Cerebrospinal Fluid Biomarker and Brain Biopsy Findings in Idiopathic Normal Pressure Hydrocephalus
et al. (2014) Cerebrospinal Fluid Biomarker and Brain Biopsy Findings in Idiopathic Normal
Pressure Hydrocephalus. PLoS ONE 9(3): e91974. doi:10.1371/journal.pone.0091974
Cerebrospinal Fluid Biomarker and Brain Biopsy Findings in Idiopathic Normal Pressure Hydrocephalus
Okko T. Pyykko 0
Miikka Lumela 0
Jaana Rummukainen 0
Ossi Nerg 0
Toni T. Seppa la 0
Massimo S. Fiandaca, Georgetown University Medical Center, United States of America
0 1 Neurosurgery of NeuroCenter, Kuopio University Hospital , Kuopio , Finland , 2 Neurology of NeuroCenter, Kuopio University Hospital , Kuopio , Finland , 3 Department of Neurology, Institute of Clinical Medicine, University of Eastern Finland , Kuopio , Finland , 4 Department of Pathology, Kuopio University Hospital , Kuopio , Finland , 5 Department of Immunology , Genetics and Pathology , Uppsala University , Uppsala , Sweden , 6 Clinical Neurochemistry Laboratory, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy, University of Gothenburg , Gothenburg , Sweden
Background: The significance of amyloid precursor protein (APP) and neuroinflammation in idiopathic normal pressure hydrocephalus (iNPH) and Alzheimer's disease (AD) is unknown. Objective: To investigate the role of soluble APP (sAPP) and amyloid beta (Ab) isoforms, proinflammatory cytokines, and biomarkers of neuronal damage in the cerebrospinal fluid (CSF) in relation to brain biopsy Ab and hyperphosphorylated tau (HPt) findings. Methods: The study population comprised 102 patients with possible NPH with cortical brain biopsies, ventricular and lumbar CSF samples, and DNA available. The final clinical diagnoses were: 53 iNPH (91% shunt-responders), 26 AD (10 mixed iNPH+AD), and 23 others. Biopsy samples were immunostained against Ab and HPt. CSF levels of AD-related biomarkers (Ab42, p-tau, total tau), non-AD-related Ab isoforms (Ab38, Ab40), sAPP isoforms (sAPPa, sAPPb), proinflammatory cytokines (several interleukins (IL), interferon-gamma, monocyte chemoattractant protein-1, tumor necrosis factor-alpha) and biomarkers of neuronal damage (neurofilament light and myelin basic protein) were measured. All patients were genotyped for APOE. Results: Lumbar CSF levels of sAPPa were lower (p,0.05) in patients with shunt-responsive iNPH compared to non-iNPH patients. sAPPb showed a similar trend (p = 0.06). CSF sAPP isoform levels showed no association to Ab or HPt in the brain biopsy. Quantified Ab load in the brain biopsy showed a negative correlation with CSF levels of Ab42 in ventricular (r = 20.295, p = 0.003) and lumbar (r = 20.356, p = 0.01) samples, while the levels of Ab38 and Ab40 showed no correlation. CSF levels of proinflammatory cytokines and biomarkers of neuronal damage did not associate to the brain biopsy findings, diagnosis, or shunt response. Higher lumbar/ventricular CSF IL-8 ratios (p,0.001) were seen in lumbar samples collected after ventriculostomy compared to the samples collected before the procedure. Conclusions: The role of sAPP isoforms in iNPH seems to be independent from the amyloid cascade. No neuroinflammatory background was observed in iNPH or AD.
Funding: This study was funded by the Health Research Council of the Academy of Finland, The Finnish Medical Foundation, EVO/VTR grants from the Kuopio
University Hospital 5252614, 5772708, the strategic funding from the University of Eastern Finland, and Finnish Cultural Foundations North Savo Regional Fund.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Idiopathic normal pressure hydrocephalus (iNPH) is a
progressive neurodegenerative disorder of unknown etiology in the elderly
presenting with gait disorder, cognitive impairment, and urinary
incontinence, with enlarged ventricles of the brain but normal or
slightly elevated cerebrospinal fluid (CSF) pressure [1,2]. Currently
there is no pathological hallmark for iNPH . Studies suggesting
some potential genetic background of iNPH have been published
[4,5]. The present treatment of choice in iNPH is CSF diversion
with an implanted shunt that relieves or even reverses the
symptoms. Various procedures to evaluate CSF dynamics in
patients with possible iNPH are used to identify those who could
benefit from CSF shunting. These include the CSF tap test,
external lumbar drainage test, infusion tests, and intraventricular
or intracranial pressure (ICP) monitoring . The most
frequent differential diagnoses of iNPH are atypical Alzheimers
disease (AD) and vascular dementia [8,10].
