- Email: [email protected]
sec vertex spindles
543
Electroencephalography and Clinical Neurophysiology, 1973, 34:543-546 © Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
CLINICAL
NOTE
4 c/sec VERTEX SPINDLES A. C. VAN HUFFELEN AND O . M A G N U S Research Unit T.N.O. for Clinical Neurophysiology, Wassenaar (The Netherlands) (Accepted for publication: November 10, 1972)
In 1966 one of us (O.M.) noticed an unusual phenomenon in some EEGs, consisting in short runs of rhythmic 4 c/sec triangular waves, located at the vertex. To ascertain whether this was a specific EEG phenomenon we recorded all EEGs which showed such runs during a period of 5 years. We have not been able to find any reference to this phenomenon in the literature.
",E~; ~" S~Is~.~:.
RC,l.=se¢.
HF<7OHz
J.M.A.v.E871) IS
MATERIAL A N D M E T H O D S In the laboratory of Clinical Neurophysiology of the Ursulakliniek approximately 13.000 EEGs have been recorded in the years 1966-1970 in neurological, neurosurgical and psychiatric in- and out-patients. The material of the present study consists of half of these EEGs (approx. 6,500) which have been evaluated by one of us (O.M.). There has been no special selection. All EEGs were recorded with conventional 16channel electroencephalographs. The electrode positions were according to the international 10-20 system. Recordings were made with short and long distance serial montages and with montages to a common average reference (GoldmanOffner). The vertex electrode (Cz) was incorporated in half of the standard montages. In all EEGs the effects of opening and closing of the eyes, hand movements, hyperventilation during at least 3 rain and intermittent photic stimulation were investigated. In patients with vegetative complaints (fainting, dizziness, hyperhidrosis, vascular headache) the influence of eyeball compression on cardiac frequency and EEG was usually examined. The clinical data concerning the patient were not known to the reporter at the moment of evaluation. The EEG phenomenon which we have studied consists of rhythmic waves at a frequency of 3.5-4.5 c/sec with amplitudes of 20-100 pV, with triangular wave form, localized at the vertex and occurring in runs of at least 1 sec, with waxing and waning amplitude. For practical reasons this phenomenon has been called 4 c/sec vertex spindles. If the EEG showed the phenomenon, the name, age, sex and provisional diagnosis of the patient were noted. In each EEG the number of times such spindles occurred, the average frequency and the average amplitude of the waves were measured. The conditions under which spindles occurred were noted. As the age distribution of the patients showing 4 c/sec vertex spindles proved to be very different from the age distri-
Fig. I. 4 c/sec vertex spindle. Average common reference (Ooldman-Offner). bution of the patients referred to our laboratory, out of the first 1,000 patients examined in 1970 a subgroup of 176 patients was formed, comprising all patients of ages between 12 and 21 years, which served as a control group. RESULTS The 4 c/sec vertex spindles were found in 20 patients out of the 6,500 (0.3 ~). Examples of the phenomenon are shown in Fig. 1 an~i 2. In the whole series of patients 133 spindles were found. The mean number of spindles for the whole series was 3.1 (S.D. 2.3) spindles per 10 rain recording time, counted in montages including electrode Cz. The mean duration of the spindles for the whole series was 2.5 (S.D. 0.4) sec. The mean frequency of this rhythmic activity was 3.9 (S.D. 0.3) c/sec and
544
A. C. VAN Ht;FFELEN AND O. MAGNUS
. . . . . . . . .
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~
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See.
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.
It z.
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.
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Fig. 2. 4 c/sec vertex spindle, bipolar montage, same patient as Fig. I.
