Chronic visceral pain secondary to ventral disc herniation: Development of visceral complex regional pain syndrome.

When an organ disease is ruled out as the origin of pelvic pain, the superior hypogastric plexus (SHP) injury and consequent dysfunction could be the mechanism of visceral chronic pain perpetuation. As much as a dorsal discus herniation may harm the dorsal or ventral roots, a ventral discus herniation at L4-L5 or L5-S1 may result in direct physical trauma to the SHP, maintaining chronic visceral pain mediated by sympathetic dysfunction, conceivably also afferent fibers dysfunction. We propose that similarly to nociceptive somatic dysfunction named complex regional pain syndrome, the maintained sympathetic pelvic pain secondary to straight physical damage to the SHP characterize in fact the same disease, but in nociceptive visceral tissue, named visceral complex regional pain syndrome, a concept constructed based on the International Association for the Study of Pain criteria (1994).

INTRODUCTION

When an organ disease is ruled out as the origin of pelvic pain, other causes including injury of the sensory afferent or the sympathetic efferent fibers of the viscera should be taking into account. These fibers engage together to consist the superior hypogastric plexus (SHP), responsible for the innervation of pelvic viscera[1] and lye in front of the lumbar discus, emerging the possibility of secondary SHP dysfunction due to ventral discogenic herniation. It is described and discussed five cases of patients suffering from long lasting chronic pelvic pain, which was credited to be secondary to ventral lumbar disc herniation and introduced the new concept of visceral complex regional pain syndrome, built based on the International Association for the Study of Pain (IASP) criteria.[2]

CASE REPORTS

The Ethics Committee of the Teaching Hospital approved the study protocol (HC-FMRP-USP n°. 1430/2010) and patients gave written informed consent. Table 1 describes five patients with chronic pelvic pain. The spine magnetic resonance imaging (MRI) had obvious anterior disc protrusion and high signal intensity anterior to the disc protrusion on MRI (Time 2; Window 1-T2W1). All patients met the inclusion criteria: Pelvic pain for more than 6 months, anterior lumbar disc herniation, high signal intensity anterior to the disc protrusion on MRI (T2W1) and positive result secondary to SHP test block [Table 2]. Exclusion criteria were structural abdominal diseases, untreated coagulopathy, unstable medical illness, neuropathy secondary to diabetes, viral neuropathy, alcohol neuropathy or cognitive impairment that precluded an accurate response assessment.

Table 1

Patients description and demographic data

Table 2

Case conduction

Patient 1-Male, history of disturbing pelvic pain associated to upper right abdominal pain. Thoracic and lumbo-sacral magnetic resonance revealed ventral discus herniation at thoracic T11-T12 and lumbar L4-L5 levels. Patient was submitted to L3, L4, and L5 sympathetic test block [Figure 1], which evidenced a ventral discus extrusion deriving from L4 to L5, accommodating over the ventral face of the L5 lumbar disc [Figure 2]. Patient had relief from pelvic pain after sympathetic test block combined to SHP test block, and from upper abdominal right pain from right splanchnic test block at T11 and T12. After 5 months, as pain gradually returned, he was submitted to radiofrequency ablation.

Figure 1

Oblique vision of lumbar (L) vertebral bodies, demonstrating the tunnel vision for the needle positioning for sympathetic ganglion block at L3, L4 and L5

Figure 2

Lateral vision of ventral discus extrusion deriving from lumbar L4-L5, accommodating over the ventral face of the L5 lumbar disc, where superior hypogastric plexus lyes

Patient 2-Female, disabling pelvic pain that got worst at sexual intercourse. Lumbar MR revealed a ventral discogenic herniation at L5-sacral S1. She was submitted to SHP test block and was pain free from pelvic pain. After 7 months, she was submitted to RF ablation of SHP. She is still comfortable after 4 years evaluation.

Patient 3-Female, worsening pelvic pain associated to right upper abdominal pain. Thoracic and lumbo-sacral magnetic resonance revealed obvious ventral discus herniations at T11-T12 and L5-S1 levels. Patient had relief from pelvic pain after SHP test block, and from upper abdominal right pain from right splanchnic test block at T11 and T12. She is still pain-free in 9 months evaluation.

Patient 4-Female, suffered from pelvic and perineal pain, married with no sexual intercourse for the past 3 years and under psychiatric supervision. Magnetic resonance revealed protruded ventral disc herniation at L5-S1 and sacral cysts. She was submitted to SHP block combined to impar block. Sacral cysts puncture at left foramina S2 and S3 was performed under fluoroscopy. She is still pain-free for the past 2 years evaluation.

Patient 5-Female, suffered from pelvic pain, single, no history of sexual intercourse. Magnetic resonance revealed big protruded ventral disc herniation at L4-L5 lumbar discus. She was submitted to SHP block with complete but not long lasting pain relief. Three months later she was submitted to L4-L5 discectomy by laser ablation (3 cycles of 400 joules, with 1 min interval between cycles (Medlaser, AVR Surgical). She is still very comfortable after 12 months evaluation.

DISCUSSION

This discussion focus on the importance of the consideration of the spine en block, including its ventral and dorsal regions. When pain is characterized as nociceptive somatic, the dorsal region of the spine should be carefully evaluated. However, visceral and sympathetic pain refer us to the ventral aspect of the vertebral bodies at the medium-lower thoracic, lumbar and sacral regions.

Because of its site of localization just anterior aspect of the vertebrae L5-S1 bodies, a herniation could harm the cellular body of the sympathetic postganglionic neuron when it synapses with the efferent sympathetic preneuron;[3] and it has been proposed the possibility of intact preganglionic axons sprouting collaterals to supply denervated ganglion cells.[4] As a consequence, chronic pelvic pain can become self-perpetuating, and now comes a question whether visceral chronic pain secondary to discogenic herniation and sympathetic hyperactivity could be classified as complex regional pain syndrome, based on the IASP criteria defined in 1994.[2]

As part of our protocol, all patients were firstly submitted to central neuraxial block [Table 2] aiming to central desensitization.[5] Clinical observation reveals that both peripheral and central mechanisms are involved in the generation and maintenance of cross-viscera sensitization and hypersensitivity.[6] Mechanisms underlying visceral hypersensitivity may include sensitization of afferent neurons and sympathetic efferent fibers (peripheral sensitization) and sensitization of spinal cord dorsal horn neurons.[7] Another important mechanism is wind-up, a form of homosynaptic activity-dependent plasticity characterized by a progressive increase in action potential output from dorsal horn neurons. The amplification process could also be aided by alterations in spinal or supraspinal glial-neuronal relations.[8] Among peripheral mechanisms, N-methyl-D-aspartate receptors were demonstrated to be expressed on the cell bodies and peripheral terminals of the primary afferent nerves innervating the colon.[9] In addition, peripheral inflammation activates microglia in the spinal cord that release proinflammatory cytokines[10] and can influence the excitability of central neurons.

As conclusions, the ventral part of the spine should be carefully evaluated looking for any reasons for HSP harm and dysfunction, such as ventral L4-L5-S1 discus intervertebralis herniation. Because visceral nociceptive tissue can, as much the somatic nociceptive tissue, suffer from secondary nervous tissue damage with consequent afferent C and Ad-fibers and efferent sympathetic dysfunction, it equally could be classified as complex regional pain syndrome of the visceral tissue, or visceral complex regional pain syndrome.