Cerebral vasculitis and reversible cerebral vasoconstriction

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Cerebral vasculitis describes inflammation that damages intracranial vessel walls and can cause stenosis, occlusion, infarction or haemorrhage. It may be primary to the central nervous system or secondary to systemic autoimmune disease, infection, malignancy, drugs or another inflammatory process. Primary CNS vasculitis is rare, its symptoms and tests are non-specific, and no single blood marker confirms it. Diagnostic confidence comes from the tempo, MRI distribution, CSF, vascular and vessel-wall imaging, exclusion of mimics and, in selected cases, a targeted brain or meningeal biopsy.

RCVS is a non-inflammatory dysregulation of cerebral arterial tone. Its hallmark is severe headache reaching maximum intensity rapidly, commonly recurring with exertion, sexual activity, bathing, coughing or emotional stress. Focal deficits and seizures can occur, and complications evolve across the first weeks. Vasoconstriction on CTA, MRA or catheter angiography is segmental and multifocal, but the name is confirmed retrospectively through reversibility and the clinical course rather than a single beaded image.

The early problem is not merely distinguishing two rare labels; it is safely excluding more frequent time-critical disease while avoiding premature steroids. Suspected CNS vasculitis or RCVS requires neurologist and neuroradiologist involvement, infectious exclusion and adherence to local stroke, headache, pregnancy and immunosuppression governance.

Key points

Reversible cerebral vasoconstriction syndrome typically causes recurrent thunderclap headaches over days to weeks, with or without convexity subarachnoid blood, ischaemic stroke, intracerebral haemorrhage, posterior reversible encephalopathy or seizures.
RCVS associations include the postpartum period and exposure to vasoactive substances, including sympathomimetics, serotonergic agents, stimulants and some recreational drugs; ask without judgement and document timing.
Primary angiitis of the central nervous system more often develops subacutely with progressive headache, cognitive or behavioural change, seizures and multifocal neurological deficits rather than repeated stereotyped thunderclaps.
Multifocal arterial narrowing or beading is not diagnostic of vasculitis: RCVS, atherosclerosis, dissection, infection and technical artefact can produce overlapping angiographic appearances.
Cerebrospinal fluid is often normal or only mildly abnormal in RCVS, whereas inflammatory change supports—but does not prove—CNS vasculitis after infection and malignancy are considered.
Early angiography can be normal in RCVS because narrowing may begin distally; evolving symptoms warrant specialist review and sometimes repeat vascular imaging.
Glucocorticoids are not routine RCVS treatment and observational evidence suggests possible harm; immunosuppression should be reserved for a defensible inflammatory diagnosis under specialist leadership.
Demonstrating substantial resolution of arterial narrowing by about three months supports RCVS, but follow-up timing and modality should be individualised by neurology and neuroradiology.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Primary CNS inflammatory vasculitis

Immune inflammation may be confined to cerebral vessels without systemic disease, producing a subacute mixture of headache, cognitive change, seizures and multifocal deficits.

Secondary vascular inflammation

Systemic autoimmunity, infection, malignancy and selected drugs can inflame cerebral arteries; identifying the underlying process changes both antimicrobial and immunosuppressive safety.

Vasoactive-triggered RCVS

Postpartum physiology, sympathomimetics, serotonergic agents, stimulants and recreational drugs are associated with reversible dysregulation of arterial tone, although no trigger is found in some cases.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Vessel-wall inflammation
In vasculitis, immune cells injure arterial walls, causing oedema, narrowing, thrombosis, weakening and irregular perfusion across multiple cerebral territories.
2
Dynamic arterial constriction
In RCVS, abnormal control of vascular tone produces segmental constriction and dilatation that evolves across distal and proximal cerebral arteries.
3
Downstream brain injury
Reduced flow causes transient ischaemia or infarction, while fragile or reperfused vessels may bleed and autoregulatory failure can generate vasogenic oedema.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Recurrent thunderclap phenotypeRed flag

Several abrupt maximal-at-onset headaches separated by partial improvement, especially after exertional or vasoactive triggers, strongly suggests RCVS but retains an emergency vascular differential.

Subacute inflammatory phenotypeRed flag

Progressive headache with cognitive change, multifocal deficits, seizures or encephalopathy over weeks is more compatible with CNS vasculitis than uncomplicated RCVS and warrants expedited specialist investigation.

RCVS complicationsRed flag

Convexity subarachnoid haemorrhage and oedema syndromes often occur early, while ischaemic complications can emerge later; any new deficit or reduced consciousness demands repeat emergency assessment.

