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.