Session's/ Radowski staging for Juvenile Nasopharyngeal angiofibroma Stage I Stage I a Limited to nasal cavity / nasopharynx Stage I b Extension into one or more sinuses. Stage II Stage II a Minimal extension into pterygopalatine fossa pterygomaxillary fissure. Stage II b Fills pterygomaxillary fossa, bowing the posterior wall of maxillary antrum anteriorly extending into the orbit the inferior orbital fissure without orbital erosion. Stage II c Infratemporal fossa extension without check or pterygoid plate involvement. Stage III Stage III a Erosion of skull base (middle cranial fossa or pterygoids) with minimal intracranial spread. Stage III b Erosion of skull base with intracranial extension with or without cavernous sinus involvement.