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Objectives MR neurography has the ability to detect and depict peripheral nerve injuries. This study evaluated the potential of MR neurography in the diagnosis of post-traumatic trigeminal neuropathy. Methods Forty-one participants prospectively underwent MR neurography of the lingual and inferior alveolar nerves using a 3D TSE STIR black-blood sequence. Two blinded and independent observers recorded the following information for each nerve of interest: presence of injury, nerve thickness, nerve signal intensity, MR neurography Sunderland class, and signal gap. Afterwards, the apparent nerve-muscle contrast-to-noise ratio and apparent signal-to-noise ratio were calculated. Clinical data (neurosensory testing score and clinical Sunderland class) was extracted retrospectively from the medical records of patients diagnosed with post-traumatic trigeminal neuropathy. Results Compared to neurosensory testing, MR neurography had a sensitivity of 38.2% and specificity of 93.5% detecting nerve injuries. When differentiated according to clinical Sunderland class, sensitivity was 19.1% in the presence of a low class injury (I to III) and improved to 83.3% in the presence of a high class (IV to V). Specificity remained unchanged. The area under the curve using the apparent nerve-muscle contrast-to-noise ratio, apparent signal-to-noise ratio, and nerve thickness to predict the presence of an injury was 0.78 ( p  < .05). Signal intensities and nerve diameter increased in injured nerves ( p  < .05). Clinical and MR neurography Sunderland scores positively correlated (correlation coefficient = 0.53; p  = .005). Conclusions This study shows that MR neurography can accurately differentiate between injured and healthy nerves, especially in the presence of a more severe nerve injury. Clinical relevance statement MR neurography is not only able to detect trigeminal nerve injuries, but it can also provide information about the anatomical specifications of the injury, which is not possible with clinical neurosensory testing. This makes MR neurography an added value in the management of post-traumatic trigeminal neuropathy. Key Points • The current diagnosis of post-traumatic trigeminal neuropathy is mainly based on clinical examination. • MR neurography is able to visualize and stratify peripheral trigeminal nerve injuries. • MR neurography contributes to the diagnostic process as well as to further decision-making.

The approximity of the inferior alveolar nerve (IAN) to the roots of lower third molars (M3) is a risk factor for the occurrence of nerve damage and subsequent sensory disturbances of the lower lip and chin following the removal of third molars. To assess this risk, the identification of M3 and IAN on dental panoramic radiographs (OPG) is mandatory. In this study, we developed and validated an automated approach, based on deep-learning, to detect and segment the M3 and IAN on OPGs. As a reference, M3s and IAN were segmented manually on 81 OPGs. A deep-learning approach based on U-net was applied on the reference data to train the convolutional neural network (CNN) in the detection and segmentation of the M3 and IAN. Subsequently, the trained U-net was applied onto the original OPGs to detect and segment both structures. Dice-coefficients were calculated to quantify the degree of similarity between the manually and automatically segmented M3s and IAN. The mean dice-coefficients for M3s and IAN were 0.947 ± 0.033 and 0.847 ± 0.099, respectively. Deep-learning is an encouraging approach to segment anatomical structures and later on in clinical decision making, though further enhancement of the algorithm is advised to improve the accuracy.

The purpose of this study was to evaluate a magnetic resonance imaging (MRI) protocol for direct visualization of the inferior alveolar nerve in the setting of mandibular fractures. Fifteen patients suffering from unilateral mandible fractures involving the inferior alveolar nerve (15 affected IAN and 15 unaffected IAN from contralateral side) were examined on a 3 T scanner (Elition, Philips Healthcare, Best, the Netherlands) and compared with 15 healthy volunteers (30 IAN in total). The sequence protocol consisted of a 3D STIR, 3D DESS and 3D T1 FFE sequence. Apparent nerve-muscle contrast-to-noise ratio (aNMCNR), apparent signal-to-noise ratio (aSNR), nerve diameter and fracture dislocation were evaluated by two radiologists and correlated with nerve impairment. Furthermore, dislocation as depicted by MRI was compared to computed tomography (CT) images. Patients with clinically evident nerve impairment showed a significant increase of aNMCNR, aSNR and nerve diameter compared to healthy controls and to the contralateral side (p < 0.05). Furthermore, the T1 FFE sequence allowed dislocation depiction comparable to CT. This prospective study provides a rapid imaging protocol using the 3D STIR and 3D T1 FFE sequence that can directly assess both mandible fractures and IAN damage. In patients with hypoesthesia following mandibular fractures, increased aNMCNR, aSNR and nerve diameter on MRI imaging may help identify patients with a risk of prolonged or permanent hypoesthesia at an early time.

