Hypoesthesia after IAN block anesthesia with lidocaine: management of mild to moderate nerve injury

Intranasal CRMP2-Ubc9 inhibitor regulates Na V 1.7 to alleviate trigeminal neuropathic pain

ABSTRACT

Dysregulation of voltage-gated sodium Na V 1.7 channels in sensory neurons contributes to chronic pain conditions, including trigeminal neuropathic pain. We previously reported that chronic pain results in part from increased SUMOylation of collapsin response mediator protein 2 (CRMP2), leading to an increased CRMP2/Na V 1.7 interaction and increased functional activity of Na V 1.7. Targeting this feed-forward regulation, we developed compound 194 , which inhibits CRMP2 SUMOylation mediated by the SUMO-conjugating enzyme Ubc9. We further demonstrated that 194 effectively reduces the functional activity of Na V 1.7 channels in dorsal root ganglia neurons and alleviated inflammatory and neuropathic pain. Here, we used a comprehensive array of approaches, encompassing biochemical, pharmacological, genetic, electrophysiological, and behavioral analyses, to assess the functional implications of Na V 1.7 regulation by CRMP2 in trigeminal ganglia (TG) neurons. We confirmed the expression of Scn9a , Dpysl2 , and UBE2I within TG neurons. Furthermore, we found an interaction between CRMP2 and Na V 1.7, with CRMP2 being SUMOylated in these sensory ganglia. Disrupting CRMP2 SUMOylation with compound 194 uncoupled the CRMP2/Na V 1.7 interaction, impeded Na V 1.7 diffusion on the plasma membrane, and subsequently diminished Na V 1.7 activity. Compound 194 also led to a reduction in TG neuron excitability. Finally, when intranasally administered to rats with chronic constriction injury of the infraorbital nerve, 194 significantly decreased nociceptive behaviors. Collectively, our findings underscore the critical role of CRMP2 in regulating Na V 1.7 within TG neurons, emphasizing the importance of this indirect modulation in trigeminal neuropathic pain.

Intranasal CRMP2-Ubc9 Inhibitor Regulates Na V 1.7 to Alleviate Trigeminal Neuropathic Pain

Dysregulation of voltage-gated sodium Na V 1.7 channels in sensory neurons contributes to chronic pain conditions, including trigeminal neuropathic pain. We previously reported that chronic pain results in part from increased SUMOylation of collapsin response mediator protein 2 (CRMP2), leading to an increased CRMP2/Na V 1.7 interaction and increased functional activity of Na V 1.7. Targeting this feed-forward regulation, we developed compound 194 , which inhibits CRMP2 SUMOylation mediated by the SUMO-conjugating enzyme Ubc9. We further demonstrated that 194 effectively reduces the functional activity of Na V 1.7 channels in dorsal root ganglia neurons and alleviated inflammatory and neuropathic pain. Here, we employed a comprehensive array of investigative approaches, encompassing biochemical, pharmacological, genetic, electrophysiological, and behavioral analyses, to assess the functional implications of Na V 1.7 regulation by CRMP2 in trigeminal ganglia (TG) neurons. We confirmed the expression of Scn9a , Dpysl2 , and UBE2I within TG neurons. Furthermore, we found an interaction between CRMP2 and Na V 1.7, with CRMP2 being SUMOylated in these sensory ganglia. Disrupting CRMP2 SUMOylation with compound 194 uncoupled the CRMP2/Na V 1.7 interaction, impeded Na V 1.7 diffusion on the plasma membrane, and subsequently diminished Na V 1.7 activity. Compound 194 also led to a reduction in TG neuron excitability. Finally, when intranasally administered to rats with chronic constriction injury of the infraorbital nerve (CCI-ION), 194 significantly decreased nociceptive behaviors. Collectively, our findings underscore the critical role of CRMP2 in regulating Na V 1.7 within TG neurons, emphasizing the importance of this indirect modulation in trigeminal neuropathic pain.

