Describe benign paroxysmal positional vertigo with its diagnosis and treatment.

Nature and Pathogenesis

• Benign paroxysmal positional vertigo (BPPV) is brief vertigo provoked by a change in head position, caused by displaced otoconia from the utricle entering a semicircular canal.
• It is the commonest cause of vertigo of all, and is curable in one visit.
• The mechanism follows from one fact: the cupula normally has the same specific gravity as endolymph, so it is not affected by gravity and the canals respond only to rotation. Otoconia are denser — so once they enter a canal, gravity begins to move the endolymph and the canal becomes gravity-sensitive

Diagnosis and Treatment

• The DIX-hallpike manoeuvre is the diagnostic test for posterior canal BPPV, and it must be performed properly:
• Sit the patient upright, turn the head 45 degrees toward the side being tested, then lie them rapidly supine with the head extended 20 to 30 degrees below the horizontal, maintaining the head turn, and observe the eyes for at least 30 seconds
• The positive response has five characteristics, all of which should be present: a latency of 5 to 20 seconds; upbeating and torsional (geotropic) nystagmus, the upper pole of the eye beating toward the lower (affected) ear; a duration under a minute; reversal of the nystagmus on sitting up; and fatigue on repetition
• The vertigo accompanies the nystagmus, and the patient should be warned beforehand that the test will provoke it, or they will resist
• Contraindications to Dix-Hallpike — cervical spine instability, severe cervical spondylosis, recent neck injury, carotid disease and severe cardiac disease; the side-lying (Semont) test is an alternative
• The supine roll (Pagnini-McClure) test diagnoses lateral canal BPPV, in which the nystagmus is horizontal and lasts longer: geotropic (beating toward the ground) indicates canalolithiasis, and apogeotropic indicates cupulolithiasis, with the affected side being that with the more intense response in geotropic disease
• Treatment IS a particle repositioning manoeuvre, and it is curative in a single session in the majority — which makes BPPV one of the most satisfying conditions in medicine to treat
• The EPLEY manoeuvre for the posterior canal moves the otoconia around the canal and back into the utricle through a sequence of four head positions, each held until the nystagmus settles
• The SEMONT (liberatory) manoeuvre is an alternative, using a rapid movement from one side-lying position to the other
• The barbecue (Lempert) roll for the lateral canal, rolling the patient through 360 degrees toward the unaffected side
• BRANDT-DAROFF exercises are performed by the patient at home, and are used for residual symptoms or where manoeuvres have failed; they are less effective than a properly performed Epley
• Drugs DO not treat BPPV.
• Post-manoeuvre restrictions (sleeping upright, avoiding head movement) were formerly advised but are not supported by evidence and are no longer recommended
• Prognosis — excellent, but recurrence occurs in up to half within a few years, so the patient should be told this and taught to recognise it; and self-treatment can be taught to those with frequent recurrences
• When BPPV does not respond, reconsider the diagnosis — central positional vertigo from a posterior fossa lesion produces downbeating nystagmus with NO latency and NO fatigue, and requires imaging
• Turning over in bed is close to pathognomonic, and is the single most useful line in the history
• Attacks last seconds, never minutes, though patients feel unwell for longer afterwards and report the whole period
• Auditory symptoms suggest another diagnosis; BPPV causes no hearing loss, tinnitus or fullness
• The posterior canal is the most dependent, which is why it is affected in the great majority of cases
• Head injury often causes bilateral BPPV, and is the commonest identifiable cause
• Warn the patient before Dix-Hallpike that it will provoke the vertigo, or they will resist and the test will fail
• Observe for at least thirty seconds, since the latency may be up to twenty and a brief look will miss the response