Visceral innervation is very complex. It is multi-level and it has multi-level efferents coming from the spine to the viscera and from the viscera to the spine. So we have all these multiple levels of communication between the viscera, which makes it complex in terms of how it interoperates and also how it presents as pain.

If you want to learn more about this topic, you can watch Chris Mercer's lecture here:

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Here are some of the reasons why visceral pain occurs:

1. Less than 10 % afferents at the dorsal horn are visceral

• A vast majority of afferents are coming from other sources.
• This leads to confusion or overlay of the afferent information coming in from the viscera

2. Pain mechanism similar to somatic pain

• We can get hyperexcitability of the ascending neurons, dysregulation of the descending pathways, and that can lead to the same type of presentation that we would see in musculoskeletal disorders

3. Mechanically insensitive afferents within the viscera

• These afferents are mechanically insensitive until they're activated by inflammation.
• If there is any inflammation within the viscera, these afferents become active and they don't switch off once the inflammation goes.

4. Diffuse, poorly localized pain

• Visceral pain is more broad and diffuse, and it often starts centrally and then spreads more peripherally as the disease or as the inflammation continues.

5. Dual innervation of many organs and multiple level afferent input

• Because of this multiple innervation Of multiple organs, there can be multiple different sites, and they can be much more widespread than we'd expect with a somatic referral

Watch this clip to know more about visceral innervation taken from the lecture ‘Visceral Masqueraders’ by Chris Mercer on Trust me-Ed.

If you want to learn more about this topic, you can watch Chris Mercer's lecture here:

Click here

Sources:
1. Lecture ‘Visceral Masqueraders’ by Chris Mercer on Trust me Ed.