The nervus intermedius (nerve of Wrisberg) is the sensory and autonomic root of the facial nerve (CN VII), running between the motor root of the facial nerve and the vestibulocochlear nerve in the internal acoustic meatus. It carries special visceral afferents for taste from the anterior two-thirds of the tongue (via chorda tympani) and from the palate (via greater petrosal nerve), and general visceral efferents (parasympathetic) for the lacrimal, submandibular, and sublingual glands.
The nervus intermedius is the component of the facial nerve responsible for geniculate neuralgia, a rare cause of deep ear pain that may be confused with glossopharyngeal neuralgia. It is also involved in Ramsay Hunt syndrome where herpes zoster reactivation at the geniculate ganglion produces ear pain, vesicles at the auricle, and facial nerve palsy through the nervus intermedius involvement. Sectioning of the nervus intermedius is occasionally performed for intractable geniculate neuralgia, and its identification is important in translabyrinthine facial nerve surgery.
Irritation of the nervus intermedius at the geniculate ganglion produces paroxysmal deep ear pain radiating to the pinna, palate, and temporomandibular region, distinct from trigeminal neuralgia by its location and from glossopharyngeal neuralgia by its auricular distribution, treated by carbamazepine or nervus intermedius sectioning in refractory cases.
Herpes zoster reactivation at the geniculate ganglion involves the nervus intermedius and the main facial nerve trunk, producing the triad of ipsilateral facial palsy, vesicles in the ear canal and auricle, and severe otalgia, managed with early antiviral therapy and corticosteroids with a worse prognosis for facial recovery than Bell palsy.
