Noninvasive assessment of the injured human spinal cord by means of functional magnetic resonance imaging

Abstract

Study design: A magnetic resonance imaging technique that enables indirect detection of neuronal activity has been developed for the spinal cord. In the present study, this method, spinal functional magnetic resonance imaging (fMRI), is applied to the first study of the injured spinal cord, with the goal of better clinical assessment of the entire cord. Objectives: The objectives of this project are: (1) to investigate the neuronal activity that can be detected in the spinal cord caudal to a chronic injury by means of spinal fMRI, and (2) to develop spinal fMRI as a clinical diagnostic tool. Setting: Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Manitoba, Canada. Methods: fMRI of the spinal cord was carried out in 27 volunteers with cervical or thoracic spinal cord injuries (SCIs). Of these volunteers, 18 had complete injuries, and nine had incomplete injuries. Spinal fMRI was carried out in a 1.5 T clinical MR system, using established methods. Thermal stimulation at 101C was applied to the fourth lumbar dermatome on each leg, and images were obtained of the entire lumbar spinal cord. Results: Areas of neuronal activity were consistently observed in the lumbar spinal cord in response to the thermal stimulation, even when the subjects had no awareness of the sensation. The pattern of activity was notably different compared with noninjured subjects. In general, subjects with complete SCI showed absent or diminished dorsal gray matter activity, but had enhanced ventral activity, particularly contralateral to the stimulation. Conclusions: Spinal fMRI is able to provide a noninvasive assessment of the injured spinal cord that does not depend on the patient's perception of the stimulus being applied. This work was carried out on a standard clinical MRI system without modification, and so is readily applicable in most MR units.

Detection of the neuronal activity occurring caudal to the site of spinal cord injury that is elicited during lower limb movement tasks

“…The activity detected is in agreement with known physiology and together with previous findings of increased contralateral activation in response to stimulation of the injured spinal cord suggest that spinal fMRI is providing reliable results. 2,[16][17][18][19] This occurrence and the implications for recovery of function in injured persons have recently come under closer investigation. 19 Investigation of neuronal circuitry caudal to a spinal cord injury site is required.…”

“…2,3 Spinal fMRI reveals neuronal function indirectly via changes in blood flow and blood oxygen levels that occur near metabolically active gray matter. 4 The signal change arises in part from the blood oxygen leveldependant (BOLD) contrast, which is based on the metabolic activity that occurs in active neuronal tissues.…”

“…This method has proven useful for detecting neuronal activity in both healthy and injured spinal cords in response to innocuous and noxious thermal stimulation, in which the distribution of activity and the signal intensity change were found to differ between conditions. 2 The neuronal response in the lumbar spinal cord to participation in active and passive lower limb movement tasks was characterized in a previous investigation involving healthy volunteers with spinal fMRI. 12 The current study aims to detect and characterize the neuronal response to these same tasks with spinal cord injured (SCI) volunteers.…”

“…Analysis can be carried out at a later time on a separate computer using published methods. [2][3][4] The resulting images reveal a large extent of the spinal cord, which can be displayed in axial, coronal, or sagittal orientation resulting in an effectively 3D display. This noninvasive technique is able to show where functional activity occurs in response to a stimulus regardless of a patient's ability to feel the stimulus, a feature the ASIA assessment scale is lacking.…”

Tactile‐associated fMRI recruitment of the cervical cord in healthy subjects

“…Despite this, seminal studies have shown that spinal cord fMRI is feasible and enables to obtain reliable results both in healthy subjects [Govers et al, 2007;Komisaruk et al, 2002;Kornelsen and Stroman, 2004;Li et al, 2005;Madi et al, 2001;Maieron et al, 2007;Moffitt et al, 2005;Ng et al, 2006;Stracke et al, 2005;Stroman and Ryner, 2001;Stroman et al, , 2002aStroman et al, , 2003aStroman et al, , 2005aYoshizawa et al, 1996] and in patients with spinal cord injury [Kornelsen and Stroman, 2007;Stroman et al, 2002bStroman et al, , 2004.…”