Peripheral Facial Palsy in Small Cell Lung Cancer with Mastoid Metastasis.

Introduction: Peripheral facial palsy is commonly associated with benign self-limited conditions. In rare circumstances, it may be the manifestation of underlying malignancy. Case description: We present an unusual case of a 53-year-old woman with previously diagnosed small cell lung cancer (SCLC), who developed sudden-onset peripheral facial palsy. Imaging studies revealed mastoid metastasis with facial nerve involvement and venous sinus thrombosis, despite a normal MRI performed just one month prior. Despite ongoing treatment, the disease showed rapid progression culminating in the patient's death. Discussion: Metastatic involvement of the mastoid is extremely rare in SCLC. Such metastases can occur via haematogenous or meningeal spread, resulting in complex clinical phenotypes with mastoid involvement, including facial palsy and venous sinus thrombosis among others. Conclusion: This case emphasises the importance of individualised assessment in peripheral facial palsy and vigilance regarding unusual metastatic patterns in cancer patients. The rapid clinical deterioration despite appropriate treatment underscores both the aggressive nature of SCLC and the critical need for more effective treatment strategies. LEARNING POINTS: Small cell lung cancer's neuroendocrine nature drives metastasis to unexpected territories, including the rarely affected mastoid region.In patients with peripheral facial palsy and malignancy risk factors, prompt imaging should be considered, even when other suspicious features are absent.Small cell lung cancer evolves rapidly in spite of treatment, requiring vigilance for metastatic complications despite reassuringly normal recent examinations.