What Are The Specific Clinical Features That Distinguish A Case Of Posterior Reversible Encephalopathy Syndrome (PRES) From A Case Of Reversible Cerebral Vasoconstriction Syndrome (RCVS) In A Patient Presenting To The Emergency Department With Thunderclap Headache And Seizures, Particularly In The Context Of A Recent History Of Preeclampsia Or Eclampsia?

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In distinguishing between posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS) in a patient presenting with thunderclap headache and seizures, particularly with a history of preeclampsia or eclampsia, the following key features are considered:

  1. Imaging Findings:

    • PRES: Characterized by posterior cerebral edema, typically in the parietal and occipital regions, seen on MRI. The edema is usually symmetric.
    • RCVS: Shows reversible vasoconstriction of cerebral arteries on imaging such as MRA or CT angiography, which may lead to infarcts.

  2. Blood Pressure:

    • PRES: Often associated with severe hypertension, a hallmark of preeclampsia or eclampsia.
    • RCVS: May not present with significant hypertension unless related to another condition.

  3. Headache Characteristics:

    • PRES: While headaches can occur, they are not typically the primary symptom. Vision changes and confusion are more common.
    • RCVS: Typically presents with a thunderclap headache, which is sudden and severe.

  4. Associated History:

    • PRES: Strongly associated with preeclampsia or eclampsia, which are hypertensive emergencies.
    • RCVS: May be linked to substance use (e.g., cannabis, cocaine) or certain medications.

  5. Clinical Presentation:

    • PRES: Often includes seizures, vision loss, and confusion due to posterior brain involvement.
    • RCVS: May present with transient ischemic attacks, strokes, or recurrent thunderclap headaches over days.

  6. Triggers and Recurrence:

    • RCVS: Can have recurrent headaches and is sometimes preceded by vasoactive substance use.
    • PRES: Typically presents acutely in the context of severe hypertension.

In summary, while both conditions can present with seizures and headache, the presence of posterior edema on MRI, severe hypertension, and a history of preeclampsia favor PRES. Conversely, thunderclap headache, vasoconstriction on imaging, and substance use history point towards RCVS.