Prone positioning which is commonly used for posterior approaches in spine surgery, is associated with several severe complications like hemodynamic disturbance, ophthalmic conditions, nerve compressions and pressure ulcers4. Likewise, the use of neuromonitoring leads to strong contractions of the biting muscles, that could proceed to tongue bite injury 5. These biting induced oral injuries during neuromonitoring stimulations are rare but concerning complications of the prone positioning 6. Furthermore, prone position is also a risk factor for massive macroglossia due to neck flexion and lingual vein congestion 7. If this condition additionally occurs, it could correspondingly ease and aggravate tongue laceration during neuromonitoring.
Mentioned complications, all together may lead to a need of an emergency ENT intervention as well as delayed extubation with a swollen tongue. Tooth damage, mandibular fracture and even bite-rupture of endotracheal tubes requiring emergency reintubation are described in the literature5. The incidence of these complications seems to be low, however several minor bruising or minimal bleeding also might have been overlooked earlier reflecting an unpredictable incidence. Due to all these factors and risk of serious events, several approaches (use of bite blocks, positioning of the head) have been described in the literature aiming to prevent intraoral injuries during the use of neuromonitoring in prone position8. However, none of them were defined as gold standard for the prevention of neuromonitoring-induced oral wounds at prone position. Therefore, during prone position possible minor or major complications related to the use of neuromonitoring should be anticipated and careful positioning as well as proper protective measures should be planed.
In order to minimize complications, in our institution we have started to use a management protocol by utilizing a silicone athletes’ dental guard, of which the appropriate size is selected while the patient is awake. As our data is also supporting us, nearby preoperative selection of individual fit, it is also important to be vigilant for the proper placement of the selected bite-block. As by doing so demonstrated in Table 1 we have not encountered any single complication. Even though there were no statistical difference between Group I and II, this is due to the small number of patients in both groups and as we did not have any tongue lacerations after the introduction of our management protocol, it would be unethical to try to raise the number of patients in Group I as it would risk unnecessary lacerations.
We believe that preoperative verification of the proper fitting of the bite-blocker to the individual patient’s anatomy while they are already being awake and thereafter its correct placement subsequent to anesthesia induction and before prone positioning seems to be more important factors in our hands than the method being used to block the bite. Nevertheless, in all patients operated in prone position with neuromonitoring, still a proper and detailed postoperative inspection should be performed at the end of surgery, preferably before the extubation. However, as avoidance should be the main goal, an algorithmic approach as proposed in our study could be defined and applied to minimize the adverse effects of neuromonitoring induced bite injuries.