Tarsal tunnel syndrome: clinical insights, vascular etiologies, and the role of ultrasonography in the diagnosis

Reis Soares, Ocacir de Souza; Duarte, Márcio Luís

doi:10.1590/0100-3984.2025.0053

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Pictorial Essay • Radiol Bras 58 • 2025 • https://doi.org/10.1590/0100-3984.2025.0053 linkcopy

Tarsal tunnel syndrome: clinical insights, vascular etiologies, and the role of ultrasonography in the diagnosis

Síndrome do túnel tarsal: impressões clínicas, etiologias vasculares e o papel da ultrassonografia no diagnóstico

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Tarsal tunnel syndrome results from compression or damage to the tibial nerve or its branches as they pass through the tarsal tunnel beneath the flexor retinaculum. Diagnosing tarsal tunnel syndrome is challenging because of nonspecific symptoms that overlap with those of other lower limb pathologies. Vascular disorders are common causes but are often overlooked. High-resolution ultrasonography has emerged as a valuable diagnostic tool, offering advantages over other imaging methods. This technique allows real-time assessment, identifying the factors that cause vascular compression and improving diagnostic accuracy. Increased awareness of the vascular contributions to tarsal tunnel syndrome can promote early diagnosis and improve treatment outcomes.

Keywords:
Ultrasonography; Tarsal tunnel syndrome; Tibial nerve; Vascular diseases

Vascular cause	Description	Key ultrasound findings
Plantar varicose veins	Dilated, tortuous plantar veins (> 5 mm diameter) associated with venous stasis	Dilated vein in direct contact with the tibial or plantar nerve; increased diameter when standing; Doppler showing slow flow or venous reflux
Tibial venous aneurysm	Focal dilatation of the tibial vein in direct contact with the tibial nerve	Fusiform or saccular anechoic area within the vein; turbulent flow on Doppler; clear compression of the adjacent nerve
Venous thrombosis	Intraluminal thrombus leading to venous dilatation and nerve compression	Non-collapsible vein with echogenic material; absence of intraluminal flow on Doppler; close anatomical relationship with the nerve
Tibial artery kinking	Tortuous or kinked tibial artery impinging on the nerve	Tortuous arterial course; pulsatile signal; direct contact with the tibial nerve; normal or altered flow direction on Doppler
Vascular malformation	Venous malformations (e.g., Klippel-Trénaunay syndrome) compressing the nerve within the tarsal tunnel	Dilated veins with anomalous channels; multiple venous pathways; direct contact with the nerve; enlargement when standing

Condition	Clinical features	Imaging findings	Key distinctions from vascular TTS
Plantar fasciitis	Localized heel pain, worse during first steps in the morning; no distal paresthesia	Ultrasound: thickened, hypoechoic plantar fascia; normal tibial nerve MRI: increased signal at insertion site	No nerve compression; symptoms localized to plantar fascia
Baxter's neuropathy	Burning heel pain, medial heel numbness, sometimes radiating to the lateral foot	Ultrasound: thickening or swelling of inferior calcaneal nerve; possible entrapment beneath abductor hallucis MRI: may show atrophy of abductor digiti minimi	More distal entrapment; affects inferior calcaneal nerve, not tibial nerve directly
Peripheral neuropathy	Bilateral, diffuse sensory loss; associated with systemic conditions (e.g., diabetes)	Ultrasound: no focal compressive site; possible diffuse nerve enlargement MRI: diffuse signal changes	Non-focal; lacks dynamic vascular compressive factor; often bilateral

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