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Clinical correlates of the spike-wave complex
CLINICAL CORRELATES OF THE SPIKE-WAVE COMPLEX 1 DANIEL SILVERMAN, M . D .
W i t h the technical assistance of THEDA SANNIT, B.S. Department of Neurology, Graduate School of Medicine, C~aduate Hospital, University o~ Pennsylvania, Philadelphia, Pa. (Received for publieation: May 28, 1954)
Since the first descriptions of the spikewave electrical patterns identified by Gibbs et al., as petit real (1935) and petit real variant (1939) epilepsy, there has been disagreement in the literature (Jasper and Kershman 1941; Finley and Dynes 1942; Echlin 1944, and others) about their clinical significance. As a contribution to this problem, 2,000 consecutive E E G records taken between 1952 and 1954 at the Graduate Hospital Electroencephalographic Laboratory were reviewed for the presence of spike-wave formations. Metrazol and Metrazol-photie activations of spike-wave complexes were excluded, since positive responses are more likely to be elicited by these procedures in nonepileptic individuals (Buehthal and Lennox 1953 ; Leiberman et al. 1954). Clinical data were gathered from the hospital charts and/or referring physicians, since about 45 per cent of the tracings were done on out-patients. The clinical diagnostic breakdown of the 2,000 records was as follows: epilepsies 25 per cent, functional psychiatric disorders 18 per cent, brain tumors and brain tumor suspects 15 per cent, cerebrovascular disorders 12 per cent, post-traumatic encephalopathies 10 per cent, cerebral degenerative diseases 8 per cent, and miscellaneous central nervous system diseases 12 per cent. Out of this group of 2,000 records, spike-wave abnormalities were encountered in 121, representing 114 patients. It was obvious on reviewing the EEGs ~hat there are important electrical differences in spike-wave formations and hence an attempt was made to reclassify them. Three broad groups are to be described. I. Classical
3 per sec. spike-wave ; this is the familiar bilaterally synchronous, mirror image, well-regulated paroxysmal 3 per see. rhythm which in the longer bursts is ~often accompanied by a clinical petit real seizure. There were 24 patients with this type of dysfunction (fig. 1). II. Generalized spike-wave formations, but not "classical" in type ; these are further separated into three subdivisions: (a) Marked variation of the spike-wave frequency; this group is closest to the "classical" and contained 11 patients (fig. 2). (b) Multiple spikes and slow wave; the spikes are usually rapid, but at times, particularly during sleep, are slow; there were 26 patients in this category (fig. 3). (c) Slow spike-wave; this corresponds to the non-focal "petit real variant" of Gibbs and in our series there were 11 patients (fig. 4). III. Focal spike-wave formations, which can be subdivided into three groups: (a) Bilaterally synchronous, but restricted to one bilateral area, most often the frontal; these are most likely focal with a mirror focus, e.g., the spike might be faster, or higher in amplitude on one side, but a clear-cut laterality could not be established; 8 such patients were in this group (fig. 5). (b) Focal spike-waves, localized to a relatively small area; these are often slow-pike formations, similar to the Gibbs' focal "petit real variant"; 19 patients belonged to this category (fig. 6). (c) Focal spike-waves with generalized spread; often the pattern is multiple spike-wave, but the focal nature of the discharge is unquestionable; there were 15 such cases (fig. 7). It must be added that the spike-waves were the only abnormalities considered in the above 1 PreBented at the March 1954 meeting of the classification, even though other abnormalities were often present in the records; almost alEastern Association of Eleetroeneephalographers. [ ~63 ]
664
DANIEL SILVERMAN
LF-LE
~
6roup
~ ;
~ ri
I - CLASSICAL
(Hypervent
i l~ti
on)
~ ~
Fig. I
Fig.
2
66g
CORRELATES OF THE SPIKE-WAVE COMPLEX ~.,~,,RT-R
,,m~e.M~.
.
Broup l i B -
MULTIPLE SPIKE-I/AVE
(Photi©
RF- V:"
.
