Mini-Skin Incision for Carotid Endarterectomy: Neurological Morbidity and Health-related Quality of Life

BACKGROUND

Cranial and cervical nerve (CCN) injury is recognized as a possible complication after carotid endarterectomy (CEA), which may result in minor local neurologic deficiencies and significant discomfort for the patient. The aim of this study is to investigate the effect of a mini-skin incision (<5 cm) on the CCN injury after CEA in comparison to standard longitudinal incision of 12-15 cm in a high volume center, and to evaluate health-related quality of life (HRQOL) outcomes in those patients who had undergone both types of the skin incision.

METHODS

From January 2013 to December 2019, 446 CEAs (47.3%) were performed through a standard neck incision of 12-15 cm (group A), while 496 (52.7%) were performed through a mini-skin incision (<5 cm) (group B). Sixty-two patients underwent standard neck incision on one side and mini-skin incision on the other side (subgroup B). The main outcome measures were stroke, death, CCN injuries, cervical hematoma rates, and reinterventions. The HRQOL was assessed at baseline and after 30 days using Medical Outcomes Study Short-Form 36 and 6 disease-specific modified Likert scales.

RESULTS

The stroke and death rate at 30 days was 1.12% in group A and 1% in group B (P = 1). The incidence of CCN deficits was significantly lower in group B (5.1%) in comparison to group A (13.4%) (P < 0.001). The cervical hematoma was more common after standard incision (4.9% vs. 1.2%, P = 0.02). HRQOL at 1 month showed that the outcomes after mini-skin incision were significantly better for less difficulty with eating/swallowing and neck pain (P < 0.01).

CONCLUSIONS

CEA through a small incision (<5 cm) may reduce CCN complications without additional perioperative neurologic risks. As validated by patients with bilateral disease who experienced both surgical techniques, mini-skin incision is also associated with better HRQOL at 1 month, particularly with regard to eating/swallowing and neck pain.

Cranial nerve outcomes in regionally recurrent head & neck melanoma after sentinel lymph node biopsy

OBJECTIVE

Characterize long-term cranial nerve (CN) outcomes following sentinel lymph node biopsy (SLNB) based management for head and neck cutaneous melanoma (HNCM).

METHODS

Longitudinal review of HNCM patients undergoing SLNB from 1997-2007.

RESULTS

Three hundred fifty-six patients were identified, with mean age 53.5 ± 19.0 years, mean Breslow depth 2.52 ± 1.87 mm, and 4.9 years median follow-up. One hundred five (29.4%) patients had SLNB mapping to the parotid basin. Eighteen patients had positive parotid SLNs and underwent immediate parotidectomy / immediate completion lymph node dissection (iCLND), with six possessing positive parotid non-sentinel lymph nodes (NSLNs). Fifty-two of 356 (14.6%) patients developed delayed regional recurrences, including 20 total intraparotid recurrences: five following false negative (FN) parotid SLNB, three following prior immediate superficial parotidectomy, two following iCLND without parotidectomy, and the remaining 12 parotid recurrences had negative extraparotid SLNBs. Parotid recurrences were multiple (4.9 mean recurrent nodes) and advanced (n = 4 extracapsular extension), and all required salvage dissection including parotidectomy. Immediate parotidectomy/iCLND led to no permanent CN injuries. Delayed regional HNCM macrometastasis precipitated 16 total permanent CN injuries in 13 patients: 10 CN VII, five CN XI, and one CN XII deficits. Fifty percent (n = 10) of parotid recurrences caused ≥1 permanent CN deficits.

CONCLUSIONS

Regional HNCM macrometastases and salvage dissection confer marked CN injury risk, whereas early surgical intervention via SLNB ± iCLND ± immediate parotidectomy yielded no CN injuries. Further, superficial parotidectomy performed in parotid-mapping HNCM does not obviate delayed intraparotid recurrences, which increase risk of CN VII injury. Despite lack of a published disease-specific survival advantage in melanoma, early disease control in cervical and parotid basins is paramount to minimize CN complications.

LEVEL OF EVIDENCE

4 (retrospective case series) Laryngoscope, 130:1707-1714, 2020.

Electrical stimulation-based nerve location prediction for cranial nerve VII localization in acoustic neuroma surgery

INTRODUCTION

Cranial nerve (CN) VII localization is a critical step during acoustic neuroma surgery because the nerve is generally hidden due to the tumor mass. The patient can suffer from Bell's palsy if the nerve is accidentally damaged during tumor removal. Surgeons localize CN VII by exploring the target area with a stimulus probe. Compound muscle action potentials (CMAPs) are elicited when the probe locates the nerve. However, false positives and false negatives are possible due to unpredictable tissue impedance in the operative area. Moreover, a single CMAP amplitude is not correlated with probe-to-nerve distance.

