Issues about the fMRI of the human spinal cord

Impact of realignment on spinal functional MRI time series

Functional magnetic resonance imaging (fMRI) of the spinal cord produces dataset that are particularly noisy because of cardiac-related motions. Realignment methods allowing subject motion correction might be sensitive to such noisy dataset. By realigning and quantifying cardiac variance on spinal dataset, we showed that such procedures decrease cardiac noise within the volumes. This has a direct and positive impact on functional imaging when estimating the T-score by means of the general linear model.

Functional responses in the human spinal cord during willed motor actions: evidence for side- and rate-dependent activity

Although the spinal cord is the output station of the central motor system, little is known about the relationships between its functional activity and willed movement parameters in humans. We investigated here blood oxygenation level-dependent functional magnetic resonance imaging (fMRI) signal changes in the cervical spinal cord during a simple finger-to-thumb opposition task in 13 right-handed volunteers, using a dedicated array of 16 receive-only surface coils on a 3 Tesla MRI system. In a first experiment, we found significant fMRI signal increases on both sides of the lower cervical spinal cord while subjects performed the motor task at a comfortable pace (approximately 0.5 Hz) using either hand. Both the spatial extent of movement-related clusters and peak signal increases were significantly higher on the side of the cord ipsilateral to the moving hand than on the contralateral side. Movement-related activity was consistently larger than signal fluctuations during rest. In a second experiment, we recorded spinal cord responses while the same motor sequence was performed using the dominant hand at two different rates (approximately 0.5 or 1 Hz). The intensity but not the spatial extent of the response was larger during higher rates, and it was higher on the ipsilateral side of the cord. Notwithstanding the limited spatial resolving power of the adopted technique, the present results clearly indicate that the finger movement-related fMRI signals recorded from the spinal cord have a neural origin and that as a result of recent technological advances, fMRI can be used to obtain novel and quantitative physiological information on the activity of spinal circuits.

Functional MR imaging of the cervical spinal cord by use of 20Hz functional electrical stimulation to median nerve

PURPOSE

Functional MR imaging of the human cervical spinal cord was carried out on volunteers by 20Hz functional electrical stimulation to median nerve, in order to detect signal changes arising concomitant to neuronal activity.

METHODS

Functional MR imaging data were acquired in six subjects with single-shot fast spin-echo sequence (SSFSE) on a 1.5T GE Clinical System. Cervical spinal cord activation was measured both in the sagittal and transverse imaging planes. Postprocessing was performed by AFNI (Analysis of Functional Neuroimages) software system.

RESULTS

Activation correlated with the time course of stimulation was consistently detected in both sagittal and transverse imaging planes of the cervical spinal cord. Regions of the spinal cord associated with motor and pain response were observed by 20Hz functional electrical stimulation to the median nerve.

CONCLUSION

The functional MR imaging signal can be detected in the human cervical spinal cord with functional electrical stimulation. Investigating the FES response in the spinal cord using the spinal fMRI will be helpful for the further discussion on the diagnosis and functional recovery to spinal cord diseases.

Subacute human spinal cord contusion: few lymphocytes and many macrophages

STUDY DESIGN

Clinicopathological correlation of three cases of subacute cervical spinal cord contusions.

OBJECTIVE

To correlate the pathology of subacute cervical spinal cord injury (SCI) with imaging and clinical-functional studies, and to compare with findings from previous human SCI studies and animal models of SCI.

SETTING

Department of Pathology, SUNY-Upstate Medical University, Syracuse, NY, USA.

METHOD

Post mortem pathology report.

CASE REPORT/RESULTS

The clinical, radiological, and pathological findings of three cases of subacute spinal cord contusions are described in detail. The postinjury survival periods were 15, 20, and 60 days, respectively. Extensive microglia/macrophage infiltrations without significant lymphocytes are seen in all cases. Free radical injury as assessed by immunocytochemistry for 4-hydroxynonenal and nitrotyrosine showed a labeling pattern parallel to that of the macrophage distribution at 15 days, but no significant labeling in the injury sites at 20 and 60 days.

CONCLUSION

The present report, though limited in sample size, shows plenty of activated microglia/macrophages in human SCI up to 60 days postinjury. This observation not only confirms similar findings in previous studies, but also raises an intriguing question of potential interactions between these activated microglia/macrophages and the experimental therapy, proposed by some authors, of injecting exogenously activated macrophages to promote SCI repair. The small number of human SCI cases (in this as well as in most other single medical centers) available for detailed study illustrates the need for the establishment of a consortium of human SCI tissue banks.