Femoral Neuropathy

Femoral Neuropathy-The Clinical Syndrome

Femoral neuropathy is an uncommon cause of anterior thigh and medial calf pain that has many causes. Femoral neuropathy may be due to compression by tumor, retroperitoneal hemorrhage, or abscess.

Stretch injuries to the femoral nerve as it passes under the inguinal ligament from extreme extension or flexion at the hip also may produce the symptoms of femoral neuropathy. Direct trauma to the nerve from surgery or during cardiac catheterization and diabetes, which can produce vascular lesions of the nerve itself, also can produce this clinical syndrome.

Femoral neuropathy is also a known complication of total hip arthroplasty.

A patient with femoral neuropathy has pain that radiates into the anterior thigh and midcalf and is associated with weakness of the quadriceps muscle.

This weakness can result in significant functional deficit, with the patient unable to extend the knee fully, which can allow the knee to buckle, resulting in inexplicable falls. A patient with femoral neuropathy also may experience weakness of the hip flexors, making walking up stairs quite difficult.

What are the Symptoms of Femoral Neuropathy

The patient with femoral neuropathy has pain that radiates into the anterior thigh and medial calf. This pain may be paresthetic or burning; the intensity is moderate to severe.

Weakness of the quadriceps muscle can be quite marked, and over time atrophy of the quadriceps may occur, especially in patients with diabetes. Patients with femoral neuropathy may report a sunburned feeling over the anterior thigh. Patients also may report that the knee feels like it is giving way.

How is Femoral Neuropathy diagnosed?

Electromyography can help identify the exact source of neurological dysfunction and clarify the differential diagnosis and should be the starting point of the evaluation of all patients thought to have femoral neuropathy. Plain radiographs of the spine, hip, and pelvis are indicated in all patients with femoral neuropathy to rule out occult bony pathological conditions. Based on the patient’s clinical presentation, additional tests, including complete blood cell count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated. Magnetic resonance imaging (MRI) of the spine and pelvis is indicated if tumor or hematoma is suspected. Injection of the femoral nerve at the femoral triangle serves as a diagnostic and therapeutic maneuver.

Differential Diagnosis

It is difficult to separate femoral neuropathy from an L4 radiculopathy on purely clinical grounds. Subtle differences may exist because the L4 radiculopathy may manifest with sensory changes into the foot and weakness of the dorsiflexors of the foot. Intrapelvic or retroperitoneal tumor or hematoma may compress the lumbar plexus and mimic the clinical presentation of femoral neuropathy.

Treatment

Mild cases of femoral neuropathy usually respond to conservative therapy, and surgery should be reserved for more severe cases. Initial treatment of femoral neuropathy should consist of treatment with simple analgesics, nonsteroidal antiinflammatory drugs (NSAIDs), or cyclooxygenase-2 (COX-2) inhibitors and avoidance of repetitive activities that exacerbate the symptoms. If diabetes is thought to be the cause of the patient’s femoral neuropathy, tight control of blood glucose levels is mandatory. Avoidance of repetitive activities thought to be responsible for the exacerbation of femoral neuropathy (e.g., repetitive hip extension and flexion) also helps ameliorate the symptoms. If the patient fails to respond to these conservative measures, a next reasonable step is injection of the femoral nerve with a local anesthetic and steroid. The use of ultrasound guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications.

Complications and Pitfalls

It is imperative that the clinician rule out causes of femoral neuropathy that, if undiagnosed, could harm the patient, such as uncontrolled diabetes and retroperitoneal or pelvic tumor. The main side effect of femoral nerve block is postblock ecchymosis and hematoma. The potential exists for needle-induced trauma to the femoral nerve. By advancing the needle slowly and then withdrawing the needle slightly away from the nerve, needle-induced trauma to the femoral nerve can be avoided.

Clinical Pearls

Femoral neuropathy always should be differentiated from lumbar plexopathy and radiculopathy of the nerve roots, which sometimes may mimic femoral nerve compression. Lumbar radiculopathy and femoral nerve entrapment may coexist in the “double crush” syndrome. The double crush syndrome is seen most commonly with median nerve entrapment at the wrist.

Injection of the femoral nerve is a simple and safe technique in the evaluation and treatment of the previously mentioned painful conditions. Careful neurological examination to identify preexisting neurological deficits that may later be attributed to the nerve block should be performed on all patients before beginning femoral nerve block, especially in patients with clinical symptoms of diabetes or clinically significant femoral neuropathy.


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