If the room spins for a few seconds when you roll over in bed, lie down, or look up to a high shelf, the cause is often BPPV, benign paroxysmal positional vertigo. It sounds alarming, but it is one of the most treatable causes of dizziness.

What is happening

Your inner ear contains tiny calcium crystals that help it sense gravity. Sometimes a few come loose and drift into one of the canals that sense rotation. When you move your head, they keep moving after you stop, and your brain reads that as spinning.

How it is treated

A physical therapist first finds which ear and which canal is involved by watching your eyes as you change position. Then a repositioning maneuver, a series of slow head turns, guides the crystals back to where they belong. Many people feel better after one or two visits.

• Spinning that lasts under a minute and is triggered by head position.

• Worse when rolling over, lying down, or looking up.

• No hearing loss and no other new symptoms.

When it is not BPPV

Dizziness with a sudden severe headache, slurred speech, double vision, weakness, or numbness needs emergency care, so call 911. Constant dizziness that does not change with position also needs a medical check before therapy.