its mean amplitude was 40/~V (S.D. 13), both for the whole series. In each single patient the spindles showed a fairly constant frequency. In 3 patients 2 or more EEGs have been recorded shortly after each other. All these EEGs showed the phenomenon. In 2 other patients EEGs had been recorded a few years earlier : in one patient 4 c/sec vertex spindles were found at the age of 16, but not at the age of 12, in another they were recorded at the age of 14 and not at the age of 12. In one other patient the spindles were only seen in 1 out of 5 records within a period of 1 year. Reactivity. As the phenomenon appeared only sporadically and as the spindles lasted only a short time, it was not possible to investigate systematically the reactivity to various kinds of stimuli. However, spindles were observed in the following conditions: eyes closed, eyes open, reading, photic stimulation, hand movements and during the first 0.5 min of hyperventilation. No spindles were encountered during drowsiness, sleep and after the first 0.5 min of hyperventilation. It should be noted that in the majority of EEGs the reaction to overbreathing was not so marked that it would have concealed the spindles. Location. The spindles were in nearly all instances strictly limited to the C~ position. In one patient there was occasionally some spread to F~, in another there was sporadically some spread to PzCharacteristics of the EEG. The EEGs at rest of all 20 patients were considered to be within the normal range. During hyperventilation in 2 patients bilaterally synchronous
spike and wave complexes have been observed. In one of these patients the diagnosis of epilepsy had been established. He had been treated by one of us (O.M.) for many years because of typical absences. 4 c/sec spindles were observed for the first time in his EEG at the age of 14 years. At that time he had been free from absences for several years, his EEG had not shown any spike and wave complexes and his medication had been discontinued. Age distribution. Seventeen out of 20 patients showing the phenomenon were between 12 and 21 years of age (Fig. 3). NO. O F PAT.
7~
4
12
14
16
18
20
22
24
26
28
56
58
[YEARS1
Fig. 3. Age distribution of the patients with 4 c/see vertex spindles.
4 c / s e c VERTEX SPINDLES
545
TABLE I The main diagnostic groups of patients and controls.
Epilepsy Concussion and seq. Psychiatric disorders Migraine Vasomotor instability, syncope Headache Other diagnoses
176 patients without spindles
17 patients with spindles
No.
No.
59 31 12 11 9
34 18 7 6 5
4 3 1 1
6
6
35
6 48
3 27
1 1
6 6
Therefore a control group of 176 patients within this age group was formed. The study group of 17 patients and the control group of 176 patients were compared for age distribution within this span, for sex and diagnosis. In the control group there was a homogenous distribution over 5 age groups of 2 years, varying between 18% and 21%. In the study group the distribution was very different, 47 ~ of cases being in the 14-15 years group. Sex distribution. In the two groups there was an equal distribution of the sexes. piagnosis. Table I shows the 7 main diagnostic groups for the study group and the control group. Sometimes these were provisional diagnoses in out-patients, in other cases they were diagnoses based on extensive clinical investigation. When comparing the two groups, the relatively large percentage (35 ~ ) of patients with ~asomotor instability in the vertex spindle group is striking. In the subgroup of patients of 14-15 years the proportion was the same (3 out of 8). Eyeball compression. This was performed in 9 out of 20 patients. In 3 cases it induced a cardiac arrest lasting more than 3 see, after which time the compression was terminated. In 2 patients there was an asystole of 2 see and in 4 cases there was no significant response. Medication. Eighteen patients received no medication; one patient had 30 mg of phenobarbitone and 60 mg of phenytoin daily and another patient 30 mg of trifluoperazinum daily. Association with frontal theta rhythm. In the EEGs of 6 out of 20 patients (30 %) 4 c/see vertex spindles were associated with a frontal theta rhythm of 6-7 c/sec, as described by Kellaway, cited by Dumermuth (1965) and Basecqs and Sorel (1966). DISCUSSION The 4 c/sec vertex spindles are easily recognizable because of their frequency, form and location. It is remarkable that nearly all of the EEGs in which this phenomenon was found were otherwise considered normal, which contrasts with the relatively high proportion of abnormal EEGs recorded in our laboratory. We do not have a large control group of healthy subjects. It is not impossible that this EEG pheno-
23 18 6
menon will be found in a certain proportion of healthy adolescents, particularly in the age group of 14 and 15 years. The preference of the 4 c/see vertex spindles for this age group in our clinical material is striking. The relationship between 4 c/see vertex spindles and vasomotor instability is suggested by the fact that the 3 patients who showed the spindles most markedly and abundantly were all referred because of vasomotor instability and by the data given in Table I. Determination of the statistical significance of these data was not possible because of the small numbers and differences in age distribution of the two groups. There was, however, no accumulation of patients with vasomotor instability in the age group of 14 and 15 years. Therefore we think that our data suggest the presence of a correlation between vasomotor instability and 4 c/see vertex spindles. The 4 c/see vertex spindles can be easily differentiated from the frontal theta rhythm at 6-7 c/see, as described by Kellaway, cited by Basecqs and Sorel (1966). This rhythm, which occurs in long runs, has its maximum at the F, position and increases during and after hyperventilation and during drowsiness, whereas the 4 c/see vertex spindles were not encountered in these conditions. It is remarkable that both theta rhythms occurred independently in the EEGs of 6 out of 20 patients (30 %), whereas Kense et al. (unpublished) found the frontal 6-7 c/see rhythm in only 15 ~ of the patients of a comparable age group in our laboratory.
