Chapter 40 Transcanal Labyrinthectomy
Labyrinthectomy is an effective surgical procedure for the management of unremitting or poorly compensated unilateral peripheral vestibular dysfunction in the presence of ipsilateral, profound, or severe sensorineural hearing loss. The physiologic rationale is that central vestibular compensation is more rapid and complete for unilateral absence of peripheral vestibular function than for unilateral abnormal function, either episodic or chronic.1
Unilateral vestibular ablation has been advocated for more than 6 decades. Selective or total eighth cranial nerve transection by the suboccipital approach was introduced by Dandy in 1928.2 Destruction of the peripheral end organs of the vestibular labyrinth was introduced by Jansen3 in 1895 for complications of suppurative labyrinthitis. This technique was applied to unilateral peripheral vestibular disturbance by Milligan4 and by Lake5 in 1904, and was reintroduced by Cawthorne6 in 1943 as a canal wall up technique. In his original description, Cawthorne apparently ablated only the lateral semicircular canal. In its current form, complete vestibular ablation is accomplished by exenteration of all three of the semicircular canals and both maculae.
The earliest report of a transcanal procedure for vertigo is credited to Crockett,7 who in 1903 described removal of the stapes as an effective treatment for vertigo. Lempert8 described an endaural transmeatal approach to the oval and round windows for Meniere’s disease. In this procedure, the stapes was removed, and the round window was punctured to “decompress” the membranous labyrinth. There was no mention, however, of the importance of destruction of the vestibular end organs. The modern transcanal labyrinthectomy for unilateral peripheral vestibular dysfunction was introduced by Schuknecht in 19569 and by Cawthorne in 1957.10 In a series of articles, Schuknecht’s technique evolved to emphasize the importance of destruction of all five vestibular end organs.11–13 Armstrong14 and Ariagno15 also emphasized the importance of total ablation of peripheral vestibular function.
PATIENT SELECTION
Although the published indications for labyrinthectomy have included hearing levels poorer than a 50 dB speech reception threshold and a 50% discrimination score, in view of the incidence of bilateral Meniere’s disease of 10% to 40%, as reported by Greven and Oosterveld16 and Paparella and Griebie,17 labyrinthectomy should be reserved for cases in which the hearing loss is severe to profound, generally with a speech reception threshold of 75 dB or worse and a speech discrimination score of less than or equal to 20%. This threshold for labyrinthectomy should be increased if hearing in the contralateral ear is not in the normal or near-normal range.
PREOPERATIVE EVALUATION
A complete history and otolaryngologic–head and neck examination should be performed. Bilateral behavioral audiometry, including pure tone thresholds for air and bone conduction and speech discrimination, is necessary. Vestibular testing should include at least bilateral caloric function, best done by electronystagmography. This assessment is necessary to evaluate the possibility of bilateral vestibular dysfunction, and to confirm vestibular dysfunction in the affected ear based on audiometry and history. Hallpike’s positional testing and evaluation for the presence of the fistula and Hennebert’s signs should be done.18 A neurologic examination should be done to rule out concurrent cranial nerve, cerebellar, or other neurologic dysfunction that would belie the working diagnosis of a peripheral unilateral vestibular dysfunction.
PREOPERATIVE PATIENT COUNSELING AND INFORMED CONSENT
Preoperative counseling should include a discussion of the natural history of Meniere’s disease, including the spontaneous rate of remission of approximately 70% within 8 years and the 10% to 40% incidence of involvement of the second ear.19 In addition, the patient should be aware that all hearing will be lost in the ear receiving surgery, and that the effect on tinnitus is unpredictable. The patient must be aware that immediately postoperatively there is a period of vertigo similar to a typical attack, and that this episode lasts several days. In addition, a period of protracted dysequilibrium may occur, and in patients with negative indicators for compensation, there may be some degree of permanent disability that requires a rehabilitative program.
