Background: Isolated hypoglossal nerve palsy caused by an atlantooccipital synovial cyst is a rare lesion, with fewer than 5 cases reported in the literature.
Case description: Our patient presented with acute hypoglossal nerve dysfunction. Our differential included neoplasm, trauma, stroke, multiple sclerosis, or other inflammatory/infectious etiology. Imaging revealed a peripherally enhancing, extradural focus in the left premedullary cistern, most likely consistent with a synovial cyst.
Conclusions: A left suboccipital craniectomy was performed in the region of the left hypoglossal canal, in which a cystic structure was noted at the occipital condyle and C1 vertebral junction. The nerve was adequately decompressed via aspiration of the cyst. Postoperatively, the patient substantially improved. Although rare, synovial cysts must be included in the differential diagnosis of atlantooccipital lesions.
Keywords: Atlantooccipital synovial cyst; Hypoglossal nerve palsy.
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