Surgery for Benign Paroxysmal Postitional Vertigo (cont.)

Surgical Treatment

Currently, two surgical treatment options are available for patients with BPPV that does not respond to conservative therapy. These two surgical options are known as: posterior semicircular canal occlusion and singular neurectomy. Both procedures carry a small risk of hearing loss. Therefore, these procedures are not performed in cases in which the involved ear is the only, or the significantly better, hearing ear.

Posterior Semicircular Canal Occlusion

Posterior semicircular canal occlusion (also known as posterior canal plugging) blocks most of the posterior canal's function without affecting the function of other parts of the inner ear. Occluding the posterior semicircular canal prevents the trapped crystals from moving inside the canal. If the crystals cannot move, the symptom of vertigo is eliminated.

Posterior semicircular canal occlusion is performed under general anesthesia. An incision is made immediately behind the ear. The incision follows the natural curve of the skin crease where the back of the outer ear meets the skin of the skull. While working under a high-power surgical microscope, some of the mastoid bone behind the ear is removed (mastoidectomy). Removing some of the mastoid is done to expose the bone surrounding the posterior semicircular canal.

Once the bone of the posterior semicircular canal is identified, a small amount of bone in this area is carefully thinned to an eggshell-like thickness. At this time, a laser is used through the thinned bone to partially seal the posterior semicircular canal membrane, which lies deep to the bone. The laser, in effect, “welds” the walls of the membrane together. (Use of the laser has shortened hospital stay and reduced the amount of disequilibrium after posterior semicircular canal occlusion compared to treatment without the laser. [Antonelli, 1996]) After the laser is used, the thinned bone is carefully removed to expose the inner membrane of the posterior semicircular canal. The canal is then tightly occluded with a plug made of bone chips and a naturally occurring gel-like material known as fibrin glue. The bone chips eventually cause bone to grow in a part of the lumen of the posterior semicircular canal, which results in permanent occlusion. After plug insertion, a piece of tissue (known as temporalis fascia obtained from a muscle above the ear) is used to cover and further seal the opened area of the posterior semicircular canal. The skin incision is closed with sutures placed under the skin, which will eventually dissolve. A surgical dressing is kept in place for one to two days.

Hospital stay after posterior semicircular canal occlusion may vary from one to five days. The length of hospitalization depends on the severity of dizziness and unsteadiness that occurs after this procedure. A feeling of unsteadiness may last for several weeks after hospital discharge. Patients may also describe a brief sensation of motion when positive pressure is applied to the ear canal or the area behind the ear. This sensation may last for several weeks.

Vestibular (balance) exercises (also known as Cawthorne exercises) are started as soon as possible after surgery. These exercises speed up the body’s ability to compensate for a loss of balance function in one ear, which occurs after posterior semicircular canal occlusion.

Results

Immediate and lasting relief of positional vertigo is very high, ranging from 93-100% for posterior semicircular canal occlusion (Anthony, 1993; Hawthorne, 1994; Parnes, 1996; Antonelli, 1996). Temporary mixed hearing loss and tinnitus are common after posterior semicircular canal occlusion (Parnes, 1996; Walsh, 1999). Permanent sensorineural hearing loss is very uncommon with reported rates ranging from 0-7% (Parnes, 1991; Parnes, 1996; Antonelli, 1996; Walsh, 1999).

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Singular Neurectomy

Singular neurectomy involves cutting the tiny nerve (singular nerve) that connects the posterior semicircular canal to the balance center of the brain. When the crystals move inside the posterior semicircular canal, a signal is sent along the singular nerve to the brain. The brain interprets this signal as a sense of constant motion and, hence, the body experiences vertigo. If the singular nerve is cut, the brain never receives the signal from the posterior semicircular canal. Movement of crystals in the posterior semicircular canal may still occur after singular neurectomy. Because the singular nerve is severed, however, the patient no longer experiences vertigo.

Singular neurectomy is performed using local anesthesia with intravenous sedation (i.e. “twilight anesthesia”) or general anesthesia. The surgery is performed either through the ear canal or through an incision behind the ear similar to that used for posterior semicircular canal occlusion. The surgical approach is based on the anatomy of the patient’s ear canal (the smaller the canal, the more likely that surgery will be performed from behind the ear). With either approach, the ear drum is elevated, much like rolling up a window shade. The bone around the round window membrane (a membrane that separates the middle from the inner ear) is removed. After this, the bone around the base of the round window membrane is removed in order to expose the tiny balance nerve that innervates the posterior semicircular canal (the singular nerve). The nerve is then destroyed and bone dust is placed in the canal of the nerve to prevent regrowth of the nerve.

The ear drum is replaced, the ear canal is packed with an absorbable foam-like material and, if an incision was made behind the ear, the wound is closed with sutures placed under the skin, which will eventually dissolve. A head dressing is placed for one to two days.

Hospital stay may vary from one to four days. The length of hospitalization is dependent on the severity of dizziness and unsteadiness that occurs after this procedure. The feeling of unsteadiness typically lasts for several weeks after hospital discharge. Postoperative vestibular compensatory exercises are begun as soon as the patient can tolerate head movement.

Results

Immediate and lasting relief of positional vertigo is very high, although somewhat less than that for posterior semicircular canal occlusion with reported success rates of 80-94% for singular neurectomy (Meyerhoff, 1985; Silverstein, 1990; Gacek, 1991). Permanent sensorineural hearing loss has been reported in 3 to 17% (Meyerhoff, 1985; Gacek, 1985; Silverstein, 1990; Gacek, 1991) of cases of singular neurectomy.

References

1. Anthony PF. Partitioning the labyrinth for benign paroxysmal positional vertigo: clinical and histologic findings. Am J Otol. 1993;14:334-342
2. Antonelli PJ, Lundy LB, Kartush JM et al. Mechanical versus CO2 laser occlusion of the posterior semicircular canal in humans. Am J Otol. 1996;17:416-420
3. Dix MR, Hallpike CS. The pathology, symptomatology, and diagnosis of certain common disorders of the vestibular system. Ann Otol Rhinol Laryngol. 1952;6:987-1016
4. Gacek RR. Pathophysiology and management of cupulolithiasis. Am J Otolaryngol. 1985;6:66-74
5. Gacek RR. Singular neurectomy update II. Review of 102 cases. Laryngoscope. 1991;101:855-862
6. Hawthorne M, el-Naggar M. Fenestration and occlusion of posterior semicircular canal for patients with intractable benign paroxysmal positional vertigo. J Laryngol Otol. 1994;108:935-939
7. Meyerhoff WL. Surgical section of the posterior ampullary nerve. Laryngoscope. 1985;95:933-935
8. Parnes LS, McClure JA. Posterior semicircular canal occlusion in the normal hearing ear. Otolaryngol Head Neck Surg. 1991;104:52-57
9. Parnes LS. Update on posterior canal occlusion for benign paroxysmal positional vertigo. Otolaryngol Clin North Am. 1996;29:333-342
10. Silverstein H, White DW. Wide surgical exposure for singular neurectomy in the treatment of benign positional vertigo. Laryngoscope. 1990;100:701-706
11. Walsh RM, Bath AP, Cullen JR et al. Long-term results of posterior semicircular canal occlusion for intractable benign paroxysmal positional vertigo. Clin Otolaryngol. 1999;24:316-323