AD is characterized by the hallmark lesions of amyloid-b (Ab)
plaques and neurofibrillary tangles composed of
hyperphosphorylated tau (HPt) in the brain of patients with amnestic cognitive
decline . The amyloid cascade hypothesis states that Ab
starts to accumulate decades before the clinical manifestations of
AD [14,15]. In vivo, Ab can be detected directly with brain biopsy
[8,16], or indirectly by observing low levels of Ab in CSF .
Fibrillar Ab can also be evaluated by positron emission
tomography (PET) utilizing e.g. the 11C-labeled Pittsburgh
compound B  or [18F]flutemetamol .
Although common pathways for iNPH and AD have been
proposed , the findings in genetic  and Ab studies 
suggest differences in etiologies of the two diseases. Ab and HPt in
the CSF may help to differentiate iNPH and AD patient groups or
detect comorbid AD in iNPH . In addition, these biomarkers
have shown a potency to predict response to shunt in iNPH
Ab originates from a cell membrane-spanning protein, amyloid
precursor protein (APP), which has diverse roles in normal
neuronal function . Soluble APP alpha (sAPPa) and beta
(sAPPb) result from the cleavage of APP by a- and b-secretases,
respectively. Low CSF levels of sAPP isoforms have been reported
in post-stroke patients and iNPH compared to AD and normal
healthy controls . In addition, sAPPa has shown a marked
prognostic value for cognitive performance following shunt surgery
, and subsequent increase of ventricular sAPP-levels has been
noted in shunt-responders .
Abnormal levels of proinflammatory cytokines, such as
interleukins (IL), interferon-gamma (IFN-c), monocyte chemoattractant
protein-1 (MCP-1), and tumor necrosis factor-alpha (TNF-a), in
CSF have been noted in various diseases of the nervous system,
including AD . In iNPH, several proinflammatory cytokines
have been studied, but none of them has proven to be useful in
diagnostics . Lower levels of IL-1b in NPH compared to AD
was reported in a single paper , while increased levels of IL-4
and IL-10 were reported in patients with NPH compared to
healthy individuals in another study, but no significant difference
was seen between NPH and other dementias . No differences
were found between NPH and AD or healthy controls in studies
comparing the levels of IL-8, IL-10, IL-12 (p40 and p70), IFN-c,
and transforming growth factor-b1 (TGF- b1) [28,33]. However,
iNPH patients did show increased levels of MCP-1 compared to
healthy individuals . Prior to treatment, higher TNF-a
concentrations (and subsequent normalization after shunting) in
CSF were observed in NPH patients compared to healthy controls
in a single study ; however, these results did not replicate in a
more recent study with solely idiopathic NPH patients .
Elevated levels of neurofilament light protein (NFL) in the CSF,
indicating neuronal death and axonal loss, have been found in
iNPH and secondary NPH in several studies [28,3639].
Increased levels of myelin basic protein (MBP) in the CSF is a
well-established biomarker for demyelination and myelin damage
in the central nervous system . Furthermore, elevated levels of
MBP have been reported in NPH .
To our knowledge, studies assessing the association between
proinflammatory cytokines and biomarkers of neuronal damage in
CSF, and cortical brain biopsy have not been published to date.
The objectives of the current study were:
1. to determine the levels of AD-related biomarkers (Ab42,
ptau, total tau), non-AD-related Ab isoforms (Ab38, Ab40), sAPP
isoforms (sAPPa, sAPPb), proinflammatory cytokines (IL 1b, 2, 4,
5, 8, 10, 12p70, and 13, IFN-c, MCP-1, TNF-a) and biomarkers
of neuronal damage (NFL, MBP) in lumbar and ventricular CSF,
and how they correlate,
2. study the relationship between the CSF biomarkers and
cortical brain biopsy,
3. assess the diagnostic and prognostic value of the CSF
biomarkers in iNPH and AD.
