Reversible Cerebral Vasoconstriction Syndrome and Thunderclap Headaches: Understanding a Transient Neurological Event

Reversible Cerebral Vasoconstriction Syndrome (RCVS) is a neurological disorder characterized by a sudden, severe onset of headaches and reversible narrowing of the cerebral arteries. While its exact prevalence is unknown, RCVS is increasingly recognized as a cause of thunderclap headaches (TCH), which are severe headaches that escalate very quickly:  from no pain to severe pain in less than a minute. Understanding RCVS and its hallmark presentation of thunderclap headaches is crucial for timely diagnosis and effective management.

What is Reversible Cerebral Vasoconstriction Syndrome?

RCVS is marked by transient spasms of the blood vessels in the brain. The mechanism of RCVS is not fully understood but is believed to involve changes in the thin layer of muscle that lines blood vessels.  This layer of muscle normally helps control the size of the blood vessels in different parts of your body to help with several functions such as body temperature and blood pressure.  For example, the blood vessels on the skin’s surface constrict when it is cold out (to keep your warmth inside) and dilate when it is hot out (to get rid of excess warmth).  The blood vessels in your body also constrict when you stand up, otherwise gravity would drain blood from your head and cause you to pass out.  In RCVS, the blood vessels in the brain constrict abnormally, causing pain and sometimes neurologic problems like seizures and strokes. Potential triggers include exercise, sexual activity, and a variety of medications and drugs (especially those that constrict blood vessels like cocaine and amphetamines).

Clinical Presentation

The defining symptom of RCVS is the thunderclap headache, named for its sudden and explosive onset. Patients often describe it as the worst headache of their lives, reaching peak intensity in less than a minute. In RCVS these severe headaches can recur over the course of about one month, with additional headaches for the next 2 months.  After 3 months, the headaches are usually gone completely and rarely return.


The diagnosis of RCVS includes a combination of headache (typically a thunderclap headache) and imaging of the blood vessels in the head showing multiple areas of vasoconstriction.  Key diagnostic steps include:

  • Clinical Assessment: A thorough history and physical examination, focusing on the characteristics of the headache and associated symptoms. RCVS is not the only cause of thunderclap headaches:  brain hemorrhages can also cause a thunderclap headache and should also be evaluated.
  • Imaging: Initial imaging often involves computed tomography (CT) or magnetic resonance imaging (MRI); these do not show RCVS, but are used to rule out other causes of thunderclap headache such as hemorrhages. Magnetic resonance angiography (MRA) or CT angiography (CTA) is crucial for visualizing the vasospasm typical of RCVS.
  • Cerebral Angiography: In uncertain cases, conventional cerebral angiography may be performed. Similar to a “heart cath,” cerebral angiography involves a catheter placed in a blood vessel, with dye injected to take a picture of the blood vessels. This is the definitive test for RCVS.
  • Follow-up Imaging: Repeating imaging after 2-3 months is essential to confirm the reversibility of the vasoconstriction, which is a hallmark of RCVS.


There is no standardized treatment for RCVS, but management generally focuses on medications that dilate blood vessels and limiting potential triggers:

  • Blood vessel dilation: Calcium channel blockers (e.g., amlodipine or nimodipine) are commonly used to reduce arterial spasm. These are typically taken for 3 months but then, if repeat imaging is normal, are sometimes stopped.
  • Trigger Avoidance: Identifying and eliminating potential triggers, including discontinuing offending medications or substances, is essential.
  • Supportive Care: Hospitalization may be necessary for severe cases, particularly those involving neurological deficits.
  • Follow-Up: Regular follow-up to monitor the resolution of symptoms and vascular changes is important. This typically involves repeat imaging and clinical evaluations.


The outlook for patients with RCVS is generally good, with most individuals having minimal headaches after 1 month, and no additional symptoms or blood vessel contriction after 3 months.  RCVS rarely occurs a second time.  A major goal in those 3 months is to prevent long-term problems like stroke with medications and with avoiding triggers.  Early recognition and appropriate management are key to preventing such outcomes.


Reversible Cerebral Vasoconstriction Syndrome, though often benign, is a significant cause of thunderclap headaches and can present with alarming neurological symptoms. Awareness and understanding of RCVS among healthcare providers are essential for prompt diagnosis and effective management, ensuring favorable outcomes for patients.

The Will Erwin Headache Research Foundation was founded with mission to find a cure for debilitating headaches, including but not limited to migraines and cluster headaches. As new headache disorders are discovered and further researched, The Foundation is also committed to keeping sufferers and their families alike, informed and aware of the ongoing changes and how they may impact them. To be part of the mission of The Foundation, consider contributing today.