Feb 21, 2018 - Hans-Jonas Meyer1. | Alexander ... Hans-Jonas Meyer, Department of ..... ing these phenomena are still unclear (Stålberg & Karlsson, 2001).
|
|
Received: 1 August 2017 Revised: 5 February 2018 Accepted: 21 February 2018 DOI: 10.1002/brb3.958
ORIGINAL RESEARCH
Associations between apparent diffusion coefficient and electromyography parameters in myositis—A preliminary study Hans-Jonas Meyer1
| Alexander Emmer2 | Malte Kornhuber2 | Alexey Surov1
1 Department of Diagnostic and Interventional Radiology, University of Leipzig, Leipzig, Germany 2
Abstract Objective: MRI is widely used in several muscle disorders. Diffusion-weighted imag-
Department of Neurology, Martin-Luther University Halle-Wittenberg, Halle, Germany
ing (DWI) is an emergent imaging modality sensitive to microstructural alterations in
Correspondence Hans-Jonas Meyer, Department of Diagnostic and Interventional Radiology, University of Leipzig, Leipzig, Germany. Email: Hans-Jonas.Meyer@medizin. unileipzig.de
tion of water molecules. Electromyography (EMG) is a clinically used diagnostic tool
tissue. The apparent diffusion coefficient (ADC) is used to quantify the random moin myositis. The aim of this study was to elucidate possible associations between ADC values and EMG findings in myositis patients. Method: Seven patients (eight investigated muscles) with myositis (mean age 51.43 ± 19 years) were included in this study. The diagnosis was confirmed by histopathology in every case. DWI was obtained with a 1.5-T scanner using two b-values 0 and 1000 s/mm². In all patients, a needle electromyography (EMG) was performed within 3 days to the MRI. The following EMG parameters were studied: motor unit action potential (MUAP) amplitudes and durations, as well as pathological spontaneous activity. Spearman’s correlation coefficient was used to analyze associations between investigated parameters. Results: The estimated mean ADCmean value was 1.51 ± 0.29 × 10−3 mm²/s, mean
ADCmin was 1.28 ± 0.27 × 10−3 mm²/s, and mean ADCmax was 1.73 ± 0.28 × 10−3 mm²/s.
Correlation analysis identified significant associations between ADCmean and duration of the MUAP (p = .78 P = .0279) and between ADCmin and duration of the MUAP (p = .85, P = .01). There were no significant differences according to pathological spontaneous activity. Conclusion: ADCmean and ADCmin showed strong positive correlations with the duration of the MUAP in myositis patients. Both modalities might similarly reflect muscle fiber loss in myositis patients. KEYWORDS
apparent diffusion coefficient, diffusion-weighted imaging, electromyography, myopathy, myositis
1 | I NTRO D U C TI O N
polymyositis, dermatomyositis, inclusion body myositis, necrotizing autoimmune myositis, and overlap myositis (Dalakas, 2015).
Autoimmune myositis is a heterogeneous group of disorders of
The diagnostic approach is multimodal consisting of anamnes-
unknown etiology and can be classified into the following entities:
tic features, clinical examination, serological parameters, needle
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2018 The Authors. Brain and Behavior published by Wiley Periodicals, Inc. Brain and Behavior. 2018;e00958. https://doi.org/10.1002/brb3.958
wileyonlinelibrary.com/journal/brb3 | 1 of 6
|
MEYER et al.
2 of 6
TA B L E 1 Overview about the patient collective included in this study Diagnosis
n
%
Polymyositis
3
42.86
Overlap myositis
3
42.86
Inclusion body myositis
1
14.29
All
7
100
2.1 | Patients One hundred and six patients with different muscle disorders were investigated by MRI in our department. Patients were included in this study if they fulfilled the following inclusion criteria: • if they had a muscle disorder (myositis) confirmed by histopathology; • MRI was performed with DWI; • Diseased muscles did not show artifacts on DWI, as signal voids,
electromyographic findings, and muscle biopsy (Dalakas, 2015). The magnetic resonance imaging (MRI) has been evaluated to be the most important imaging modality in these patients due to its
movement artifacts, and susceptibility artifacts • EMG was performed within 3 days to the MRI and the video EMG recordings were available
excellent soft tissue contrast (Leung, 2017; O’Connell et al., 2002). Thus, it is clinically used to detect atrophy of affected muscles,
Cases that did not meet the inclusion criteria were excluded from
muscle edema, and/or myofasciitis (Dalakas, 2015; O’Connell
the study. Also, patients with traumatic muscle injury, steroid-induced
et al., 2002).
myopathy, muscle abscesses, and muscles struck by ischemia or ve-
Recently, diffusion-weighted imaging (DWI) has been evaluated to be a useful imaging tool in several muscle disorders such as tumors, inflammation, and myopathies (Partovi et al., 2015; Qi, Olsen,
nous thrombosis were excluded. Altogether, seven patients (four women, 57.14%) were included in this study (Table 1).
Price, Winston, & Park, 2008; Ran et al., 2016; Surov & Behrmann, 2014; Surov et al., 2015). Additionally, it can be quantified with the apparent diffusion coefficient (ADC) reflecting the random water motion in tissue (Surov, Meyer, & Wienke, 2017).
