Definition and Overview
Labyrinthectomy is a specialised, destructive surgical procedure used to manage a condition known as vestibular dysfunction. It involves the removal of balance end organs to prevent the brain from receiving signals from the parts of the inner ear that sense motion and gravity changes.
Knowing the anatomy and physiology of the inner ear is crucial in the understanding of labyrinthectomy. The inner ear can basically be divided into two parts: the cochlear system, which is responsible for hearing; and the vestibular system, which is responsible for balance. Structurally, it is made up of the bony labyrinth, a set of bony passages which contain the membranous labyrinth, where receptors can be found. Inner ear fluid, the perilymph and the endolymph, are contained in the labyrinths. The bony labyrinth has several parts, namely the cochlea, the semicircular canals, and the vestibule.
The vestibular system is composed of semicircular canals and the vestibule, which is made up of membranous sacs known as the saccule and the utricle. Together, these components greatly contribute to the sense of balance by detecting changes in rotation, linear motion, and gravity. If these areas are damaged by injury or disease, vestibular disorders such as Meniere’s disease can develop.
Who Should Undergo and Expected Results
Labyrinthectomy is considered for the treatment of vestibular disorders in cases wherein adequate medical therapy and rehabilitation have failed to address the condition.
A vestibular disorder is a disease that affects the sense of balance. It affects as much as 35% of people who are 40 years old and above in the United States alone. These conditions usually present with vertigo and chronic dizziness. Disorientation, temporary nausea, ear fullness, and loss of sense of balance can also occur. Some patients may also experience tinnitus, or a constant buzzing in the ear and hearing loss. Common vestibular disorders include labyrinthitis, benign paroxysmal positional vertigo, and Meniere’s disease, to name a few.
Labyrinthectomy is a destructive procedure; hence, it is reserved for patients with disabling peripheral vestibular disorders on one side. As much as possible, this operation should be limited to patients with an associated hearing loss on the same side. Labyrinthectomy has specifically been advocated for patients with Meniere’s disease, a condition wherein the pressure in the endolymphatic system of the inner ear is increased. Surgery is indicated in these patients who fail to respond to medical treatment, usually after 3 to 6 months from initiation. Patients who experience severe disability related to the disease may opt to undergo the procedure sooner. However, for young patients and those with bilateral disease, experts suggest other alternative treatment options.
Control of vertigo after labyrinthectomy is very high, occurring in about 95% of patients.
How is the Procedure Performed?
The goal of labyrinthectomy is the complete destruction of all the vestibular end organs to eliminate vestibular function.
There are two ways to approach a labyrinthectomy: the transcanal approach and the transmastoid approach. The former is more commonly performed while the latter is typically used for patients who have narrow openings or canals.
The transcanal approach involves the creation of a tympanomeatal flap to gain access to the middle and inner ear to perform the curettage of the posterior annulus. The incus and the stapes are then removed by cutting the tendon of the stapedius muscle. The oval window is drilled to make it larger in order to connect with the round window before the end organ is destroyed. The saccule and the utricle are then scraped and the semicircular canals are probed.
Once the destruction is complete, an antibiotic-filled gelatin sponge may be used to fill up the vestibule.
On the other hand, the transmastoid approach utilises an incision behind the ear to expose and cut the mastoid bone to visualise the structures of the middle and inner ear. The semicircular canals are then drilled and opened up, and the facial nerve preserved. The vestibular end organs are then removed. Finally, the cavity of the mastoid is closed.
Possible Risks and Complications
When performed properly, complications of labyrinthectomy are uncommon. Patients are typically given anti-emetic medications postoperatively to minimise vomiting and nausea, which may be present for several days. Informed consent is very important for this destructive procedure as hearing loss on the side operated on is inevitable.
A possible complication is a cerebrospinal fluid (CSF) leak. If the leak is noted during the operation, it needs to be repaired at the same time. For small leaks, bone wax may be used for closure. For bigger leaks, a muscle plug may have to be placed. CSF leaks that are not repaired may cause serious complications, such as meningitis.
One of the more devastating complications of a labyrinthectomy is injury to the facial nerve. For this reason, some surgeons routinely use a facial nerve monitor during the procedure, to make sure that the nerve is preserved.
An incomplete labyrinthectomy occurs in approximately 5% of patients undergoing the procedure. All neuroepithelium should be removed so as to prevent the recurrence of neuronal activity and persistence of vertigo. The utricle may also be difficult to locate because it tends to retract; use of an utricular hook may help. If symptoms of vertigo persist, revision surgery may have to be performed.
Dickins JRE, graham SS. Surgical treatment of peripheral vestibular disorders. Glasscock ME, Gulya AJ.Glasscock-Shambaug’s Surgery of the ear. 5th ed. Ontario: BC Deckers; 2005. 517-575.
Tutar H, Tutar VB, Gunduz B, Bayazit YA. Transmastoid labyrinthectomy for disabling vertigo after cochlear implantation. J Laryngol Otol. 2014 Nov. 128(11):1008-10.