Ultrasound-Guided Inferior Alveolar Nerve Block in the Horse: Assessment of the Extraoral Approach in Cadavers.

Blinded techniques to desensitize the inferior alveolar nerve (IAN) include intraoral, angled, and vertical extraoral approaches with reported success rates of 100%, 73%, and 59%, respectively. It has not been determined whether an ultrasound-guided extraoral approach is feasible. Further, the fascicular nature of the inferior alveolar and lingual nerves of the horse has not been described. The objectives of this study were to describe a low-volume ultrasound-guided vertical extraoral inferior alveolar nerve block technique and to describe the fascicular nature of these nerves. An ultrasound-guided approach to the IAN was conducted with a microconvex transducer and an 18-G, 15-cm spinal needle using a solution containing iodinated-contrast and methylene blue dye. Accuracy was assessed by contrast visualized at the mandibular foramen on computed tomography (CT) and methylene blue dye staining of the nerves on gross dissection. Sections of inferior alveolar and lingual nerves were submitted for histological analysis. Assessment by CT and dissection determined success rates of 81.3% and 68.8%, respectively; 68.8% of injections had inadvertent methylene blue dye staining of the lingual nerve. Nerve histology revealed both the inferior alveolar and lingual nerves to be multifascicular in nature. Mean fascicle counts for the inferior alveolar and lingual nerves were 29 and 30.8, respectively. The technique is challenging and no more accurate than previously published blinded techniques. Any extraoral approach to the IAN is likely to also desensitize the lingual nerve.

Differences in control of parasympathetic vasodilation between submandibular and sublingual glands in the rat.

We examined blood flow in the submandibular gland (SMGBF) and sublingual gland (SLGBF) during electrical stimulation of the central cut end of the lingual nerve (LN) in the urethane-anesthetized rats using a laser speckle imaging flow meter. LN stimulation elicited intensity- and frequency-dependent SMGBF and SLGBF increases, and the magnitude of the SMGBF increase was higher than that of the SLGBF increase. The increase in both glands was significantly inhibited by intravenous administration of the autonomic cholinergic ganglion blocker hexamethonium. The antimuscarinic agent atropine markedly inhibited the SMGBF increase and partly inhibited the SLGBF increase. The atropine-resistant SLGBF increase was significantly inhibited by infusion of vasoactive intestinal peptide (VIP) receptor antagonist, although administration of VIP receptor antagonist alone had no effect. The recovery time to the basal blood flow level was shorter after LN stimulation than after administration of VIP. However, the recovery time after LN stimulation was significantly delayed by administration of atropine in a dose-dependent manner to the same level as after administration of VIP. Our results indicate that 1) LN stimulation elicits both a parasympathetic SMGBF increase mainly evoked by cholinergic fibers and a parasympathetic SLGBF increase evoked by cholinergic and noncholinergic fibers, and 2) VIP-ergic mechanisms are involved in the noncholinergic SLGBF increase and are activated when muscarinic mechanisms are deactivated.

Duloxetine in the treatment of burning mouth syndrome refractory to conventional treatment: A case report.

Patients with burning mouth syndrome (BMS) report burning sensation and pain involving the tongue and oral mucosa without any apparent medical or dental cause. The pathogenesis of this syndrome remains unclear and there is currently no standard treatment. BMS is, therefore, often misdiagnosed and its management is complex. This lack of clinical expertise may result in decreased health-related quality of life and increased psychological distress among patients with BMS. The present case report involves a 77-year-old female patient with BMS refractory to conventional treatment with nerve block and medication, who was successfully treated with duloxetine. Duloxetine may become a new therapeutic option in the management of BMS.

Should we be giving bilateral inferior alveolar and lingual nerve blocks for third molar surgery?

Extraction of mandibular third molars is one of the most common procedures in oral and maxillofacial surgery, and it is normal practice to extract both teeth at one visit under general anaesthesia. However, when both teeth are extracted under local anaesthesia, bilateral inferior alveolar and lingual nerve blocks are required, which is a subject of debate among clinicians. Much of the controversy surrounds the safety and efficacy of bilateral anaesthesia even though many surgeons use local anaesthetic solutions for perioperative and postoperative pain relief after day case general anaesthesia with no reports of unwanted effects. The evidence presented in this review explores published research for and against the use of unilateral and bilateral inferior alveolar and lingual nerve blocks.

Prolonged peripheral nerve blockade in patients using lithium carbonate.