2.2 | MRI In all cases, MRI of the thigh and lower leg was performed using
Another important diagnostic modality is needle electromy-
a 1.5- T scanner (Magnetom Vision Sonata Upgrade, Siemens,
ography (EMG), which is widely used in clinical routine (Dalakas,
Germany). MRI sequences included turbo spin-echo (TSE) images,
2015). A fine needle electrode is inserted into the muscle. Then,
T2- weighted (T2W) fat- suppressed short tau inversion recovery
a signature electrical signal is generated by the motor units (MU)
(STIR) images, half-Fourier acquisition single-shot turbo spin-echo
displaying extracellular potential differences in muscle cells be-
(HASTE) images, T1-weighted (T1W) spin-echo (SE) images prior and
longing to the same alpha motor neuron. Furthermore, the MU
after intravenous administration of contrast medium.
action potential (MUAP) is brought about by voluntary muscle
Diffusion-weighted images were obtained with a multishot SE-
contraction. In certain pathological conditions, unprovoked regu-
EPI (echo planar imaging) sequence with b-values, 0, and 1000 s/
lar signals generated by individual muscle fibers can be assessed as
mm². Motion-probing gradient pulses were placed in the three or-
pathological spontaneous activity (SA) (Apartis, 2013). Clinically,
thogonal planes, and isotropic DW imaging was generated by three
EMG is mostly used to rule out possible differential diagnoses
orthogonal axes. Sequence parameters were as follows: TR/TE:
like neurogenic disorders and to assess disease activity in myo-
5800/68 ms; flip angle: 90°, thickness: 5 mm; matrix size: 128; band-
sitis patients (Dalakas, 2015). Typically, MUAPs become small in
width: 2.3 kHz; Imaging Frequency: 63.685; number of averages: 2.
amplitude, short in duration, and polyphasic. Furthermore, muscle fiber degeneration is accompanied by pathological spontaneous activity.
2.3 | ADC measurement
It is yet unclear whether electrodiagnostic information about ex-
ADC maps were automatically generated by the implemented soft-
tracellular potential differences provided by EMG is associated with
ware. In all cases, polygonal regions of interest (ROI) were manually
the random water motion in muscles measured by DWI. Presumably,
drawn on the ADC maps along the contours of the affected mus-
both modalities might be able to assess disease activity in a similar
cles on each slice (whole muscle measure). A minimum ADC value
fashion.
(ADCmin), a mean ADC value (ADCmean), and a maximum ADC value
Therefore, the purpose of this study was to elucidate possible
(ADCmax) were estimated of every muscle.
associations between DWI and EMG in myositis patients.
2.4 | Electromyography 2 | M ATE R I A L S A N D M E TH O DS
The EMG was recorded by M.K. using a concentric needle electrode (37 mm, 26G, CareFusion, USA) and by a Multiliner Vision
This retrospective study was approved by the institutional ethic
(Viasys, Höchberg, Germany) in the Electrophysiology Unit of the
committee and informed consent was waived.
Department of Neurology. The number of the analyzed motor unit
|
3 of 6
MEYER et al.
F I G U R E 1 Imaging findings in a 75-year-old patient with polymyositis. (a) T2w fat-suppressed short tau inversion recovery (STIR) image showing edema of the thigh musculature, especially of the triceps surae muscle. The investigated muscle with EMG and ADC is the tibialis anterior muscle. (b) ADC map. The different ADC values of the most affected muscle are as follows: ADCmin = 1.32 × 10−3 mm2/s, ADCmean = 1.45 × 10−3 mm2/s, and ADCmax = 1.64 × 10−3 mm2/s). (c) The representative EMG curves of the tibialis anterior muscle. The mean MUAP duration is 12.2 ms, and the mean amplitude is 2.69 mV
action potential (MUAP) and its characteristic features (amplitude, duration) were measured in each affected muscle. Pathological spontaneous activity (PSA) was evaluated. Video EMG recordings were analyzed for PSA and MUAP variables in each muscle examined. The investigated muscles were as followed: n = 2 (25%) M. tibialis anterior, n = 2 M. vastus medialis (25%), and n = 4 (50%) M. vastus lateralis, respectively.
TA B L E 2 Estimated DWI and EMG parameters Parameters
M ± SD
ADCmean, ×10 −3 mm2/s ADCmin, ×10
−3
2
1.51 ± 0.29
Median
Range
1.46
1.07–1.96
mm /s
1.28 ± 0.27
1.30
0.70–1.58
ADCmax, ×10 −3 mm2/s
1.73 ± 0.28
1.68
1.40–2.20
Amplitude, mV
0.97 ± 0.81
0.70
0.31–2.70
Duration, ms
9.79 ± 2.32
9.50
6.40–12.70
2.5 | Statistical analysis Statistical analysis and graphics creation were performed using GraphPad Prism (GraphPad Software, La Jolla, CA, USA). Collected data were evaluated by means of descriptive statistics (absolute and relative frequencies). Spearman’s correlation coefficient (p) was used to analyze associations between investigated parameters. ADC and clinical subgroups were analyzed by Mann–Whitney test. In all instances, p values
