AND INCIDENCE OF POSITIVE HISTORY FINDINGS (SEIZURE, COMA, INTOXICATION) Total Group Type of PMR

No. Cases

Matched Group

Positive History No. Percent

No. Cases

Positive History No. Pervent

Body Face Borderline No Response

14 41 28 328

10 ]8 5 29

71.4 43.8 17.9 8.8

13 41 28 82

9 18 5 6

69.2 43.8 17.9 7.3

Total:

411

62

] 5.]

164

38

23.2

of degree of body participation in the response. The incidence of all history findings significantly correlated with the response was determined for each type. D a t a are shown in table I V in which " p o s i t i v e history'.' includes all items listed in table I I I , with the exception of alcoholism and E C T more than 4 months previously. Comparable data for the matched group are also shown in table IV, and the d a t a for the unselected group are g r a p h e d in figure 2. The results show clearly that the greater the extent of body involvement in the photomyoclonic response, the more likely a history

proportion of borderline t h a n definite responses occurred with 5 per see. twin flashes. (2) patients who first showed the response with twin flash stimulation had negative histories relatively more often t h a n those who responded to single flashes. Two of the three controls with responses showed these with twin flashes. Results indicate that, under conditions of this study, s t i m u l u s frequency and duration were not significant variables. I t should be noted, however, t h a t the twin flash sequences followed the single flash series and t h a t 33 (38.4 per cent) of the responses did not occur until twin flashes

SIGNIFICANCE OF PHOTOMYOCLONIC RESPONSE

were applied. This supports the impression (Gastaut and Corriol 1951) that twin flashes are particularly efficacious in eliciting the photomyoclonic response, often succeeding where single flashes fail. DISCUSSION

The purpose of this study was to ascertain what clinical factors are associated with a photomyoclonic response to light stimulation

451

of larger samples of certain conditions, e.g., conversion hysteria, might alter this conclusion. The control group of this study was too small to provide definite evidence eoneerning the question of differences between psychiatric patients and normals. Present data strongly suggest that in such comparisons the differential incidence of histories of deviant cerebral excitability must be taken into ae-

80 >no

Iu) b.I

~O 6o

>

1-

0D.

50

3: I--

40

u.I

50

~ 7 w o !1~ w n

20

(N

I0

NO RESPONSE

BORDERLINE

FAGE ONLY

FAGE AND BODY

TYPE OF PHOTOMYOCLONIC RESPONSE Fig. 9. Incidence of positive history of deviant cerebral ezcitability for each type of photomyocionic response. Positive history findings include: spontaneous seizures or impaired consciousness, fAmi!y history of epilepsy, seizures with insulin or after with drawal of drugs or alcohol, recent barbiturate coma, barbiturate addiction or intoxication, ECT within past four months.

alone in psychiatric patients. The results indicated that this response may be a sign of deviant cerebral excitability, e.g., as indicated by a history of seizures, either "spontaneous" or induced. Incidence of responses was not found to be a function of type of psychiatric disorder. However, it is conceivable that study

count. The incidence of definite responses in the control group was 6.7 per cent, compared with 13.4 per cent in the patients. If cases with a history of deviant cerebral excitability were omitted, the incidence in patients would fall to 7.7 per cent. Present results support the view that the

