FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT skull base to mid-thigh in the initial evaluation of unilateral isolated CN XII palsy. Cranial Neuropathy MRA Head and Neck When dissection of the internal carotid artery is suspected as a cause of acute isolated CN XII palsy, MRA may be useful to evaluate for dissection. In a retrospective review of the literature comparing test performance of MRI/MRA with CTA in the assessment of cervicocephalic arterial dissection with a reference standard of catheter angiography, the authors report MRI sensitivities and specificities of 50% to 79% and 67% to 99%, respectively, and CTA sensitivities and specificities of 51% to 98% and 67% to 100%, respectively (based on prospective studies) [192]. The authors concluded that the test characteristics of MRI/MRA and CTA for diagnosis of cervicocephalic arterial dissection were similar and study selection should be based on individual factors including urgency of imaging. In another comparative study, multidetector CT/CTA demonstrated more features of cervical artery (internal carotid and vertebral arteries) dissection compared with MRI/MRA. There was no significant reader preference for MRI/MRA compared with CT/CTA when evaluating for internal carotid artery dissection. MRI/MRA provided additional characterization of ischemic complications [191]. A limitation of the literature assessing MRA and CTA for dissection is that most studies evaluate test performance in the clinical setting of traumatic dissection rather than spontaneous dissection. CTA is often used as a primary screening tool when carotid dissection is suspected in the emergent setting [190]. MRI had greater sensitivity (100%) but lower specificity (59%) for detecting hypoglossal canal invasion by glomus jugulare tumors when compared with CT (sensitivity of 87.5% and specificity of 66.7%) [183].
Cranial Neuropathy. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT skull base to mid-thigh in the initial evaluation of unilateral isolated CN XII palsy. Cranial Neuropathy MRA Head and Neck When dissection of the internal carotid artery is suspected as a cause of acute isolated CN XII palsy, MRA may be useful to evaluate for dissection. In a retrospective review of the literature comparing test performance of MRI/MRA with CTA in the assessment of cervicocephalic arterial dissection with a reference standard of catheter angiography, the authors report MRI sensitivities and specificities of 50% to 79% and 67% to 99%, respectively, and CTA sensitivities and specificities of 51% to 98% and 67% to 100%, respectively (based on prospective studies) [192]. The authors concluded that the test characteristics of MRI/MRA and CTA for diagnosis of cervicocephalic arterial dissection were similar and study selection should be based on individual factors including urgency of imaging. In another comparative study, multidetector CT/CTA demonstrated more features of cervical artery (internal carotid and vertebral arteries) dissection compared with MRI/MRA. There was no significant reader preference for MRI/MRA compared with CT/CTA when evaluating for internal carotid artery dissection. MRI/MRA provided additional characterization of ischemic complications [191]. A limitation of the literature assessing MRA and CTA for dissection is that most studies evaluate test performance in the clinical setting of traumatic dissection rather than spontaneous dissection. CTA is often used as a primary screening tool when carotid dissection is suspected in the emergent setting [190]. MRI had greater sensitivity (100%) but lower specificity (59%) for detecting hypoglossal canal invasion by glomus jugulare tumors when compared with CT (sensitivity of 87.5% and specificity of 66.7%) [183].