A 42-year-old male with no comorbidities presented with complaints of pain on the medial aspect of the left ankle, cramps on the left leg during the night and numbness of the left first to third toes for 4 weeks.
On clinical examination, he had normal power of intrinsic foot muscles with normal sensation. Tinel’s sign was positive in the left tarsal tunnel region along with tenderness.
MRI of the left ankle shows a lobulated mass along the medial aspect of the calcaneus (arrow), demonstrating fluid signal intensity on fat-suppressed T2-weighted sagittal (Figure 1a) and coronal (Figure 1b) images and T2-weighted sagittal image (Figure 1d). The mass demonstrated an iso to hypointense signal intensity to skeletal muscle on T1-weighted images (Figure 1c) along the medial aspect of the calcaneum posterior to the flexor digitorum longus tendon.
Ultrasound of the left ankle shows a lobulated cystic lesion behind the medial malleolus (Figure 2).
Background
The tarsal tunnel is a fibro-osseous channel extending from the ankle to the midfoot, through which the medial tendons and the posterior tibial neurovascular bundle pass. Tarsal tunnel syndrome (TTS) is a compression neuropathy of the posterior tibial nerve or one of its branches and may be caused by a variety of pathologic lesions [1].
The aetiology can be intrinsic or extrinsic:
Clinical Perspective
Symptoms include sole numbness, pain, and a cold sensation; they affect the patient’s quality of life [2]. TTS can present similarly to other lower extremity conditions, with the most common differential diagnosis being plantar fasciitis, as these patients also present with plantar heel pain. In addition to plantar fasciitis (in which TTS is thought to be commonly misdiagnosed), polyneuropathy, L5 and S1 nerve root syndromes, Morton’s metatarsalgia, compartment syndrome of the deep flexor compartment will have to be distinguished from tarsal tunnel syndrome as well [4].
Imaging Perspective
Imaging, in particular MRI, can help identify causative factors in individuals with suspected TTS and help aid surgical management. The detection of a space-occupying lesion is important, as surgery is advised.
Outcome
Treatment of tarsal tunnel syndrome is initially conservative and includes behavioural modification, physical therapy, immobilisation, and anti-inflammatory medication. Surgical release of the flexor retinaculum and removal of the offending mechanism is attempted in refractory cases or in cases with mass effect, but results vary depending on the aetiology, duration of symptoms, and the age of the patient. The longer the duration of symptoms and the older the patient, the worse the prognosis.
Take Home Message / Teaching Points
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Ganglion cyst causing tarsal tunnel syndrome
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Based on the provided MRI images, there is an irregular cystic or cyst-like high-signal lesion located near the medial malleolus of the left foot (in the tarsal tunnel region where the posterior tibial nerve runs). Surrounding tissue structures are locally compressed. This cystic structure is adjacent to the flexor retinaculum and surrounding soft tissues, and the signal characteristics suggest a fluid component. Mild soft tissue edema or inflammatory signs are visible in the surrounding area, but there is no obvious abnormality in the local bone.
Considering the patient’s symptoms (medial malleolus pain, toe numbness, nighttime cramping), clinical examination findings (positive Tinel’s sign), and imaging findings (cystic lesion in the tarsal tunnel region likely compressing the posterior tibial nerve), along with no significant history of other systemic diseases, the most likely diagnosis is: Tarsal Tunnel Syndrome of the Left Foot (potentially caused by a cystic lesion such as a ganglion cyst).
If conservative treatments fail or MRI confirms a significant space-occupying lesion (e.g., cystic or tumorous mass) causing prolonged nerve compression, surgical decompression and/or excision of the cyst may be considered. Surgical outcomes depend on factors such as the patient’s age, duration of symptoms, and the specific etiology.
Rehabilitation should be conducted progressively, following the FITT-VP principle:
Notes: If the patient experiences significantly increased pain, foot swelling, or marked discomfort at night, seek medical attention or adjust the training regimen promptly.
Disclaimer: This report serves as a reference analysis and does not substitute for an in-person consultation or professional physician’s advice. If you have any questions, please consult your clinical doctor promptly.
Ganglion cyst causing tarsal tunnel syndrome
