Neurilemoma of the posterior tibial nerve and tarsal tunnel syndrome

Tarsal tunnel syndrome secondary to accessory or variant muscles: a clinical and anatomical systematic review

PURPOSE

Many etiologies are known to lead to a tarsal tunnel syndrome (TTS). One rare cause is mass-occupying lesions, and particularly accessory or variant muscles (AVM). This study aimed to systematically collect published clinical cases of TTS caused by AVM.

METHODS

An electronic literature search was conducted from inception to April 2021. The diagnosis of AVM should be reported in one of the following methods: ultrasonography, magnetic resonance imaging (MRI), or per-operatively. Data extraction included types and prevalence of accessory muscles, clinical presentation and diagnosis, and treatment modalities. Twenty-five studies were identified with a total 39 patients (47 ankles).

RESULTS

The prevalence of TTS was reported in only two studies (9%). Forty-nine AVM were identified with the accessory flexor digitorum longus being the most common (52%). The most common sign/symptoms were tenderness (78.7%), pain (82.9%), dysesthesia (57.4%), Tinel sign (44.6%), and a swelling (25.5%). Decompression and excision were the most commonly performed procedures. Four accessory/variant muscles in the ankle have the potential to induce a tarsal tunnel syndrome.

CONCLUSION

This review highlights the clinical and imagery specificities of TTS secondary to accessory or variant muscles. Mass-occupying etiology should be included in the list of differential diagnoses whenever a posterior tibial nerve compression is suspected.

Atypical musculoskeletal manifestations on flexor hallucis longus tendon of gout causing tarsal tunnel syndrome in diabetic patients: A case report

RATIONALE

Deposition of tophus is a common feature in chronic gout; however, signs and symptoms are not always well-pronounced in cases of uncommon sites. We report a rare case with a tophaceous tendonitis on the flexor hallucis longus (FHL) tendon with tarsal tunnel syndrome (TTS). This is the first surgical case of TTS by gouty tophi in FHL.

PATIENT CONCERNS

A 55-year-old woman presented with a 6-month history of mild discomfort at the right foot, which gradually worsened in the past 3 weeks. The patient visited our outpatient clinic due to persistent and aggravating foot pain and swelling around the tarsal tunnel.

DIAGNOSIS

The patient was diagnosed with hyperuricemia and diabetes mellitus with chronic kidney disease, and did not receive regular antigout treatments. Paresthesia was found along the distribution of medial and plantar nerve and tinel test was positive on tarsal tunnel. Biochemical examination showed she had raised serum uric acid (10.6 mg/dL) and decreased estimated glomerular filtration rate (69 mL/min/1.73 m). Conventional radiography examination showed negative pathology except soft tissue swelling. Magnetic resonance imaging revealed a fusiform mass within the FHL tendon and fluid collection around tarsal tunnel.

INTERVENTIONS

Surgical exploration was performed to remove the mass. Inflammation fluid exploded out from FHL tendon sheath, which was later proven to have infiltration of monosodium urate crystal. Superficial dissection revealed a white chalky mass and posterior tibial nerve was significantly compressed by the tophus mass.

OUTCOMES

The mass was removed and the symptoms were relieved at immediate postoperative period.

LESSONS

A tophaceous tendonitis on FHL tendon can cause TTS and surgical decompression of the gout lesion can reduce the symptoms.

3T magnetic resonance neurography of tibial nerve pathologies

Diagnosis of tibial neuropathy has been traditionally based on clinical examination and electrodiagnostic studies; however, cross-sectional imaging modalities have been used to increase the diagnostic accuracy and provide anatomic mapping of the abnormalities. In this context, magnetic resonance neurography (MRN) offers high-resolution imaging of the tibial nerve (TN), its branches and the adjacent soft tissues, and provides an objective assessment of the neuromuscular anatomy, abnormality, and the surrounding pathology. This review describes the pathologies affecting the TN and illustrates their respective 3 Tesla (T) MRN appearances with relevant case examples.

Tarsal tunnel syndrome and flexor hallucis longus tendon hypertrophy

Tarsal tunnel syndrome (TTS) defines an entrapment neuropathy of the posterior tibial nerve or one of its branches, within the tarsal tunnel. Numerous etiologies have been described explaining this entrapment, including trauma, space-occupying lesions, foot deformities, etc. We present an unreported cause of a space-occupying lesion in the etiology of TTS, namely the combination of a hypertrophic long distally extended muscle belly of the flexor hallucis longus and repetitive ankle motion. Surgical debulking of the muscle belly in the posterior ankle compartment resolved all symptoms.

Tarsal tunnel syndrome associated with a neurilemoma in posterior tibial nerve: a case report

Compression neuropathy of the posterior tibial nerve (PTN) and its branches in the tarsal tunnel is called tarsal tunnel syndrome (TTS) and has various aetiologies. Space-occupying lesions in the tunnel, such as neurilemomas, can cause such a disease. When a neurilemoma occupies the tarsal tunnel, it can compress the PTN directly or indirectly and results in restriction of the tunnel volume. Symptoms due to this restricted volume may vary in TTS. A case of neurilemoma of PTN in tarsal tunnel with a complaint of posteromedial ankle intermittent pain in a 20-year-old patient is presented here. A mass was observed at the ankle posteromedially during clinical examinations and the patient underwent magnetic resonance imaging (MRI) and radiological investigation. Radiographic evaluation of the ankle was normal. However, MRI was revealed a mass adjacent to the PTN in the tarsal tunnel. An ovoid, smooth-surfaced, encapsulated and eccentrically localized mass in the PTN was detected at surgery. The mass was excised from the nerve and pathological evaluation revealed a neurilemoma (schwannoma). Neurilemomas arising from the PTN in the tarsal tunnel should always be kept in mind as a differential diagnosis when a patient complains of a posteromedial ankle pain. Since it is a space-occupying lesion and encapsulated tumor in the tarsal tunnel, simple surgical resection is curative without a distinct morbidity.