Parkinsonism Differentiates Idiopathic Normal Pressure Hydrocephalus from Its Mimics

Association between high plasma p-tau181 level and gait changes in patients with mild cognitive impairment

Previous studies on gait changes in mild cognitive impairment (MCI) are inconsistent. Alzheimer's disease (AD) plasma biomarkers, amyloid beta (Aβ) and phosphorylated-tau (p-tau), are relevant to gait disorders. This study explores gait changes in MCI and the relationship between gait performance and AD plasma biomarkers. 231 participants were recruited and stratified based on p-tau181 levels into: low p-tau181 with normal cognition (lT-NC), low p-tau181 with MCI (lT-MCI), and high p-tau181 with MCI (hT-MCI). The same cohort was subsequently stratified by Aβ42/Aβ40 levels into: high Aβ42/Aβ40 with normal cognition (hA-NC), high Aβ42/Aβ40 with MCI (hA-MCI), and low Aβ42/Aβ40 with MCI (lA-MCI). Demographic, cognitive and gait data were compared across groups. The hT-MCI and lA-MCI groups were older than the other groups. Significant differences in stride length were found between lT-NC and hT-MCI, lT-MCI and hT-MCI, but not between lT-NC and lT-MCI. Neuropsychological assessments revealed poorer performance in hT-MCI and lT-MCI groups relative to lT-NC, while global cognitive function was comparable between hT-MCI and lT-MCI groups. No such associations were observed between stride length and Aβ42/Aβ40 levels. Decreased stride length, which is generally considered to be indicative of poorer gait, was significantly associated with elevated p-tau181 levels and independent of global cognitive status. These findings highlight the potential of p-tau181 as a biomarker for tau-related motor dysfunction in MCI.

Hakim's disease: an update on idiopathic normal pressure hydrocephalus

INTRODUCTION

Idiopathic normal pressure hydrocephalus (iNPH) increases with age but is still underdiagnosed and undertreated. In the last decade, iNPH research has expanded into understanding broader contributions to iNPH, the role of cerebrospinal fluid (CSF), and imaging biomarkers to aid early detection, help diagnosis and differentiation from iNPH mimics, and aid with outcome prediction.

EVIDENCE ACQUISITION

We performed a literature search on the PubMed database. English language articles published between 2015-2024 were included. The strategies focused on iNPH and specific terms related to the topics of this review.

EVIDENCE SYNTHESIS

We first addressed the ambiguity of current classification terminology and reviewed the newly proposed classification system. This review has shown that prevalence is higher than previously reported. We have reviewed imaging and found numerous highly sensitive and specific imaging markers to aid diagnosis and differentiate from common mimics. CSF biomarkers have revealed that amyloid β and tau levels were lower in iNPH patients, which helped with differentiation from iNPH mimics, and that other emerging inflammatory markers need to be studied further. We also found numerous promising genetic markers in familial iNPH involved in cilial dysfunction, neuroinflammation, and neurodegeneration. Literature also reported the frequent presence of spinal stenosis, and studies reported better iNPH outcomes when these were addressed.

CONCLUSIONS

This has shown that there is a need for the development of a structured and standardized classification system, iNPH assessment protocol with standardized testing, and standardized biomarkers to aid diagnosis and treatment, and that this needs an interdisciplinary team approach.

Parkinsonism and cerebrospinal fluid disorders

BACKGROUND

Although various motor manifestations can be seen in patients with cerebrospinal fluid (CSF) disorders, such as hydrocephalus or intracranial hypotension, the clinical presentation with parkinsonism is not clearly elucidated.

METHODS

We searched the literature for studies describing the occurrence of parkinsonism in subjects with normal pressure hydrocephalus (NPH), obstructive hydrocephalus, and intracranial hypotension. We analyzed the clinical presentation (particularly with respect to bradykinesia, rigidity, rest tremor, and gait disturbance/postural instability) as well as the response to treatment.

RESULTS

Parkinsonism was most commonly reported in NPH patients. Although gait disturbance/postural instability is a well-known motor symptom of NPH, other cardinal signs include upper limb involvement or asymmetric presentation. As for obstructive hydrocephalus, parkinsonism was mainly observed in subjects with aqueductal stenosis and more often after shunt surgery. Patients with NPH or obstructive hydrocephalus rarely improved with levodopa therapy, while most subjects only improved with shunt surgery. Although the mechanism is still controversial, a functional involvement of nigrostriatal pathway has been hypothesized based on imaging studies and case reports. Brain imaging is also helpful for atypical cases of intracranial hypotension presenting with parkinsonism. Parkinsonism improved after treatment in such cases as well.

