History
Iliohypogastric nerve entrapment
Symptoms of iliohypogastric nerve entrapment include burning or lancinating pain immediately following an abdominal operation. The pain extends from the surgical incision laterally into the inguinal and suprapubic regions. Discomfort may occur immediately or as long as several years after the procedure and may last for months to years. This discomfort may derive from the formation of scar tissue in the region. Occasionally, the pain may extend into the genitalia because of significant overlap with other cutaneous nerves.
Loss of sensation is usually minimal and not problematic. Iliohypogastric nerve entrapment causing symptoms similar to trochanteric bursitis refractory to conventional therapy has been reported.
Ilioinguinal nerve entrapment
Symptoms of ilioinguinal nerve entrapment may include hyperesthesia or hypoesthesia of the skin along the inguinal ligament. The sensation may radiate to the lower abdomen. Pain may be localized to the medial groin, the labia majora or scrotum, and the inner thigh. The characteristics of the pain may vary considerably. Patients may be able to associate their pain clearly with a traumatic event or a surgical procedure.
In as many as 75% of patients, pain and tenderness may be present when pressure is applied where the nerve exits the inguinal canal. Sensory impairment is common in the distribution of the nerve supply. Symptoms usually increase with hip extension (patients walk with the trunk in a forward-flexed posture). Pain may also be reproduced with palpation medial to the anterior superior iliac spine (ASIS).
Genitofemoral nerve entrapment
Injury to the femoral branch of the genitofemoral nerve causes hypoesthesia over the anterior thigh below the inguinal ligament; this finding distinguishes entrapment of this nerve from entrapment of the iliohypogastric or ilioinguinal nerve. Groin pain is a common presentation of neuralgia from nerve injury or entrapment. The pain may be worse with internal or external rotation of the hip, with prolonged walking, or even with light touch.
Femoral nerve entrapment
Symptoms of a femoral neuropathy may include pain in the inguinal region that is partially relieved by flexion and external rotation of the hip, as well as dysesthesia over the anterior thigh and anteromedial leg. Patients complain of difficulty in walking and of knee buckling, depending on the severity of the injury. The femoral nerve gives rise to the saphenous nerve in the thigh; therefore, numbness in this distribution can be present. Anterior knee pain may also be present because the saphenous nerve supplies the patella.
Lateral femoral cutaneous nerve entrapment
Symptoms of lateral femoral cutaneous nerve entrapment may include anterior and lateral thigh burning, tingling, and numbness, which increase with standing, walking, or hip extension (and sometimes also with lying prone). Symptoms usually are unilateral but may be bilateral in rare cases. Sitting usually yields improvement, unless compressive forces, such as tight belts or garments, remain.
Saphenous nerve entrapment
Symptoms of saphenous nerve entrapment may include a deep thigh ache, knee pain, and paresthesias in the nerve’s cutaneous distribution in the leg and foot. The infrapatellar branch may become entrapped on its own because it passes through a separate foramen in the sartorius tendon. It may also be exposed to trauma where it runs horizontally across the prominence of the medial femoral epicondyle. Patients report paresthesias and numbness in the infrapatellar region that worsen with knee flexion or compression by garments or braces.
Saphenous nerve entrapment is a frequently overlooked cause of persistent medial knee pain in patients who experience trauma or direct blows to the medial aspect of the knee. Because the saphenous nerve is purely sensory, an isolated injury to this nerve should not result in weakness. If weakness is present, the examiner should look for an injury to the femoral nerve or, possibly, an upper lumbar radiculopathy, particularly if thigh adduction is present (obturator nerve).
Obturator nerve entrapment
The main complaints in obturator nerve entrapment include difficulty with ambulation and the development of an unstable leg. In an anterior branch entrapment, symptoms can consist of exercise-related pain or groin pain. The patient may describe a deep ache in the region of the adductor origin at the pubic bone that increases with exercise; the pain may radiate down the medial aspect of the thigh toward the knee. An athlete’s ability to jump may be reduced. The weakness in these patients usually worsens with exercise.
