Vertigo: a sensation of instability in which the person feels that they or their surroundings are moving or rotating.
Posterior canal benign paroxysmal vertigo (BPPV).
What is BPPV?
BPPV is a syndrome characterised by episodes of vertigo, which last for approximately 1–60 seconds; are related to rapid changes in head position, particularly movements related to gravity and those involving neck extension (lying down in bed, reaching up for high objects, bending over); and may be associated with nausea and vomiting for up to several hours.
BPPV is believed to be due to debris (canaliths) in the semicircular canals of the ear. Canaliths may continue to move after the head stops moving, with stimulation of the vestibular nerve leading to vertigo.
BPPV symptoms usually resolve spontaneously within 12 weeks, but may persist for up to several months. Attacks tend to occur in clusters and symptoms may recur, following periods of apparent remission.
What causes BPPV?
Although most cases are unexplained, BPPV is associated with head trauma, vestibular neuritis, vertebrobasilar ischaemia, labyrinthitis, middle ear surgery and periods of prolonged bed rest.
How is BPPV confirmed?
Posterior canal BPPV is confirmed by a positive Dix-Hallpike positional test (Hallpike manoeuvre), with unequivocal features of positional nystagmus. The test is not positive in patients with anterior and horizontal semicircular canal BPPV, both of which are much less common.
A positive Dix-Hallpike positional test provokes vertigo and nystagmus when a patient is moved from a sitting position to lying, with the head tipped 45 degrees below the horizontal, 45 degrees to the side and with the side of the affected ear (and semicircular canal) downwards. The nystagmus typically has a latency of a few seconds before onset and fatigues after approximately 30 to 40 seconds. The nystagmus is rotatory with the fast phase beating towards the lower ear (geotropic) and adapts with repeated testing. Optic fixation (when the eyes are fixed on a specific object) may reduce the severity of the nystagmus.
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