INTRODUCTION
Primary arteritis of the central nervous sytem (PACNS) is a relatively rare disease that can be devastating and very challenging to pinpoint. It causes multiple strokes or loss of blood flow in the brain.
PACNS is rare, with a reported prevalence of 2.4 cases per million person years. The majority of patients are men 2:1 women, and the mean age of patients diagnosed is 50 years old but the disease can occur at any age.
Common laboratory test abnormalities in patients with PACNS include:
Analysis of the CSF is a crucial part of the evaluation of patients with potential PACNS and should be performed in all patients unless there are contraindications. The importance of CSF analysis in excluding any infectious or malignant process and the performance of adequate stains and cultures of the CSF cannot be overemphasized. The CSF is abnormal in 80 to 90 percent of patients with pathologically documented disease. Normal CSF findings can occur with localized disease and in patients presenting with mass-like lesions. There are no specific abnormalities of the CSF in PACNS; however, the CSF findings in the majority of patients show an aseptic meningitis pattern with modest lymphocytic pleocytosis, normal glucose levels, elevated protein level, and occasionally the presence of oligoclonal bands and elevated IgG synthesis. By contrast, in the RCVS, the most common mimic of PACNS, the CSF analysis is usually normal or reflects findings of subarachnoid hemorrhage if this is present. [1]
Arteriography
Classic cerebral angiography studies in PACNS reveal findings of segmental narrowing referred to as "beading," usually in the medium and small arteries. Involvement of several sites of the cerebral circulation is typical of PACNS. Other findings include circumferential or eccentric vessel irregularities. While the findings are characteristic of cerebral arteritis, these findings are not specific, and may be encountered in non-vasculitic disorders such as atherosclerosis and vasospasm. [1]
Acute phase reactants such as the ESR and CRP are usually normal in PACNS. An elevated ESR and CRP should raise suspicion of systemic involvement by either an infectious or inflammatory process.[1]
MRI is sensitive in detecting abnormalities in PACNS and should be performed in all patients suspected to have PACNS. MRI of the brain commonly shows multiple infarcts in multiple vascular territories, and often in areas of the brain not affected by more common causes of stroke (such as the corpus callosum). However, these findings are not specific for PACNS and the interpretation of MRI findings should be performed by an expert neuroradiologist who is familiar with the findings of CNS vasculitis and its radiologic mimics. In addition, there may rarely be tumor-like lesions. Conversely, a negative MRI carries a high negative predictive value for the diagnosis of PACNS
MRA lacks both sensitivity and specificity for PACNS. Computed tomography angiography (CTA) may be more sensitive for detecting vascular irregularities than MRA, but is far less sensitive than catheter-based angiography.[1]
Conventional angiography remains an important part of the diagnostic testing for suspected PACNS, and experts obtain angiography in patients who have MRI findings of multiple cortical and subcortical infarcts that are otherwise unexplained. Angiography can detect segmental narrowing in multiple vessels that are typical of, though not pathognomonic for, PACNS, and help further rule out alternative diagnoses such as atherosclerosis, moyamoya, and dissection. These tests may also be helpful in selecting a location for brain biopsy if needed. [1]
[1]R Hajj-Ali, L Calabrese. PACNS. Uptodate.