Posterior tibial nerve entrapment
Patients with proximal tarsal tunnel syndrome usually present with diffuse, vague discomfort or pain. They may have burning, tingling, or frank numbness in the plantar foot. Although occasionally a history of trauma is reported, most patients report an insidious onset of symptoms.
In most instances, symptoms are unilateral. Occasionally, patients may report proximal radiation of pain to the medial leg. Prolonged standing and walking usually exacerbate the symptoms, and rest alleviates them. Many patients also present with night pain that is improved with massage or walking. Patients may note pain secondary to nerve tension when the ankle is placed in extreme dorsiflexion.
Patients with distal entrapment of the lateral plantar nerve or its branches usually present with chronic heel pain that has been present for 9-12 months. Many of their symptoms are similar to plantar fasciitis, especially the location of their pain and their startup pain. In addition to the mechanical symptoms of plantar fasciitis, they present with neuritic pain that is unrelated to weight bearing or loading of the foot.
Most patients report that at first, their symptoms occurred only when they were bearing weight. Over time, the symptoms tended to increase, eventually occurring when the patient was seated and occasionally occurring at night.
Patients are usually asymptomatic in the mornings before taking their first step. Symptoms usually worsen with increased activity, as well as toward the end of the day and after long periods of standing, walking, or running. Prolonged standing in one place may be an aggravating factor. Most patients continue to have pain or burning (“afterpain” or “afterburn”) for 30 minutes to several hours after they are off their feet.
Tarsal tunnel syndrome is seen commonly in individuals who are in their fifth and sixth decades of life, and it is more common in women than in men. No consistent correlation with patient body weight has been identified. Most investigators have not been able to identify a significant common factor regarding occupation or underlying foot structure.
Some patients with tarsal tunnel syndrome have concomitant peripheral neuropathy or radiculopathy. Patients with peripheral neuropathy or radiculopathy may have symptoms that mimic tarsal tunnel syndrome.
Patients with certain systemic diseases, such as diabetes mellitus, alcoholism, thyroid disease, and vitamin deficiencies, are at increased risk for entrapment neuropathy.
Common peroneal nerve entrapment
Peroneal nerve lesions at the region of the knee or distal thigh usually result in patient reports of altered ambulation secondary to paretic or paralyzed ankle dorsiflexors. Loss of sensation in the cutaneous distribution of the superficial and deep peroneal nerves may be noted, but ankle dorsiflexion weakness is often of most concern to the patient. [37]
Pain is not universal with common peroneal nerve injuries; if present, it is often related to the specific cause of the nerve compromise. For example, nerve compromise secondary to traumatic injury from blunt trauma will likely be accompanied by pain secondary to soft-tissue swelling and inflammation, whereas chronic compression secondary to habitual leg-crossing is often nonpainful. Tapping of the nerve at the fibular head may produce pain and tingling (Tinel sign) in the sensory distribution of the peroneal nerve.
Superficial peroneal nerve entrapment
With superficial peroneal nerve entrapment, though patients may present with numbness or paresthesia in the distribution of the nerve and occasionally have pain about the lateral leg, the most typical presentation is vague pain over the dorsum of the foot. This pain may be chronic, remaining present for several years, and may be associated with other foot and ankle symptoms; on the other hand, it may be acute and associated with recent trauma or surgery about the ankle.
Specific measure that put the superficial peroneal nerve at risk for direct or stretch injury include the use of the anterolateral arthroscopy portal and the use of noninvasive traction methods with straps over the dorsum of the foot. About one quarter of patients have a history of previous or recurrent ankle sprains or trauma.
Typically, symptoms increase with activity (eg, running, walking, or squatting); they are often relieved by rest or the avoidance of a specific activity. This tendency is particularly pronounced in athletes whose symptoms are suggestive of exertional or chronic anterolateral compartment syndrome.
