Infantile Spasms with Basal Ganglia MRI Hypersignal May Reveal Mitochondrial Disorder Due to T8993G MT DNA Mutation

Abstract

To report three cases of infantile spasms (IS) with an abnormal magnetic resonance imaging signal in the basal ganglia (Leigh-like syndrome), due to T8993G mt DNA mutation. The first sign was, at the end of the first year of life, IS in one case and the combination of IS with behavior changes in the two other cases. Video EEG polygraphy demonstrated both spasms and hypsarrhythmia, but no other kind of seizures. Vigabatrin or steroids controlled the spasms with a follow-up of several years. All 3 patients had hyperlactatorrhachia (3.47 to 7 mmol/l). Axial hypotonia and dystonia appeared by the end of the first year of life. As in cases with the NARP mutation and onset later in life, neuropathy and retinopathy could also be demonstrated. Although it is well established that symptomatic IS with hypsarrhythmia mainly result from cortical lesions, this epileptic encephalopathy may also be generated by lesions in the basal ganglia without evidence of cortical damage. This finding suggests that West syndrome is likely to be caused by age-related dysfunction at any level of a cortico-putaminal loop of hyperexcitability.