Pathophysiology of Post-Traumatic Trigeminal Neuropathic Pain

Trigeminal nerve injury is one of the causes of chronic orofacial pain. Patients suffering from this condition have a significantly reduced quality of life. The currently available management modalities are associated with limited success. This article reviews some of the common causes and clinical features associated with post-traumatic trigeminal neuropathic pain (PTNP). A cascade of events in the peripheral and central nervous system function is involved in the pathophysiology of pain following nerve injuries. Central and peripheral processes occur in tandem and may often be co-dependent. Due to the complexity of central mechanisms, only peripheral events contributing to the pathophysiology have been reviewed in this article. Future investigations will hopefully help gain insight into trigeminal-specific events in the pathophysiology of the development and maintenance of neuropathic pain secondary to nerve injury and enable the development of new therapeutic modalities.

Differential roles of NMDAR subunits 2A and 2B in mediating peripheral and central sensitization contributing to orofacial neuropathic pain

The spinal N-methyl-d-aspartate receptor (NMDAR), particularly their subtypes NR2A and NR2B, plays pivotal roles in neuropathic and inflammatory pain. However, the roles of NR2A and NR2B in orofacial pain and the exact molecular and cellular mechanisms mediating nervous system sensitization are still poorly understood. Here, we exhaustively assessed the regulatory effect of NMDAR in mediating peripheral and central sensitization in orofacial neuropathic pain. Von-Frey filament tests showed that the inferior alveolar nerve transection (IANX) induced ectopic allodynia behavior in the whisker pad of mice. Interestingly, mechanical allodynia was reversed in mice lacking NR2A and NR2B. IANX also promoted the production of peripheral sensitization-related molecules, such as interleukin (IL)-1β, tumor necrosis factor (TNF)-α, brain-derived neurotrophic factor (BDNF), and chemokine upregulation (CC motif) ligand 2 (CCL2), and decreased the inward potassium channel (Kir) 4.1 on glial cells in the trigeminal ganglion, but NR2A conditional knockout (CKO) mice prevented these alterations. In contrast, NR2B CKO only blocked the changes of Kir4.1, IL-1β, and TNF-α and further promoted the production of CCL2. Central sensitization-related c-fos, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba-1) were promoted and Kir4.1 was reduced in the spinal trigeminal caudate nucleus by IANX. Differential actions of NR2A and NR2B in mediating central sensitization were also observed. Silencing of NR2B was effective in reducing c-fos, GFAP, and Iba-1 but did not affect Kir4.1. In contrast, NR2A CKO only altered Iba-1 and Kir4.1 and further increased c-fos and GFAP. Gain-of-function and loss-of-function approaches provided insight into the differential roles of NR2A and NR2B in mediating peripheral and central nociceptive sensitization induced by IANX, which may be a fundamental basis for advancing knowledge of the neural mechanisms' reaction to nerve injury.

Visualization of Inferior Alveolar and Lingual Nerve Pathology by 3D Double-Echo Steady-State MRI: Two Case Reports with Literature Review

Injury to the peripheral branches of the trigeminal nerve, particularly the lingual nerve (LN) and the inferior alveolar nerve (IAN), is a rare but serious complication that can occur during oral and maxillofacial surgery. Mandibular third molar surgery, one of the most common surgical procedures in dentistry, is most often associated with such a nerve injury. Proper preoperative radiologic assessment is hence key to avoiding neurosensory dysfunction. In addition to the well-established conventional X-ray-based imaging modalities, such as panoramic radiography and cone-beam computed tomography, radiation-free magnetic resonance imaging (MRI) with the recently introduced black-bone MRI sequences offers the possibility to simultaneously visualize osseous structures and neural tissue in the oral cavity with high spatial resolution and excellent soft-tissue contrast. Fortunately, most LN and IAN injuries recover spontaneously within six months. However, permanent damage may cause significant loss of quality of life for affected patients. Therefore, therapy should be initiated early in indicated cases, despite the inconsistency in the literature regarding the therapeutic time window. In this report, we present the visualization of two cases of nerve pathology using 3D double-echo steady-state MRI and evaluate evidence-based decision-making for iatrogenic nerve injury regarding a wait-and-see strategy, conservative drug treatment, or surgical re-intervention.

