Altered Coupling Between Resting-State Cerebral Blood Flow and Functional Connectivity Strength in Cervical Spondylotic Myelopathy Patients

Beyond the aging spine - a systematic review of functional changes in the human brain in cervical spondylotic myelopathy

Cervical Spondylotic Myelopathy (CSM) is a degenerative condition that leads to loss of cervical spinal cord integrity, typically affecting the aged population. Emerging fMRI-based evidence suggests that the brain is also affected by CSM. This systematic review aimed to understand the usefulness of brain fMRI in CSM. A comprehensive literature search was conducted until March 2023 according to PRISMA guidelines. The inclusion criteria included original research articles in English, primarily studying the human brain's functional changes in CSM using fMRI with at least 5 participants. The extracted data from each study included demographics, disease severity, MRI machine characteristics, affected brain areas, functional changes, and clinical utilities. A total of 30 studies met the inclusion criteria. Among the fMRI methods, resting-state fMRI was the most widely used experimental paradigm, followed by motor tasks. The brain areas associated with motor control were most affected in CSM, followed by the superior frontal gyrus and occipital cortex. Functional changes in the brain were correlated to clinical metrics showing clinical utility. However, the evidence that a specific fMRI metric correlating with a clinical metric was "very low" to "insufficient" due to a low number of studies and negative results. In conclusion, fMRI can potentially facilitate the diagnosis of CSM by quantitatively interrogating the functional changes of the brain, particularly areas of the brain associated with motor control. However, this field is in its early stages, and more studies are needed to establish the usefulness of brain fMRI in CSM.

Brain MRI changes in degenerative cervical myelopathy: a systematic review

BACKGROUND

Degenerative cervical myelopathy (DCM) is the most common cause of adult spinal cord dysfunction globally. Associated neurological symptoms and signs have historically been explained by pathobiology within the cervical spine. However, recent advances in imaging have shed light on numerous brain changes in patients with DCM, and it is hypothesised that these changes contribute to DCM pathogenesis. The aetiology, significance, and distribution of these supraspinal changes is currently unknown. The objective was therefore to synthesise all current evidence on brain changes in DCM.

METHODS

A systematic review was performed. Cross-sectional and longitudinal studies with magnetic resonance imaging on a cohort of patients with DCM were eligible. PRISMA guidelines were followed. MEDLINE and Embase were searched to 28th August 2023. Duplicate title/abstract screening, data extraction and risk of bias assessments were conducted. A qualitative synthesis of the literature is presented as per the Synthesis Without Meta-Analysis (SWiM) reporting guideline. The review was registered with PROSPERO (ID: CRD42022298538).

FINDINGS

Of the 2014 studies that were screened, 47 studies were identified that used MRI to investigate brain changes in DCM. In total, 1500 patients with DCM were included in the synthesis, with a mean age of 53 years. Brain alterations on MRI were associated with DCM both before and after surgery, particularly within the sensorimotor network, visual network, default mode network, thalamus and cerebellum. Associations were commonly reported between brain MRI alterations and clinical measures, particularly the Japanese orthopaedic association (JOA) score. Risk of bias of included studies was low to moderate.

INTERPRETATION

The rapidly expanding literature provides mounting evidence for brain changes in DCM. We have identified key structures and pathways that are altered, although there remains uncertainty regarding the directionality and clinical significance of these changes. Future studies with greater sample sizes, more detailed phenotyping and longer follow-up are now needed.

FUNDING

ODM is supported by an Academic Clinical Fellowship at the University of Cambridge. BMD is supported by an NIHR Clinical Doctoral Fellowship at the University of Cambridge (NIHR300696). VFJN is supported by an NIHR Rosetrees Trust Advanced Fellowship (NIHR302544). This project was supported by an award from the Rosetrees Foundation with the Storygate Trust (A2844).

Brain Structural and Functional Dissociated Patterns in Degenerative Cervical Myelopathy: A Case-Controlled Retrospective Resting-State fMRI Study

Background

Previous studies have shown the whole-brain global functional connectivity density (gFCD) and gray matter volume (GMV) alterations in patients with degenerative cervical myelopathy (DCM). However, no study aimed to investigate the associations between the spatial patterns of GMV and gFCD alterations in patients with DCM.

Methods

Structural data and resting-state functional MRI data of 35 DCM patients and 35 matched healthy controls were collected to assess their gFCD and GMV and investigate gFCD and GMV alterations in patients with DCM and their spatial pattern associations.

Results

In our current study, significant gFCD and GMV differences were observed in some regions of the visual system, sensorimotor cortices, and cerebellum between patients with DCM and healthy controls. In our findings, decreased gFCD was found in areas primarily located at the sensorimotor cortices, while increased gFCD was observed primarily within areas located at the visual system and cerebellum. Decreased GMV was seen in the left thalamus, bilateral supplementary motor area (SMA), and left inferior occipital cortices in patients with DCM, while increased GMV was observed in the cerebellum.

Conclusion

Our findings suggest that structural and functional alterations independently contributed to the neuropathology of DCM. However, longitudinal studies are still needed to further illustrate the associations between structural deficits and functional alterations underlying the onset of brain abnormalities as DCM develops.