Assessment of lingual nerve functions after smoking cessation.

OBJECTIVE: Cigarette smoking is associated with a variety of oral diseases. A previous study showed a reduction of thermal sensitivity in the innervation area of the lingual nerve in smokers possibly caused by a degeneration of thermosensitive receptors as a consequence of smoking. The current study investigates somatosensory changes in ex-smokers. MATERIALS AND METHODS: Sensory functions in innervation areas of lingual nerve were investigated in 40 ex-smokers by psychophysical means. Functions of lingual nerve in 40 ex-smokers were compared to those in 40 smokers and 40 non-smokers. Subjects were investigated using quantitative sensory testing (QST, cold and warm detection, thermal sensory limen, heat and cold pain, and mechanical detection). RESULTS: Significant differences were found in both groups, ex-smokers and smokers compared to non-smokers. Cold (p < .001), warm (ex-smokers: p < .01; smokers: p < .001) detection thresholds and thermal sensory limen (p < .001) showed significantly lower sensitivity in ex-smokers and smokers in comparison to non-smokers. CONCLUSIONS: The lower temperature sensitivity of ex-smokers compared to that in non-smokers indicates a reduction of somatosensory function of the tongue, possibly caused by irreversible nerve degeneration associated with smoking. Influencing factors leading to sensory changes could be modulation of thermo-receptors, demyelination as well as a change of the epithelial structure.

Meta-analysis of the Incidence of Lingual Nerve Deficits After Mandibular Bilateral Sagittal Split Osteotomy.

INTRODUCTION: Bilateral sagittal split osteotomy is a relatively common maxillofacial surgical procedure. The most commonly reported complication is neurosensory disturbances (NSD). The inferior alveolar nerve is by far the most commonly affected but sporadic reports of NSD of the lingual nerve also exist. The aim of this meta-analysis is to estimate the incidence of lingual nerve NSD following bilateral sagittal split osteotomy. MATERIALS AND METHODS: A systematic search of the English literature was conducted in February 2015 including several databases and using numerous MeSH terms. Article selection was based on preset criteria. Then pertinent data were collected and the incidence of the complications was calculated. RESULTS: Three articles were included in the meta-analysis. Incidence rates ranged between 0.3% and 18% with a pooled incidence of 0.7%. DISCUSSION: Lingual nerve NSD is an infrequent complication of bilateral sagittal split osteotomy. Fortunately, the complication usually resolves within 1 year of the procedure.

Comparison of current perception threshold electrical testing to clinical sensory testing for lingual nerve injuries.

PURPOSE: We performed a retrospective study of lingual nerve injury assessment comparing the techniques of current perception threshold testing versus clinical sensory testing. PATIENTS AND METHODS: We designed and implemented a cross-sectional study and enrolled a patient sample with lingual nerve injuries presenting for treatment to the principal investigator. The predictor variables were clinical sensory testing modalities (ie, temperature, nocioception, vibration, 2-point discrimination, brush stroke, and von Frey monofilament perception). The primary outcome variable was the electrical current perception thresholds of the tongue dorsum (neurometer measurements at 5, 250, and 2,000 Hz). Comparisons were established with the ipsilateral affected and contralateral unaffected lingual nerve distributions. The associations between the clinical sensory testing and current perception threshold measurements were assessed using correlation coefficients, with the level of statistical significance set at P < .05. RESULTS: A total of 40 patients (13 males and 27 females) were included in the present study. The average age of these patients was 34 years (range 13 to 66). Significant correlations were observed between the electrical stimulation thresholds at 2,000 Hz and the 2-point discrimination, reaction to brushing, reaction to vibration, and von Frey fiber thresholds, between the electrical stimulation thresholds at 250 Hz to the nociceptive and thermal thresholds, and between the electrical stimulation thresholds at 5 Hz to thermal stimuli. CONCLUSIONS: The significant correlations observed in the present study indicate that current perception threshold can be a complementary or alternative tool in the assessment and evaluation of lingual nerve injuries.

Verification of nerve integrity after surgical intervention using quantitative sensory testing.

