Nerve Action Potential Recordings Research Articles

On the Stimulation Artifact Reduction during Electrophysiological Recording of Compound Nerve Action Potentials.

Recording neuronal activity triggered by electrical impulses is a powerful tool in neuroscience research and neural engineering. It is often applied in acute electrophysiological experimental settings to record compound nerve action potentials. However, the elicited neural response is often distorted by electrical stimulus artifacts, complicating subsequent analysis. In this work, we present a model to better understand the effect of the selected amplifier configuration and the location of the ground electrode in a practical electrophysiological nerve setup. Simulation results show that the stimulus artifact can be reduced by more than an order of magnitude if the placement of the ground electrode, its impedance, and the amplifier configuration are optimized. We experimentally demonstrate the effects in three different settings, in-vivo and in-vitro.

Некоторые особенности регистрации потенциала действия слухового нерва у пациентов с кохлеарными имплантами

Recording of auditory nerve action potential is now widely used in clinical practice to objectively adjust speech processor parameters in patients with cochlear implants. According to some authors, the correlation coefficient between the potential of the auditory nerve and the most comfortable level varies within a fairly wide range, but nevertheless it well determines the relief of the tuning curve. This article discusses the relationship of this correlation to the rate of growth of the response amplitude of the auditory nerve potential. Patients with high growth rate of auditory nerve potential amplitude show high correlation (R = 0,71) of this threshold with maximum comfortable level of auditory perception, but patients with low speed show low correlation (R = 0,34) of this dependence. In the latter case, the automatic mode of recording the auditory nerve potential does not achieve the desired result and requires the use of the visual analysis mode of the obtained results. In this case, it is necessary to create several progressive maps with subsequent verification of the results on the patient's behavioral reactions. The paper also presents a variety of options for recording the effect potential of the auditory nerve in special groups of patients with an anomaly of the cochlear and auditory nerve.

SY5.4. Monitoring for peripheral nerve surgery

Injuries or diseases of peripheral nerves can have severe impact on function, severe disability (inability to work), social and psychological effects or chronic pain. The main reason to perform Intraoperative monitoring (IOM) during peripheral nerve surgery are to prevent nerve injuries during surgery, to identify peripheral nerves or fascicles in cases of variable anatomy, scar tissue or tumors, to determine axon continuity across a lesion, and to guide surgical decisions regarding the type of neural reconstruction to perform. Nerve action potential (NAP) recording is considered a standard method for peripheral nerve monitoring given its ability to determine the presence or absence of functional axons in a segment of nerve, it also localizes functional and non-functional nerve segments. A NAP recording requires 4.000 to 5.000 intact or regenerating axons to be obtained and its preferred to compound muscle action potential (CMAP) recordings. The presence or absence of a NAP is more important than its latency, amplitude or shape. If a NAP is recorded in a nerve or fascicle, neurolysis is performed, and nerve grafts are required in no-responding fascicles. Some technical difficulties of NAP recording are related to very short stimulation/recording distances, stimulus artifact, volume conduction from another nerve, low temperature, use of tourniquet and use of local anesthetics. CMAP recording is like that used in triggered EMG, surface or subcutaneous needle electrodes are placed over desired muscles and the exposed peripheral nerve is stimulated. Free EMG is useful to detect, in real time, trains or bursts of abnormal discharges that indicate possible nerve damage. It́s easy to use, not affected by anesthesia and has high sensitivity but low specificity. Bipolar intramuscular electrodes are preferred for EMG recordings.

Can MitoTEMPO protect rat sciatic nerve against ischemia-reperfusion injury?

Abdominal ischemia-reperfusion (I/R) is known to cause both structural and functional damage to sciatic nerve which is related to the oxidative stress. We investigated the protective effects of mitochondria-targeted antioxidant (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride (MitoTEMPO) on ischemia-reperfusion-induced nerve damage by using the conduction velocity distribution (CVD) calculations from in vitro compound nerve action potential (CNAP) recordings from rat sciatic nerve. Adult male Wistar albino rats were divided into three groups. The IR and IR + MT groups had aortic cross-clamping for 1h followed by 2h reperfusion, while SHAM group had the same procedure without cross-clamping. IR + MT group received 0.7mg/kg/day MitoTEMPO injection for 28days before I/R, while other groups received vehicle alone. Ischemia-reperfusion resulted in a significant decrease (p < .05) in maximum depolarizations (mV), areas (mV.ms), and maximum and minimum upstroke velocities (mV/ms) of CNAPs, while injection of MitoTEMPO showed a complete protective effect on these impairments. The histograms for CVD showed that I/R blocked the contribution of fast-conducting fibers (> 60m/s). MitoTEMPO prevented that blockage and caused a shift in the CVD. Functional nerve damage caused by I/R can be prevented by MitoTEMPO, which can enter mitochondria, the main source of reactive oxygen species (ROS).

