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Posterior tibial vein thrombosis causing tarsal tunnel syndrome

Case contributed by Amit Lakkaraju
Diagnosis certain

Presentation

Acute onset medial ankle pain and numbness over the heel.

Patient Data

Age: 50 years
Gender: Female

There is medial ankle soft tissue edema centered on the posterior branch of the paired posterior tibial veins as it runs through the tarsal tunnel. There is a heterogenous high signal centrally within the lumen of the vein on PDFS sequences surrounded by a peripheral rim of low signal. The posterior tibial vein abuts the swollen posterior tibial nerve. The posterior tibial nerve is demonstrating internal high signal. On the coronal images, there is denervation edema signal seen in the quadratus plantae muscle (lateral plantar nerve innervation) and high signal in the inferior plantar nerve (Baxter's nerve).

Arrows indicating regions of interest.

Posterior tibial vein

ultrasound

Targeted ultrasound of the medial ankle confirms the diagnosis of posterior tibial vein thrombosis. The posterior branch of the duplicated posterior tibial vein from 2cm above the ankle joint to 3cm below the ankle joint is non-compressible and does not show any flow. The tibial nerve in the tarsal tunnel abuts the thrombosed vein.

Case Discussion

The posterior tibial vein is formed by the medial and lateral plantar veins. It is often a single vein but can be duplicated as seen in this case. The posterior tibial vein runs along with the posterior tibial artery and the posterior tibial nerve in the tarsal tunnel. It receive tributaries from the peroneal veins and the venous plexus in the calf muscles (especially from the venous plexus in the soles muscle) and from superficial veins. They join the anterior tibial veins to form the popliteal vein that enters the popliteal fossa.

In this case, the posterior branch of the duplicated posterior tibial vein is thrombosed as it runs through the tarsal tunnel producing a rare cause of tarsal tunnel syndrome and Baxter's neuropathy. There is secondary neuritis of the inferior plantar nerve (Baxter' nerve) and denervation edema in the quadratus plantae muscle (supplied by the lateral plantar nerve).

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