Cerebral abscess with ventriculitis

Case contributed by Assoc Prof Craig Hacking

Presentation

Intoxicated. Minor trauma (ped v car), no ALOC but headache and vomiting since. Poor historian. Dishevelled, probable IVDU with trackmarks on arms.

Patient Data

Age: 35 years
Gender: Male

Motion artefact degrades image quality.

No acute intra or extra-axial hemorrhage. There is focal hypoattenuation within the right occipital lobe, with asymmetry of the adjacent occipital horn of the right lateral ventricle and mild positive mass effect.

Neuroparenchymal volume and grey-white matter differentiation are elsewhere preserved. Normal CT appearance of the midline and posterior fossa structures.

Unremarkable orbits and globes. Small right frontal scalp hematoma. The imaged paranasal sinuses and mastoid air cells are well pneumatized.

IMPRESSION

  1. No acute intracranial hemorrhage.
  2. Focal hypoattenuation with mild positive mass effect within the right occipital lobe, suspicious for an underlying mass lesion with vasogenic edema. Further evaluation with post-contrast CT is recommended.

Post contrast CT

CT

There is a ring-enhancing centrally hypoattenuating ovoid lesion within the white matter of the right occipital lobe, corresponding to the changes described on the recent non-contrast CT. The enhancing component measures 20 x 12 x 12 mm. There is mild perilesional vasogenic edema and mild positive mass effect, with partial effacement of the occipital horn of the right lateral ventricle.

No further intra or extra-axial space-occupying lesion. No further abnormal focus of intracranial contrast enhancement. No CT evidence of ventriculitis.

The major dominant intracranial arteries and dural venous sinuses opacify normally. 

IMPRESSION

Ring-enhancing centrally hypoattenuating lesion within the right occipital white matter with mild positive mass effect. The differential diagnosis is between a cerebral abscess and neoplasm. MRI with gadolinium is recommended.

Ovoid right occipital lobe white matter lesion measures 14 mm in maximum diameter. The center of the lesion is low T1 signal, reasonably high T2 signal and intermediate signal on FLAIR. There is a slightly irregular rim with immediate T1 signal and low T2 signal. Surrounding vasogenic edema extends to the occipital horn of the right lateral ventricle, where there is dependent debris filling the occipital horn with resultant loss of normal CSF signal intensity. Contrast enhancement at the periphery of the lesion anteriorly becomes contiguous with the thickened and enhancing ependymal lining of the right occipital horn and trigone. Diffusion imaging confirms true restricted diffusion in the center of the lesion as well as the dependent material in the occipital horn. No ventricular dilatation. No significant mass effect or midline shift.

No other focus of signal abnormality is demonstrated. No other pathological contrast enhancement appreciated. Normal flow voids are demonstrated. The dural venous sinuses demonstrate normal contrast opacification.

IMPRESSION

Features in keeping with a right occipital lobe abscess and acute ventriculitis. Neurosurgical team aware of the results.

Case Discussion

The patient was taken to theater and the abscess drained. It grew Aggregobacter aphrophilus and was treated with IV ceftriaxone.

A. aphrophilus was previously classified as Haemophilus aphrophilus and is a Gram-negative coccobacillus, forming part of the HACEK group of bacteria. It is a commensal of the oropharynx and respiratory tract and more commonly produces endocarditis and pneumonia. 

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