Which symptom is characteristic of Guillain-Barre syndrome?

Guillain-Barre syndrome is primarily characterized by progressive muscle weakness that typically starts in the lower extremities and can ascend to involve the upper body and respiratory muscles. This ascending weakness is a hallmark feature of the condition and is often preceded by an infection. Patients may experience sensations such as tingling or numbness, but the most defining symptom is indeed the weakness in the lower extremities.

The other symptoms listed, while they may occur due to various neurological conditions, are not as specifically associated with Guillain-Barre syndrome as the weakness of the lower extremities. Facial droop, difficulty swallowing, and hand tremors can be seen in other neurological disorders but do not capture the essence of what is typically observed in Guillain-Barre syndrome.