The Mount Fuji sign

A 6 year-old-girl developed decreased responsiveness 12 hours after surgical resection of a pilocytic astrocytoma by posterior fossa craniotomy. Computed tomography of the brain demonstrated the ‘Mount Fuji sign’ (Fig 1). This sign refers to hypoattenuating subdural air that causes compression and separation of bilateral frontal lobes suggestive of underlying tension pneumocephalus and warrants emergent neurosurgical reference.¹

Fig 1.

Axial unenhanced computed tomography images of the brain demonstrates bilateral subdural hypoattenuating areas (*) causing compression of the frontal lobes. Note the widening of the inter–hemispheric space between the tips of the frontal lobes (white arrows) forming the characteristic silhouette of Mount Fuji.