Saphenous Neuralgia

Saphenous Neuralgia – The Clinical Syndrome

Saphenous neuralgia is an uncommon cause of medial calf pain that may occur after vascular surgery on the lower extremity.

With the increased number of total knee arthroplasties being performed, trauma to the infrapatellar branch of the saphenous nerve may cause damage, producing pain and numbness over the patellar tendon.

Patients with saphenous neuralgia often experience the medial pseudoclaudication type of pain that may confuse the clinical evaluation and lead the clinician to suspect lumbar spinal stenosis.

Saphenous neuralgia also may be due to compression of the nerve by tumor, hemorrhage, or abscess.

This compression usually occurs at the level at which the nerve exits from Hunter canal.

Stretch injuries to the saphenous nerve also can occur at this point. The nerve is subject to compression as it crosses to the medial knee.

Compression of the saphenous nerve at the knee is known as surfer’s knee because of compression of the saphenous nerve by the edge of the surfboard.

Diabetes can affect the saphenous nerve, but this is usually in conjunction with neuropathy of the other nerves of the lower extremity.

What are the Symptoms of Saphenous Neuralgia

A patient with saphenous neuralgia presents with pain that radiates into the medial calf to the medial malleolus. This pain may be paresthetic or burning; the intensity is moderate to severe.

There is no motor deficit associated with saphenous neuropathy, unless the spinal nerve roots or plexus or other peripheral nerves are involved. Patients with saphenous neuralgia may report a sunburned feeling over the distribution of the saphenous nerve.

How is Saphenous Neuralgia 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 suspected to have saphenous neuralgia. Plain radiographs of the spine, hip, pelvis, and femur are indicated in all patients who present with saphenous neuralgia to rule out occult bony pathological processes.

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, pelvis, and proximal lower extremity is indicated if tumor or hematoma is suspected.

Ultrasound imaging may also provide useful information regarding the status of the nerve. Injection of the saphenous nerve with a local anesthetic and steroid as it exits Hunter canal serves as a diagnostic and therapeutic maneuver.

Differential Diagnosis

It is difficult to separate saphenous neuralgia from a lumbar radiculopathy on purely clinical grounds, and electromyography is strongly recommended.

Electromyography and nerve conduction testing also help rule out the presence of peripheral neuropathy. Intrapelvic or retroperitoneal tumor or hematoma may compress the lumbar plexus and mimic the clinical presentation of saphenous neuralgia.

Treatment

Mild cases of saphenous neuralgia usually respond to conservative therapy, and surgery should be reserved for more severe cases. Initial treatment of saphenous neuralgia 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 saphenous neuralgia, tight control of blood glucose levels is mandatory.

Avoidance of repetitive activities thought to be responsible for the exacerbation of saphenous neuralgia helps ameliorate the symptoms.

The use of gabapentin or a tricyclic antidepressant such as nortriptyline as an adjuvant analgesic also may help ameliorate the symptoms of saphenous neuralgia. If the patient fails to respond to these conservative measures, a next reasonable step is injection of the saphenous nerve with a local anesthetic and steroid. 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 saphenous neuralgia that, if undiagnosed, could harm the patient, such as uncontrolled diabetes and retroperitoneal or pelvic tumor. The main side effect of saphenous nerve block is postblock ecchymosis and hematoma.

Potential exists for needle-induced trauma to the saphenous nerve. By advancing the needle slowly and then withdrawing the needle slightly away from the nerve, needle-induced trauma to the saphenous nerve can be avoided.

Clinical Pearls

Saphenous neuralgia always should be differentiated from lumbar plexopathy and radiculopathy of the nerve roots, which may sometimes mimic saphenous nerve compression.

Lumbar radiculopathy and saphenous 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 saphenous nerve is a simple and safe technique in the evaluation and treatment of the aforementioned painful conditions.

Careful neurological examination to identify preexisting neurological deficits that later may be attributed to the nerve block should be performed on all patients before beginning saphenous nerve block, especially in patients with clinical symptoms of diabetes or clinically significant saphenous neuralgia.


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