Abstracts

Rationale: Although unilateral and asymmetrical features of motor seizures (e.g.cephalic version and “Figure 4” sign) correctly indicate laterality of secondarily generalized seizure origin in many cases, their reliability apparently diminishes during seizure progression as semiology then may reflect ictal propagation rather than origin (Chauvel etal, 1995; Williamson,1992; Kotagal etal 2000). Unstudied has been the sequential tonic postures of head and multiple limb joints as primary and secondarily generalized (PG and SG) motor seizures evolve, nor their ability to distinguish between these two generalized seizure typesMethods: We scrutinized generalized motor seizures, one each occurring among 15 in-patients evaluated for intractable epilepsy. Sequential tonic positions of head and multiple limb joints lasting at least 3 seconds divided each seizure into phases. These were analysed by authors independently without patient identity nor EEG data. .Mutual review resolved interpretation discrepancies. Ictal and interictal EEGs defined PG and SG in this studyResults: Three ictal phases occurred in 7 patients, 4 in 5, and 5 in 3. Seizures involved most joints in most phases, e.g. cephalic version (12 patients), shoulders (11), elbows,(11), hips (11), and knees (9). The proportion of patients in whom a majority of joints exhibited bilaterally symmetrical features (principally flexion or extension) became greater in later phases (3 and 4) than in early (1 and 2) phases (Table and Figure). Among 56 involved joints (15 patients) for which flexion or extension positions of elbows, hips or knees were visibly involved for 2 or more phases, flexion progressed to extension in 36 joints, extension to flexion in 2 while flexion and extension were each sustained in 5 and 8 joints respectively. Flexion/extension alternated in 5 joints. Bilaterally symmetrical involvement of most homologous joints occurred during phase 1 in all 5 patients with PG and in only 3 of 10 with SG (P value (Fisher’s) = 0.031), whereas no such distinction appeared in phases 2-4. Cephalic version with neck extension occurred contralateral to focal origin in 6/6 patients in phase 1 and 4/4 in phase 2.Ipsiversion with neck flexion appeared in one patient. However, early version occurred in 3/5 patients with PG.Flexor and extensor symmetry (unilateral simultaneous flexion or extension of elbow and hips/knees, Foerster,1936)) (postures 1,2 of Figure) did not occur more often than by chanceConclusions: Although asymmetrical postures of bilaterally homologous joints distinguished PG from SG in phase one , increasing symmetry of later phases blurred the distinction of these two entities. As ictal tonic postures depend largely upon activation of the reticulospinal tract (RST), the more common progression from flexion to extension likely reflects increasing excitation of RST as the generalized seizure progresses (Burnham, 1987). Lack of more common flexor or extensor symmetry implies a limited role of direct supplementary motor or premoter efferents to the spinal cord in producing tonic ictal phenomena