Postauricular (12 msec latency) responses to acoustic stimuli in patients with peripheral, facial nerve palsy

The postauricular (12 msec latency) response to a loud click stimulation was investigated in 23 patients with facial nerve palsy. Of these patients 21 had an intracranial cause for the facial palsy and 2 had an extracranial cause. Only in those with the extracranial facial nerve damage could the response be obtained from both sides. When the nerve was damaged intracranially there was no response on the paralysed side. This seems to indicate that the posterior auricular muscle is the effector of the presumed sonomotor reflex arc involving the cochlea, cochlear nerve and nuclei, undetermined brainstem pathway, facial motor nucleus, facial nerve and the muscles supplied by it.