CONCLUSIONS

Studies exploring the relationship between CSF disorders and parkinsonism are mainly descriptive and their quality is generally poor. However, considering that these disorders can be treated, clinicians' awareness of the differential diagnosis is important and future studies better exploring the underlying pathophysiological mechanisms are warranted. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.

Cerebrospinal Fluid Amyloid-β Oligomer Levels in Patients with Idiopathic Normal Pressure Hydrocephalus

BACKGROUND

The amyloid-β oligomers, consisting of 10-20 monomers (AβO10-20), have strong neurotoxicity and are associated with cognitive impairment in Alzheimer's disease (AD). However, their role in patients with idiopathic normal pressure hydrocephalus (iNPH) is poorly understood.

OBJECTIVE

We hypothesized that cerebrospinal fluid (CSF) AβO10-20 accumulates in patients with iNPH, and its clearance after CSF shunting contributes to neurological improvement. We measured CSF AβO10-20 levels before and after CSF shunting in iNPH patients evaluating their diagnostic and prognostic role.

METHODS

We evaluated two iNPH cohorts: "evaluation" (cohort-1) with 32 patients and "validation" (cohort-2) with 13 patients. Comparison cohorts included: 27 neurologically healthy controls (HCs), and 16 AD, 15 Parkinson's disease (PD), and 14 progressive supranuclear palsy (PSP) patients. We assessed for all cohorts CSF AβO10-20 levels and their comprehensive clinical data. iNPH cohort-1 pre-shunting data were compared with those of comparison cohorts, using cohort-2 for validation. Next, we compared cohort-1's clinical and CSF data: 1) before and after CSF shunting, and 2) increased versus decreased AβO10-20 levels at baseline, 1 and 3 years after shunting.

RESULTS

Cohort-1 had higher CSF AβO10-20 levels than the HCs, PD, and PSP cohorts. This result was validated with data from cohort-2. CSF AβO10-20 levels differentiated cohort-1 from the PD and PSP groups, with an area under receiver operating characteristic curve of 0.94. AβO10-20 levels in cohort-1 decreased after CSF shunting. Patients with AβO10-20 decrease showed better cognitive outcome than those without.

CONCLUSION

AβO10-20 accumulates in patients with iNPH and is eliminated by CSF shunting. AβO10-20 can be an applicable diagnostic and prognostic biomarker.

Clinical Outcome and Striatal Dopaminergic Function After Shunt Surgery in Patients With Idiopathic Normal Pressure Hydrocephalus

OBJECTIVE

To determine changes in clinical features and striatal dopamine reuptake transporter (DAT) density after shunt surgery in patients with idiopathic normal pressure hydrocephalus (iNPH).

METHODS

Participants with probable iNPH were assessed at baseline by means of clinical rating scales, brain MRI, and SPECT with [¹²³I]-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (FP-CIT). Levodopa responsiveness was also evaluated. Patients who did or did not undergo lumboperitoneal shunt were clinically followed up and repeated SPECT after 2 years.

RESULTS

We enrolled 115 patients with iNPH. Of 102 patients without significant levodopa response and no signs of atypical parkinsonism, 92 underwent FP-CIT SPECT (58 also at follow-up) and 59 underwent surgery. We identified a disequilibrium subtype (phenotype 1) and a locomotor subtype (phenotype 2) of higher-level gait disorder. Gait impairment correlated with caudate DAT density in both phenotypes, whereas parkinsonian signs correlated with putamen and caudate DAT binding in patients with phenotype 2, who showed more severe symptoms and lower striatal DAT density. Gait and caudate DAT binding improved in both phenotypes after surgery (p < 0.01). Parkinsonism and putamen DAT density improved in shunted patients with phenotype 2 (p < 0.001). Conversely, gait, parkinsonian signs, and striatal DAT binding worsened in patients who declined surgery (p < 0.01).

CONCLUSIONS

This prospective interventional study highlights the pathophysiologic relevance of striatal dopaminergic dysfunction in the motor phenotypic expression of iNPH. Absence of levodopa responsiveness, shunt-responsive parkinsonism, and postsurgery improvement of striatal DAT density are findings that corroborate the notion of a reversible striatal dysfunction in a subset of patients with iNPH.

Neuropsychological tests are useful for predicting comorbidities of idiopathic normal pressure hydrocephalus

Objectives

Comorbidities of idiopathic normal pressure hydrocephalus (iNPH), such as Alzheimer's disease (AD) and Parkinson's spectrum (PS) disorder, can affect the long‐term prognosis of cerebrospinal fluid (CSF) shunting. Therefore, it is important to be able to predict comorbidities in the early stage of the disease. This study aimed to predict the comorbidities of iNPH using neuropsychological tests and cognitive performance evaluation.