A o t i v a t i on)
"t
photo~
~.oo,~
I
5Our
Fig. 3
L~-~F ' ~
~ ~
~ ~
I souv
/
~
RF-RT
RP-RF
,
Fig. 4
~/~
666
DANIEL SILVERMAN
RF-RM
f\
RP-RO
Group I l l
A - BILATERAL FOCAL SPIKE-WAVE
I.M-LP
1 second
~T50 uV
Fig. 5
ways, however, the spike-wave was the most significant feature in the interpretation. At times, a focal spike-wave discharge became generalized; in this case the E E G was recorded as focal. In the multiple spike-wave category there were often single spike-wave dis-
charges; the classification, however, was considered multiple spike-wave. The most striking clinical finding in the spike-wave groups is that all but three patients at the time of the test had histories of seizures of some type; these exceptions were young
VbT'LTI LT-L.Post,T.~ L Post T
/~.
LO~
I ~ ]~_ _ ^ ....
Broup
A~.~ III
.~ ~ ~ ^AA ._ A
R. P o o t . T . - R O
~
~ m
~ t
~ ~sscond ~
,I.,~R'P°st'T"V V.-L.Post,T
t,/ Fig. 6
_ .^
B - FOCAL SPIKE-WAVE
(Sleep l c t i v i l i o n - P o s t e r i o r
T
n
Temporal
50 uV
Focus)
667
CORRELATES OF THE SPIKE-WAVE COMPLEX children - - one a two y e a r old mentally ret a r d e d girl ( E E G group I I I b) and the other two, a 5 y e a r old behavior problem boy ( E E G g r o u p I I c) and a 7 y e a r old behavior problem boy ( E E G g r o u p I I a). I t is entirely
Stoup
III
A s t u d y of seizure p a t t e r n s in relation to E E G types (table I ) yields some significant information. G r a n d real (which here:includes brief tonic seizures and the few cases of m y o clonic seizures who also h a d g r a n d real sei-
C - FOCAL SPIKE WAVE
LT- V
RP V"
1 second
~ 50 uV
Fig. 7
possible t h a t these patients m a y develop seizures at an older age. F r o m this it m a y be i n f e r r e d t h a t spike-wave formations of whatever v a r i e t y point clinically toward epileptic phenomena, a conclusion reached some years ago b y Finley (1942).
zures) is the most frequent seizure encountered, 66 per cent; next is petit real (which includes akinetic seizures), 26 per cent. Only in the " c l a s s i c a l " spike-waves did petit real predominate as the seizure t y p e ; thus the " c l a s s i c a l " p a t t e r n more often indicates petit
TABLE I EEG CLASSIFICATION AND TYPES OF SEIZURES EEG groups
0
No seizures 0
(11) (26) (11)
6 21 6
1 1 1
4 1 3
0 2 0
0 1 0
0 0 0
1 0 1
I I I (42) a ( 8 ) b (19)
6 10
0 1
1 0
0 3
0 2
1 2
0 1
(16)
6
0
2
0
0
7
0
(114)
60
16
16
6
6
10
3
I
(24)
Ii
(48)
a b ¢
c
TOTALS
Grand mal 6
Petit mal 11
GMand Automatisms GMand PM Aut. 4 1 2
Jacksonian
~68
DANIEL SILVERMAN
real seizures, but by no means exclusively. The f u r t h e r the variation from the "clas:sical", the less likely are petit mal phenomena to be found. The generalized multiple spikewave pattern correlates closely with grand mal seizures. There are too few cases in the series to make a detailed study of the age factor. The .youngest patient was 8 months old (a case of brief tonic seizures and probably petit mal :spells, electrically in group I I I c, corresponding to Gibbs' hypsarhythmia) ; the oldest was 58 (a patient with grand mal seizures since .age 13, whose E E G was in class I I b ) . The majority were in the younger age groups: 48 under age 11, 29 between l l and 18, 31 be-
tally retarded, 2 behavior problems and 2 with organic eonfusional syndromes). For etiologic factors in group II, trauma was implicated in 6, birth i n j u r y in 3 and encephalitis in 4; in group lI[, trauma was implicated in 4, birth i n j u r y in 2, operative damag~ (for cyst of 3rd ventricle) in 1, verified braik~ tumors in 2, unverified tumor in l, encephalitis in 5, presenile psychosis (degenerativei in 1 and brain abscess cicatrix in 2. These data tend to support the thesis ot~ Jasper (1954) that the " c l a s s i c a l " 3 per sec. spike-wave, group 1, is usually " i d i o p a t h i c " in origin and represents a " c e n t r e n c e p h a l i c " dysrhythmia as opposed to the strictly cortimbal seizures and spike-waves, group IlI,
