Iatrogenic axillary neuropathy after intramuscular injection of the deltoid muscle

A previously healthy 26-yr-old male presented for an electrodiagnostic evaluation with complaints of significant right deltoid muscle atrophy and shoulder abduction weakness after receiving an intramuscular (IM) deltoid injection of an antiemetic 4 wk earlier. Electrodiagnostic evaluation confirmed an acute axillary neuropathy. We hypothesize that direct mechanical trauma to the anterior branch of the axillary nerve resulted in axillary mononeuropathy with axonal loss, although chemically induced nerve injury cannot be excluded. Injections in and about the shoulder complex are performed routinely for the purposes of vaccination, IM medication administration, deltoid trigger-point injections, and intra-articular and bursal steroid injections. Although such injections are considered routine office procedures, there is increased risk of neurovascular injury if they are performed incorrectly. The purpose of this brief report is to make practitioners aware of the potential for axillary neuropathy with such procedures, to review the salient anatomy, and to propose a potential guideline for clinical practice to minimize iatrogenic axillary neuropathy.