Postmastectomy brachial plexus injury exacerbated by tissue expansion.

A neurapraxic injury to the brachial plexus was seen after modified radical mastectomy and immediate tissue expander placement. Neurological recovery proceeded until a sudden deterioration 42 hours after the fourth expansion. Deflation of the expander from an initial pressure of 18 mm Hg to 8 mm Hg led to relief from all acute symptoms, which were primarily in the distribution of the nerve most severely involved at the time of the initial injury, the median nerve. The history of previous neurapraxia and anatomical relationships between the tissue expander, pectoralis minor tendon, and neurovascular structures suggest that impairment of nerve function occurred through a compressive mechanism resembling a double-crush phenomenon.