Bony entrapment of the superficial peroneal nerve in the fracture callus has also been reported when fractures of the fibula heal with abundant callus.
Certain positions (eg, crossing the leg over the opposite thigh) can induce symptoms, as can tight clothing (eg, sock elastic over the lateral leg). Pain may occasionally occur at night. Occasionally, patients report a bulging mass in the leg.
Deep peroneal nerve entrapment
Patients with deep peroneal nerve entrapment commonly complain of vague pain, a burning sensation, or a cramp over the dorsum of the foot, which may or may not involve the first webspace. Associated sensory changes may be noted in the first dorsal webspace. Some patients may present with neuritic symptoms (eg, unrelenting pain at rest and during sleep) along the course of the nerve. There may be pain in the ankle region even if only the motor nerve is involved.
Symptoms may appear or worsen only with a certain shoe or boot or with certain activities. Patients with more proximal entrapment may present with frequent tripping due to foot drop or weakness of the extensor halluces longus, though such a presentation is less common.
Interdigital neuritis
Many patients with interdigital neuritis (also known as Morton neuroma, Morton metatarsalgia, interdigital neuroma, or interdigital nerve compression) present with an intermittent dull ache or cramping sensation on the plantar aspect of either the second or the third interspace. Many patients present with a vague discomfort in the involved toes, and some may feel numbness or burning, with occasional shooting pain. Some patients notice spreading of the involved toes, and others may notice symptoms only with certain shoes.
Symptoms are usually exacerbated by walking, particularly with bare feet on hard surfaces, and sudden sharp pain may result from various activities (eg, sprinting, jumping, squatting, or repeated hopping) or from the wearing of high-heeled or tight shoes. Symptoms improve with rest, and night pain is rare. With progression of the condition, pain may radiate proximally. In chronic cases, patients may sense a mass or a stone bruise in the ball of the foot.
Nearly equal involvement of the second and third interspaces has been reported in the literature; involvement of the first and fourth spaces also has been reported, albeit rarely. Simultaneous tenderness in the second and third interspaces is not rare. Bilateral cases have been reported but are uncommon. Other pathologies of the forefoot (eg, instability of the second metatarsophalangeal [MTP] joint) are frequently present. Coughlin et al reported that 20% of their patients originally had concomitant instability of an adjacent MTP joint.
Clinically, dorsoplantar compression of the second or third intermetatarsal space reproduces pain that may radiate to the toes or proximally along the course of the affected nerve. The patient may display relative paresthesia of the webspace supplied by the injured nerve, though this relative paresthesia is often difficult to ascertain.
Physical Examination
Iliohypogastric nerve entrapment
On examination, pain and tenderness are usually present in the area of scarring or entrapment of the iliohypogastric nerve. Hyperesthesia or hypoesthesia may occur in the area supplied by this nerve. Diagnosis is difficult, owing to the small area of cutaneous supply that this nerve provides. There may be overlap in sensory supply with the genitofemoral and ilioinguinal nerves.
The following three major criteria are used to diagnose iliohypogastric nerve entrapment:
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History of a surgical procedure in the lower abdominal area (though spontaneous entrapment can occur) - Pain can usually be elicited by palpating laterally about the scar margin, and the pain usually radiates inferomedially toward the inguinal region and into the suprapubic and proximal genital area
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A definite area of hypoesthesia or hyperesthesia identified in the region of supply of the iliohypogastric nerve
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Symptoms relieved by local anesthesia - Infiltration of a local anesthetic into the region where the iliohypogastric and ilioinguinal nerves depart the internal oblique muscle and where symptoms can be reproduced on physical examination by palpation should provide symptomatic relief
If no relief is obtained with injection, a different cause of the discomfort should be sought. Alternate diagnoses include upper lumbar or lower thoracic nerve root pathology and pain of discogenic origin. If the iliohypogastric nerve is clearly identified as the source of pain and a favorable response is not obtained with local anesthetic injection, then surgical exploration and resection of the nerve should be considered.
