Subparaneural injection in popliteal sciatic nerve blocks evaluated by MRI

Abstract

<jats:title>Abstract</jats:title><jats:p>Intraneural injection of a local anesthetic can damage the nerve, yet it occurs frequently during distal sciatic block with no neurological sequelae. This has led to a controversy about the optimal needle tip placement that results from the particular anatomy of the sciatic nerve with its paraneural sheath.</jats:p><jats:p>The study population included patients undergoing lower extremity surgery under popliteal sciatic nerve block. Ultrasound-guidance was used to position the needle tip subparaneurally and to monitor the injection of the local anesthetic. Sonography and magnetic resonance imaging were used to assess the extent of the subparaneural injection.</jats:p><jats:p>Twenty-two patients participated. The median sciatic cross-sectional area increased from 57.8 mm2 pre-block to 110.8 mm<jats:sup>2</jats:sup> immediately post-block. An intraneural injection according to the current definition was seen in 21 patients. Two patients had sonographic evidence of an intrafascicular injection, which was confirmed by MRI in one patient (the other patient refused further examinations). No patient reported any neurological symptoms.</jats:p><jats:p>A subparaneural injection in the popliteal segment of the distal sciatic nerve is actually rarely intraneural, i.e. intrafascicular. This may explain the discrepancy between the conventional sonographic evidence of an intraneural injection and the lack of neurological sequelae.</jats:p>

Dual Guidance in Regional Anesthesia – Influence of Needle Electrode Configuration on Stimulation Success at Sciatic Nerve; A Randomized, Controlled Pilot Trial

“…Subparaneural injection of local anesthetics must therefore be distinguished from intraneural injection (subepineural or intrafascicular) with the potential risk of nerve lesion. 22 Thus, the aim should be to inject the local anesthetic subparaneurally.…”

Low volume distal sciatic block (LVDSB) - comparison spread of injectate between LVSDB and distal adductor canal in healthy volunteer

“…Při podrobnějším studiu anatomie ischiadického nervu zjistíme existenci společné pochvy distálního konce ischiadického nervu přechá zející na popliteální části tibiálního a fibulárního nervu. Tekutina podaná pod tento společný obal vyplňuje oběma směry epineurální prostor tibiálního nervu i společného fibulárního nervu, aniž by pronikla pod epineurium do jednotlivých nervů mezi fascikly [7,8,9,10].…”

“…Genikulární nervy jsou umístěny na ventrální straně ischia dického, tibiálního i společného fibulárního nervu. Předpokládáme, že definované množství anestetika, v přiměřené koncentraci, podaného do společného obalu v distální části ischiadického nervu má předpoklad vytvořit diferenciovanou analgetickou blokádu s omezením blokády motorické [7,8,13,14].…”

Ultrasound-Guided Subparaneural Axillary Block in Sub-Saharan Africa: A Prospective Multicenter Study and Review of Literature

“…This technique was initially used in sciatic blocks with satisfactory results in terms of the time taken to set up and the effectiveness of the sensory-motor block [9]. Analyses with magnetic resonance imaging showed a low rate of intrafascicular injection type nerve lesions with the perineural infiltration [10].…”