SPECTROSCOPIC IMAGING OF FRONTAL NEURONAL DYSFUNCTION IN HYPEREKPLEXIA

We used proton magnetic resonance spectroscopic imaging (MRSI) to asse ss in vivo cortical neuronal involvement in hyperekplexia. Cerebral ne uronal function was measured using proton MRSI in four unrelated patie nts with hyperekplexia and 20 healthy controls. All patients had the m ajor form of hyperekplexia, with additional atypical clinical features in two of them, Family history was positive in three patients and abs ent in one. The neuronal marker N-acetylaspartate (NAA), choline-conta ining compounds (Cho) and creatine (Cr) were measured in frontal, cent ral and parietal areas. The MRSI showed a reduction of the relative re sonance intensity of NAA/(Cr + Cho) in frontal and central regions in three patients, and in the right frontal region of the fourth. In one patient a second MRSI showed normal relative NAA resonance intensities over both temporal lobes as well as in the brainstem, In two subjects the topography of EEG abnormalities in the frontal lobes coincided wi th the MRSI findings, This proton MRSI study indicates the presence of frontal neuronal dysfunction in hyperekplexia, Whether this represent s cortical dysfunction or an epiphenomenon of diencephalic or brainste m abnormalities remains open. However, the observation of normal proto n MRSI in the temporal regions and brainstem in one of the patients se ems to concur with the hypothesis of a facilitatory role of cortical d ysfunction within areas of sensorimotor representation in the generati on of the pathological startle reaction in hyperekplexia.