Primary generalised epileptic myoclonus: a frequent manifestation of minipolymyoclonus of central origin.

Abstract

SUMMARY A group of patients with myoclonus is described whose jerks are preceded by a bilaterally synchronous, frontocentrally predominant, negative cerebral potential in the EEG. This potential may be a slow wave with variable timing in relation to EMG bursts, and in this circumstance the muscle jerks are usually small amplitude and multifocal ("minipolymyoclonus"). The cerebral negativity can also be shorter in duration and time-locked to limb jerks, which are larger in amplitude and more widespread. We propose that the physiology of this distinct form of myoclonus is similar to that of primary generalised epilepsy.Myoclonus has been recognised in association with bilaterally synchronous discharges as recorded by scalp EEG. These paroxysmal discharges may assume a variety of forms: the regular 3 Hz spikewave activity of classic petit mal;' atypical, slower spike-wave paroxysms;23 diffuse spiking, spikewave, or polyspike wave as seen in myoclonic epilepsies or numerous encephalopathies;4 5 generalised, individual small amplitude " spikes" ;6 rapid 30 Hz central sinusoidal rhythms;5 or the more continuous rhythmic delta activity of a generalised cerebral disturbance.7 Recently, the categorisation of myoclonus into electrophysiological types68-12 has been facilitated by computerised methodology involving jerk-locked averaging of EEG data.'3 We now report a series of patients whose myoclonus was associated with a bilaterally synchronous electrocerebral event. form"-and the other in the well-described setting of Trisomy 21 (Down's syndrome).'6'8 The ninth patient was a 14-year-old girl with a familial progressive myoclonic epilepsy. The tenth patient had a degenerative disease of unknown nature. The last patient had typical petit mal epilepsy with 3 Hz spike and wave paroxysms on EEG and a strong family history. All patients were taking at least one anticonvulsant agent. MethodsEMG was recorded with pairs of surface electrodes placed longitudinally, 2-3 cm apart, over the mid-portion of the muscle. EEG was recorded with a Grass Model-8 electroencephalograph in referential linkage to ipsilateral ears with gold cup electrodes positioned in accordance with the 10-20 system (fig 1); the frequency response range was 1 to 35 or 70 Hz. The electrical signals were amplified and led to a PDP-11 computer which collected and sometimes averaged the data. Four to sixteen simultaneous data channels were employed. Computer collection was triggered by an event in one of the channels (using a Schmidt trigger pulse); events before and after the trigger could be recorded. The sensitivity of the trigger was set so that a trigger occurred only with definite jerks and not with occasional low level background EMG activity; by doing this, small jerks would not trigger a collection. Topographic analysis of 16-channel EEG data was carried out with computer programs previously described."9 506

Fame 3

“…Jerk-locked averaging showed a series of waves, a similar pattern to that described initially in primary generalized epileptic myoclonus and also described as a manifestation of ADCME, and in familial myoclonus epilepsy. 7,20,21 The condition described in this report, which we have termed FAME 3, appears different from FAME, and does not link to the FAME 1 locus for Family B. We cannot completely rule out the FAME 1 locus in Family A, but the FAME 2 locus has been excluded in both families.…”

Postoperative Myoclonus After Epilepsy Surgery: A Case Report

“…Postoperative paraplegia with spinal myoclonus possibly caused by epidural anesthesia was also re- ported [12]. The occurrence of bilateral myoclonus following brain surgery and temporal lobe resection has been reported in only a few patients [6][7][8]. Bilateral non-epileptic myoclonus after resection of the frontal lobe, to our knowledge, has never been reported.…”

“…Few days or weeks after the operation, the patients developed restlessness of fingers and hands accompanied by atypical 2 Hz spike-wave from a temporal focus [6] or brief bilateral jerks occurring weekly and always with clear consciousness [8]. Here, we present a patient with traumatic intractable epilepsy who developed myoclonus after brain surgery mimicking epileptic myoclonus, and discuss the importance of understanding of the origin of myoclonus in the management of the patients.…”

“…Occurrence of myoclonus following a left temporal lobectomy for chronic encephalitis [6] as well as after standard anterior temporal lobectomy for medically intractable temporal lobe epilepsy has been reported [8]. Few days or weeks after the operation, the patients developed restlessness of fingers and hands accompanied by atypical 2 Hz spike-wave from a temporal focus [6] or brief bilateral jerks occurring weekly and always with clear consciousness [8].…”

“…Focal myoclonus can be caused by trauma, infection, tumors, vascular diseases, and neuroinflammation [3,4]. In addition, focal myoclonic seizure has been reported to occur during surgical procedures due to administration of anesthetic agents [5] or after brain resection due to operative failure in terms of seizure control, coexisting generalized epilepsy or a complication of brain resection [6][7][8].…”