SUMMARY An EEG phenomenon consisting of rhythmic 3.~4.5 c/see triangular waves with an average amplitude of 40/~V, strictly localized at the vertex, occurring in spindles with an average duration of 2.5 see has been observed in 20 patients. This phenomenon was called 4 c/see spindles. It occurred particularly in awake adolescents with a peak at the age of 14-15 years. The most common diagnosis under which they had been referred was vasomotor instability. The EEGs of 30 ~ of these patients moreover showed a frontal theta rhythm at 6-7 e/see. In 90 ~ of these patients the EEG was otherwise unremarkable.
546 RESUME FUSEAUX DE 4 c/sec AU VERTEX Un ph6nomene EEG consistant en ondes triangulaires rythmiques de 3,5 fi 4 c/sec et d'une amplitude moyenne de 40 txV, strictement localis6 au vertex, survenant en fuseaux avec une dur~e moyenne de 2,5 sec, a 8t~ observ6 chez 20 malades. Ce ph6nom~ne a ~t~ appel+ fuseaux de 4 c/sec au vertex. II survient tout particuli~rement chez des adolescents 6veill6s, montrant une predominance ~ l'gtge de 14 ~ 15 ans. Le diagnostic le plus habituel darts lequel ces 61+ments ont 6t6 observes est l'instabilit6 vaso-motrice. Les EEG de 30%
A. C. \'AN HUFFELEN AND O. MAGNUS de ces malades, en omre, monlrent un rythme theta frontal de 6 fi 7 c/sec. Chez 90'~41 d'entre eux, I'EEG n'a par ailleurs rien de remarquable.
REFERENCES
BASECQS,J. et SOREL L Signification des paroxysmes anterieurs formes d'ondes en trains 8 6 c/s. Acta neurol belq., 1966, 66:928 938. DUMERMUTH, J. Electroencephalographie im Kindesaller, Georg Thieme Verlag, Stuttgart, 1965.
Electroencephalography and Clinical Neurophysiology, 1973, 34:543-546 © Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
CLINICAL
NOTE
4 c/sec VERTEX SPINDLES A. C. VAN HUFFELEN AND O . M A G N U S Research Unit T.N.O. for Clinical Neurophysiology, Wassenaar (The Netherlands) (Accepted for publication: November 10, 1972)
In 1966 one of us (O.M.) noticed an unusual phenomenon in some EEGs, consisting in short runs of rhythmic 4 c/sec triangular waves, located at the vertex. To ascertain whether this was a specific EEG phenomenon we recorded all EEGs which showed such runs during a period of 5 years. We have not been able to find any reference to this phenomenon in the literature.
",E~; ~" S~Is~.~:.
RC,l.=se¢.
HF<7OHz
J.M.A.v.E871) IS
MATERIAL A N D M E T H O D S In the laboratory of Clinical Neurophysiology of the Ursulakliniek approximately 13.000 EEGs have been recorded in the years 1966-1970 in neurological, neurosurgical and psychiatric in- and out-patients. The material of the present study consists of half of these EEGs (approx. 6,500) which have been evaluated by one of us (O.M.). There has been no special selection. All EEGs were recorded with conventional 16channel electroencephalographs. The electrode positions were according to the international 10-20 system. Recordings were made with short and long distance serial montages and with montages to a common average reference (GoldmanOffner). The vertex electrode (Cz) was incorporated in half of the standard montages. In all EEGs the effects of opening and closing of the eyes, hand movements, hyperventilation during at least 3 rain and intermittent photic stimulation were investigated. In patients with vegetative complaints (fainting, dizziness, hyperhidrosis, vascular headache) the influence of eyeball compression on cardiac frequency and EEG was usually examined. The clinical data concerning the patient were not known to the reporter at the moment of evaluation. The EEG phenomenon which we have studied consists of rhythmic waves at a frequency of 3.5-4.5 c/sec with amplitudes of 20-100 pV, with triangular wave form, localized at the vertex and occurring in runs of at least 1 sec, with waxing and waning amplitude. For practical reasons this phenomenon has been called 4 c/sec vertex spindles. If the EEG showed the phenomenon, the name, age, sex and provisional diagnosis of the patient were noted. In each EEG the number of times such spindles occurred, the average frequency and the average amplitude of the waves were measured. The conditions under which spindles occurred were noted. As the age distribution of the patients showing 4 c/sec vertex spindles proved to be very different from the age distri-
Fig. I. 4 c/sec vertex spindle. Average common reference (Ooldman-Offner). bution of the patients referred to our laboratory, out of the first 1,000 patients examined in 1970 a subgroup of 176 patients was formed, comprising all patients of ages between 12 and 21 years, which served as a control group. RESULTS The 4 c/sec vertex spindles were found in 20 patients out of the 6,500 (0.3 ~). Examples of the phenomenon are shown in Fig. 1 an~i 2. In the whole series of patients 133 spindles were found. The mean number of spindles for the whole series was 3.1 (S.D. 2.3) spindles per 10 rain recording time, counted in montages including electrode Cz. The mean duration of the spindles for the whole series was 2.5 (S.D. 0.4) sec. The mean frequency of this rhythmic activity was 3.9 (S.D. 0.3) c/sec and
544
A. C. VAN Ht;FFELEN AND O. MAGNUS
. . . . . . . . .
