Neurologic Complications of Scuba Diving HERBERT B. NEWTON, M.D., Ohio State University Hospitals, Columbus, Ohio Recreational scuba diving has become a popular sport in the United States, with almost 9 million certified divers. When severe diving injury occurs, the nervous O A patient infor- system is frequently involved. In dive-related barotrauma, compressed or expand- mation handout on complications of ing gas within the ears, sinuses and lungs causes various forms of neurologic scuba diving, written injury. Otic barotrauma often induces pain, vertigo and hearing loss. In pulmonary by the author of this barotrauma of ascent, lung damage can precipitate arterial gas embolism, causing article, is provided on blockage of cerebral blood vessels and alterations of consciousness, seizures and page 2225. focal neurologic deficits. In patients with decompression sickness, the vestibular system, spinal cord and brain are affected by the formation of nitrogen bubbles. Common signs and symptoms include vertigo, thoracic myelopathy with leg weak- ness, confusion, headache and hemiparesis. Other diving-related neurologic com- plications include headache and oxygen toxicity. (Am Fam Physician 2001;63:2211- 8,2225-6.) ecreational scuba diving, which is defined as pleasure diving Dive-Related Barotrauma without mandatory decompres- During descent and ascent in the water, the sion to a maximum depth of diver is constantly exposed to alterations of 130 ft, has become a popular ambient pressure. Barotrauma refers to tissue Ractivity in the past 20 years. In the United damage that occurs when a gas-filled body States alone, there are almost 9 million certi- space (e.g., lungs, middle ear) fails to equalize fied divers.1 Although divers are concentrated its internal pressure to accommodate changes along coastal regions, many others dive in in ambient pressure.2-4 The behavior of gasses inland lakes, streams, quarries and reservoirs, at depth is governed by Boyle’s law: the vol- or fly to distant dive sites. Physicians practic- ume of a gas varies inversely with pressure.6 ing almost anywhere in the United States may During descent, as ambient pressure increases, see a patient with a dive-related injury or the volume of gas-filled spaces decreases complaint. unless internal pressure is equalized. If the In general, severe injury and death are pressure is not equalized by a larger volume of uncommon in recreational diving acci- gas, the space will be filled by tissue engorged dents.1-5 The Divers Alert Network1 reports with fluid and blood. This process underlies an average rate of 90 fatalities per year since the common “squeezes” of descent that affect 1980. Each year, between 900 and 1,000 the middle ear, external auditory canal, mask, divers are treated with recompression ther- sinuses and teeth. apy for severe dive-related complications. In many of these patients, one or more of the OTIC AND SINUS BAROTRAUMA major symptoms are neurologic in origin. Barotrauma to the middle or inner ear can The nervous system is frequently involved in occur during the descent or ascent phases of dive-related complications and fatalities.5 the dive and may cause vertigo and other neu- Physicians need to be aware of the broad rologic symptoms.2-5,7 Middle ear barotrauma spectrum of neurologic injuries that can of descent is the most common type of diving occur during dive accidents to ensure early injury and may involve hemorrhage and rup- recognition, accurate diagnosis and appro- ture of the tympanic membrane. Symptoms priate therapy. include the acute onset of pain, vertigo and JUNE 1, 2001 / VOLUME 63, NUMBER 11 www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 2211 neural hearing loss, tinnitus, nausea and eme- Pulmonary barotrauma is the most severe form of sis. The Weber’s test will lateralize to the unaf- barotrauma and occurs during ascent. fected side in this group of patients. Reducing intracranial and perilymphatic pressures through bed rest, head elevation and with stool softeners can help. Surgical exploration may be conductive hearing loss that lateralizes to the necessary for repair of the fistula if conservative affected side during the Weber’s test. In severe treatment is ineffective within five to 10 days cases (usually during ascent), increased pres- (i.e., the symptoms persist or worsen). sure in the middle ear can cause reversible weakness of the facial nerve and Bell’s palsy PULMONARY BAROTRAUMA (facial baroparesis).8 Pulmonary barotrauma is the most severe Vertigo can also be induced if barotrauma form of barotrauma and occurs during differentially affects the two vestibular organs ascent.2-4,9 In accordance with Boyle’s law, as (alternobaric vertigo). The vertigo resolves the ambient pressure is reduced during ascent, after