18F-FDG PET-CT pattern in idiopathic normal pressure hydrocephalus.

Ryan A Townley,Bradley F Boeve,Matthew L Senjem,David S Knopman,Val Lowe,David T Jones,Hugo Botha,Ronald C Petersen,Clifford R Jack,Jonathan Graff-Radford

doi:10.1016/j.nicl.2018.02.031

Abstract

BackgroundIdiopathic normal pressure hydrocephalus (iNPH) is an important and treatable cause of neurologic impairment. Diagnosis is complicated due to symptoms overlapping with other age related disorders. The pathophysiology underlying iNPH is not well understood. We explored FDG-PET abnormalities in iNPH patients in order to determine if FDG-PET may serve as a biomarker to differentiate iNPH from common neurodegenerative disorders.MethodsWe retrospectively compared 18F-FDG PET-CT imaging patterns from seven iNPH patients (mean age 74 ± 6 years) to age and sex matched controls, as well as patients diagnosed with clinical Alzheimer's disease dementia (AD), Dementia with Lewy Bodies (DLB) and Parkinson's Disease Dementia (PDD), and behavioral variant frontotemporal dementia (bvFTD). Partial volume corrected and uncorrected images were reviewed separately.ResultsPatients with iNPH, when compared to controls, AD, DLB/PDD, and bvFTD, had significant regional hypometabolism in the dorsal striatum, involving the caudate and putamen bilaterally. These results remained highly significant after partial volume correction.ConclusionsIn this study, we report a FDG-PET pattern of hypometabolism in iNPH involving the caudate and putamen with preserved cortical metabolism. This pattern may differentiate iNPH from degenerative diseases and has the potential to serve as a biomarker for iNPH in future studies. These findings also further our understanding of the pathophysiology underlying the iNPH clinical presentation.

Highlights

Idiopathic normal pressure hydrocephalus is a treatable neurologic syndrome which has become more relevant in recent years due to an aging population
When Idiopathic normal pressure hydrocephalus (iNPH) patients were compared to controls, striatal hypometabolism was highly significant (p < 0.0001)
When iNPH patients were compared to Alzheimer's disease dementia (AD) and Dementia with Lewy Bodies (DLB)/Parkinson's Disease Dementia (PDD) groups, the differences in striatum hypometabolism were highly significant (p < 0.003)

Summary

Introduction

Idiopathic normal pressure hydrocephalus (iNPH) is a treatable neurologic syndrome which has become more relevant in recent years due to an aging population. Urinary incontinence, and cognitive impairment occur more commonly with increasing age – ranging from 15 to 42% depending on the population studied (Coyne et al, 2014; Petersen et al, 2014; Sudarsky, 1990) This complicates the diagnosis of iNPH, the treatment approach, and outcome measurements. Patients are selected following a multimodal, staged evaluation which includes clinical examination, neuroimaging, and often a large volume spinal tap This process is complicated by the fact that iNPH can be difficult to differentiate from other neurodegenerative diseases causing ventriculomegaly. Results: Patients with iNPH, when compared to controls, AD, DLB/PDD, and bvFTD, had significant regional hypometabolism in the dorsal striatum, involving the caudate and putamen bilaterally These results remained highly significant after partial volume correction. These findings further our understanding of the pathophysiology underlying the iNPH clinical presentation

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