Secondary vasculitis clues

Fever, rash, arthritis, ocular inflammation, renal findings, immunosuppression, recent infection, malignancy or systemic vascular symptoms should direct testing beyond isolated primary CNS disease.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Emergency non-contrast CT brain and acute headache pathwayFirst step
Why
Identify subarachnoid or intracerebral blood and assess other urgent structural causes of thunderclap headache.
Interpretation and limitations
Sensitivity depends on timing and scan quality. If subarachnoid haemorrhage remains possible after a negative CT, follow the current national and local pathway for further testing rather than assuming RCVS.
02
CTA or MRA of head and neck
Why
Assess intracranial narrowing, aneurysm, dissection, occlusion and other arterial explanations for headache or deficit.
Interpretation and limitations
Alternating narrowing and dilatation can support RCVS or vasculitis but is non-specific. Distal disease may be missed early, and expert comparison with later imaging is often more informative than one report.
03
MRI brain with diffusion, FLAIR and susceptibility imaging
Why
Map acute and previous infarction, convexity subarachnoid blood, oedema and the distribution of multifocal injury.
Interpretation and limitations
Infarcts of differing ages and territories support a vascular inflammatory process but also occur with embolism. Posterior vasogenic oedema can overlap with RCVS, particularly in pregnancy-related or hypertensive presentations.
04
Lumbar puncture after imaging and safety assessment
Why
Evaluate suspected infection or subarachnoid haemorrhage and look for inflammatory CSF supporting CNS vasculitis.
Interpretation and limitations
Cell count, protein, glucose, microbiology and selected virology are interpreted in context. Normal CSF weighs against many inflammatory vasculitides but does not independently establish RCVS.
05
Targeted systemic and infectious screen
Why
Search for a secondary cause while avoiding an indiscriminate low-specificity autoimmune panel.
Interpretation and limitations
FBC, inflammatory markers, renal and liver tests, urinalysis and tests guided by exposure and phenotype may identify infection or systemic disease. A positive autoantibody alone does not prove cerebral vessel inflammation.
06
Vessel-wall MRI, catheter angiography or biopsy
Why
Resolve persistent diagnostic uncertainty when the result would alter high-risk treatment.
Interpretation and limitations
Concentric enhancement may support inflammation but is not perfectly specific; catheter angiography defines lumen rather than histology. Targeted biopsy can confirm vasculitis or an alternative, yet sampling error means a negative result is not absolute exclusion.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Aneurysmal subarachnoid haemorrhage

A first thunderclap headache requires urgent haemorrhage investigation; RCVS may itself cause convexity subarachnoid blood but does not remove the need to exclude aneurysm.

Cervical artery dissection

Unilateral neck or facial pain, Horner syndrome and a mural abnormality favour dissection, which can also cause multifocal ischaemia and headache.

Intracranial atherosclerosis

Fixed stenosis at typical sites with vascular risk and calcified plaque favours atherosclerosis; beading alone cannot establish inflammatory vasculitis.

RCVS versus inflammatory vasculitis

Repeated thunderclaps, near-normal cerebrospinal fluid and later arterial resolution favour RCVS; progressive symptoms and inflammatory fluid support vasculitis but remain non-specific.

Additional chapter-specific clues

Dangerous mimic patternRed flag

Meningism, collapse, neck pain, papilloedema, pregnancy or puerperium, severe hypertension, thrombosis risk and focal deficit can point towards haemorrhage, dissection, venous thrombosis or hypertensive encephalopathy.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ThunderclapExclude immediate vascular catastropheFirst stepHeadache reaches peak intensity within seconds to a minute, whether first or recurrent.

11. Stabilise ABCDE, record exact onset and triggers, examine consciousness, meningism, optic discs and focal neurology, and check pregnancy or postpartum status.
22. Use the local subarachnoid-haemorrhage imaging pathway and add head-and-neck vascular imaging when RCVS, dissection, aneurysm or stroke is plausible.
3Escalation3. Escalate any haemorrhage, infarct, seizure or hypertensive emergency immediately; investigate a negative initial scan further when clinical suspicion remains.
44. Review prescribed, over-the-counter and recreational vasoactive exposures, but do not let a plausible trigger prematurely close the differential.

02DifferentiateBuild a syndrome-level diagnosisInitial emergencies are controlled but RCVS or cerebral vasculitis remains possible.

11. Compare tempo: recurrent thunderclaps with trigger exposure favour RCVS, whereas progressive encephalopathy and multifocal disease raise inflammatory or infectious causes.
22. Integrate MRI lesion pattern, arterial imaging, CSF and focused systemic findings, explicitly documenting evidence that argues both for and against each diagnosis.
33. Discuss equivocal studies in a neurovascular multidisciplinary setting and decide whether repeat angiography, vessel-wall imaging or biopsy would change management.
44. Exclude infections and relevant mimics before immunosuppression, with microbiology, rheumatology or other specialist input when the phenotype directs it.

