2025 Poster Presentations
P204: SKULL BASE MALIGANCY MIMICKING OSTEOMYELITIS IN A 6-YEAR OLD
Avraham Adelman, BS; Nikita Chapurin, MD, MHS; Brian Lobo, MD; Si Chen, MD; University of Florida
Case: A 6-year-old immunocompetent girl, with history of 2 acute otitis media episodes, presented to the ED with a 3-week history of sixth cranial nerve palsy and a new complete seventh cranial nerve palsy. She did not have pain or otorrhea. CT showed mucosal thickening in the left sphenoid sinus and mastoid. MRI revealed a 1.3 cm rim-enhancing lesion with destruction in the left petrous apex. Her white blood cell count was normal and ESR was elevated. A nuclear scan demonstrated avid uptake in the left petrous apex. The top differential diagnosis was skull base osteomyelitis. After 2.5 weeks of antibiotics, there was no improvement in her cranial nerve functions. Repeat MRI showed the lesion expanded significantly into the sphenoid sinus. An endoscopic sphenoidotomy obtained tissue biopsy which revealed rhabdomyosarcoma. A CT chest revealed lung metastases, leading to chemoradiation.
Discussion: Rhabdomyosarcoma (RMS) is a rare malignant tumor, with about 35% occurring in the head and neck. It often presents in advanced stages with cranial nerve palsies. On MRI, RMS typically appears iso-intense on T1-weighted images with strong enhancement post-contrast and moderate intensity on T2-weighted images. On CT, it is slightly hypodense with bone destruction. RMS can mimic osteomyelitis on nuclear medicine scans, showing increased uptake, especially after gallium. The petrous apex, a possible primary site, is difficult to access for biopsy. This case highlights that diagnosing RMS in the petrous apex can be difficult due to its similarity to osteomyelitis and surgical access challenges.