OBJECTIVES

This paper presents a new modality for nerve localization. The probe-to-nerve distance is predicted by the proposed nerve location prediction model.

METHODS

Input features are extracted from CMAP responses, tissue impedance, and stimulus current. The tissue impedance is calculated from the estimated resistance and capacitance of the tissue equivalent circuit. In this study, experiments were conducted in animals. A frog's sciatic nerve and gastrocnemius were used to represent CN VII and facial muscle in humans, respectively. Gelatin (2.8%) was used as a mock material to mimic an acoustic neuroma. The %NaCl applied to the mock material was used to emulate uncontrollable impedance of tissue in the operative area.

RESULTS

The 10-fold cross-validation results revealed an average prediction accuracy of 86.71% and an average predicted error of 0.76 mm compared with the measurement data.

CONCLUSION

The proposed nerve location prediction model could predict the probe-to-nerve distance across various impedances of the mock material.

Galanin protects against nerve injury after shear stress in primary cultured rat cortical neurons

The neuropeptide galanin and its receptors (GalR) are found to be up-regulated in brains suffering from nerve injury, but the specific role played by galanin remains unclear. This study aimed to explore the neuroprotective role of galanin after shear stress induced nerve injury in the primary cultured cortical neurons of rats. Our results demonstrated that no significant changes in cell death and viability were found after galanin treatment when subjected to a shear stress of 5 dyn/cm(2) for 12 h, after increasing magnitude of shear stress to 10 dyn/cm(2) for 12 h, cell death was significantly increased, while galanin can inhibit the nerve injury induced by shear stress with 10 dyn/cm(2) for 12 h. Moreover, Gal2-11 (an agonist of GalR2/3) could also effectively inhibit shear stress-induced nerve injury of primary cultured cortical neurons in rats. Although GalR2 is involved in the galanin protection mechanism, there was no GalR3 expression in this system. Moreover, galanin increased the excitatory postsynaptic currents (EPSCs), which can effectively inhibit the physiological effects of shear stress. Galanin was also found to inhibit the activation of p53 and Bax, and further reversed the down regulation of Bcl-2 induced by shear stress. Our results strongly demonstrated that galanin plays a neuroprotective role in injured cortical neurons of rats.

Cranial nerve monitoring during subpial dissection in temporomesial surgery

OBJECTIVE

Cranial nerves (CNs) crossing between the brainstem and skull base at the level of the tentorial hiatus may be at risk in temporomesial surgery involving subpial dissection and/or tumorous growth leading to distorted anatomy. We aimed to identify the surgical steps most likely to result in CN damage in this type of surgery.

METHODS

Electromyographic responses obtained with standard neuromonitoring techniques and a continuous free-running EMG were graded as either contact activity or pathological spontaneous activity (PSA) during subpial resection of temporomesial structures in 16 selective amygdalohippocampectomy cases. Integrity of peripheral motor axons was tested by transpial/transarachnoidal electrical stimulation while recording compound muscle action potentials from distal muscle(s).

RESULTS

Continuous EMG showed pathological activity in five (31.2%) patients. Nine events with PSA (slight activity, n = 8; strong temporary activity, n = 1) were recorded. The oculomotor nerve was involved three times, the trochlear nerve twice, the facial nerve once, and all monitored nerves on three occasions. Surgical maneuvers associated with PSA were the resection of deep parts of the hippocampus and parahippocampal gyrus (CN IV, twice; CN III, once), lining with or removing cotton patties from the resection cavity (III, twice; all channels, once) and indirect exertion of tension on the intact pia/arachnoid of the uncal region while mobilizing the hippocampus and parahippocampal gyrus en bloc (all channels, once; III, once). CMAPs were observed at 0.3 mA in two patients and at 0.6 mA in one patient, and without registering the exact amount of intensity in three patients.

CONCLUSION

The most dangerous steps leading to cranial nerve damage during mesial temporal lobe surgery are the final stages of the intervention while the resection is being completed in the deep posterior part and the resection cavity is being lined with patties. Distant traction may act on nerves crossing the tentorial hiatus via the intact arachnoid.

