Cerebrospinal Fluid Leak Rhinorrhea after Systemic Erlotinib Chemotherapy for Metastatic Lung Cancer: A Familiar Problem from an Unfamiliar Culprit

Background Cerebrospinal fluid (CSF) rhinorrhea after medical therapy for pituitary prolactinoma is a rare but well-described phenomenon. To our knowledge, no CSF leaks have been reported after targeted medical treatment of pituitary or anterior skull base metastases. We report this unusual case to raise awareness of spontaneous CSF leaks in the setting of skull base metastatic disease. Case Presentation A 66-year-old woman presented with epidermal growth factor receptor–mutant stage IV adenocarcinoma of the lung. Headache workup revealed a large sellar and clival lesion consistent with metastatic disease. Systemic erlotinib chemotherapy was initiated with a robust positive response. Approximately 1 week after chemotherapy initiation, the patient noted clear discharge from the right nostril. Her oncologist first diagnosed her with allergic rhinitis, but she presented with meningitis 4 days after diagnosis of CSF leak and was admitted for intravenous antibiotics and definitive repair of a CSF leak via an endoscopic endonasal approach. An erosion of bone and dura was found at the dorsum sellae where tumor had regressed due to the chemotherapy. A multilayer skull base repair was made uneventfully, and she recovered fully with no leakage seen at 2-month follow-up. Conclusions All members of the treatment team should be aware of this possibility of CSF leak after initiation of systemic chemotherapy and tumor regression and urgently refer patients for repair if a leak should develop before the development of meningitis.