Stimulation of the frontal eye field, located in the caudal part of the middle frontal gyrus (area 8), usually results in conjugate deviation of the eyes to the opposite side. In looking at these slices, the radiologist is able to assess skull bones for injury, infection, fluid. Lesions of the caudal PPRF may cause paralysis of horizontal eye movements, while lesions of the rostral PPRF can cause paralysis of vertical eye movements. A computed tomography scan (CT or CAT) of the internal auditory canal, also called cross-sectional imaging, allows the radiologist to look at different levels, or slices, of the skull bones leading from the ear using a rotating X-ray beam. Fibers from the caudal PPRF project to the ipsilateral abducens nucleus, while fibers from the rostral PPRF project uncrossed fibers to the RiMLF, which in turn projects to the ipsilateral oculomotor nuclear complex. Start Preamble Start Printed 70 AGENCY: Centers for Medicare & Medicaid Services (CMS), HHS. It is used to evaluate normal anatomic structures, evaluate for vestibular schwannomas, assess for inflammatory and/or infectious processes, and detect residual and/or recurrent cholesteatoma. Stimulation of the caudal and rostral PPRF produces conjugate horizontal eye deviation and vertical eye movements respectively. MRI is firmly established as an essential modality in the imaging of the temporal bone and lateral skull base. Enlargement of the Internal Auditory Canal and Associated Posterior Fossa Anomalies in PHACES Association. In addi- tion, 3-T imaging can be completed with shorter acqui- sition times. A, Axial T2-weighted sampling perfection with application-optimized contrasts by using flip angle evolution (SPACE) image demonstrates a well-circumscribed mass in the left IAC (arrow). found 2.5 mm mass in right internal canal consistent with acoustic neuroma. The center for horizontal gaze (the abducens nucleus) and the center for vertical gaze (the rostral interstitial nucleus of the medial longitudinal fasciculus, or RiMLF), are joined physiologically by the paramedian pontine reticular formation (PPRF), which lies rostral to the abducens nucleus. Our institution conducts the vast majority of internal au- ditory canal (IAC) MRI examinations with 3-T magnets, which allow for a superior signal-to-noise ratio and higher spatial resolution compared with 1.5-T imaging. Figure 1: MRI scans of inner auditory canal (IAC) lipoma in a 54-year-old man demonstrate the usefulness of fat saturation.
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