[Damage to craniocerebral nerves in reconstructive surgery of carotid arteries]

Reconstructive operations on aortic arch branches appear to be the most efficient method of preventing acute and chronic impairments of cerebral circulation. Iatrogenic lesions of the craniocerebral nerves deteriorate the course of the immediate, and especially the remote postoperative period, decreasing quality of life and social status of the patients after endured carotid reconstructions. The authors analysed herein the outcomes in a total of 562 patients after endured carotid artery surgery for atherosclerosis or pathological tortuosity. The authors examined the incidence rate, patterns and risk factor of damage to the craniocerebral nerves in all the patients. Comprehensive prevention of damage to the craniocerebral nerves was carried out in a total of 412 patients from the Study Group and was aimed at excluding or decreasing intensity of the eff ect of the eliminable risk factors. The proposed measures made it possible to decrease the rate of lesions of craniocerebral nerves from 18.7 to 6.9% and to substantially improve the postoperative patients' quality of life.

A novel model for examining recovery of phonation after vocal nerve damage

OBJECTIVES/HYPOTHESIS

Recurrent laryngeal nerve injury remains a dominant clinical issue in laryngology. To date, no animal model of laryngeal reinnervation has offered an outcome measure that can reflect the degree of recovery based on vocal function. We present an avian model system for studying recovery of learned vocalizations after nerve injury.

STUDY DESIGN

Prospective animal study.

METHODS

Digital recordings of bird song were made from 11 adult male zebra finches; nine birds underwent bilateral crushing of the nerve supplying the vocal organ, and two birds underwent sham surgery. Songs from all the birds were then recorded regularly and analyzed based on temporal and spectral characteristics using computer software. Indices were calculated to indicate the degree of similarity between preoperative and postoperative song.

RESULTS

Nerve crush caused audible differences in song quality and significant drops (P<0.05) in measured spectral and, to a lesser degree, temporal indices. Spectral indices recovered significantly (mean=43.0%; standard deviation [SD]=40.7; P<0.02), and there was an insignificant trend toward recovery of temporal index (mean=28.0%; SD=41.4; P=0.0771). In five of the nine (56%) birds, there was a greater than 50% recovery of spectral indices within a 4-week period. Two birds exhibited substantially less recovery of spectral indices and two birds had a persistent decline in spectral indices. Recovery of temporal index was highly variable as well, ranging from persistent further declines of 45.1% to recovery of 87%. Neither sham bird exhibited significant (P>0.05) differences in song after nerve crush.

CONCLUSION

The songbird model system allows functional analysis of learned vocalization after surgical damage to vocal nerves.

Curative-like analgesia in a neuropathic pain model: Parametric analysis of the dose and the duration of treatment with a high-efficacy 5-HT1A receptor agonist

High-efficacy activation of central 5-HT(1A) receptors by means of the recently discovered, selective 5-HT(1A) receptor ligand, F 13640 [(3-chloro-4-fluoro-phenyl)-[4-fluoro-4-{[(5-methyl-pyridin-2-ylmethyl)-amino]methyl}piperidin-1-yl]methanone, fumaric acid salt] causes an unprecedented, broad-spectrum analgesia in rat models of acute and chronic pain of nociceptive and neuropathic origin; it also is effective in conditions where opioids either are ineffective, induce analgesic tolerance, or elicit persistent hyperalgesia/allodynia. Inversely mirroring morphine's actions, F 13640's ("curative-like") analgesic effects persist after the discontinuation of treatment. Here, we examined the relationships, if any, between the dose and the duration of F 13640 treatment on the one hand, and the duration of persistent analgesia on the other. Rats received unilateral infraorbital nerve injury and developed allodynia - as assessed by an increased response to von Frey filament stimulation - within 24 days; thereafter, using osmotic pumps, rats were subcutaneously infused with F 13640 in two experiments. In one, a one-week infusion was instituted at 0.04-10-mg/day doses; in a second experiment, a 0.63-mg/day dose was implemented for a duration ranging from 1 to 56 days. These 250- and 56-fold variations of the dose and duration of treatment caused post-treatment, persistent analgesia for about 10 and 40 days, respectively. At least as much as dose, the duration of F 13640 treatment determines F 13640-induced persistent analgesia. Neuroadaptive modulations at pre- and postsynaptic, brain and spinal cord 5-HT(1A) receptors may be involved in the dynamical, dose- and time-dependent, pre-treatment rise and post-treatment decay of the analgesia induced by high-efficacy 5-HT(1A) receptor activation.

Cerebellopontine angle lipoma with extracranial extension

Lipomas of the cerebellopontine angle (CPA) are rare. A recent literature review identified only 98 reported cases of CPA lipoma. We present here a case of CPA lipoma in a 28-year-old woman who was admitted to our hospital with hearing loss in her left ear. Computed tomography scan and magnetic resonance imaging revealed a CPA mass lesion with extracranial extension around the left internal carotiol artery. The patient was operated on in the sitting position via a right suboccipital craniectomy. The intracranial part of the mass was partially removed. Histopathological examination resulted in a diagnosis of lipoma. Surgical treatment of CPA lipomas is rarely indicated, and the aim of surgery must be decompression of neural structures.

