Spontaneous extracranial pneumatocele associated with mastoid hyperpneumatization.

Spontaneous extracranial pneumatoceles unassociated with trauma are rare. We report a case of spontaneous extracranial mastoid pneumatocele associated with exuberant pneumatization of the calvarium and mastoid. The patient presented with a compressible bulge over the base of the zygoma and superior to the pinna. Surgical exploration demonstrated a large air sac in continuity with nontraumatic bony defects of the tympanosquamous and tympanomastoid sutures.