03TreatMatch intervention to mechanismA specialist working diagnosis has been formed and complications have been identified.

11. For RCVS, stop non-essential vasoactive triggers, provide analgesia that avoids further vasoconstrictive exposure, and manage blood pressure without abrupt cerebral hypoperfusion.
22. Consider a calcium-channel blocker only with neurovascular advice, explaining that headache relief is more established than prevention of stroke and that hypotension may be harmful.
33. For probable vasculitis, define induction and prophylaxis through specialist services after infectious exclusion and obtain baseline safety tests before immunosuppressive treatment.
44. Arrange clinical and vascular-imaging follow-up to document recovery, detect complications and revisit the diagnosis if narrowing persists or symptoms evolve.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

May reduce the intensity or recurrence of thunderclap headache; evidence that it prevents infarction or haemorrhage is limited.

Nimodipine for selected RCVS

Specialist centres may use an oral regimen such as 30–60 mg every 4 hours, or an equivalent divided schedule, but this is off-label and must follow local neurovascular advice.

Monitor for hypotension, dizziness and drug interactions. Avoid creating low cerebral perfusion, and do not allow symptomatic improvement to replace follow-up imaging or emergency reassessment.

Suppresses damaging vessel-wall inflammation when primary or secondary CNS vasculitis is sufficiently supported.

High-dose glucocorticoid for confirmed inflammatory vasculitis

Induction may include intravenous methylprednisolone pulses followed by oral prednisolone, with exact dose, taper and additional immunosuppression determined by the specialist vasculitis team.

Do not use empirically for routine RCVS. Exclude important infection, document diagnostic confidence, and provide glucose, bone, gastric and opportunistic-infection risk management according to regimen.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Ischaemic stroke

Critical narrowing, thrombosis or embolism can infarct multiple arterial territories, leaving focal disability or cognitive impairment.

Intracranial haemorrhage

Vessel fragility and pressure changes may cause convexity subarachnoid or intracerebral bleeding, particularly early in RCVS or with destructive inflammation.

Seizures and posterior reversible encephalopathy

Cortical irritation and autoregulatory failure can produce seizures, visual symptoms, encephalopathy and vasogenic oedema requiring monitored supportive care.

Treatment-related worsening

Premature immunosuppression can obscure infection, while glucocorticoids may worsen RCVS; a defensible distinction is therefore clinically consequential.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Perform repeated neurological and headache assessments during the complication window, with immediate re-imaging for a new deficit, seizure, reduced consciousness or a materially changed headache.
Measure blood pressure frequently when vasoactive treatment is used, balancing severe hypertension against the risk of worsening ischaemia through excessive reduction.
Arrange interval CTA or MRA through the neurovascular team to show improvement or reversibility and to challenge an RCVS diagnosis if abnormalities persist.
When immunosuppression is prescribed, monitor full blood count, renal and liver function, infection risk, glucose and regimen-specific toxicity under a named specialist protocol.
Review all possible triggers, pregnancy-related context and recurrence-prevention advice at follow-up, including clear instructions for urgent return if thunderclap pain recurs.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Beading is a description

Segmental calibre change describes the lumen but cannot distinguish arterial-tone disturbance from inflammation, atherosclerosis, dissection or artefact without the clinical and temporal context.

Timing changes sensitivity

RCVS narrowing can be subtle or absent near the start of symptoms because abnormalities may progress from distal to more proximal vessels, making planned reassessment valuable.

CSF shifts probability

A convincingly inflammatory cerebrospinal-fluid profile supports vasculitis or infection, whereas near-normal findings fit RCVS; neither pattern should be interpreted without imaging and microbiology.

Steroids separate the pathways

Glucocorticoids may be central to inflammatory vasculitis but are inappropriate as reflex treatment for suspected RCVS, which is one reason diagnostic discipline matters.

Pregnancy broadens urgency

Postpartum thunderclap headache brings RCVS into focus but also demands active consideration of venous thrombosis, arterial dissection, haemorrhage, pre-eclampsia and posterior reversible encephalopathy.

11Common pitfallsFrequent interpretation and management errors.

01
Diagnosing RCVS from exposure to a serotonergic or sympathomimetic drug alone neglects subarachnoid haemorrhage, dissection and other lethal headache causes.
02
Calling angiographic beading vasculitis and immediately starting steroids can worsen RCVS and obscure infection before adequate diagnostic sampling.
03
Using a normal early CTA to permanently exclude vasoconstriction fails to account for evolving distal disease and the value of specialist repeat imaging.
04
Ordering a broad autoimmune screen without a phenotype creates incidental positives that can distract from infection, embolism, atherosclerosis or drug exposure.
05
Treating headache relief as proof of recovery overlooks delayed infarction and the need to confirm arterial resolution through planned follow-up.