Left temporal skull mass and pain. History of neurofibromatosis type I. There is a well-circumscribed, lobulated left temporal scalp mass. The mass is closely related to or within the temporalis muscle. The main bulk of the mass is composed of multiple smaller nodules that are peripherally T2 hyperintense and centrally T1-hypointense (target sign). The nodules show intense, heterogeneous contrast enhancement. The main bulk of the mass collectively measures in the axial plane 4.9 cm x 1.6 cm and craniocaudally 4.4 cm. Smaller similar masses are present superficial to the temporalis muscle. In addition to this well-circumscribed component, the left temporalis muscle shows diffuse abnormal signal and contrast enhancement which tapers distally, perhaps though not definitively reflective of infiltration. While the underlying skull is not infiltrated/invaded, the mass extends inferiorly to cause chronic remodeling of the lateral aspect of the temporal bone without deep infiltration. It causes mass effect on the external auditory canal as well. The brain shows no abnormality but this is a limited assessment. The dural venous sinuses are patent. Major intracranial arteries are patent as well. There is no orbital abnormality. There are no signs of sphenoid wing dysplasia. The paranasal sinuses are clear.
Left temporal scalp mass as described above compatible with neurofibroma. In addition to the main component of discrete nodular lesions, there is an infiltrative pattern of enhancement which tapers more distally in the left scalp. This could represent subtle tumor infiltration or a reactive phenomenon. While there is no gross osseous invasion, there is chronic remodeling of the mastoid air cells as described above.