Which symptom is a clear sign of Guillain-Barre Syndrome?

Acute demyelination is the hallmark of Guillain-Barre Syndrome (GBS). This condition is characterized by the immune system mistakenly attacking the peripheral nerves, leading to demyelination, which is the loss of the protective myelin sheath surrounding these nerves. This demyelination results in a variety of symptoms, primarily muscle weakness and sensory disturbances, often starting in the lower extremities and potentially progressing to cause significant complications, including respiratory failure in severe cases.

While severe headache, muscle spasms, and extreme fatigue can occur in various conditions, they are not defining features of GBS. The acute nature of the demyelination in GBS is critical for diagnosis and distinguishes it from other neurological conditions. Acute demyelination can lead to the rapid development of motor weakness, often described as "ascending paralysis," which is a classic presentation of Guillain-Barre Syndrome.