Advanced MRI techniques
Advanced MRI techniques include brain and spinal cord volumetric
analyses, diffusion tensor imaging (DTI), and resting-state functional
MRI. These techniques are usually not applied as part of the clinical
routine workup in MOGAD patients, and quantitative volumetric and/or
microstructural grey and white matter analyses using advanced MRI
techniques are few. Recent studies, however, have identified specific
changes in MOGAD patients that are potential new imaging biomarkers and
tools for a better understanding of MOGAD disease pathology
(23,100–102).
Although brain lesion distributions have been found to differ between
MOGAD and AQP4-NMOSD patients, brain MRI volumetry did not show any
differences in MOGAD patients compared to healthy controls in whole
brain, deep grey matter, or white matter volumes (100,103). In children
with ADEM, reduced brain volume and failure of age-expected brain growth
was found for both MOG-IgG seropositive and -seronegative patients
(Bartels et al. submitted), similar to findings in paediatric
anti-NMDA-receptor encephalitis and paediatric-onset MS (7,81,104).
Spinal cord MRI analysis could identify spinal cord atrophy in patients
with MOGAD as compared to healthy subjects, which was found to associate
with increased counts of historical myelitis attacks. However, cord
lesion frequency and atrophy was found to be less frequent compared to
AQP4-TM (41,101). In MOG-myelitis patients, another study showed that
the grey matter volume in the spinal cord was reduced during the acute
phase of the attack (102).
Resting-state functional MRI connectivity allows for the study of
functional connectivity alterations, such as in the visual or
sensorimotor networks of the brain (105–107). Recently, it was found
that altered interhemispheric function in patients with MOG-ON can be
observed compared to healthy controls using resting-state functional MRI
(108).
Meanwhile, evaluating network and CNS changes using graph theory and
network statistical methods for elucidating clinical attack-related
damage in NMOSD patients has also shown promise. Both cortical
topological network changes and deep grey matter volume changes have
been detected in AQP4-NMOSD patients following ON attacks and in
patients with a simultaneous combination of clinical attacks (109,110).
These findings suggest there may be non-localised damage or affection in
NMOSD, which could also be the case in MOGAD.
Using DTI, one study found decreased white matter integrity in adult
MOGAD patients compared to healthy controls, specifically reduced
parallel diffusivity within whole-brain white matter tracts (100). As
demyelination represents a pathological hallmark in MOGAD, in-vivo
imaging of myelin integrity could represent a promising technique to
further identify disease mechanisms and disease courses in MOGAD (111).
Further studies applying more advanced sequences representative of
myelin, such as T1-weighted/T2-weighted intensity-ratio, multi-parameter
mapping, and magnetization transfer MRI analysis in MOGAD patients may
help in identifying more subtle MRI changes in the future (112–114).