Video‐Polygraphic Analysis of Myoclonic Seizures in Juvenile Myoclonic Epilepsy

Abstract

We studied myoclonic seizures (MS) in 5 patients with juvenile myoclonic epilepsy (JME) using video polygraphic recordings to investigate the clinical characteristics of MS in this epileptic syndrome. The total number of MS analyzed was 302 (range 27-125, mean 60) seizures per patient. MS occurred either singly or repetitively (37 vs. 63%) and corresponded to generalized bilaterally synchronous single or multispike-and-wave complexes at 3-5 Hz. Video analysis of the myoclonic jerks demonstrated that either distal or proximal muscle involvement predominated. In the former, there was mild bilateral flexion and some external rotation of the forearms. In the latter, flexion of both arms at the elbow, flexion and abduction of the thighs, and extension of the back was observed. Asymmetry of MS was noted in 4 of 5 patients. Facial involvement of MS occurred infrequently in 2 patients. When the patients kept both arms outstretched, the arms dropped or there was sudden interruption of ongoing electromyographic (EMG) potentials immediately after myoclonic jerks (postmyoclonic inhibition) in all patients. One should inquire about these clinical characteristics of MS in JME when taking a thorough history in patients with primary generalized tonic-clonic seizures (GTC).

Atonic Epileptic Drop Attacks Associated with Generalized Spike-and-Slow Wave Complexes: Video-Polygraphic Study in Two Patients

“…However, as we reported previously (6), we cannot exclude a spectrum of intensity in the initial myoclonic phenomena, ranging from the minimum observed in these 2 patients to the very intense manifestations observed in those with myoclonic-atonic seizures. We previously reported that myoclonic seizures observed in patients with juvenile myoclonic epilepsy are generally succeeded by some degree of atonia, ranging from minor atonia recognizable only on surface EMG to the more intense atonia causing actual dropping of the extending arms (12). According to our present knowledge, the term "myoclonic seizures" can be applied to the former, regardless of the mild succeeding atonia and the term "myoclonic-atonic seizures" can be applied to the latter, as is the case with atonic seizures.…”

Auras in generalized epilepsy

“…26 Auras and other "focal" features in patients with GE can lead to the misdiagnosis of FE. 4,5,16,18,19,26 It is also possible that auras in GE are underreported, and may be more likely to be elicited with systematic questioning. For most patients with epilepsy, an initial goal of clinical evaluation is distinguishing GE from FE.…”

“…4,[15][16][17][18][19] Focal clinical features such as forced lateralized head turning at seizure onset, and asymmetries and asynchronies of limb movements during the clonic phase also occur in IGE. 15 In patients with JME, unilateral and asymmetric myoclonic jerks can occur.…”

“…Furthermore, patients with JME may perceive asymmetries in myoclonic seizures that are actually symmetric. 16,17 In a study of 26 patients with JME, 14 (54%) demonstrated focal semiologic or electroencephalographic features, or both. Notably, the "figure 4" sign (extension of one arm and flexion of the contralateral arm at the elbow), which is conventionally viewed as a lateralizing sign in secondarily generalized seizures, was noted in 19.2% 18 of patients with JME.…”

“Here, There, Everywhere”, or is it Truly Partial Epilepsy?

“…Clear asymmetry of clinical myoclonic jerks was identified in four of five patients with JME in a video-Polygraphic analysis of myoclonic seizures 24 . The same study reported that ictal EEG findings were very similar to interictal EEG abnormalities that do not accompany clinical jerks.…”