Evaluation of magnetic resonance spectroscopy total sodium concentration measures, and associations with microstructure and physical impairment in cervical myelopathy

Abstract

Cervical myelopathy; Macromolecular tissue volume; Spinal cord

Mielopatia cervical; Volum del teixit macromolecular; Medul·la espinal

Mielopatía cervical; Volumen del tejido macromolecular; Médula espinal

Spinal cord injury causes a cascade of physiological responses, which may trigger a subsequent neurotoxic increase in intracellular sodium. This can lead to neurodegeneration, both at and beyond the site of injury, causing clinical symptoms and loss of function. However, in vivo measurements of tissue sodium remain challenging. Here we utilise sodium magnetic resonance spectroscopy (23Na-MRS) at 3T to measure tissue sodium concentration (TSC) and its association with microstructural measures and macromolecular MRI metrics in the cervical spinal cord, distal to the site of injury. Twenty people with cervical myelopathy and twenty healthy controls, were studied. Associations with motor and sensory impairments were explored using ASIA and jOAMEQ scores. No significant difference in TSC in the cervical myelopathy group (39 ± 10 mM) relative to healthy controls (35 ± 13 mM) was found. However, patients had a significantly lower cord-cross-sectional area than controls (70 ± 9 mm2 vs. 82 ± 9 mm2, p < 0.001). Lower-extremity function positively correlated with intracellular volume fraction (p = 0.031). In conclusion, using 23Na-MRS, TSC in cervical myelopathy patients was successfully measured. Differences in TSC relative to healthy controls did not reach significance, despite a significant reduction in cord-cross-sectional area. However, lower intracellular volume fraction, indicating reduced neurite density distal to the site of injury, was associated with physical impairment.

This study was supported by Wings for Life (#169111) to CGWK and BS. CGWK receives funding from MRC (#MR/S026088/1), Ataxia UK, Rosetrees Trust (#PGL22/100041 and #PGL21/10079). JNP is supported in part by funding from the United Kingdom’s Department of Health NIHR University College London Hospitals Biomedical Research Centres funding scheme. BS is also supported by the Multiple Sclerosis Society (175). CT is currently being funded by a Miguel Servet contract, awarded by the Instituto de Salud Carlos III (ISCIII), Ministerio de Ciencia e Innovación de España (CP23/00117). FG receives the support of a fellowship from “la Caixa” Foundation (ID 100010434). The fellowship code is "LCF/BQ/PR22/11920010".