Perineural tumor spread can lead to isolated or multiple CN palsies and is the macroscopic spread of tumor along the course of a nerve distant from the site of the primary tumor as detected on imaging. It should be distinguished from perineural invasion, which is local invasion detected on histopathologic diagnosis at the primary tumor site [66,124]. Perineural tumor spread on imaging is associated with a worse prognosis [195]. The trigeminal (CN V) and facial (CN VII) nerves are most commonly affected by perineural tumor spread, although any nerve traveling in the vicinity of a malignancy may become involved. A multitude of tumors can result in perineural tumor spread, with squamous cell carcinoma (cutaneous and mucosal), adenoid cystic carcinoma, melanoma, lymphoma, basal cell carcinoma, and mucoepidermoid carcinoma most commonly occurring in the head and neck. Clues to perineural tumor spread include effacement of perineural and juxtaforaminal fat; asymmetric nerve enlargement or enhancement; osseous foraminal enlargement or erosion; and imaging features of denervation injury [65,66,104,123,124,196]. CT Head There is no relevant literature to support the use of routine head CT in the initial evaluation of perineural spread of tumor. CT Maxillofacial There is no relevant literature to support the use of routine maxillofacial CT in the initial evaluation of perineural spread of tumor. Contrast-enhanced maxillofacial CT may be complementary to MRI and is useful for characterizing osseous changes of skull base and neural foramina; however, contrast-enhanced neck CT with thin- cut high-resolution bone algorithm windows through the skull base can provide similar information while Cranial Neuropathy simultaneously staging the neck [64,66]. There is no relevant literature to support the use of combined pre- and postcontrast imaging. CT Temporal Bone There is no relevant literature to support the use of routine temporal bone CT in the initial evaluation of perineural spread of tumor.
Cranial Neuropathy. Perineural tumor spread can lead to isolated or multiple CN palsies and is the macroscopic spread of tumor along the course of a nerve distant from the site of the primary tumor as detected on imaging. It should be distinguished from perineural invasion, which is local invasion detected on histopathologic diagnosis at the primary tumor site [66,124]. Perineural tumor spread on imaging is associated with a worse prognosis [195]. The trigeminal (CN V) and facial (CN VII) nerves are most commonly affected by perineural tumor spread, although any nerve traveling in the vicinity of a malignancy may become involved. A multitude of tumors can result in perineural tumor spread, with squamous cell carcinoma (cutaneous and mucosal), adenoid cystic carcinoma, melanoma, lymphoma, basal cell carcinoma, and mucoepidermoid carcinoma most commonly occurring in the head and neck. Clues to perineural tumor spread include effacement of perineural and juxtaforaminal fat; asymmetric nerve enlargement or enhancement; osseous foraminal enlargement or erosion; and imaging features of denervation injury [65,66,104,123,124,196]. CT Head There is no relevant literature to support the use of routine head CT in the initial evaluation of perineural spread of tumor. CT Maxillofacial There is no relevant literature to support the use of routine maxillofacial CT in the initial evaluation of perineural spread of tumor. Contrast-enhanced maxillofacial CT may be complementary to MRI and is useful for characterizing osseous changes of skull base and neural foramina; however, contrast-enhanced neck CT with thin- cut high-resolution bone algorithm windows through the skull base can provide similar information while Cranial Neuropathy simultaneously staging the neck [64,66]. There is no relevant literature to support the use of combined pre- and postcontrast imaging. CT Temporal Bone There is no relevant literature to support the use of routine temporal bone CT in the initial evaluation of perineural spread of tumor.