Giant tumefactive perivascular spaces

Abstract

Background and purpose: The brain perivascular spaces (PVSs) are pial-lined, interstitial fluid-filled structures that accompany penetrating arteries. When enlarged, they may cause mass effect and can be mistaken for more ominous pathologic processes. The purpose of this study was to delineate the broad clinical and imaging spectrum of this unusual condition.

Methods: Thirty-seven cases of giant PVSs were identified from 1988 to 2004 and were retrospectively reviewed. Clinical data collected included patient demographics, presenting symptoms, and follow-up. Histopathologic data were reviewed when available. Images were evaluated for size and location of the giant PVSs, associated mass effect, hydrocephalus, adjacent white matter changes, and contrast enhancement.

Results: There were 24 men and 13 women with an age range of 6-86 years, (mean 46 years). The most common presenting feature was headache (15 patients). Thirty-two cases had multilocular clusters of variably sized cysts. Five lesions were unilocular. All lesions had signal intensity comparable to CSF and did not enhance. The most common location for the giant PVSs was the mesencephalothalamic region (21/36). Fourteen were located in the cerebral white matter; two were in the dentate nuclei. Nine giant mesencephalothalamic PVSs had associated hydrocephalus, which required surgical intervention.

Conclusion: Giant tumefactive PVSs most often appear as clusters of variably sized cysts that are isointense relative to CSF and do not enhance. They are most common in the mesencephalothalamic region and may cause hydrocephalus. Although they may have striking mass effect, giant PVSs should not be mistaken for neoplasm or other diseases.

Fig 1.

Coronal anatomic diagram depicts multiple bilateral giant perivascular spaces (PVSs) in the mesencephalothalamic region. There are fenestrations of the giant PVSs, which may allow accumulation of interstitial fluid between the vessel and pia or within the interpial space causing enlargement of the PVSs. Note the mass effect upon the third ventricle with associated obstructive hydrocephalus. Graphic courtesy of James Cooper, MD and AMIRSYS, Inc (35).

Fig 2.

Axial T2-weighted (A), postcontrast axial T1-weighted (B), and postcontrast coronal T1-weighted (C) images obtained in a 46-year-old man with headaches show a nonenhancing multiloculated cystic mass in the right midbrain, thalamus, and right medial temporal lobe. The cysts follow CSF signal intensity on all pulse sequences and do not enhance. Follow-up imaging 13 years later showed no change. Biopsy proved pial-lined giant perivascular spaces.

Fig 3.

Coronal postcontrast T1-weighted image obtained in a 56-year-old woman with headaches shows a nonenhancing unilocular giant perivascular space (black arrow) in the left thalamus with compression and displacement of the third ventricle (white arrow). Note associated hydrocephalus. Surgery disclosed a smooth walled cyst with no abnormality in the adjacent brain. The patient initially underwent a cyst fenestration with a decrease in the size of the PVS. Four months later, there was reaccumulation of fluid and the PVS enlarged to its original size. A ventriculoperitoneal shunt was then placed, which relieved the hydrocephalus. Follow-up studies showed no change in cyst size over 4 years.

Fig 4.

Sagittal T1-weighted (A), axial FLAIR (B), and coronal T2-weighted (C) images obtained in a 71-year-old man with dementia show extensive involvement of the hemispheric and subcortical white matter with multilocular giant perivascular spaces. The coronal image shows the marked asymmetry of the lesions. Note the scattered focal white matter changes surrounding some of the lesions (black arrows) seen best on the FLAIR image. Case courtesy of Anthony Doyle, MD.

Fig 5.

Sagittal T1-weighted (A), axial FLAIR (B), and axial T2-weighted (C) images obtained in a 46-year-old woman with a visual field defect show extensive involvement of the corpus callosum and cingulate gyrus (A, white arrow) with extension to the subcortical white matter of the parietal and occipital lobes. There is slight increased signal intensity surrounding the lesions, best seen on FLAIR image (B, white arrows). The gray matter is stretched and displaced over the multiloculated giant perivascular spaces. Case courtesy of Leena Valanne, MD.

Fig 6.

Images obtained in a 37-year-old man with headaches. Axial T2-weighted (A) and axial FLAIR (B) images show diffuse, confluent white matter hyperintensity surrounding the giant perivascular spaces. There is mild gyral expansion over the perivascular spaces. The diffusion-weighted image (C) shows no diffusion restriction.

Fig 7.

Images obtained in a 6-year-old boy with a history of minor trauma. Axial T1-weighted (A), coronal T2-weighted (B), axial FLAIR (C) and postcontrast coronal T1-weighted (D) images show multiloculated giant perivascular spaces in the left dentate gyrus. There is mild focal mass effect upon the fourth ventricle (white arrow). The clustered cysts follow CSF on all pulse sequences.

Fig 8.

Images obtained in a 35-year-old man with headache who underwent a biopsy and a third ventriculostomy procedure. Axial T1-weighted MR image (A) shows the giant perivascular space in the left midbrain. A section through the cyst wall (B) shows red-stained collagen in the leptomeninges on the outer aspect of the cyst wall coating the underlying brain tissue that forms the bulk of the cyst wall. No lining of pia matter is present on the inner aspect of the cyst. (Hematoxylin van Gieson stain, original magnification ×20) There is extensive gliosis in the cyst wall as demonstrated by the numerous brown stained fibrillary processes within the brain tissue (C). (Immunocytochemistry for GFAP, original magnification ×20) A high-power view (D) of the cyst wall near the pia arachnoid outer coating (top of picture). Reactive astrocytes are seen toward the bottom of the illustration. No neurons were identified. (Hematoxylin and eosin stain, original magnification ×40)