PURPOSE: The aim of this study was to apply a standardized Quantitative Sensory Testing (QST) approach in patients to investigate whether oral surgery can lead to sensory changes, even if the patients do not report any sensory disturbances. Furthermore, this study determines the degree and duration of possible neuronal hyperexcitability due to local inflammatory trauma after oral surgery. PATIENTS AND METHODS: Orofacial sensory functions were investigated by psychophysical means in 60 patients (30 male, 30 female) in innervation areas of infraorbital nerves, mental nerves and lingual nerves after different interventions in oral surgery. The patients were tested 1 week, 4 weeks, 7 weeks, and 10 weeks postoperatively. As controls for bilateral sensory changes after unilateral surgery, tests were additionally performed in 20 volunteers who did not have any dental restorations. RESULTS: No differences were found between the control group and the control side of the patients. Although not 1 of the patients reported paresthesia or other sensory changes postoperatively, QST detected significant differences between the control and the test side in the mental and lingual regions. Test sides were significantly less sensitive for thermal parameters (cold, warm, and heat). No differences were found in the infraorbital region. Patients showed significantly decreased pain pressure thresholds on the operated side. QST monitored recovery over time in all patients. CONCLUSIONS: The results show that oral surgery can lead to sensory deficits in the mental and lingual region, even if the patients do not notice any sensory disturbances. The applied QST battery is a useful tool to investigate trigeminal nerve function in the early postoperative period. In light of the increasing forensic implication, this tool can serve to objectify clinical findings.

Impaired somatosensation in tongue mucosa of smokers.

Smoking has been indicated as a risk factor for oral diseases and can lead to altered sense of taste. So far, the effects of sensory changes on the tongue are not investigated. In this study, quantitative sensory testing was used to evaluate somatosensory function in the lingual region. Eighty healthy volunteers were investigated (20 smokers, 20 non-smokers). Subjects were bilaterally tested in innervation areas of lingual nerves. Thresholds of cold and warm detection, cold and heat pain, and mechanical detection were determined. As control for systemic, extraoral effects of smoking, tests were additionally performed in 40 volunteers (20 smokers, 20 non-smokers) on the skin of the chin innervated by the mental branch of the trigeminal nerve. Cold (p < 0.001), warm detection thresholds (p < 0.001), and thermal sensory limen (p < 0.001) showed higher sensitivity in non-smokers as compared to smokers. Heat pain and mechanical detection, as well as all tests in the skin of the chin, showed no significant differences. The impaired temperature perception in smokers indicates a reduction of somatosensory functions in the tongue, possibly caused by nerve degeneration associated with smoking. Possible systemic effects of smoking do not seem to affect extraoral trigeminal branches.

Phonetic damage related to unilateral functional inhibition of the lingual nerve.

PURPOSE: The aim of this study was to analyze the effects of unilateral functional inhibition of the lingual nerve in phonetic function by perceptual and acoustic analyses of speech, which was recorded before and after neurosensory modification of the lingual nerve, and a comparison of results of these evaluations with a subject's self-perception. PATIENTS AND METHODS: The sample consisted of 10 volunteers who had the lingual nerve of the right side anesthetized. The analyzed recordings consisted of terms directly dependent on the tongue for production. In the perceptual analysis, pitch and loudness behaviors were observed, in addition to coarticulation and intelligibility. The acoustic analysis of 5 vowels and sibilant /s/ was realized. A questionnaire about the discomfort level in speech production was applied. RESULTS: Perceptual/auditive and acoustic parameters showed no significant differences. Although 3 informants declared some kind of discomfort related to speech production, they presented no acoustic or perceptual modification in sound quality. CONCLUSIONS: Although inhibition of sensory function of the lingual nerve generated considerable annoyance, there was no specific damage to phonetic function in the group under study, because no differences were observed in the quality of the speech of subjects after applying anesthesia to the lingual nerve.

Oral pain perception and taste in burning mouth syndrome.

