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Traumatic needle damage to nerves during regional anesthesia: presentation of a novel mechanotransduction hypothesis
  1. Graeme A McLeod1,2,
  2. Amy Sadler1 and
  3. Tim G Hales3
  1. 1 Department of Anaesthesia, NHS Tayside, Dundee, UK
  2. 2 Division of Imaging and Technology, University of Dundee, Dundee, UK
  3. 3 Division of Systems Medicine, University of Dundee, Dundee, UK
  1. Correspondence to Professor Graeme A McLeod, Department of Anaesthesia, NHS Tayside, Dundee DD1 9SY, UK; g.a.mcleod{at}


Despite advances in needle positioning techniques, nerve damage still occurs after regional anesthesia. Recognized causes include local anesthetic toxicity, subperineural injection, high subepineural fluid injection pressures and subepineural hematoma after forceful needle-–nerve contact.

We hypothesize that subperineural injection is still possible, but less likely to be the cause of nerve damage because needle penetration of fascicles and mechanical damage is difficult to achieve. High-resolution (75 µm) 40 MHz micro-ultrasound images of pig axillae show short-bevelled 22 g, 0.7 mm wide block needles that are three times larger than the average fascicle. Fascicular bundles are extremely difficult to puncture because they spin away on needle contact. Histology from fresh cadavers after supposed intrafascicular injection shows fluid spread within perineurium and intrafascicular perineural septae, but no breach of endoneurium or axons.

We propose that mechanotransduction, the cellular changes that occur in response to force, contributes to nerve damage. Piezo ion channel proteins transduce force into electrical activity by rapid entry of cations into cells. Excessive Ca2+ influx into cells has the potential to inhibit nerve regeneration. Cellular changes include regulation of gene expression. The forces associated with purposeful needle insertion are generally unknown. Our experiments in the soft embalmed Thiel cadaver showed a lognormal range of forces between 0.6 N and 16.8 N on epineural penetration.

We hypothesize that forceful needle injury may cause nerve damage by activation of Piezo receptors and release of intracellular Ca2+.

  • nerve block
  • peripheral nerve injuries
  • neurologic manifestations

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  • Collaborators N/A.

  • Contributors GAM and AS provided the original idea. GAM, AS and TH wrote the paper.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.