TABLE II ACTIVATION RESULTS B -- ADI)ITIONA L
A -- CRUCIAL EEG groups I II
(24) (48)
(42)
TOTALS
Photic
13 1 4
8 3 4
6 1 6
0
0 1 4 1
4 4 10 6
2 1 ] 0
7
~°4
39
17
Sleep
Photic
More t h a n one
5 0 1
4 3 3
0 2 7
H - P (1) H-S (2) H - P (1)
o
2
o
s-P (2) H-s (1)
0
2
1
0
b (19)
1
2
o
o
e
2
5
1
9
21
11
a b
(11) (26)
e (11) III
Sleep
tIyperventilation
a
(8) (15)
tween 19 and 45, and 6 over 45. The youngest patient with the " c l a s s i c a l " p a t t e r n was 32 months old - - this is in keeping with the find~ng of Kellaway (1954). Females were more prevalent than males, 61 to 53. In groups I and II, the preponderance was more marked: 43 to 29; in group I I I the ratio was reversed: 18 females to 24 males. Group I was singularly free of neurologic defect, psychiatric disturbances or known etiologic factors; in only two was there a questionable element of brain trauma. Group II had a moderate number with neurologic defect (5) and psychiatric disorder (3 behavior problems and one mentally r e t a r d e d ) ; while group I I I had the most with neurologic defect (9) and psychiatric difficulties (2 men-
Hyperventilation
which have their origin in focal cortical pathology. The other generalized spike-waves, group II, lie somewhat in between, or may represent mixed types. Mention must be made of activation procedures. U n f o r t u n a t e l y we do not have absolute comparisons, as reason dictates either sparing the patient or the technician's time when either the resting record or one activation procedure gives unequivocal results. Insofar as practicable, we tried to use all the activation procedures listed; nevertheless, ~ayperventilation was omitted 29 times (mostly with infants), photic stimulation 34 and sleep 12 times. Table II-A lists the cases in which activation alone elicited the spike-wave complexes; table II-B lists the times in which
CORRELATES OF THE SPIKE-WAVE COMPLEX
an activation procedure in addition to the resting record b r o u g h t out more clearly the spike-wave abnormalities. The " c l a s s i c a l " spike-wave responds best to hyperventilation activation, the multiple spike-wave to photic, while sleep is u n i f o r m l y effective, most revealing in the focal spike-wave complexes. W h e n e v e r used, sleep was 65 per cent, hyperventilation 45 per cent, and photic stimulation 40 per cent effective in this series; the overall percentage of eliciting spike-wave complexes was increased 42 per cent by the use of activation. These results emphasize the unmistakable value of activation techniques in the E E G investigation of the epilepsies. SUMMARY Out of 2,000 consecutive E E G s of neurologic patients, 121 (or 114 patients) had spike-wave complexes. Clinically, the spikewave complex is practically diagnostic of epileptic phenomena. Spike-wave complexes are divided into the " c l a s s i c a l " type, which correlates best but not exclusively with petit real epilepsy; other generalized spike-wave d y s r h y t h m i a s of which the multiple spikewave corresponds most closely to g r a n d real epilepsy; and focal spike-wave, in which group focal seizures are more frequently
669
found. K n o w n etiologic factors a n d positive neurologic signs are r a r e in the " c l a s s i c a l " spike-wave group and common in the focal spike-waves. Activation techniques are import a n t in eliciting spike-wave complexes. REFERENCES BUCHTHAL, F. and LENNOX, M. The EEG effect of
