Tarsal tunnel syndrome is defined as entrapment of the tibial nerve or branches of the nerve within or distal to the tarsal tunnel of the medial ankle.1 This is an extremely rare diagnosis and can reasonably be thought of as a pain syndrome.
Common etiologies for tarsal tunnel syndrome include acute trauma, such as sprains, strains, or fractures. Other causes include mass lesions from venous varicosities, cysts, lipomas, tendon sheath ganglia, bony exostoses, or tumors.2,3 Inflammatory arthropathies may also cause tarsal tunnel syndrome.2,3 In many cases the etiology is ultimately unknown.3,4 Compared with carpal tunnel syndrome, chronic repetitive injury is believed to be a rare etiology.5
Neuropathic lesions of other intrinsic nerves of the foot are caused by similar etiologies. In cases involving the deep peroneal nerve and medial and intermediate dorsal cutaneous nerves, tight fitting shoes have been implicated.4,5
Epidemiology including risk factors and primary prevention
Tarsal tunnel syndrome is a rare disease defined by the Office of Rare Diseases Research of the National Institutes of Health as having a prevalence of less than 1 in 200,000.
The tibial nerve descends posterior and inferior to the medial malleolus. As it descends distal to the medial malleolus it runs through the tarsal tunnel. The tunnel is a fibrosseous structure called the flexor retinaculum that makes up the roof, and a bony floor. After exiting, the tibial nerve divides into the medial calcaneal nerve, medial plantar nerve, and lateral plantar nerve. The medial plantar nerve provides sensation to the medial plantar foot, distal dorsal three and a half toes, motor to abductor hallucis brevis, flexor hallucis brevis, and flexor digitorum brevis. The most likely site of compression is the decussation of the flexor digitorum longus and flexor hallucis longus.6
The lateral plantar nerve supplies sensation to the lateral plantar foot, distal dorsal one and a half toes, and motor to abductor digiti quinti pedis. It is most likely compressed between the abductor hallucis longus and quadratus planus.7 The medial calcaneal nerve only supplies sensory to the plantar heel. The deep peroneal nerve travels deep to the extensor retinaculum of the foot. It provides sensory to the web space between the first and second digits, motor to extensor digitorum brevis, and extensor hallucis brevis. The superficial peroneal nerve divides into medial and intermediate dorsal cutaneous nerves in the lower third of the leg. It travels superficial to the extensor retinaculum. These nerves provide sensory to the remaining dorsum of the foot and toes with the exception of the fifth toe.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
Symptoms are often vague and nonspecific. The patient may complain of numbness, tingling, or burning of the plantar foot and distal toes or in the perimalleolar area.1-3,5 As the condition progresses, patients may complain of pain that awakens them at night or more proximal pain in their calf.1,3 Intrinsic foot muscle atrophy may rarely be seen in chronic and severe cases.1,3 Medial plantar and lateral plantar neuropathy present similarly with intermittent foot pain along with numbness and tingling that is worse with activity.4,7 Neuropathy of the deep peroneal, medial, and intermediate dorsal cutaneous nerves presents with symptoms of pain over the dorsal foot, numbness, and paresthesias.4,5 Calcaneal neuropathy presents with heel pain and numbness.
2. ESSENTIALS OF ASSESSMENT
Because symptoms are vague and nonspecific, the differential diagnosis is, therefore, broad. Peripheral neuropathies and musculoskeletal injuries are high on the differential and should be considered first and extensively evaluated and treated before reaching a diagnosis of tarsal tunnel syndrome.
It is important to evaluate for a radiculopathy or radiculitis, particularly in the L5 or S1 distribution. Similarly, peroneal neuropathy at the fibular head should be considered.
The patient should be asked about recent or remote trauma including sprains, strains, and fractures. Systemic diseases, such as diabetes mellitus, thyroid conditions, lupus, and inflammatory arthropathies, should be screened for.
Vascular disease should be considered because vascular claudication can present with numbness and tingling.
Consider medications that are associated with peripheral neuropathy and a history of alcoholism in the initial history.
A family history of foot deformities, such as pes planus, pes cavus, valgus or varus hindfoot, and hammer toes, should be asked about.
It is essential to perform a general examination of the back and peripheral nervous system, including manual muscle testing, reflexes, sensation, and maneuvers to elucidate radiculopathy and musculoskeletal pain. A sensory exam determines the breadth of the involved areas. It is difficult to isolate the intrinsic muscle of the foot for manual muscle testing; therefore, weakness may be masked.1,3 Muscles should be inspected, however, for atrophy.
