Spectrum of epilepsy in terminal 1p36 deletion syndrome

Summary Purpose: Previous reports have summarized the seizures types occurring in 1p36 deletion syndrome. To better define the spectrum of epilepsy, we studied 91 patients (median age 7.8 years) with confirmed 1p36 deletion. Methods: Based on clinical charts, we retrospectively analyzed the evolution of both the EEG findings and seizures. Results: Epilepsy occurred in 53 patients (58.2%), with onset at a median 2.75 months. First seizures were generalized tonic (8 cases), tonic and clonic (6) or myoclonic (12), simple partial (6), or complex partial (14). Thereafter, 20 patients (21.9%) developed infantile spasms with hypsarrhythmia, at a median age of 5 months. High doses of oral steroids were tried in nine cases, with a prompt remission of seizures in six. Among them, five were seizure‐free at the time of evaluation. Conversely, two of three nonresponders to steroids developed severe and refractory epilepsy. At the time of evaluation, 32 patients were seizure‐free, from a median age of 1.8 years. Nineteen patients (20.9%) had developed refractory epilepsy with polymorphic seizures, including generalized tonic and tonic–clonic seizures (13) combined with myoclonic seizures (11) and atypical absences (3), atonic seizures (2), or complex partial seizures (3). The EEG showed focal, multifocal or generalized spikes, polyspike, and waves, with poverty of the usual background rhythmic activities. Conclusions: Early epilepsy is a frequent finding in 1p36 deletion syndrome with infantile spasms as of the most common features that can contribute to a poor clinical outcome. Early diagnosis and management of infantile spasm in this condition is mandatory.