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.

Activation of c-Jun and ATF-2 in primate motor cranial nerve nuclei is not associated with apoptosis following axotomy

Nerve transection induces complex changes in gene regulation and expression that can have profound phenotypic effects on the fate of axotomized neurons. The transcription factors c-Jun and ATF-2 (activating transcription factor-2) are components of a regulatory network that mediates survival, regeneration, and apoptosis following axotomy in rodents. The activation and function of c-Jun and ATF-2 after nerve injury have not been examined in primates. Using a novel model of cranial nerve injury in baboons, we have examined the temporality of c-Jun activation (phosphorylation) in cranial nerve (CN) III and CN VI neurons and ATF-2 activation in CN VI neurons at 2, 4, and 9 days post-injury by immunohistochemistry. Furthermore, we have addressed whether the activation of these factors is associated with apoptosis by the TUNEL assay. We report that activated c-Jun is present in CN III and CN VI neurons ipsilateral to axotomy at 2, 4, and 9 days post-injury, but not in neurons contralateral to injury. Additionally, CN VI neurons ipsilateral to injury at 4 and 9 days contain activated ATF-2. Furthermore, no evidence of TUNEL reactivity was observed in either nucleus, regardless of laterality, at any of the examined time points. These findings suggest that activation of both c-Jun and ATF-2 does not mediate apoptosis in axotomized primate CN III and CN VI neurons at time points up to 9 days. This report serves as a basic inquiry into the neuronal response to cranial nerve injury in primates.

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.

Intraoperative Electrophysiologic Identification of the Nervus Intermedius

OBJECTIVE

Although enormous attention has been directed to the localization and preservation of the facial nerve in acoustic neuroma surgery, the nervus intermedius has largely been ignored. In this article, we describe a method for intraoperative electrophysiologic identification of the nervus intermedius.

STUDY DESIGN

Retrospective case review.

SETTING

University hospital (tertiary care center).

PATIENTS

Thirty-three patients who underwent intraoperative facial nerve monitoring for various cerebellopontine angle procedures. Recording electrodes were placed in the orbicularis oculi and orbicularis oris muscles. A constant-voltage stimulator was used to stimulate both the facial nerve and the nervus intermedius.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

Electrophysiologic response after stimulation of the nervus intermedius.

RESULTS

Stimulation of the nervus intermedius produced long-latency, low-amplitude response recorded only on the orbicularis oris channel. The response had a mean threshold 0.4 V, a mean latency of 11.1 ms, and a mean amplitude of 11.1 microV, all significantly different from responses to stimulation the facial nerve.

CONCLUSION

Knowledge of electrophysiologic features of nervus intermedius stimulation can help protect the facial nerve during cerebellopontine angle surgery. The surgeon must recognize that stimulation of the nervus intermedius can cause electromyographic activity in the facial nerve monitoring channels, but the main trunk of the facial nerve may lie in entirely different location in the cerebellopontine angle.

The effect of substance P on the spontaneous discharge from injured inferior alveolar nerve fibres in the ferret

Previous studies in our laboratory have shown that, at a site of inferior alveolar nerve (IAN) injury, there is a close association between the development of spontaneous neural activity and the accumulation of neuropeptides in the damaged axons. As this ectopic activity may contribute to the development of sensory disturbances after injury, we have examined further this relationship by determining the potential role of one neuropeptide, substance P (SP), in the initiation or modulation of the spontaneous discharge. Thirty-six adult ferrets were anaesthetised, the IAN sectioned, and the animals allowed to recover for 3-4 days. In terminal experiments under general anaesthesia, electrophysiological recordings were made from axons in fine filaments dissected from the nerve, central to the injury site. The effect of SP (2 x 10(-12), 10(-6) and 10(-4) M) and SP-antagonist (10(-4) M) applied either close-arterially or topically to the injury site was determined. Of the 101 units studied, 59% were spontaneously active. Close-arterial administration of SP increased the level of spontaneous discharge in a dose-dependent manner, with higher concentrations affecting more units (2 x 10(-12) M, 14%; 10(-6) M, 58%; 10(-4) M, 85%). SP also initiated spontaneous discharge in some previously silent units. Activity in 46% of units also increased in response to the SP-antagonist. None of the units responded to topical application of either SP or SP-antagonist. This study shows that SP can both initiate and modulate the spontaneous discharge from damaged axons, and this mechanism may be a potential therapeutic target in the management of sensory disturbances after nerve injury.

