Poster 211: Injection of Botulinum Toxin as a Treatment for Superficial Peroneal Nerve Entrapment Caused by Muscle Hernia: A Case Report

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      Setting: Foot clinic of university hospital. Patient: A 79-year-old woman with pain in the lower leg and dorsum of the foot. Case Description: The patient presented with insidious onset of pain radiating from the anterodistal lower leg to the dorsum of right foot for the past 5 weeks. Pain was exacerbated with activities and relieved by rest. Her medical history included noninsulin-dependent diabetes mellitus for the past 22 years. Physical examination revealed a tender bulge of soft tissue 8cm above the lateral malleolus. Sensation to light touch was reduced on the distal anterolateral aspect of the lower leg and dorsum of the foot sparing the first web space. Her Tinel sign was positive when tapping over the soft tissue bulge, reproducing the symptoms. Remaining neurologic examination was not significant. Ultrasonographic evaluation of the lower leg showed herniation of peroneal muscle and exiting superficial peroneal nerve through fascial defect. Electromyography confirmed the soft tissue bulge as being the skeletal muscle. Assessment/Results: The patient was diagnosed with entrapment of superficial peroneal nerve secondary to muscle herniation. Diagnostic injection of lidocaine under ultrasonographic guidance near the superficial peroneal nerve alleviated the symptoms completely. She returned to the clinic 2 weeks later with complaint of residual pain and tenderness. 20U of botulinum toxin (Botox) were injected into the herniated muscle under ultrasonographic and electromyographic guidance. 1 week after the injection, the patient reported complete resolution of her symptoms. Discussion: Entrapment of superficial peroneal nerve due to muscle herniation through fascial defect of the lateral compartment has been previously described. This is, however, the first report of treating this condition with botulinum toxin. Conclusions: In this case, investigators showed that botulinum toxin can be utilized in the treatment of entrapment of the superficial peroneal nerve due to muscle herniation under the guidance of ultrasonography and electromyography.