Rationale and Objective
The aim of this study was to determine the distinctive features of normal-pressure hydrocephalus (NPH) and other dementias on routine T1-weighted and T2-weighted magnetic resonance (MR) images. Also, the contribution of these parameters to the diagnosis and treatment of NPH was investigated.
Materials and Methods
Routine MR images were used to investigate the morphologic features (dilatation of Sylvian cisterns, narrowness of convexity sulci, thickness of corpus callosum (TCC), and dilatation of perihippocampal fissures) and the flow void phenomenon (FVP) in patients with idiopathic NPH (INPH) and other dementias. Routine MR images of 18 patients with INPH, 11 with dementias other than INPH, and 20 controls were retrospectively examined. Morphologic features and the FVP were graded subjectively. The TCC was measured quantitatively. Morphologic parameters, the FVP, and the shunt response were assessed using Kruskal-Wallis and Mann-Whitney U tests.
Results
The mean FVP score was significantly higher in patients with INPH (2.89 ± 0.75) than in controls and patients with other dementias (1.1 ± 0.85 and 1.09 ± 0.83, respectively) ( P < .001). There was significant difference in terms of TCC between patients with INPH (3 ± 0.7 mm), those with other dementias (1.9 ± 0.7 mm), and controls (5.2 ± 0.8 mm) ( P < .001). Significant differences in terms of other morphologic features were found between patients with INPH and those with other dementias ( P < .05). No significant difference was found between morphologic parameters and the FVP and the outcome of cerebrospinal fluid diversion ( P > .05).
Conclusions
Intense FVP is a signature of but is not pathognomonic for INPH. The morphologic analysis of MR images can be distinctive for the diagnosis of INPH or dementias other than INPH. Detailed evaluation of morphologic features and the FVP in routine MR workup of dementia will be useful for accurate diagnosis.
Normal-pressure hydrocephalus (NPH), a rare disease in the population, is generally seen in the elderly . NPH may be either idiopathic (INPH) or secondary to subarachnoid hemorrhage, meningitis, cranial trauma, and intracranial surgery . INPH is characterized by gait disturbance, dementia, and/or urinary incontinence with normal opening pressure at lumbar puncture in patients without causative disorders, and ventricular enlargement due to disturbed cerebrospinal fluid (CSF) circulation .
Diagnosis of INPH is of great importance. Because many patients with possibly curable INPH often are misdiagnosed as having Alzheimer’s disease (AD) or vascular dementia, improvement after the temporary removal of CSF and shunt surgery is not always adequately provided . Magnetic resonance imaging (MRI) is an important neuroimaging technique in the diagnosis of INPH. Presence of the flow void phenomenon (FVP) on T2-weighted (T2W) images supports the diagnosis . The degree of the FVP has been reported to correlate with shunt efficacy . Specific morphologic changes, including enlarged Sylvian fissures and tight medial parietal sulci, ventriculomegaly without enlargement of the convexity sulci and perihippocampal fissures (PHFs), and the thickness of the corpus callosum (TCC) on conventional cranial MRI are also useful . Some studies have shown that the FVP and these morphologic magnetic resonance (MR) changes have no additive diagnostic and prognostic value for INPH . As a result of these conflicting results, the value of the FVP and specific morphologic MR changes as diagnostic tests in INPH is uncertain.
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Materials and methods
Subjects
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Table 1
Demographic Characteristics of the Groups
Variable Group 1: Patients with INPH Group 2: Patients with Other Dementias Group 3: Controls Number of cases (women/men) 18 (10/8) 11 (5/6) 20 (10/10) Mean age (y) (range) 66 (50–75) 64 (45–79) 53 (40–75)
INPH, idiopathic normal-pressure hydrocephalus.
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MR Procedure
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Data Analysis
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Results
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Table 2
Shunt Outcomes, FVP Scores, and Morphologic Features of Patients with Probable INPH (Group 1)
Patient Sex Age (y) Gait Apraxia Urinary Incontinence Dementia TCC (mm) SWCL SCW Dilatation of PHFs FVP Shunt Outcome 1 F 75 + + + 4 0 2 0 3 + 2 F 63 + + + 3 0 2 0 4 − 3 M 65 + + + 3 1 1 0 3 − 4 M 70 + − + 4 0 2 1 3 + 5 M 66 + + + 2 1 1 1 2 + 6 M 66 + + + 3 1 1 0 2 + 7 F 68 + + + 3 1 1 1 3 + 8 F 50 + − + 3 0 2 0 2 − 9 M 50 + − + 4 1 2 0 3 + 10 F 75 + + + 2 1 2 1 4 + 11 F 70 + − + 3 2 2 1 3 + 12 M 73 + + + 3 2 3 2 2 − 13 M 59 + + + 3 1 2 1 2 − 14 F 60 + + + 2 1 1 1 4 − 15 M 73 + + + 3 0 2 0 3 + 16 F 57 + + + 2 0 3 1 2 + 17 F 74 + + + 4 1 2 1 3 + 18 F 72 + + + 3 1 2 1 4 +
FVP, flow void phenomenon; INPH, idiopathic normal pressure hydrocephalus; PHF, perihippocampal fissure; SCW, Sylvian cistern width; SWCL, sulcal width at convexity level; TCC, thickness of the corpus callosum.
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Table 3
Morphologic Characteristics of the Groups
P Value Mean Score NPH Group OD Group Control Group Among Groups NPH vs Control NPH vs OD OD vs. Control Shunt Response FVP 2.89 ± 0.7 1.09 ± 0.8 1.1 ± 0.8 <.001 <.001 <.001 NS NS TCC (mm) 3 ± 0.7 1.91 ± 0.7 5.2 ± 0.8 <.001 <.001 .001 <.001 NS Dilatation of PHFs 0.66 ± 0.6 2 ± 1.09 0.7 ± 0.5 <.001 NS .001 .001 NS SCW 1.83 ± 0.6 2.63 ± 0.7 1.35 ± 0.8 <.001 NS <.05 <.001 NS SWCL 0.77 ± 0.6 1.91 ± 0.7 0.9 ± 0.6 .001 NS .001 <.05 NS
FVP, flow void phenomenon; NPH, normal-pressure hydrocephalus; NS, not significant; PHF, perihippocampal fissure; OD, other dementias; SCW, Sylvian cistern width; SWCL, sulcal width at convexity level; TCC, thickness of the corpus callosum.
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Discussion
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Conclusions
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