227 - Bilateral Foot Drop as the Main Sign of Extensive Syringomyelia: When Electrodiagnostic Studies Lead Astray

A 20-year-old female was admitted with progressive bilateral ankle dorsiflexion weakness and steppage gait, accompanied by lower-limb ataxia, proprioceptive and thermal sensory disturbances, nociceptive impairment in the upper limbs, persistent headache and neck heaviness over the previous five months. Electrodiagnostic studies revealed a chronic mixed polyradiculoneuropathy affecting the lower limbs. Lumbar MRI initially showed an L5–S1 disc protrusion. She was treated in the neurology department with steroid pulses, followed by five days of intravenous immunoglobulin, with no significant clinical improvement. Given the upper-limb symptoms, cervical and dorsal MRI were performed, revealing extensive syringomyelia associated with Chiari malformation type I. A suboccipital decompression was performed. At 6-months follow-up, all symptoms completely resolved.

Discussions: This case highlights the diagnostic challenge of extensive syringomyelia presenting with bilateral foot drop, a symptom that can easily mimic peripheral neuropathies. It emphasizes the importance of considering the entire clinical picture rather than relying on a single diagnostic study. Prompt differentiation between central and peripheral causes of progressive weakness is essential, as misdiagnosis can delay appropriate intervention and adversely affect neurological outcomes. Previous studies show unilateral foot drop as a common motor-related deficit in syringomyelia, while bilateral involvement remains rare.

Conclusions: Syringomyelia should be included in the differential diagnosis of bilateral foot drop, especially when associated with mixed sensory deficits and ataxia. Timely neuroimaging is essential to avoid misdiagnosis and optimize functional outcomes.