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PubMed This is a summary of 8 peer-reviewed journal articles Updated
Neurology · Primary Angiitis of the Central Nervous System

Recognizing Symptoms and Emergency Red Flags

At a Glance

Central nervous system vasculitis can cause ongoing headaches, fatigue, memory or mood changes, and seizures. Sudden weakness, speech or vision changes, severe confusion, a new or prolonged seizure, thunderclap headache, or high fever needs emergency care.

Symptoms of Primary Angiitis of the Central Nervous System (PACNS) can vary significantly from person to person. Because this disease can affect different sizes of blood vessels and different areas of the brain, no two patients have the exact same experience [1][2].

Understanding your symptoms involves distinguishing between the daily challenges of living with a chronic condition and the “red flag” signs that require immediate emergency care.

How Vessel Size Affects Your Symptoms

Doctors often categorize PACNS based on which blood vessels are inflamed. This “phenotype” or category can influence the symptoms you are most likely to experience [2][3].

  • Small-Vessel PACNS: This type affects the tiny arteries deep in the brain tissue or in the leptomeninges (the protective layers covering the brain). It commonly presents as encephalopathy—a general term for brain dysfunction that includes confusion, memory loss, personality changes, or a “foggy” feeling [1][4]. You may also experience persistent, dull headaches or seizures [1][5].
  • Medium and Large-Vessel PACNS: This type affects the larger arteries that supply blood to major sections of the brain. It is more likely to cause sudden “focal” symptoms, which are issues restricted to a specific part of the body, such as weakness on one side or difficulty speaking [1][2]. These symptoms often look like a stroke and can happen repeatedly in different areas of the brain [2][5].

Non-Emergency Symptoms

Many symptoms of PACNS are subacute, meaning they develop slowly over days or weeks rather than all at once [1]. While these require medical attention, they are generally part of your baseline if they are stable and already discussed with your team:

  • Chronic Headaches: Dull, aching, or “heavy” headaches that have been present for a long time and have not changed in character [1].
  • Mild Cognitive Changes: Slight difficulty multi-tasking, subtle memory lapses, or taking longer to process information that remains stable over time [4].
  • Mood Changes: Persistent feelings of anxiety, depression, or emotional irritability [1].
  • Fatigue: A deep, persistent exhaustion that does not improve with rest.

When to Seek Emergency Care: Red Flags

A “red flag” is a symptom that could indicate a new stroke, a brain bleed (hemorrhage), a dangerous level of brain swelling, a serious infection, or medication toxicity [1][6]. If you experience any of the following, call emergency services (such as 911) or go to the nearest emergency room immediately. Do not drive yourself, and record the exact time the symptoms began:

  • Sudden Weakness or Numbness: Especially if it occurs on only one side of the face or body.
  • Trouble Speaking: Sudden slurring of words, difficulty finding words, or inability to understand others.
  • Vision Loss: Abrupt blurring, double vision, or loss of sight in one or both eyes.
  • Severe Loss of Balance: Sudden dizziness, incoordination, or inability to walk.
  • First or Prolonged Seizure: Any new seizure activity, or a seizure that lasts more than five minutes.
  • New Severe Confusion: A sudden drop in alertness, disorientation to time or place, or being unable to wake up.
  • Thunderclap or Unusual Severe Headache: A sudden, excruciating headache that reaches its maximum intensity within seconds—often described as the “worst headache of my life”—or a severe headache accompanied by neck stiffness or fever [6][7].
  • High Fever or Infection Signs: Because your treatments suppress your immune system, a high fever or severe systemic illness requires emergency evaluation.

Triage: When to Contact Your Team

In someone with known CNS vasculitis, any sudden, new, or clearly worsening neurological symptom requires urgent advice or emergency assessment according to your care plan. If a symptom is clearly changing, getting worse, or you develop a fever, contact your neurology team’s office immediately; an adjustment to your current treatment plan may be needed [8]. If you have emergency symptoms, do not wait for an office callback—seek emergency services right away.