Peripheral nerve blocks with local anaesthesia are routinely utilized in oral surgical procedures to achieve anaesthesia at the operative site. A number of local tissue factors as well as systemic conditions and medications may alter the onset, depth and duration of peripheral nerve blocks. This article describes two cases of extremely prolonged anaesthesia in patients treated with chronic oral lithium carbonate who had been administered inferior alveolar, lingual, long buccal, greater palatine and posterior superior alveolar nerve blocks with lidocaine with adrenaline for surgical removal of an upper and a lower third molar tooth. A possible relation with systemic lithium therapy and its probable mode of action are explored.

Autonomic and cardiovascular effects of pentobarbital anesthesia during trigeminal stimulation in cats.

Stimulation of the trigeminal nerve can elicit various cardiovascular and autonomic responses; however, the effects of anesthesia with pentobarbital sodium on these responses are unclear. Pentobarbital sodium was infused intravenously at a nominal rate and the lingual nerve was electrically stimulated at each infusion rate. Increases in systolic blood pressure (SBP) and heart rate (HR) were evoked by lingual nerve stimulation at an infusion rate between 5 and 7 mg·kg(-1)·h(-1). This response was associated with an increase in the low-frequency band of SBP variability (SBP-LF). As the infusion rate increased to 10 mg·kg(-1)·h(-1) or more, decreases in SBP and HR were observed. This response was associated with the reduction of SBP-LF. In conclusion, lingual nerve stimulation has both sympathomimetic and sympathoinhibitory effects, depending on the depth of pentobarbital anesthesia. The reaction pattern seems to be closely related to the autonomic balance produced by pentobarbital anesthesia.

Role of medullary GABA signal transduction on parasympathetic reflex vasodilatation in the lower lip.

In the orofacial area, noxious stimulation of the orofacial structure in the trigeminal region evokes parasympathetic reflex vasodilatation, which occurs via the trigeminal spinal nucleus (Vsp) and the inferior/superior salivatory nucleus (ISN/SSN). However, the neurotransmitter involved in the inhibitory synaptic inputs within these nuclei has never been described. This parasympathetic reflex vasodilatation is suppressed by GABAergic action of volatile anesthetics, such as isoflurane, sevoflurane, and halothane, suggesting that medullary GABAergic mechanism exerts its inhibitory effect on the parasympathetic reflex via an activation of GABA receptors. The aim of the present study was to determine the role of GABA(A) and GABA(B) receptors in the Vsp and the ISN in regulating the lingual nerve (LN)-evoked parasympathetic reflex vasodilatation in the lower lip. Under urethane anesthesia (1g/kg), change in lower lip blood flow elicited by electrical stimulation of the LN was recorded in cervically vago-sympathectomized rats. Microinjection of GABA (10 µM; 0.3 µl/site) into the Vsp or the ISN significantly and reversibly attenuated the LN-evoked parasympathetic reflex vasodilatation. Microinjection of the GABA(A) receptor-selective agonist muscimol (100 µM; 0.3 µl/site) or the GABA(B) receptor-selective agonist baclofen (100 µM; 0.3 µl/site) into the Vsp or the ISN significantly and irreversibly reduced this reflex vasodilatation, and these effects were attenuated by pretreatment with microinjection of each receptor-selective antagonists [GABA(A) receptor selective antagonist bicuculline methiodide (1mM; 0.3 µl/site) or GABA(B) receptor selective antagonist CGP-35348 (1mM; 0.3 µl/site)] into the Vsp or the ISN. Microinjection of these antagonists alone into the Vsp or the ISN had no significant effect on this reflex vasodilatation. In addition, microinjection (0.3 µl/site) of the mixture of muscimol (100 µM) and baclofen (100 µM) into the Vsp or the ISN also significantly reduced this reflex vasodilatation. These results suggest that medullary GABA signal transduction inhibits the parasympathetic reflex vasodilatation in the rat lower lip via GABA(A) and GABA(B) receptors in the Vsp and the ISN.

Distribution and absorption of local anesthetics in inferior alveolar nerve block: evaluation by magnetic resonance imaging.

