Absence of Disproportionately Enlarged Subarachnoid Space Hydrocephalus, a Sharp Callosal Angle, or Other Morphologic MRI Markers Should Not Be Used to Exclude Patients with Idiopathic Normal Pressure Hydrocephalus from Shunt Surgery

Diagnostic accuracy of the iNPH Radscale in idiopathic normal pressure hydrocephalus

Background and purpose

The idiopathic normal pressure hydrocephalus (iNPH) Radscale was developed to standardize the evaluation of radiological signs in iNPH. The purpose of this study was to estimate the diagnostic accuracy of the iNPH Radscale in a sample of “true positive” and “true negative” cases.

Methods

Seventy-five patients with definite iNPH, i.e. who had improved at clinical follow-up one year after ventriculoperitoneal shunt surgery, were compared with 55 asymptomatic individuals from the general population. A radiologist assessed the seven radiological features of the iNPH Radscale in computed tomography of the brain in the patients (preoperatively) and controls.

Results

The iNPH Radscale score was significantly higher in the iNPH group (Median = 10, interquartile range 9–11) than in the control group (Median = 1, interquartile range 1–2) (p <0.001). Receiver operated characteristics analysis yielded an area under the curve of 99.7%, and an iNPH Radscale score ≤ 4 identified those without iNPH, with a sensitivity of 100%, specificity of 96% and overall accuracy of 98.5%.

Conclusions

In this study, iNPH Radscale could accurately discriminate between patients with definite iNPH and asymptomatic individuals over 65 years old. According to the results, a diagnosis of iNPH is very likely in patients with an iNPH Radscale score above 8 and corresponding clinical symptoms. On the other hand, the diagnosis should be questioned when the iNPH Radscale score is below the cut-off level of 4. We conclude that the iNPH Radscale could work as a diagnostic screening tool to detect iNPH. Whether the scale also can be used to predict shunt outcome needs further studies.

Dopaminergic Degeneration and Small Vessel Disease in Patients with Normal Pressure Hydrocephalus Who Underwent Shunt Surgery

The diagnosis of idiopathic normal pressure hydrocephalus (iNPH) and the outcome of lumboperitoneal shunt treatment remains to be systematically explored. Here, we aim to evaluate whether the severity of dopaminergic degeneration and white matter small vessel disease could be predictors of outcome for iNPH patients subjected to lumboperitoneal shunt treatment. This is a single center retrospective study with 39 patients with probable iNPH undergoing programmable surgical lumboperitoneal shunt from June 2016 to March 2018 at Hualien Tzu Chi Hospital. In all patients, dopaminergic degeneration was determined with ^99mTc- TRODAT-1 SPECT scan, while white matter small vessel disease (Fazekas scale) was assessed with Brain MRI. The iNPH grading scale (iNPHGS) score and Karnofsky Performance Score (KPS) pre- and post-operation (6-month follow-up) were available for all patients. Linear regression was used to correlate the severities of dopaminergic degeneration and small vessel disease with lumboperitoneal shunt treatment outcomes. Their iNPHGS score improved significantly after surgery (pre-operatively, 7.8 ± 2.6; post-operatively, 5.7 ± 2.6 (26.9% improvement) (p < 0.05)). Moreover, the KPS was also improved significantly after surgery, by a mean of 24.6% from the baseline score (p < 0.05). A significant correlation was observed between the severity of dopaminergic degeneration and a poorer improvement of iNPHGS score (p = 0.03). However, improvement of the iNPHGS score was not correlated with white matter small vessel disease. Dopaminergic degeneration comorbidity neutralized the degree of improvement after surgery. Although white matter small vessel disease was correlated with iNPH incidence, it may not be a prognostic factor for shunt operation. These findings have implications for the use of dopaminergic imaging, as they might help predict the surgical outcome of patients with iNPH, while vascular mechanisms seem to be involved in iNPH pathophysiology.

Reliability and Interobserver Variability of Evans' Index and Disproportionately Enlarged Subarachnoid Space Hydrocephalus as Diagnostic Criteria for Idiopathic Normal Pressure Hydrocephalus

Background:

The image diagnosis of idiopathic normal-pressure hydrocephalus (iNPH) is based on the ventriculomegaly, whose criterion is an Evans' Index (EI) >0.3. Recently, disproportionately enlarged subarachnoid space hydrocephalus (DESH) has been proposed as a morphological characteristic to iNPH. Several studies cast doubt on the reliability of these criteria in the diagnosis of iNPH. Furthermore, interobserver differences of these criteria have not yet been investigated. The objective of this study was to assess the diagnostic reliability and interobserver variability of EI and DESH.

Materials and Methods:

The preoperative magnetic resonance (MR) images of 84 definite iNPH patients were retrospectively evaluated by a neuroradiologist (NR) and physical therapist (PT). They independently assessed the EI and DESH. The MR images were evaluated preoperatively by a neurosurgeon (NS). The results were showed in mean (standard deviation).

Results:

The mean age was 78.4 (6.3) years (male:female = 49:35). The mean EI was 0.33 (0.04), 0.32 (0.04), and 0.31 (0.03) for NS, NR, and PT, respectively (P < 0.0001). The rate of accurate diagnosis of iNPH with EI >0.3 was 74%, 66%, and 61% for NS, NR, and PT, respectively, and there was a moderate level of agreement. By contrast, there was a substantial lower level of accuracy in assessment with DESH for all three evaluators as 50%, 44%, and 27% for NS, NR, and PT, respectively, again with a moderate level of agreement. However, the rates of patients fulfilling both EI >0.3 and DESH were remarkably lower than either of the two parameters individually at a mere 37%, 30%, and 16% for NS, NR, and PT, respectively, with a low level of agreement between the rates.

Conclusion:

This study suggests that DESH cannot be a diagnostic criterion for iNPH. If EI >0.3 and DESH were both necessary to diagnose iNPH, then more than 70% of patients would have been misdiagnosed and would have been deprived of the chance of treatment and its benefits. These results request a paradigm shift in the concepts of iNPH.

Neuroimaging of Normal Pressure Hydrocephalus and Hydrocephalus

Since the clinical syndrome of progressive gait disturbance, urinary incontinence, and dementia in the setting of occult hydrocephalus responsive to cerebrospinal fuid (CSF) shunting was first reported in 1965, the existence of a potentially reversible cause for a form of a dementia illness has generated extensive clinical research and numerous clinical trials. Idiopathic normal pressure hydrocephalus (iNPH) continues to be a heavily debated clinical syndrome. This paper reviews guidelines and imaging findings most often associated with iNPH and the relationship of the neuroimaging findings to some of the theories for this complex syndrome.

The year in review: progress in brain barriers and brain fluid research in 2018

This editorial focuses on the progress made in brain barrier and brain fluid research in 2018. It highlights some recent advances in knowledge and techniques, as well as prevalent themes and controversies. Areas covered include: modeling, the brain endothelium, the neurovascular unit, the blood–CSF barrier and CSF, drug delivery, fluid movement within the brain, the impact of disease states, and heterogeneity.