BACKGROUND: Aim of this study was to investigate the effect of idiopathic burning mouth syndrome (BMS) on both, the pain perception within trigeminal lingual nerve distribution and gustatory sensitivity using capsaicin threshold test, and regional taste tests, respectively. METHODS: Pain thresholds for capsaicin were assessed using capsaicin-impregnated filter-paper strips. The strips were placed midline on the tongue tip for whole mouth testing with the mouth closed, and on the left or right edge of the extended anterior tongue for lateralized testing. Measures of gustatory function were obtained by validated "taste strips" test kit and electrogustometry. The tests were applied to 13 patients with BMS. Results were compared with those from 28 healthy subjects. RESULTS: Patients with BMS exhibited a decreased gustatory and somatosensory perception compared with healthy controls. These changes were found for lateralized tests but not for the whole mouth test procedure. Duration of disorder showed an effect on the capsaicin threshold, with patients being less sensitive to capsaicin exhibiting an increased duration of disorder. CONCLUSION: Both pain-related and gustatory sensitivies of the tongue are found to be decreased in BMS.

Transoral sialolitectomy combined with sialoendoscopy versus open submaxilectomy for the management of hilar lithiasis of the submandibular gland. / Sialolitectomía transoral combinada con sialoendoscopia versus submaxilectomía abierta para el manejo de litiasis hiliares de la glándula submaxilar.

INTRODUCTION: The treatment of salivary obstructive pathology by minimally invasive techniques has been an object of assessment by different studies for decades. Lithiasis at the level of the salivary duct will be the most frequent cause of obstruction, representing more than 50% of the pathology of the major salivary glands and almost 80% of these affecting the Wharton duct. MATERIAL AND METHODS: A prospective study comparing the results of combined transoral sialolitectomy (CTS) and open submaxillectomy techniques by cervicotomy in 2 groups of patients treated by lithiasis at the level of the hilum of the submaxillary gland. RESULTS: 22 patients were included in the study 16 (72.7%) were men and 6 (27.3%) were women, the average age was 54.41 years ± 12.75 (Min: 30/Max: 77). Regarding the variables associated with the disease: average lithiasis, size of the stone, hospital stay, lingual nerve alteration or complications for both techniques, differences were not found between both groups. There were only statistically significant differences in the average stay in favor of the CTS (P=.001). CONCLUSION: The minimally invasive approaches to the salivary ductal system, associated or not with sialoendoscopy, can be efficacy and can be associated with lower number of complications. The natural tendency should be aimed to gradually replacing open sialoadenectomy techniques, reserving its indication for the treatment of tumor pathology.

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.

Vanilloid receptor 1 (TRPV1) expression in lingual nerve neuromas from patients with or without symptoms of burning pain.

The lingual nerve, a peripheral branch of the trigeminal nerve, can be damaged during the surgical removal of lower third molar teeth. This damage can lead to the development of dysaesthesia, with some patients complaining of burning pain. We investigated the hypothesis that vanilloid receptor 1 (TRPV1), a transducer of noxious heat stimuli, was involved in the development of this burning pain. Neuroma specimens were obtained from patients undergoing microsurgical repair of a damaged lingual nerve. Repair was undertaken where there was little evidence of spontaneous recovery, 7-41 months after the initial injury. Preoperatively the incidence of dysaesthesia was determined by reported symptoms and using visual analogue scales (VAS) for pain, tingling and discomfort. Nine neuromas were studied from patients with burning dysaesthesia and six from patients with a sensory deficit but no dysaesthesia. Indirect immunofluorescence for protein gene product (PGP) 9.5 and TRPV1 was used to quantify the percentage area of PGP 9.5 positive neuronal tissue that also expressed TRPV1. The results showed no significant difference between the mean percentage area of TRPV1 expression in neuromas from patients with or without burning dysaesthesia. Furthermore, there was no correlation between TRPV1 expression and the VAS scores for pain, tingling or discomfort. However, if data from all patients was pooled, there was a negative correlation between the level of TRPV1 expression and the time after initial injury. These data do not rule out involvement of TRPV1 in the aetiology of burning dysaesthesia following lingual nerve injury but suggest that TRPV1 at the injury site does not play a primary role.

Evidence of chorda tympani dysfunction in patients with burning mouth syndrome.

