Cerebral abscess and subdural empyema

Case contributed by Matthew Tse
Diagnosis certain


Known base of skull tumor. New pyrexia, new headache, new word finding difficulties, new cranial nerve palsies. CRP 600.

Patient Data

Age: 55 years
Gender: Male

MRI brain


Centered within left anterior inferior temporal lobe, collection of relatively homogeneous low T1 and high T2 signal with relatively thin, regular peripheral enhancement measuring 21 x 30 x 29 mm (TR x AP x CC) and corresponding central diffusion restriction in keeping with abscess. Hyperintense T2 signal of the surrounding white matter in keeping with edema.

Subdural collection with corresponding diffusion restriction in keeping with subdural empyema, extending along the inferior aspect of the left temporal and medial aspect of left temporal, occipital and parietal lobes, measuring up to 8 mm depth on coronal reformats at the inferior temporo-occipital region.

The ventricular system is clear with no evidence of hydrocephalus or pyocephalus.

No other intra-axial space-occupying lesion.
No significant midline shift or herniation.

Enhancing soft tissue mass at the left skull base encasing the left internal carotid artery, soft tissue mass lesion within left external acoustic canal and fluid signal within the left mastoid air cells, overall similar to recent MRI neck.

Enlarged left neck nodes similar to prior.
Right maxillary sinus polyp also similar to prior.

Left temporal lobe abscess with associated left subdural empyema, presumably secondary to eroding left skull base mass, which is similar in size to prior.

Case Discussion

An intra-parenchymal fluid collection with relatively uniform strong diffusion restriction and thin peripheral enhancement is a characteristic appearance for a cerebral abscess; a key feature, in this case, is appreciating the close relationship with the base of skull mass and the likely close association between the mass and the abscess which may make definitive surgical intervention difficult. The other key observation is appreciating the subdural collection and the fact this collection also restricts diffusion in keeping with a subdural abscess (subdural empyema).

The patient initially had the abscess drained, which grew small numbers of Streptococcus intermedius. The subdural collection was too small for neurosurgical intervention initially but subsequent imaging showed enlargement of the subdural collection which was subsequently washed out by neurosurgery, following which inflammatory markers normalized.

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