Seven shortcuts help with diagnosis of CNS vasculitis
EXPERT ANALYSIS FROM THE WINTER RHEUMATOLOGY SYMPOSIUM
• Mind the must-rule-outs
“Ask yourself,” Dr. Calabrese said, “‘What’s the worst thing that could happen here if I goof up this diagnosis?’”
The answer is the worst that can happen is that a CNS infection or malignancy gets misdiagnosed as PACNS. Those are the two must-rule-outs: infection – be it viral, tuberculosis, fungal, syphilis, bacteria, parasites, or Rickettsia – and malignancy.
“Malignancies can be insanely complex. Five percent of solid tumors will have leptomeningeal metastasis and present with chronic meningitis; that’s always goofing us up,” Dr. Calabrese said.
Intravascular CNS lymphoma is an important mimicker of PACNS. The affected patient may have headaches, punctate infarctions upon imaging, an abnormal CSF, and a mildly abnormal angiogram. The only way to distinguish it from PACNS is by brain biopsy.
“CNS lymphomas are always angiocentric, so unless you’ve got a really good pathologist and a really good biopsy specimen you may goof this up,” Dr. Calabrese cautioned.
• Failure to respond to cytotoxic agents and glucocorticoids suggests an alternative diagnosis, not refractory disease
It’s very unusual for a patient with PACNS to fail a robust course of cyclophosphamide or methotrexate plus steroids. This is a red flag situation warranting a pause to reconsider the diagnosis.
Other red flags commonly encountered by a consulting rheumatologists are that a neurologist diagnosed PACNS in the absence of a lumbar puncture, or on the basis of angiographic findings with a normal CSF.
Dr. Calabrese reported having no financial conflicts of interest.
