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      Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm





    Chief Complaint


    Organ System


    Patent Pending

    Modified Fisher Grading Scale for Subarachnoid Hemorrhage (SAH)

    States severity of SAH based on amount and type of blood on CT with associated vasospasm risk.


    This scale only applies to aneurysmal subarachnoid hemorrhage (aSAH).

    • Thin SAH is classified as < 1mm in depth.
    • Thick SAH is classified as ≥ 1mm in depth.

    Clinician must be able to identify subarachnoid hemorrhage (SAH) and major neuroanatomical landmarks on head CT.

    When to Use
    Why Use

    Patients with aSAH.

    • The Modified Fisher Grading Scale (MFS) helps predict the risk of clinical vasospasm and delayed cerebral ischemia (DCI) in aSAH. It improves upon the original Fisher scale by incorporating presence of intraventricular hemorrhage (IVH).
    • The MFS is entirely radiographic and typically determined at initial presentation.
    • Four basic MFS grades (1-4) map to risk of clinical vasospasm.
    • Rates of vasospasm for each MFS grade vary across studies. The MFS grade should not interpreted as an exact probability of developing vasospasm or DCI.
    • Should NOT be used as the sole data point to make decisions on medical management or goals of care.
    • Was not originally developed to predict mortality, but a recent review showed that MFS grade is associated with in-hospital mortality. (Lantigua 2015)
    • Similarly, the MFS was not originally designed to predict neurological outcome, but a retrospective analysis showed that MFS grades are associated with a higher chance of poor neurological outcome. (Kramer 2008)
    • Does NOT apply to SAH due to trauma, arteriovenous malformations, cavernous angiomas, dural arteriovenous fistulae, cortical or sinus venous thromboses, mycotic aneurysms, or septic emboli with hemorrhagic transformation.
    • Allows timely preventative treatment for vasospasm and DCI to be initiated (vasospasm typically occurs between 4 and 14 days (“vasospasm window”) after the onset of aSAH. (Fisher 1983)
    • Vasospasm is common in aSAH and often results in DCI, which occurs in up to 46% of all patients and can cause devastating neurological consequences and/or death. (Claassen 2001)
    • The MFS is widely used and well-known in the critical care and neurocritical care communities.
    No SAH present
    Focal or diffuse thin SAH
    Focal or diffuse thick SAH


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    Next Steps
    Creator Insights


    • Neurological and neurosurgical consultation should be obtained for patients with evidence of any SAH on imaging or lumbar puncture, whether the SAH is likely to be aneurysmal or non-aneurysmal in nature.
    • Computed tomographic angiography (CTA) of the head is helpful to determine the presence of a lesion suitable for surgical or endovascular intervention.
    • Consider discussing need for cerebrovascular imaging, such as CTA of the head or catheter angiography, with neurological or neurosurgical consultant before ordering.
    • Similarly, consider deferring the decision to start medications that have been shown to alter outcomes in aSAH (such as nimodipine and/or aminocaproic acid) to the neurological or neurosurgical consultant.
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    About the Creator
    Dr. Jan Claassen
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