Traumatic brain injury (TBI) occurs when an external force causes the brain to move violently within and collide with the skull. This leads to functional problems of varying degrees and durations. Doctors categorize TBI as mild, moderate or severe depending on the alteration in awareness, duration of loss of consciousness, extent of amnesia and examination findings.
Most TBIs result from motor vehicle, sports and combat injuries. The Centers for Disease Control and Prevention (CDC) report that approximately 1.7 million people sustain a TBI each year in the U.S., but as many as 50 percent of these injuries may go unreported. These injuries contribute significantly to deaths and permanent disabilities. About 300,000 combat veterans have suffered TBIs.
Mild TBIs with symptoms that last hours to days are commonly called concussions. Concussions are associated with a temporary loss of awareness or consciousness and an inability to recollect events (amnesia) in the narrow window preceding and/or following the injury. Any person who reports being dazed or disoriented after a blow to the head should be considered to have had a concussion.
Symptoms usually resolve with rest and time, but even mild injuries can have delayed and/or persistent symptoms; this is known as postconcussion syndrome. Problems thinking, diminished energy or agility and difficulty concentrating or retaining new information may linger for days or weeks. Other symptoms may include nausea, vomiting, headache, dizziness, vision disturbances and problems with balance, mood and sleep. The likelihood of chronic problems is higher when the initial trauma is more severe.
Evidence shows that even mild TBI can have more impact on people’s health than previously thought. A period of physical and mental rest is important after the injury to avoid further harm and facilitate symptom resolution. Recovery following repeated concussions is often slower.
TBI and Diving
Divers who report a history of concussion on a dive medical form are required to obtain clearance from a physician. Thus, divers may withhold this information to avoid this perceived unnecessary inconvenience. In addition to asking about a head injury associated with a loss of consciousness within the past five years, the screening form asks about TBI-related symptoms that may have been caused by a concussion.
Physicians who evaluate fitness to dive after concussions are tasked with considering the specific stressors inherent to diving amid a limited body of evidence about TBI and diving. Recurrence of symptoms such as headache and dizziness is common and may compromise a diver’s safety. Such symptoms may also confound the diagnosis of acute diving-related injuries such as decompression illness (DCI).
Mood swings and mild mental-status changes are common after TBI; these can affect a diver’s attention to detail, interpretation of information (e.g., depth, time, etc.), memory and interactions with the diver’s buddy, guide or team. The recovering brain is vulnerable to reinjury and possibly to venous gas emboli. Seizure risk is also a concern, because seizures that occur at depth are generally fatal.
Chronic TBI symptoms usually disqualify divers, but there is growing pressure to lower the barriers to participation for people who have had a mild TBI. With a lack of definitive evidence specific to questions about fitness to dive after TBI, we have assembled a group of experts to provide their views on how the growing body of TBI literature in other areas could be applied in diving medicine.
How might a history of a head injury with loss of consciousness in a (now-asymptomatic) diver affect fitness to dive?
Lin Weaver: TBI is graded at the time of injury as mild, moderate or severe. I will mainly address mild TBI. Equally important to the grade at the time of injury is the potential diver’s condition at the time of the fitness-to-dive evaluation (presumably months to years after the injury). Twenty-two percent of patients who had a mild TBI will have postconcussive symptoms one year later (McMahon et al. 2014).
In general, people who had a severe TBI should not dive. I guess there could be exceptions, made case by case. Some people who had a moderate TBI may make a full recovery, in which case I think it’s OK for them to dive. If they have not recovered, then symptoms may preclude diving, just as persistent symptoms generally preclude diving for people who had a mild TBI. If structural damage is apparent with CT scan or MRI, the person probably should not dive.
A diver with a history of TBI should dive conservative profiles that minimize risk of decompression sickness (DCS). If the diver were to need hyperbaric oxygen therapy, the dose of oxygen might place him or her at an increased risk of seizure. Divers who have had a TBI have consumed some of their cognitive reserve, and getting DCS or arterial gas embolism (AGE) would represent another brain injury, so the outcome would be worse than if they had never had a TBI.
Wayne Massey: Loss of consciousness, which is often difficult to confirm, is cause for concern about more serious problems that may affect the diver.
We usually want to establish diving suitability after a mild concussion. Head injuries that involve loss of consciousness are more worrisome than those that do not, although getting an accurate history from the patient, coach or family is often unreliable. A duration of symptoms that is cause for concern is not well defined in the literature, but all studies agree that an early return to sports participation comes with the risk of a second injury. Following symptom resolution and a normal examination, individuals may return to diving progressively except in cases in which a seizure occurred.
Tony Alleman: Loss of consciousness for more than 30 minutes or amnesia for longer than one hour is considered disqualifying for commercial divers. Returning to commercial diving after a mild TBI is generally acceptable if no changes are present in imaging such as an MRI or CT scan. Brain contusions, hemorrhage and other structural abnormalities are often associated with delayed symptoms such as seizures.
How long after a concussion should divers wait before returning to diving?
Weaver: With a mild TBI and a full recovery, I think diving is OK, but I will break this down somewhat:
- Mild TBI and full recovery within one week: Diving is OK one month later, but it should be conservative and not include decompression.
- Mild TBI and full recovery within one month: The person should not dive for six months.
- Mild TBI and recovery months, but less than one year, later: No diving for one full year after complete symptom resolution.
