Incidence of Neurological Complications in Recreational Scuba Diving
The incidence of neurological complications in properly performed recreational scuba diving ranges from 0.017% to 0.2% for decompression illness or arterial gas embolism, with neurological manifestations being among the most serious potential complications. 1
Types of Neurological Complications
Decompression Illness (DCI)
- Accounts for approximately 41% of adverse diving events 1
- Occurs due to bubble formation during or after ascent as inert gases (mainly nitrogen) dissolved in tissues come out of solution
- Neurological manifestations include:
- Motor weakness
- Ataxia
- Paresthesia
- Spinal cord injury (particularly lower thoracic region) 2
- Cerebral symptoms (especially with arterial gas embolism)
Arterial Gas Embolism (AGE)
- Results from pulmonary barotrauma during ascent
- Presents with sudden neurological deficits similar to stroke
- Most commonly affects middle cerebral artery or vertebrobasilar distributions 2
- Can cause rapid deterioration, convulsions, and death 1
Risk Factors for Neurological Complications
- Rapid or uncontrolled ascent
- Inadequate decompression stops
- Repetitive dives
- Exercise during or after diving
- Cold exposure
- Pre-existing pulmonary anomalies
- Anatomical shunts (e.g., patent foramen ovale) 3
- Respiratory conditions that increase risk of barotrauma 1
Epidemiology Data
The British Thoracic Society guidelines provide some insight into the incidence rates:
In a review of military diving between 1968-1981, from 706,259 dives:
- 1,174 adverse events were reported (0.17%)
- Decompression illness comprised 41% of these events
- Barotrauma accounted for 22% 1
US estimates suggest:
- 500-600 cases of decompression illness or arterial gas embolism per year
- From an estimated 30 million dives annually
- Overall risk of 0.017-0.2% 1
Fatality rates:
- Estimated at 2.09-2.68 per 100,000 participants (US data)
- In 1995, the British Sub Aqua Club reported 18 fatalities from approximately 3 million dives (0.0006%) 1
Clinical Presentation
Neurological complications may present with:
- Sudden onset of symptoms during or shortly after diving
- Focal neurological deficits (weakness, numbness, visual changes)
- Cognitive impairment
- Ataxia or coordination problems
- Pain (often in joints but can be neurological in origin)
- Progressive symptoms if untreated 2
Treatment Outcomes
- Complete relief of symptoms occurs in 50-70% of divers with decompression illness 2
- 30% have partial relief despite appropriate treatment
- Delay to treatment worsens outcomes, though most divers respond to hyperbaric oxygen even days to weeks after injury 2
- The initial clinical severity is the strongest predictor of poor outcome (odds ratio 2.68) 4
Prevention
- Proper training and adherence to dive protocols
- Appropriate gas mixtures for depth
- Slow, controlled ascent with proper decompression stops
- Avoiding risk factors such as cold exposure and excessive exertion
- Pre-dive medical screening to identify contraindications 3
It's important to note that even when following all safety protocols, neurological complications can still occur in recreational diving, though the risk is relatively low when proper procedures are followed.