A woman with both positional and spontaneous dizziness.

A 40-year-old woman came to the office for evaluation of dizziness of 6 weeks' duration. She also complained of associated headache, which abated with the onset of her menstrual cycle. She said that she had first experienced dizziness during the first few weeks of her earlier pregnancies.

Her latest episodes began as a brief rotary sensation when she turned over in bed. She subsequently noted that dizziness would occur both spontaneously and during other positional changes, but most notably when she turned over from the supine position.

Electronystagmography revealed the presence of a left-beating nystagmus while the woman laid on her right side. A right-beating nystagmus became evident when she turned her neck to the left, but not when she laid on her left side. The alternate binaural bithermal caloric test showed low-velocity responses to stimulation of the right ear (a 36% reduced vestibular response [RVR] on the right) but no directional preponderance according to Jongkees' formula. The simultaneous binaural bithermal test (not shown) revealed a type 2 response consistent with an RVR right.