452

CHARLES SHAGASS

photomyoclonic response is of clinical significance (Gastaut 1952). While this view may appear opposed to the statement of Bickford et al. (1952) that the response is a normal one to high intensity repetitive stimulation in the human being, contradiction of this statement is not intended. It is felt, however, that the observation upon which Bickford et al. based this statement, namely that high intensity photic stimulation often produced photomyoclonie responses in normals, does not necessarily lead to the conclusion that the response is normal under almost any conditions. in reconciling opposing views consideration must be given to the quantitative aspects of both stimulus and response. Bickford et al. (1952) demonstrated that, in normals, responses were elicited more often with higher intensities of illumination. Carterette and Symmes (1952) listed a number of other important stimulus variables, particularly color. Deviant cerebral excitability, especially susceptibility to seizures, is known to vary from one time to another in the same individual. Present data showed that, under given stimulus conditions, the greater the response, as reflected in extent of body involvement, the more likely it was to be of clinical significance. Considering these facts, it would follow that the photomyoclonic response involves a normal response mechanism, for which ease of elicitation varies in relation to degree of deviant cerebral excitability. The clinical significance of a response would then have to be interpreted in terms of the quantitative aspects of the stimulus, a body response at low intensities probably being of greater significance than a palpebral response at high intensities. Since responsiveness also varies, it should not be anticipated that any particular stimulating conditions will yield results of uniform significance. It should be expected that such correlations will be statistical in nature, with the likelihood that systematic investigation will define stimulus conditions of optimal predictive value. It should be made clear that, in the foregoing discussion, the photomyoclonic response, correlated with deviant cerebral excitability, has been regarded as a physiological sign. It

has not been considered to be necessarily ass(~ elated with specific structural pathological changes, although it seems clear from the work of Gastaut (1950, 1952), that such an association is possible. Presumably, where a lesion is present, it may increase the irritability of structures mediating the photo myoclonic response. Sensitivity could also be increased, but on a reversible physiological basis alone, by agents such as massive doses of barbiturates or electroshock. Increased irr'i tability could also be inborn without apparent structural change, as in those individuals with it family history of epilepsy. Present data contribute no direct information bearing on the mechanisnl of the photomyoclonic response. The greater incidence ~Jf the response in females is difficult to explain and suggests that background hormonal factors may require scrutiny. The observation of Lin, Greenblatt and Solomon (1952) that epileptic discharges were elicited by flickering light more frequently during menstruation may be relevant in this connection. The association of the response with recent ECT and with barbiturate intoxication probably lends support to the concept that the reticular system is involved iu the elaboration of the response (Van Bogaert, Radermecker, and Titeea 1950). Both of these agents are thought to have important effects on the activity of mid-brain and thalamic reticular systems (Roth 1951). As a sign of deviant cerebral excitability, the photomyoelonic response appears far from specific. Half of the group showing it had a negative history, while over half of the patients with a positive history did not show the response. However, in view of the widespread use of photie activation and the frequency with which EEGs are taken on psychiatric patients, the correlations demonstrated here would seem of practical importance. The psychiatric patient population, for reasons of therapeutic history alone, contains a relatively high proportion of individuals whom one would expect to show a photomyoclonic response. In this group, subjected as it is to such seizure activating procedures as insulin hypoglycemia and barbiturate withdrawal after prolonged narcosis therapy, the occur-

SIGNIFICANCE OF PHOTOMYOCLONIC RESPONSE

453

renee of "non-specific" eonvulsions is common. The clinical electroencephalographer will frequently be asked for studies on patients who have had such seizures, and often the photomyoelonie response may be the only positive finding. With no other neurological or EEG findings, such cases would be thoughl to have a latent seizure tendency of "functional" nature. The photomyoclonic response supports such an appraisal in a positive way.

logical sign of deviant cerebral excitability. Investigative attempts to correlate the response with psychiatric disorder will require control of this factor.

