The “Twin Peaks” Sign: A Distinct Radiological Sign Suggesting Caution for Pneumocephalus and Anterior Skull Base Fracture in the Setting of Epistaxis after Head Injury

Pneumocephalus is common after neurosurgical and sinus procedures, but also after traumatic skull base fractures. An elderly lady presented after a fall with epistaxis and progressive consciousness decline. CT showed a cribriform plate fracture and severe pneumocephalus involving the extradural, subdural, intraventricular, and posterior fossa compartments. It was postulated the “epistaxis” comprised bloodstained CSF, which allowed air to enter the subarachnoid/subdural space, by means of a dehiscence in the skull base, creating a CSF fistula.

We hereby describe a distinct radiological entity, the “twin peaks” sign, not to be confused with the Mount Fuji sign. In the latter, the frontal lobes are collapsed by pneumocephalus in the convexity of each hemisphere. The significance of the twin peaks sign is twofold: (1) The frontal lobes collapse, like in the Mount Fuji sign, but there is, also air entrapment in the interhemispheric space, which may lead to compression from the center outward as well as to compression from the convexity inward. (2) The separation of the frontal lobes beyond the point of their tips, causing these prominent peaks, is a sign of increased tension. This suggests air pressure is at least greater than the surface tension of CSF between the frontal lobes. Epistaxis in the setting of head injury, whether severe or mild and repetitive, should alert to the possibility of CSF leak and skull base fracture. Progressive neurological decline should prompt investigations to exclude tension pneumocephalus. The twin peaks sign should lead to immediate referral to neurosurgery.