BACKGROUND: More than two-thirds of patients with burning mouth syndrome (BMS) have altered taste sensation. The authors conducted a study to assess chorda tympani and trigeminal nerve function in these patients. METHODS: The study was composed of 48 patients; 22 were diagnosed as having BMS, 14 had burning symptoms related to other diseases and were diagnosed as having secondary burning mouth syndrome (SBMS), and 12 were healthy volunteers. The authors evaluated the electrical detection thresholds of the infraorbital and mental nerves and the electrical taste and electrical detection/tingling thresholds in the anterior two-thirds of the tongue for all patients. Electrical taste threshold is thought to be dictated by chorda tympani nerve function while electrical detection/tingling thresholds are regulated by trigeminal nerve function. RESULTS: The mean electrical taste/tingling detection thresholds ratio and the taste detection thresholds were significantly higher in patients with BMS than in patients with SBMS and in control subjects, indicating chorda tympani nerve dysfunction. Eighteen (82 percent) of the 22 patients with BMS demonstrated chorda tympani dysfunction (13 unilateral and five bilateral). CONCLUSIONS: Chorda tympani hypofunction may play an important role in BMS pathology. Unilateral hypofunction may be sufficient to produce generalized burning sensation exceeding the affected nerve area. CLINICAL IMPLICATIONS: Elevated taste detection threshold levels determined via electrogustatory testing and an elevated taste/tingling detection thresholds ratio may assist clinicians in the diagnosis of BMS. More studies are needed to validate these findings.

Effects of transitory lingual nerve impairment on speech: an acoustic study of sibilant sound /s/.

By measuring spectral characteristics of the sibilant /s/ this study investigated whether the reduced orosensory feedback caused by lingual nerve impairment affects the acoustics and articulation of sibilants. A further goal was to examine speakers' capability to compensate for the deviant control of the delicate movements required for the proper production of /s/ by experimentally modifying the function of the tongue in a way that reduces the necessary somatosensory information in articulation. Five healthy men with no speech, language or hearing abnormalities were enrolled. They produced the sibilant /s/ in a variety of phonetic contexts in two sessions: first in normal conditions and then with local anaesthesia of the right lingual nerve. From the speech samples, the spectral characteristics of the sibilant sound (i.e. the centre of gravity, standard deviation, skewness and kurtosis) were analysed acoustically. The results showed that the reduced tactile sensation has effects on the tongue function resulting in individual and variable spectral alterations. The variation between different speakers indicates individual ability to compensate for the effects caused by the sensory dysfunction of the tongue. It seems, therefore, that the compensatory mechanisms for speech production are highly speaker-dependent.

Simplifying the assessment of the recovery from surgical injury to the lingual nerve.

OBJECTIVE: To determine the sensitivity of conventional sensory assessment in monitoring lingual nerve recovery subsequent to third molar surgery and to evaluate if the assessment methods can be predictive of injury outcome. METHOD: A prospective case series of 94 patients presenting with lingual nerve injuries evaluated using objective mechanosensory and subjective methods during the recovery period of up to 12 months. RESULTS: The conventional tests were often unable to diagnose the presence of injury due to variability and they were not predictive of outcome. As a result of this study, we are able to identify patients more likely to have permanent rather than temporary lingual nerve injury at four to eight weeks post injury, using patient reported subjective function. The subjective function test also minimises the requirements for specialist training or equipment providing an ideal method for general dental practice. CONCLUSIONS: The development of these simple subjective tests may enable us to identify which patients are at risk of permanent lingual nerve injuries in the early post injury phase, thus allowing expeditious therapy when indicated.

Neurophysiologic and quantitative sensory testing in the diagnosis of trigeminal neuropathy and neuropathic pain.