Nonevoked facial pain in rats following infraorbital nerve injury: a parametric analysis

Unilateral chronic constriction injury to the infraorbital nerve (IoN-CCI) induces an increase in face-grooming behavior that is not part of normal body grooming (i.e., "isolated face grooming"). Despite the validity of isolated face grooming as a measure of spontaneous neuropathic pain, variation between rats in postoperative face grooming has limited its usefulness. We examined whether performing bilateral rather than unilateral IoN surgery could induce a more stable face-grooming behavior. It was found that bilaterally ligated rats performed a significantly greater amount of isolated face grooming (approximately four- to fivefold) when compared with unilaterally ligated rats. However, this effect was accompanied by an equivalent increase in between-subjects variation. No significant difference in face grooming during body grooming was found between bilaterally and unilaterally ligated rats. Rats were observed in two different sizes of observation cages; also, in addition to the amount of time spent on face grooming, the number and average duration of the face-grooming episodes were recorded. The effects of IoN surgery are caused by increases in the number of episodes. The effects of cage size were mostly related to differences in episode duration; that is, rats performed longer face-grooming episodes in the small compared to the large observation cage. The present data confirm previous reports that isolated face grooming is a more sensitive measure than the total amount of face grooming. Bilateral IoN surgery does not seem to offer a more stable outcome measure; increases in isolated face grooming were, however, more clearly observed in the small cage.

[Neuronal regeneration and functional recovery following peripheral nervous system lesions]

INTRODUCTION

The complete traumatic sectioning of peripheral nerves start subcellular and molecular processes in the involved sensory and motor neurons that ends, in many cases, with a complete reinnervation of the sensory or muscular target. Nevertheless, the process is frequently disturbed, from a functional point of view, by the improper reinnervation of targets different from the original ones, a fact implying a partial or total lost of the involved sensory or motor function.

METHOD AND AIMS

Results obtained with several types of axotomy and of experimental anastomosis carried out with the different brainstem motor nerves are shown. The aim was to analyze the capabilities of the different brainstem centers to adapt their physiology to the functional characteristics of a new motor target, with respect to their affinity with the motor tasks carried out by the new target.

CONCLUSIONS

It is concluded that there is a gradient of functional adaptability in motoneurons to the role of new motor targets depending on their affinity in embryologic origins and functional properties. It is remarked the importance that, for a proper recovery of the lost function, have the compensatory processes started by synergistic motor systems not affected directly by the lesion.

Perceptual and instrumental evaluation of voice and tongue function after carotid endarterectomy

OBJECTIVE

Laryngeal and tongue function was assessed in 28 patients to evaluate the presence, nature, and resolution of superior recurrent laryngeal and hypoglossal nerve damage resulting from standard open primary carotid endarterectomy (CEA).

METHODS

The laryngeal and tongue function in 28 patients who underwent CEA were examined prospectively with various physiologic (Aerophone II, laryngograph, tongue transducer), acoustic (Multi-Dimensional Voice Program), and perceptual speech assessments. Measures were obtained from all participants preoperatively, and at 2 weeks and at 3 months postoperatively.

RESULTS

The perceptual speech assessment indicated that the vocal quality of "roughness" was significantly more apparent at the 2-week postoperative assessment than preoperatively. However, by the 3-month postoperative assessment these values had returned to near preoperative levels, with no significant difference detected between preoperative and 3-month postoperative levels or between 2-week and 3-month postoperative levels. Both the instrumental assessments of laryngeal function and the acoustic assessment of vocal quality failed to identify any significant difference on any measure across the three assessment periods. Similarly, no significant impairment in tongue strength, endurance, or rate of repetitive tongue movements was detected at instrumental assessment of tongue function.

CONCLUSIONS

No permanent changes to vocal or tongue function occurred in this group of participants after primary CEA. The lack of any significant long-term laryngeal or tongue dysfunction in this group suggests that the standard open CEA procedure is not associated with high rates of superior recurrent and hypoglossal nerve dysfunction, as previously believed.

[Neurophysiologic intraoperative monitoring to preserve cranial nerve function in base of skull surgery]

BACKGROUND

Neurophysiologic intraoperative monitoring (NIM) has gone through a renaissance since the advent of computer technology. Currently, both motor and sensory cranial nerves, including the IInd and VIIIth cranial nerves, can be intraoperatively controlled by means of small and mobile systems.

PATIENTS AND METHODS

In order to estimate the value of NIM using the new generation of computer systems, we analyzed the records of 379 patients who underwent skull base surgery since 1996. These comprised NIM of the IInd, VIIth, VIIIth cranial nerves in most cases and of the IXth, Xth, XIth, and XIIth cranial nerves in selected cases.

