Vocal Cord Palsy in Hypoxic Brain Injury: A Qualitative Systematic Review

This study aimed to consolidate evidence linking vocal cord palsy (VCP) to hypoxic injury, and its pathophysiology, and explore related topographical representations along laryngeal innervation. PubMed, Embase, and Scopus were the databases used. This review adheres to PRISMA guidelines. We included case series or case reports published before December 6, 2023. These studies must document VCP, diagnosed via direct or indirect laryngoscopic evaluation, resulting from hypoxic injury with imaging documentation specifying the level of injury. Screening, review, quality assessment, and extraction were done using Covidence. Our search strategy yielded 380 articles, of which 11 papers met the inclusion criteria for final review. A total of 12 patients were included across the selected studies, evenly split between genders. The causes of hypoxic injury were stroke in 11 cases and perinatal asphyxia in one. The hypoxic injury affected the medulla, pons, basal ganglia, thalamus, internal capsule, cortex, and cerebellum. The distribution of hypoxic injuries was: left side (6), bilateral (2), right side (2), and not mentioned (2). Vocal cord involvement was unilateral in eight cases and bilateral in four cases. In five cases, the involvement was ipsilateral to the hypoxic injury, bilateral when the injury was bilateral, and contralateral in two cases. Our study provides insights into how hypoxic brain injury can cause VCP and correlates the level of lesions along the innervation pathway with the clinical presentation. VCP can be induced by hypoxic injuries to the neurons extending from the laryngeal motor cortex to the laryngeal motor neurons in the medulla.