SUMMARY

and DALY, D. Some observations on the mechanisms of photic and photo-metrazol activation. EEG Clin. Ne~rophysioZ., 1952, 4: 275-282. CAR~ERE~rE, E. C. and SYMMES, D. Color as an experimental variable in photic stimulation. EEG Cli~. Ne~rophysiol., 1962, 4: 289-296. DONOIEE, M. L'exploration fonctionnelle du cerveau par la m~thode photocardiazolique. Thesis presented to the Mixed Faculty of General and Colonial Medicine and Pharmacy of Marseille, 1951. GASTAUT, H. Un signe 61ectroene6phalographique des hydrocephalies: la r6ponse par recrutement au cours de la stimulation lumineuse intermittente. Rev. Neurol., Paris, 1950, 8~: 410-413. GASTAU~, H. L'activation photo-cardiazolique. EEG Cli~. Neurophysiol., 1952, 4: 2711274. GASTAU'r, H. and COgRIOL, J. Note pr~liminaire sur un proc6d6 nouveau et particuli~rement efficace de stimulation lumineuse intermittente. EEG Clin. Ne~zrophysiol., 1951, 3: 87-88. HILL, I). EEG in episodic psychotic and psychopathic behavior. EEG Clin. Neurophysiol., 1952, 4 : 419-442. KENNARV, M. A. The electroencephalogram in psychological disorders. Psyehosom. Med., 1950, 15: 95-115. LIN, W., GREENBLATT,M. and SOLOMON,H. C. Effect of flickering light on epileptic discharges: influence of medication and menstruation. EEG Clin. Neurophysiol., 1952, 4: 552-560. R~MONV, A. Photometrazol activation. EEG Clin. Ne~rophysiol., 1952, 4: 265-270. ROTH, M. Changes in the EEG under barbiturate anaesthesia produced by electro-convulsive treatment and their significance for the theory of ECT action. EEG Clin. NeurophysioZ., 19B1, $: 261-280. VAN ROGAERT,L., RADERMECKER,J. and TITECA, J. Les syndromes myocloniques. Folia Psyehiat. Neerl., 1950, 53: 650-~90.

1. T h e p u r p o s e o f t h i s s t u d y was to det e r m i n e t h e c l i n i c a l c o r r e l a t e s of t h e p h o t o m y o e l o n i c r e s p o n s e to i n t e r m i t t e n t l i g h t s t i m u l a t i o n a l o n e i n p s y c h i a t r i c p a t i e n t s . T h e rel a t i o n s h i p of a n u m b e r of c l i n i c a l f a c t o r s to i n c i d e n c e of p h o t o m y o e l o n i c r e s p o n s e s w a s d e t e r m i n e d i n a g r o u p o f 411 p a t i e n t s . A c o n t r o l g r o u p of 30 n o n - p a t i e n t s u b j e c t s w a s also s t u d i e d . 2. I n c i d e n c e of r e s p o n s e s w a s n o t sign i f i c a n t l y r e l a t e d to t y p e o f p s y c h i a t r i c diso r d e r o r to age. I n c i d e n c e w a s l o w e r i n eonl r o l s t h a n in p a t i e n t s , b u t n o t s i g n i f i c a n t l y so. Responses occurred significantly more often in f e m a l e t h a n i n m a l e p a t i e n t s . A b n o r m a l ities i n t h e r e s t i n g E E G w e r e m o r e f r e q u e n t in p a t i e n t s w i t h responses. T h e m o s t signif i c a n t c o r r e l a t e s of t h e r e s p o n s e c o u l d be g r o u p e d as " h i s t o r y o f d e v i a n t c e r e b r a l excitability" and included: personal and family h i s t o r y of " s p o n t a n e o u s " seizures, s e i z u r e s with insulin, recent electroeonvulsive therapy, r e c e n t b a r b i t u r a t e coma, b a r b i t u r a t e a d d i c tion and intoxication. It was found that the greater the extent of bodily involvement in the response, the higher the incidence of a "history of deviant cerebral excitability". 3. I t w a s c o n c l u d e d t h a t t h e p h o t o m y o elonie r e s p o n s e m a y be r e g a r d e d as a p h y s i o -

The author wishes to acknowledge his indebtedness to Dr. James Nniman who assisted in classification and statistical analysis of the clinical data and to Miss Sabina Migicovsky, who took the records. REFERENCES BICKFORD, R. G., SEM-JACOBSElq, C. W., WHITE, P. T.

Refere~tce: SHAOASS, C. Clinical significance of the photomyoclonic response in psychiatric patients. EEG Clin. Ne~rophysioL, 19~1, 6: 445-453.