Solving the Riddle of “Idiopathic” in Idiopathic Intracranial Hypertension and Normal Pressure Hydrocephalus: An Imaging Study of the Possible Mechanisms – Monro–Kellie 3.0

BACKGROUND: Idiopathic intracranial hypertension (IIH) and normal pressure hydrocephalus (NPH) represent a cluster of typical clinical and imaging findings, with no evident etiological cause noted. In this study, we have proposed a model for IIH and NPH called Monroe–Kellie 3.0 (MK 3.0). IIH and NPH may be entities which represent opposite sides of the same coin with venous system and cerebrospinal fluid (CSF) as core drivers for both these entities. MATERIALS AND METHODS: IIH and NPH volume data were collected, voxel-based morphometry analysis was performed without normalization, and the distribution of the individual volumes of gray matter, white matter, and CSF was statistically analyzed. Visual morphometry analyses of segmented data were performed, and the findings in routine magnetic resonance imaging (MRI) were noted to build a model for IIH and NPH. RESULTS: In IIH and NPH when the volumes were compared with controls, the distribution was similar. Furthermore, the morphometric changes noted in the MRI and segmented volume data were analyzed and the results were suggestive of changes in elastic property of brain causing a remodeling of brain shape and resulting in minor brain shift in the skull vault, and the resulting passive displacement of CSF which has been termed as MK 3.0. CONCLUSION: This model helps to put the clinical and imaging findings and complications of treatment in single perspective.