Electroencephalographic findings in Friedreich's ataxia

Electroencephalographic tracings of 50 patients who presented the classical features of Friedreich's ataxia were reviewed. Mild nonspecific abnormalities were found in 33% and consisted of: a) Abnormal slow or irregular background rhythms in 15 patients (30%). b) Intermittent paroxysmal rhythms, considered to be projected from diencephalic or upper midbrain structures, in 4 patients (8%). c) Unilaterally absent driving responses in 2 affected siblings (4%). There was no response to intermittent photic stimulation in 60% of the patients. This finding is not considered a definite abnormality, and its significance remains unclear. Four patients (8%) had epileptic seizures, but of these only two had interictal epileptic abnormalities. There was no correlation between the duration and severity of the disease and the presence of electroencephalographic abnormalities. Friedreich's ataxia is mainly a spinal disorder. Involvement of supraspinal and in particular brain stem or diencephalic structures may be more extensive in those patients who show electrographic abnormalities. This would require confirmation with comparative data based on pathological observations. Impaired function of brain stem inhibitory mechanism may be responsible for the slightly raised incidence of seizures in patients with Friedreich's ataxia and other cerebellar degenerations.