Facial canal

Facial canal is a bony structure found in the temporal bone of the skull, which houses and protects the facial nerve (CN VII) as it traverses through the skull. The facial canal is crucial for the protection and function of the facial nerve, which is responsible for controlling the muscles of facial expression, conveying taste sensations from the anterior two-thirds of the tongue, and supplying secretomotor fibers to the lacrimal, submandibular, and sublingual glands.

Anatomy

The facial canal begins at the internal acoustic meatus, a passage in the temporal bone, and ends at the stylomastoid foramen, through which the facial nerve exits the skull. The canal can be divided into three segments: the labyrinthine segment, the tympanic segment, and the mastoid segment.

Labyrinthine Segment

The labyrinthine segment, also known as the meatal segment, is the shortest and narrowest part of the facial canal. It begins at the fundus of the internal acoustic meatus and extends to the geniculate ganglion, a swelling in the nerve that contains cell bodies of sensory neurons.

Tympanic Segment

The tympanic segment runs laterally from the geniculate ganglion, above the oval window (an opening in the bone surrounding the cochlea), and continues behind the tympanic cavity. This segment is important as it is where the nerve makes a sharp bend, known as the first genu.

Mastoid Segment

The mastoid segment is the longest part of the facial canal. It extends from the second genu, located at the posterior wall of the tympanic cavity, and descends vertically to exit the skull through the stylomastoid foramen. This segment of the canal also gives off a small branch known as the chorda tympani, which carries taste fibers from the anterior two-thirds of the tongue and secretomotor fibers to the submandibular and sublingual glands.

Clinical Significance

Damage to the facial nerve at any point along the facial canal can result in facial nerve palsy, which is characterized by weakness or paralysis of the muscles of facial expression on the affected side. Causes of facial nerve damage include Bell's palsy, infections, tumors, and trauma. Diagnosis often involves imaging studies such as MRI or CT scans to visualize the facial canal and identify any abnormalities.

Treatment

Treatment of facial nerve palsy depends on the underlying cause. Corticosteroids are commonly used to reduce inflammation in cases of Bell's palsy. Surgical intervention may be necessary to relieve pressure on the nerve in cases of trauma or to remove tumors.

See Also

• Temporal bone
• Facial nerve
• Bell's palsy
• Skull