Brain death from meningitis secondary to ear infection

Findings

Initital head / temporal CT: Pneumocephalus along the left falx of unknown etiology. No evidence of intracranial lesion, midline shift, or intracranial hemorrhage. No fracture of the temporal bones. Widening of the left lambdoid suture with well corticated borders, inconsistent with fracture. Fluid is present in the mastoid air cells bilaterally.

Follow-up CT: Unchanged pneumocephalus. Loss of the suprasellar and quadrigeminal plate cisterns consistent with herniation. Decreasing differentiation between the gray and white matter consistent with edema. Fluid again was seen in the mastoid air cells bilaterally.

Nuclear medicine study: No evidence of flow/perfusion to brain either on the early dynamic images or on the delayed images.

Differential diagnosis:
- Skull fracture
- Meningitis

Epilogue: Patient's girlfriend reported he was diagnosed with an ear infection, but did not fill the prescription. After toxicology consult, possiblity of meningitis was raised. While still in ER the second head CT was done which showed changes of diffuse brain hypoxia with cerebral edema and herniation. Examination at this point revealed fixed and dilated pupils with no brainstem reflexes. ICP monitor was placed showing pressure was significantly elevated, unable to be controlled with hyperosmolar therapy. A nuclear medicine scan was obtained and showed no evidence of flow or perfusion to the brain, findings consistent with brain death when taken in correlation with clinical findings.


Diagnosis: Brain death from meningitis secondary to ear infection


Key points

Differential diagnosis of Pneumocephalus
- Traumatic 74%
May be found within any compartment from skull, skull base, paranasal sinus, or mastoid fracture
3% of all skull fractures
8% of all paranasal sinus fractures
- Neoplasm involving sinus 13%
Osteoma, pituitary adenoma, mucocele, epidermoid, paranasal sinus malignancy
- Iatrogenic 4%
Lumbar puncture, craniotomy, craniectomy, ventriculostomy, ICP monitor placement
- Infectious 9%
Rare sequela of gas-producing infection
Typically sinusitis or mastoiditis
- Regardless, pneumocephalus itself is not a problem—what's causing it?

Epidural
- Remains localized
- Air will not necessarily move with changes in head position

Subdural
- Air-fluid levels
- Moves with changes in head position
- Confluent
- Tension pneumocephalus may result in "Mount Fuji sign"—subdural air separates/compresses frontal lobes, creating widened interhemispheric space between frontal lobe tips—mimics silhouette of Mt Fuji.

Subarachnoid
- Multifocal
- Non-confluent

CT: Imaging tool of choice
MRI: Foci of absent signal on all sequences