Xue-wei Zhang1,2, Wei-hong Zhang2, and Qin Long3
1Department of Interventional Radiology, China Meitan General Hospital, Beijing, China, People's Republic of, 2Department of Radiology, Peking Union Medical College Hospital, Beijing, China, People's Republic of, 3Department of Ophthalmology, Peking Union Medical College Hospital, Beijing, China, People's Republic of
Synopsis
High myopia (HM) can
result in serious vision problems. To date, the pathophysiologic mechanism remains
unknown. The authors tried to explore the potential locations which involved in
the brain abnormalities of HM patients, through observing altered ALFF of
different bands and functional connectivity of the brain by rs-fMRI. The
results showed that, not only visual cortex but also multiple brain regions were
noted to have abnormal changes in the brain of HM patients. In conclusion, the
findings indicated that high myopia affects many functional networks, and
different bands of ALFF may provide a new way to explore the underlying mechanism.introduction
High myopia (HM), sometimes known as pathological myopia or degenerative
myopia, is a type of refractive error
above -6 diopter (D),which can result in visual impairment and even blindness [1]. Till now, the mechanism
of HM has not been clarified yet. Most of the magnetic resonance（MR） studies related with high
myopia are concentrated on the structural changes of the eyeball and the brain[2]. However, only few
studies addressed the changes of the brain activity in people with HM. Resting-state
functional magnetic resonance imaging (rs-fMRI) is appropriate for exploring
the mechanism of HM. Technically, amplitude of low-frequency fluctuations
(ALFF) and fractional ALFF (fALFF) are two common indexes which have been
proven to be valuable parameters to reflect spontaneous neural activity. Previous
researches have demonstrated that fALFF could improve sensitivity and
specificity in detecting abnormal brain activities [3], and detailed information
about the brain can be acquired through analyzing the different frequency bands
[4]. In addition, functional
connectivity can provide clues of the observed temporal correlations between
remote areas and it has the potential application to clarify the rearrangement
of the
networks[5]. Herein, we hypothesized
that the abnormalities in the brain of HM patients exist not only in the visual
cortex but also in some other functional networks.
Purpose
To analyze the altered amplitude of
low-frequency fluctuation (ALFF) and functional connectivity of the brain using
resting-state functional magnetic resonance imaging (fMRI) in HM patients.
Methods
and Materials
Four patients with high myopia (above-10D in both eyes) and ten age- and
gender-matched healthy controls were recruited. After the ALFF and fractional
amplitude of low-frequency fluctuation (fALFF) for slow-4(0.027-0.73 Hz) and
slow-5 (0.01-0.027 Hz) bands were calculated, the results between patients and
healthy controls were compared. The functional connectivity (FC) between
regions of interest (ROIs) based on ALFF findings with the voxels in the whole brain
were then calculated.
Results
1.Altered
ALFF results of one-sample t-test across all subjects of the two groups during
resting state are showed in Figure 1 (P < 0.05, AlphaSim correction).
2. Compared with healthy subjects, HM
patients showed significant increased ALFF in the right inferior occipital
gyrus, left lingual gyrus and Broadman area 18 (Showed in Fig.2).
3. Two ROIs’ spheres were drawn by peak
points based on altered areas of ALFF (The Montreal Neurological Institute (MNI)
coordinates of peak points were showed in Fig.2). Compared with healthy
controls, HM patients showed decreased functional connectivity of ROI1 in the
left inferior occipital gyrus and left medial superior frontal gyrus. For the
ROI 2, decreased functional connectivity of HM patients were left cuneus but
increased functional connectivity in right inferior temporal gyrus (Showed in Fig.3).
4. The alterations of fractional ALFF
for slow4 and slow5 bands: Compared with healthy subjects, HM patients showed
significant increased fALFF in the right postcentral gyrus and precentral gyrus
but decreased fALFF in right calcarine cotex, cuneus,
Broadman area 18, left anterior cingulum and Broadman area 10 for slow-4. Meanwhile,
HM patients showed significant increased fALFF in left superior frontal gyrus
but decreased fALFF in left precentral gyrus, Broadman area 6 and middle
frontal gyrus for slow-5. (Showed in Fig.4)
Conclusion
Our findings indicated that high myopia
not only affect visual
cortex but also some other functional networks. In addition, frequency effects
should be taken into account as a combination of the different bands can
acquire more information about the brain.
Acknowledgements
The
author thanks Wei-Hong Zhang, in the Department of Radiology and Qin Long, in the
Department of ophthalmology, Peking Union Medical College Hospital for their
valuable help on the manuscript.References
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