Näonärvi

Näonärvi, known in English as the facial nerve (cranial nerve VII), is the seventh cranial nerve. It provides motor innervation to the muscles of facial expression and carries special sensory and autonomic fibers. The nerve has a dual embryologic and functional character: a motor root and a nervus intermedius carrying taste fibers and parasympathetic fibers. Its fibers originate in the brainstem (facial motor nucleus and nervus intermedius) and it travels internal to the skull before emerging at the stylomastoid foramen to supply facial muscles.

Anatomy and course are characterized by a complex intracranial and intratemporal path. After leaving the brainstem, the nerve traverses the internal acoustic meatus with the vestibulocochlear nerve, then passes through the facial canal in the temporal bone. In the temporal bone it gives off the greater petrosal nerve and the chorda tympani; it also gives off the nerve to stapedius. The nerve exits the skull at the stylomastoid foramen and divides into terminal branches—temporal, zygomatic, buccal, marginal mandibular, and cervical—that innervate the muscles of facial expression. Parasympathetic fibers reach lacrimal and salivary glands via two routes: greater petrosal nerve to the pterygopalatine ganglion (lacrimal and nasal glands) and chorda tympani to the submandibular ganglion (submandibular and sublingual glands). Taste from the anterior two-thirds of the tongue travels with the chorda tympani to the brainstem.

Clinical significance includes facial nerve palsy, which causes weakness of facial muscles, inability to close the eye, and altered facial symmetry. Other signs may include hyperacusis, decreased lacrimation, reduced saliva, and loss of taste on the anterior tongue. Common conditions involve Bell’s palsy, Ramsay Hunt syndrome, tumors, or trauma affecting CN VII.