Abstract
We present a case report of unilateral PACNS in the context of polydrug use that posed diagnostic and therapeutic challenges.
A 36-year-old male presents with progressive short-term memory loss over the past year. He later disclosed that this was in the context of non-intravenous NMDA, amphetamines, cocaine and magic mushroom use. Initial magnetic resonance imaging (MRI) revealed a solitary right periventricular T2/FLAIR hyperintense lesion without diffusion restriction. Cerebrospinal fluid did not yield definitive infective cause or oligoclonal bands. Neurological and cognitive assessment were normal. A 6-month progress MRI demonstrated progression leading to his first brain biopsy, showing vasculitis features and no B-cell predominance. He represented two weeks later with a generalised seizure and MRI showing further progression of size and number of lesions in the right hemisphere while continuing polydrug use. Computer Tomography and FDG-PET were negative for malignancy screening, MR and CT angiograms were not suggestive of vasculopathy. Repeat CSF was unremarkable. A second brain biopsy was again suggestive of vasculitis, confirmed by the presence of granuloma. The patient was given a second pulse of methyl prednisone and commenced on cyclophosphamide for presumed diagnosis of PACNS after exclusion of even rare possible infections resulting in clinical and radiological improvement.
To date, there have been no reported unilateral PACNS associated with drug use. The main differential diagnosis remains lymphoma and previous treatment with steroids might cover pathological features. Although the exact cause remains elusive, treatment for PACNS could be considered in unilateral white matter lesion not responsive to pulse steroids.