RESULTS

Whereas 72% of these cases demonstrated changes in the recorded intraoperative NIM signals, only 29% of them gave evidence of either clinical or electrophysiological neural function alterations during the postoperative follow-up.

CONCLUSIONS

NIM is the only available system capable of providing the surgeon with instant intraoperative neural status-related feedback.

Effect of dexamethasone and dipyrone on lingual and inferior alveolar nerve hypersensitivity following third molar extractions: preliminary report

AIMS

To study the effect of dexamethazone and dipyrone on sensory changes in the innervation territories of the inferior alveolar, infraorbital, and lingual nerves caused by third molar extractions.

METHODS

Fourteen patients (8 men and 6 women) were divided randomly into 2 groups. The first group received dipyrone preoperatively, while the second group received dipyrone and dexamethazone preoperatively. All patients in the study received a prophylactic preoperative dose of amoxicillin (500 mg) as well as dipyrone postoperatively. In all patients, a single mandibular third molar was removed, while in 2 patients the contralateral third molar was removed at a subsequent time. Electrical detection thresholds were assessed in the inferior alveolar, lingual, and infraorbital nerve regions prior to surgery and 2 and 8 days following surgery. The level of perioperative pain, difficulty of extraction, and distance of molar root apices from the inferior alveolar nerve canal were also assessed.

RESULTS

Patients who received only dipyrone had significantly reduced lingual and inferior alveolar nerve electrical detection thresholds 2 days after surgery, which returned to nearly baseline values by the eighth day postoperatively. In patients who received dexamethasone, no significant reduction in the electrical detection threshold was found.

CONCLUSION

Preoperative treatment with dexamethasone and dipyrone but not dipyrone alone prevents sensory hypersensitivity following third molar extraction.

Central neuronal changes after nerve injury: neuroplastic influences of injury and aging

Peripheral nerve injury produces a hyperexcitability of primary afferents and neurons in the spinal cord that is considered important in the development of nerve injury-induced pain. The authors recently developed a nerve injury model in the trigeminal region of the rat to study the neuronal mechanism of neuropathic pain in the trigeminal system. The escape thresholds to mechanical stimulation applied to the whisker pad area were significantly lower in rats with an inferior alveolar nerve (IAN) transection than those evoked from the contralateral, sham-operated whisker pad. Also, background activity and mechanically evoked responses in infraorbital nerve (ION) afferents and hyperpolarization-activated current (Ih) in trigeminal ganglion ION neurons were increased following IAN transection. Background activity and mechanically evoked responses of wide dynamic range (WDR) neurons in trigeminal subnucleus caudalis on the ipsilateral side relative to the transection were also significantly increased after the operation. A large number of cells expressed c-Fos-like immunoreactivity in the caudal medulla and upper cervical spinal cord following non-noxious mechanical stimulation of the faces of rats with IAN transection. The effect of aging on spinal dorsal horn neurons and the involvement of nerve injury in producing abnormal pain sensation in rats with advancing age were also studied. The incidence of licking behavior in response to noxious radiant heat stimulation of the hind paw was lower in the aged rats than in younger adults, but paw withdrawal latency was shorter and the activities of spinal dorsal horn neurons were higher in the aged rats. Furthermore, the descending inhibitory systems were impaired in the aged rats. These observations suggest that the changes in neuronal activity in the aged rats likely corresponded to the changes observed in the rat model of peripheral nerve injury.

Bilateral occipital neuropathy as a rare complication of positioning for thyroid surgery in a morbidly obese patient

BACKGROUND

Peripheral neuropathies in various locations are described as complications after anesthesia and surgery. This is the first case report of temporary bilateral occipital neuropathy from positioning for thyroid surgery in a morbidly obese patient.

METHODS

A 48-year-old women with a history of depression, fibro-myalgia, asthma, sleep apnea, diabetes mellitus and morbid obesity (127 kg, 165 cm) underwent 4 hours anesthesia with propofol/remifentanil without muscle relaxation for thyroid surgery. The neck with a very low range of motion secondary to fat tissue needed to be extended to facilitate surgery as much as possible. The head was carefully padded and there were no episodes of hypotension or hypoxemia throughout the case or in the PACU. At post op day 1 she complained of bilateral numbness in the distribution area of both greater occipital nerves. On post op day 2 tingling sensations and improvement of numbness was noticed. The patient recovered without residual symptoms after 6 weeks.

