Key Clinical MessageHyponatremia is a common electrolyte disturbance seen among the acute geriatric admissions with two common diagnostic entities; the syndrome of inappropriate antidiuretic hormone (SIADH) and cerebral salt wasting syndrome (CSWS) that have different clinical and biochemical presentations, different pathogenesis and therapeutic approaches. Hyponatremia caused by CSWS in patients with cerebral small vessel disease (cSVD) a prevalent condition among the elderly, can be masked in geriatric patients with concomitant fluctuating neurological deficits. Correct diagnosis is crucial to appropriate management. In this case report we describe an association between hyponatremia caused by CSWS in a patient with cSVD.