EEG findings in Parkinsonism

ELECTROENCEPHALOGRAPHYAND CLINICAL NEUROPHYSIOLOGY

CLINICAL

AND

LABORATORY

321

NOTE

EEG FINDINGS IN PARKINSONISM A. A. S m A K O V

A N D I. S. M E Z A N

Neuropsychiatric Institute, Sofia (Bulgaria) (Received for publication: July 31, 1962) There have been hitherto comparatively few pape~ on the study of the EEG in Parkinson's syndrome. The subject has been controversial since 1936, when brain waves synchronous with the rhythm of the tremor were described. In 1939 Schwab and Cobb demonstrated the artificial origin of these waves and most of their 38 cases were described as normal. Recently Schwab, England and Peterson (1958) and England, Schwab and Peterson (1959) pointed out the increased average age of the patients, in their new series about 4(P/o showed abnormal EEGs. We thought it worth while to return to this subject and present the results of our experience over several years.

MATERIAL A N D METHODS

have investigated a truly random material, but we suppose that other workers have faced similar difficulties. Fourteen scalp electrodes were applied. An ear reference record was first taken, followed by a bipolar anteroposterior one and a 3-min hyperventilation test. Sixty four male and 36 female patients have been investigated; their age distribution is shown in Fig. I. The mean age of the group was 54. The mean alpha frequency of each record was evaluated by counting the alpha waves in several 3-see strips of the occipital leads. For comparison normal records were randomly drawn from our files, withou; regard to the clinical diagnosis. Diffuse theta activity, exceeding 10% of the record, was considered abnormal, unless it occurred during the last minute of hyperventila. tion.

W e have, during the lastyears,trea:edseveralhundred Parkinsonian patients in the neurological clinic of our institute. Their EEGs were recorded on admission and also after medicinal treatment for several weeks. We selected 100 cases with technically good records. Many electroencephalograms had to be discarded, because they were literally drowned in artifacts. Thus we can not pretend to

RESULTS Most of our cases (64) showed electroencephalograms which were considered to be normal according to ordinary criteria. Forty of them had well organized background activity, a high alpha index and good reactivity, these being so

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35 %

30 25

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20 10

15 lo

e

o

I

9

10

11

12

13

- Fre~ncy

Fig. I Age distribution of P.~rkinmnian patients. Abscissa: years; ordinate: rases.

Fig. 2 Frequency distribution of the alpha rhythm in normal records. Abscissa: c/see; ordinate: ca.~es in per cent. . . . . . . . Parkinmnians, - controlsof random abe, . . . . . . . . . controls over forty.

£1ecfroenccph. clin. Neurophysiol., 1963, 15:321-322

322

X. A. SIRAKOV AND I. S. MEZAN

comparable with an)" clinically healthy group. Another I 1 patients showed more p(x,rly organized EEGs, with some sporadic slow.wave activity, mostly in rostral leads, but they could still be considered as being within the normal limits. Finally, there were 13 flat electroencephalograms, with maximal amplitudes of 10-25 ,uV. Nevertheless, if the group of normal Parkinsonian EEGs is compared with other groups of randomly selected normal electroencephalograms, some striking differences can be observed. Fig. 2 shows the distribution of alpha frequencies in 50 Parkinsonians, compared with 100 normal records of patients aged over 15 and with other I00 normal EEGs belonging to patients older than forty. It can be seen that, while the alpha frequency distribution is quite similar in the control groups, it is conspicuously shifted to the left in Parkinsonian patients, with a peak frequency of 9 c/see instead of 10 c/see. The frequencies 12 and 13 c/see are entirely missing from the Parkinsonian group, while the lowest frequency of 8 c/see is largely represented. Abnormal electroencephalograms were found in 36 cases. Their age distribution was similar to that of the whole sample. The mean age was 55. The abnormality consisted most often in a slight to moderate degree of diffuse slow.wave activity (25 cases). Sometimes the abnormality could be established only during hyperventilation (7 cases). Finally, localized or bamispheral manifestations were found only in four patients. The abnormal electroencephalograms often showed also decreased reactivity of the alpha rhythm. DISCUSSION Our results ten©rally confirm the data of the long-term investigation conducted by Schwab et al. Their last publication (1959) is based on 7~ cases, of which more than 5~/o were abnormally slowed. It ~hould be pointed out, however, that "he mean age of their group was 65, or I I years hi~er than in ours. The age factor, wtth the concomitant arteriosclerosis, could modify to a certain extent the final results, although we could not observe significant age differences between the group with normal EEGs and that with abnormalities. The commonest abnormalities in the Parkinsonian electroencephalogram seeh~to consist in moderate slowing of the background rhythm with decreased reactivity, or the appearance of some slow-wave activity. As might be expected, the local EEG signs of this disease are slight, rare and without clinical correlations, We also stress for the first time the evident tendency to slowing of the alpha rhythm, even in patients with normal EEGs. Flat EEGs were observed in 13~ of the cases. This figure corresponds with that expected in any neurological

