Model-based analysis of the acute effects of transcutaneous magnetic spinal cord stimulation on micturition after spinal cord injury in humans

PLoS Computational Biology, 2024 · DOI: https://doi.org/10.1371/journal.pcbi.1012237 · Published: July 1, 2024

Spinal Cord Injury Neurology Bioinformatics

Simple Explanation

A computer model was developed to simulate normal bladder control, dysfunctional control after spinal cord injury (SCI), and bladder responses to transcutaneous magnetic stimulation (TMS). Lumbar interneurons were added to enable a spinal voiding reflex, and descending control was modified to inhibit this reflex in adults. After SCI, descending inhibition is lost, and the spinal voiding reflex re-emerges; TMS responses required additional excitatory and inhibitory neurons in the lumbar spine with frequency-specific responses.

Study Duration

Not specified

Participants

Not specified

Evidence Level

Not specified

Key Findings

1
The model reproduced the re-emergence of a spinal voiding reflex after SCI, which is typically suppressed in adults but can reappear due to neural reorganization.
2
Low-frequency TMS (1 Hz) within the model normalized control of voiding after SCI, facilitating coordinated bladder contraction and urethral relaxation.
3
High-frequency TMS (30 Hz) enhanced urine storage by contracting the urethral sphincter and preventing simulated leaking and incontinence.

Research Summary

This study developed a computational model of the neural circuit of micturition to replicate normal bladder function, dysfunction after SCI, and responses to transcutaneous magnetic stimulation (TMS). The model incorporated an infantile spinal voiding reflex, which is suppressed in adults but re-emerges after SCI, and simulated the effects of TMS on lumbar interneurons. Results showed that low-frequency TMS normalized voiding after SCI, while high-frequency TMS enhanced urine storage, suggesting that TMS can modulate bladder function by differentially affecting spinal interneurons.

Practical Implications

Therapeutic intervention

TMS can be used as a non-invasive method to modulate spinal cord circuits and improve bladder control in patients with SCI.

Understanding neural dysfunction

The model helps in understanding the neural basis of adverse effects of SCI and how rehabilitation and neuromodulation can ameliorate neurological disorders.

Optimization of stimulation parameters

The differential sensitivity of excitatory and inhibitory neurons to TMS can be exploited to mitigate detrusor-sphincter dyssynergia.

Study Limitations

1
The model simplifies the dense network of interneurons as individual nodes.
2
Afferent information from the sphincter is ignored, as well as the diversity of receptors mediating afferent signals.
3
The model does not accurately reflect changes in neurotransmitter receptors, ion channels, and remodeled connections that occur after a SCI.

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