Facial paralysis in the form of Bell palsy is the most common cause of acute peripheral facial nerve palsy, attributed to inflammation of the facial nerve, which may be idiopathic or due to herpes simplex virus. Most patients experience complete recovery of function by 6 months, which can be hastened with steroids [102]. In general, Bell palsy patients need not be imaged unless the symptoms are atypical, recurrent, or persist for 2 to 4 months [102]. Unilateral hyperactivity of the facial nerve can occur, resulting in the spasm of the facial musculature referred to as hemifacial spasm. Hemifacial spasm is most commonly the result of vascular compression of the facial nerve, usually within the centrally (oligodendrocyte) myelinated portion of the nerve [100]. CT Head There is no relevant literature to support the use of routine CT head alone in the evaluation of unilateral isolated facial nerve palsy. CT Temporal Bone High-resolution thin-cut temporal bone CT provides complementary useful information to MRI by characterizing the osseous integrity of the temporal bone through which the facial nerve courses. CT imaging excels at osseous imaging and characterizes well temporal bone fractures, presurgical osseous anatomy, bony facial nerve canal involvement with inflammatory middle ear disease, facial canal foraminal expansion, patterns of bone erosion, and intrinsic bone tumor matrices [2,99,105-108]. High-resolution temporal bone CT with thin sections should be obtained to evaluate the course of CN VII. Contrast may be useful in the setting of infection or when a tumor is suspected. There is no relevant literature to support the use of combined pre- and postcontrast imaging. High-resolution noncontrast CT of the temporal bone is useful to characterize temporal bone fractures including fractures through the facial nerve canal, but sensitivity for nondisplaced fracture has been shown to vary with fracture location and is lowest in the mastoid segment [105,108]. Cranial Neuropathy
Cranial Neuropathy. Facial paralysis in the form of Bell palsy is the most common cause of acute peripheral facial nerve palsy, attributed to inflammation of the facial nerve, which may be idiopathic or due to herpes simplex virus. Most patients experience complete recovery of function by 6 months, which can be hastened with steroids [102]. In general, Bell palsy patients need not be imaged unless the symptoms are atypical, recurrent, or persist for 2 to 4 months [102]. Unilateral hyperactivity of the facial nerve can occur, resulting in the spasm of the facial musculature referred to as hemifacial spasm. Hemifacial spasm is most commonly the result of vascular compression of the facial nerve, usually within the centrally (oligodendrocyte) myelinated portion of the nerve [100]. CT Head There is no relevant literature to support the use of routine CT head alone in the evaluation of unilateral isolated facial nerve palsy. CT Temporal Bone High-resolution thin-cut temporal bone CT provides complementary useful information to MRI by characterizing the osseous integrity of the temporal bone through which the facial nerve courses. CT imaging excels at osseous imaging and characterizes well temporal bone fractures, presurgical osseous anatomy, bony facial nerve canal involvement with inflammatory middle ear disease, facial canal foraminal expansion, patterns of bone erosion, and intrinsic bone tumor matrices [2,99,105-108]. High-resolution temporal bone CT with thin sections should be obtained to evaluate the course of CN VII. Contrast may be useful in the setting of infection or when a tumor is suspected. There is no relevant literature to support the use of combined pre- and postcontrast imaging. High-resolution noncontrast CT of the temporal bone is useful to characterize temporal bone fractures including fractures through the facial nerve canal, but sensitivity for nondisplaced fracture has been shown to vary with fracture location and is lowest in the mastoid segment [105,108]. Cranial Neuropathy