370
Copyright
©
2017 The Korean Society of Radiology
Longitudinal Intrinsic Brain Activity Changes
in Cirrhotic Patients before and One Month after
Liver Transplantation
Yue Cheng, MD, PhD
1
, Li-Xiang Huang, MD
1
, Li Zhang, MD
2
, Ming Ma, MD
2
, Shuang-Shuang Xie, MD
1
,
Qian Ji, MD, PhD
1
, Xiao-Dong Zhang, MD, PhD
1
, Gao-Yan Zhang, MD, PhD
3
, Xue-Ning Zhang, MD, PhD
4
,
Hong-Yan Ni, MD, PhD
1
, Wen Shen, MD, PhD
1
Departments of
1
Radiology and
2
Transplantation Surgery, Tianjin First Central Hospital, Tianjin 300192, China;
3
School of Computer Science and
Technology, Tianjin Key Laboratory of Cognitive Computing and Application, Tianjin University, Tianjin 300072, China;
4
Department of Radiology,
The Second Hospital of Tianjin Medical University, Tianjin 300211, China
Objective: To evaluate the spontaneous brain activity alterations in liver transplantation (LT) recipients using resting-state
functional MRI.
Materials and Methods: Twenty cirrhotic patients as transplant candidates and 25 healthy controls (HCs) were included in
this study. All patients repeated the MRI study one month after LT. Amplitude of low-frequency fluctuation (ALFF) values
were compared between cirrhotic patients (both pre- and post-LT) and HCs as well as between the pre- and post-LT groups.
The relationship between ALFF changes and venous blood ammonia levels and neuropsychological tests were investigated
using Pearson’s correlation analysis.
Results: In the cirrhotic patients, decreased ALFF in the vision-related regions (left lingual gyrus and calcarine),
sensorimotor-related regions (left postcentral gyrus and middle cingulate cortex), and the default-mode network (bilateral
precuneus and left inferior parietal lobule) were restored, and the increased ALFF in the temporal and frontal lobe improved
in the early period after LT. The ALFF decreases persisted in the right supplementary motor area, inferior parietal lobule,
and calcarine. The ALFF changes in the right precuneus were negatively correlated with changes in number connection
test-A scores (r = 0.507, p < 0.05).
Conclusion: LT improved spontaneous brain activity and the results for associated cognition tests. However, decreased ALFF
in some areas persisted, and new-onset abnormal ALFF were possible, indicating that complete cognitive function recovery
may need more time.
Keywords: Liver transplantation; Cirrhosis; Hepatic encephalopathy; Resting state; Functional magnetic resonance imaging;
Amplitude of low-frequency fluctuation; Brain activity change
Received April 11, 2016; accepted after revision October 8, 2016.
This work was supported by National Natural Science Foundation of China (No. 81601482 to Y. C. and No. 61503278 to G. Y. Z)
Corresponding author: Wen Shen, MD, PhD, Department of Radiology, Tianjin First Central Hospital, No. 24 Fu Kang Road, Nan Kai
District, Tianjin 300192, China.
• Tel: (86) 15900209418 • Fax: (86) 22 23361365 • E-mail: shenwen66happy@163.com
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://
creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium,
provided the original work is properly cited.
Korean J Radiol 2017;18(2):370-377
https://doi.org/10.3348/kjr.2017.18.2.370
pISSN 1229-6929 · eISSN 2005-8330
Original Article
|
Neuroimaging and Head & Neck
INTRODUCTION
Hepatic encephalopathy (HE), one of the serious
complications in patients with end-stage liver cirrhosis, is
caused by accumulation in the bloodstream of ammonia
and other endogenous substances deriving from hepatic
metabolism. The spectrum of the syndrome ranges
from psychometric performance alterations (minimal
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MATERIALS AND METHODS
Subjects
We recruited a consecutive series of cirrhotic patients
who were scheduled for LT from December 2013 to October
2015. The diagnosis of liver cirrhosis was made by clinical
history and imaging (abdominal computed tomography and
ultrasound findings). We excluded subjects if they had: 1)
history of drug abuse; 2) psychiatric or neurologic illness; 3)
any serious complications after LT such as rejection, severe
biliary stenosis, liver failure, or any central nerve system
complications; or 4) poor image quality with a head motion
more than 2.0 mm/degree. In all, we ultimately included
20 cirrhotic patients (13 men and 7 women; mean age:
51.9 ± 6.9 years) who received successful LT operations in
our hospital. Among them, 13 patients had been previously
included in another prospective study of ours that was
already published (17). All patients underwent MRI scan
both before and one month after LT. The etiologies of the
liver cirrhosis included type C hepatitis, type B hepatitis,
cryptogenic cirrhosis, and primary biliary cirrhosis (n = 8,
7, 3, 2 for each). All patients received laboratory tests,
including prothrombin time and total bilirubin, albumin,
and venous blood ammonia values, within one week before
the MRI scans; we also used Child-Pugh classification to
grade hepatic function. We recruited 25 healthy controls
(HCs; 18 men and 7 women; mean age: 49.6 ± 8.3 years)
who were frequency matched in age, gender, and education
using advertisements within our hospital. The control
subjects had no history of neurologic, psychiatric, or
traumatic diseases that could have affected brain function.
