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Case report
An adult man with tinnitus underwent MR imaging of the internal acoustic meatuses. There was no previous brain imaging. His inner ear was normal, but T2-weighted axial images showed an extensive cluster of thin-walled, small T2-hyperintense foci of variable shapes in the region of corpus callosum and pericallosal region. A subsequent detailed MR scan of the brain confirmed a large cluster of small oval and curvilinear cystic lesions of cerebrospinal fluid (CSF) intensity, predominantly involving the body and genu of corpus callosum without corpus callosum atrophy. There was superior extension into the periventricular white matter of the frontoparietal region with minimal mass effect to the lateral ventricle (figures 1–4). The differential diagnosis included dilated Virchow-Robin spaces, a cystic neoplasm, non-neoplastic neuroepithelial cysts, parasitic cysts, ventricular diverticula and chronic vascular ischaemic changes. These lesions were isointense to CSF on all sequences, with minimal mass effect, no haemorrhagic content, no contrast enhancement Figure 5, no restricted diffusion and with normal adjacent neuroparenchyma. We considered these to be tumefactive perivascular spaces predominantly involving the body and genu of corpus callosum, as a rare incidental MR imaging finding.
Axial T2-weighted MRI shows a large cluster of cysts of variable sizes, predominantly in the region of corpus callosum and extending into left cerebral cortex. 2 4
Sagittal T2-weighted images confirm the dominant involvement of corpus callosum.1 2
T1-weighted axial images show the cluster of cysts, isointense to cerebrospinal fluid.1–4
Coronal fluid attenuation inversion recovery images show these cysts to be isointense to cerebrospinal fluid and causing mild mass effect on left lateral ventricle.1–4
Coronal T1-weighted postcontrast images show no enhancement of the cyst walls.1 2
Discussion
Virchow-Robin (or perivascular) spaces are normal pial-lined interstitial fluid-filled structures that do not communicate with the subarachnoid spaces.1–3 They characteristically occur along the lenticulostriate arteries in inferior basal ganglia around the anterior commissure. Less commonly, they occur in the midbrain, the subinsular region and the cerebellum.2 3 They typically appear as small oval or linear foci, measuring 2–5 mm, isointense to CSF and with no contrast enhancement or diffusion restriction. They usually remain asymptomatic.1 2
These cysts can enlarge with age and in some patients with vascular risk factors, particularly affecting the basal ganglia, external and extreme capsules, the centrum semiovale and ventral tegmentum.2 4 Dilated Virchow-Robin spaces may be associated with microvascular diseases, but also with trauma, non-vascular dementia, multiple sclerosis and the mucopolysaccharidoses4 Occasionally, they can be very large and mimic cystic neoplasms and encephalomalacia.2–4 Giant Virchow-Robin spaces, in particular those in the inferior basal ganglia and mesencephalothalamic region, can cause mass effect and hydrocephalus. Small Virchow-Robin spaces in characteristic locations are common findings on MR scans. Occasionally, they show abnormal dilatation with mass effect or bizarre multicystic asymmetric appearance at atypical locations, imposing a diagnostic challenge. Interval follow-up imaging helps to confirm their benign nature.
Footnotes
Contributors AKL drafted the manuscript and prepared the figures. PLS reviewed the manuscript.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed. This paper was reviewed by Josh Klein, Boston,
Massachusetts, USA.