Common questions in this guide

What symptoms can central nervous system vasculitis cause?
Symptoms can include ongoing headaches, fatigue, changes in memory or thinking, mood or personality changes, and seizures. Some people develop stroke-like problems such as weakness on one side, trouble speaking, vision changes, or difficulty walking.
Which CNS vasculitis symptoms require emergency care?
Call emergency services for sudden weakness or numbness, trouble speaking, sudden vision loss, severe loss of balance, a first or prolonged seizure, new severe confusion, or a thunderclap headache. High fever or signs of a serious infection also require urgent evaluation, especially during immune-suppressing treatment.
How can I tell whether a symptom is part of my baseline or an emergency?
Stable headaches, mild thinking changes, mood symptoms, or fatigue may be part of your established baseline if your care team has already reviewed them. A symptom that is sudden, clearly different, or getting worse may signal a stroke, bleeding, swelling, infection, or medication toxicity and needs urgent medical assessment.
Does the type of blood-vessel involvement affect CNS vasculitis symptoms?
Yes. Small-vessel disease more often causes brain dysfunction, headaches, or seizures. Medium- and large-vessel disease is more likely to cause sudden, localized problems such as one-sided weakness or difficulty speaking that can resemble a stroke.
When should I contact my neurology team about a new symptom?
Contact your neurology team promptly if a symptom changes, worsens, or occurs with fever. Do not wait for an office callback if you have a possible emergency symptom; call emergency services and note the exact time it began.
How should I prepare for a CNS vasculitis emergency?
Ask your care team which hospital to use, who to call, and what information to bring. Keep your medication list and medical records available, and make sure a trusted person knows your plan so you do not have to drive yourself during an emergency.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my imaging and tests, do I have small-vessel or medium-to-large-vessel involvement?
  2. 2.What specific non-emergency symptoms should I monitor as a sign that my current treatment might need adjustment?
  3. 3.How can we distinguish between a side effect of my medication and a new symptom of PACNS?
  4. 4.Is there a specific hospital or ER where I should go if I experience red-flag symptoms, to ensure I see doctors familiar with my condition?

Questions For You

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References

References (8)
  1. 1

    Primary central nervous system vasculitis - An update on diagnosis, differential diagnosis and treatment.

    Kraemer M, Berlit P

    Journal of the neurological sciences 2021; (424()):117422 doi:10.1016/j.jns.2021.117422.

    PMID: 33832773
  2. 2

    Subtypes of primary angiitis of the CNS identified by MRI patterns reflect the size of affected vessels.

    Schuster S, Bachmann H, Thom V, et al.

    Journal of neurology, neurosurgery, and psychiatry 2017; (88(9)):749-755 doi:10.1136/jnnp-2017-315691.

    PMID: 28705900
  3. 3

    A comparative study of large-vessel and small-vessel primary angiitis of the central nervous system: insights from a Chinese single-center retrospective cohort.

    Wang Y, Lyu J, Li F, et al.

    Frontiers in immunology 2025; (16()):1724588 doi:10.3389/fimmu.2025.1724588.

    PMID: 41479923
  4. 4

    Central Nervous System Vasculitis: Primary Angiitis of the Central Nervous System and Central Nervous System Manifestations of Systemic Vasculitis.

    Amin M, Uchino K, Hajj-Ali RA

    Rheumatic diseases clinics of North America 2023; (49(3)):603-616 doi:10.1016/j.rdc.2023.03.011.

    PMID: 37331735
  5. 5

    Primary Angiitis of the Central Nervous System: Magnetic Resonance Imaging Spectrum of Parenchymal, Meningeal, and Vascular Lesions at Baseline.

    Boulouis G, de Boysson H, Zuber M, et al.

    Stroke 2017; (48(5)):1248-1255 doi:10.1161/STROKEAHA.116.016194.

    PMID: 28330942
  6. 6

    Reversible cerebral vasoconstriction syndromes and primary angiitis of the central nervous system: clinical, imaging, and angiographic comparison.

    Singhal AB, Topcuoglu MA, Fok JW, et al.

    Annals of neurology 2016; (79(6)):882-94 doi:10.1002/ana.24652.

    PMID: 27043703
  7. 7

    Cerebrospinal fluid findings in reversible cerebral vasoconstriction syndrome: a way to differentiate from cerebral vasculitis?

    Kraayvanger L, Berlit P, Albrecht P, et al.

    Clinical and experimental immunology 2018; (193(3)):341-345 doi:10.1111/cei.13148.

    PMID: 29722896
  8. 8

    European Stroke Organisation (ESO) guidelines on Primary Angiitis of the Central Nervous System (PACNS).

    Pascarella R, Antonenko K, Boulouis G, et al.

    European stroke journal 2023; (8(4)):842-879 doi:10.1177/23969873231190431.

    PMID: 37903069

This page about CNS vasculitis symptoms and emergency red flags is for informational purposes only and does not constitute medical advice. Follow your personal emergency plan and seek urgent care for new or worsening neurologic symptoms.

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