Document resource
Autoimmune small-vessel cerebral vasculitis is an uncommon but potentially reversible cause of rapidly progressive cognitive and neurological decline. Its presentation can be heterogeneous, often mimicking vascular, infectious or degenerative processes. Hyponatraemia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) may occur as a secondary manifestation of hypothalamic involvement or systemic inflammation, compounding neurological dysfunction and complicating management. We describe a middle-aged woman who developed acute cognitive deterioration, emotional lability and gait disturbance secondary to newly diagnosed autoimmune small-vessel vasculitis with serological evidence of systemic autoimmunity, on a background of prior polyautoimmune diseases (type 1 diabetes mellitus and hypothyroidism). Despite resolution of inflammatory activity following high-dose corticosteroid therapy, profound hyponatraemia (serum sodium 110–120 mmol/L) persisted despite conventional measures (fluid restriction, salt supplementation and urea) and despite improvement in inflammatory activity following immunotherapy, consistent with refractory SIADH. Initiation of tolvaptan, a selective vasopressin V2-receptor antagonist, successfully resulted in gradual and sustained correction of serum sodium levels without over-rapid correction, osmotic demyelination or hepatic toxicity. Alongside longer-term immunosuppression with steroids and cyclophosphamide, this led to stabilisation of neurological and cognitive deficits. This case highlights the complexities of managing patients with cognitive and neuropsychiatric sequelae from autoimmune small-vessel central nervous system (CNS) vasculitis and the importance of evaluation and treatment of potential organic causes of cognitive impairment. To our knowledge, there are no prior published reports describing refractory SIADH in autoimmune small-vessel CNS vasculitis requiring V2-receptor antagonism. Awareness of this disease association and this effective therapeutic option allows earlier recognition and improved patient outcomes in similar cases.