Brain fMRI during orientation selective epidural spinal cord stimulation

Scientific Reports, 2021 · DOI: 10.1038/s41598-021-84873-8 · Published: March 15, 2021

Simple Explanation

This study introduces a new method for epidural spinal cord stimulation (ESCS) called Orientation Selective (OS) stimulation, which aims to improve the specificity and efficiency of traditional ESCS. The OS approach allows targeting ESCS to spinal fibers of different orientations, potentially making stimulation less dependent on precise electrode placement. The researchers used functional MRI (fMRI) to observe brain activation patterns during OS-ESCS in rats, finding that the stimulation activated complex brain networks involved in motor and sensory information transmission.

Study Duration

Not specified

Participants

n = 6 rats for monopolar ESCS, n = 11 for OS-ESCS

Evidence Level

Not specified

Key Findings

1
OS-ESCS modulates spinal-brain connectomes within the CNS, as demonstrated by brain activations during stimulation of S1 and L2 spinal segments.
2
Significant activations were observed in the thalamus, motor cortex, primary somatosensory cortex, retrosplenial cortex, and anterior cingulate cortex during OS-ESCS.
3
Orientation selectivity was strong in the cingulate and motor cortices, as well as in areas within the basal forebrain and septal regions, the thalamus and the hippocampus.

Research Summary

This study introduces Orientation Selective Epidural Spinal Cord Stimulation (OS-ESCS) in rats and uses fMRI to monitor brain activations during stimulation of spinal segments S1 and L2. The findings show that OS-ESCS modulates spinal-brain connectomes, activating brain regions such as the thalamus and motor cortex, and that the electric field direction affects the activation patterns. The authors conclude that OS-ESCS provides added flexibility for targeting specific axonal fiber orientations and optimizing activation of connected brain areas, potentially mitigating effects of electrode placement inaccuracies.

Practical Implications

Improved Pain Management

OS-ESCS may allow for more precise targeting of spinal cord structures, potentially improving pain management by selectively activating or avoiding specific pathways.

Enhanced Motor Function Restoration

By targeting specific axonal fiber orientations, OS-ESCS could enhance motor function restoration after spinal cord injury.

Clinical Translation

The conceptual framework of OS-ESCS is translatable to clinical settings, as fMRI has been used with SCS, and OS-ESCS paradigms can be implemented with commercially available electrodes.

Study Limitations

1
The sample size was relatively small, which may have limited the detection of group differences in brain patterns during OS-ESC of the two sites.
2
The use of anesthesia during the fMRI session, namely urethane, can induce switching between states of sleep during long experimental sessions, thus potentially confounding the results.
3
The relatively simple 3-channel design, and the relatively large size of the wires as compared to the dimension of the rat spinal cord, pose additional limitations to the current study.

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