All controls also had no liver or other systemic diseases.
This study was approved by the Ethics Committee
of Tianjin First Central Hospital, and we conducted all
experiments in compliance with relevant guidelines and
regulations. All participants provided written informed
consent prior to the study.
Cognitive Assessment
The psychometric test battery comprised the number
connection test-A (NCT-A) and digit-symbol test (DST) (19),
which we used to evaluate the cognitive impairment in
cirrhotic patients; we performed these tests for all subjects
just before their MRI scans. The NCT-A tests psychomotor
function, whereas the DST tests attention and processing
speed. Lower scores are considered to reflect poor cognitive
abilities (1). Cirrhotic patients were diagnosed as MHE if
hepatic encephalopathy [MHE]) to stupor and coma (1).
Evidence has shown that neurocognitive dysfunction in
cirrhotic patients is associated with deterioration in daily
functioning, poorer quality of life, and mortality (2). Liver
transplantation (LT) is an effective treatment that can
improve life quality and prolong survival (3); impaired
cognitive function can also be greatly corrected after LT (4-
6). However, the mechanisms underlying the neurological
changes in patients who undergo LT remain largely unclear.
By understanding this, better therapeutic methods for
cirrhosis-related cognitive dysfunctions may be developed.
Recently, resting-state functional MRI (rs-fMRI) plays an
important role in investigating the neural mechanisms of
various mental disorders (7-9). This approach is relatively
economical and easy to implement in clinical studies, and it
can also overcome potential limitations in task-based fMRI
studies (10). In recent years, some groups have studied the
changes in cerebral activity in cirrhotic patients using rs-
fMRI (11-15). These studies indicated that the impairments
and reorganization of brain function are dynamic processes
and that these changes can both exist in every stage of HE
from simple cirrhosis (without HE) to MHE and, ultimately,
overt HE. Using resting-state functional connectivity, Lin
et al. (16) found dynamic disruptions and reconstruction
of intrinsic large-scale networks approximately one year
after LT accompanied by cognitive deficits and recovery.
Moreover, Zhang et al. (17) found improved long- and
short-range functional connectivity density one month after
LT and persistence of posterior cingulate cortex/precuneus
(PCu) functional connectivity disturbance. However, these
functional connectivity studies reveal the abnormal brain
connections only between two remote regions, not from the
perspective of local brain activity. Although aberrant brain
connectivity between the two remote regions is integrative
and comprehensive, no definite conclusion can be reached
about which one is abnormal (8).
To overcome these limitations, amplitude of low-frequency
fluctuation (ALFF) (18), a newly developed approach to
quantitatively measure the amplitude of spontaneous
brain activity, is recommended. This method can provide
us with regional spontaneous brain activity information,
which is important for completely understanding a disease.
Thus, the goals of this study were to 1) assess local brain
activity alterations after LT using ALFF and 2) examine the
relationship between ALFF alterations and the changes in
the neuropsychological test scores following LT.
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they showed no symptoms of overt encephalopathy but their
scores were abnormal on at least one neuropsychological
test (beyond 2 standard deviations of the mean value for
the HCs; 19).