Background Iatrogenic mandibular nerve damage resulting from oral surgeries and dental procedures is painful and a formidable challenge for patients and oral surgeons alike, mainly because the absence of objective and quantitative methods for diagnosing nerve damage renders treatment and compensation ambiguous while often leading to medico-legal disputes. The aim of this study was to examine discriminating factors of traumatic mandibular nerve within a specific magnetic resonance imaging (MRI) protocol and to suggest tangible diagnostic criteria for peripheral trigeminal nerve injury. Methods Twenty-six patients with ipsilateral mandibular nerve trauma underwent T2 Flex water, 3D short tau inversion recovery (STIR), and diffusion-weighted imaging (DWI) acquired by periodically rotating overlapping parallel lines with enhanced reconstruction (PROPELLER) pulse sequences; 26 injured nerves were thus compared with contra-lateral healthy nerves at anatomically corresponding sites. T2 Flex apparent signal to noise ratio (FSNR), T2 Flex apparent nerve-muscle contrast to noise ratio (FNMCNR) 3D STIR apparent signal to noise ratio (SSNR), 3D STIR apparent nerve-muscle contrast to noise ratio (SNMCNR), apparent diffusion coefficient (ADC) and area of cross-sectional nerve (Area) were evaluated. Results Mixed model analysis revealed FSNR and FNMCNR to be the dual discriminators for traumatized mandibular nerve ( p  < 0.05). Diagnostic performance of both parameters was also determined with area under the receiver operating characteristic curve (AUC for FSNR = 0.712; 95% confidence interval [CI]: 0.5660, 0.8571 / AUC for FNMCNR = 0.7056; 95% confidence interval [CI]: 1.011, 1.112). Conclusions An increase in FSNR and FNMCNR within our MRI sequence seems to be accurate indicators of the presence of traumatic nerve. This prospective study may serve as a foundation for sophisticated model diagnosing trigeminal nerve trauma within large patient cohorts.

Key Points This paper highlights some of the risks of causing nerve injury during planning, preparation and placement of mandibular implants. Highlights potential pitfalls and problems. Provides tips on how to prevent these implant related trigeminal injuries. Background The incidence of implant-related inferior alveolar nerve injuries (IANI) is steadily increasing within the UK population. Aims This study prospectively reviewed thirty cases (35% male; 65% female) of implant-related IANI seen in a specialist nerve injury clinic. Methods Neurosensory examinations were carried out to ascertain a quantifiable rating of the perception, pain profiling and functional difficulties. Data were analysed using SPSS software. Results Patients were aware of signing consent forms for the surgery in 11 cases and 8 of those felt they were not explicitly warned about nerve injury. Over 70% of patients were referred after six months post injury. Implant surgery planning involved intra-oral films only (30%), CBCT (10%), dental pantomograph (50%) and long cone peri-apical radiographs (48%). However, no radiographic evidence pre- or postoperatively was provided by the referring practitioner in 15% of cases. Intra-operative problems included bleeding and neurological symptoms. Proximity of the implant bed or implant to the inferior alveolar canal was evident radiographically. This showed contact with roof inferior alveolar nerve canal in 44% of cases, protrusion into the canal in 20% of cases, crossing of the canal in 20% cases and distance in one case, presumed to be due to local anaesthetic injury. All patients presented with a demonstrable neuropathy, which included neuropathic pain (50%) that interfered with speaking, kissing and socialising. Conclusions Consent, preoperative planning and appropriate referral were inadequate in provision of mandibular implants in this patient group. Recommendations have been proposed to improve practice and possible novel strategies are suggested for the prevention and improved management of these complications.

Background In general, trigeminal nerve injury is known as a potential risk of many surgical procedures in the oral cavity. Recent literature demonstrated that the risk of nerve injury is correlated with the experience of the surgeon. Therefore, the purpose of this study was to evaluate retrospectively the incidence of trigeminal nerve injuries in a teaching university setting. Material and methods From January 2000 to December 2009, a total of 1,559 patients underwent one intervention in the postcanine region of the mandible. Interventions included extractions, osteotomies, periradicular surgery, and implant surgery. In 2010, all 1,559 patient charts were screened. A record was made if trigeminal nerve injury was documented within the first month following surgery. These patients were re-evaluated. Results Documentation in the charts revealed that sensorial disturbance following surgery was seen in 42 patients (2.69 %). Among them, nine patients were clinically re-evaluated by the authors and 12 were interviewed by phone and observed by their dentist without any problems. Persistence of sensory disturbance was found in 5 of the 21 patients (0.32 %), and four of these five lesions were in the lingual nerve (0.25 %). Related to the type of surgery, most sensory disturbances were seen following periradicular surgery. Discussion Within the limitations of this study, it may be stated that oral surgery in an outpatient setting of a teaching university hospital resulted in very low rates of trigeminal nerve injuries. It may be concluded that adequately surveyed trainees can perform mandibular surgery without an increased risk of trigeminal sensorial disturbance.