CONCLUSION

Pressure or shear stress to the nerve, hypoperfusion or metabolic disturbances are discussed as the leading etiology of nerve damage during surgery in the literature. Pressure from fat tissue during prolonged head extension for surgery seems to be the cause in this case and should therefore be avoided whenever possible in morbidly obese patients, especially when other risk factors for neuropathy like diabetes are present.

Intraoperative cranial nerve monitoring

The purpose of intraoperative monitoring is to preserve function and prevent injury to the nervous system at a time when clinical examination is not possible. Cranial nerves are delicate structures and are susceptible to damage by mechanical trauma or ischemia during intracranial and extracranial surgery. A number of reliable electrodiagnostic techniques, including nerve conduction studies, electromyography, and the recording of evoked potentials have been adapted to the study of cranial nerve function during surgery. A growing body of evidence supports the utility of intraoperative monitoring of cranial nerve nerves during selected surgical procedures.

Mechanosensory and thermosensory changes across the border of impaired sensitivity to pinprick after mandibular nerve injury

PURPOSE

The study goal was to determine how sensory function varies across the border of impaired sensitivity to pinprick in patients with mandibular nerve injuries.

PATIENTS AND METHODS

Borders of decreased sensitivity to pinprick were mapped in 15 patients who reported altered sensation. Four mechanoreceptive, 2 thermoreceptive, and 2 thermonociceptive functions were studied at 5 sites separated by 0.6 cm across the border. The tests were repeated to evaluate day-to-day consistency in the pattern of variation for each sensory measure.

RESULTS

The estimates of sensory function were not found to vary in a systematic manner from outside to inside the pinprick-impaired area for all patients for any of the 8 tests. However, for every test, some patients exhibited large variations. On average, the magnitudes of loss in contact detection, subjective intensity of light touch, and direction discrimination were greatest; the magnitudes of loss in 2-point perception and in heat and cold pain perception were least. Some patients provided no evidence of impairment on certain tests. For some patients, the estimates suggested increased sensitivity within the pinprick-impaired area (eg, to noxious cold stimuli).

CONCLUSIONS

Although certain patients exhibit impairment, there is no obligatory loss in light touch, 2-point perception, direction discrimination, or temperature perception across the border of decreased sensitivity to pinprick. The differences among patients suggest that the data from individual patients should be evaluated in clinical studies and in clinical practice. Researchers should not rely solely on average values and summary statistics.

Increased expression of mRNAs for microtubule disassembly molecules during nerve regeneration

The mRNA expression of the microtubule disassembly molecules (SCG10, stathmin, SCLIP and RB3) in response to nerve injury was examined using a rat hypoglossal nerve injury model. After nerve injury prominent increase in mRNA expression of SCG10, stathmin and RB3 was observed, while only slight increase in SCLIP mRNA was observed in injured motor neurons. The increase in SCG10 and RB3 mRNA expression was quicker than that of stathmin and SCLIP. All the elevated signals decreased gradually to control levels by 4 weeks after nerve injury.

Behavioral and electrophysiological consequences of deafferentation following chronic constriction of the infraorbital nerve in adult rats

Deafferentation of the hind paw following sciatic nerve injury results in behavioral changes, such as autotomy, suggestive of persistent, spontaneous pain. The effects of deafferentation involving trigeminal nerves have, however, received less attention. Here, alterations in trigeminal ganglion neuronal activity and mechanically evoked and spontaneous behavior were studied in adult rats after a chronic constriction injury of the infraorbital nerve (ION). Compared to sham-operated rats, most rats with ION damage were unresponsive to mechanical stimulation of the mystacial vibrissae up to 56 days after surgery. Increased facial grooming was observed only in rats with chronic ION constriction 10 days after surgery. Free-ranging behavior was similar to that of sham-injury animals. In contrast, increases in the number of spontaneously active trigeminal ganglion neurones were observed in those rats with ION injuries at both 3 and 56 days. These data suggest that chronic constrictive injuries of the ION resulting in prolonged loss of low-threshold input from the periphery lead to only transient behavioral changes, despite the presence of spontaneous activity in trigeminal sensory neurones.

