We studied the effects on CSF dynamics at the foramen magnum and the clinical significance of the abnormal tonsillar motion in 14 patients with Chiari type I malformation and 14 control subjects using cine phase-contrast MRI. Dynamic MRI consisted of axial and sagittal cine phase-contrast sequences. CSF and tonsillar motion were qualitatively and quantitatively evaluated, and the subarachnoid space at the foramen magnum measured. In Chiari patients, cine phase-contrast MRI detected the abnormal pulsatile motion of the cerebellar tonsils, which produced a selective obstruction of CSF flow from the cranial cavity to the spine. The amplitude of the tonsillar pulsation and the severity of the arachnoid space reduction were associated with the symptom of cough-strain headache, but not with the presence of syringomyelia. The finding of abnormal valve dynamics of the cerebellar hernia revealed by cine phase-contrast MRI conforms to the pathophysiologic mechanisms suggested in pressure register studies and opens a new possibility in the presurgical assessment of Chiari patients with exertional symptoms.

The clinical presentation of Pourfour du Petit syndrome (PdPs) is the opposite of Horner syndrome. Although all disorders underlying Horner syndrome may potentially present as PdPs, very few cases of the latter have been described in the literature. We report a patient with PdPs due to carotid compression by a thyroid tumor.

Symptomatic suprageniculate lesions in multiple sclerosis expressed as a visual field defect are infrequent. The present case developed a bilateral homonymous defect as the initial and unique symptom of the disease. It was confirmed by nuclear magnetic resonance imaging, which disclosed extensive demyelinating areas in both optic nerve radiations. The mode of onset, perimetric findings, and unusual presentation of this condition are briefly discussed.

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