A man with hyponatremia, confusion, and involuntary limb movements

Abstract

Case presentationA 48-year-old Caucasian man presented to the Emergency Room with a 5-month history of involuntary movements of the limbs and confusion.His past medical history was negative for epilepsy, cancer, traumas, previous surgery, and psychiatric disorders. Four months before this evaluation, the patient was admitted to the Neurological Unit for involuntary limb movements. Neurological examination, electroencephalography (EEG), brain computed tomography (CT) scan and magnetic resonance imaging (MRI) were normal. Biochemical exams showed a moderate hyponatremia (129 mmol/L) that responded to fluid restriction. Psychiatric assessment led to the diagnosis of conversion disorder with comorbid anxiety. Clonazepam was prescribed, but his symptoms did not improve. Specifically, the patient reported sudden and brief episodes of involuntary limb movements, predominantly jerking of the arms, without incontinence or loss of consciousness. These episodes occurred several times a day, and they were often followed by minor falls. There was no obvious trigger, but he felt strange prior to the events. His wife noticed that he was confused, had poor memory, pronounced context-inappropriate sentences and had dramatically changed his behavior and personality. He denied headache, weight loss, fever, fatigue, pain, and gastrointestinal/pulmonary symptoms.The patient was physically active, did not smoke, and denied exposure to heavy metals/toxic agents, alcohol assumption, and use of illicit drugs. His only medication was clonazepam, and he was not on diuretics. He was under pressure for work-and family-related problems, as he was the owner of a pet shop and also had to look after his father with Alzheimer's disease and his brother with schizophrenia.Physical and neurological examinations were normal. Routine blood tests (Table 1) revealed hyponatremia (126 mmol/L) and increased creatine kinase levels (481 UI/L). EEG showed minimal non-specific abnormalities, and brain CT scan was normal.