Clinical presentation and pathomorphology
The disease is characterized by idiopathic inflammatory involvement of the central nervous system vasculature. Small arteries and arterioles are primarily involved. The inflammation is multifocal in nature, which clinically presents as recurrent episodes of small cerebral infarctions and transient ischemic attacks (TIAs) affecting multiple arterial territories simultaneously.
The key and sole method for definitive diagnostic verification remains brain biopsy.
Typical histological findings:
- Segmental inflammation of small vessels.
- Marked intimal proliferation and fibrosis.
- Spared tunica media (tunica media).
- In some cases, multinucleated Langerhans giant cells are found in the biopsy specimen.
The prognosis without treatment is extremely unfavorable. Timely therapy, including cyclophosphamide (cyclophosphamide) combined with prednisone (prednisone), can halt disease progression.
Diagnostic Imaging and Neuroimaging
Diagnostic imaging modalities detect pathology in more than 90% of patients, yet their findings have low specificity.
- Brain MRI: The primary lesion sites are the subcortical white matter (these lesions are sometimes mistaken for multiple sclerosis), deep grey matter, and cortex. Diffusion-weighted imaging (DWI) effectively demonstrates small acute infarctions (e.g., within the middle cerebral artery territory). Intracranial hemorrhage is atypical for PACNS. Parenchymal and leptomeningeal contrast enhancement is observed in 35% of patients. Cortical laminar necrosis may occur.
- Specialized MRI sequences: Targeted vessel wall imaging (vessel wall imaging) or the black-blood imaging (black-blood imaging) technique allows detection of contrast enhancement directly within the wall of the affected artery against a dark vessel lumen.
- Angiography (MRA, DSA, X-ray): Conventional angiography has low sensitivity. Typical findings include areas of segmental narrowing (stenosis) and widening (dilation) of medium-sized vessels, as well as vascular occlusions. Marked stenoses of the supraclinoid segment of the internal carotid artery and the proximal segment of the middle cerebral artery are frequently detected.
Cerebrospinal fluid (CSF) analysis
CSF examination reveals abnormalities in 80–90% of patients with primary CNS angiitis. However, these alterations are mild and non-specific. Most commonly, CSF analysis shows elevated total protein and/or pleocytosis (increased white blood cell count).
Differential diagnosis
The primary clinical and radiological "mimic" of primary angiitis is reversible cerebral vasoconstriction syndrome (RCVS). Unlike PACNS, it is accompanied by acute thunderclap headache (thunderclap headache), while CSF analysis and MRI remain normal (unless complicated by hemorrhage or PRES syndrome). The main criterion for RCVS is that the angiographic pattern of multifocal vasoconstriction is significantly or completely reversible within 3 months. The syndrome frequently occurs following the use of vasoactive substances, illicit drugs, or in the postpartum period.
It is also necessary to rule out:
- Secondary vasculitides: frequently occur in the setting of varicella-zoster virus infection (Varicella-zoster virus), HIV, or cocaine use.
- Primary systemic vasculitides: giant cell arteritis (in patients over 50 years of age, associated with polymyalgia rheumatica), Takayasu arteritis, polyarteritis nodosa, and granulomatosis with polyangiitis.
Briefly: answers to topical questions
What neurological symptoms, besides transient ischemic attacks and small strokes, are characteristic of primary CNS angiitis?
In addition to transient ischemic attacks and small cerebral strokes, sources for CNS vasculitis list clinical signs that should raise suspicion of the condition:
- severe headache;
- focal or multifocal neurological dysfunction;
- cognitive impairment;
- altered consciousness.
It is specifically noted for PACNS that it can manifest as episodes of small cerebral infarctions and TIAs involving multiple arterial territories.
"Media is spared" — upon histological examination of primary CNS angiitis, the tunica media remains intact, distinguishing it from other inflammatory angiopathies.
Class and exam questions
Can a diagnosis of primary CNS angiitis be established based solely on MRI and angiography data?
No, neuroimaging findings (white matter lesions, arterial stenoses) are non-specific. A definitive verified diagnosis requires a brain biopsy.
How to differentiate primary angiitis from reversible cerebral vasoconstriction syndrome (RCVS)?
In RCVS, CSF is typically normal, sudden thunderclap headache is characteristic, and angiographic changes are fully reversible within three months.
Do intracerebral hemorrhages occur in primary CNS angiitis?
Intracranial hemorrhages, such as parenchymal hematomas, are rare in this pathology. Ischemic strokes are far more characteristic.
What else to study on this topic
- Clinical and neuroimaging criteria for reversible cerebral vasoconstriction syndrome (RCVS).
- RCVS complications: cortical subarachnoid hemorrhage and PRES syndrome.
- Neurological complications of giant cell arteritis and polyarteritis nodosa.
- Infectious CNS vasculitides associated with varicella-zoster virus (VZV).
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