Infantile spasms in tuberous sclerosis complex

Abstract

The high incidence of infantile spasms (IS) and hypsarrhythmia in tuberous sclerosis complex (TSC) has long been emphasized but it is now clear that infants with TSC show clinical and EEG differences from those with classical West syndrome. Seizures at onset are mainly characterized by partial motor seizures and IS. Subtle partial seizures may be present in the early neonatal period and may precede the onset of IS. Visual recording techniques have led to significant progress in the classification of seizures associated with TSC, demonstrating that they have a focal or multifocal origin in the vast majority of cases. In most cases, an awake interictal EEG shows focal or independent multifocal spike and slow-wave activity at onset and later a pseudo-hypsarrhythmic pattern. Ictal EEG starts with focal spikes originating from the posterotemporal, or occipital regions followed by a generalized irregular slow transient and an abrupt diffuse flattening. Although the pathophysiological mechanisms responsible for the coexistence of partial seizures and IS are still unclear, IS associated with TSC may be the result of a rapid secondary generalization. The presence of IS due to TSC is strongly predicted by the cortical tuber count, while the age of onset of seizures and the age of occurrence of EEG foci depend on the localization of cortical tubers with an earlier expression of the parieto-occipital than of the frontal regions. Early recognition of these distinctive features appears worthwhile for therapeutic and prognostic implications. Despite the efficacy of vigabatrin the prognosis of IS is generally poor. Studies using combined topographic mapping of EEG, magnetic resonance imaging and positron emission tomography may provide new strategies for selecting candidates suitable for surgery.