MRI Data Acquisition
We acquired the MRI data using a clinical 3 Tesla whole
body MR imager (TIM-Trio; Siemens Medical Solutions,
Erlangen, Germany) with a 32-channel head coil; the head
coil was fitted with foam padding and headphones to
minimize head motion and reduce scanner noise. During
scanning, each subject was asked to hold the head still,
relax with eyes closed, and not to think of anything in
particular. rs-fMRI images were obtained using a rapid
gradient echo-planar sequence (200 volumes; repetition
time = 2500 ms; echo time = 30 ms; field of view = 220
x 220 mm
2
; flip angle = 90°; section thickness = 3 mm;
acquisition matrix = 96 x 96; a total of 40 slices covering
the whole brain).
Data Preprocessing
We conducted functional imaging data analysis using the
Data Processing Assistant for Resting-State fMRI software
(http://www.restfmri.net/forum/DPARSF) toolbox. Briefly,
we discarded the first 10 time points for each subject due
to the signal stabilization and subject adaptation to the
scanning noise. The remaining 190 time points were left
for correcting the acquisition delays between slices and the
head motion. We excluded data from subjects with head
motion of more than 2.0 mm translation in any direction
and more than 2.0° rotation in each axis.
Subsequently, we spatially normalized the realigned
images according to the standard Montreal Neurological
Institute template and resampled them into a voxel size of
3 x 3 x 3mm
3
. After this, we performed spatial smoothing
by means of convolution with a Gaussian kernel of 4 mm.
ALFF Calculation
Before we calculated ALFF, in order to reduce the effects
of very-low-frequency drift and very-high-frequency noises,
we removed the linear trends and performed temporal
filtering (band-pass, 0.01–0.08 Hz). Then, using a fast
Fourier transformation, we converted the time course for
each voxel into the frequency domain. Then, each frequency
of the power spectrum was square root transformed and
averaged across 0.01–0.08 Hz, and we took the averaged
square root as the ALFF measurement. For standardization
purposes, we divided the ALFF of each given voxel by the
global mean ALFF of the whole brain.
Statistics Analysis
We used SPSS (version 17.0; SPSS Inc., Chicago, IL,
USA) to analyze the demographic data and SPM8 for the
rs-fMRI data. We conducted two-sample t tests to assess
the differences in age, education level, and clinical scores.
We also used two-tailed chi-square tests examine the
differences by gender between the patients and the HCs.
We also performed paired t tests to evaluate the changes
in clinical scores after LT, second-level random-effect two-
sample t tests to characterize the ALFF differences between
the cirrhotic patients (pre- and post-LT) and HCs, and paired
t tests to compare the differences between pre- and post-LT
patients. We considered age, sex, and education years as no-
interest covariates, and corrected the results using AlphaSim
(http://afni.nimh.nih.gov/pub/dist/doc/manual/AlphaSim.
pdf); an overall false positive p < 0.05 was achieved by
combining an individual voxel threshold of p < 0.01 and a
minimum cluster volume threshold of 729 mm
3
.
Furthermore, we selected the regions that showed
significantly altered ALFF in pre- and post-LT comparisons
as a mask and extracted the mean ALFFs for each patient
in these masks. We calculated the ΔALFF, Δammonia, and
ΔNCT-A/ΔDST, which reflected the changes in ALFF and the
ammonia and neuropsychological tests before and after
LT. Subsequently, we used Pearson’s correlation analysis to
study the relationship between ΔALFF in these brain regions
and Δammonia or ΔNCT-A/ΔDST. The statistical threshold
for significant difference was p < 0.05 for these analyses.
RESULTS
Demographics and Clinical Data
The demographic and clinical data of the cirrhotic patients
and HCs are shown in Table 1. There were no significant
differences in the data including age, gender, and education
years between the cirrhotic patients and HCs (all p >
0.05). The Child-Pugh classifications revealed 17 patients
as class C and 3 patients as class B. Thirteen patients had
histories of overt HE episodes, 5 patients with abnormal
neuropsychological results were diagnosed as MHE, and the
remaining 2 patients with normal neuropsychological results
were diagnosed as non-HE.
The cirrhotic patients performed worse on cognitive
tests than did the HCs before LT (p < 0.01). They needed
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more time for the NCT-A and got lower DST scores. After
LT, both the NCT-A and DST performances improved (p <
0.01), although they were still worse the HCs’ scores (p <
0.05). The prothrombin time and albumin, total bilirubin,
and venous ammonia concentrations of the pre-LT patients
were abnormal. After LT, all the test indexes improved
significantly (All p < 0.005).
