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Neuroradiology Case of the Week

Case 243

Leena Ketonen, MD, PhD

Clinical Presentation: A 65-year-old previously normal caucasian woman experienced extubation difficulties and confusion following extensive pelvic and urinary tract cancer surgery. After the initial post-surgical episode of confusion, the neurologic examination was nonfocal. Her EEG was normal.

Imaging Findings: Non-contrast CT of the brain reveals multiple low density lesions throughout the white matter (Fig. 1). The lesions follow closely CSF density and they do not demonstrate calcification.  MR imaging of the brain confirms the presence of  prominent  perivascular spaces (PVSs, Virchow-Robin spaces) that follow the CSF signal in all pulse sequences [Figs. 2A-F).  FLAIR image shows some linear and confluent hyperintensities in the white matter. No contrast enhancement is present. On diffusion-weighted imaging (DWI) the lesions do not demonstrate diffusion restriction.  On T2 image there is no blooming effect. 

Diagnosis: Widespread widening of perivascular spaces (Virchow-Robin spaces)

Discussion: The perivascular spaces of the brain are pial-lined interstitial fluid filled structures that follow the penetrating arteries. On MR and CT images the enlarged perivascular spaces appear as fluid filled spaces most commonly seen in basal ganglia around the anterior commissure. Other common locations include mid-brain, deep white matter, cortex, corpus callosum and cingulate gyrus. When widened, the PVSs in the white matter are difficult to differentiate from other lesions. Occasionally, the PVSs may become strikingly enlarged causing even mass effect [1, 2]. When significantly enlarged, they may mimic neurologic processes such as seen in cystic neoplasm, cystic infarctions, parasitic cysts, non-neoplastic neuroepithelial cysts, ventricular diverticulum and even deposition disorders such as mucopolysaccaridoses [1, 3]. Though the average PVS size is usually 5 mm or less, they occasionally expand and can reach up to several centimeters in size. They may cause focal mass effect and even hydrocephalus. On older patients diffuse and confluent FLAIR and T2 signal abnormality can follow these lesions in the white matter area [4]. These lesions typically spare the cortical gray matter, however, the sub cortical lesions can expand the overlying gyri (Fig. 2A). Large, focal mass effect may be present. MR spectroscopy in adjacent brain tissue is typically normal. The lesions have the tendency to slightly increase by increasing age, otherwise they remain stable. Widespread dilatation of PVSs may look bizarre, especially if they are unilateral.
     Clinical presentation is usually normal and they are discovered incidentally at imaging. A patient may have non-specific symptoms such as headaches.
     Until 2005 only scattered case reports of ultimate widening of perivascular spaces and giant tumefactive PVSs have been reported.

References:

1. Salzman KL, Osborn AG, House P, Jinkins JR, Ditchfield A, Cooper JA, Weller RO. Giant tumefactive perivascular spaces. AJNR Am J Neuroradiol. 2005 Feb;26(2):298-305. [Medline]
2. Papayannis CE, Saidon P, Rugilo CA, Hess D, Rodriguez G, Sica RE, Rey RC. Expanding Virchow Robin spaces in the midbrain causing hydrocephalus. AJNR AJNR Am J Neuroradiol. 2003 Aug;24(7):1399-403. [Medline]
3. Osborn A [et al.]: Diagnostic Imaging. Brain. Book. AMIRSYS Inc. Salt Lake City,Utah, 2004. I;7;24
4. Ogawa T, Okudera T, Fukasawa H, Hashimoto M, Inugami A, Fujita H,Hatazawa J, Shimosegawa E, Noguchi K, Uemura K. Unusual widening of Virchow-Robin spaces: MR appearance. AJNR Am J Neuroradiol. 1995 Jun-Jul;16(6):1238-42. [Medline]