Vascular lesions of the brain: causes, symptoms, diagnosis, treatment

Among the vascular malformations of the cerebral arteries, arteriovenous malformations and aneurysms are the most common.

Arteriovenous malformations (AVM)

Arteriovenous malformations are networks of dilated blood vessels in which arteries directly drain into veins. Arteriovenous malformations most commonly occur at the site of branching of cerebral arteries, usually within the brain parenchyma of the frontoparietal region, frontal lobe, lateral cerebellum, or occipital lobe vessels. Arteriovenous malformations may bleed or directly compress brain tissue, leading to seizures or ischemia. Arteriovenous malformations may be incidental findings on CT or MRI; CT with or without contrast typically reveals arteriovenous malformations larger than 1 cm in diameter. Arteriovenous malformations should be suspected if a patient complains of a sensation of noise in the head. Angiography is necessary to confirm the diagnosis and assess the operability of arteriovenous malformations.

Obliteration of superficial arteriovenous malformations is possible with the use of combined interventions using microsurgery, radiosurgery and endovascular correction. For correction of deep and large arteriovenous malformations, but not more than 3 cm in diameter, stereotactic radiosurgery, endovascular treatment methods (for example, pre-resection embolization or thrombolysis through an intra-arterial catheter) or coagulation with a focused proton beam are used.

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Aneurysms

Aneurysms are focal dilations of arteries. The prevalence of aneurysms in the population is approximately 5%. The most common causes of aneurysms are arteriosclerosis, arterial hypertension, and hereditary connective tissue diseases (in particular, Ehlers-Danlos syndrome, pseudoxanthoma elasticum, autosomal dominant polycystic kidney disease). Sometimes septic emboli induce the development of mycotic aneurysms. Cerebral aneurysms are usually no more than 2.5 cm in diameter, saccular (not fusiform) in shape, sometimes with small multiple protrusions with a thinned wall (bunch-shaped aneurysm). Most aneurysms are aneurysms of the middle or anterior cerebral arteries or communicating branches of the circle of Willis, especially at the sites of arterial bifurcation. Mycotic aneurysms usually develop distal to the first divergence of the arterial branches of the circle of Willis. Many aneurysms are asymptomatic, but some cause symptoms due to compression of adjacent structures. Oculomotor palsies, diplopia, strabismus, and orbital pain may indicate compression of cranial nerves III, IV, V, or VI. Visual loss and bitemporal visual field defects may indicate compression of the optic chiasm. Bleeding from aneurysms into the subarachnoid space causes symptoms of subarachnoid hemorrhage. Aneurysms do not necessarily cause headache before rupture, although microhemorrhages preceding rupture may well be the source of headache. Aneurysms are often incidental findings on CT or MRI. Angiography or magnetic resonance angiography is needed to verify the diagnosis. If the size of an asymptomatic aneurysm in the blood supply zone of the anterior cerebral artery does not exceed 7 mm, the risk of rupture is considered low and does not justify the risks associated with surgical correction. If a patient has a large aneurysm in the blood supply zone of the posterior cerebral artery, there are symptoms of bleeding or compression of adjacent brain structures, then immediate endovascular surgery is indicated.

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