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OMFS-IMPATH Research Group, Department of Imaging and Pathology, Faculty of Medicine, University of Leuven, Leuven, BelgiumDepartment of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Faculty of Medicine, University of Leuven, Leuven, BelgiumDepartment of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium
Address: Myrthel Vranckx, Department of Oral and Maxillofacial Surgery, University Hospitals Leuven, Kapucijnenvoer 7 blok a, 3000 Leuven, Belgium. Tel: +32 (0)16 341975.
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Faculty of Medicine, University of Leuven, Leuven, BelgiumDepartment of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Faculty of Medicine, University of Leuven, Leuven, BelgiumDepartment of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Faculty of Medicine, University of Leuven, Leuven, BelgiumDepartment of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, Belgium
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Faculty of Medicine, University of Leuven, Leuven, BelgiumDepartment of Oral and Maxillofacial Surgery, University Hospitals Leuven, Leuven, BelgiumDepartment of Dental Medicine, Karolinska Institutet, Stockholm, Sweden
With the growing demand for dental work, trigeminal nerve injuries are increasingly common. This retrospective cohort study examined 53 cases of iatrogenic trigeminal nerve injury seen at the Department of Oral and Maxillofacial Surgery, University Hospitals of Leuven between 2013 and 2014 (0.6% among 8845 new patient visits). Patient records were screened for post-traumatic trigeminal nerve neuropathy caused by nerve injury incurred during implant surgery, endodontic treatment, local anaesthesia, tooth extraction, or specifically third molar removal. The patients ranged in age from 15 to 80 years (mean age 42.1 years) and 68% were female. The referral delay ranged from 1 day to 6.5 years (average 10 months). The inferior alveolar nerve (IAN) was most frequently injured (28 cases), followed by the lingual nerve (LN) (21 cases). Most nerve injuries were caused during third molar removal (24 cases), followed by implant placement (nine cases) and local anaesthesia injuries (nine cases). Pain symptoms were experienced by 54% of patients suffering IAN injury, compared to 10% of patients with LN injury. Persistent neurosensory disturbances were identified in 60% of patients. While prevention remains the key issue, timely referral seems to be a critical factor for the successful treatment of post-traumatic neuropathy.
A variety of dental and maxillofacial procedures carry the risk of post-traumatic neuropathy (PTN), making it difficult to estimate the overall incidence of iatrogenic trigeminal nerve damage specifically caused by dental and oral surgery
. The increased performance of dental procedures is one cause of the rising occurrence of trigeminal nerve injuries, which can lead to trigeminal sensory nerve neuropathy ranging from loss of sensitivity to severe neuropathic pain. Such complications can decrease the patient’s quality of life and sometimes lead to medico-legal action
This retrospective study was performed to examine the incidence and clinical characteristics of trigeminal nerve injuries at the Department of Oral and Maxillofacial Surgery, University Hospitals Leuven in Belgium (OMFS UZL), which offers orofacial PTN care. Focus was placed on delay and referral patterns in particular, since these are key factors for treatment success. Moreover, little evidence on referral delay has been described in the current literature. Prompt recognition of PTN, followed by appropriate referral and early treatment, gives the patient the best chance of improvement or recovery of sensory function in the damaged nerve branch.
Materials and methods
After receiving ethical approval from the Medical Ethics Committee of UMZ, the patient records from the Department of Oral and Maxillofacial Surgery were screened to identify patients seen for iatrogenic damage to branches of the trigeminal nerve during the period 2013–2014. Specifically, cases in which the causative sensory neuropathy was due to third molar removal, implant surgery, endodontic treatment, administration of local anaesthesia, or extraction of non-third molars were selected.
Information retrieved from the patient records included demographic data, details of the injury itself, the date of injury and duration, the referral type, the course of symptoms, and details of the local anaesthesia product used. The follow-up and progress of the neuropathy over the full duration of each patient’s neurosensory disturbance was observed. Cases of PTN that continued beyond 3 months were labelled persistent. Patients with PTN were grouped according to the causative procedure, nerve damaged, and referral type. Symptoms were categorized into three groups: loss of sensitivity, including hypoesthesia and anaesthesia (negative symptoms); no pain, encompassing any symptom or combination of symptoms not involving pain (positive symptoms, such as paresthesia and dysesthesia); and pain, either alone or as part of a combination of symptoms.
