Primary isolated skull base eosinophilic granuloma confined to the anterior clinoid process: illustrative case

BACKGROUND: Solitary eosinophilic granuloma (EG) occurs anecdotally in the skull base region, and it has been described in only three previous publications. The authors report the first case of EG of the anterior clinoid process (ACP), which was confined to the ACP and presented with decreased vision. OBSERVATIONS: A 38-year-old woman presented with decreased vision of the left eye of 5 months’ duration. Her visual acuity was 3/10, other neurological examinations were intact, and there were no other osseous or soft tissue lesions. The lesion was excised using a left-sided craniotomy and transdural clinoidectomy, decompressing the optic nerve both intra- and extradurally. The lesion was characteristic for EG, and no recurrence was detected after 2 years. LESSONS: EG can be confined to the ACP and impair vision. Imaging studies are sensitive but not specific, and surgical decompression is both diagnostic and treatment oriented. Close observation and even adjuvant therapy may be indicated in similar cases.