Functional popliteal artery entrapment syndrome (FPAES) is an uncommon cause of exercise-induced leg pain. Artery compression is mostly due to hypertrophic gastrocnemius muscles (GCM) without any anatomic abnormality. Surgical arteriolysis of popliteal artery is often proposed, sometimes with myotomy. But long-term efficacy of surgery is unknown. As botulinum toxin A (BoNT-A) injections can induce localised and partial muscular atrophy and hypotonia, we supposed that BoNT-A injections in GCM could relieve pain associated with FPAES.

We describe five patients with a FPAES treated with BoNT-A and followed more than one year. Diagnostic was confirmed by provocative tests in plantar or dorsal flexion of the ankle on vascular imagery (doppler ultrasonography, computed tomography or magnetic resonance angiography). Other causes of leg pain were excluded, such as chronic exertional compartment syndrome with compartment pressure after exercise. BoNT-A was injected under electromyograph guidance in the proximal third of both heads of GCM (two sites/head), with 25 to 37.5 U of Incobotulinum toxin A or 100 to 160 US of Abobotulinum toxin A.

Exercise-induced leg pain completely disappeared after treatement for all patients and they resumed their normal level of sports or physical professional activities. One patient was treated twice, eight months after the first injections, since he relapsed. There were no muscular weakness but the patient treated with the highest dose had transient asthenia and mictional disorders. Four patients are currently still asymptomatic, with a follow up between 14 and 28 months. One patient relapsed late after 50 months.

BoNT-A injections could be used as a new conservative therapeutic strategy in FPAES and could reduce functional compression by improving artery-GCM impingement. This study is the first to demonstrate that BoNT-A could induce long-lasting resolution of symptoms, more than one year as previoulsy described (Hislop, 2017). It is well tolerated if the dose is well choosed.