Part of the exam should include the patient standing because varicosities may be more apparent.4 A Tinel sign should be performed; it is present in most cases of tarsal tunnel syndrome.3
A valgus hindfoot and a positive Tinel sign just posterior to the navicular tuberosity can suggest medial plantar neuropathy. Pain with ankle eversion and pain exacerbated when foot is plantarflexed are also features seen on physical exam.
Shoes should be inspected, particularly when considering anterior tarsal tunnel syndrome, an entrapment of the deep peroneal nerve under the extensor retinaculum of the ankle, or medial and intermediate dorsal cutaneous neuropathy.
For symptoms of foot pain, numbness, or weakness, gait should be assessed. Pes planus, pes cavus, and valgus or varus hindfoot are thought to be associated with tarsal tunnel syndrome, and an orthotic can be used to correct alignment.3,4 Other biomechanical derangements in knee, hip, or spine should be assessed because they may contribute to symptoms of foot pain.
Serology for inflammation, erythrocyte sedimentation rate, and C-reactive protein can be ordered. In addition, complete blood count, urinalysis, blood urea nitrogen, creatinine, hemoglobin A1C, human immunodeficiency virus testing, B12, rapid plasma reagin, and Venereal Disease Research Laboratory can be ordered to consider contributing causes or mimics.
Anterior-posterior and lateral radiographs can rule out fractures and assess foot alignment. Magnetic resonance imaging and ultrasound can assess for a cyst or mass lesion. Ultrasound can localize nerve compression and dynamically assess the foot.
Supplemental assessment tools
Electrodiagnostic testing is an important tool in the evalutation of suspected tarsal tunnel syndrome or mimicking conditions. Bilateral distal tibial motor to abductor hallucis brevis for medial plantar nerve conduction, and abductor digiti quinti pedis for lateral plantar nerve conduction should be assessed. Latencies may be prolonged or amplitudes reduced on the affected side. In addition, tibial and peroneal motor, sural sensory, tibial and peroneal F waves, and an H reflex can be done to help localize the lesion and exlude other lesions. Sensory and mixed nerve studies for lateral and medial plantar nerves may increase the sensitivity for diagnosis.3,5
Needle electrode examination should be performed on several muscles in the affected limb including the abductor hallucis, abductor digiti quinti pedis, and other muscles in order to exclude a radiculopathy or other peripheral nerve lesions that may mimic TTS
Early predictions of outcomes
Predictors of poor outcomes include symptoms greater than 1 year, old age, motor deficits, nerve scarring, and idiopathic causes.8-11 Surgical outcomes are more likely to be successful if there is a mass lesion.8
Wong-Baker FACES Pain Rating Scale may be useful in predicting outcome for tarsal tunnel syndrome. Patients who improved with nonoperative treatment had improved pain scores when after treatment scorese were compared to pre-treatment scores. Patients requiring surgery improved in the medial calcaneal and medial plantar regions only.12
In general, healthy eating habits, weight loss, and activity modifications may be necessary to help patients with foot pain. In patients with anterior tarsal tunnel syndrome, tight fitting shoes should be avoided. In runners with lateral or medial plantar neuropathy, a decrease in running may be necessary.
Social role and social support system
Social support systems should be discussed with the patient. Social support groups are available for obesity, alcoholism, and chronic conditions, such as inflammatory arthritis.
Vocational training or professional modifications may need to be considered. Manual laborers are thought to have worse outcomes with tarsal tunnel syndrome.8,10
3. REHABILITATION MANAGEMENT AND TREATMENTS
At different disease stages
Treatment of tarsal tunnel syndrome or any intrinsic foot neuropathy should begin with noninvasive strategies. Because obesity may predispose patients to tarsal tunnel syndrome, weight loss should be emphasized.2 Orthotics to correct alignment or to relieve pressure is an option if there is suspicion that this is contributing to symptoms.3,4 Physical therapy may help correct muscle imbalances that may be contributing. Anti-inflammatory medications or steroid injections may provide relief.4
Specific etiologies for tarsal tunnel syndrome or any intrinsic foot neuropathy should be treated, such as varicose vein management, ganglion cyst aspiration, or tumor.
Tarsal tunnel syndrome is often resistant to conservative measures, and surgical release can become necessary for relief.4
With surgery, the goal is to relieve nerve compression. Surgery can remove cysts, bone spurs, and compression caused by the tarsal tunnel. Surgical release has mixed success rates ranging from 44% to 90%.2,4
Coordination of care
Team members include a physiatrist, physical therapist, orthotist, interventionalist for injections, podiatrist, and a surgeon.
Patient & family education
Patient education on their disease and contributing factors can empower them to avoid exacerbating symptoms. Use of proper fitting shoes and orthotics should be taught. Patients should be encouraged to manage contributing conditions, such as diabetes. In general, weight loss is encouraged and alcohol intake is discouraged.