Group Differences in ALFF
The ALFF differences between pre- and post-LT group
and the HCs and between the post- and pre-LT groups are
displayed in Tables 2-4 and Figures 1-3. Compared with the
HCs, the pre-LT patients showed significantly decreased
ALFF in the bilateral calcarine, inferior parietal lobe (IPL),
PCu, left lingual gyrus, postcentral gyrus (PoCG), middle
cingulate cortex, and right supplementary motor area (SMA)
and increased ALFF in the bilateral lateral temporal cortex,
parahippocampal gyrus (PHG), right hippocampus (Hip), and
superior frontal gyrus (SFG). The post-LT patients displayed
ALFF decreases in the right IPL, calcarine, and SMA and
increases in the right SFG, inferior frontal gyrus (IFG), left
PHG, and left middle frontal gyrus (MFG). Interestingly,
Table 1. Demographics and Clinical Data of Pre- and Post-LT Groups and HCs
Parameter HCs (n = 25) Pre-LT (n = 20) Post-LT (n = 20)
P
Pre-LT/HCs Post-LT/HCs Post-/Pre-LT
Sex (M/F) 18/7 13/7 13/7 0.614* 0.614* -
Age (years)
49.6 ± 8.3 51.9 ± 6.9
51.9 ± 6.9 0.316
†
0.316
†
-
Education (years) 12.6 ± 3.0 12.1 ± 4.1 12.1 ± 4.1 0.642
†
0.642
†
-
NCT-A (seconds) 44.1 ± 10.8 78.6 ± 33.8 59.2 ± 30.8 0.000
†
0.028
†
0.000
‡
DST (score) 48.6 ± 10.4 27.8 ± 12.8 35.0 ± 14.0 0.000
†
0.001
†
0.000
‡
Biochemical parameters
Prothrombin time (seconds) - 17.9 ± 4.3 12.1 ± 2.6 - - 0.000
‡
Albumin (mg/dL) - 29.6 ± 6.2 38.0 ± 5.8 - - 0.000
‡
Total bilirubin (mg/dL) - 68.6 ± 54.9 21.7 ± 13.2 - - 0.001
‡
Venous ammonia (μmol/L)
- 71.6 ± 29.2
42.2 ± 13.8
- -
0.000
‡
Child-Pugh B/C
- 3/17 - - - -
No-HE/MHE/HE - 2/5/13 - - - -
*Chi-square test,
†
Two-sample t test,
‡
Paired two-sample t test. DST = digit-symbol test, HCs = healthy controls, HE = hepatic
encephalopathy, LT = liver transplantation, MHE = minimal hepatic encephalopathy, NCT-A = number connection test-A
Table 2. Differences of ALFF between Pre-LT Patients and HCs
Brain Regions Brodmann’s Area MNI Coordinates Cluster Size Peak t Value
Left LG 19 -15, -45, -9 28 -3.74
Right calcarine 18 24, -60, 18 77 -3.65
Left calcarine 18 -18, -60, 12 53 -4.04
Left PoCG 2/3 -63, -15, 12 82 -4.90
Right PCu 7 12, -76, 44 48 -4.21
Left PCu 7 -6, -66, 48 334 -5.93
Right MCC 24 3, 21, 30 73 -4.53
Right IPL 40 48, -48, 54 124 -4.30
Left IPL 40 -45, -45, 51 108 -4.20
Right SMA 6 -3, 12, 51 201 -4.75
Right LTC 21/22 46, 11, -25 215 5.79
Left LTC 21/22 -45, 0, -24 218 5.51
Right Hip 20 25, -4, -18 47 3.78
Right PHG 36 30, -6, -36 28 3.29
Left PHG 36 -21, -6, -30 86 4.69
Right SFG 10 15, 60, 3 27 3.61
p<0.05, AlphaSim corrected. Negative t value represents decrease, and positive t value represents increase. ALFF = amplitude of
low-frequency fluctuation, HCs = healthy controls, Hip = hippocampus, IPL = inferior parietal lobule, LG = lingual gyrus, LT = liver
transplantation, LTC = lateral temporal cortex, MCC = middle cingulate cortex, MNI = Montreal Neurological Institute, PCu = precuneus,
PHG = parahippocampal gyrus, PoCG = postcentral gyrus, SFG = superior frontal gyrus, SMA = supplementary motor area
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compared with the pre-LT group, the post-LT patients
demonstrated significant ALFF increases in the left IPL and
right Pcu and ALFF decreases in the bilateral middle temporal
gyrus, right precentral gyrus (PreCG), and Hip (Fig. 4).
