Lessons of the month: HLA-B27-associated syndrome and spontaneous intracranial hypotension resulting in behavioural variant frontotemporal dementia.

Spontaneous intracranial hypotension is uncommon and results from a cerebrospinal fluid (CSF) leak. We describe the case of a marathon runner who presented with postural headache attributable to CSF venous fistulation originating from a lower thoracic nerve root cyst. Subsequent investigations confirmed a unifying diagnosis of human leukocyte antigen B27-associated syndrome.