Users Online: 885 Home Print this page Email this page Small font sizeDefault font sizeIncrease font size  
Home | About us | Editorial board | Search | Ahead of print | Current issue | Archives | Submit article | Instructions | Subscribe | Contacts | Login 

RSACP wishes to inform that it shall be discontinuing the dispatch of print copy of JOACP to it's Life members. The print copy of JOACP will be posted only to those life members who send us a written confirmation for continuation of print copy.
Kindly email your affirmation for print copies to [email protected] preferably by 30th June 2019.


Table of Contents
Year : 2014  |  Volume : 30  |  Issue : 3  |  Page : 439-440

Tongue bite injury after use of transcranial electric stimulation motor-evoked potential monitoring

Department of Anesthesiology, Christian Medical College, Vellore, Tamil Nadu, India

Date of Web Publication22-Jul-2014

Correspondence Address:
Aparna Williams
Department of Anesthesiology, Christian Medical College and Hospital, Vellore - 632 004, Tamil Nadu
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-9185.137297

Rights and Permissions

How to cite this article:
Williams A, Singh G. Tongue bite injury after use of transcranial electric stimulation motor-evoked potential monitoring. J Anaesthesiol Clin Pharmacol 2014;30:439-40

How to cite this URL:
Williams A, Singh G. Tongue bite injury after use of transcranial electric stimulation motor-evoked potential monitoring. J Anaesthesiol Clin Pharmacol [serial online] 2014 [cited 2021 Jun 19];30:439-40. Available from:


Monitoring of motor-evoked potential (MEP) during spine surgery is considered a safe technique but potential hazards include bite injuries, possibility of hazardous stimulator output, patient movement induced injury, seizures, cardiac dysrhythmias, and epidural electrode-related complications. [1] Tongue and lip bite injuries are the most common reported complications during MEP monitoring with an incidence ranging from 0.2% to 0.63%. [1],[2] Previous case reports have reported bite injuries including minor tongue lacerations, broken teeth, and even bitten endotracheal tube. [1]

Thirty-seven-year-old, ASA physical status I, male with BMI 24.3 Kg/m 2 , was posted for L3-4 laminectomy and excision of L3 intradural tumor in the prone position with transcranial electric stimulation (TES) MEP monitoring. After induction of anesthesia and intubation, the endotracheal tube was taped to the right side and a soft bite block (rolled up gauze) was inserted in the midline. Surgery and anesthesia were uneventful and lasted two hours. Tracheal extubation was performed in the OR but the patient was mildly sedated. Postoperative examination of the oral cavity revealed a tongue hematoma on the left side [Figure 1]. He was reassured about the self-resolving nature of the hematoma and was advised oral care regimen.

Risk factors for tongue injury during TES MEP monitoring include C3-4 focused stimulation that directly activates the temporalis muscle [3] and prone position (as in our patient) as it predisposes to tongue swelling. [4] The mechanism of tongue injury may involve both corticobulbar activation with pulse-trains and direct muscle or trigeminal nerve stimulation, because jaw-clenching also occurs with single pulses. Use of C3/4 TES might produce stronger biting than C1/2 TES because the electrodes are closer to facial motor cortex, jaw muscles, and trigeminal nerves. [1]

Placement of a bite block is standard practice during MEP monitoring, but it does not necessarily prevent injury to oral structures as is evident in our case. Tongue injury due to bite block dislodgement and movement of the tongue between the teeth has been reported earlier. [3] There is no consensus on the type and number of bite blocks to reduce these injuries. Most reviewers suggest the use of soft bite blocks [1],[5] as rigid bite blocks may cause pressure injury to the tongue and lingual nerve and dental trauma. The use of three soft bite blocks (one in between the molars on each side and one in the centre) [5] and dental guards on the mandibular and maxillary dental lines with a soft bite block in between have been suggested. [6] Frequent intraoperative checking of the position of the bite block and the tongue has been recommended but this may be difficult if the patient is in the prone position, as in our case.
Figure 1: Tongue hematoma

Click here to view

All anesthesiologists need to be aware of and discuss the risk of injury to structures of the oral cavity when using TES MEP monitoring with the patient. Careful assessment for tracheal extubation is warranted in cases at high risk for injury, as an injured and swollen tongue may cause airway obstruction and need for re intubation. The use of less frequent and low voltage stimulation, correct placement of bite blocks, and continued vigilance to their position can go a long way in preventing patient bite injuries during TES MEP monitoring.

  References Top

1.MacDonald DB. Intraoperative motor evoked potential monitoring: Overview and update. J Clin Monit Comput 2006;20:347-77.  Back to cited text no. 1
2.Tamkus A, Rice K. The incidence of bite injuries associated with transcranial motor-evoked potential monitoring. Anesth Analg 2012;115:663-7.  Back to cited text no. 2
3.Deiner SG, Osborn IP. Prevention of airway injury during spine surgery: Rethinking bite blocks. J Neurosurg Anesthesiol 2009;21:68-9.  Back to cited text no. 3
4.Lam AM, Vavilala MS. Macroglossia: Compartment syndrome of the tongue? Anesthesiology 2000;92:1832-5.  Back to cited text no. 4
5.Pajewski TN, Arlet V, Phillips LH. Current approach on spinal cord monitoring: The point of view of the neurologist, the anaesthesiologist and the spine surgeon. Eur Spine J 2007;16(Suppl 2):S115-29.  Back to cited text no. 5
6.Mahmoud M, Spaeth J, Sadhasivam S. Protection of tongue from injuries during transcranial motor-evoked potential monitoring. Pediatr Anaesth 2008;18:902-3.  Back to cited text no. 6


  [Figure 1]

This article has been cited by
1 Smooth Extubation and Smooth Emergence Techniques: A Narrative Review
Tiffany H. Wong,Garret Weber,Apolonia E. Abramowicz,Ronald G. Pearl
Anesthesiology Research and Practice. 2021; 2021: 1
[Pubmed] | [DOI]
2 Comparison of Intraoperative Motor Evoked Potentials Monitoring with Direct Cranial Stimulation by Peg-Screw and Transcranial Stimulation by Corkscrew for Supratentorial Surgery
Kohei Kanaya,Tetsuya Goto,Tetsuyoshi Horiuchi,Kazuhiro Hongo
World Neurosurgery. 2019;
[Pubmed] | [DOI]
3 Optimal stimulation intensity for Br(E)-MsEP waveform derivation at baseline in pediatric spinal surgery
Kazuyoshi Kobayashi,Kei Ando,Masaaki Machino,Kyotaro Ota,Masayoshi Morozumi,Satoshi Tanaka,Shunsuke Kanbara,Sadayuki Ito,Naoki Ishiguro,Shiro Imagama
Clinical Neurology and Neurosurgery. 2019; 180: 74
[Pubmed] | [DOI]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
   Article Figures

 Article Access Statistics
    PDF Downloaded245    
    Comments [Add]    
    Cited by others 3    

Recommend this journal