Korean J Pain.  2021 Jan;34(1):132-136. 10.3344/kjp.2021.34.1.132.

Does subepineural injection damage the nerve integrity? A technical report from four amputated limbs

• Diwan S
• Nair A
• Sancheti P
• Zundert AV

• KMID: 2510320
• DOI: http://doi.org/10.3344/kjp.2021.34.1.132

Abstract

Local anesthetic (LA) injection outside the sheath in epineural or paraneural connective tissue is considered safe practice among regional anesthesiologists. There is limited evidence as to whether neurological complications occur if LA is injected inside the sheath (subepineural - intraneural). We performed ultrasound guided injections at the level of undivided sciatic nerve in four amputated lower limbs. In two specimens, LA was injected in epineural connective tissue (paraneural tissue) and in another two specimens by penetrating the outer nerve sheath (hyperechoic epineurium). Ultrasonography demonstrated an increase in the size of nerve and macroscopic findings revealed fascicular tracings with sub-epineural injections. Limbs were sent for histological analysis in formalin containers. Pathologist performed the analysis which demonstrated an intact perineurium and a breach in the epineurium. We conclude that sub-epineural injections are unsafe and injection should be done in paraneural tissue to ensure safety and avoid unwanted neurological sequelae after the block.

Keyword

Anesthetics; Local; Injections; Nerve Block; Neuralgia; Pathology; Peripheral Nerves; Sciatic Nerve; Ultrasonography; Interventional

Figure

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  Fig. 1 L1 specimen in prone position, with ultrasound guided injection at the popliteal sciatic nerve through a sterile insulated needle under a linear probe.

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  Fig. 2 L1 specimen in prone position. (A) The needle in-plane (white arrow) inserted from lateral to medial. The marker – dark blue – is on lateral side depicts the orientation marker. Green line denotes paraneural covering i.e., epineural connective tissue. The blue cross is the paraneural spread of the solution. Orange dots are fascicles. (B) Schematic diagram of Fig. 2A. LA: local anesthetic.

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  Fig. 3 L3 specimen in prone position. (A) The needle in-plane (white arrow) inserted from lateral to medial in L3. The marker – dark blue – is on lateral side depicts the orientation marker. Green line denotes paraneural covering i.e., epineural connective tissue. Blue asterisk is the intraneural solution spread. Orange dots are fascicles. (B) Schematic diagram of Fig. 3A. LA: local anesthetic.

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  Fig. 4 L1 and L3 specimen in prone position. (A) Macroscopic findings of solution dispersal in L1. In the epineural connective tissue (EPI-ct) (paraneural) needle placement and injection of methylene blue dye (MBD) revealed an EPI-ct (paraneural) spread of MBD between the two nerves at the level of division. The EPI-ct (paraneural) and the epineural coverings of the nerves are well delineated. (B) Schematic diagram of Fig. 4A. (C) Macroscopic findings of solution dispersal in L3 specimen. (D) Schematic diagram of Fig. 4C. CPN: common peroneal nerve.

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  Fig. 5 Histological information about L1 and L3 specimen (hematoxylin and eosin stain, low power [×10]). (A) Histological findings of specimen L1. Epineural connective tissue (paraneural tissue-green lines) injection in L1, revealed localization of methylene blue dye in the epineural connective tissue (paraneural). The intact inner epineurium (gold) and the perineurium (dark blue arrows) and internal architecture of the nerve are well preserved. (B) Histological findings of specimen L3. Sub-epineural needle placement (inside the sheath) revealed the breach of inner epineurium (gold).

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