Figure 5 illustrates the Pearson’s correlation analysis
results between the clinical data and the brain regions with
altered ALFF, which revealed negative correlations between
ΔALFF in the right PCu and ΔNCT-A (r = 0.507, p < 0.05).
There were no correlations between ΔALFF and ΔDST or
Δammonia (p > 0.05).
DISCUSSION
In this rs-fMRI study, we found that most of the brain
regions with altered ALFF were restored one month after
LT, whereas the reduced ALFF in some regions such as the
right SMA, IPL, and calcarine persisted one month after
LT. Furthermore, there were new-onset ALFF decreases in
the right PreCG and increases in the left MFG and right IFG
one month after LT. These findings suggest that partial
renormalization of spontaneous brain activity and complete
cognitive function recovery may need more time. The ALFF
had practical value in detecting the brain changes after LT.
Although the exact biologic mechanisms of ALFF are still
unclear, many studies have suggested that altered ALFF is
associated with abnormal regional neuronal activity (13,
20). Many fMRI algorithms have been developed such as
independent component analysis, seed correlation analysis,
and regional homogeneity (14, 18, 21). Different analysis
methods can reflect different aspects of integrated human
brain function; compared with other methods, the strength
of ALFF lies in its directly reflecting the amplitude of
spontaneous brain activity (13). ALFF has been used widely
in studies of neuropsychological diseases including HE
(13, 22, 23). In the present study, abnormal ALFF in pre-
LT patients indicated neural function impairment in specific
brain areas, consistent with previous studies (22, 23). In
addition, ALFF algorithms have also been used in detecting
the brain functional alterations of cirrhotic patients after
treatment, such as transjugular intrahepatic portosystemic
shunt (24). Thus, ALFF is potentially valuable for uncovering
the mechanism of how transplantation affects the brain
function in the early postoperative period.
Our study found that one month after LT, most of the
brain regions with decreased ALFF before LT had reversed.
The lingual gyrus and calcarine, the key components of
the visual cortex, are the vision center in the human
brain. These areas play important roles in visual attention,
visual discrimination, and color perception (25). As the
region of the primary somatosensory cortex, the PoCG
Table 3. Differences of ALFF between Post-LT Patients and HCs
Brain Regions Brodmann’s Area MNI Coordinates Cluster Size Peak t Value
Right calcarine 18 24, -60, 18 27 -3.41
Right IPL 40 48, -51, 54 30 -3.74
Right SMA 6 3, -18, 60 56 -3.51
Left PHG 36 -18, 0, -33 28 3.95
Left MFG 10/46 -42, 42, 18 33 4.39
Right SFG 10 18, 57, 0 72 3.70
Right IFG 9 51, 33, 6 37 3.86
p < 0.05, AlphaSim corrected. Negative t value represents decrease, and positive t value represents increase. ALFF = amplitude of low-
frequency fluctuation, HCs = healthy controls, IFG = inferior frontal gyrus, IPL = inferior parietal lobule, LT = liver transplantation,
MFG = middle frontal gyrus, MNI = Montreal Neurological Institute, PHG = parahippocampal gyrus, SFG = superior frontal gyrus, SMA =
supplementary motor area
Table 4. Differences of ALFF between Post- and Pre-LT Patients
Brain Regions Brodmann’s Area MNI Coordinates Cluster Size Peak t Value
Right MTG 21 56, 2, -25 66 -4,85
Left MTG 21 -60, -15, -21 73 -4.75
Right Hip 20 33, -6, -18 46 -5.66
Right PreCG 4 30, -18, 51 45 -4.98
Left IPL 40 -45, -45, 48 28 4.61
Right PCu 7 12, -72, 45 30 4.15
p < 0.05, AlphaSim corrected. Negative t value represents decrease, and positive t value represents increase. ALFF = amplitude of low-
frequency fluctuation, Hip = hippocampus, IPL = inferior parietal lobule, LT = liver transplantation, MNI = Montreal Neurological Institute,
MTG = middle temporal gyrus, PCu = precuneus, PreCG = precentral gyrus