The geniculate ganglion (from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''genu'', for "knee") is a bilaterally paired special sense ganglion of the

intermediate nerve The intermediate nerve, nervus intermedius, nerve of Wrisberg or glossopalatine nerve is the part of the facial nerve (cranial nerve VII) located between the motor component of the facial nerve and the vestibulocochlear nerve (cranial nerve VIII) ...

component of the facial nerve (CN VII). It is situated within

facial canal The facial canal (also known as the Fallopian canal) is a Z-shaped canal in the temporal bone of the skull. It extends between the internal acoustic meatus and stylomastoid foramen. It transmits the facial nerve (CN VII) (after which it is nam ...

of the

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...

. It contains cell bodies of first-order unipolar

sensory neuron Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded receptor potentials. This process is called sensory transduc ...

s which convey gustatory (taste) afferents from taste receptors of the anterior two-thirds of the tongue by way of the

chorda tympani Chorda tympani is a branch of the facial nerve that carries gustatory (taste) sensory innervation from the front of the tongue and parasympathetic ( secretomotor) innervation to the submandibular and sublingual salivary glands. Chorda tymp ...

, and of the

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...

by way of the

greater petrosal nerve The greater petrosal nerve (or greater superficial petrosal nerve) is a nerve of the head mainly containing pre-ganglionic parasympathetic fibres which ultimately synapse in the pterygopalatine ganglion. It branches from the facial nerve (CN VI ...

, From the ganglion, the proximal fibres proceed to the gustatory (i.e. superior/rostral) part of the

solitary nucleus The solitary nucleus (SN) (nucleus of the solitary tract, nucleus solitarius, or nucleus tractus solitarii) is a series of neurons whose cell bodies form a roughly vertical column of grey matter in the medulla oblongata of the brainstem. Their a ...

where they synapse with second-order neurons.

Anatomy

Structure

The geniculate ganglion is conical in shape. The

diverges from CNVII and the

lesser petrosal nerve The lesser petrosal nerve (also known as the small superficial petrosal nerve) is the general visceral efferent (GVE) nerve conveying pre-ganglionic parasympathetic secretomotor fibers for the parotid gland from the tympanic plexus to the otic g ...

diverges from CN IX at the geniculate ganglion.

Relations

It is located close to the

internal auditory meatus The internal auditory meatus (also meatus acusticus internus, internal acoustic meatus, internal auditory canal, or internal acoustic canal) is a canal within the petrous part of the temporal bone of the skull between the posterior cranial fossa ...

. It is covered superiorly by the

petrous part of the temporal bone The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three ...

(which is sometimes absent over the ganglion).

Clinical significance

The geniculate ganglion is an important surgical landmark near the

Herpes zoster oticus

The geniculate ganglion may become

inflamed Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', ''d ...

due

herpes zoster virus Varicella zoster virus (VZV), also known as human herpesvirus 3 (HHV-3, HHV3), is one of nine known herpes viruses that can infect humans. It causes chickenpox (varicella) commonly affecting children and young adults, and shingles (herpes zos ...

virus infection. Swelling of the ganglion may result in facial palsy (

Ramsay Hunt syndrome Three different neurological syndromes carry the name of Ramsay Hunt syndrome. Their only connection is that they were all first documented by the famous neurologist James Ramsay Hunt (1872–1937). * Ramsay Hunt syndrome type 1, also called ''Rams ...

). The syndrome presents with intense pain in one ear that is followed by a vesicular rash around the

ear canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the auricle to the eardrum and is about in length and in diameter. S ...

Additional images

File:Gray788.png , Plan of the facial and intermediate nerves and their communication with other nerves.

References

External links

* () * () {{Authority control Nervous ganglia of the head and neck Gustatory system Sensory ganglia Otorhinolaryngology Cranial nerves Facial nerve