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PHOENIX, Ariz., May 27 -- Almost like wet dogs shaking their heads, patients with benign paroxysmal positional vertigo are resolving dizziness by a series of directed movements to remove loose calcium crystals from semicircular canals in the ear.

The quick head-positioning treatment was effective for relieving vertigo especially in patients with loose calcium crystals (otoliths) in the posterior-canal, a common form of the disorder, Terry D. Fife, M.D., of the University of Arizona, and colleagues reported in treatment guidelines in the May 27 issue of Neurology.

The most common form of vertigo occurs when a patient looks up or bends over so that otoliths from the macula of the utricle fall into a semicircular canal. Now referred to as canaliths, they move in the semicircular canal eventually deflecting the cupula, resulting in a burst of vertigo and nystagmus.

All of the repositioning maneuvers move these ectopic canaliths from the semicircular canal into the vestibule of the ear where they are absorbed.

There are a number of repositioning maneuvers in use, said Dr. Fife and colleagues, but they lack standardization, the guidelines authors wrote.

So they reviewed all relevant articles from 1996 to June 2006. These included, for example, treatment for posterior-canal disorder and horizontal-canal and anterior-canal disorder.

Among various maneuvers reviewed, the investigators found that for the common posterior-canal disorder, the canalith repositioning maneuver (also called the Epley maneuver) is safe and effective and should be offered to patients of all ages with this form of benign positional vertigo.

The Semont maneuver is "possibly effective," they said, but received only a low recommendation on the basis of a single study.

The relapse rate and second occurrence rate are not fully established, the guideline writers said. Short-term relapse rates range from 7% to nearly 23% within a year of treatment, but long-term recurrences may approach 50%, depending on the age of the patients.

As an example of the positional treatment, the canalith maneuver for right-sided disorder begins with the patient sitting up on a bed or table.

Then, while lying down, the patient's head is held by the therapist in the right head-hanging position for 20 to 30 seconds (steps one and two). In step three, the therapist turns the head 90 degrees toward the unaffected side.

The head is held this way for 20 to 30 seconds before being turned another 90 degrees so that it is nearly in the face-down position (step four).

After 29 to 30 seconds the patient is brought to the sitting up position (step five).

Although the therapist guides the patient through these steps, the patient's head position is key to successful treatment, the investigators said.

The guidelines also evaluated whether activity restriction is needed following treatment and concluded that five of six studies showed no added benefit for post-treatment activity or position restriction, such as sleeping upright and wearing a cervical collar.

For patients treating themselves, home exercises seemed to pose little risk, but evidence was insufficient to show that it is as effective as maneuvers done by a physician or other therapist.

Turning to the efficacy of medication treatment, the investigators said that in the absence of randomized controlled trials, there is no evidence to support a recommendation of any medication in the routine treatment of this form of benign vertigo.

Lack of evidence precluded recommendations for surgical treatment for refractory disorder, they added.

Future studies, they concluded, are needed to clarify the best treatments for the horizontal-canal form of the disorder, they concluded.

Dr. Fife reported that he has received research support from GlaxoSmithKline and estimates that 6% of his time is spent on canalith repositioning. Other authors have received honoraria or research support from BiogenIdec, Pfizer, GlaxoSmithKline, and Boehringer Ingelheim, and Ortho-McNeil.

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