Topographical Mapping of the cardiac autonomic innervation for selective cardiac neuromodulation in pigs and rabbits using MicroCT

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Horizon 2020- EU H2020-EU.1.2.2. - FET Proactive

"NeuHeart" Nr. 824071

Background & Introduction

In recent years, Vagus Nerve Stimulation (VNS) has proved to be a potential therapeutic approach for the treatment of cardiovascular diseases, such as Heart Failure or atrial fibrillation [1]. However, the lack of specific anatomical knowledge of the cervical VN [2, 3] and thus, of the cardiac autonomic innervation aggravates the side effects of unselective cervical VNS.

Purpose

The goal of this study was to investigate the cardiac vagus nerve branches for selective cardiac VNS stimulation using micro-computed tomography (µCT) and 3D renderings.

Methods

Vagus nerve specimens (n= 11 pig nerves, n= 5 rabbit nerves) were harvested from the nodose ganglion down to the cardiac branches in domestic pigs and New Zealand White rabbits on both sides, and the cardiac autonomic innervation was mapped µCT and 3D renderings.

Results

Our results provide anatomical and topographical key features on the cervical and cardiac autonomic innervation including course of the cardiac branch, cardiac branching patterns, fascicle number, and size of the autonomic nerves. We also compared these aforementioned anatomical parameters between pigs and rabbits and highlighted key anatomical differences among individuals within pigs. In pigs, the cardiac branches were partly composed of both nerves even when they branched off the VN whereas in rabbits, the two nerves were completely separated and the cardiac branch was solely parasympathetic. Finally, we generated a 3D model of various parts of the VN specimen and compared them to images of the native nerves taken during VN dissection surgery.

Conclusions

Here we present an imaging approach to map the anatomy and topography of the cardiac Vagus Nerve for selective stimulation of cardiac VN branches. We also characterized the morphology of the VN, the sympathetic trunk (ST), and the cardiac branch (CB) at the level of the cardiac branching point to highlight the complex interplay between the nerves. Our data provide one possible reason for unwanted side effects of cervical VNS. However, future studies are required to broaden the knowledge in this specific research field of selective cardiac VNS.

Transcranial magnetic stimulation and chronic pain: current status

OBJECTIVE

To examine evidence suggesting a potential role for transcranial magnetic stimulation (TMS) in the treatment of chronic pain.

CONCLUSION

Chronic pain is characterized by brain changes that can reasonably be presumed to be associated with hyperalgesia, as occurs with neuropathic changes in the periphery. TMS has the ability to induce plastic changes in the cortex at the site of stimulation and at connected sites, including the spinal cord. It also has the ability to influence the experience of experimental/acute pain. In studies of TMS in chronic pain, there is some evidence that temporary relief can be achieved in a proportion of sufferers. Chronic pain is common. Current treatments are often ineffective and complicated by side-effects. Work to this point is encouraging, but systematic assessment of stimulation parameters is necessary if TMS is to achieve a role in the treatment of chronic pain. Maintenance TMS is currently provided in relapsing major depression and may be a useful model in chronic pain management.

Changes to cold detection and pain thresholds following low and high frequency transcranial magnetic stimulation of the motor cortex

There is some evidence that repetitive transcranial magnetic stimulation (rTMS) can alleviate the experience of chronic pain. The mechanisms by which rTMS may induce pain relief, however, are unknown. The present study examined whether a session of rTMS would produce sensory threshold changes in healthy individuals. Detection and pain thresholds for cold sensations were compared following low frequency (1 Hz) (Experiment 1) and high frequency (20 Hz) (Experiment 2) repetitive TMS. While cold detection threshold was significantly lowered by both rTMS rates, only high frequency rTMS produced a significant change in cold pain threshold. In contrast, sham rTMS did not alter thresholds for cold stimuli. These findings provide evidence that sensory thresholds can be influenced by repetitive transcranial magnetic stimulation.

Psychiatry has much to offer for chronic pain

OBJECTIVE

The objective of this study was to make an argument in favour of the inclusion of psychiatrists on chronic pain clinic teams.

METHOD

The argument takes the form of answers to four central questions: (i) does pain involve an emotional experience; (ii) do psychiatric disorders accompany chronic pain; (iii) can psychiatric disorders present as chronic pain; and (iv) which patients present to pain units, and what do we know of their personalities?

RESULTS

The affirmative case was substantiated in respect of the first three questions. In examining the last question, evidence indicates that patients who present to chronic pain units frequently have personality features that make assessment and therapy difficult.

CONCLUSIONS

Psychiatry is the field of medicine where practitioners have the most experience with emotional states and personality, and is the only field where they have specialized skills in the diagnosis and treatment of psychiatric disorders. Psychiatry has much to offer in chronic pain management and chronic pain management teams should include a psychiatrist. This conclusion has resourcing and training implications.

Transcranial magnetic stimulation applications and potential use in chronic pain: studies in waiting

Transcranial magnetic stimulation (TMS) is a new technology which uses electromagnetic principles to produce small electrical currents in the cortex. Evidence indicates that TMS can produce plastic changes in the CNS which are observable at both the cellular and physiological levels. It is proposed that studies are justified to determine whether TMS can provide short-term or long-term relief in chronic pain.