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Neuroradiology Case of the Week

Case 49

Ravinder Sidhu, MD, Akio Hiwatashi, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 38-year-old female presented with right-sided weakness of six days duration. Imaging studies did not reveal any explanation for the weakness but an incidental finding was discovered which would be discussed in this chapter.

Radiological Findings: Non-contrast head CT showed a small calcification in the inferior aspect of left caudate nucleus (Fig.1A). Contrast enhanced CT showed revealed faint enhancement surrounding the calcified speck.Ther was no midline shift or mass effect(Fig.1B). Axial T1- weighted MR images were unremarkable (Fig.2A). However, post contrast T1- weighted images confirmed the blush in left caudate nucleus region (Fig.2B). MR venography and angiography did not reveal early draining vein or artery.

Diagnosis: Capillary telangectasia

Discussion:
Clinical Discussion: Cerebral vascular malformations frequently are classified as --

1. Arteriovenous malformations
2. Venous malformations
3. Cavernous malformations
4. Capillary telangectasia

    The imaging features of first three types have been well described in the literature and these lesions can be reliably distinguished on the basis of MR features. Capillary telangectasia have been radiographically occult, however contrast enhanced MR studies with gradient echo sequences are fairly specific [1,2].
    Capillary telangectasia are small areas of abnormally dilated capillaries with otherwise normal brain tissue. They have been described throughout the brain, however pons is the most classical location. Capillary telangectasia represent 16-20% of all brain vascular malformations, however autopsy series estimate the prevalence of capillary telangectasia to be around 0.4%, although they may not be visible on imaging studies. They can occur at any age without specific sex/race predilection. Most of them are asymptomatic but have been associated with minor symptoms such as vertigo, headache and dizziness. Rarely, they may present with hemorrhage [3].

Imaging Discussion: Capillary telangectasia are occasionally visible on dynamic contrast enhanced CT scans. CECT may show subtle area of enhancement. Rarely, tiny specks of calcifications may be seen on plain scan as seen in index case.
    Contrast enhanced MR characteristically shows brush/lacelike enhancement without any mass effect. T2-weighted images may not show significant signal alteration, however, occasionally increased signal intensity may be seen on T1-weighted images [4].
    Lee et al. evaluated 18 patients of capillary telangectasia and found enhancement in all patients with little or no abnormal signal intensity on T2-weighted images [5].
    Gradient echo sequences are useful in cases of capillary telangectasia associated with hemorrhage. Angiography (MRA, CTA, conventional angiography) is not indicated since these are typically angiographically occult.
    The differential diagnosis of such an enhancing pontine lesion includes infection, infarction, demyelinating lesion, neoplasm, or rarely central pontine myelinosis. However, absence of mass effect or significant T2 prolongation are important indicators favoring for vascular lesions.
    However, it is important to remember as in absence of histopathological findings, as well as not knowing about their association with increased risk of hemorrhage or development of cavernous angioma, these patients should be kept on follow up MR.

References:

1. Awad IA, Robinson JR, Mohanty S, Estes M. Mixed vascular malformations of the Brain: clinical and pathogenetic consideration. Neurosurgery 1993; 33:179-188.
2. Gomori JM, Grossman RI, Goldberg HI, Hackney DB, Zimmerman RA, Bilaniuk LT. Occult cerebral vascular malformations; high-field MR imaging. Radiology 1986; 158:707-713.
3. Osborn AG. Diagnostic Neuroradiology. Mosby Editions 1994; 309-311.
4. Barr RM, Dillon WP, Wilson CB. Slow-flow vascular malformations of the Pons: Capillary Telangectasia? AJNR 1996; 17(1):71-78.
5. Lee RR, Becher MW, Benson ML, Rigamonti D. Brain capillary telangectasia: MR Imaging appearance and clinicopathological findings. Radiology 1997; 205(3):797-805.