Vestibular findings in a 62-year-old woman with dizziness and a type I Chiari malformation.

A 62-year-old woman presented with a chief complaint of dizziness. The dizziness had begun 2 months earlier, when she was awakened at 2 a.m. "with everything spinning." The spinning feeling intensified when she turned onto her right side. This initial episode lasted for 15 minutes. After the feeling had subsided, she arose to go the bathroom and she felt unstable, and the spinning feeling returned for approximately 5 minutes. When she returned to bed, she noticed that the feeling would recur when she turned to the right. This entire episode lasted approximately 1 hour.

When she awoke in the morning and attempted to get out of bed, the spinning returned for 15 minutes. Later that morning, she bent to pick tip an article from the floor and the feeling returned; it disappeared when she straightened tip. She later experienced a 5-minute recurrence when she came out of the shower.

She was prescribed meclizine every 4 hours while awake, and the dizziness cleared up in 4 days. However, it recurred after another 4 days. Diphenhydramine was substituted for meclizine, and the symptoms disappeared in 2 days.

The patient reported no subjective hearing loss, tinnitus, or aural fullness. She did, however, note a 1-year history of a feeling of pressure in the back of her neck. Otherwise, her personal and family history and a review of systems were noncontributory.

Magnetic resonance imaging detected a type I Chiari malformation. A clinical examination revealed that the patient experienced difficulty performing the sharpened tandem Romberg test with the right foot forward. Her corneal sensation on the left was diminished, as was her sensation of light touch in the second division of the trigeminal nerve on the left. There were also some left cerebellar signs.

Electronystagmography elicited no spontaneous, positional, or neck-torsion nystagmus. The alternate binaural bithermal caloric test yielded a normal reduced vestibular response and directional preponderance. On closer examination of the individual responses, a relatively reduced warm response on the right was noted. The simultaneous binaural bithermal caloric test elicited a type 3 response with right-beating nystagmus on both cool and warm simultaneous stimuli. This response indicates an abnormality of the vestibular system, as does an abnormal directional preponderance, but it has no localizing value in identifying the side or whether the problem is central or peripheral. Ocular fixation suppression of caloric-induced nystagmus was present.

Findings on audiology were normal, but auditory brainstem-evoked potentials indicated a delay of wave V bilaterally; waves up to wave III were normal bilaterally.

Imaging of the temporal bones showed evidence of otic capsule otosclerosis. A 5-hour glucose tolerance test revealed a hypoglycemic response of 25 mg% at 2 hours. The patient was prescribed a bisphosphonate, calcium carbonate, vitamin D, and a hypoglycemic diet.

The patient returned for follow-up 3 months later. She said the dizziness and neck pressure had disappeared and that she felt more energetic.

This case is an example of a coexisting central nervous system disorder and a peripheral vestibular disorder. It would be easy to attribute the patient's symptoms to the Chiari malformation based on the electronystagmographic and evoked-potential findings. But the presence of ocular fixation suppression, the imaging of the temporal bones, and the metabolic evaluation led to a diagnosis that in the final analysis was effective in identifying the source of her symptoms and successfully treating it.

Kenneth H. Brookler, MD

From Neurotologic Associates, PC, New York City.