Radiology #6: Under Pressure

The Patient

A 27 year old male patient presents after being struck in the head with a hammer. He lost consciousness and was taken to a local clinic, where there was no access to CT. Instead, the following plainfilms were taken, and he was then sent to Bara:

The Pictures

What do you think?

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There's a large amount of pneumocephalus visible on both views. He also has a parietal skull fracture which appears depressed and extensively comminuted.

Because there was an associated open wound, he was treated with cefazolin 2g IV q8h. Depressed skull fractures frequently cause seizures, so he was loaded with phenytoin 1g IV and charted continued maintenance doses of 100mg IV q8h. Typically, depressed skull fractures need surgical elevation if they are ≥100% displaced (i.e. depressed by greater than or equal to one skull width) [1], so after CT he was referred to neurosurgery for elevation and debridement.

In this case, there was also a prolonged period of altered consciousness. In the absence of any space-occupying intracranial haematoma, and having persisted too long for it to be post-ictal, the altered mental state was thought to be due to the pneumocephalus itself. This is because - just like a pneumothorax - pneumocephalus can cause tension. This is why patients with pneumocephalus should not fly or ascend to altitude until there's resolution.

Radiologically, tension pneumocephalus is suggested by the presence of the "Mt Fuji sign" [2], which is where the frontal lobes appear peaked due to the bridging veins which tether them to the meninges. Images of this (in two different patients) can be seen here:

Our patient's images were not quite so pronounced, but there is a hint of this sign visible in the AP view on the left. Typically, pneumocephalus itself requires no treatment, and the air will gradually be resorbed over time. Tension pneumocephalus, on the other hand, can require evacuation via burr hole.

An interesting factoid to finish up - in rare cases, patients with pneumocephalus may describe hearing a "bruit hydroaerique" - a splashing noise that occurs with head movement.

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Thanks to Dr Nick Chapman for submitting this case.

References

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[1] Bullock MR, Chesnut R, Ghajar J, et al. Surgical management of depressed cranial fractures. Neurosurgery. 2006;58(3 Suppl):S56-60.

[2] Pillai P, Sharma R, MacKenzie L, et al. Traumatic tension pneumocephalus - two cases and comprehensive review of literature. Int J Crit Illn Inj Sci. 2017;7(1):58-64.