Medical Must-See: The patient who lost his mind - well, part of it

Doctors suspected a stroke but found a hole in their diagnosis

An 84-year-old is entitled to be a little absent-minded, but this CT scan is something else.

The elderly man presented to an ED in Northern Ireland with a history of recurrent falls and left-sided arm and leg weakness.

Doctors initially suspected a stroke, but examination and routine blood testing revealed no obvious abnormalities.

It was only when they ordered a brain CT that a 9cm air pocket was detected within his right frontal lobe.

An MRI confirmed the presence of a pneumatocoele — a pressurised air-filled cavity, known as a tension pneumocephalus when found in the brain — extending from the cribriform plate.

Imaging also revealed the culprit: a large benign osteoma within the ethmoidal air cells. The tumour had eroded the cribriform plate, allowing air to be forced under pressure into the right frontal lobe and restricting blood flow.

The patient was offered a frontal craniotomy to evacuate the air cavity and excise the osteoma. However, he decided agasint surgery given the risks and benefits.

The patient was started on secondary stoke prevention, and on 12-week follow-up, his left-sided weakness had resolved.

Writing in BMJ Case Reports, his treating doctor explained:

A small number of reported cases have been associated with history of ENT pathology, usually an osteoma, causing erosion through the cribriform plate and forcing air under pressure into the brain by creating a ‘one-way valve’ effect.

This often causes the pneumatocoele to grow insidiously over weeks to months. Sometimes it can be precipitated by a more acute event, for example, following a bout of sneezing or coughing. It is a rarely reported complication of frontal sinus osteoma.

More information:
BMJ Case Reports 2018; online.