Pituitary stone resulting in visual dysfunction and spontaneous rhinorrhea in nonfunctioning pituitary adenoma: illustrative case

BACKGROUND: Calcifications in pituitary adenomas are rare, being found in only 5.4%–25% of reported cases. These are divided into eggshell-like calcifications around the tumor and nodular calcifications at the center of the tumor, the latter of which are called “pituitary stones” (PSs). OBSERVATIONS: The authors report the case of a 60-year-old male with a nonfunctional pituitary adenoma with PSs and asymptomatic ventricular dilatation who presented with spontaneous cerebrospinal fluid (CSF) rhinorrhea and rapid visual aggravation without an increase in tumor size over the course of 4 years. After endoscopic transnasal surgery, his visual acuity immediately improved temporarily. It was believed that the increased intracranial pressure due to secondary hydrocephalus resulted in visual aggravation; thus, a ventriculoperitoneal (VP) shunt was created. After creation of the VP shunt, the patient’s visual acuity improved gradually and completely. Histological findings showed that adenoma cells were observed among the lamellar bone trabeculae. To the best of the authors knowledge, this is the first report of osteoid metaplasia–type PSs in nonfunctioning pituitary adenoma. LESSONS: PSs formed near the sellar floor and caused spontaneous CSF rhinorrhea due to direct mechanical stress on the dura mater and optic nerves, which may have caused meningitis and secondary hydrocephalus that resulted in visual impairment independent of tumor size.