Metrazol and photic stimulation in 682 normal subjects. EEG Clin. Neurophysiol., 1953, 5: 545558. EOHLIN, F. A. The electroencephalogram associated with epilepsy. Arch. Neurol. Psychiat., Chicago, 1944, 52: 270-289. FINLEY, K. H. and DYNES, J. G. Eleetroencephalographic studies in epilepsy. Brain, 1942, 65:
256-265. GIBBS, F., DAVIS, H. and LENNOX,W. G. The electroencephalogram in epilepsy and in conditions of impaired consciousness. Arch. Neurol. Psychiat., Chicago, 1985, 34: 1133-1148. GIBBS, F., GXBBS,E. and LENNOX,W. G. The influence of the blood sugar level on the wave and spike formation in petit real epilepsy. Arch. Neurol. Psychiat., Chicago, 1989, 41 : 1111-1116.
JASPER, H. and KERSHMAN, J.
Electroencephalo-
graphic classification of the epilepsies. Arch. Neurol. Psychiat., Chicago, 1941, 45: 903-943. KELLAWAY, P. E. C. The ontogenesis of the spike and wave formation in man. Presented at the March 1954 meeting of the Eastern EEG Assoc. LEIBERMAN, D. M., HOENIG, J. and HACKER, M.
Metrazol-flieker threshold in neuropsychiatrie patients. BEG Clin. Neurophysiol., 1954, 6: 9-18. PENFIELD, W. and JASPER, H. "Epilepsy and the Functional Anatomy of the Human Brain." Boston, Little, Brown and Co., 19f¢1, 622 pp.
Reference: SILVEEMAlq,D. ~inleal correlates of the spike-wave complex. BEO Clin. Neerophysiol., 1954, 6: 663-669.
4
W i t h the technical assistance of THEDA SANNIT, B.S. Department of Neurology, Graduate School of Medicine, C~aduate Hospital, University o~ Pennsylvania, Philadelphia, Pa. (Received for publieation: May 28, 1954)
Since the first descriptions of the spikewave electrical patterns identified by Gibbs et al., as petit real (1935) and petit real variant (1939) epilepsy, there has been disagreement in the literature (Jasper and Kershman 1941; Finley and Dynes 1942; Echlin 1944, and others) about their clinical significance. As a contribution to this problem, 2,000 consecutive E E G records taken between 1952 and 1954 at the Graduate Hospital Electroencephalographic Laboratory were reviewed for the presence of spike-wave formations. Metrazol and Metrazol-photie activations of spike-wave complexes were excluded, since positive responses are more likely to be elicited by these procedures in nonepileptic individuals (Buehthal and Lennox 1953 ; Leiberman et al. 1954). Clinical data were gathered from the hospital charts and/or referring physicians, since about 45 per cent of the tracings were done on out-patients. The clinical diagnostic breakdown of the 2,000 records was as follows: epilepsies 25 per cent, functional psychiatric disorders 18 per cent, brain tumors and brain tumor suspects 15 per cent, cerebrovascular disorders 12 per cent, post-traumatic encephalopathies 10 per cent, cerebral degenerative diseases 8 per cent, and miscellaneous central nervous system diseases 12 per cent. Out of this group of 2,000 records, spike-wave abnormalities were encountered in 121, representing 114 patients. It was obvious on reviewing the EEGs ~hat there are important electrical differences in spike-wave formations and hence an attempt was made to reclassify them. Three broad groups are to be described. I. Classical
