Brain capillary telangiectasia – Usually a do-not-touch lesion

A 32-year-old woman with a history of migraines and symptoms consistent with rebound headaches.

On MRI, there is a low T1 and high T2 signal lesion in the left posterior corona radiata. There is a central tubular structure running parallel to the long axis of the lesion. There is a low signal seen on the gradient echo T2 images. Post gadolinium agent, the lesion demonstrates faint stippled enhancement. There is no evident mass effect with no midline shift or hydrocephalus. This is in keeping with a brain capillary telangiectasia with a central vascular structure, the latter in keeping with an associated developmental venous anomaly.

Background

Brain Capillary telangiectasias (BCT) are small, low-flow vascular lesions with otherwise normal brain tissues. Prevalence is 0.4% to 0.7% [8]. They consist of dilated capillaries interspersed with normal brain tissue, featuring a thin endothelial lining but lacking vascular smooth muscle or elastic fibres. Histologically, they can sometimes be mixed with elements of cavernous venous malformations [2]. However, the main difference is that cavernous venous malformations do not contain normal brain tissue within their boundaries [1]. BCT is well known to be associated with cavernous malformations, developmental venous anomalies and arteriovenous malformations, suggesting that these lesions may be on the same pathological spectrum [8].

Clinical Perspective

Most capillary telangiectasias are entirely asymptomatic and are found incidentally on MRI scans taken for unrelated reasons. When symptomatic, it can cause headaches, double vision, dizziness, hearing loss, and uncoordinated movements. Intracerebral haemorrhage is a rare complication of capillary telangiectasia, potentially causing headaches, weakness, paraesthesia, hyperreflexia and paralysis. Additionally, capillary telangiectasia can be part of a combined vascular deformity of the brain, often associated with cavernous or arteriovenous malformations. In such cases, significant complications like haemorrhage, stroke, aphasia, loss of vision, unsteadiness that may be severe, and hydrocephalus may occur [3]. Interestingly, in one study where they resected five capillary telangiectasia which had bled, four had other features of other vascular malformations [8].

Imaging Perspective

Capillary telangiectasias are not usually visible on CT. On MRI they may be of low T1 signal and high T2 / FLAIR signal and can be very subtle on these sequences. Blood-sensitive sequences like susceptibility weighted imaging (SWI) or gradient echo T2 (GRE T2*), will show blooming (low signal) of the lesion. There is no mass effect by the lesion. When contrast is given, there is a mild enhancement, and they may have a stippled appearance. The majority are in the pons; however, they can also be in the cerebral hemispheres, cerebellum and elsewhere in the brainstem [4–7].

Outcome

Treatment is typically unnecessary for capillary telangiectasia, as the condition is usually asymptomatic. Additionally, the abnormality is often located in the pons region of the brainstem, making treatment impractical. Provided there are characteristic imaging findings, routine follow-up is unnecessary [3].

Teaching points

This condition should not be mistaken for tumours. Tumours would not exhibit all these three features, namely (1) no mass effect, (2) subtle on standard T1 and T2 weighted imaging, and (3) blooming (low signal) involving the whole lesion, whereas capillary telangiectasias characteristically exhibit all three.