Ilioinguinal nerve entrapment
The diagnosis of ilioinguinal nerve entrapment can be made on the basis of local infiltration of anesthetic with or without steroid, which should result in relief within 10 minutes.
Genitofemoral nerve entrapment
The diagnosis of genitofemoral nerve entrapment is typically made by using anesthetic nerve blocks. Injection of the ilioinguinal and iliohypogastric nerves anteriorly should leave the pain or abnormal sensation unchanged; a block of the L1 and L2 roots should then result in relief. This procedure should help determine the diagnosis and prevent unnecessary surgical exploration of an uninjured nerve.
Femoral nerve entrapment
On examination, patients with femoral nerve entrapment may present with weak hip flexion, weak knee extension, and impaired quadriceps tendon reflex, as well as sensory deficit in the anteromedial aspect of the thigh. Pain may be increased with hip extension and relieved with external rotation of the hip. If compression occurs at the inguinal region, no hip flexion weakness is present. Sensory loss may occur along the medial aspect of the leg below the knee (saphenous distribution).
Lateral femoral cutaneous nerve entrapment
In some cases of lateral femoral cutaneous nerve entrapment, physical examination findings may be completely normal. Hyperesthesia over the lateral thigh (usually in a smaller area than the symptoms) may be noted. Pain can be produced by pressure medial to the ASIS. A positive Tinel sign may be present over the ASIS or the inguinal ligament.
Diagnosis of this entrapment, like that of other lower-extremity nerve entrapments, may be based on an injection of local anesthetic near the inguinal ligament or the ASIS. Spontaneous recovery usually is expected.
Saphenous nerve entrapment
In cases of saphenous nerve entrapment, deep palpation proximal to the medial epicondyle of the femur may reproduce the pain and complaints. Some weakness may be present because of guarding or disuse atrophy from pain, but no direct weakness will result from the nerve impingement. Sensory loss in the saphenous distribution may be present on examination. No weakness should be present in the quadriceps muscles or in the hip adductors.
The diagnosis may be made on the basis of injection of local anesthetic along the course of the nerve and proximal to the proposed site of entrapment. Nerve conduction techniques are available to assess neural conduction in the main branch of the saphenous nerve or in the terminal branches. The routine tests may be disappointing in persons with subcutaneous adipose tissue or swelling.
A side-to-side comparison of the nerve should be made and must demonstrate a lesion consistent with the patient’s complaints. A somatosensory evoked potential (SSEP) test can also be performed and the results compared with those of the contralateral side for diagnosis, though this test may be cumbersome and time-consuming.
Obturator nerve entrapment
With severe injuries to the obturator nerve, loss of adduction and internal rotation occur, and the typical gait pattern is that of an externally rotated foot. Examination reveals wasting of the adductor muscles of the thigh and, possibly, diminished sensation along the medial thigh distally.
The differential diagnosis includes adductor muscle strain, osteitis pubis, stress fracture of the pelvis, inguinal ligament enthesopathy, entrapment of the lateral femoral cutaneous nerve, and inguinal hernia. A nerve block may be helpful but usually is not necessary for diagnosis.
Posterior tibial nerve entrapment
The diagnosis of tibial nerve entrapment, or tarsal tunnel syndrome (proximal and distal), is based primarily on a detailed history and physical examination. Further screening studies (eg, laboratory workup for arthritides, diabetes, alcoholism, and thyroid dysfunction) are indicated in cases of associated inflammation and in patients with symptoms of peripheral neuropathy (see Workup).
Inspection of the patient while he or she is standing and walking allows the examiner to evaluate for alignment deformities, such as hindfoot varus or valgus, swelling, varicosities, or other skin changes.
Palpation of the pulses is used to evaluate the patient’s distal circulation. Sensory examination, including Semmes-Weinstein monofilament testing of the entire foot, may reveal dermatomal numbness due to compression neuropathy, or could reveal peripheral neuropathy.