3 per sec. spike-wave ; this is the familiar bilaterally synchronous, mirror image, well-regulated paroxysmal 3 per see. rhythm which in the longer bursts is ~often accompanied by a clinical petit real seizure. There were 24 patients with this type of dysfunction (fig. 1). II. Generalized spike-wave formations, but not "classical" in type ; these are further separated into three subdivisions: (a) Marked variation of the spike-wave frequency; this group is closest to the "classical" and contained 11 patients (fig. 2). (b) Multiple spikes and slow wave; the spikes are usually rapid, but at times, particularly during sleep, are slow; there were 26 patients in this category (fig. 3). (c) Slow spike-wave; this corresponds to the non-focal "petit real variant" of Gibbs and in our series there were 11 patients (fig. 4). III. Focal spike-wave formations, which can be subdivided into three groups: (a) Bilaterally synchronous, but restricted to one bilateral area, most often the frontal; these are most likely focal with a mirror focus, e.g., the spike might be faster, or higher in amplitude on one side, but a clear-cut laterality could not be established; 8 such patients were in this group (fig. 5). (b) Focal spike-waves, localized to a relatively small area; these are often slow-pike formations, similar to the Gibbs' focal "petit real variant"; 19 patients belonged to this category (fig. 6). (c) Focal spike-waves with generalized spread; often the pattern is multiple spike-wave, but the focal nature of the discharge is unquestionable; there were 15 such cases (fig. 7). It must be added that the spike-waves were the only abnormalities considered in the above 1 PreBented at the March 1954 meeting of the classification, even though other abnormalities were often present in the records; almost alEastern Association of Eleetroeneephalographers. [ ~63 ]
664
DANIEL SILVERMAN
LF-LE
~
6roup
~ ;
~ ri
I - CLASSICAL
(Hypervent
i l~ti
on)
~ ~
Fig. I
Fig.
2
66g
CORRELATES OF THE SPIKE-WAVE COMPLEX ~.,~,,RT-R
,,m~e.M~.
.
Broup l i B -
MULTIPLE SPIKE-I/AVE
(Photi©
RF- V:"
.
A o t i v a t i on)
"t
photo~
~.oo,~
I
5Our
Fig. 3
L~-~F ' ~
~ ~
~ ~
I souv
/
~
RF-RT
RP-RF
,
Fig. 4
~/~
666
DANIEL SILVERMAN
RF-RM
f\
RP-RO
Group I l l
A - BILATERAL FOCAL SPIKE-WAVE
I.M-LP
1 second
~T50 uV
Fig. 5
ways, however, the spike-wave was the most significant feature in the interpretation. At times, a focal spike-wave discharge became generalized; in this case the E E G was recorded as focal. In the multiple spike-wave category there were often single spike-wave dis-
charges; the classification, however, was considered multiple spike-wave. The most striking clinical finding in the spike-wave groups is that all but three patients at the time of the test had histories of seizures of some type; these exceptions were young
VbT'LTI LT-L.Post,T.~ L Post T
/~.
LO~
I ~ ]~_ _ ^ ....
Broup
A~.~ III
.~ ~ ~ ^AA ._ A
R. P o o t . T . - R O
~
~ m
~ t
~ ~sscond ~
,I.,~R'P°st'T"V V.-L.Post,T
t,/ Fig. 6
_ .^
B - FOCAL SPIKE-WAVE
(Sleep l c t i v i l i o n - P o s t e r i o r
T
n
Temporal
50 uV
Focus)
667
CORRELATES OF THE SPIKE-WAVE COMPLEX children - - one a two y e a r old mentally ret a r d e d girl ( E E G group I I I b) and the other two, a 5 y e a r old behavior problem boy ( E E G g r o u p I I c) and a 7 y e a r old behavior problem boy ( E E G g r o u p I I a). I t is entirely
Stoup
III
A s t u d y of seizure p a t t e r n s in relation to E E G types (table I ) yields some significant information. G r a n d real (which here:includes brief tonic seizures and the few cases of m y o clonic seizures who also h a d g r a n d real sei-
C - FOCAL SPIKE WAVE
LT- V
RP V"
1 second
~ 50 uV
Fig. 7
possible t h a t these patients m a y develop seizures at an older age. F r o m this it m a y be i n f e r r e d t h a t spike-wave formations of whatever v a r i e t y point clinically toward epileptic phenomena, a conclusion reached some years ago b y Finley (1942).
