Keywords:
Pathology, Comparative studies, MR, Neuroradiology brain, Head and neck, CNS
Authors:
S. Kitao1, E. Matsusue2, S. Fujii1, F. Miyoshi1, T. Kaminou1, T. Ogawa1; 1Yonago/JP, 2Tottori/JP
DOI:
10.1594/ecr2013/C-1246
Purpose
Introduction
Neuromelanin is a by-product of the synthesis of monoamine neurotransmitters such as noradrenalin and dopamine,
and is mainly expressed in neurons of the locus coeruleus (LC) and substantia nigra pars compacta (SNc) [1-3].
Neuromelanin can induce paramagnetic T1-shortening effects when combined with metals such as iron and copper [4,
5].
T1-weighted imaging has failed to depict neuromelanin-generated contrast,
presumably because of the negligible T1 difference between neuromelanin and brain tissue.
Sasaki et al.
reported neuromelanin-related contrast in the SNc and LC using a multi-slice 2-dimensional fast-spin-echo T1-weighted sequence with 3T MR imaging,
where both the high signal-to-noise ratio and prolonged T1 relaxation time of the brain functioned synergistically to enhance the visualization of neuromelanin-related contrast [6].
Nakane et al.
[7] identified neuromelanin-generated contrast in the SNc and LC,
even at 1.5 T,
using a 3D-gradient echo T1-weighted sequence with magnetization transfer contrast pulses,
which suppress brain background signals to enhance the contrast between brain background and neuromelanin.
Parkinson’s disease (PD) is characterized by severe loss of dopaminergic neurons and neuromelanin.
Pathologically,
dementia with Lewy bodies (DLB) closely resembles PD.
Patients with DLB are characterized by the diffuse presence of Lewy bodies,
cytoplasmic inclusions composed principally of alpha-synuclein,
in both subcortical and cortical areas of the brain,
whereas PD patients have Lewy bodies in the subcortical areas of the brain,
mainly the SNc and LC [8,
9].
Sasaki et al.
[6] demonstrated diminished neuromelanin levels in the SNc and LC in PD using 3T MR neuromelanin-contrast imaging.
In addition,
Schwarz et al.
[10] suggested that T1 hyperintense area in the SNc was substantially smaller in patients with late stage PD than those with early stage PD using 3T MR neuromelanin-contrast imaging.
On neuromelanin-contrast imaging,
paramagnetic T1-shortening effects of neuromelanin-containing neurons are considered to be closely related to the high signal intensity of the SNc.
In addition,
the iron content of the SNc is very high,
approximately 20 mg/100 mg tissue,
and it increases with age [11,
12].
Therefore,
the possibility that a high iron concentration in the SNc may cause T1-shortening effects has been suggested in neuromelanin-contrast imaging [6].
In this study,
we performed direct correlation between postmortem neuromelanin MR imaging (NmMRI) and neuropathological findings and clarified the pathological background of the signal change in normal,
DLB,
and PD cases.
In addition,
to examine the participation of iron deposition,
we also evaluated the extent of iron deposition using immunohistochemistry for ferritin,
which is the main storage form of iron in the brain.