Fig. 1.3–15a, b Cavernoma. (a) The axial T2-weighted MRI sequences show a focal lesion in a deep parietal location on the left alongside the lateral ventricle, with a center formed by bright and dark points (“popcorn”), surrounded by a dark ring (hemosiderin deposits). (b) The hemosiderin-sensitive T2* gradient echo sequences, now with a coronal section, confirm the presence of blood breakdown products as dark signal losses.
1.3.3.2 Capillary telangiectasia
Capillary telangiectasia is another intracerebral vascular malformation with a cavernous venous structure. In contrast to cavernomas, however, the vessels are diffusely embedded in the cerebral parenchyma. These malformations are usually observed incidentally in the brainstem, thalamus, or basal ganglia during MRI examinations. There are no clinical symptoms associated with them. In individual patients with intracerebral bleeding, it has been debated whether this finding is coincidental or whether it occurs in combination with another vascular malformation that is not visible on imaging, such as a cavernoma or AVM.
On MRI, T1-weighted and T2-weighted images are usually normal, or only show discrete signal changes. Hemosiderin-sensitive sequences show slight signal fading, but not as marked as in cavernoma. After contrast administration, there is signal enhancement of small, striate vessels or of an extensive area, with no perifocal edema and no space-occupying characteristics (Fig. 1.3-16). The enhancement already declines again in late images—in contrast to most focal inflammatory or tumor findings. There is no indication for treatment.
Fig. 1.3–16a, b Telangiectasia. (a) In a young woman with formication in the left arm, the hemosiderin-sensitive T2* gradient echo sequence on MRI shows flat signal fading in the left paramedian area in the pons, much weaker than in a cavernoma (see Fig. 1.3-12c). The T1-weighted and T2-weighted images were normal. (b) On the T1-weighted sequences after contrast administration, there is circumscribed enhancement of small vascular structures in this area, compatible with capillary telangiectasia as an incidental finding in the examination.
Fig. 1.3–17a, b Venous angioma or developmental venous anomaly (DVA). (a) Digital subtraction angiography identifies a venous malformation in the cerebellum solely in the venous phase, with small afferent veins (“caput medusae”) and an efferent collecting vein (arrow). (b) Magnetic resonance imaging (T1-weighted sequence) after contrast administration shows a similar finding, with the small afferent veins contrasted (arrow). The collecting vein was imaged on adjacent sections (not shown).
1.3.3.3 Venous malformations (venous angioma)
Venous malformations are very often seen on MRI images. These represent a circumscribed persistent embryonic venous system consisting of small, spider-burst veins that flow into a dilated collecting vein (“caput medusae”). The term “developmental venous anomaly” (DVA) has therefore also been introduced to describe this type of vascular malformation. They often occur in combination with cavernomas, a radiographic search for which should therefore be carried out. Venous malformations usually have no clinical significance. An association with seizures or intracranial bleeding is more likely to be explained by small, radiographically undiagnosed cavernomas.
Venous malformations can be demonstrated angiographically. However, the venous structures are only first filled with contrast in the venous phase, as compared to arteriovenous malformations with early arteriovenous shunts. The MRI appearance is also typical, with small, confluent spider-burst veins and larger, efferent collecting veins becoming visible after contrast administration (Fig. 1.3-17). Treatment is not necessary and might be dangerous, as DVAs drain normal brain tissue.
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