Dear all
I have been asked to look into the following, and I must confess I don't have a great depth of knowledge in this area (any guidance much appreciated!)
Has anyone looked at (or got any thoughts on) the evidence for brain imaging following transient ischaemic attack?
The arguments for are: to confirm ischaemia in order to put people on aspirin; to identify rare other causes of the symptoms (e.g. tumour or subdural haematoma).
The argument against that has been put to me is: wouldn't it be cheaper just to put everyone on aspirin based on history and examination (assuming the harm from this is low), and not to bother with imaging.
Has anyone looked at the harms/benefits of such an approach?
For information, the American Heart Association guidelines http://www.bmj.com/cgi/content/full/321/7258/393 say:
There is general agreement that patients with manifestations suggestive of hemispheric TIA should receive a CT scan of the head in the initial diagnostic evaluation to exclude a rare lesion such as a subdural hematoma or brain tumor responsible for symptoms (Class III, type C). CT may reveal an area of brain infarction appropriate to TIA symptoms in 29% to 34% of patients, a finding that may influence subsequent management, especially the timing of an eventual carotid endarterectomy (Class III, type C). CT of the head has only a limited role in evaluation of patients with TMB (Class III).
Despite a slight advantage of MRI over CT in detection of brain infarction appropriate to hemispheric symptoms of ischemia, substitution of MRI for CT in initial evaluation of patients with TIA is not warranted. The panel recognizes that this is a subject of considerable dissension. MRI may be considered when a CT scan fails to substantiate the clinical diagnosis or if additional diagnoses require confirmation or exclusion (Class III). There is also advantage in identifying lesions such as subdural hematoma that may be isodense with surrounding parenchyma on CT imaging as well as in AVMs that rarely present with hemispheric TIAs (Class III, type C).
CT of the head has a limited role in evaluation of patients with vertebrobasilar TIAs, as subdural hematoma or brain tumor are not known to present with transient symptoms resembling posterior circulation ischemia (Class III). CT can detect areas of appropriate cerebellar or, less commonly, brain stem infarction, a finding that in selected instances may alter clinical management. In addition, CT may show evidence of severe atherosclerotic disease in the vertebrobasilar system, such as dolichoectasia of the basilar artery, as a potential mechanism of TIAs (Class III).
The routine use of MRI in evaluation of patients with vertebrobasilar TIAs is not justified (Class III) vis-a-vis general management, despite its advantages over CT in detection of lesions potentially related to the mechanism of posterior circulation TIAs, such as atherosclerotic tortuosity, stenosis, or occlusion of the basilar artery (Class III). Occult brain infarction is better identified by MRI in the vertebrobasilar territory, a finding that may provide additional information about the source of the TIA.
Kind regards
Dr John Powell
Specialist Registrar in Public Health Medicine
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+44 (0) 1296 310143
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