Jang H, et al. - The authors investigated whether amyloid positron emission tomography ([18F] florbetaben (FBB) PET) could be used to determine concomitant Alzheimer’s disease (AD) in idiopathic normal pressure hydrocephalus (iNPH) patients. They proposed that amyloid PET scans could help in determining which idiopathic normal pressure hydrocephalus (iNPH) patients would benefit from shunt surgery by discriminating concomitant Alzheimer’s disease (AD).

Methods

• The authors performed FBB PET scans and the tap test in 31 patients with clinically suspected iNPH.
• They compared amyloid positive (iNPH/FBB+) and negative (iNPH/FBB-) groups with respect to clinical characteristics.
• Using a linear mixed model, they assessed prognostic value of FBB PET scans by analyzing the response to the tap test.
• Furthermore, they performed a multivariable regression analysis to examined whether amyloid PET positivity could predict the positive tap test response independent of other AD biomarkers.

Results

• Compared to the iNPH/FBB- group (24/31, 77.4%), the iNPH/FBB+ group (7/31, 22.6%) had a higher percentage of APOE4 carriers, lower Aβ₄₂, higher CSF t-tau, and p-tau/Aβ₄₂ ratio, while the 2 groups did not differ in imaging characteristics.
• Patients in the iNPH/FBB- group had a higher percentage of tap responders and demonstrated a greater improvement in gait scores after the tap test than the iNPH/FBB+ group (group-tap test effect interaction, p=0.035).
• In multivariable logistic regression analysis, the authors showed that amyloid positivity on PET scans (OR 0.03, p=0.029) and CSF p-tau (OR 0.87, p=0.044) were independently associated with the positive tap test response.
• Fourteen patients received shunt surgery among 21 tap responders in the iNPH/FBB- group.
• Out of them, 12 (85.7%) patients showed symptom improvement.