The range of motion of the ankle, subtalar, and the midfoot joints is examined, and any limitations are noted. Pain may increase with dorsiflexion and eversion or inversion of the foot; these positions increase tarsal compartment pressure. [28] Motor examination should include asking the patient to spread the toes to facilitate assessment of the abductor digiti minimi and, if appropriate, the abductor hallucis. Hypertrophy of the abductor hallucis or an accessory muscle may also be present, with fullness in the longitudinal arch.
Patients with proximal tarsal tunnel syndrome often have ganglia, tenosynovitis, or other space-occupying lesions in the tarsal tunnel that may be palpable. They may also have positive Tinel signs along the tibial nerve. Occasionally, nerve percussion causes symptoms and pain to radiate proximal to the nerve course (the so-called Valleix phenomenon). Linscheid noted that in most of his patients with proximal tarsal tunnel syndrome, manual compression of the nerve at the tarsal tunnel for 60 seconds reproduced their symptoms. [38]
Patients with distal tarsal tunnel syndrome usually have the most severe tenderness over the first branch of the lateral plantar nerve over the plantar medial heel and under the abductor hallucis. Many patients have tenderness along the entire tibial nerve, starting from behind the distal medial malleolus. Additional tenderness is usually present over the plantar fascia insertion on the medial calcaneal tuberosity and sometimes along the entire medial edge of the plantar fascia. The Tinel sign is usually absent.
The deep tendon reflexes and straight-leg raise are evaluated with an eye to detecting any isolated or concomitant radiculopathy. Hamstring tightness is evaluated with both legs extended.
Patients with entrapment of the medial plantar nerve have tenderness over the medial arch inferior to the navicular tuberosity, but not directly over the plantar fascia. Pain may radiate to the medial toes and the ankle. Numbness or a Tinel sign over this area may be present only after prolonged weightbearing exercise. Occasionally, orthotic use may be correlated with the onset of the symptoms. Stretching of the nerve as a result of eversion of the foot or of standing on the toes may reproduce or exacerbate symptoms.
Common peroneal nerve entrapment
The history and physical examination are the most helpful initial clinical tools in establishing a high index of suspicion for a common peroneal nerve injury. Nerve biopsy, though largely unnecessary, may confirm the diagnosis.
Observation of the patient’s gait is useful in diagnosing ankle dorsiflexion weakness. A patient with common peroneal nerve entrapment often displays a steppage gait pattern, in which the affected foot is lifted excessively from the ground during the swing phase of ambulation in order to clear the foot. This results in excessive hip and knee flexion, and the appearance is as if the patient is stepping over an object in his or her path.
In addition, a foot slap may be heard on foot strike because of the inability of the ankle dorsiflexors to provide a controlled descent of the foot toward the floor. The patient may also stumble when walking as a consequence of the toes on the affected side dragging or catching on the floor during the swing-through phase of ambulation.
Examination often reveals a variable pattern of weakness, with the extensor digitorum brevis most profoundly affected. Ankle and toe dorsiflexion may be substantially altered. Dorsiflexion is best tested by having the patient place the ankle in the neutral position and then dorsiflex the foot and invert; this tests the anterior tibial muscle optimally. Often, ankle eversion is normal because the relevant muscles are relatively spared.
In a pure common peroneal neuropathy, plantar flexion should be spared. In fibular neck fractures, complete absence of sensation is possible along the anterodistal portion of the leg and the entire dorsum of the foot. Lateral calf sensation may be spared if the lesion is below the nerve branch to this region. When the neural insult occurs at the knee, the short head of the biceps femoris often is spared.
Superficial peroneal nerve entrapment
In the setting of suspected superficial peroneal nerve entrapment, examination should include the entire course of the nerve, starting from the lower back and extending through the sciatic notch, the proximal fibula, and the lateral leg, where a muscle bulge due to a fascial defect may be palpated in some patients.
