Surgery for Benign Paroxysmal Postitional Vertigo

Background

• Short duration (usually less than 1 – 2 minutes, although it may feel longer)
• Attacks occur suddenly
• Provoked by a specific head movement

Indications for Surgery

Pathophysiology

Ninety percent of cases of BPPV are due to abnormalities in a part of the balance system of the inner ear known as the posterior semicircular canal (The remaining ten percent of cases of BPPV are divided almost equally between the horizontal and superior semicircular canals). The balance system of the inner ear consists of three semicircular canals (horizontal, posterior and superior) and two other balance chambers known as the utricle and the saccule. The semicircular canals sense angular movement of the head such as when the head is tilted from side to side. The utricle and saccule sense linear motion such as that experienced when riding in an elevator. Tiny crystals, present exclusively in the utricle and saccule, are what allow the body to sense linear motion. These crystals are attached to the top of a gelatinous type structure. The semicircular canals, the utricle and saccule are connected to each other through a set of small tubes.

BPPV occurs when these tiny crystals become loose, fall into one of the semicircular canals and become trapped inside the semicircular canal. Once inside a semicircular canal, these crystals are free to float inside the fluid of the canal. The vertigo of BPPV happens when the crystals inside the semicircular canal continue to move even though the head remains still. Vertigo ends when the movement of the crystals inside the canal stops. Since only specific head movements cause these crystals to move, BPPV only occurs when the head is turned into a specific position. A visual analogy is that of a toy “snow globe”, which, when shaken, causes the “snow” particles to float inside the globe (the same events that occur inside the semicircular canal in BPPV when the head is turned into a certain position). The “snow” particles eventually fall to the bottom of the globe by gravity if there is no more movement of the globe (similarly, in less than a few minutes, the vertigo of BPPV subsides when the crystals in the inner ear stop moving).

Testing Prior To Surgery

The diagnosis of BPPV is made based on a characteristic history and a positive Dix-Hallpike test (Dix, Hallpike, 1952). A Dix-Hallpike test is performed in the physician’s office with the patient seated on a table. The physician has the patient lie backwards so that the head hangs slightly below the table with head turned first to one side and then repeated with the head turned to the other side. A positive Dix-Hallpike test involves the finding of a characteristic nystagmus (“eye twitching”) in one or both of the head-hanging positions. In addition, the patient should complain of the subjective sensation of motion when the nystagmus is present. A positive Dix-Hallpike test not only confirms the diagnosis of BPPV, but it also determines which ear and which semicircular canal is involved based on the direction of the nystagmus.

Other testing prior to surgery includes:

• Hearing test (audiogram): for baseline
• MRI of the brain with and without contrast dye: to rule out other causes for positional vertigo
• Videonystagmography (VNG): for baseline evaluation of inner ear balance function

Goals of Surgery