As previously mentioned, the Wong-Baker FACES Pain Rating Scale scores are beneficial in predicting outcomes.8 On follow-up after treatment, patients should be asked about improved pain, sleeping, walking distance, and overall function for outcomes measures. There may be a role for repeat electrodiagnostics if there is no improvement or symptoms worsen.
Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
- Tarsal tunnel syndrome is rare and the diagnosis should be made on only rare occasions and with much less confidence as other entrapment neuropathies such as carpal tunnel syndrome. Rule out more common conditions, such as systemic distal polyneuropathy or common musculoskeletal complaints, such as a sprain or strain.
- If electrodiagnostic testing revealss abnormalities in the distribution of the tibial nerves bilaterally, polyneuropathy should be considered as a diagnosis of bilateral tarsal tunnel syndrome is exceedingly rare.
- When diagnosing tarsal tunnel syndrome, consider underlying causes, such as mass lesions, inflammatory arthritis, diabetes, or human immunodeficiency virus.
4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
Using ultrasonagraphy in the diagnosis of nerve disorders is increasingly common. IN the case of a rare diaganosis such as tarsal tunnel syndrome, additional clnical information can be benificial. There is some evidenced in the liturature that ultrasonagraphy of the tibial nerve can show abnormalistis in the setting of tarsal tunnel syndrome.13 Sonographic criteria for idiopathic tarsal tunnel syndrome have also been outlined.14
5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE
Gaps in the evidence-based knowledge
- Epidemiology of tarsal tunnel syndrome is not well known.
- There are no recommended treatment guidelines for tarsal tunnel syndrome.
- Electrodiagnostic studies are level C recommendations for confirming the diagnosis of tarsal tunnel syndrome.15
- DeLisa JA, Saeed, MA. The tarsal tunnel syndrome. Muscle Nerve. 1983;6:664-670.
- Cimino WR. Tarsal tunnel syndrome: review of the literature. Foot Ankle. 1990;11:47-52.
- Oh SJ, Meyer RD. Entrapment neuropathies of the tibial (posterior tibial) nerve. Neurol Clin. 1999;17:593-615.
- Williams TH, Robinson AH. Entrapment neuropathies of the foot and ankle. Orthop Trauma. 2009;23:404-411.
- Preston DC, Shapiro BE. Tarsal tunnel syndrome. In: Preston DC, Shapiro BE, eds. Electromyography and Neuormuscular Disorders. 2nd ed. Elsevier; 2005:365-372.
- Oh SJ, Lee KW. Medial plantar neuropathy. Neurology. 1987;37:1408-1410.
- Baxter D, Pfeffer G. Treatment of chronic heel pain by surgical release of the first branch of the lateral plantar nerve. Clin Orthop. 1992;279:229-236.
- Antoniadis G, Scheglmann K. Posterior tarsal tunnel syndrome: diagnosis and treatment. Dtsch Arztebl Int. 2008;105:776-781.
- Sammarco GJ, Chang LJ. Outcome of surgical treatment of tarsal tunnel syndrome. Foot Ankle Int. 2003;24:125-131.
- Lau J, Daniels T. The effects of tarsal tunnel release and stabilization procedures on tibial nerve tension in a surgically created pes planus foot. Foot Ankle Int. 1998;19:770-777.
- Ballie DS, Kelinkian AS. Tarsal tunnel syndrome: diagnosis, surgical technique, and functional outcome. Foot Ankle Int. 1998;19:65-72.
- Gondring WH, Trepman E, Shields B. Tarsal tunnel syndrome: assessment of treatment outcomes with an anatomic pain intensity scale. Foot Ankle Surge. 2009;15:133-138.
- Samarawickrama D, Therimadasamy AK, Chan YC, Vijayan J, Wilder-Smith EP. Nerve ultrasound in electrophysiologically verified tarsal tunnel syndrome. Muscle Nerve. 2016 Jun;53(6):906-12.
- Tawfik EA, El Zohiery AK, Abouelela AA. Proposed Sonographic Criteria for the Diagnosis of Idiopathic Tarsal Tunnel Syndrome. Arch Phys Med Rehabil. 2016 Jul;97(7):1093-9.
- Patel AT, Gaines K, Malamut R, et al. Usefulness of electrodiagnostic techniques in the evaluation of suspected tarsal tunnel syndrome: an evidence-based review. Muscle Nerve. 2005;32:236-240.
Original Version of the Topic:
Michael K. Mallow, MD. Tarsal tunnel syndrome and intrinsic neurologic foot disorders. 10/30/2013.
Michael K. Mallow, MD
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