Results
Demographic characteristics
During the 2-year study period (2013–2014), a total of 8845 patients were seen at OMFS UZL, including 4080 in 2013 and 4765 in 2014. Among these patients, 53 (0.6%) consulted due to PTN of the trigeminal nerve caused by an iatrogenic injury incurred during one of the selected procedures. The patients who arrived at the department with iatrogenic nerve injuries were more commonly female (n = 36, 68%) than male (n = 17, 32%). The average age was 42.9 years (range 15–80 years) for female patients and 40.4 years (range 23–69 years) for male patients (overall average age 42.1 years).
Referral
For 15 patients, the causal procedure was performed at OMFS UZL (hereafter termed ‘internal referrals’). The remaining 38 patients consulted OMFS UZL after undergoing a procedure that caused iatrogenic PTN at an external centre (hereafter termed ‘external referrals’). Among the external referrals, 11 were referred directly by the clinician who performed the causative procedure (‘direct external referrals’), 16 patients were indirectly referred by another medical professional, such as a general practitioner or dentist (‘indirect external referrals’), and seven patients consulted the OMFS UZL on their own initiative; the referral route was unclear for the remaining four patients.
Delay
Among the 53 patients included, the average referral delay was 323 days (10 months), with a range of 1 day to 2383 days (6.5 years). Overall, 29% of patients attended OMFS UZL within 3 months, 49% within 6 months, and 63% within 1 year of injury. Among internal referrals, the average delay was 14 days, and all were seen within 3 months after the injury. The patterns for external referrals are displayed in Table 1. The average delay was 103 days (3 months) for direct external referrals and 478 days (1 year and 4 months) for indirect external referrals. Of the 11 direct external referrals, only five (45%) patients, including one patient injured during third molar extraction and four injured during the administration of local anaesthesia, consulted OMFS UZL within the critical period of 3 months. Furthermore, among the six patients with a neurosensory disturbance due to third molar extraction, only one (17%) was seen within the critical 3-month period (Table 1). In contrast, among the five patients with neurosensory disturbance due to local anaesthesia injections, four (80%) were seen during the critical period. The delay was even longer for indirect external referrals, with only five (31%) of the 16 patients seen within the critical period, including three referrals for external endodontic treatment-related PTN, one patient injured during third molar extraction, and one patient injured during the extraction of a non-third molar.
Table 1External referrals displayed according to the cause of injury and referral delay. All direct external referrals were seen within 1 year after the causative procedure. Indirect external referrals suffered up to 3 years of delay in referral to the University Hospitals Leuven.
The 53 patients who consulted OMFS UZL presented a total of 58 damaged nerves. The recorded injuries included 28 cases of inferior alveolar nerve (IAN) damage (53% of patients), 21 lingual nerve (LN) injuries (40% of patients), three cases of buccal nerve (BN) damage (6% of patients), and six cases of damage to the maxillary division (V2) of the trigeminal nerve or branches (11% of patients).
The most common cause of PTN was the extraction of third molars (24 cases, 45%), followed by local anaesthesia injuries (nine cases, 17%) and implant-related injuries (nine cases, 17%). Among the nine cases of local anaesthesia injury, five involved the use of articaine 4% and one was due to intra-osseous anaesthesia; the anaesthetic product utilized was not mentioned for the remaining three cases. PTN was related to non-third molar extraction in nine cases (9%) and to endodontic treatment in eight cases (6%). Stratification by causative procedure revealed that LN damage was more common than IAN damage in injuries related to third molar removal (14 LN vs. 9 IAN) and local anaesthesia (7 LN vs. 4 IAN).
Symptoms
Among the nine patients with implant-related injuries, seven complained of pain sensation with or without other symptoms (Fig. 1). In contrast, among the 24 cases of nerve damage due to third molar removal, 19 patients experienced pain-free altered sensation of the ipsilateral areas of the chin, lip, or tongue innervated by the IAN or LN. The remaining five patients suffering from PTN after third molar removal reported pain, either alone or in combination with other symptoms (Fig. 1).
