Tap Test Can Predict Cognitive Improvement in Patients With iNPH-Results From the Multicenter Prospective Studies SINPHONI-1 and -2

Relationship between disproportionately enlarged subarachnoid-space hydrocephalus and white matter tract integrity in normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) patients had altered white matter tract integrities on diffusion tensor imaging (DTI). Previous studies suggested disproportionately enlarged subarachnoid space hydrocephalus (DESH) as a prognostic sign of NPH. We examined DTI indices in NPH subgroups by DESH severity and clinical symptoms. This retrospective case-control study included 33 NPH patients and 33 age-, sex-, and education-matched controls. The NPH grading scales (0-12) were used to rate neurological symptoms. Patients with NPH were categorized into two subgroups, high-DESH and low-DESH groups, by the average value of the DESH scale. DTI indices, including fractional anisotropy, were compared across 14 regions of interest (ROIs). The high-DESH group had increased axial diffusivity in the lateral side of corona radiata (1.43 ± 0.25 vs. 1.72 ± 0.25, p = 0.04), and showed decreased fractional anisotropy and increased mean, and radial diffusivity in the anterior and lateral sides of corona radiata and the periventricular white matter surrounding the anterior horn of lateral ventricle. In patients with a high NPH grading scale, fractional anisotropy in the white matter surrounding the anterior horn of the lateral ventricle was significantly reduced (0.36 ± 0.08 vs. 0.26 ± 0.06, p = 0.03). These data show that DESH may be a biomarker for DTI-detected microstructural alterations and clinical symptom severity.

Predictive Ability of Frontal Assessment Battery for Cognitive Improvement After Shunt Surgery in Individuals With Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

The predictive ability of the Frontal Assessment Battery (FAB) for postoperative cognitive improvement in idiopathic normal pressure hydrocephalus (iNPH) is unstudied.

OBJECTIVE

To compare the predictive ability of the FAB and the Mini-Mental State Examination (MMSE) for postoperative cognitive improvement in individuals with iNPH after shunt surgery.

METHOD

We retrospectively reviewed the medical records of individuals with iNPH who had shunt surgery between January 2016 and October 2018. Individuals had completed the tap test and clinical evaluations (FAB, MMSE, Timed Up and Go [TUG]) both before and 24-48 hours after CSF tapping and after surgery. We excluded individuals without complete clinical evaluations and those with shunt surgery performed >6 months after CSF tapping. Factors associated with postoperative FAB and MMSE improvement as per the 2011 iNPH guidelines were extracted using univariate and multivariate logistic regression analyses. Independent variables were baseline FAB and MMSE scores, FAB and MMSE score changes and TUG amelioration rate after CSF tapping, Evans index, age, and days from CSF tapping to surgery and from surgery to postoperative assessment.

RESULTS

The mean number of days from CSF tapping to surgery and from surgery to postoperative assessment were 77.5 (SD = 36.0) and 42.0 (SD = 14.5), respectively. Logistic regression analyses showed significant associations in the univariate analyses of postoperative FAB improvement with baseline FAB scores ( P = 0.043) and with FAB score changes after CSF tapping ( P = 0.047).

CONCLUSION

The FAB may help predict postoperative cognitive improvement after shunt surgery better than the MMSE.

Reconsidering Ventriculoperitoneal Shunt Surgery and Postoperative Shunt Valve Pressure Adjustment: Our Approaches Learned From Past Challenges and Failures

Treatment for idiopathic normal pressure hydrocephalus (iNPH) continues to develop. Although ventriculoperitoneal shunt surgery has a long history and is one of the most established neurosurgeries, in the 1970s, the improvement rate of iNPH triad symptoms was poor and the risks related to shunt implantation were high. This led experts to question the surgical indication for iNPH and, over the next 20 years, cerebrospinal fluid (CSF) shunt surgery for iNPH fell out of favor and was rarely performed. However, the development of programmable-pressure shunt valve devices has reduced the major complications associated with the CSF drainage volume and appears to have increased shunt effectiveness. In addition, the development of support devices for the placement of ventricular catheters including preoperative virtual simulation and navigation systems has increased the certainty of ventriculoperitoneal shunt surgery. Secure shunt implantation is the most important prognostic indicator, but ensuring optimal initial valve pressure is also important. Since over-drainage is most likely to occur in the month after shunting, it is generally believed that a high initial setting of shunt valve pressure is the safest option. However, this does not always result in sufficient improvement of the symptoms in the early period after shunting. In fact, evidence suggests that setting the optimal valve pressure early after shunting may cause symptoms to improve earlier. This leads to improved quality of life and better long-term independent living expectations. However, in iNPH patients, the remaining symptoms may worsen again after several years, even when there is initial improvement due to setting the optimal valve pressure early after shunting. Because of the possibility of insufficient CSF drainage, the valve pressure should be reduced by one step (2–4 cmH₂O) after 6 months to a year after shunting to maximize symptom improvement. After the valve pressure is reduced, a head CT scan is advised a month later.