This study was approved by the Kuopio University Hospital
(KUH) Research Ethical Committee, The Finnish National
Supervisory Authority for Welfare and Health, and The Finnish
Ministry of Social Affairs and Health. All participants or their
proxies gave a written, informed consent prior to participation in
the study. If the clinician suspected dementia to significantly affect
the capacity of the patient to consent, a next of kin, caretakers or
guardians consented on the behalf of participants. When a consent
was obtained from a participants proxy, the patients own opinion
was inquired and considered, and no patients were recruited
against their will.
Kuopio NPH Registry and Protocol
Neurosurgery of KUH solely provides full-time acute and
elective neurosurgical services for the KUH catchment population
in Middle and Eastern Finland. In addition, the KUH area
contains four central hospitals with neurological units and
catchment areas of their own .
Patients fulfilling the following criteria were further assessed in
KUH Neurosurgery as possible NPH patients: (1) primary
evaluation and examination by a neurologist indicating NPH; (2)
one to three symptoms suggestive of NPH (gait disorder, cognitive
impairment, urinary incontinence); and (3) NPH related brain
imaging findings (enlarged ventricles (Evans index.0.3) together
with obliterated cortical sulci). The diagnostic workup protocol of
KUH Neurosurgery for possible NPH included a clinical
examination, CT or MRI scan, and 24 h intraventricular ICP
monitoring together with a frontal cortical brain biopsy. Kuopio
NPH Registry (www.uef.fi/nph) consists of all evaluated possible
NPH patients from the KUH catchment population since 1993
The ICP criteria for the shunt treatment in iNPH patients were
(1) a basal ICP pressure between 10 and 20 mmHg continuously,
or (2) the presence of A-waves or more than 30% B-waves during
the 24 h monitoring, when basal pressure was between 5 and
10 mmHg .
Altogether 102 patients, 51 men and 51 women, with a median
age of 74.6 years (range 4787 years) from the Kuopio NPH
Registry with cortical brain biopsy, APOE genotype, and a
ventricular CSF sample available were included in the study
(Table 1). 63 patients were diagnosed with iNPH according to the
protocol above, and were shunted with ventriculoperitoneral shunt
(PS Medical medium pressure or adjustable valve). The clinical
response to shunt was evaluated at 23 months after surgery, and
any subjective or objective improvement in patient gait, memory
or urinary continence was graded as a positive shunt response.
Clinical AD was diagnosed according to a protocol described
earlier [8,10,21] in 26 patients (including 10 patients with initial/
primary diagnosis of iNPH) in a median follow-up time of 2.3
years (range 0.26.2 years).
Age (years) (median (range))
Leading symptom, n (%)
Immunoreactivity (n (%))
APOE-e4 carriers (n (%))
Follow-up time (years) (median (range))
Possible NPH (n = 102)
Final clinical diagnosis of iNPH (n = 53)
Shunt responder Shunt nonresponder
Mixed iNPH + AD
No diagnosis of iNPH (n = 39)
Abreviations: APOE, apolipoprotein E gene; CSF, cerebrospinal fluid; NPH, normal pressure hydrocephalus; iNPH, idiopathic NPH; AD, Alzheimers disease; Ab, amyloid
beta protein; HPt, hyperphosphorylated tau protein.
Immunohistochemistry and histological evaluation
Biopsy samples representing frontal cortex and subcortical white
matter were stained with hematoxylin-eosin and immunostained
with monoclonal antibodies directed to Ab (6F/3D) and HPt
(AT8) as described earlier in detail [8,21]. Positive Ab
immunostain was further quantified and reported as ratio of area covered
by Ab to total area of cortex in the biopsy as described earlier .
DNA was extracted from venous blood using commercial kit
according to manufacturers protocol (Illustra Blood GenomicPrep
Mini Spin Kit, GE Healthcare, Little Chalfont, UK). A standard
PCR method was used in the APOE genotyping [21,42].
CSF samples and biomarker analyses
The ventricular CSF samples were collected immediately after
the placement of intraventricular catheter (first 1 mL discarded) in
the ICP measurement procedure. In addition, a lumbar CSF
sample was available in 49 patients. The lumbar samples were
obtained through a lumbar puncture prior to the ICP
measurement protocol (12 patients) or 2448 hours after introducing the
ventricular catheter (37 patients).
Levels of AD biomarkers (Ab42, p-tau, total tau) were measured
from the CSF samples using commercial ELISA kits (Innotest
bamyloid142, Innotest Phosphotau(181P), Innotest Tau-Ag,
Innogenetics, Ghent, Belgium) according to the manufacturers protocol
at validated laboratory in Neurology (www.uef.fi/neuro),
University of Eastern Finland, Kuopio, Finland as described earlier .