Shape and anatomical relationship of the mental foramen to the mandibular premolars in an Indian sub-population: a retrospective CBCT analysis

Objectives

This study assessed the shape and anatomical relationship of the mental foramen (MF) to mandibular posterior teeth in an Indian sub-population.

Materials and Methods

In total, 475 existing cone-beam computed tomography records exhibiting 950 MFs and including the bilateral presence of mandibular premolars and first molars were assessed. Images were evaluated 3-dimensionally to ascertain the position, shape, and anatomical proximity of MFs to mandibular teeth. The position and shape of MFs were measured and calculated. The Pythagorean theorem was used to calculate the distance between the root apex of the mandibular teeth and the MF.

Results

MFs exhibited a predominantly round shape (left: 67% and right: 65%) followed by oval (left: 30% and right: 31%) in both males and females and in different age groups. The root apices of mandibular second premolars (left: 71% and right: 62%) were closest to the MF, followed by distal to the first premolars and mesial to the second premolars. The mean vertical distance between the MF and the nearest tooth apex calculated on sagittal sections was 2.20 mm on the right side and 2.32 mm on the left side; no significant difference was found according to sex or age. The distance between the apices of the teeth and the MF was ≥ 4 mm (left; 4.09 ± 1.27 mm and right; 4.01 ± 1.15 mm).

Conclusions

These findings highlight the need for clinicians to be aware of the location of the MF in treatment planning and while performing non-surgical and surgical endodontic procedures.

Molecular mechanisms of painful traumatic trigeminal neuropathy-Evidence from animal research and clinical correlates

Painful traumatic trigeminal neuropathy (PTTN) may occur following major craniofacial or oral trauma, or may be subsequent to relatively minor dental interventions. Following injury, pain may originate from a peripheral nerve, a ganglion, or from the central nervous system. In this review, we focus on molecular mechanisms of pain resulting from injury to the peripheral branch of the trigeminal nerve. This syndrome has been termed painful traumatic trigeminal neuropathy (PTTN) by the International Headache Society and replaces previous terms including atypical odontalgia, deafferentation pain, traumatic neuropathy and phantom toothache. We emphasize the scientific evidence supporting the events purported to lead to PTTN by reviewing the pathophysiology of PTTN based on relevant animal models. Additionally, we briefly overview clinical correlates and pathophysiological manifestations of PTTN.

Behavioral changes in calves 11 days after cautery disbudding: Effect of local anesthesia

Hot-iron disbudding results in painful burn wounds that take weeks to heal. Spontaneous behaviors indicative of pain are apparent in the immediate hours after disbudding, but whether they occur later in the healing process is unknown. To evaluate whether ongoing pain was present around the time the necrotic tissue loosens from the scalp, we tested the effect of administration of local anesthetic 11 d after the procedure. Disbudded female Holstein and Jersey calves (n = 24) were randomly assigned to receive an injection of local anesthetic (lidocaine) or saline at the cornual nerve on both sides of the head. We recorded the frequency of 8 behaviors for 75 min: head shakes, head rubs, head scratches, ear flicks, tail flicks, bucks/jumps/kicks, grooming, and transitions between standing and lying. Calves treated with lidocaine shook their heads less and tended to flick their ears less than calves administered saline, consistent with the effects of pain relief previously reported in the immediate hours after disbudding. These calves also rubbed their head against the sides of the pen more often, suggesting lidocaine suppressed wound protective behavior. Head shaking and head scratching became more common in the last 25 min compared with the first 50 min in calves treated with lidocaine, consistent with the return of sensation to the disbudding wounds. No treatment differences in the other behaviors were observed. These results suggest that calves experience ongoing pain 11 d after hot-iron disbudding, adding to a growing body of evidence that pain persists for weeks after the procedure.

