Cavernous sinus syndrome from clival metastasis as the initial presentation of disseminated prostate adenocarcinoma: a case report and literature review.

Prostate adenocarcinoma commonly metastasises to the axial skeleton, but skull base deposits with acute cranial nerve palsies as the first clinical sign are unusual. We report a 68-year-old man admitted with one month history of dyspnoea and weakness, who was found to have severe microcytic anaemia (haemoglobin 6.5 g/dL) with stool positive for occult blood; upper gastrointestinal endoscopy showed only mild antral gastritis. During the first week he developed left-sided ptosis, progressing over three days to complete ophthalmoplegia with binocular diplopia. Gadolinium-enhanced MRI of the brain showed a destructive clival deposit with heterogeneous enhancement extending into the left cavernous sinus. On directed questioning the patient admitted to a five-month history of lower urinary tract symptoms (LUTS) dismissed as age-related. Serum prostate-specific antigen was 754 ng/mL. Cross-sectional imaging and multiparametric prostate MRI confirmed a Prostate Imaging Reporting and Data System (PIRADS) 5 lesion with widespread pulmonary, mediastinal nodal, pelvic nodal and skeletal metastases. The hospital course was complicated by severe hyponatraemia with a high urine sodium (43 mEq/L), supporting the syndrome of inappropriate antidiuresis. Transrectal ultrasound-guided biopsy confirmed prostatic adenocarcinoma. The case is a reminder that cranial nerve palsies in an elderly man can be the first visible sign of silent disseminated prostate cancer, and that asking directly about urinary symptoms at every clinical encounter matter, even though such symptoms are not themselves a reliable indicator of early disease.