Ab isoforms (Ab38, Ab40), sAPP isoforms (sAPPa, sAPPb), and
the proinflammatory cytokines (IL 1b, 2, 4, 5, 8, 10, 12p70, and
13, IFN-c, MCP-1, TNF-a) were analyzed utilizing commercially
available multiplexed assays (Meso Scale Discovery, Gaithersburg,
MD, USA) [28,43], and NFL and MBP concentrations were
measured using commercial ELISA kits (NF-Light,
UmanDiagnostics, Umea, Sweden, and ACTIVE MBP, Diagnostic Systems
Laboratories, Webster, TX, USA, respectively). All analyses were
performed according to the manufacturers protocols by
boardcertified laboratory technicians at the Clinical Neurochemistry
Laboratory, Sahlgrenska University Hospital, Molndal. Each set of
biomarker measurements was performed on one day, using one
batch of reagents.
All clinical, immunohistochemical, and laboratory analyses were
performed blinded to the result information of each other.
Nonparametric KruskalWallis H and MannWhitney U tests
were used for comparing CSF levels of measured biomarkers
between different groups, and the Wilcoxon signed-rank test for
comparisons of two related samples. To define the correlation
between different proinflammatory cytokines, Pearson correlation
with Bonferroni correction (k = 55) was applied.
Patients with tauopathy but no amyloid (n = 4) were excluded
from the analyses of different biomarkers in relation to biopsy
findings, and iNPH patients with co-morbid AD (n = 10) and
iNPH patients with negative shunt-response (n = 5) from the
analyses comparing true iNPH patients to non-iNPH patients.
Some cytokines were below the lower limit of detection of the
assays and graded as zero concentration in statistical analyses. One
patient had an insufficient CSF sample for the analysis of sAPPs,
and another for the analysis of Ab isoforms Ab38 and Ab40.
IBM SPSS Statistics for Mac (version 18.104.22.168, IBM, Armonk,
NY, USA) was used in the statistical analyses. The level of
significance was set at p,0.05.
Possible NPH (n = 102)
Final clinical diagnosis of iNPH (n = 53)
Mixed iNPH + AD
No diagnosis of iNPH (n = 39)
Abreviations: CSF, cerebrospinal fluid; Ab42, amyloid beta 142; p-tau 181, tau phosphorylated at threonine 181; sAPP, soluable amyloid precursor protein; IL-8,
interleukin 8; MCP-1, monocyte chemoattractant protein-1; TNF-a, tumor necrosis factor-alpha; NFL, neurofilament light protein; MBP, myelin basic protein.
*Mean (SD) CSF concentrations in ng/L.
Ab and sAPP isoforms
Lumbar CSF levels of sAPPa were significantly lower (p,0.05)
in patients with iNPH and a positive shunt reponse compared to
non-iNPH patients, while sAPPb showed a similar tendency
(p = 0.06, Table 2, Figure 1B and 1D). However, no such
association was seen for sAPP isoforms in ventricular CSF samples
(p = 0.370.47, Table 2, Figure 1A and 1C). In iNPH patients, a
tendency towards lower levels of sAPPa and sAPPb were observed
(p = 0.230.49) in shunt-responders compared to nonresponders in
ventricular and lumbar CSF (Table 2).
Ventricular CSF levels of Ab42 differed (p = 0.003) between
different brain biopsy groups (Table 3, Figure 2C). Patients with
positive Ab and HPt immunoreactivity in the cortical brain biopsy
showed significantly lower CSF levels of Ab42 compared to the Ab
positive and HPt negative group (post hoc p = 0.008), and to the
Ab and HPt negative group (post hoc p = 0.005, Table 3,
Figure 2C). Similar associations were seen in lumbar samples
(data not shown). Quantified Ab load showed a negative
correlation with the levels of CSF Ab42 in ventricular (Pearsons
r = 20.295, p = 0.003) and lumbar (Pearsons r = 20.356, p = 0.01)
samples (Figure 3). However, the CSF levels of other Ab isoforms
(Ab38, Ab40) and sAPP isoforms (sAPPa, sAPPb) did not correlate
(p = 0.590.95) with the presence of Ab or HPt in the biopsy
(Table 3, Figure 2AB and 2DE). Furthermore, there was no
correlation between the levels of sAPP isoforms in the CSF and Ab
load in cortical brain biopsy (p = 0.840.92). There were no
statistically significant differences between the levels of CSF Ab or
tau biomarkers in shunt-responding and nonresponding iNPH
Several cytokines were present at concentrations below the
lower limit of detection of the assay (Table S1). All tested
proinflammatory cytokines showed positive correlations between
each other in ventricular (Table S1) and lumbar (Table S2) CSF
samples. All ventricular and lumbar CSF IL-8 samples and all but
one ventricular CSF MCP-1 sample were above the lower limit of
detection, and the two cytokines and TNF-a were chosen for
further analyses from the proinflammatory cytokines measured.