zures) is the most frequent seizure encountered, 66 per cent; next is petit real (which includes akinetic seizures), 26 per cent. Only in the " c l a s s i c a l " spike-waves did petit real predominate as the seizure t y p e ; thus the " c l a s s i c a l " p a t t e r n more often indicates petit
TABLE I EEG CLASSIFICATION AND TYPES OF SEIZURES EEG groups
0
No seizures 0
(11) (26) (11)
6 21 6
1 1 1
4 1 3
0 2 0
0 1 0
0 0 0
1 0 1
I I I (42) a ( 8 ) b (19)
6 10
0 1
1 0
0 3
0 2
1 2
0 1
(16)
6
0
2
0
0
7
0
(114)
60
16
16
6
6
10
3
I
(24)
Ii
(48)
a b ¢
c
TOTALS
Grand mal 6
Petit mal 11
GMand Automatisms GMand PM Aut. 4 1 2
Jacksonian
~68
DANIEL SILVERMAN
real seizures, but by no means exclusively. The f u r t h e r the variation from the "clas:sical", the less likely are petit mal phenomena to be found. The generalized multiple spikewave pattern correlates closely with grand mal seizures. There are too few cases in the series to make a detailed study of the age factor. The .youngest patient was 8 months old (a case of brief tonic seizures and probably petit mal :spells, electrically in group I I I c, corresponding to Gibbs' hypsarhythmia) ; the oldest was 58 (a patient with grand mal seizures since .age 13, whose E E G was in class I I b ) . The majority were in the younger age groups: 48 under age 11, 29 between l l and 18, 31 be-
tally retarded, 2 behavior problems and 2 with organic eonfusional syndromes). For etiologic factors in group II, trauma was implicated in 6, birth i n j u r y in 3 and encephalitis in 4; in group lI[, trauma was implicated in 4, birth i n j u r y in 2, operative damag~ (for cyst of 3rd ventricle) in 1, verified braik~ tumors in 2, unverified tumor in l, encephalitis in 5, presenile psychosis (degenerativei in 1 and brain abscess cicatrix in 2. These data tend to support the thesis ot~ Jasper (1954) that the " c l a s s i c a l " 3 per sec. spike-wave, group 1, is usually " i d i o p a t h i c " in origin and represents a " c e n t r e n c e p h a l i c " dysrhythmia as opposed to the strictly cortimbal seizures and spike-waves, group IlI,
TABLE II ACTIVATION RESULTS B -- ADI)ITIONA L
A -- CRUCIAL EEG groups I II
(24) (48)
(42)
TOTALS
Photic
13 1 4
8 3 4
6 1 6
0
0 1 4 1
4 4 10 6
2 1 ] 0
7
~°4
39
17
Sleep
Photic
More t h a n one
5 0 1
4 3 3
0 2 7
H - P (1) H-S (2) H - P (1)
o
2
o
s-P (2) H-s (1)
0
2
1
0
b (19)
1
2
o
o
e
2
5
1
9
21
11
a b
(11) (26)
e (11) III
Sleep
tIyperventilation
a
(8) (15)
tween 19 and 45, and 6 over 45. The youngest patient with the " c l a s s i c a l " p a t t e r n was 32 months old - - this is in keeping with the find~ng of Kellaway (1954). Females were more prevalent than males, 61 to 53. In groups I and II, the preponderance was more marked: 43 to 29; in group I I I the ratio was reversed: 18 females to 24 males. Group I was singularly free of neurologic defect, psychiatric disturbances or known etiologic factors; in only two was there a questionable element of brain trauma. Group II had a moderate number with neurologic defect (5) and psychiatric disorder (3 behavior problems and one mentally r e t a r d e d ) ; while group I I I had the most with neurologic defect (9) and psychiatric difficulties (2 men-
Hyperventilation