Fig. 1Symptoms according to the causative procedure. Symptoms were categorized into three groups: loss = loss of sensitivity, including hypoesthesia and anaesthesia; no pain = any symptom or combination of symptoms not involving pain; pain = pain, either alone or as part of a combination of symptoms. (LA = local anaesthesia; ENDO = endodontic treatment; IP = implant surgery; M3 = third molar extraction; Non-M3 = extraction of teeth other than M3.).
Among the 28 patients with IAN injuries, 15 experienced painful symptoms, while 11 experienced pain-free altered sensation and only two experienced loss of sensation. In contrast, LN injuries were rarely reported as painful (2/21 cases) (Fig. 2).
Fig. 2Symptoms according to the injured nerve. Symptoms were categorized into three groups: loss = loss of sensitivity, including hypoesthesia and anaesthesia; no pain = any symptom or combination of symptoms not involving pain; pain = pain, either alone or as part of a combination of symptoms. (V2 = maxillary division of the trigeminal nerve; BN = buccal nerve; LN = lingual nerve; IAN = inferior alveolar nerve.)
Among the 53 patients, 32 (60%) suffered from persistent PTN (Fig. 3). All implant-related injuries were persistent. Sensory disturbances after third molar extraction were persistent in 14 of the 24 cases (58%), while the remaining 10 patients experienced improvement of their symptoms within 3 months after injury. Among the patients with injuries related to endodontic procedures or local anaesthesia, one in three suffered from persistent PTN.
Fig. 3Temporary and persistent injuries according to the causative procedure. Neurosensory disturbances lasting longer than 3 months were considered persistent. (Non-M3 = extraction of teeth other than M3; M3 = third molar extraction; IP = implant surgery; ENDO = endodontic treatment; LA = local anaesthesia.)
Of note, the population of patients referred to this specialist trigeminal PTN clinic does not fully represent the demographic characteristics of all patients undergoing the selected procedures. Thus the data presented here do not reflect the true incidence of injuries caused by these procedures
. The patients included in this study were most commonly female and middle-aged. Overall, the demographic characteristics of the study population are similar to those described previously, with several prior studies reporting that 61–77% of patients suffering from iatrogenic nerve injuries were female and a mean age ranging from 28 to 41 years
. This discrepancy between the sexes can be attributed to the general consensus that females are more likely to seek specialized treatment than males.
The time from injury to consultation at OMFS UZL varied within this patient population. Among all referred patients, 29% consulted OMFS UZL within 3 months after injury, 49% within 6 months, and 63% within 1 year. Similar delays have been reported by Robinson et al.
. Regarding the indirect external referrals, less than half consulted OMFS UZL within 3 months, and half of those seen within 3–6 months after injury had shown no improvement during prior follow-up (Table 1). Apart from the intrinsic delay involved with an indirect referral, this could be attributed in part to tertiary referrals. Among the late referrals with a delay of over 1 year, a substantial proportion were not delayed due to poor injury management; rather, the delay often reflected the complexity of the problem and the patient’s continuing quest for a solution. This is exemplified by the patients who consulted OMFS UZL with implant-related injuries, of whom five were indirectly referred by external medical professionals and four presented via an unknown party or self-referral. All three endodontic-related cases were indirectly referred within 1 month. In both implant surgery and endodontic treatment, when altered sensation persists after local anaesthesia has worn off, a rapid diagnosis followed by immediate referral is warranted
Among the 38 external patients, seven (almost 20%) were self-referrals. This could indicate that the patients had suboptimal relationships with their initial clinicians after the injury had occurred. Patients have stated that inadequate postoperative management and a lack of information are two of the four most bothersome factors relating to iatrogenic PTN
No standardized guidelines exist on the management of neurosensory deficits and most protocols are based on expert opinion. Various surgical and pharmacological treatments have been advocated for nerve injury with varying degrees of success, with physiological and pharmacological non-surgical therapies being the first-line postoperative care, followed by surgical evaluation and treatment
In a recent systematic review and meta-analysis, Kushnerev and Yates suggest that if no improvement is noted during follow-up over the first 3 months after injury, the patient should be referred to a surgeon to evaluate the need for exploration or surgical repair
. They advise that if ongoing improvement is noted during close follow-up, referral may be delayed until 6 months after injury. However, these recommendations are controversial, since central sensitization can already occur during the first 3 months post-injury
. Moreover, an exception to these general guidelines is that implant- and endodontic-related injuries should be assessed and repaired preferably within 12 hours, and with a maximum time window of 30–48 hours post-injury, to avoid persistent nerve damage
Ziccardi and Steinberg reviewed the literature to determine the effect of the timing of the surgical repair of trigeminal nerve damage on the recovery rate
. Some authors have reported timing guidelines, but evidence-based recommendations are scarce. Susarla et al. showed that patients referred early (<90 days post-injury) regained sensory function earlier and more frequently after surgical lingual nerve repair than late referrals (>90 days post-injury)
. Although the prevention of nerve injury remains the key issue, any suspected nerve injury should be referred immediately to a specialist centre with experience in trigeminal nerve injury repair and management.
