Background & Aims

Pain management for post herpetic neuralgia entails different modalities. Pharmacologic intervention remains to be a foundation for treatment. Furthermore, interventional pain therapies have also been used to decrease the pharmacologic burden and decrease unwanted adverse reactions to drugs. This case report narrates an unexpected development of an abdominal mass after the administration of thoracic erector spinae plane block with local anesthetic day. Possible theories behind the development of an abdominal mass following the said peripheral nerve block are explored.

Methods

A 52-year-old, Korean, male with diabetes, hypertension and body mass index of 35 was seen for left flank pain extending to the left periumbilical area of a month duration associated previously with a maculopapular rash and blisters that has already dried up. Pain was described as stabbing, aching, with pins and needles scored at 6/10, and cold sensation over the abdominal part corresponding to T10 dermatome. He was initially diagnosed as postherpetic neuralgia T10 left and was given a course of antivirals, paracetamol, pregabalin, and tramadol. However, he developed pruritus after taking the pregabalin and tramadol, hence was referred to the pain clinic. He underwent ultrasound guided erector spinae plane block at T10, left, with 20mL Bupivacaine 0.25% + Methylprednisolone 40mg. This immediately afforded relief of pain to 3/10. However, the patient developed a round, hard, 3cm by 3cm nontender, nonreducible mass over the left abdomen at the level of T10 12 hours after the procedure. The mass resolved within a day. In the interim, neuropathic symptoms resolved and there was no recurrence of the abdominal mass, pins and needles, and cold sensation.

Results

In the setting of herpes zoster, the reactivation of the virus causes myelin and axon deficiency and atrophy of the dorsal horn. The neuropathy follows a dermatomal distribution and in this case at T10. Erector spinae plane (ESP) block is said to work through diffusion of the injectate into the paravertebral space or by spread toward the ventral and dorsal rami of spinal nerves and may spread craniocaudally. Blockade of the ESP with 20mL of bupivacaine and methylprednisolone was successful as congruent with the report of relief by the patient. A number of case reports of abdominal pseudo-hernia caused by herpes zoster have been documented. It is a rare complication wherein the virus attacks the ventral root causing abdominal muscle paralysis and abdominal mass without actual structural defects. With this in mind, the authors propose that the performed ESP block had weakened or paralyzed the affected abdominal wall by blockade at the ventral and dorsal rami at T10, possibly with craniocaudal spread. On the other hand, the injectate may also had an anterior spread deep to the fascial planes of intercostal muscles producing the mass at the lateral abdominal area. This is the most dependent area of the dermatome anatomic wise on the patient on prone position. These theories are compatible with the timeline of the mass with the duration of the effect of bupivacaine for an interfascial plane block such as ESP.

Conclusions

Thoracic erector spinae plane block with bupivacaine and methylprednisolone reduced pain by 50% in a patient with post herpetic neuralgia. Patient was obese, diabetic, and hypertensive. An abdominal mass developed 12 hours after injection probably secondary to muscle weakness or paralysis from the ESP block; or local migration of the injected solution deep to the fascial plane of intercostal muscles. The abdomen was the most dependent area of the patient in a prone position and could be a major factor for the migration of the injectate. Since the abdominal mass resolved in less than a day, other pathologies over the abdomen were not explored.

An abdominal mass following thoracic erector spinae plane block is an unusual occurrence. There are limited to no publications found to narrate a similar event. This case report is able to provide additional knowledge regarding a situation that may occur after a well- known peripheral nerve block. Patient education, specifically when securing informed consent, can be improved with this new information.

References

Ahmed, S. A., Magdy, A. A., Abdullah, M. A., & Albadry, A. A. (2022). The Effect of Erector Spinae Plane Block With and Without Addition of Magnesium on Relief of Pain from Post-herpetic Neuralgia. Pain physician, 25(5), 365–372. De Cassai, A. et al. (2019). Erector spinae plane block: a systematic qualitative review. Minerva anestesiologica, 85(3), 308–319. https://doi.org/10.23736/S0375-9393.18.13341-4 Gruver C, Guthmiller KB. Postherpetic Neuralgia. [Updated 2023 Apr 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493198/
NYSORA. (2022, April 12). Erector spinae plane nerve block. NYSORA. https://www.nysora.com/erector-spinae-plane-block/ Mehta, P., Maher, P., & Singh, J. R. (2015). Treatment of postherpetic neuralgia using a thoracic transforaminal epidural steroid injection. PM & R : the journal of injury, function, and rehabilitation, 7(4), 443–446. https://doi.org/10.1016/j.pmrj.2014.11.009 Whitman PA, Launico MV, Adigun OO. Anatomy, Skin, Dermatomes. [Updated 2023 Oct 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535401/ Selvi, O., & Tulgar, S. (2018). Ultrasound guided erector spinae plane block as a cause of unintended motor block. Bloqueo en el plano del erector de la columna ecoguiado como causa de bloqueo motor imprevisto. Revista espanola de anestesiologia y reanimacion, 65(10), 589–592. https://doi.org/10.1016/j.redar.2018.05.009 Yoo, Jisook et al. “Abdominal pseudohernia caused by herpes zoster: 3 case reports and a review of the literature.” JAAD case reports vol. 5,8 729-732. 5 Aug. 2019, doi:10.1016/j.jdcr.2019.06.019

Presenting Author

Christian Cerafica

Poster Authors

Christian Cerafica

MD, MBA

Pain Medicine Fellow-in-Training, The Medical City, Ortigas, Philippines

Lead Author

Glenice Kane Nocom-Fong

MD, MBA, DPBA, DPBPM

Assistant Training Officer: Pain Medicine Fellowship Program; and Training Officer, Anesthesiology Residency; Department of Anesthesiology, The Medical City, Ortigas, Philippines

Lead Author

Topics

  • Specific Pain Conditions/Pain in Specific Populations: Neuropathic Pain - Peripheral