Magnetic resonance imaging of the brainstem and cranial nerves

Ten normal human volunteers and 44 patients with pathology of the brainstem or cranial nerves were scanned using a. 3 Tesla permanent MR imaging system. MR images were obtained of the cranial nerves and brainstem using various spin-echo pulse sequences and scanning planes. 4 mm thick sections with .75 mm pixels on a 256 display matrix were used whenever possible. The normal MR images were correlated with thin section cryodissection specimens of fresh human cadavers. Brainstem structures including major nuclei and tracts were then identified. The cranial nerves were followed through the subarachnoid cisterns and the base of the skull. Pathological involvement of the brainstem by tumors, infarcts, and demyelinating disease was well shown and correlated with clinical findings. Examples of optic glioma, fifth, eighth, and twelfth nerve schwannomas as well as other cranial nerve pathology were also demonstrated. Magnetic resonance produces excellent images of cranial nerves and brainstem with high contrast resolution. Unlike CT, there is no beam hardening artifact from bone. T1 weighted images maximize brainstem-CSF contrast and are useful for demonstrating the external anatomy of the brainstem and cranial nerves. The T2 weighted images show internal brainstem anatomy, CSF within neural foramina, and highlight many pathological conditions.