Over the 2-year study period, less than 1% of patients presented with iatrogenic trigeminal PTN. The most common cause of injury was third molar extraction, followed by implant surgery and local anaesthesia, extraction of non-third molars, and endodontic treatment. Other researchers have reported similar findings, with third molar removal accounting for more than half of injuries, implant surgery and local anaesthesia accounting for between 11% and 21% of injuries, and endodontic-related injuries being the least common
. Among the cases of injury due to local anaesthesia, five involved the use of articaine 4%, which is considered more chemotoxic than anaesthetic products of lower concentration. However, these results should be interpreted with caution due to the potential for bias
. The findings concerning the persistence of iatrogenic nerve injuries are also similar to those reported previously in the literature. Libersa et al. reported that 75% of injuries caused by implant surgery were persistent, as well as 22% of injuries caused by third molar extractions and 15% of endodontic treatment-related injuries
. Different studies in the literature have reported varying incidences of IAN and LN injuries, but have not demonstrated any trends relating to the risk of IAN and LN injury during the causal procedures investigated. However, there is a consensus that the selected oral procedures pose the greatest risk of iatrogenic damage to these two mandibular divisions of the trigeminal nerve.
Symptoms varied according to the nerve injured, with IAN damage more commonly causing pain than LN damage (54% and 10%, respectively). In the literature, the frequency of pain sensation ranges from 15% to 44% after IAN injury and from 10% to 41% after LN injury
. It is difficult to explain this wide range of reported pain incidences. Multiple factors influence a person’s pain threshold, which can show substantial intra- and inter-individual variation. The increasing trend of pain reported by PTN patients could also be related to the high rates of pain reported in cases of PTN after implant surgery (78%), which is now performed more frequently than in the past. The present study found a high percentage of reported pain (67%) among cases of endodontic treatment-related injury, supporting prior reports that patients with endodontic treatment-related injuries have a high probability of developing severe neuropathic pain if not treated immediately
. However, only three such cases were included in this study, and larger sample sizes are needed to confirm this finding.
Among all cases of trigeminal PTN in this study, 60% were persistent. Fourteen (58%) of the 24 patients with an injury due to third molar removal developed a persistent neurosensory disturbance. All nine implant-related injuries were persistent, and none were referred within 3 months of injury. Nonetheless, there is limited evidence supporting a relationship between delayed referral and persistent PTN.
Despite sparse evidence to support interventions for patients with trigeminal PTN, guidelines for the management of trigeminal PTN exist; however, they remain poorly applied in clinical practice. The possibility of successful treatment is diminished by (1) late referral caused by delayed acknowledgement of an injury, (2) limited knowledge of symptoms, diagnosis, and treatment, (3) consultation of multiple clinicians, and (4) uncertainty regarding the optimal referral for different mechanisms of damage. Greater awareness about the prevention of iatrogenic nerve injury and early post-injury management, including timely and appropriate referral, is of paramount importance for reducing the incidence and persistence of iatrogenic trigeminal nerve injuries.
Acknowledgements
San Francisco Edit writing assistance (own payment).
References
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Complications in third molar removal: a retrospective study of 588 patients.
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