Introduction Primary CNS angiitis is a challenging diagnosis to make. Without treatment it is relentlessly progressive and fatal.

Case A 44 year old gentleman from Sierra Leone presented to A&E with a 4.5 hour history of left facial weakness and slurred speech. CT was normal and a diagnosis of minor stroke made. The patient was discharged on Clopidogrel and Simvastatin, with outpatient MRI.

2 weeks later the patient re-presented with a 3 day history of worsening left sided hemi-chorea. MRI revealed diffuse right hemisphere vasculopathy. Routine bloods, thrombophilia, infection and autoimmune screens were normal, as were carotid doppler's, ECHO, CXR and CSF. 24 hr ECG revealed bursts of AF. The patient was diagnosed with paroxysmal AF and discharged with a follow up MRI, which revealed worsening vasculopathy.

A brain biopsy was arranged, showing non-specific chronic inflammation with focal non-necrotising granulomatous vasculitis, confirming ‘Primary CNS Angiitis’. The patient was treated with Prednisolone and Cyclophosphamide, making a full recovery.

Discussion Making this diagnosis is challenging, as brain imaging often shows non specific changes and blood results are usually normal. CSF may reveal raised proteins and WBCs. A high index of suspicion is required to arrange a brain biopsy as this confirms the diagnosis.