Lumbar CSF samples showed higher IL-8 levels compared to
ventricular samples (p,0.001). Moreover, lumbar/ventricular
CSF IL-8 ratios (p,0.001) were significantly higher in samples
collected after the ventriculostomy and ICP measurement
compared to those collected before the procedure (Figure 4).
The levels of tested proinflammatory cytokines in the CSF
showed no association to the presence of Ab or HPt in brain
Biomarkers of neuronal damage
There was no significant relation of CSF NFL or MBP levels to
the brain biopsy findings or to the diagnosis of iNPH or AD. In
iNPH, a tendency (p = 0.05) towards lower ventricular CSF NFL
values was seen in shunt-responders (Table 2).
This is the first study to explore Ab and sAPP isoforms,
proinflammatory cytokines, and biomarkers of neuronal damage
in the CSF in conjunction with cortical brain biopsy. The major
finding in the current study was the demonstration of the
independent role of sAPPa in iNPH, which is not explained by
cortical Ab pathology.
In iNPH, decreased levels of sAPP isoforms in lumbar CSF have
been reported in previous studies . As predicted, the level
of lumbar CSF sAPPa was lower, whereas sAPPb showed a similar
trend in patients with shunt-responsive iNPH compared to
noniNPH patients in our patient cohort. Interestingly, in ventricular
samples no association with iNPH was noted, which could be
explained by the ventriculostomy procedure as an invasive sample
collection method or by concentration of proteins in lumbar CSF.
However, the reason for unaffected ventricular levels of sAPP
isoforms are obscure as the ventricular CSF could be expected to
reflect the periventricular metabolism better than lumbar CSF.
The pathobiological role of sAPP isoforms in iNPH seems to be
unconnected to the amyloidogenic pathway as there was no
correlation between sAPP isoform levels in the CSF and Ab load
in the cortical brain biopsy. The reason for the lowering of sAPP
isoform levels in untreated iNPH remains unclear. However, as
the levels are restored upon successful shunt treatment it has been
hypothesized that the lowering may reflect metabolic impairment
in brain tissue affected by iNPH . In any case, our data suggest
that the observed sAPP isoform level changes are independent of
Ab pathology or are so early in the cascade that they do not reflect
current tissue pathology.
As expected, CSF levels of Ab42 showed a negative association
and correlation to Ab load in the brain, as published earlier ,
and as suggested by amyloid-imaging studies . In contrast, no
such association was seen between the CSF levels of Ab38 or Ab40
with positive Ab or HPt immunoreactivity in the cortical brain
biopsy. Our findings support the non-amyloidogenic role of Ab38
and Ab40 in the living human brain.
As predicted, AD patients had lower Ab42 and higher p-tau
levels in the CSF compared to non-AD patients, although the
differences did not reach statistical significance. One explanation
to this is that non-AD patients show similar CSF Ab42 and p-tau
findings as biomarkers of comorbid AD tissue pathology without
clinical dementia of Alzheimers type. As no pathological hallmark
lesions have been identified in iNPH , the role of Ab and tau in
iNPH remain elusive. However, there are patients with mixed
pathologies i.e., patients with AD-related pathology and later
dementia but still initial objective response for shunt surgery .
Interestingly, patients with iNPH + AD had lowest levels of CSF
Ab42, and highest frequency of APOE-e4 carriers. Eighty percent
(8/10) of these patients showed a favourable response to shunt
In contrast to two previous studies [22,23], we found no
prognostic potential in the levels of CSF Ab42 or tau in shunted
iNPH patients. The differences in the results may be explained by
the different sample collection time (most the samples in the
current study were collected after ventriculostomy). It should also
be noted that cited studies included fewer patients.
