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).

Pneumocephalus from sinus barotrauma of ascent.
Figure 9.5 Pneumocephalus from sinus barotrauma of ascent. (a) The x-ray lateral view, showing gas at the vertex. (b) A computed tomography section showing gas anteriorly. (Courtesy of Dr R. W. Goldman.)

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.