PURPOSE: The aim of this study was to evaluate the distribution and absorption of local anesthetic solutions in inferior alveolar nerve block using magnetic resonance imaging. MATERIALS AND METHODS: Forty healthy volunteers were divided into 4 groups and injected with 1.5 mL for inferior alveolar nerve block and 0.3 mL for lingual nerve block. The solutions used for the different groups were 2% lidocaine, 2% lidocaine with 0.125 mg/mL epinephrine, 4% articaine with 0.006 mg/mL epinephrine, and 4% articaine with 0.012 mg/mL epinephrine. All subjects had axial T2-weighted and fat-suppressed images at 0, 60, and 120 minutes after injection. The localization, area, and intensity (signal characteristics) of the solutions were analyzed and onset and duration times of the anesthesia were recorded. RESULTS: There were no significant differences between groups with regard to the intensity and area of the solutions at 0, 60, and 120 minutes after injection, but differences were found within each group. CONCLUSIONS: No between-group differences were found on magnetic resonance imaging in the distribution and absorption of lidocaine with or without epinephrine and articaine with 0.006 and 0.012 mg/mL epinephrine. All solutions were noticeably absorbed at 120 minutes after injection.

Severe adverse reactions to dental local anaesthetics: prolonged mandibular and lingual nerve anaesthesia.

BACKGROUND: Prolonged anaesthesia may occur following dental local anaesthetic blocks. This paper reviews the possible mechanisms of injury. Direct injury to the nerve by the needle, although commonly thought to be the mechanism, is unlikely. It is much more likely that the injury is from neurotoxicity and/or interference with the vascularization of the nerve. METHODS: Estimation of the frequency of injury was complicated by the fact that although local anaesthetics are prescription-only (S4) drugs, they are supplied without prescription by dental supply houses. Unlike all other S4 drugs, there is no statutory requirement to record supply. The pharmaceutical and supply houses relied on that and 'commercial confidentiality' to not supply information. RESULTS: An informed estimate of 1 in 27 415 was made but this figure has wide confidence limits. Management of cases of prolonged anaesthesia following local anaesthetic injection is discussed. CONCLUSIONS: Patients who suffer this uncommon complication suffer considerable distress and feel injured, so care must be exhibited in their management. Specialist referral is recommended.

Area extent anaesthesia from buccal nerve block.

This study investigated the extent of complete anaesthesia from buccal nerve block. 40 healthy Thai patients (20 males; 20 females) requiring buccal nerve block for surgery were studied. After the buccal nerve was blocked, the buccal mucosa was explored using a sharp probe to map out the extent of anaesthesia. The operation was carried out after inferior alveolar and lingual nerve block. The extent of the anaesthesia was mainly from the retromolar area to the second molar, followed by the first molar to the second premolar, whilst the first premolar to the central incisor was the area least affected. An important finding of this study was that the anaesthetized extent of some patients extended to the anterior region on the same quadrant. This study showed the affected areas of buccal nerve anaesthesia extended through the buccal mucosa from the first premolar to the central incisor in some patients. It can serve as another informative indication for lower anterior surgery.

Paresthesias in dentistry.

Alterations to normal oral sensory function can occur following restorative and surgical dental procedures. Paresthesia is defined as an abnormal sensation, such as burning, pricking, tickling, or tingling. Paresthesias are one of the more general groupings of nerve disorders known as neuropathies. This article reviews the extent of this oral complication as it relates to dental and surgical procedures, with specific emphasis on paresthesias associated with local anesthesia administration. This review establishes a working definition for paresthesia as it relates to surgical trauma and local anesthesia administration, describes the potential causes for paresthesia in dentistry, assesses the incidence of paresthesias associated with surgery and local anesthesia administration, addresses the strengths and weaknesses in research findings, and presents recommendations for the use of local anesthetics in clinical practice.

Occurrence of paresthesia after dental local anesthetic administration in the United States.

BACKGROUND: Several studies have suggested that the likelihood of paresthesia may depend on the local anesthetic used. The purpose of this study was to determine if the type of local anesthetic administered had any effect on reports of paresthesia in dentistry in the United States. METHODS: The authors obtained reports of paresthesia involving dental local anesthetics during the period from November 1997 through August 2008 from the U.S. Food and Drug Administration Adverse Event Reporting System. They used chi(2) analysis to compare expected frequencies, on the basis of U.S. local anesthetic sales data, with observed reports of oral paresthesia. RESULTS: During the study period, 248 cases of paresthesia occurring after dental procedures were reported. Most cases (94.5 percent) involved mandibular nerve block. The lingual nerve was affected in 89.0 percent of cases. Reports involving 4 percent prilocaine and 4 percent articaine were 7.3 and 3.6 times, respectively, greater than expected (chi(2), P < .0001) on the basis of local anesthetic use by U.S. dentists. CONCLUSIONS: These data suggest that paresthesia occurs more commonly after use of 4 percent local anesthetic formulations. These findings are consistent with those reported in a number of studies from other countries. CLINICAL IMPLICATIONS: Until further research indicates otherwise, dentists should consider these results when assessing the risks and benefits of using 4 percent local anesthetics for mandibular block anesthesia.