The present study compared the use of cone beam computerized tomography (CBCT) images and intra-oral radiographs in the placement of final implant drills in terms of nerve damage to cadaver mandibles. Twelve cadaver hemimandibles obtained from 6 cadavers were used. Right hemimandibles were imaged using peri-apical radiography and left hemimandibles using CBCT, and the images obtained were used in treatment planning for the placement of implant drills (22 for each modality, for a total of 44 final drills). Specimens were dissected, and the distances between the apex of the final implant drill and the inferior alveolar neurovascular bundle and incisive nerve were measured using a digital calliper. Nerves were assessed as damaged or not damaged, and the Chi-square test was used to compare nerve damage between modalities ( P < 0.05). Nerve damage occurred with 7 final drills placed based on peri-apical radiography (31.8%) and 1 final drill placed using CBCT images (4.5%). The difference in nerve damage between imaging modalities was statistically significant ( P = 0.023), with CBCT outperforming intraoral film in the placement of final implant drills ex vivo. In order to prevent nerve damage, CBCT is recommended as the principal imaging modality for pre-implant assessment.

Introduction The results of prior studies assessing the accuracy of panoramic radiographic signs of intimate relationship between inferior alveolar nerve (IAN) and impacted molars are controversial. This may be partly due to inadequate objectivity and reliability of these radiographic signs, which is evaluated in the present study. Materials and methods Three hundred radiographs in which impacted third molar reached the superior border of the inferior alveolar canal or was superimposed by the canal were evaluated by three examiners independently, twice 3 months apart. Inter- and intra-examiner agreements were analyzed using kappa statistics. Results The inter-examiner agreement for all radiographic signs was poor ( k  < 0.2). The intra-examiner agreement for radiographic signs 2, 3, and 6 was poor with mean kappa values of 0.08, 0.00, and 0.09, respectively. Concerning the radiographic signs 4, 5, 7, and 8, the intra-examiner agreement was moderate with mean kappa values of 0.54, 0.49, 0.44, and 0.57, respectively. The mean kappa coefficient for the radiographic sign 1 yielded a good agreement ( k  = 0.65). Conclusions In the present study, the examiners were unable to reliably assess radiographic signs of intimate relationship between IAN and third molar, indicating that panoramic images should not be relied upon for preoperative prediction of IAN injury.

Purpose This study aimed to assess the reliability of multidetector computed tomography (MDCT) in determining the surgical risk of the inferior alveolar neurovascular bundle in extractions of third molars. Methods The sample comprised thirty-three individuals (63 third molars) who underwent preoperative evaluation by MDCT before extraction of impacted mandibular third molars. MDCT was used to determine the relationship between the roots of the third molars and the mandibular canal, and the course of the mandibular canal. Inferior alveolar nerve (IAN) exposure and the presence of hemorrhage were analyzed after removal of the teeth. IAN neurosensory deficit was recorded after 7 days. Clinical and MDCT findings were compared using Fisher’s exact test ( P  < 0.05). Results There was a statistically significant association between IAN exposure and the tomographic relationship between the roots of third molars and the mandibular canal ( P  = 0.015). Conventionally, all cases of IAN neurosensory deficit and hemorrhage occurred when the roots of the third molar presented in an at-risk relationship with the mandibular canal, however, this association was not statistically significant ( P  > 0.05). A statistically significant association was found between the lingual course of the mandibular canal and IAN exposure ( P  = 0.03). Conclusions MDCT is an effective tool for determination of the surgical risk to the inferior alveolar neurovascular bundle in extraction of mandibular third molars.

Brain-derived neurotrophic factor (BDNF), which is released due to nerve injury, is known to promote the natural healing of injured nerves. It is often observed that damage of mandibular canal induces local sclerotic changes in alveolar bone. We reported that peripheral nerve injury promotes the local production of BDNF; therefore, it was possible to hypothesize that peripheral nerve injury affects sclerotic changes in the alveolar bone. This study aimed to evaluate the effect of BDNF on osteogenesis using in vitro osteoblast-lineage cell culture and an in vivo rat osteotomy model. MC3T3-E1 cells were cultured with BDNF and were examined for cell proliferative activity, chemotaxis and mRNA expression levels of osteoblast differentiation markers. For in vivo study, inferior alveolar nerve (IAN) injury experiments and mandibular cortical osteotomy were performed using a rat model. In the osteotomy model, exogenous BDNF was applied to bone surfaces after corticotomy of the mandible, and we morphologically analyzed the new bone formation. As a result, mRNA expression of osteoblast differentiation marker, osteocalcin, was significantly increased by BDNF, although cell proliferation and migration were not affected. In the in vivo study, osteopontin-positive new bone formation was significantly accelerated in the BDNF-grafted groups, and active bone remodeling, involving trkB-positive osteoblasts and osteocytes, continued after 28 days. In conclusion, BDNF stimulated the differentiation of MC3T3-E1 cells and it promoted new bone formation and maturation. These results suggested that local BDNF produced by peripheral nerve injury contributes to accelerating sclerotic changes in the alveolar bone.