Benign paroxysmal positional vertigo of the horizontal canal.
OBJECTIVES: To review the clinical features, electronystagmography findings, the possible mechanism, and a possible therapeutic approach to benign paroxysmal positional vertigo (BPPV). METHODS: Sixty-three cases of BPPV of the horizontal canal type have been reviewed. It is characterised by horizontal nystagmus and an intense vertigo, provoked by rotation of the head in a supine patient. The horizontal nystagmus beats towards the ground on both sides, becomes more pronounced when lying on the pathological side, and then the nystagmus often changes direction. RESULTS: Forty-eight patients underwent electronystagmography. On the pathological side, the first phase nystagmus had a mean latency of three seconds and a mean duration of 31.6 seconds. Nystagmus inversion occurred in 36 patients after a nystagmus free interval. The mean second phase nystagmus duration lasted 33.4 seconds. On the healthy side, the nystagmus had a mean latency of 3.4 seconds and a mean duration of 39.5 seconds. Fatigue was seen in six patients. Simultaneous involvement of the posterior canal was present in 16 patients. A liberatory manoeuvre was successful in six patients. CONCLUSIONS: The liberatory manoeuvre should be tried in patients with horizontal canal vertigo. It should not be performed in patients with severe cervical arthrosis, vertebrobasilar insufficiency, or when the patient has neck pain during the manoeuvre.