Disinhibition of somatosensory and motor cortex in mitochondriopathy without myoclonus

Objective: To test electrophysiologically, if patients with mitochondriopathy but without evidence of myocloni have subclinical signs of disinhibition in motor and somatosensory cortices. Methods: Two patients were studied and compared with age-matched control groups. Results: In both patients, giant somatosensory evoked potentials after median nerve stimulation and a reduced intracortical inhibition tested by transcranial magnetic stimulation in a paired pulse paradigm indicated a dysfunction of inhibitory circuits in the motor as well as the somatosensory cortex. In addition, the somatosensory evoked 600 Hz activity recorded by magnetoencephalography was abolished. Conclusions: Patients with mitochondriopathy may suffer from a subclinical disturbance of inhibition in the sensorimotor cortex. The loss of 600 Hz activity indicates that these high-frequency oscillations could reflect the activity of inhibitory neurons in the somatosensory cortex.