pressure equalization occurs. Treatment gas inside the lungs will expand in volume.6 If of middle ear barotrauma involves deconges- the expanding gas is not allowed to escape by tants (e.g., intranasal oxymetazoline, oral exhalation, the alveoli and surrounding tissues pseudoephedrine), antihistamines, analgesics will tear. The most common cause of pul- and antibiotics (amoxicillin-clavulanate monary barotrauma among recreational [Augmentin] in a dosage of 500/125 mg divers is breath holding. Other causes are three times per day or clindamycin [Cleocin] related to pulmonary obstructive diseases, in a dosage of 300 mg three times per day for such as asthma or bronchitis, which can lead 10 to 14 days) in patients with otorrhea and to the trapping of gas. Several forms of pul- perforation.2,4,7 monary barotrauma can develop, including Inner ear barotrauma also can develop in mediastinal emphysema, subcutaneous em- patients with middle ear barotrauma.2-5,7 A physema, pneumothorax and arterial gas pressure gradient between the perilymph of the embolism. Arterial gas embolism is the most inner ear and the middle ear cavity can occur, dangerous form of pulmonary barotrauma causing rupture of the labyrinthine windows and accounts for nearly one fourth of fatalities (round and oval) and leakage of perilymph per year among recreational divers.3 In addi- into the middle ear (i.e., fistula). Symptoms tion, it is the only form in which neurologic include the acute onset of vertigo, sensori- symptoms predominate over pulmonary symptoms.9 Arterial gas embolism develops when free The Author air enters the pulmonary vasculature and is carried to the heart and arterial circulation.9,10 HERBERT B. NEWTON, M.D., is associate professor of neurology and director of the division of neuro-oncology at Ohio State University Medical Center and Arthur G. A large proportion of air bubbles can reach James Cancer Hospital and Solove Research Institute, Columbus, Ohio. He graduated the brain, occlude blood vessels and cause from the State University of New York at Buffalo School of Medicine and Biomedical stroke-like events. The most common signs Sciences, Buffalo. Dr. Newton received his neurology training at the University of Michigan Medical School, Ann Arbor. He completed a fellowship in neuro-oncology at and symptoms of arterial gas embolism are Memorial Sloan-Kettering Cancer Center, New York City. Dr. Newton is certified by the neurologic (Table 12,4,6,7), although pul- Professional Association of Diving Instructors (PADI) as a DiveMaster and Instructor in monary symptoms may also be present. In dive medicine (PADI 162347) and is a member of the Diver’s Alert Network and the Undersea & Hyperbaric Medical Society. more than 80 percent of patients, symptoms develop within five minutes of reaching the Address correspondence to Herbert B. Newton, M.D., Department of Neurology, Ohio State University Medical Center, 465 Means Hall, 1654 Upham Dr., Columbus, OH surface, but they also can occur during ascent 43210 (e-mail: [email protected]). Reprints are available from the author. or after a longer surface interval. 2212 AMERICAN FAMILY PHYSICIAN www.aafp.org/afp VOLUME 63, NUMBER 11 / JUNE 1, 2001 Scuba Diving Almost two thirds of patients with arterial gas embolism have alterations of conscious- Treatment of arterial gas embolism consists of life support, ness (i.e., coma or obtundation). Seizures, 100 percent oxygen, rehydration and transport to a recom- focal motor deficits, visual disturbances, ver- pression facility. tigo and sensory changes are also common. Spinal cord lesions occur less frequently. Many patients show initial improvement within minutes to hours, secondary to partial clear- Oxygen reduces ischemia in affected tissues ance of air emboli. Magnetic resonance imag- and accelerates the dissolution of air emboli. ing (MRI) may demonstrate focal lesions in Seizures, arrhythmias, shock, hyperglycemia the brain after arterial gas embolism.10 Arter- and pulmonary dysfunction should be ial gas embolism can mimic decompression treated, if present. Recompression therapy sickness, and the presentation of the two syn- should be initiated immediately, using the dromes may be clinically indistinguishable United States Navy (USN) Table 6 algo- (Table 21-5,7-10).2,4,6 Arterial gas embolism and rithm.2-5,10,11 Recompression therapy reduces decompression sickness can develop simulta- the size of air bubbles by increasing ambient neously in some patients. In fact, the air pressure, expedites passage of emboli emboli of arterial gas embolism may act as a through the vasculature and re-establishes nidus, or “seed,” to precipitate decompression blood flow to ischemic tissues. sickness. Therefore, the two syndromes are often described and treated together