Central causes of foot drop: rare and underappreciated differential diagnoses.

Background/objective: Peripheral causes of foot drop are well recognized. However, causes stemming from the central nervous system represent rare, important, and underappreciated differential etiologies.

Methods: Two cases of foot drop stemming from central causes are described.

Patients: The first patient, a 46-year-old man with a remote history of lumbar spine fracture and L4-L5 instrumentation/fusion, presented with progressive weakness and numbness of the left foot, followed within 3 months by similar symptoms in the right foot. Lumbar spine imaging failed to reveal compressive nerve root pathology. Electromyography, nerve conduction studies, and muscle and nerve biopsy suggested a preganglionic lesion and ruled out a peripheral cause. Upper spine magnetic resonance imaging (MRI) revealed significant spinal stenosis at C4-C7 and T11-T12. Patient 2 was a 66-year-old man with a known left parasagittal convex meningioma diagnosed 2 years prior presented with a progressive right foot drop over 2 months. Spine imaging was normal, and serial brain MRI confirmed a slowly enlarging parasagittal meningioma.

Results: Following decompressive laminectomies at C4-C7 and T11-T12, patient 1's gait improved, with marked resolution of his right foot drop and significant improvement on the left. Patient 2 underwent craniotomy for microsurgical tumor resection. At the 2-week follow-up examination, he was taking daily walks.

Conclusions: Central causes, although rare, need to be considered in the differential diagnosis of foot drop. Central causative lesions usually occur at locations where pyramidal tract connections are condensed and specific and the function is somatotopically organized. These cases confirm that good results can be achieved when correctable central causes of foot drop are recognized.