This study investigated the utility of neurophysiologic examination and thermal quantitative sensory testing (QST) in the diagnosis of trigeminal neuropathy and neuropathic pain. Fifty-eight patients (14 men), 34 with sensory deficit within the inferior alveolar nerve (IAN) and 24 within the lingual nerve (LN) distribution, were included. Twenty-six patients (45%) reported neuropathic pain. Patients underwent blink reflex (BR) test and thermal QST; sensory neurography was done to the IAN patients. Results of clinical sensory testing were available from the charts of 48 patients revealing abnormal findings in 77% of the IAN and in 94% of the LN patients. The BR test was abnormal in 41%, neurography in 96%, and QST in 91% of the IAN patients. In the LN group, BR was abnormal in 33%, and QST in 100% of the patients tested. Neurophysiologic tests and QST verified the subjective sensory alteration in all but 2 IAN patients, both with old injuries, and 4 LN patients who did not undergo QST. When abnormal, thermal QST showed elevation of warm and cold detection thresholds (hypo/anesthesia), hypoalgesia was less marked, and heat allodynia was only occasionally present. Contralateral thermal hypoesthesia after unilateral injury was found in 14 patients. It was associated with the occurrence of neuropathic pain (P=0.016). Axonal Abeta afferent damage was less severe in the IAN patients with pain than in those without pain (P=0.012). Neurophysiologic tests and thermal QST provide sensitive tools for accurate diagnosis of trigeminal neuropathy and study of pathophysiological features characteristic to human neuropathic pain.

The effect of carbamazepine on injury-induced ectopic discharge in the lingual nerve.

Previous studies have shown that the development of ectopic activity from damaged axons following nerve injury may contribute to the aetiology of sensory disturbances, including dysaesthesia. Pharmacological manipulation of this activity could provide a method of treatment for this intractable condition. In this study we have investigated the effect of carbamazepine, an anti-convulsant, as it is known to have membrane stabilising properties. In eight anaesthetised adult ferrets the left lingual nerve was sectioned and the animals allowed to recover for 3 days. Then, in terminal experiments under general anaesthesia, the nerve was re-exposed and electrophysiological recordings were made from spontaneously active units in fine filaments dissected from the nerve proximal to the injury site. Carbamazepine in a modified cyclodextrin (hydroxypropyl-beta-cyclodextrin) was administered intravenously in increments, in order to achieve a progressively increasing systemic concentration, and serum levels were determined at the point that activity ceased. Twenty-one spontaneously active units were studied, with conduction velocities of 2.1-28.9 m s(-1) and discharge frequencies of 0.25-15.3 Hz. Spontaneous activity ceased in 13 units with a serum concentration of carbamazepine ranging from 3.5 to 8.4 mg/l, which was within the normal therapeutic range (4-12 mg/l). Four units ceased activity with carbamazepine levels above the therapeutic range (15.4-17.2 mg/ml), but the remaining four continued to discharge throughout the recording period. These data suggest that systemic carbamazepine can reduce the level of spontaneous activity initiated in some axons following lingual nerve injury.

Objective evaluation of iatrogenic lingual nerve injuries using the jaw-opening reflex.

The extent of reflex inhibition of masseteric electromyographic activity, after an electrical stimulus applied to lingual mucosa, was used as a test of the ability of the lingual nerve to conduct nerve impulses and this was compared with the results of standard clinical tests. Two groups of subjects were assessed: healthy subjects (n=10) and patients with lingual nerve injuries (n=17). The patients were tested 8-9 weeks after their injury and retested 6 months later when they were retrospectively allocated to either a temporary injury or a permanent injury group. The group measure of reflex inhibition after stimulation of the tongue on the opposite side to the injury was no different from the same measure in controls, whereas two-point discrimination did differ. Group measures of inhibition and of subjective function after stimulation on the side of the injury were significantly different from controls whereas light touch and two-point discrimination were not. There was good agreement between quantified masseteric inhibition and subjective function, but it was not possible at 8-9 weeks after the injury to differentiate between those that would recover and those that would be permanent.

New method for the objective evaluation of injury to the lingual nerve after operation on third molars.

Existing tests of function of the lingual nerve are either subjective or, when they elicit the jaw-opening reflex, are dependent on the cooperation of the subject. We report a study in 12 healthy volunteers and 12 patients with iatrogenic injury to the lingual nerve. A bite block (containing stimulating electrodes) was held between the teeth and the tongue was held on to the electrodes by suction. When the lingual nerve was intact, an electrical stimulus elicited brief inhibition of masseteric electromyographic activity. Local analgesia and iatrogenic injury to the lingual nerve altered nerve conduction and caused a reduction in reflex inhibition. Two methods, compatible with limited numbers of applications of the stimulus, were used to quantify responses. One used an indirect measurement of intervals between action potentials of muscle and the other used a measurement of rectified signals falling below the mean amplitude before and after the stimulus. Both methods gave values that correlated with subjective sensations. The first gave an estimate of the probability of defining major malfunction of the nerve objectively; the second gave a linear measurement that allowed recovery of the nerve to be followed.

