Wednesday, July 30, 2014

Vascular Lesions

Vascular lesions
CT revolutionised the non-invasive diagnosis of 'strokes' and is the most worthwhile form of early primary investigation in any patient who has suffered or is suspected of suffering from a cerebrovascular accident. Intracranial haemorrhage or haematoma is shown as a high density lesion (Fig. 12.19) due to the clot. As the clot absorbs, the lesion becomes isodense and later of low attenuation.

 This residual low density represents the area of damaged brain. Extracerebral haematoma, both extradural and subdural, are well demonstrated, par-ticularly in the acute phase, as high density peripheral lesions. Subdural haematoma may go through an isodense phase as the blood clot is absorbed and later becomes hypodense. Chronic subdural haematomas show a very characteristic appearance of a low density peripheral lesion in the skull (Fig. 12.20). CT also provides an ideal non-invasive method of investigating patients with head injuries and comatose patients suspected of head injury. Apart from showing extradural and subdural haematomas, intracranial contusions with haemorrhage are also well shown as are the relationships of depressed fractures to underlying brain. Subarachnoid haemorrhage is best investigated by CT in the first place. In a high proportion of cases the localisation of blood in the subarachnoid space or of secondary intracranial haematoma will establish where the ruptured aneurysm or angioma is sited. Large angiomas and aneurysms are also well shown by CT before they rupture, particularly after enhancement.

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