Asymmetric epileptic spasms after corpus callosotomy in children with West syndrome may be a good indicator for unilateral epileptic focus and subsequent resective surgery

Abstract

Objective: This retrospective study was designed to observe differences in ictal movements of epileptic spasm (ES) before and after corpus callosotomy (CC). We hypothesized that asymmetric expression of ES is more clarified after CC and would be a good indicator for the epileptic hemisphere.

Methods: We selected 16 patients with intractable ES in West syndrome who were seizure-free after CC and subsequent resection or disconnective surgery of the unilateral hemisphere. We retrospectively reviewed their behavioral ES recorded at video-electroencephalography monitoring before and after CC. Asymmetric neck flexion (NF) and involuntary muscular contraction of the upper and lower extremities (MCU and MCL, respectively) were primarily described correlating their laterality and the responsible hemisphere proved by surgical resection.

Results: Asymmetric NF, MCU, and MCL could be found both before and after CC. However, the percentage of those movements to the total number of ES increased after CC; asymmetric NF, 82.9% vs. 20.1%; unilaterally predominant MCU, 81% vs. 39.3%; and unilaterally predominant MCL, 77.6% vs. 29.9%. Regarding asymmetric NF, the direction in which the neck flexed or the head turned was significantly ipsilateral to the responsible hemisphere in 9 of 12 patients after CC (75%). The predominant side of MCU and MCL were significantly contralateral to the responsible hemisphere in 11 of 11 and 7 of 9 patients (100% and 77.8%, respectively).

Significance: Asymmetric NF, MCU, and MCL were clarified in patients with ES who were successfully treated with CC and subsequent surgery. Those changes in ictal behaviors after CC may indicate the lateralization of epileptic activity and encourage more curative surgical treatment.

Keywords: corpus callosotomy; epilepsy surgery; epileptic spasms; west syndrome.

FIGURE 1

Asymmetric NF and MCU after CC (Case 4). Representative asymmetric NF and MCU are shown (case 4). Ictal correlates with a high‐amplitude slow wave in the right hemisphere followed by a brief electrodecremental pattern as seen on EEG (bottom). (A) Before the appearance of ES. (B,C) NF with slight head flexion and right side turning (arrow), where the body also flexed ventrally, and the left arm slightly moved laterally by the flexion of the shoulder joint (Video S1). NF, neck flexion; MCU, muscle contraction of upper extremities; CC, corpus callosotomy; EEG, electroencephalography; ES, epileptic spasms

FIGURE 2

Asymmetric NF and MCU after CC (Case 12). Representative asymmetric NF and MCU are shown (case 12). Ictal correlates with fast waves and high‐amplitude slow wave in right hemisphere followed by brief electrodecremental pattern are seen on EEG (bottom). (A) Before the appearance of ES. (B,C) NF with forced head flexion and right side turning (arrowhead), where the body also flexed ventrally, and the left arm moved laterally by the flexion of the shoulder and elbow joints (arrow) (Video S2). NF, neck flexion; MCU, muscle contraction of upper extremities; CC, corpus callosotomy; EEG, electroencephalography; ES, epileptic spasms.

FIGURE 3

Symmetry and asymmetry in NF, MCU, and MCL before and after CC. X‐axis, relative laterality index of asymmetric movements; Y‐axis, the relative frequency of symmetric movements. Individual symbols correspond to each patient. The distribution of plots can be compared before and after the CC, and symmetry or laterality in each movement can be visualized here. Significant lateralization is defined if the absolute value of the laterality index is more than 0.5. Symbols show individual patients. (A) NF: Direction of NF during ES is straight to the middle before but deviated to the left or right side after CC in most patients, where significant lateralization to the responsible hemisphere is seen in nine of 12 patients. (B) MCU: MCU during ES is bilaterally symmetric but unilaterally predominant in most patients after CC, where significant lateralization contralateral to the responsible hemisphere is seen in 11 of 11 patients. (C) MCL: MCL during ES is bilaterally symmetric before but unilaterally predominant in many patients after CC, where significant lateralization contralateral to the responsible hemisphere is seen in seven of nine patients. NF, neck flexion; MCU, muscle contraction of upper extremities; MCL, muscle contraction of lower extremities; CC, corpus callosotomy; EEG, electroencephalography; ES, epileptic spasms.