Posterior fossa subdural empyemas from mastoiditis

Case contributed by Derek Smith
Diagnosis certain

Presentation

Multiple falls. Confused, altered coordination.

Patient Data

Age: 70 years
Gender: Male
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bone
window
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bone window
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Axial C+
delayed
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Info

Partial opacification of the left middle ear and mastoid spaces, with a bone defect into the posterior fossa.

Associated collections in the subdural space between the cerebellum and tentorium, crossing the midline and surrounding the dorsal surface. Extension of this collection into the foramen magnum.

Little appreciable enhancement. No pneumocephalus.

Mild generalized volume loss, but no specific supratentorial findings.

Partly opacified anterior paranasal sinuses.

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Gradient Echo
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T2
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T1 C+
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T1
C+
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Info

Abnormal diffusion restriction in these posterior fossa subdural collections, continued into the left mastoid space. More striking peripheral enhancement.

These sequences also better demonstrate the extension into the foramen magnum. There is also enhancing debris with diffusion restriction in the occipital horns suggesting CSF dissemination.

There is also signal change with diffusion restriction in the left cerebellar hemisphere, compatible with parenchymal inflammatory changes.

Case Discussion

When there is a history of recurrent falls and trauma, hypodense collections could be mistaken for chronic subdural hematomas. However, the distribution is atypical for trauma and careful inspection for adjacent bone / sinus changes - as in this case - is important.

MRI is useful to confirm abnormal diffusion restriction in pyogenic collections, and also to demonstrate the extent of abnormal signal.

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