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J Emerg Med. 2012 May;42(5):559-65. doi: 10.1016/j.jemermed.2011.05.101. Epub 2012 Feb 2.

Comparative sensitivity of computed tomography vs. magnetic resonance imaging for detecting acute posterior fossa infarct.

Author information

1
Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.

Abstract

BACKGROUND:

Posterior fossa strokes, particularly those related to basilar occlusion, pose a high risk for progression and poor neurological outcomes. The clinical history and examination are often not adequately sensitive or specific for detection.

STUDY OBJECTIVES:

Because this population stands to benefit from acute interventions such as intravenous and intra-arterial tissue plasminogen activator, mechanical thrombectomy, and intensive monitoring for neurologic deterioration, this study examined the sensitivity of non-contrast head computed tomography (NCCT) for diagnosing posterior fossa strokes in the emergency department.

METHODS:

This study analyzed a prospectively collected database of acute ischemic stroke patients who underwent head NCCT within 30 h of symptom onset and who were subsequently found to have a posterior fossa infarct on brain magnetic resonance imaging (MRI) performed within 6 h of the NCCT.

RESULTS:

There were 67 patients identified who had restricted diffusion on MRI in the posterior fossa. The National Institutes of Health Stroke Scale (NIHSS) scores ranged from 0 to 36, median 3. Only 28 patients had evidence of infarction on the initial NCCT scan. The timing of NCCT scans ranged from 1.2 to 28.9 h after symptom onset. The sensitivity of NCCT was 41.8% (95% confidence interval 30.1-54.4). The longest period of time between symptom onset and a negative NCCT with a subsequent positive diffusion-weighted imaging MRI was 26.7 h.

CONCLUSIONS:

Head NCCT imaging is frequently insensitive for detecting posterior fossa infarction. Temporal evolution of strokes in this distribution, coupled with beam-hardening artifact, may contribute to this limitation. When a posterior fossa stroke is suspected and the NCCT is non-diagnostic, MRI is the preferred imaging modality to exclude posterior fossa infarction.

PMID:
22305149
PMCID:
PMC3346849
DOI:
10.1016/j.jemermed.2011.05.101
[Indexed for MEDLINE]
Free PMC Article

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