which have their origin in focal cortical pathology. The other generalized spike-waves, group II, lie somewhat in between, or may represent mixed types. Mention must be made of activation procedures. U n f o r t u n a t e l y we do not have absolute comparisons, as reason dictates either sparing the patient or the technician's time when either the resting record or one activation procedure gives unequivocal results. Insofar as practicable, we tried to use all the activation procedures listed; nevertheless, ~ayperventilation was omitted 29 times (mostly with infants), photic stimulation 34 and sleep 12 times. Table II-A lists the cases in which activation alone elicited the spike-wave complexes; table II-B lists the times in which
CORRELATES OF THE SPIKE-WAVE COMPLEX
an activation procedure in addition to the resting record b r o u g h t out more clearly the spike-wave abnormalities. The " c l a s s i c a l " spike-wave responds best to hyperventilation activation, the multiple spike-wave to photic, while sleep is u n i f o r m l y effective, most revealing in the focal spike-wave complexes. W h e n e v e r used, sleep was 65 per cent, hyperventilation 45 per cent, and photic stimulation 40 per cent effective in this series; the overall percentage of eliciting spike-wave complexes was increased 42 per cent by the use of activation. These results emphasize the unmistakable value of activation techniques in the E E G investigation of the epilepsies. SUMMARY Out of 2,000 consecutive E E G s of neurologic patients, 121 (or 114 patients) had spike-wave complexes. Clinically, the spikewave complex is practically diagnostic of epileptic phenomena. Spike-wave complexes are divided into the " c l a s s i c a l " type, which correlates best but not exclusively with petit real epilepsy; other generalized spike-wave d y s r h y t h m i a s of which the multiple spikewave corresponds most closely to g r a n d real epilepsy; and focal spike-wave, in which group focal seizures are more frequently
669
found. K n o w n etiologic factors a n d positive neurologic signs are r a r e in the " c l a s s i c a l " spike-wave group and common in the focal spike-waves. Activation techniques are import a n t in eliciting spike-wave complexes. REFERENCES BUCHTHAL, F. and LENNOX, M. The EEG effect of
Metrazol and photic stimulation in 682 normal subjects. EEG Clin. Neurophysiol., 1953, 5: 545558. EOHLIN, F. A. The electroencephalogram associated with epilepsy. Arch. Neurol. Psychiat., Chicago, 1944, 52: 270-289. FINLEY, K. H. and DYNES, J. G. Eleetroencephalographic studies in epilepsy. Brain, 1942, 65:
256-265. GIBBS, F., DAVIS, H. and LENNOX,W. G. The electroencephalogram in epilepsy and in conditions of impaired consciousness. Arch. Neurol. Psychiat., Chicago, 1985, 34: 1133-1148. GIBBS, F., GXBBS,E. and LENNOX,W. G. The influence of the blood sugar level on the wave and spike formation in petit real epilepsy. Arch. Neurol. Psychiat., Chicago, 1989, 41 : 1111-1116.
JASPER, H. and KERSHMAN, J.
Electroencephalo-
graphic classification of the epilepsies. Arch. Neurol. Psychiat., Chicago, 1941, 45: 903-943. KELLAWAY, P. E. C. The ontogenesis of the spike and wave formation in man. Presented at the March 1954 meeting of the Eastern EEG Assoc. LEIBERMAN, D. M., HOENIG, J. and HACKER, M.
Metrazol-flieker threshold in neuropsychiatrie patients. BEG Clin. Neurophysiol., 1954, 6: 9-18. PENFIELD, W. and JASPER, H. "Epilepsy and the Functional Anatomy of the Human Brain." Boston, Little, Brown and Co., 19f¢1, 622 pp.
Reference: SILVEEMAlq,D. ~inleal correlates of the spike-wave complex. BEO Clin. Neerophysiol., 1954, 6: 663-669.
4