Effect of lingual nerve block on burning mouth syndrome (stomatodynia): a randomized crossover trial.

Burning mouth syndrome (stomatodynia) is associated with changes of a neuropathic nature the main location of which, peripheral or central, remains unknown. A randomised, double-blind crossover design was used to investigate the effects of lingual nerve block on spontaneous burning pain and a possible correlation with the effects of topical clonazepam, the patient's response to a psychological questionnaire, and the taste and heat thresholds. The spontaneous burning was measured with a visual analogue scale (VAS) just before and 15 min after injection. The decreases in VAS score after lidocaine or saline injection were not significantly different (2.7+/-3.9 and 2.0+/-2.6, respectively; n=20). However, two groups of patients could be identified: in a "peripheral group" (n=10) the VAS decrease due to lingual nerve injection was 4.3+/-3.1cm after lidocaine and 0.9+/-0.3 cm after saline (p=0.02). In a "central group" (n=7), there were an increase in pain intensity score (-0.8+/-2.6 cm) after lidocaine and a decrease (1.5+/-3.0 cm) after saline (p=0.15). An increase in the hospital anxiety and depression (HAD) score and a decreased taste sensitivity and heat pain threshold of painful oral area were seen in patients compared with age-and-sex-matched controls (p<0.05). Topical clonazepam treatment tended to be more effective (p=0.07) and HAD score lower (p<0.03) in the peripheral than in the central group. These results suggest that the neuropathic disorder associated with stomatodynia may be predominantly peripheral, central or mixed depending on the individual. Topical application of clonazepam and HAD may serve as indicators of which mechanism is dominating.

Transient isolated lingual nerve neuropraxia associated with general anaesthesia and laryngeal mask use: two case reports and a review of the literature.

BACKGROUND: Transient, isolated lingual nerve neuropraxia is a rare complication following general anaesthesia. Reports implicate airway manipulation and we describe two new cases associated with laryngeal mask airway (LMA) and review the related English language literature. RESULTS: Unilateral numbness and loss of taste on the anterior tongue were the characteristic symptoms. Collation of literature data (median and range) with that from the new cases showed: patient age was 38 (20-61) years and female to male ratio was 1.2:1. Surgery time was 62.5 (20-150) min and symptom duration was 28 (7-120) days. CONCLUSION: Lingual neuropraxias reported have been transient and patients can be advised, despite disturbing symptoms, that recovery is anticipated in about 1 month. Lingual neuropraxia reports are becoming more frequent, perhaps associated with increasing LMA use. Research is recommended as modification to LMA cuff volume, pressure and/or position within the oral cavity might ameliorate the entity.

Effect of SB-750364, a specific TRPV1 receptor antagonist, on injury-induced ectopic discharge in the lingual nerve.

Abnormal neural activity generated at a site of nerve injury is thought to contribute to the development of dysaesthesia. Vanilloid receptor 1 (TRPV1), a transducer of noxious stimuli, may be involved in the initiation of this abnormal activity and could provide a useful therapeutic target. We investigated the effect of a specific TRPV1 antagonist (SB-750364) on injury-induced discharge in the lingual nerve. In 12 anaesthetised adult ferrets the left lingual nerve was sectioned and animals were allowed to recover for 3-7 days. In terminal experiments under general anaesthesia, the nerve was re-exposed and electrophysiological recordings made from spontaneously active axons in fine filaments dissected from the nerve central to both the injury site and the junction with the chorda tympani. SB-750364 was infused via the cephalic vein in order to achieve three increasing but stable systemic blood levels of the compound (0.3, 1.0 and 3.0 microM). Twenty-eight spontaneously active units were studied, with discharge frequencies ranging from 0.02 to 4.9 Hz. There was a significant reduction in spontaneous activity in 17 units (61%) at 1.0 microM or less of SB-750364 (p<0.01; Friedman test with Dunn's multiple comparisons). A further 4 units (14%) showed a significant reduction in activity at 3.0 microM (p<0.01). In the remaining 7 units (25%) the discharge was unaffected (p>0.05). These data show that the TRPV1 antagonist SB-750364 can reduce the level of spontaneous activity initiated in some axons following lingual nerve injury.