- Mild TBI and continuing symptoms: The symptoms may be a problem for diving. For example, vertigo and dizziness may be made worse on a boat. Vertigo may cause nausea, which may be incompatible with safe diving. Exposure to cold may make migraines worse. Diving can be a significant stressor, so anxiety and posttraumatic stress disorder (PTSD) are disqualifiers. Cognitive problems may interfere with divers’ ability to interpret their dive computer or follow directions properly. Any drugs a diver takes must be reviewed with specific advice about diving. Any symptoms warrant evaluation by brain-injury and dive-medicine specialists. All diving is not the same. Diving in relatively shallow, clear, warm water without current is very different from cold, rough water with poor visibility. Recommendations for diving should specify the type of diving.
With a mild concussion, when symptoms resolve within one day, diving within a week of resolution is appropriate. If symptoms go on for a month, then diving does not seem wise until after resolution and a period of observation and medical reassessment, especially with any symptoms beyond a headache. Any persistent cognitive symptoms such as poor concentration would require further observation and a conservative return to activity. Rest and good sleep are reported to be helpful. Subsequent neurological evaluation must assess attention, orientation, judgment, insight and memory. A CT scan is almost never helpful; an MRI should be conducted when a clinical examination suggests bleeding in the brain. An electroencephalogram (EEG) should be considered in the event of persistent symptoms.
Massey: When symptoms resolve early I suggest waiting a week, but the longer the symptoms persist, the longer I would delay diving. Symptom duration is important in determining how long one should avoid sports, including diving.
Alleman: From a commercial diving standpoint, staying out of the water for at least six weeks would be recommended, provided that the diver has a normal neurological examination after this delay. From a recreational standpoint, a longer period of time may be considered since the individual is not compelled to dive from a financial standpoint.
Are there any possible benefits of diving for patients with a mild TBI?
Weaver: There is no scientific proof that patients with mild TBI gain improvement by diving.
Massey: I doubt the existence of benefits based on present information.
Alleman: There is no medical literature that supports diving as beneficial for patients with mild TBI.
What are the main fitness-to-dive concerns with TBI?
Weaver: Headaches following mild TBI are common. They can interfere with attention and concentration and sometimes affect vision, which might make reading a dive computer screen challenging.
Massey: One of the main concerns is cognitive impairment, which relates to judgment, awareness and reasoning. Will the diver make mistakes that he or she otherwise would not, and will that affect the diver’s safety?
Seizure risk varies with the degree of injury, but a significant seizure risk would rule out further diving. Whether the risk of a seizure is permanently elevated in the postconcussive state is unknown. It is likewise unknown whether there is a difference in the risk of complex partial, simple partial, generalized, absence and other types of seizures.
Alleman: Restoration of all cognitive function is necessary to return to safe diving. No matter what type of diving is done, all divers need to have good mental faculties when faced with an emergency in the water, whether it is an encounter with marine life or the loss of air/gas at depth. Any impaired response in these situations could be fatal.
What are the minimum medical requirements that must be met by people with a TBI who wish to dive?
Weaver: Tests such as the sharpened Romberg and near point of convergence are relatively sensitive in brain-injured people, but if they are positive, does that mean the diver can or cannot dive? I don’t think these tests suggest a definitive answer to the question. I think whether diving can be endorsed is more a matter of the symptoms, including how they might change during a dive and whether they might somehow increase the risk of a dive emergency.
Regardless, patients who had a moderate or even severe TBI and want to dive should be assessed by brain-injury specialists such as neurologists, physical medicine and rehabilitation specialists, neuropsychologists, psychiatrists and dive medicine specialists.
In the event of penetrating trauma or if injury to the temporal lobe occurred, then seizure risk will be significantly elevated for several years after the injury. A mild TBI brings a slightly elevated risk of seizure, but that risk is low. A diver who has recovered from a mild TBI can probably use nitrox but should perhaps limit their PO2 to 1.3 ATA. That being said, I am not aware of any real evidence about how hyperoxia and prior brain injury affect seizure risk.
Massey: The requirements are an ability to think clearly, no significant anxiety, good attention span, appropriate insight and judgment for training and no physical limiting factors.
Alleman: A normal, thorough neurological examination would be required for a return to diving. Cognitive testing would also be advised. For any history of loss of consciousness, imaging (CT or MRI) should be considered prior to returning to diving.
References
Annegers JF, Hauser WA, Coan SP, Rocca WA. A population-based study of seizures after traumatic brain injuries. N Engl J Med 1998; 338:20-24.
McMahon PJ, et al. Symptomatology and functional outcome in mild traumatic brain injury: results from the prospective TRACK-TBI study. J Neurotrauma 2014; 31(1):26-33.
Meet the Experts
Tony Alleman, M.D., MPH, is board certified in occupational medicine and undersea and hyperbaric medicine. He is the chairman of the Physicians Diving Advisory Committee of the Association of Diving Contractors International and participates on an International Marine Contractors Association committee on diver health. In his practice he performs dive physicals and treats dive-related disorders for commercial divers. He is the past president of the Gulf Coast Chapter of the Undersea and Hyperbaric Medical Society.
Wayne Massey, M.D., is a clinical neurologist and professor of neurology at Duke University Medical Center in Durham, N.C. He gained significant experience treating divers with serious decompression illness as a doctor at the U.S. Navy Hospital in Bethesda, Md. He is a fellow of the American Academy of Neurology and the American College of Physicians and a member of the DAN board of directors.
Lindell Weaver, M.D., is the medical director of hyperbaric medicine at Intermountain Healthcare in Salt Lake City, Utah. He became a diver in 1975, was a U.S. Navy Undersea Medical Officer for two years and became a diving instructor in the 1980s. He has studied hyperbaric oxygen for brain injury for years and played a leadership role in U.S. Department of Defense studies of randomized trials of hyperbaric oxygen for postconcussive syndrome due to war-related mild TBI.
| © Alert Diver — Q1 2017 |