Combined Transnasal and Transcranial Approach for a Complex Type IV Nasal Dermoid Sinus Cyst

BACKGROUND AND IMPORTANCE: Nasal dermoid sinus cysts (NDSCs) are rare congenital midline anomalies caused by incomplete separation of ectoderm and neuroectoderm during embryogenesis. Intracranial extension, although uncommon, increases the risk of infection, recurrence, and neurological complications. Hartley type IV lesions involve the intradural compartment and represent the most complex subtype. CLINICAL PRESENTATION: A 13-year-old boy presented with a congenital nasal tip pit associated with recurrent swelling and serous discharge since age 9. MRI and computed tomography revealed a midline fistulous tract extending through the foramen cecum, with extradural intrafalcine and intradural frontobasal components, consistent with a type IV NDSC. Complete excision was achieved through a combined transnasal interalar and transcranial transfrontal approach. The extracranial tract was dissected to the foramen cecum, and the intracranial component was removed by interhemispheric dissection. Endoscopic assistance confirmed a deformed foramen cecum, reconstructed with polymethylmethacrylate. The postoperative course was uneventful, with no neurological deficits. Imaging confirmed complete resection without recurrence. Histopathology demonstrated abundant keratinous debris, confirming a dermoid lesion. CONCLUSION: This case highlights the importance of multidisciplinary planning and tailored craniofacial strategies in managing complex NDSCs with intracranial extension. The combined transnasal and transcranial approach enabled radical excision while preserving anatomic and functional integrity.