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

Objectives 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. 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) and/or MRI) received 100 IU BTX into the medial head of the gastrocnemius and plantar muscles using ultrasound. Primary endpoint was patient-reported therapeutic effect 6 weeks after injection. Secondary endpoints were changes in treadmill testing and DUS 6 weeks after injection and number of patients free of symptoms or from surgery at one 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: 150 meter, median, IQR 78-258 m, after: 205 meter, median, IQR 120-299m, p=0.25). Popliteal artery DUS detected occlusion rates during provocation decreased from 31% to 3% (p=0.004). 60% reported fewer symptoms (40% some improvement, 20% much or fully recovered). Half of patients were satisfied. Conclusions Botulinum toxin A injections for fPAES are safe and patient friendly. Six weeks after injection, approximately half of patients report fewer symptoms and are satisfied. Long-term follow-up is needed before widespread implementation is recommended.