Denervation injury changes that occur within the tongue in the setting of hypoglossal nerve palsy vary with acuity and can be detected on MRI and CT, with MRI providing better soft tissue contrast [186-188]. Thin-cut heavily T2-weighted contrast- enhanced modified balanced SSFP sequences and contrast-enhanced MRA focused on the posterior skull provide detailed imaging of the lower nerves with 90% to 100% of imaged CN XII visible [24]. 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]. Denervation injury changes that occur within the tongue in the setting of hypoglossal nerve palsy vary with acuity and can be detected on MRI and CT, with MRI providing better soft tissue contrast [186-188]. Thin-cut heavily T2-weighted contrast- enhanced modified balanced SSFP sequences and contrast-enhanced MRA focused on the posterior skull provide detailed imaging of the lower nerves with 90% to 100% of imaged CN XII visible [24]. Cranial Neuropathy US Neck There is no relevant literature to support the use of US neck in the initial evaluation of unilateral isolated CN XII palsy. Variant 9: Multiple different lower cranial nerve palsies or combined lower cranial nerve syndromes (CN IX-XII). Initial imaging. The medulla oblongata joins the pons to the spinal cord and is composed of a ventral portion and a dorsal tegmentum. The ventral portion contains the pyramids and olives, and the dorsal tegmentum contains CN IX through CN XII nuclei along with the white matter sensory tracts. Vascular supply to the medulla is from the anterior spinal artery, branches of the vertebral arteries, and the posterior inferior cerebellar arteries [1,131]. Outside the brainstem, CN IX through CN XI traverse the jugular foramen, and CN XII traverses the hypoglossal canal in the posterior skull base before extending caudally into the neck.
Cranial Neuropathy. Denervation injury changes that occur within the tongue in the setting of hypoglossal nerve palsy vary with acuity and can be detected on MRI and CT, with MRI providing better soft tissue contrast [186-188]. Thin-cut heavily T2-weighted contrast- enhanced modified balanced SSFP sequences and contrast-enhanced MRA focused on the posterior skull provide detailed imaging of the lower nerves with 90% to 100% of imaged CN XII visible [24]. 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]. Denervation injury changes that occur within the tongue in the setting of hypoglossal nerve palsy vary with acuity and can be detected on MRI and CT, with MRI providing better soft tissue contrast [186-188]. Thin-cut heavily T2-weighted contrast- enhanced modified balanced SSFP sequences and contrast-enhanced MRA focused on the posterior skull provide detailed imaging of the lower nerves with 90% to 100% of imaged CN XII visible [24]. Cranial Neuropathy US Neck There is no relevant literature to support the use of US neck in the initial evaluation of unilateral isolated CN XII palsy. Variant 9: Multiple different lower cranial nerve palsies or combined lower cranial nerve syndromes (CN IX-XII). Initial imaging. The medulla oblongata joins the pons to the spinal cord and is composed of a ventral portion and a dorsal tegmentum. The ventral portion contains the pyramids and olives, and the dorsal tegmentum contains CN IX through CN XII nuclei along with the white matter sensory tracts. Vascular supply to the medulla is from the anterior spinal artery, branches of the vertebral arteries, and the posterior inferior cerebellar arteries [1,131]. Outside the brainstem, CN IX through CN XI traverse the jugular foramen, and CN XII traverses the hypoglossal canal in the posterior skull base before extending caudally into the neck.