Persistent idiopathic facial pain

Background

Persistent idiopathic facial pain (PIFP) is a chronic disorder recurring daily for more than two hours per day over more than three months, in the absence of clinical neurological deficit. PIFP is the current terminology for Atypical Facial Pain and is characterized by daily or near daily pain that is initially confined but may subsequently spread. Pain cannot be attributed to any pathological process, although traumatic neuropathic mechanisms are suspected. When present intraorally, PIFP has been termed ‘Atypical Odontalgia’, and this entity is discussed in a separate article in this special issue. PIFP is often a difficult but important differential diagnosis among chronic facial pain syndromes.

Aim

To summarize current knowledge on diagnostic criteria, differential diagnosis, pathophysiology and management of PIFP.

Methods

We present a narrative review reporting current literature and personal experience. Additionally, we discuss and differentiate the common differential diagnoses associated with PIFP including traumatic trigeminal neuropathies, regional myofascial pain, atypical neurovascular pains and atypical trigeminal neuropathic pains.

Results and conclusion

The underlying pathophysiology in PIFP is still enigmatic, however neuropathic mechanisms may be relevant. PIFP needs interdisciplinary collaboration to rule out and manage secondary causes, psychiatric comorbidities and other facial pain syndromes, particularly trigeminal neuralgia. Burden of disease and psychiatric comorbidity screening is recommended at an early stage of disease, and should be addressed in the management plan. Future research is needed to establish clear diagnostic criteria and treatment strategies based on clinical findings and individual pathophysiology.

Neuropathy of Trigeminal Nerve Branches After Oral and Maxillofacial Treatment

OBJECTIVE

To report the incidence of trigeminal neuropathy seen among new patients in a referral center within a period of 1 year (2013). The cause of damage, method of management and treatment outcome was assessed after 1-year follow-up.

MATERIALS AND METHODS

The records of all new patients visiting the oral and maxillofacial unit of the University hospital of Leuven in 2013 were screened for a history of damage to branches of the trigeminal nerve. The selected records were examined and the duration of nerve damage, received treatment as well as the outcome of the neuropathy after treatment was noted after 1-year follow-up.

RESULTS

56 patients (21 males, 35 females) from 7602 new patients had symptoms of damage to the trigeminal nerve branch. These symptoms persist in more than one-third of the patients [21/56 (37.5 %)] after 1-year follow-up. The least recovery is seen from oral surgery, implant placement, orthognathic surgery and tooth extraction. After 1 year 85 % (12/14) of neuropathic pain cases still have their symptoms as compared to 19 % (5/26) of patients with hypoesthesia.

CONCLUSION

This study shows a low incidence of nerve damage among the new patients presenting in oral and maxillofacial surgery clinic (<1 %); however, one-third of patients who sustain nerve damage never recover fully. Early diagnosis of the cause of neuropathy is essential. There is a need to objectively assess all patients with symptoms of trigeminal nerve damage before, during and after treatment.

Effect of a trial pharmaceutical solution on reversing sensations after using lidocain: An animal study

Introduction:

Local anesthesia has a paramount role in any branches of medical sciences specially dentistry. Soft tissue irritations and lips biting are adverse side-effects in some cases. This study tried out to represent a new pharmaceutical solution in returning sensations faster.

Materials and Methods:

Five New Zealand laboratory rabbits were anesthetized with 1 cc Ketamine and Xilosine intramuscularly in thigh site. Electrodes were attached to the palms and wrists. Then, 0.2 cc lidocain 2% was injected in forearm origin in order to block median proximal nerve in both forelegs. The nerves conduction study (NCS) was recorded before and after lidocain injection, plus 30 min and once again 1 h after calcium gloconate 10%, dextrose 50%, citric acid solution injection. The recorded data were analyzed using Wilcoxon test and using SPSS software (version 11.5) at significant level of 0.05.

