Femoral/saphenous neuropathy

Signs and symptoms-- weakness and atrophy of the quadriceps muscle, reduced knee reflex, sensory disturbance over the anterior thigh/medial calf.

PEARLS

1) HIP FLEXOR MUSCLES MUST BE TESTED AND IF THEY ARE INVOLVED IT SIGNIFIES INVOLVEMENT OF LUMBAR PLEXUS.

2) ELDERLY PATIENTS MAY STATE THAT THEIR LEG COLLAPSED OR THAT THEY CANNOT ELEVATE THE LEG SUFFICIENTLY TO CLIMB STAIRS WITHOUT RECOGNIZING THE WEAKNESS OF THE MUSCLE AFFECTED.

Etiologies are many. Biemonds studied 50 patients. Four had retroperitoneal tumors, one retroperitoneal hematoma (often due to bleeding diathesis, six had lacerations or trauma, six had femoral neuropathy from diabetes, fifteen had radiculopathy masquerading as femoral neuropathy, eighteen were unknown included elderly and postulate was that they were diabetic or vascular). Iatrogenic causes include trauma after attempted femoral arterial puncture or catheterisation, intrapelvic operations with bleeding ( including renal transplant) or stretch due to marked extension or flexion of the hip. This can occur with coma after intoxication, or during childbirth, especially with poorly padded stirrups used in patients already numb from an epidural injection.

EMG PEARLS
1) Femoral nerve slowing can be further evaluated by saphenous nerve conductions (if abnormal its not radiculopathy). Plexus lesions have normal femoral motor nerves, abnormal saphenous nerve conductions, and EMG abnormalities outside femoral nerve territory (check....) L4 radiculopathy shows EMG abnormality ooutside L4 myotome including paraspinal muscles (check...) Saphenous nerve involvement (one of three branches of the femoral nerve) produces abnormal sensation on medial calf. May get Tinel's sign along nerve anywhere from Hunter's canal above knee. Can occur from procedures in Hunter's canal or at knee. EMG of femoral neuropathy: often more useful than NCS. Examine lumbar paraspinals and obturator innervated muscles. EMG femoral innervated muscles: VM, RF, iliopsoas; obturator (adductor longus); superior gluteal nerve (TFL), and lumbar paraspinal muscles. ADD-- 4 fb distal to pubic tubercle , adducts limb.