Abstracts

Rationale: Early epileptic encephalopathy with suppression burst (Ohtahara syndrome: OS) is very severe epileptic encephalopathy and its seizure and developmental prognoses are exclusively very poor. Os with hemimegalencephaly (HMC) is the severest disease, and the patients usually become bed-ridden and tube-fed without early surgery. We studied on early predictors for developmental outcome after hemispherotomy (HS) in patients with OS with HMC by using brain evoked potentials. Methods: Seventeen patients with OS with HMC who underwent HS with vertical approach at 2 to 7 months except at 11 months in one patient were prospectively studied. Spasms or brief tonic seizures with occasional cluster developed at the first day of life to one month of age. Three cases had linear sebaceous nevus and 3 cases had Hypomelanosis of Ito. The patients were sedated with oral triclofos sodium or rectal chloral hydrate, and latencies of bilateral wave IV (P100) of flash visual evoked potentials (VEP), wave V and I-V of auditory brainstem response (ABR), N18 of median nerve somatosensory evoked potentials (SEP), and N20 of median nerve short latency somatosensory evoked potentials (SSEP) were examined by using Neuropack X1 (NIHON KOHDEN Co., Tokyo) before HS and 2 weeks to 3 months after HS. Developmental outcome was evaluated at 14 to 128 months of age by mail survey or face to face survey by using Kinder Infant Development Scale (KIDS). Results: Development quotient (DQ) ranged from 3 to 73. Thirteen patients were seizure-free and 4 patients had residual seizures. Among seizure-free patients, 11 patients had DQ 25-72 (Group A) and 2 patients had DQ 7-9 (Group B), and patients with residual seizures had DQ 3-8 (Group C). N20 at the non-HMC side was not evoked in all but 2 cases before HS. These 2 cases belonged to Group A and showed delayed N20 latency. N20 at the non-HMC side emerged with normal or subnormal latency in all cases in Group A, but none in Group B and one in Group C after HS. No correlation was seen between DQ and changes of latencies of P100 of flash VEP, wave V and I-V of ABR, and N18 of median nerve SEP at the non-HMC side before and after HS among three groups. Conclusions: The present study suggests that emergence of N20 or normalization of N 20 latency of median nerve SSEP at the non-HMC side early after HS can be an early predictor of fairly good developmental outcome in patients with OS with HMC after HS. Patients without improvement of N20 of median nerve SSEP after HS may have poor developmental outcome even if they obtain seizure-freedom.