Use of botulinum toxin type A in symptomatic accessory soleus muscle: first five cases

Symptomatic accessory soleus muscle (ASM) can cause exercise-induced leg pain due to local nerve/vascular compression, muscle spasm, or local compartment syndrome. As intramuscular injections of botulinum toxin type A (BTX-A) can reduce muscle tone and mass, we investigated whether local BTX-A injections relieve the pain associated with symptomatic ASM. We describe five patients presenting peri/retromalleolar exertional pain and a contractile muscle mass in the painful region. Com-pression neuropathy was ruled out by electromyo-graphic analysis of the lower limb muscles. Doppler ultrasonography was normal, excluding a local vascular compression. ASM was confirmed by magnetic resonance imaging. After a treadmill stress test, abnormal intramuscular pressure values in the ASM, confirmed the diagnosis of compartment syndrome only in one patient. All five patients received BTX-A injections in two points of the ASM. The treatment efficacy was evaluated based on the disappearance of exercise-induced pain and the resumption of normal physical and sports activities. After BTX-A injection, exertional pain disappeared and all five patients resumed their normal level of physical and sports performances. Neither side effects nor motor deficits were observed. BTX-A is well tolerated in patients with ASM and could be used as a new conservative therapeutic strategy for the treatment of symptomatic ASM before surgery.