The head stabilization reflex by stimulation of accessory nerve.

The head stabilization reflex (HSR) was described by a new technique of stimulating the accessory nerve and then the reflex muscle responses' were recorded electromyographically from the contralateral sternocleidomastoid muscle. Thirty-two normal control subjects and 22 patients with various neurological disorders were studied. The HSR obtained from the contralateral sternocleidomastoid muscle was very stable with a mean latency of about 45 ms and was regularly obtained by the supramaximal stimulation of the ipsilateral accessory nerve from the normal subjects. The HSR was absent in 9 out 11 patients with cerebellar syndrome. The HSR seemed to be a oligo-polysynaptic/plurosegmental reflex under the strong control of the cerebellum.