Patterns of sensory recovery in the lingual nerve after surgical trauma.

OBJECTIVE: To examine the pattern of sensory recovery in the lingual nerve following injury, with an emphasis on qualitative changes. METHODS: Using data from one patient with prolonged dysaesthesia after surgical trauma to the lingual nerve, we correlated changes in perceived sensory function during recovery with results from qualitative and quantitative taste tests, and patient-reported quality-of-life measures. RESULTS: Recovery of quantitative taste testing as measured by automated electrogustometry, and qualitative whole of mouth taste testing, preceded perceptual recovery of taste. On the other hand, taste acuity as measured by regional qualitative taste testing tended to lag behind perceptual recovery. The pattern of recovery in the different qualitative taste sensations suggests variation in sensitivity of the nerve fibres responsible for carrying taste sensation, with the fibres relating to bitter and sour taste being the last to recover. CONCLUSION: To our knowledge, taking into account the limitations of this study, this picture of differential recovery of taste function in the lingual nerve has not been previously reported.

Ectopic neural activity from myelinated afferent fibres in the lingual nerve of the ferret following three types of injury.

Sensory disturbances following nerve injury may result from abnormal neural activity initiated at the injury site. We have studied the activity generated in the lingual nerve after three types of injury which may have variable potentials for the initiation of sensory disturbances. We have also compared the results with those found after damage to the inferior alveolar nerve, another branch of the trigeminal nerve, to determine whether differences in nerve fibre type or location affect the level of abnormal activity. In anaesthetised adult male ferrets the left lingual nerve was either ligated and cut distally, chronically constricted, or sectioned and allowed to regenerate. Following recovery periods of 3 days-6 months, single unit electrophysiological recordings were made from central to the injury site. After all three types of injury, some of the damaged axons at the injury site developed spontaneous activity (up to 36% of units) and mechanical sensitivity (up to 35% of units). There were significantly fewer spontaneously active units after ligation than after the other two types of injury but the level of mechanical sensitivity was not significantly different between the three types of injury. There was a significant increase in the spontaneous activity between 3 weeks and later recovery periods following both ligation and section injuries, and this late increase was not seen in our previous studies on the inferior alveolar nerve. Differences in the time-course of ectopic activity in adjacent branches of the trigeminal nerve suggest that the fibre types or anatomical relationships affect the outcome of injury.

The effect of nerve growth factor on functional recovery after injury to the chorda tympani and lingual nerves.

Nerve growth factor (NGF) is known to ameliorate central changes and enhance the regeneration of damaged axons in the early stages after peripheral nerve injury. We have assessed the long-term outcome of placing NGF at a nerve repair site by determining the functional characteristics of several groups of sensory afferent and autonomic efferent fibres in the cat lingual nerve. Six months after entubulation repair, with or without the incorporation of NGF, the recovery of secretomotor and vasomotor efferents was determined by recording salivary flow from the submandibular gland and temperature changes on the tongue surface, each evoked by stimulation of the repaired nerve. Electrophysiological recordings from the lingual and chorda tympani nerves proximal to the repair allowed characterisation of mechanosensitive, thermosensitive and gustatory afferents. When compared with data from uninjured control animals, both repair groups showed changes in spontaneous discharge and persistent reductions in conduction velocity, receptor sensitivity, proportion of gustatory units, and rate of salivary secretion. Comparisons between the outcome of repair with or without NGF revealed few differences. In the NGF group the conduction velocity of afferents in the lingual nerve was lower, and the level of spontaneous activity was higher. However, NGF appeared to preferentially enhance the regeneration of thermosensitive afferents, suggesting that it may play a role in determining the phenotypic profile of the regenerating axonal population. This suggests that future therapeutic enhancement of regeneration after peripheral nerve injury may require a combination of factors to encourage regeneration of specific fibre groups.