[Pneumoencephalos: etiology, pathologic significance and diagnosis. Apropos of 13 observations].

Thirteen cases of pneumoencephalos attended at our hospital in a four-year period are reported. All the cases were men; mean age was 47.2 years. The most frequent cause was injury (seven cases) followed by surgical procedures (five cases); in one case, pneumoencephalos was secondary to barotrauma. In the initial period, the most frequent clinical features were impairment of level of consciousness and psychomotor agitation (84%), whereas in the established period, deep coma (Glasgow scale less than or equal to 7) predominated in 69% of patients. Only 16% of patients complained of headache. The most frequent localization of gas was in subdural space (54% of cases) followed by subarachnoid space (23% of cases). Twenty-three percent of patients presented tension pneumoencephalos. With respect to distribution of gas, 53% of patients presented pneumatocele, 38% of patients had pneumoencephalos, and 15% presented a laminar distribution of the gas. Pneumoencephalos is usually associated to a high mortality rate; 53% of our patients died. In the postsurgical group, mortality rate was 60% and in the posttraumatic group, mortality rate was 43%.