Results:

The NCS of left and right forearms was 1.4 ± 1.35 mV and 0.48 ± 0.45 mV. According to the statistical test, there was no significant difference between two groups (P > 0.05).

Conclusion:

Calcium gloconate 10%, dextrose 50%, citric acid solution did not reverse the effect of anesthetic drugs. Possible reasons were pressure to the nerves, which were caused by drug volume, and low sample size.

Mental nerve paresthesia secondary to initiation of endodontic therapy: a case report

Whenever endodontic therapy is performed on mandibular posterior teeth, damage to the inferior alveolar nerve or any of its branches is possible. Acute periapical infection in mandibular posterior teeth may also sometimes disturb the normal functioning of the inferior alveolar nerve. The most common clinical manifestation of these insults is the paresthesia of the inferior alveolar nerve or mental nerve paresthesia. Paresthesia usually manifests as burning, prickling, tingling, numbness, itching or any deviation from normal sensation. Altered sensation and pain in the involved areas may interfere with speaking, eating, drinking, shaving, tooth brushing and other events of social interaction which will have a disturbing impact on the patient. Paresthesia can be short term, long term or even permanent. The duration of the paresthesia depends upon the extent of the nerve damage or persistence of the etiology. Permanent paresthesia is the result of nerve trunk laceration or actual total nerve damage. Paresthesia must be treated as soon as diagnosed to have better treatment outcomes. The present paper describes a case of mental nerve paresthesia arising after the start of the endodontic therapy in left mandibular first molar which was managed successfully by conservative treatment.

The enigma of the mental foramen as it relates to plastic surgery

The mental foramen position changes because of individual characteristics, and the knowledge of its location is paramount in a number of surgical procedures. This study's goal was to assess its position in relation to dentition and its symmetry in a Brazilian population. One hundred ninety-one dried jaws were divided in 3 groups according to the presence or absence of dentition and bone resorption in the foramen region. Standardized measurements of the distance between the foramen and anatomical references were made to establish its position and symmetry. The majority of the specimens studied belonged to white (74%) male (72%) individuals. The foramen most frequent position, using the teeth as reference, was between the premolars for both sexes (males, 41%; females, 60.3%). Most of the mandibles (56%) did not present symmetry between the right and left sides. Accessory foramina were found in 13.6% of jaws. The most frequent position of the mental foramen was between the premolars (position III of Tebo and Telford [Anat Rec 1950;107:61-66]), and they were predominantly asymmetric. The group with no teeth in the mental foramen area showed a reduction of the distance between the alveolar margin of the jaw and the mental foramen.

Pain sensation and postsurgical complications in posterior mandibular implant placement using ridge mapping, panoramic radiography, and infiltration anesthesia

Objectives. The aim of this study was to investigate intrasurgical and after surgical, pain and the incidence of after surgical alteration of sensation in the mandible and lower lip when placing implants in the posterior mandible using ridge mapping, panoramic radiography, and infiltration anesthesia. Methods. This was a longitudinal clinical study of healthy patients needing implant placement in the posterior mandible. After thorough examination and treatment plan using ridge mapping and panoramic radiography, all patients received dental implants under local infiltration anesthesia. The patients were then given a questionnaire to assess the pain during anesthesia and implant surgery. Change of sensation in the lower lip was evaluated by standard neurosensory examination tests at 7 days and 1 and 4 months. Prosthetic treatment was carried out 4 months postsurgery and the patients were followed for an average of 28.5 months afterwards. Results. A total of 103 implants were placed in 62 patients. Patients reported very minor pain during injection. No pain was reported during either implant placement or bone grafting procedures. No alteration of sensation in the mandible or lower lip was recorded postsurgery. Conclusion. In most cases, ridge mapping, panoramic radiography, and infiltration anesthesia are sufficient for posterior mandibular implant placement without pain or complications.