Does a peculiar EEG pattern exist also for FRAXE mental retardation?

Abstract

Objective: FRAXE mental retardation, a recently identified rare genetic condition, is due to a mutation of the FMR2 gene, located at Xq28 region. The phenotype is non-specific and characterized by developmental delay, speech, reading and writing problems, poor adaptive skills, anxiety, aggressiveness, obsessive-compulsive disturbance, and hyperactivity. The objective of this study was to describe the characteristic EEG pattern found in one patient with FRAXE mental retardation. Methods: EEG (with photic stimulation and hand/foot tapping) and median nerve somatosensory evoked potentials were recorded in a 8-year-old male patient with FRAXE mental retardation (diagnosis confirmed by molecular genetic analysis) and speech disturbances. Results: The patient never presented seizures; however, sleep enhanced multifocal spikes were found in the EEG. Moreover, tactile stimulation of hands and feet, as well as intermittent photic stimulation, provoked the appearance of spikes. Somatosensory evoked potentials from the median nerves showed a ‘giant’ component at around 60 ms. Conclusions: Considering the rarity of both FRAXE mental retardation and tactile evoked spikes, their association in the same subject might be considered as not casual. If confirmed by future studies, these neurophysiological findings might be considered as a marker for FRAXE mental retardation.