ABNORMALITIES OF EXTRACRANIAL VESSELS
This disease involves intracranial as well as extracranial vessels which appear like a 'string of beads'. The patient presents with infarction as a result of thrombotic occlusion or haemorrhage from an associated saccular aneurysm, of which there is an increased risk. Transluminal angioplasty can be used to dilate a stenotic segment.
Dilated and narrowed segments of vessel. Produced by fibrosis of the lamina media.
Extracranial and intracranial dissections are an underdiagnosed cause of stroke in young persons. Spontaneous dissections occur in Marian's syndrome, fibromuscular dysplasia, migraine and hypertension. Pathological examination often reveals cystic degeneration or necrosis of the media.
TRAUMA TO CAROTID AND VERTEBRAL VESSELS
A direct blow to the neck, a sustained tight grip around the neck or a hyperextension injury may produce an intimal tear of the extracranial vessels. This may lead to dissection and occlusion.
The vertebral arteries arc particularly susceptible to trauma in view of their close relationship to the cervical spine at intervertebral foramina, the atlanto-axial joint and the occipito-atlantal joint. Carotid dissection may present with a painful isolated Horner's syndrome.
Angiography will confirm, and exploration and/or anticoagulant therapy may halt thrombus formation.
Pressure from a cervical rib can result in aneurysmal formation in the subclavian artery with endothelial damage, thrombus formation and embolisation down the arm or retrograde thrombus spread and embolisation to the vertebral and common carotid arteries.
Infection in structures close to the carotid artery can result in inflammatory change in the vessel wall and secondary thrombosis. In children, infection in the retropharyngeal fossa (tonsillar infection) may cause cerebral infarction. Meningitis (especially pneumococcal) may result in secondary arteritis and occlusion of intracerebral vessels as they cross the subarachnoid space.
Bilateral occlusion of the carotid artery at the siphon is followed by the development of a fine network of collateral arteries and arterioles at the base of the brain. This may be a congenital or acquired disorder associated with previous meningitis, oral contraception or granulomatous disease (e.g. sarcoidosis). Children present with alternating hemiplegia, adults with subarachnoid haemorrhage. There is no specific treatment though some use surgical revascularisation procedures.
A recessively inherited disorder. Accumulation of homocystine in blood damages endothelium and induces premature occlusive arterial disease. The significance of the heterozygote state is uncertain.
See Mitochondrial disorders (page 462)
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