The geniculate ganglion (“external genu”) is located within the temporal bone. The first branch from the ganglion is the greater superficial petrosal nerve (GSPN) which passes to the pterygopalatine ganglion and innervates the nasal and palatine mucosa and the lacrimal gland of the eye; lesions proximal to this point produce a dry eye.
The geniculate ganglion (from Latin genu, for “knee” is an L-shaped collection of fibers and sensory neurons of the facial nerve located in the facial canal of the head. It receives fibers from the motor, sensory, and parasympathetic components of the facial nerve and sends fibers that will innervate the lacrimal glands, submandibular glands, sublingual glands, tongue, palate, pharynx, external auditory meatus, stapedius, posterior belly of the digastric muscle, stylohyoid muscle, and muscles of facial expression.
The geniculate ganglion contains special sensory neuronal cell bodies for taste, from fibers coming up from the tongue through the chorda tympani and from fibers coming up from the roof of the palate through the greater petrosal nerve.
Sensory and parasympathetic inputs are carried into the geniculate ganglion via the nervus intermedius. Motor fibers are carried via the facial nerve proper. The greater petrosal nerve, which carries sensory fibers as well as preganglionic parasympathetic fibers, emerges from the anterior aspect of the ganglion.
The geniculate ganglion is one of several ganglia of the head and neck. Like the others, it is a bilaterally distributed structure, with each side of the face having a geniculate ganglion.