934 - Rapidly Progressive Quadriceps Weakness: Femoral Neuropathy, Lumbar Radiculopathy or Neurogenic Claudication?

Case Diagnosis: Femoral neuropathy, lumbar radiculopathy, and neurogenic claudication may present with overlapping symptoms such as anterior thigh pain, weakness, and gait dysfunction, making early diagnosis challenging. Accurate differentiation is critical for timely intervention, particularly in older adults where presentations can be atypical or rapidly progressive.

Case Description: A 71-year-old male developed sudden-onset low back pain after lifting a heavy object. Initial symptoms included anterior thigh paresthesia, burning pain, and testicular discomfort. Exam revealed left quadriceps atrophy, inability to extend the knee, preserved hip flexion and sensation, negative straight leg raise, sensory loss over the left saphenous distribution, and visible quadriceps fasciculations. Left patellar reflex could not be tested due to prior total knee replacement. The differential included femoral nerve impingement versus lumbar radiculopathy. Lumbar MRI showed severe spinal canal stenosis and moderate to severe bilateral neuroforaminal narrowing at L3–4 and L4–5, expanding the differential to include neurogenic claudication. Symptoms progressed within two months to left leg dragging and significant gait impairment, requiring emergent spinal decompression with rapid improvement.

Discussions: While both femoral neuropathy and lumbar radiculopathy may present with anterior thigh pain, sensory loss, and weakness of hip flexion and knee extension, femoral neuropathy causes deficits confined to the femoral nerve distribution. Lumbar radiculopathy may involve additional dermatomes or myotomes. Neurogenic claudication from lumbar stenosis often causes posture-dependent bilateral symptoms involving multiple root levels. This case illustrates diagnostic complexity when anterior thigh symptoms are present. Rapid progression and multilevel findings favored a central cause despite initial features mimicking peripheral neuropathy. Electrodiagnostic studies and imaging are essential when the clinical picture is unclear.

Conclusions: Early identification of neurogenic causes of anterior thigh pain and weakness is crucial to avoid irreversible deficits. This case highlights the need for a broad differential and appropriate diagnostic workup, especially in older adults with symptoms resembling benign musculoskeletal injuries.