Chiari Type 1 Malformation-induced Intracranial Hypertension with Diffuse Brain Edema Treated with Foramen Magnum Decompression: A Case Report.

Chiari type 1 malformation (CM1) rarely causes papilloedema, which is indicative of high intracranial pressure with or without ventricular dilatation. Furthermore, concomitant brain parenchymal abnormalities have not been reported to date. In this paper, the authors report on a young woman of CM1-induced intracranial hypertension (ICH) with diffuse brain edema with a focus on venous sinus assessment, and discuss the surgical strategy. A 24-year-old woman presented to Nagoya University Hospital complaining of 4-year history of severe occipital headache and blurry vision with slowly progressive worsening. Head and whole spine MRI showed a CM1 with diffuse white matter hyperintensities (WMH) on T2-weighted imaging and narrowed brain sulci without hydrocephalus. Lumbar puncture revealed extremely high opening pressure. Detailed blood examination and other radiographical imaging studies denied the presence of tumor, collagen disease, encephalitis and other entities. Head magnetic resonance venography and angiography demonstrated severe transverse sinus stenosis on both sides. Foramen magnum decompression was performed to alleviate the ICH by restoration of cerebrospinal fluid (CSF) stagnation at the foramen magnum with successful outcome. The patient completely recovered from preoperative symptoms immediately after surgery. The diffuse WMH and narrowing brain sulci have been resolving. The most feasible explanation for this complicated pathophysiology was ICH induced by CM1 led to transverse sinus collapse, resulting in diffuse WMH as a result of venous hypertension. This case report is the first illustration of successful surgical treatment of CM1 with diffuse brain edema with a focus on venous sinus assessment.