Brachial plexus mucormycosis secondary to perineurial spread: Literature review and case report of a rare mode of infectious spread

Background: Mucormycosis is a rare fungal infection with nervous system involvement occurring through contiguous spread and/or angioinvasion after rhino-orbital and paranasal infection. Few cases report perineurial trigeminal mucormycosis spread with no cases reporting peripheral perineurial spread to the brachial plexus. Here, we detail such a case with rapid, progressive spread from a distal-arm cutaneous lesion, along the radial nerve proximally to the brachial plexus. Case: A 66-year old female presented to a peripheral hospital with a gangrenous forearm after falling 6-weeks prior resulting in a forearm abrasion. She was treated initially with antibiotics and outpatient wound care management, however re-presented with extensive forearm necrosis requiring an above-elbow amputation. She was transferred to our institution for further infectious disease management and investigation upon mucormycosis diagnosis (Rhizopus oryzae growth). Magnetic resonance imaging was completed showing perineurial invasion into the brachial plexus and spinal nerve roots. The patient underwent shoulder disarticulation and brachial plexus debridement for source control of the infection with pathologically confirmed perineurial fungal invasion. Despite aggressive surgical debridement and antifungal therapy, the patient died due to subsequent pulmonary fungal dissemination. Conclusion: Mucormycosis is a rare, but well recognized fungal infection typically spreading by direct tissue invasion or hematogenously after angioinvasion. Few case reports highlight perineurial Mucor spreading and none detail dissemination along peripheral nerves as seen here. In light of the high morbidity and mortality of these infections, the importance of timely diagnosis and thorough imaging investigations including MR neurography is emphasized.