A study of multimodality evoked responses in idiopathic spasmodic torticollis.

A wide variety of anatomical sites have been implicated in the pathogenesis of torticollis, based primarily on animal studies. These include lesions in the mesencephalic tegmentum, third ventricle, diencephalon, pre-tectal area, prestitial nucleus of the mid-brain, cervical cord, atlanto-axial junction and motor cortex, amongst others. This study describes the use of multimodality evoked potentials including visual, auditory, bilateral median and peroneal somatosensory evoked responses, undertaken in patients with idiopathic spasmodic torticollis. An attempt was made to non-invasively identify any physiological disruption along these major pathways which could help locate a causative lesion. Normal evoked responses were obtained both ipsilateral and contralateral to the affected side in all patients. It is concluded that the lesion in idiopathic spasmodic torticollis does not discernibly involve the visual, auditory or motor somatosensory pathways.