Complex regional pain syndrome type II caused by iatrogenic lateral dorsal cutaneous nerve injury A case report

Rationale: Complex regional pain syndrome (CRPS) is a painful condition classified as type I or II depending on the absence or presence of nerve injury, respectively. Injury to the lateral dorsal cutaneous nerve (LDCN), a branch of the sural nerve, is a rare occurrence observed after a sprain or procedures conducted on the lateral side of the ankle. Patient concerns: A 38-year-old female, who had undergone prolotherapy for a sprain in the lateral side of the left ankle 3 months ago, presented with persistent causalgia and dysesthesia around the injection site. Diagnosis: An electrodiagnostic study was conducted, which confirmed that the patient had peripheral neuropathy of the left LDCN. Considering the digital infrared thermal imaging and three-phase bone scan findings and the clinical presentation, the condition was diagnosed as CRPS type II due to iatrogenic LDCN injury according to the Budapest diagnostic criteria for CRPS. Interventions: The patient was treated with steroid pulse therapy, physical therapy, and transcutaneous electrical nerve stimulation, as well as nonsteroidal anti-inflammatory drugs, pregabalin, and tricyclic antidepressants. Outcomes: After 1 month of treatment, allodynia of the left foot persisted, but the pain reduced from 6 points to 3 points on the numeric rating scale. Partial recovery of amplitude and conduction velocity was confirmed in the follow-up electrodiagnostic study. Lessons: LDCN injury should be considered in patients who complain of persistent lateral ankle and foot paresthesia or pain after sprain or procedures performed on the lateral side of the ankle. Early diagnosis and treatment can lead to a good prognosis when the LDCN injury has progressed to CRPS.