population (epileptics and neurotics excepted) (Adams 1959, M~er-Mickelcit 1953). It may be concluded that the EEG findings in Parkinsonism are not specific and that they consist in a more or less evident slowing of the background rhythm. SUMMARY I. Among 100 EEGs in Parkinsonian patients 64 were normal and 36 abnormal. The abnormalities consisted in most cases (25) in a slight to moderate diffuse slow-wave activity. In another 7 patients this activity appeared only during hyperventUation. Localized or hemispherai mani. festations were found in 4 cases only. 2. The frequency distribution of the alpha rhythm in the normal records is markedly shifted to the left in coin. parison with control groups. 3. The EEG findings in Parkinsonism are not specific and consist in a more or less evident slowing of the alpha rhythm.

R~SUM~ R~SULTA'rsDe C'~eO DANSLE PARKImONmME l. Parmi 100 I~EG effectu6s sur des maladcs parkinsonlens, 64 sent normau; et 36 anormaux. Dans la plupart des cas (25) les anomalies prennent la forme d'une activit6 diffuse, 16#re ou modern, d'ondes lentes. Chez 7 malades, cette activit6 apparalt seulement pendent l'hyperventilalion. Chez 4 malades seulement, l'on trouve des manifestations Itgalis~.~s ou h6misph6riques, 2. Dana les I~EG normaux la distribution de la fNquence du rythme alpha montre un d~placement m a r q ~ vet's la ~auche en comparaisonav¢~ lea troupes des t~moh~s. 3. L'I~EGdu malade attaint de la maladie de Parkinson est non.sp~ifique ~'t r~v61e un ralentlssement, plus ou acing ~vldent, du rythme alpha, REFERENCES

ADAMS,A. Studies of the fiat EEG in Man. FAectroen~l~, olin. NeuropAyJ/ol., I ~ , II: 35-41. ENOLAND, A, C,, SctlwAa, R, S, AND PI~nSON, E. The EEO in Parkinson's syndrome, EIt~troencel~. din. Neurophyslol., 1959, II: 723--731. MBYER-MICKeLeiT, g. Das EEG nach gedeckten gopffer. letzungen. Dtscb. mad. Wschr., 1953, 78: 480-484. SCHWAU, R. S. ANO COBB, S. Simultaneous EMGs and EEGs in paralysis agitans, J. NeurOl~yslol., 19~, 2: 36-41, SCHWAS, R, S., ENOLAND,A, C, ANn I ~ M O N , E. Comparison of EEG Êindings in Parkinson's dis~N~ FAct,-

:roencel~,olin. Neuropky$1ol., 19S, I0: 186.

Re[erence: SmAKOV, A. A. and Mr,.AN, I. S. EEG findings in Parkinsonism. FJeetmencep&el~. Neumpl~a~., 1963, l~: 321-322.