Endothelin-converting enzymes and endothelin receptor B messenger RNAs are expressed in different neural cell species and these messenger RNAs are coordinately induced in neurons and astrocytes respectively following nerve injury

There is some evidence that endothelins may be a signal mediator between neuronal and glial cells, at least in some regions of the brain. To evaluate this possibility, the localization of messenger RNAs for endothelin-converting enzymes and endothelin receptor B in the rat brain were examined using in situ hybridization histochemistry. The messenger RNAs for endothelin-converting enzyme-1 and endothelin-converting enzyme-2 were expressed mainly in neurons located in various brain regions, whereas the messenger RNA for endothelin receptor B was mainly localized in the astrocytes located throughout the brainstem, Bergmann glia, choroid plexus and ependymal cells. The localization patterns of endothelin-converting enzyme and endothelin receptor B messenger RNAs were strikingly different. For instance, in the cerebellum, endothelin-converting enzyme-1 messenger RNA was localized in Purkinje cells, and endothelin-converting enzyme-2 mRNA was expressed in Purkinje cells and granule cells. On the other hand, endothelin receptor B messenger RNA was expressed in Bergmann glia and the astrocytes located in the granule cell layer. This suggests that final cleavages of big endothelins are performed on neuronal cells, and the major target of the processed endothelins could be astrocytes, which express endothelin receptor B most abundantly in the brain. Since evidence that endothelin is implicated in brain injury has also accumulated, we examined whether the expressions of endothelin-converting enzymes and endothelin receptor B are regulated by nerve injury. Following hypoglossal nerve injury, expression of messenger RNA for endothelin-converting enzymes-1 and -2 and endothelin receptor B was enhanced in the injured motor neurons and astrocytes respectively. The up-regulation of these messenger RNAs was also confirmed by a reverse transcription-polymerase chain reaction based strategyThese results lead us to suggest that endothelin can be an inducible intercellular mediator between injured neurons and astrocytes in response to nerve injury.

Neuromuscular rehabilitation and electrodiagnosis. 2. Localized peripheral neuropathy

This self-directed learning module highlights advances in diagnosis and treatment of focal injuries to peripheral and cranial nerves. It is part of the chapter on neuromuscular rehabilitation and electrodiagnosis in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. Nerve conduction and electromyographic techniques are employed as extensions of the physician's senses in clinical examination and diagnosis. The findings are used to plan treatment, and to predict and measure outcomes. Electrodiagnosis and medical and surgical treatments of nerve injuries are discussed in light of the managed-care utilization review of services.

Taste perception after lingual nerve repair

PURPOSE

This retrospective study evaluates patients' perception of taste after lingual nerve injury and repair. It is hypothesized that return of taste is a distinct neurophysiologic phenomenon related to specialized taste physiology and it does not correlate with specific, objective sensory return.

PATIENTS AND METHODS

During 1995 to 1996, 30 patients underwent microsurgical repair of lingual nerve injuries. Of these, 22 patients met the inclusion criteria for this study. Chart review documented the date and cause of injury, sensory examination, injury classification, procedures, operative findings, and postoperative sensory examination. A telephone questionnaire addressed whole mouth taste perception with normal daily eating. The questions asked were: 1) Was your sense of taste changed or abnormal after your nerve injury? and 2) Did your sense of taste recover after nerve repair?

RESULTS

All patients had a postinjury, prerepair sensory deficit on levels A, B, and C testing: neurotmesis (n = 14); and axonotmesis (n = 8). The mean time from injury to repair was 16 weeks (range, 3 to 41 weeks). Operative findings confirmed 12 Sunderland Class IV (partial transection) injuries and 10 Class V (complete transection) injuries. All patients had primary microsurgical repair without a nerve graft or entubulization. Postoperatively, 18 patients showed marked improvement in sensory testing at levels A, B and C, and 4 patients showed no significant change. A telephone interview regarding whole mouth taste perception indicated that 20 of 22 patients perceived changed, abnormal taste postinjury and pre-repair. Two patients reported normal taste perception. Postrepair, only 7 of 20 patients reported an increase or return of taste perception to a more normal level. The mean follow-up time was 80 weeks.

CONCLUSION

Most patients (20 of 22) with lingual nerve injuries in this study perceived whole mouth taste as abnormal. After nerve repair, although 82% (18 of 22) of patients had improvement in somatosensory function, whole mouth taste was perceived as improved by only 35% (7 of 20). It is proposed that the perception of whole mouth taste may not be related to the ability to perceive multiple sensory modalities, but rather to special sensory (taste) modality perception. Also, central changes may occur in the special sensory fibers that impact on the brainstem nucleus for taste (nucleus solitarius) and therefore the patient's perception of taste.

Techniques to prevent olfactory nerve reconstitution in the pigeon

Transectioned olfactory nerves in birds can reestablish structural and functional connections with the olfactory bulbs in comparatively short time spans, thereby hampering long-range studies of avian olfaction and behavior. Accordingly, techniques are described that are suitable for impeding the reconstitution of the olfactory nerve after its transection in the pigeon. These involve the use of inexpensive and easily obtainable materials including cotton pellets, glass beads, and polyethylene tubing.