Both CT and MRI imaging scans can be read as negative in a patient with an acute stroke.

Risk factors for negative imaging studies:

(1) small infarct

(2) poor image quality

(3) interpretation error

(4) failure to perform follow-up scan after an initial negative scan

(5) failure to provide sufficient clinical information to the radiologist

(6) brainstem stroke

(7) low NIHSS score


A CT scan may be negative with:

(1) small or late-presenting subarachnoid hemorrhage

(2) ischemic stroke (versus diffusion-weighted MRI)

(3) cerebral venous sinus thrombosis

(4) lesions in the posterior fossa

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