Materials & Methods

Forty‐nine patients with possible iNPH were divided into three groups: iNPH without AD or PS comorbidity (group‐1), iNPH with AD comorbidity (group‐2), and iNPH with PS comorbidity (group‐3), according to CSF biomarkers such as phosphorylated tau and dopamine transporter imaging. Scores on the new EU‐iNPH‐scale, which is based on 4 neuropsychological tests (Rey Auditory Verbal Learning Test, Grooved Pegboard test, Stroop colour‐naming test and interference test), were compared for each group. In addition, the scores before and 12 months after CSF shunting for each group were compared.

Results

EU‐iNPH‐scale using 4 neuropsychological tests could distinguish group‐1 from group‐2 or group‐3 by area under the curve values of 0.787 and 0.851, respectively. Patients in group‐1 showed a remarkable increase in memory and learning ability after surgery. Group‐2 performed significantly poorer than group‐1 patients on memory testing, but otherwise showed improvements in most of the neuropsychological tests. Group‐3 performed significantly worse than group‐1 patients—especially on Stroop tests—but showed post‐surgery improvement on only the Stroop colour‐naming test.

Conclusions

The 4 neuropsychological tests of the EU‐iNPH‐scale can help predict iNPH comorbidities and evaluate the prognosis of CSF shunting.

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.

Neural circuits of idiopathic Normal Pressure Hydrocephalus: A perspective review of brain connectivity and symptoms meta-analysis

Idiopathic normal pressure hydrocephalus (iNPH) is a prevalent reversible neurological disorder characterized by impaired locomotion, cognition and urinary control with ventriculomegaly. Symptoms can be relieved with cerebrospinal fluid drainage, which makes iNPH the leading cause of reversible dementia. Because of a limited understanding of pathophysiological mechanisms, unspecific symptoms and the high prevalence of comorbidity (i.e. Alzheimer's disease), iNPH is largely underdiagnosed. For these reasons, there is an urgent need for developing noninvasive quantitative biomarkers for iNPH diagnosis and prognosis. Structural and functional changes of brain circuits in relation to symptoms and treatment response are expected to deliver major advances in this direction. We review structural and functional brain connectivity findings in iNPH and complement those findings with iNPH symptom meta-analyses in healthy populations. Our goal is to reinforce our conceptualization of iNPH as to brain network mechanisms and foster the development of new hypotheses for future research and treatment options.

Is frontal gait a myth in normal pressure hydrocephalus?

BACKGROUND

Patients with idiopathic normal pressure hydrocephalus (iNPH) are considered to present a magnetic, slow, wide-based gait, also called frontal gait. However, this gait profile is not specific for iNPH and encountered in patients with other neurological conditions mimicking iNPH (i.e. iNPH mimics), such as vascular dementia. We aimed to characterize the gait profiles in iNPH and their mimics and to compare the prevalence of clinical gait abnormalities between both groups.

METHODS

This retrospective study included 140 patients suspected of iNPH (76.3 ± 6.8 yo; 30.7% female). Eighty patients (57.1%) were diagnosed with iNPH according to the NPH consensus guidelines criteria; the remaining sixty patients were classified as mimics (23 neurodegenerative conditions, 12 multifactorial conditions, 9 vascular dementia, 7 mixed dementias, 6 toxic conditions, 2 psychiatric conditions, and 1 stroke). Two independent diagnosis-blinded clinicians (kappa, 0.73) evaluated gait according to four categories: frontal gait, parkinsonian gait, other clinical gait abnormalities, and normal gait.

RESULTS

iNPH patients and mimics shared similar clinical characteristics. Frontal gait occurred in only 26% of patients (with a similar prevalence for the mimics). Parkinsonian gait was significantly more prevalent among the mimics (32% versus 15%; p-value: 0.032). This association between parkinsonian gait and mimics remained significant after adjusting for age, gender, comorbidities and white matter changes (OR: 2.404; 95% CI: [1.03-5.64]; p value: 0.044).

CONCLUSION

Frontal gait is not the most prevalent gait abnormality in iNPH and does not discriminate iNPH from its mimics. Parkinsonian gait is more prevalent among the mimics.

Current Updates on Idiopathic Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is one of the neurodegenerative diseases which can be treated surgically with favorable outcome. The gait disturbance, cognitive, and urinary symptoms are known as the clinical triad of iNPH. In this review, we have addressed the comorbidities, differential diagnoses, clinical presentations, and pathology of iNPH. We have also summarized the imaging studies and clinical procedures used for the diagnosis of iNPH. The treatment modality, outcomes, and prognosis were also discussed.