An unusual case of aneurysmal tibial nerve compression detected in ED

We present an unusual case of tibial nerve compression caused by a true tibial posterior artery aneurysm. A 61-year-old man was admitted to the emergency department due to suspected muscle rupture. He had experienced a sudden, intense right calf pain and swelling that had begun during walking. He had a 6-month-long history of symptoms suggestive to the tibial nerve dysfunction and a month-long history of neurologic finding consistent with the right tibial nerve paresis. An examination of the legs revealed a painful mass in the posterior-medial compartment of the right calf. Emergency ultrasound scanning of the right lower leg vascularization showed an expansive saccular aneurysm of the proximal segment posterior tibial artery with mural thrombus and splitting of the aneurysmal wall. An angiography confirmed the diagnosis. Under spinal anesthesia, we performed aneurysmectomy and decompressed the tibial nerve. The histologic examination was compatible with a true aneurysm of the right posterior tibial artery.