Short-term analysis of botulinum toxin A for functional popliteal artery entrapment syndrome.

[OBJECTIVE] Functional popliteal artery entrapment syndrome (fPAES) is characterized by exertional leg pain caused by hypertrophic musculature in young adults. If history, examination and imaging suggest fPAES, treatment is surgical including removal of plantaris and part of medial gastrocnemius muscle. Intramuscular botulinum toxin type A (BTX) injections are a less invasive alternative, but the therapeutic evidence is low. The aim of this prospective study was to determine the short-term clinical effects of BTX.

[METHODS] In this prospective single-center cohort study, young patients with a history suggestive of fPAES (calf pain within 5-10 minutes after starting exercise, disappearance 5-10 minutes after exercise cessation) and suggestive imaging (occluding or stenotic popliteal artery on duplex ultrasound [DUS] examination and/or magnetic resonance imaging) received 100 IU BTX into the medial head of the gastrocnemius and plantar muscles using ultrasound guidance. The primary end point was patient-reported therapeutic effect 6 weeks after injection. Secondary end points were changes in treadmill testing and DUS 6 weeks after injection and number of patients free of symptoms or from surgery at 1 year of follow-up.

[RESULTS] Between December 2022 and November 2024, 32 patients (50% male; median age, 21 years) were studied. Injections were well-tolerated without side effects. At 6 weeks, lower leg pain during daily life was significantly attenuated, but was unchanged during exercise. Change in pain free walking distance during a treadmill test was not significant (before: median, 150 m; interquartile range, 78-258 m; after: median, 205 m; interquartile range, 120-299 m; = .25). Popliteal artery DUS examination detected occlusion rates during provocation decreased from 31% to 3% ( = .004). Sixty percent reported fewer symptoms (40% some improvement, 20% much or fully recovered). One-half of the patients were satisfied.

[CONCLUSIONS] Botulinum toxin A injections for fPAES are safe and patient friendly. Six weeks after injection, approximately one-half of the patients report fewer symptoms and are satisfied. Long-term follow-up is needed before widespread implementation can be recommended.