Hypoglossal Nerve Palsy Due to Synovial Cyst: A Systematic Review and Illustrative Case

Introduction: Synovial cysts are benign soft-tissue masses that are rarely located in the occipitocervical junction and surrounding anatomical location. They may lead to compression of the hypoglossal nerve. Typically, cysts in this region remain asymptomatic, and biopsies of the hypoglossal canal have high risks, so imaging is a very important diagnostic tool.

Methods: A systematic search of PubMed, Medline, Embase, Scopus, and Web of Science was conducted in line with PRISMA guidelines to identify studies on patients with hypoglossal nerve palsy due to synovial cysts. The search strategy followed the authors' predefined PROSPERO protocol. (CRD42024577602)

Results: Data were reviewed from 35 patients with hypoglossal nerve palsy due to synovial cysts across 18 studies from 1974 to 2024. (Table 1) There were 14 (40.0%) males and 21 (60.0%) females. The median (range) patient age was 69.0 (20-89) years. In terms of presenting symptoms, 29 (82.86%) exhibited unilateral tongue atrophy or deviation. Additionally, 11 patients (31.43%) reported swallowing difficulties or dysphagia, and 23 patients (62.86%) experienced slurred speech or dysarthria.

Conclusion : Synovial cysts within the hypoglossal canal are benign lesions that typically appear as T1 hypointense or isointense and T2 hyperintense with peripheral enhancement on magnetic resonance imaging (MRI).