Dizziness in a SCUBA diver.

A 49-year-old, 235-lb man--a SCUBA diver--presented with a 17-month history of vestibular symptoms. His first episode had occurred about 15 minutes after he finished a routine dive. His symptoms included hearing loss and ringing in the right ear, rotary vertigo, an inability to maintain an upright posture, nausea, and vomiting. When his symptoms persisted, he underwent hyperbaric oxygen therapy without beneficial effect. His hearing loss and tinnitus did not abate until 18 hours after their onset, and severe dizziness persisted for more than 2 days. For the next few weeks, he experienced lingering symptoms on moving his head quickly, and then his symptoms eventually disappeared. He continued to dive throughout this period.

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The patient's symptoms returned 5 months prior to presentation, when he experienced less severe dizziness following a dive. The dizziness lasted for a day. He reported no other ear-related symptoms.

At presentation, the patient complained that he did not feel right when he was on a boat, but he denied dizziness, hearing loss, tinnitus, and aural fullness. His family history was noncontributory. Findings on a clinical neurotologic examination were negative except that he experienced a significant amount of difficulty performing the sharpened tandem Romberg test.

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Electronystagmography revealed no spontaneous or positional nystagmus. Alternate binaural bithermal testing revealed no response to the warm and cool stimuli. Ice-water stimulus revealed bilateral hypoactive responses, with less activity on the right (figure 1). The sinusoidal vertical-axis rotation test revealed a borderline low gain at 0.5 Hz, abnormal symmetry to the right at three frequencies, and phases consistent with a peripheral vestibular disorder (figure 2). Audiometric findings were within normal ranges. Otoacoustic emissions were present in both ears, more so on the left (figure 3).

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Computed tomography of the temporal bones detected evidence of demineralized labyrinthine bony capsules such as those that are seen in patients with otosclerosis-like symptoms. The metabolic examination identified hyperlipidemia in all parameters, and the 5-hour glucose tolerance test revealed impaired glucose tolerance. The vitamin D level was in the insufficient category.

The patient was started on a bisphosphonate (risedronate) at 30 mg twice weekly plus a daily calcium supplement with vitamin D, 1,000 IU of vitamin D3, and sodium monofluorophosphate. In addition, he was referred for nutritional counseling to address his metabolic factors.

The patient returned 3 months later, during which time he had made two 30-ft dives without incident. He admitted that he had refused the nutritional counseling. Otoacoustic emissions testing showed a lesser range of the distortion-product otoacoustic emissions in the right ear. Sinusoidal vertical-axis rotation testing showed similar gains and phases, and there was abnormal symmetry only at one frequency. The patient was advised to refrain from SCUBA diving, to remain on his medical regimen, and to see the nutritionist.

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When the patient returned for his second follow-up in another 3 months, he remained neurotologically symptom-free. Sinusoidal vertical-axis rotation testing showed similar gains, a phase lag at only one frequency, and no abnormal symmetry. The otoacoustic emissions had improved over previous tests. His vitamin and mineral supplementation was continued, and etidronate was added to the pharmacologic regimen. The etidronate was prescribed at 400 mg/day for 2 out of every 6 weeks, alternating with risedronate. He was advised to restrict any further SCUBA activity to shallow ([less than or equal to] 20 ft) dives.

Three months later, the patient retuned and reported that he was still neurotologically symptom-free. Since his previous visit, he had made a few 15-ft dives in a pool. He had lost 50 pounds by following the diet prescribed by the nutritionist. Sinusoidal vertical-axis rotation testing showed similar gains, a phase lag at only one frequency, and a phase lead at another frequency. Abnormal symmetry to the right occurred at one frequency. Otoacoustic emissions testing revealed an improved range and amplitude, more so in the right ear. These findings are consistent with a reversal of auditory hair cell activity and peripheral vestibular function. The return of the abnormal symmetry without vestibular symptoms is a reflection of central vestibular mechanisms responding to the reversal, or improvement, in vestibular function. The interval on risedronate was extended by 2 weeks, and the remainder of the medical regimen was continued.

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Four months later, the patient remained neurotologically symptom-free despite having made several pool dives of 20 to 25 feet. He had lost another 10 pounds since his previous visit. Sinusoidal vertical-axis rotation testing showed improved gains, more phase shifts, and less abnormal symmetry to the right. Otoacoustic emissions remained the same in the right ear. The regimen was continued with a 5-week longer interval of the risedronate, bringing the entire cycle to 13 weeks.

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Five months later--and 18 months since his initial presentation--the patient returned and again reported no symptoms. Alternate binaural bithermal testing showed a marked improvement in caloric function compared with the results of the first test (figure 4). Sinusoidal vertical-axis rotation testing revealed normal gains, normal symmetry, and lags at 0.32 and 0.5 Hz (figure 5). Distortion-product otoacoustic emissions testing revealed further improvement and a marked improvement over the initial testing (figure 6). The patient was advised that he could resume his normal SCUBA activities.

This case illustrates a reversible inner ear dysfunction when an etiology is identified and treated. Although the patient's symptoms manifested right after he finished SCUBA diving, they were not directly related to the diving. The absolute barometric pressure of the dive might have been a trigger of the symptoms rather than the cause.

Kenneth H. Brookler, MD, MS, FRCSC