RESUMEN
Spontaneous meningoencephaloceles (MECs) are sparsely documented in the literature. Those occurring in the frontal sinus are an exceedingly rare entity. MECs are commonly associated with cerebrospinal fluid (CSF) rhinorrhoea. CSF rhinorrhoea is frequently misdiagnosed, causing delays in diagnosis and management. The subsequently increased risk of bacterial meningitis can be life-threatening to patients. We report the case of a woman in her late 70s with a spontaneous frontal sinus MEC, presenting with a 6-month history of CSF rhinorrhoea. The patient was successfully treated using the novel Carolyn's window approach endoscopically; 9-month follow-up revealed no skull-base breach. Our case emphasises the importance of considering MEC as a differential diagnosis for clear rhinorrhoea and demonstrates successful repair through a novel surgical approach.