In iNPH, reports of abnormal levels of proinflammatory
cytokines (IL-1b, IL-4, IL-10, MCP-1, TNF-a) in the CSF has
been published [28,31,32,34], while contradictory findings in
studies comparing proinflammatory cytokines (IL-8, IL-10, IL-12
(p40 and p70), IFN-c, TNF-a, TGF- b1) have also been reported
[28,33,35]. In the current study,we made an attempt to measure a
wide panel of different proinflammatory cytokines from
ventricular and lumbar CSF, and positive correlations between cytokines
were seen. However, we also noted that most of the cytokines are
present in CSF at concentrations that are close to or below the
lower limit of detection of the assay. In fact, these low
concentrations, which are technically challenging to measure,
may explain some of the varying results in the published literature.
Here, we focused on the cytokines that could be robustly
quantified in at least a subset of samples, i.e., IL-8. No association
of proinflammatory cytokines in the CSF with the diagnosis of
iNPH or AD or the presence of Ab or HPt in brain biopsy was
seen. In patients with iNPH, proinflammatory cytokines did not
show prognostic value in shunt surgery. Consequently, our data
suggest the role of neuroinflammation in iNPH and AD to be of
little importance. Instead, an inflammatory response was seen in
lumbar CSF samples collected after the ventriculostomy and ICP
measurement. In addition, increased CSF tau and p-tau levels
were observed in lumbar samples obtained after ventriculostomy
as reported in earlier studies [17,39]. In consequence, levels of
biomarkers in post-ventriculostomy lumbar CSF may not reflect
the true values of the biomarkers in these patients.
Previous studies have reported increased levels of CSF NFL in
NPH [28,3639]. In our cohort, NFL showed higher lumbar CSF
levels in patients with shunt-responsive iNPH compared to
noniNPH patients (Table 2), but not to a significant degree.
Interestingly, iNPH patients with positive shunt response showed a
tendency towards lower NFL levels in ventricular CSF compared
to shunt-nonresponsive iNPH patients. As NFL reflects subcortical
axonal damage, perhaps high NFL could represent more severe
and less recovering injury in the hydrocephalic brain.
The strengths of the current study include: a large NPH cohort
evaluated by cortical brain biopsy, utilization of ventricular and
lumbar CSF samples in the analyses, a wide panel of tested CSF
biomarkers, and evaluation of clinical outcome and other
dementing disorders in the follow-up. The limitations of this study
included: a limited number of patients with no shunt response,
systematic assessment of shunt response only at 23 months,
dichotomised shunt response scale, lack of validated objective
outcome measures, and lumbar CSF sample available only in half
of the cases. It is obvious that at least in prospective research
setting shunted patients should be followed-up for a significantly
longer time, and validated outcome measures should be utilized.
Five patients with diagnostic findings suggesting iNPH did not
respond to shunt possibly due to comorbidities or misdiagnosis,
and thus these patients were excluded from the comparisons of
(true) iNPH patients and non-iNPH patients in addition to the
iNPH patients who were diagnosed with comorbid AD in the
More basic science and clinical studies evaluating the biology
and potential role as diagnostic and prognostic biomarker of
sAPPa and b are needed in the future.
To conclude, the role of sAPP isoforms in iNPH seems to be
unconnected to the Ab cascade pathway, but rather may be
explained by a metabolic failure or ischemia in the brain. No
elevations in the levels of proinflammatory cytokines in the CSF
were observed in the different diagnostic groups. Consequently,
neuroinflammation in iNPH and AD require further study. None
of the tested CSF biomarkes showed a potency to discriminate
between iNPH and non-iNPH patients or shunt-responders and
nonresponders in iNPH in clinical setting.
The authors wish to acknowledge Marita Voutilanen, RN, for
maintenance of the Kuopio NPH Registry.
Conceived and designed the experiments: IA HS JEJ MH VL. Performed
the experiments: OTP ML JR ON TTS S-KH AMK IA LP SS HZ VL.
Analyzed the data: OTP ML JR ON TTS S-KH AMK IA LP MH VL.
Contributed reagents/materials/analysis tools: IA HS JEJ MH HZ VL.
Wrote the paper: OTP VL. Critical revision of the manuscript for
important intellectual content: OTP ML JR ON TTS S-KH AMK IA LP
SS HS JEJ MH HZ VL. Statistical analysis: OTP ML VL. Obtained
funding: HS MH HZ VL. Study supervision: HS MH VL.
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