Abstracts

Rationale: Late-onset spasms (LOS) are epileptic spasms (ES) starting after the first year of life, usually resistant to treatment, found in patients with brain disorders and cognitive disabilities. Gobbi et al. (1987) first described a form of LOS in which periodicity is the most characteristic element; since then there has been no description of periodic LOS. Since ES could not be classified as focal or generalized the 2010 ILAE proposal for classification of epileptic seizures classified them under unknown category. We describe periodic LOS and unique features in two children with Rasmussen encephalitis (RE) and focal cortical dysplasia (FCD). Methods: Clinical, electroencephalographical and neuroimaging findings were assessed prospectively. Results: Case 1 - A 5-year-old girl started presenting progressive left hemiparesis at 2.5 years followed, more than two years later, by clusters of asymmetric ES. Treatment with OCBZ was ineffective. Prolonged video-EEG monitoring revealed diffuse background slowing, more marked on the right hemisphere, and frequent spikes over the right frontotemporal (RFT) region. Stereotyped clusters of asymmetric periodic ES were recorded, associated with rictus-type facial grimaces, without consciousness impairment. EEG showed bursts of high voltage, generalized, symmetric, repetitive polyphasic slow spike-wave complexes, ranging from 0.5 to 2 seconds in duration, usually recurring every 5-13 seconds, with a typical diamond-shape on EMG recording. Brain CT and MRI documented progressive atrophy of the right cerebral hemisphere, more marked over the perisylvian area. With presumable diagnosis of RE a right hemispherotomy was performed. Pathology confirmed the diagnosis, and the patient has been seizure free for six months. Case 2 - A 5-year-old boy started refractory daily seizures at 1.9 years and gelastic seizures at age of 4. Interictal EEG showed diffuse background slowing, more marked on the right hemisphere, and frequent spikes over the RFT region. Clusters of bilateral and symmetric ES were recorded, combined with laugh and rictus-type facial grimaces and preserved consciousness, accompanied by periodic RFT high-voltage slow waves with a superimposed fast rhythm, recurring every 2-3.5 seconds and a typical diamond-shape on EMG. A RFT FCD was suggested by MRI; he is currently waiting for surgery. Both children presented cognitive disabilities. Conclusions: Whereas in West syndrome the majority of focal lesions involve posterior brain regions, LOS are associated with anterior lesions. As in Lennox-Gastaut syndrome, EEG abnormalities predominated in anterior areas in our cases of LOS. This sequence is likely to be determined by progressive maturation of the brain and it has been considered a new age-related epileptic encephalopathy. It has been suggested that periodicity of this intriguing pattern is the result of a diffuse or local alteration in neuronal excitability changing responsiveness to input from distant areas. The recognition of LOS in focal lesions is of paramount importance since it has implications in therapeutic and prognosis.