Recurrence of condition is about 2 % in adults. Seizure activity would be a major concern, as drowning would surely ensue if this occurred underwater. Oxygen toxicity would increase this risk.
Scarring from the treatment is said to produce an increased risk for the development of bubbles in areas of altered vasculature, either decreased or increased, an unproven suspicion. Also, we don’t know exactly how the gamma knife works over a period of months to decrease blood flow.
Residual weakness would be of some concern in hindering the diver’s ability to gear up and perform tasks required for safe diving. It might also diminish his ability to self rescue and to rescue his buddy, thereby endangering the entire dive operation. [The degree of disability is of some importance]. Enhanced reaction to nitrogen is a possibility but this is not known.
In addition, the hemiparesis requires careful recorded delineation in order to be able to differentiate between this entity and possible decompression symptoms – should this untoward event occur.
—Risk from the Condition
Depth and pressure should have no effect on the condition. Recurrence of the condition has to be accounted for with the realization that should a hemorrhage occur underwater, the risks are very high for death from drowning.
—Risks from the Treatment
Scarring from the gamma knife would need to be determined by various studies. Foci of altered vascularity could possibly lead to DCS in the area with further diminution in neuronal coverage of the penumbra of injury.
—Risks to the Diver
Chance of a rebleed underwater, minimal but present. Vigorous exercise, lifting heavy weights and using the Valsalva method for ear-clearing when diving all increase arterial pressure in the head and may increase the likelihood of a recurrent hemorrhage. Chance of convulsions, both from the scarring and from the increased propensity for seizures from borderline high oxygen partial pressures at depth. [O2 pp greater than 1.4 ata can lead to oxygen toxicity and seizures].
Advising the Diver
—Potential for injury from future diving
A long time, previously certified sport diver might possibly return to diving with the full knowledge of the potential for injury after an appropriate period to allow for full radiation effect [three years]. A commercial diver should not return to diving for various reasons, namely the depths, strenuous activity and likelihood of decompression diving and liability potentials. However, a new diver or partially trained diver could participate in the sport depending on the degree of disability and appropriate wait for full effect of the focused radiation as determined by MRI studies and angiography.
Degree of disability
Findings on studies and degree of benefit as determined by studies.
History of convulsions or anticonvulsant therapy.
—Dive or not dive
There are several unsubstantiated reports that recommend for cerebral hemorrhage that if there are no convulsions and the person is not taking anticonvulsant medication – then diving may be considered after a wait of three seizure free years. [Parker, The Sport Diving Medical].
If there is a highly motivated individual who is well informed of the risks and is willing to accept these risks – then one might consider allowing low stress diving [shallow diving [60 fsw or above], warm water with little in the way of current, surges or wave action] sooner if the AVM is shown to be stable and asymptomatic. Again, as the effect of the focused radiation on the AVM is realized over many months; blood flow through the AVM should be monitored and retreatment performed if necessary.
It would be wise to avoid all factors that would increase the risks of O2 toxicity (deep diving, Nitrox, rebreathers) because of the possibility of initiating seizures.
The patient should be given enough time to demonstrate that the AVM has fully responded to the gamma knife. Close observation of changes over a several month period are required. Whether or not the full three year wait is necessary should be determined by clinical experience in combination with the MRI, angiograms and the material provided above. There are no studies or guidelines.