-~~vl
/
~
RIC;,,t,Z
I SOC
•
See.
. ,~.. HF. O ~ ,,
.
It z.
.
.
~ .,x.~,"
.
.-
c
~.
.
E.C.
.
.
.
,,
~
.
.
,
.
J.M.A v. E. l i -
¢'
;
^
.
.
.
.
-lit O U
.
.
.
";.\
Fig. 2. 4 c/sec vertex spindle, bipolar montage, same patient as Fig. I.
its mean amplitude was 40/~V (S.D. 13), both for the whole series. In each single patient the spindles showed a fairly constant frequency. In 3 patients 2 or more EEGs have been recorded shortly after each other. All these EEGs showed the phenomenon. In 2 other patients EEGs had been recorded a few years earlier : in one patient 4 c/sec vertex spindles were found at the age of 16, but not at the age of 12, in another they were recorded at the age of 14 and not at the age of 12. In one other patient the spindles were only seen in 1 out of 5 records within a period of 1 year. Reactivity. As the phenomenon appeared only sporadically and as the spindles lasted only a short time, it was not possible to investigate systematically the reactivity to various kinds of stimuli. However, spindles were observed in the following conditions: eyes closed, eyes open, reading, photic stimulation, hand movements and during the first 0.5 min of hyperventilation. No spindles were encountered during drowsiness, sleep and after the first 0.5 min of hyperventilation. It should be noted that in the majority of EEGs the reaction to overbreathing was not so marked that it would have concealed the spindles. Location. The spindles were in nearly all instances strictly limited to the C~ position. In one patient there was occasionally some spread to F~, in another there was sporadically some spread to PzCharacteristics of the EEG. The EEGs at rest of all 20 patients were considered to be within the normal range. During hyperventilation in 2 patients bilaterally synchronous
spike and wave complexes have been observed. In one of these patients the diagnosis of epilepsy had been established. He had been treated by one of us (O.M.) for many years because of typical absences. 4 c/sec spindles were observed for the first time in his EEG at the age of 14 years. At that time he had been free from absences for several years, his EEG had not shown any spike and wave complexes and his medication had been discontinued. Age distribution. Seventeen out of 20 patients showing the phenomenon were between 12 and 21 years of age (Fig. 3). NO. O F PAT.
7~
4
12
14
16
18
20
22
24
26
28
56
58
[YEARS1
Fig. 3. Age distribution of the patients with 4 c/see vertex spindles.
4 c / s e c VERTEX SPINDLES
545
TABLE I The main diagnostic groups of patients and controls.
Epilepsy Concussion and seq. Psychiatric disorders Migraine Vasomotor instability, syncope Headache Other diagnoses
176 patients without spindles
17 patients with spindles
No.
No.
