The Mt. Fuji sign is a radiologic finding seen in tension pneumocephalus. Bilateral hypoattenuating collections are seen in the frontal subdural space, which causes compression and separation of the frontal lobes.
Notice the widening of the interhemispheric space between the tips of the frontal lobes which resembles the silhouette of Mt. Fuji.
In tension pneumocephalus, air enters into the cranial vault through disruption of the skull or skull base. Air pressure increases within the subdural space due to a ball-valve mechanism, where air enters into subdural space but egress of air is blocked by an obstruction.
Tension pneumocephalus may occur after surgical evacuation of SDH (2.5-16%), skull base surgery, paranasal sinus surgery, posterior fossa surgery in sitting position, or head trauma.
To diagnose tension pneumocehpalus, CT findings should correlate with clinical signs of deterioration.
“Peaking sign” (compression of frontal lobes without separation of frontal lobes) has also been linked to tension pneumocephalus.
- emergent decompression to alleviate pressure
- drilling burr holes
- needle aspiration
- EVD placement
- administration of 100% oxygen
- closure of dural defects
- careful monitoring for clinical signs of deterioration
- serial CT scanning of brain
This is Mt. Fuji in Japan
Michel, Steven J. “The Mount Fuji Sign.” Radiology 232.2 (2004): 449-450.