Abdominal Pain Followed by Altered Mental Status: A Rare Presentation of Guillain Barré Syndrome

Guillain Barré syndrome (GBS) is an acute inflammatory polyneuropathy with several variants; it usually presents as acute symmetrical muscle weakness with or without bulbar involvement, making it a neurological emergency. In this report, we describe the case of a 39-year-old male who presented with abdominal pain for three days and whose illness became progressively drowsy on the fifth day. Based on clinical assessment, nerve conduction studies, and biochemical, microbiological, and radiological investigations, other causes were ruled out and it was concluded that the patient had hyponatremia secondary to syndrome of inappropriate diuretic hormone secretion (SIADH) due to GBS. Although sensory symptoms like pain or dysaesthesias occurring in the back or extremities are common and may precede motor weakness, abdominal pain remains a very rare presentation of GBS. GBS is usually understood as a "pure" peripheral nervous system disorder but central nervous system (CNS) dysfunction may occur due to metabolic abnormalities (like hyponatremia and CO₂ narcosis) or autonomic dysfunction in GBS, its treatment, or due to GBS itself (Anti-GQ1b disease variant).