Early rehab, retraining key to vertigo management
Medication must facilitate vestibular compensation--Dr. Lacour
Early vestibular rehabilitation, active retraining, and using a drug that facilitates vestibular compensation are the key to effective treatment of vertigo.
Dr. Michel Lacour, director of the research committee and head of laboratory at Université de Provence in France, stressed these as he outlined six key strategies in vertigo management during a symposium organized by Solvay Pharma. He cited results of recent research in support of a six-point strategy in vertigo management.
"From a clinical point of view, the rehabilitation must be performed early, active training must be instituted including all available sensory cues, and you have to use adequate pharmacological treatment that strongly facilitates the vestibular compensation process," he said. The drug he recommends is betahistine (Serc), which, according to him, increases histamine synthesis and release in the vestibular nuclei to accelerate the vestibular compensation process.
Six commandments of vertigo rehabilitation
Lacour gave six pointers to guide physicians in the treatment of unilateral vestibular lesions.
I. It is better to do vestibular training early.
Lacour cited animal experiments that showed recovery of the equilibrium function following unilateral vestibular injury. In these experiments, a cat was made to walk on a rotating beam after it was subjected to vestibular resection. Just after the injury, the cat was unable to walk even when the beam was stationary. Ten days later, it can walk on the beam
rotating at low speed, and eventually traversed it while rotating at faster speed. Forty to 45 days later, the cat had totally recovered its dynamic function. In the second phase, the cat was placed in a small box such that it was unable to stand, simulating the behavior of patients who stay in bed after vestibular injury. The recovery was delayed and very poor.
II. It is necessary to have active retraining.
In the same animal study, Lacour compared the response of the vestibular-nuclei cell to optokinetic stimulation between a normal cat (control) and the one subjected to unilateral vestibular resection. The study showed that the vestibular-nuclei cell does not respond to static and passive visual stimulation, and no reorganization at this level of the brainstem occurs as a result of these stimuli. But when the cat is allowed to behave normally and given dynamic visual inputs, an experience-induced reorganization takes place.
"The best reorganization occurs when you give dynamic and active retraining with visual input," concluded Lacour.
III. It is preferable to manage the rehabilitation programs according to the patient's reference frames.
Citing their study of 100 patients with Meniere disease who underwent unilateral vestibular neurectomy, Lacour said they found individual differences on the reference for postural equilibrium. The patients were subjected to a postural performance test where they were asked to stand on a platform and maintain their balance with their eyes open or closed. Half of the patients had better performance with their eyes open, the other half with their eyes closed. The first set of patients exhibited a visual strategy while the second showed a proprioceptive strategy in maintaining postural equilibrium.
IV. Test the patient in various environmental contexts.
According to Lacour, if a patient is tested in total darkness, in the light without references to verticality, and in the light with references to verticality, one gets different results. The subjective visual vertical is deviated toward the lesioned side in total darkness and in the light without reference to verticality. However, there is a strong reduction of this deviation among patients who are in a lighted area where there are references to verticality.
V. Train patients not only with postural and oculomotor tests but also in spatial-navigation conditions.
The vestibular system is also involved in spatial navigation. An example of a task that uses this vestibular function is path integration, like using a map to go to a certain place.
VI. It is helpful to give drug treatment.
Behavioral recovery after vestibular lesions may be hastened with drugs, said Lacour, citing an experiment with cats. With early vestibular training alone, it took the cats 45 days after vestibular injury to recover reticular function. But among those given betahistine (50 to 100 mg/kg), recovery was shortened to 15 to 18 days. The period of recovery was reduced by 50 percent with betahistine, indicating that it strongly facilitates recovery after vestibular lesion, said Lacour.
He noted that animal experiments have shown that cats treated with betahistine have an increased expression of HDC mRNA in the hypothalamus and subsequently increased production of histamine. Once released, histamine binds to histamine H3 receptors in the brainstem. This in turn causes depolarization of the vestibular nerve cells and rebalances the activity of both the lesioned and the unaffected vestibular nuclei, subsequently accelerating the vestibular compensation process, recovery of gaze, and postural stabilization.
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