Aim and background: Hyponatremia is a common electrolyte disorder in the setting of neurological disease. Among patients with neurological disorders, syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the common malady, and cerebral salt wasting syndrome (CSWS) is rarely encountered. In SIADH, there is usually increased or normal intravascular volume, and in CSWS, there is central volume depletion. Thus, proper clinical examination of central volume status should be done before making a diagnosis. Case description: A 73-year-old man presented with drowsiness 2 years ago. Serum sodium was low, and he was advised by a physician to take extra salt supplementation. His confusion worsened, he developed gait instability, urinary incontinence, and was diagnosed as having normal pressure hydrocephalus (NPH). A ventriculo peritoneal (VP) shunt was placed. Later in the year, he was again admitted to the hospital with drowsiness. He was diagnosed with SIADH and treated with water restriction and tolvaptan. A year later, he became drowsy and was admitted to this hospital. Serum sodium was low, and he had central volume depletion. He was diagnosed with CSWS. The worsening was due to the change in VP shunt pressure as he walked through a metal detector, which led to excessive drainage of cerebrospinal fluid (CSF). He was treated with hydration, salt supplementation, and shunt pressure adjustment, leading to improvement in his condition. Conclusion: CSWS is a rare metabolic manifestation of NPH. Patients with VP shunts should be cautioned against walking through a metal detector with a potential electromagnetic field. Clinical significance: Clinical assessment of jugular venous pressure (JVP) is important in order to differentiate between SIADH and CSWS.