A female diver surfaced from a 80fsw dive and experienced back pain and nausea. She was administered oxygen but soon experienced weakness and a “pins and needles” feeling in both legs. She received hyperbaric oxygen (HBO) treatment almost two days later when she returned home. After three sessions in the chamber, she still has lingering symptoms in her legs. Decompression injury of the spinal cord is suspected.
I am a 48-year-old woman weighing 130 pounds; I have 96 lifetime dives — 12 of which have occurred in the past 12 months. The incident occurred on my twelfth dive in a six-day dive series — the first dive of the day. The dive was to 80 fsw (24 msw) for roughly 35 minutes. After surfacing and taking the boat back to shore, I carried my tank up a small hill to the dive shop. Shortly afterward I experienced pain in my shoulder blades, followed by nausea. I was given oxygen as I reclined in a hammock at the dive shop.
I was really uncomfortable in the hammock and wanted to go inside the dive shop where there was an easy chair. When I tried to get up, I could not move my legs or wiggle my toes. I had a pins and needles feeling along both legs. After about 45 minutes on oxygen I regained the use of my legs, but I still had some numbness in both legs. The doctor on the island did not identify the problem as decompression illness and simply advised me to rest.
Upon returning home to North America a day and a half later, the numbness had not improved, so I sought medical attention and was treated in a decompression chamber. The first treatment session lasted about five and a half hours; later the same day I had another three-hour session. The following day I had an additional three-hour session. After the second session I no longer felt any numbness in my left leg. However, I was still experiencing numbness in my right leg, which is why we did the third treatment. The numbness has not resolved; after about one month the numbness started changing to nerve pain — a burning, tingling sensation, with some loss of sensitivity to heat and cold.
Nothing has changed with my right leg in the past year. I have seen a neurologist and recently had an MRI on my spine and brain. The MRI did not show any abnormalities. The neurologist gave me a new prescription to try for the pain and said it could take a long time to heal.
I was tested for a patent foramen ovale (PFO), and the results were negative. I’ve done 22 (very conservative) dives since the incident. Fortunately, diving has no effect on my leg at all; it feels no different during or after dive.
The symptoms described by this diver are very likely caused by decompression injury of the spinal cord. A dive to 80 fsw for 35 minutes can produce a significant amount of venous gas bubbles, especially if it is a near square dive. Venous bubbles can contribute to spinal cord injury as has been shown in an animal model of decompression sickness, but circulating bubbles are not necessary for it. In this case, the symptoms started with nausea and pain between the shoulder blades, which could have reflected venous gas bubbles flooding the pulmonary circulation. Muscular weakness of the legs (paraparesis) with the feeling of pins and needles (paresthesia) that followed, indicated spinal cord injury.
These symptoms may rarely resolve on their own, but there is nothing at the time of symptom onset to indicate that it will have a favorable evolution, and it should be treated as an emergency.
The use of oxygen first aid increases the probability that symptoms will resolve and should be started as soon as possible. Even in cases with complete resolution, symptoms may return; standard treatment with recompression in a hyperbaric chamber and hyperbaric oxygen therapy (HBOT) should follow.
In this case, symptoms improved but did not resolve completely after 45 minutes of breathing oxygen. Breathing oxygen for a longer time could have helped. The HBOT was administered a few days later and resulted with additional improvement, but some symptoms have remained. Minor residual symptoms have been reported in up to 70 percent of spinal cord decompression injuries. It is not possible to tell whether an earlier application of HBOT would have achieved a complete resolution. The persistent pain that remained in this case is not a minor distraction, but this diver has been able to cope with it and even to continue diving.
Muscular leg weakness after a dive should always be treated as an emergency, and divers should receive a full neurological evaluation, first aid oxygen and evacuation to the nearest emergency room, where proper steps can be taken to ensure timely treatment and the best possible outcome.
Petar Denoble, MD, D.Sc.