Occasionally, the cranial gas spaces (mastoid, para-nasal sinuses) are affected by ascent barotrauma, when the expanding gas ruptures into the cranial cavity. This may follow descent barotrauma, when haemorrhage occupies the gas space and its orifice is blocked. The sudden bursting of gas and/or blood into the cranial cavity, usually through the tegmen tympani and the thinned petrous temporal bone into the epidural space, could cause significant brain damage.
The clinical presentation may have all the clinical features of a catastrophic intracerebral event, such as a subarachnoid haemorrhage. Excruciating headache immediately on ascent is probable, although the effects of a space-occupying lesion may supervene. Neurological signs may follow brain injury or cranial nerve lesions.
It is likely that the condition could be aggravated by excessive Valsalva manoeuvres (‘equalizing the ears’) or ascent to altitude (air travel). Diagnosis can be verified by positional skull x-ray study or computed tomography scan (Figure 9.5).
Treatment includes the following: bed rest, sitting upright; avoidance of the Valsalva manoeuvre, sneezing, nose blowing, altitude exposure, or other manoeuvres that increase nasopharyngeal pressures; 100 per cent oxygen inhalation for many hours; and follow-up radiology or scans to verify a reduction of the air volume. If untreated, the disorder may last a week or so, and subsequent infection is possible. On theoretical grounds, recompression or craniotomy could be considered in dire circumstances.
The presence of pneumocephalus, in association with sinus injury in general medicine, has been well recorded by Markham19, and it is one of the dangers associated with sinus barotrauma5. It has been well demonstrated by Goldmann20 (see Figure 9.3).
Pneumocephalus results from the expansion during ascent of gas in a space (mastoid, ethmoidal and sphenoidal sinus) that has been partly occupied by blood and fluid from the descent barotrauma. A rupture into the cranial cavity, with air and/or fluids, produces an excruciating and sudden headache, with the pathological features demonstrated by radiology, CT brain scans or MRI. The temporal bony roof over the sinuses is frequently very thin or incomplete, allowing for the contents of this (air, blood) to rupture into the middle cranial fossa, into the epidural areas21. This condition is not infrequently observed at autopsy when the diver has descended while alive but unconscious, inducing para-nasal sinus barotrauma, and then being brought to the surface, where the gas space has expanded, even though the diver may have died.
Extension of infections following sinus barotrauma and subsequent sinusitis may result in orbital cellulitis, meningitis and other neurological problems.
Orbital haemorrhage may also result from the pressure gradient, with potential vision-threatening ocular complications. Sinus mucocoeles, produced during barotrauma, can also cause space-occupying lesions with neurological sequelae, including optic neuropathy and blindness. Demonstrable on MRI, these disorders require referral of the patient to an ophthalmic surgeon.