Thinner slice axial DWI or thin-section coronal DWI may improve sensitivity for detecting small acute brainstem infarction, with nearly 25% of acute brainstem infarcts more easily seen on thin-cut coronal DWI compared with standard axial DWI in one study [138,194]. 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 within the jugular foramen, and their relationship to the hypoglossal nerve as they exit the skull base, with 90% to 100% of imaged CN IX, CN X, and CN XII visible [24]. There is variable direct visualization of CN XI with the cranial segment identified in 88% of the sides and the spinal segment identified in 93% of the sides in one study [149]. Another study reported lower rates with the spinal root of CN XI visualized in only 51% of subjects using heavily T2-weighted contrast-enhanced modified balanced SSFP sequences [24]. DWI can be used to assess for acute brainstem infarction, cholesteatoma, and for characterizing tumor cellularity. False-negative DWI can occur in the setting of very small ischemic brainstem infarcts [137,138]. Thinner slice axial DWI or thin-section coronal DWI may improve sensitivity for detecting acute brainstem infarction, with nearly 25% of acute brainstem infarcts more easily seen on thin-cut coronal DWI compared with standard axial DWI in one study [138,194]. US Neck There is no relevant literature to support the use of US neck in the initial evaluation of multiple lower CN palsies. Variant 10: Head and neck cancer. Suspected or known perineural spread of tumor. Initial imaging. The compact anatomy of the brainstem results in close proximity of multiple CN nuclei, and the complex anatomy of the head and neck results in close proximity and interconnection of multiple CNs, which can lead to multiple cranial neuropathies. Multiple middle and lower CN palsies are discussed in Variant 4 and 9, respectively.
Cranial Neuropathy. Thinner slice axial DWI or thin-section coronal DWI may improve sensitivity for detecting small acute brainstem infarction, with nearly 25% of acute brainstem infarcts more easily seen on thin-cut coronal DWI compared with standard axial DWI in one study [138,194]. 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 within the jugular foramen, and their relationship to the hypoglossal nerve as they exit the skull base, with 90% to 100% of imaged CN IX, CN X, and CN XII visible [24]. There is variable direct visualization of CN XI with the cranial segment identified in 88% of the sides and the spinal segment identified in 93% of the sides in one study [149]. Another study reported lower rates with the spinal root of CN XI visualized in only 51% of subjects using heavily T2-weighted contrast-enhanced modified balanced SSFP sequences [24]. DWI can be used to assess for acute brainstem infarction, cholesteatoma, and for characterizing tumor cellularity. False-negative DWI can occur in the setting of very small ischemic brainstem infarcts [137,138]. Thinner slice axial DWI or thin-section coronal DWI may improve sensitivity for detecting acute brainstem infarction, with nearly 25% of acute brainstem infarcts more easily seen on thin-cut coronal DWI compared with standard axial DWI in one study [138,194]. US Neck There is no relevant literature to support the use of US neck in the initial evaluation of multiple lower CN palsies. Variant 10: Head and neck cancer. Suspected or known perineural spread of tumor. Initial imaging. The compact anatomy of the brainstem results in close proximity of multiple CN nuclei, and the complex anatomy of the head and neck results in close proximity and interconnection of multiple CNs, which can lead to multiple cranial neuropathies. Multiple middle and lower CN palsies are discussed in Variant 4 and 9, respectively.