Disinhibition of somatosensory and motor cortex in mitochondriopathy without myoclonus

Objective: To test electrophysiologically, if patients with mitochondriopat hy 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 gr oups. Results: In both patients, giant somatosensory evoked potentials after medi an nerve stimulation and a reduced intracortical inhibition tested by trans cranial magnetic stimulation in a paired pulse paradigm indicated a dysfunc tion of inhibitory circuits in the motor as well as the somatosensory corte x. In addition, the somatosensory evoked 600 Hz activity recorded by magnet oencephalography was abolished. Conclusions: Patients with mitochondriopathy may suffer from a subclinical disturbance of inhibition in the sensorimotor cortex. The loss of 600 Hz ac tivity indicates that these high-frequency oscillations could reflect the a ctivity of inhibitory neurons in the somatosensory cortex. (C) 2001 Elsevie r Science Ireland Ltd. All rights reserved.