Percussion along the superficial course of the nerve over the proximal fibula, lateral leg, or anterior ankle may result in a positive Tinel sign, with reproduction of radiating pain. Direct palpation with pressure on the site of entrapment may also induce or exacerbate symptoms. Repeating the examination after a particular activity that exacerbates symptoms may produce findings not present on the initial examination at rest.
Styf described the use of three provocative tests for nerve compression at rest and again at rest after exercise in competitive athletes with symptoms suggestive of exertional compartment syndrome. [39] In the first test, pressure is applied over the anterior intermuscular septum while the patient actively dorsiflexes the ankle. In the second, the foot is passively plantarflexed and inverted at the ankle. In the third, while the patient maintains the passive stretch, gentle percussion is applied over the course of the nerve.
In some cases of superficial peroneal nerve entrapment associated with direct or indirect trauma, patients may present with symptoms of reflex sympathetic dystrophy (RSD), or complex regional pain syndrome (CRPS), which creates a diagnostic and therapeutic challenge.
Infrequently, weakness of the dorsiflexors and everters of the foot may be seen with associated foot drop in more proximal entrapments of the superficial peroneal nerve.
Occasionally, in cases of exertional compartment syndrome, measurement of the intramuscular pressure at rest after exercise may be helpful.
Injection of the nerve with lidocaine or bupivacaine just above the site of involvement can be the most valuable diagnostic tool. The patient can define the extent of relief obtained from such an injection, which can be helpful in defining the zone of injury and expected relief from surgical release or excision.
Deep peroneal nerve entrapment
With proximal entrapment of the deep peroneal nerve, motor dysfunction may be demonstrated on regular gait examination, with presentations such as a dramatic foot drop. However, symptoms are usually more subtle and are noted only on heel walk or a hop test.
With long-standing dysfunction, plantarflexion of the ankle with extension of the toes can compress the nerve as it passes beneath the extensor retinaculum, and this can exacerbate the symptoms. Muscular atrophy may also be noted in the anterior compartment of the extensor digitorum brevis with distal entrapment of the nerve.
With distal entrapment, tenderness may be elicited along the entrapped segment of the nerve over the anterior ankle or just distal to it, and an underlying bony prominence is usually present. Provocative dorsiflexion and plantarflexion of the ankle may bring on or increase symptoms. A sensory deficit in the first webspace may also be detectable. Most patients have a positive Tinel test result over the entrapment site, commonly around the fibular neck or over the anterior ankle.
Incomplete involvement can also occur, affecting isolated sensory or motor branches. Temporary resolution of neuritic symptoms following an injection of the nerve with plain lidocaine at the site of entrapment is a good indicator that the diagnosis is correct.
Interdigital neuritis
The Mulder click is a useful diagnostic test for interdigital neuritis. The forefoot is held in one hand, and the metatarsal heads are squeezed while the other hand places direct pressure on the plantar aspect of the interspace. As the metatarsal heads are compressed, the enlarged nerve is pushed plantar and away from the metatarsal heads, and a click is palpated with the digit in the plantar web space just distal to the transverse intermetatarsal ligament.
This test is often uncomfortable for the patients but does not usually reproduce their symptoms. The palpated mass can be pushed up again in the interspace with manual pressure while partial compression is maintained on the metatarsal heads. Many times, one digit is observed to move suddenly.
A range of conditions may mimic interdigital neuritis, including metatarsal stress fracture, MTP joint synovitis, intermetatarsal bursitis, extensor tendon tenosynovitis, tumor, and more proximal nerve injury. Metatarsal stress fracture will present with bony tenderness and pain upon palpation of the metatarsal shaft, rather than the common digital nerve. MTP joint synovitis will often prove painful during active or passive joint motion.
The diagnosis of interdigital neuritis is based primarily on clinical findings. Careful clinical examination usually will reveal other conditions that can mimic or coexist with intermetatarsal neuritis. In complex cases, immediate, temporary resolution in response to a local anesthetic block proximal to the involved area below the intermetatarsal ligament can confirm the diagnosis.