59 31 12 11 9
34 18 7 6 5
4 3 1 1
6
6
35
6 48
3 27
1 1
6 6
Therefore a control group of 176 patients within this age group was formed. The study group of 17 patients and the control group of 176 patients were compared for age distribution within this span, for sex and diagnosis. In the control group there was a homogenous distribution over 5 age groups of 2 years, varying between 18% and 21%. In the study group the distribution was very different, 47 ~ of cases being in the 14-15 years group. Sex distribution. In the two groups there was an equal distribution of the sexes. piagnosis. Table I shows the 7 main diagnostic groups for the study group and the control group. Sometimes these were provisional diagnoses in out-patients, in other cases they were diagnoses based on extensive clinical investigation. When comparing the two groups, the relatively large percentage (35 ~ ) of patients with ~asomotor instability in the vertex spindle group is striking. In the subgroup of patients of 14-15 years the proportion was the same (3 out of 8). Eyeball compression. This was performed in 9 out of 20 patients. In 3 cases it induced a cardiac arrest lasting more than 3 see, after which time the compression was terminated. In 2 patients there was an asystole of 2 see and in 4 cases there was no significant response. Medication. Eighteen patients received no medication; one patient had 30 mg of phenobarbitone and 60 mg of phenytoin daily and another patient 30 mg of trifluoperazinum daily. Association with frontal theta rhythm. In the EEGs of 6 out of 20 patients (30 %) 4 c/see vertex spindles were associated with a frontal theta rhythm of 6-7 c/sec, as described by Kellaway, cited by Dumermuth (1965) and Basecqs and Sorel (1966). DISCUSSION The 4 c/sec vertex spindles are easily recognizable because of their frequency, form and location. It is remarkable that nearly all of the EEGs in which this phenomenon was found were otherwise considered normal, which contrasts with the relatively high proportion of abnormal EEGs recorded in our laboratory. We do not have a large control group of healthy subjects. It is not impossible that this EEG pheno-
23 18 6
menon will be found in a certain proportion of healthy adolescents, particularly in the age group of 14 and 15 years. The preference of the 4 c/see vertex spindles for this age group in our clinical material is striking. The relationship between 4 c/see vertex spindles and vasomotor instability is suggested by the fact that the 3 patients who showed the spindles most markedly and abundantly were all referred because of vasomotor instability and by the data given in Table I. Determination of the statistical significance of these data was not possible because of the small numbers and differences in age distribution of the two groups. There was, however, no accumulation of patients with vasomotor instability in the age group of 14 and 15 years. Therefore we think that our data suggest the presence of a correlation between vasomotor instability and 4 c/see vertex spindles. The 4 c/see vertex spindles can be easily differentiated from the frontal theta rhythm at 6-7 c/see, as described by Kellaway, cited by Basecqs and Sorel (1966). This rhythm, which occurs in long runs, has its maximum at the F, position and increases during and after hyperventilation and during drowsiness, whereas the 4 c/see vertex spindles were not encountered in these conditions. It is remarkable that both theta rhythms occurred independently in the EEGs of 6 out of 20 patients (30 %), whereas Kense et al. (unpublished) found the frontal 6-7 c/see rhythm in only 15 ~ of the patients of a comparable age group in our laboratory.
SUMMARY An EEG phenomenon consisting of rhythmic 3.~4.5 c/see triangular waves with an average amplitude of 40/~V, strictly localized at the vertex, occurring in spindles with an average duration of 2.5 see has been observed in 20 patients. This phenomenon was called 4 c/see spindles. It occurred particularly in awake adolescents with a peak at the age of 14-15 years. The most common diagnosis under which they had been referred was vasomotor instability. The EEGs of 30 ~ of these patients moreover showed a frontal theta rhythm at 6-7 e/see. In 90 ~ of these patients the EEG was otherwise unremarkable.
546 RESUME FUSEAUX DE 4 c/sec AU VERTEX Un ph6nomene EEG consistant en ondes triangulaires rythmiques de 3,5 fi 4 c/sec et d'une amplitude moyenne de 40 txV, strictement localis6 au vertex, survenant en fuseaux avec une dur~e moyenne de 2,5 sec, a 8t~ observ6 chez 20 malades. Ce ph6nom~ne a ~t~ appel+ fuseaux de 4 c/sec au vertex. II survient tout particuli~rement chez des adolescents 6veill6s, montrant une predominance ~ l'gtge de 14 ~ 15 ans. Le diagnostic le plus habituel darts lequel ces 61+ments ont 6t6 observes est l'instabilit6 vaso-motrice. Les EEG de 30%
A. C. \'AN HUFFELEN AND O. MAGNUS de ces malades, en omre, monlrent un rythme theta frontal de 6 fi 7 c/sec. Chez 90'~41 d'entre eux, I'EEG n'a par ailleurs rien de remarquable.
REFERENCES
BASECQS,J. et SOREL L Signification des paroxysmes anterieurs formes d'ondes en trains 8 6 c/s. Acta neurol belq., 1966, 66:928 938. DUMERMUTH, J. Electroencephalographie im Kindesaller, Georg Thieme Verlag, Stuttgart, 1965.