For detecting hypoglossal canal invasion by glomus tumors, CT had a sensitivity and specificity of 87.5% and 66.7%, respectively, compared with MRI which had a sensitivity of 100% and a specificity of 59% [183]. CTA Head and Neck When dissection of the internal carotid artery is clinically suspected as a cause of acute isolated CN XII palsy, CTA may be useful to evaluate for dissection, particularly in the emergent setting. In a study comparing CTA with conventional angiography, CTA had a sensitivity of 66% when evaluating for blunt carotid vascular injury, with most false-negatives representing low grade injuries [190]. In a 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]. 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. 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].
Cranial Neuropathy. For detecting hypoglossal canal invasion by glomus tumors, CT had a sensitivity and specificity of 87.5% and 66.7%, respectively, compared with MRI which had a sensitivity of 100% and a specificity of 59% [183]. CTA Head and Neck When dissection of the internal carotid artery is clinically suspected as a cause of acute isolated CN XII palsy, CTA may be useful to evaluate for dissection, particularly in the emergent setting. In a study comparing CTA with conventional angiography, CTA had a sensitivity of 66% when evaluating for blunt carotid vascular injury, with most false-negatives representing low grade injuries [190]. In a 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]. 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. 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].