An Uncommon Presentation of Guillain-Barré Syndrome With Lhermitte Sign.

Guillain-Barré syndrome (GBS) is a complex and potentially life-threatening disease, representing the most common cause of acute neuromuscular paralysis worldwide. Its diagnosis is primarily based on clinical findings, often complemented by electrophysiological studies and laboratory investigations. Therefore, knowledge of the clinical signs and symptoms is essential to make a prompt diagnosis and allow timely initiation of therapeutic interventions. Despite significant advancements in our understanding of this disease, many aspects of its nature are yet to be fully understood. We present a compelling case that initially manifested with the Lhermitte sign, followed by the development of paresthesias and diminished muscle strength originating in the upper extremities and progressing in a cephalocaudal pattern. These initial findings suggest a pathology involving the cervical spinal cord or nerve roots. However, the patient's evolving neurological deficits and subsequent diagnostic studies revealed an unexpected etiology: GBS. This case highlights the importance of maintaining a broad differential diagnosis, even when confronted with seemingly characteristic clinical presentations. It also reveals the complexity of GBS, a disease that can present with potential atypical manifestations that can mimic other neurological disorders.