Scalpel edge roughness affects post-transection peripheral nerve regeneration

BackgroundGentle and precise tissue dissection reduces collateral tissue damage and preserves its structural quality for optimizing healing. This is particularly true for peripheral nerve neurorrhaphy. Axon regeneration kinetics across the repair is dependent on the amount of intraneural fibrosis. The purpose of this study was to determine whether scalpel blade smoothness was a deterministic factor in the kinetics of postneurorrhaphy peripheral axon regeneration. MethodsScalpel transection of the saphenous nerve was performed in 18 female Hartley guinea pigs either by a standard #15 stainless steel scalpel blade or a highly polished version of the same blade. Compound nerve action potential recordings and histochemical assay of neurofilament density proximal and 1 cm distal to the site of nerve transection were quantified postneurorrhaphy at postoperative weeks 5, 9, and 12. ResultsThere was no action potential transmission observed in the distal axons immediately after neurorrhaphy. A substantial acceleration of axonal conduction recovery was observed in nerves transected with polished scalpel blades observed by high compound nerve action potential amplitudes at postneurorrhaphy weeks 5 and 9 (P < .05). In addition, an increased recovery of intra-axonal neurofilament density in nerves transected with polished scalpel blades was observed by postoperative week 5 (P < .05). ConclusionThe quality of the scalpel blade is an important determinate of postsurgical healing. Gentle handling of tissue matters.

Artifact reduction by using alternating polarity stimulus pairs in intraoperative peripheral nerve action potential recording.

Intraoperative nerve action potential (NAP) recording permits direct study of an injured nerve for functional assessment of lesions in continuity. Stimulus artifact contamination often hampers NAP recording and interferes with its interpretation. In the present study, we evaluated the artifact reduction method using alternating polarity in peripheral nerve recording. Our study was conducted under controlled conditions in laboratory animals. NAPs were recorded from surgically exposed median or ulnar nerves. For the artifact reduction method with alternating polarity, two sequential recordings, one with normal and one with reversed stimulus polarity, were acquired and the signals from this recording pair were averaged. Simulation was also performed to further evaluate the effects of alternating polarity on the waveforms. The results are as follows: First, we found that this method worked for recordings with unsaturated electrical stimulus artifacts. Second, slightly unequal latencies occurred in an NAP pair, and this inequality contributed to a minimal loss of NAP amplitudes when averaging the two recordings. Third, perfect artifact cancelation and minimal signal loss were also demonstrated by simulation. Finally, we applied the method during nerve inching and demonstrated its usefulness in intraoperative NAP recordings as the method made the recording more resilient to short conduction distances. Thus, our findings demonstrate that this artifact reduction method can be used as a supplemental tool together with our previously described bridge grounding technique or the nonlifting nerve recording configuration to further improve intraoperative peripheral nerve recording. The method can be applied in clinical settings.

Solutions to the technical challenges embedded in the current methods for intraoperative peripheral nerve action potential recordings.

Intraoperative nerve action potential (NAP) recording is a useful tool for surgeons to guide decisions on surgical approaches during nerve repair surgeries. However, current methods remain technically challenging. In particular, stimulus artifacts that contaminate or mask the NAP and therefore impair the interpretation of the recording are a common problem. The authors' goal was to improve intraoperative NAP recording techniques by revisiting the methods in an experimental setting. First, NAPs were recorded from surgically exposed peripheral nerves in monkeys. For the authors to test their assumptions about observed artifacts, they then employed a simple model system. Finally, they applied their insights to clinical cases in the operating room. In monkey peripheral nerve recordings, large stimulus artifacts obscured NAPs every time the nerve segment (length 3-5 cm) was lifted up from the surrounding tissue, and NAPs could not be recorded. Artifacts were suppressed, and NAPs emerged when "bridge grounding" was applied, and this allowed the NAPs to be recorded easily and reliably. Tests in a model system suggested that exaggerated stimulus artifacts and unmasking of NAPs by bridge grounding are related to a loop effect that is created by lifting the nerve. Consequently, clean NAPs were acquired in "nonlifting" recordings from monkey peripheral nerves. In clinical cases, bridge grounding efficiently unmasked intraoperative NAP recordings, validating the authors' principal concept in the clinical setting and allowing effective neurophysiological testing in the operating room. Technical challenges of intraoperative NAP recording are embedded in the current methods that recommend lifting the nerve from the tissue bed, thereby exaggerating stimulus artifacts by a loop effect. Better results can be achieved by performing nonlifting nerve recording or by applying bridge grounding. The authors not only tested their findings in an animal model but also applied them successfully in clinical practice.

Stable InSe transistors with high-field effect mobility for reliable nerve signal sensing

Among two-dimensional layered semiconductors, indium selenide (InSe) is one of the most promising materials with absolute advantages in field-effect transistors (FETs) because of its high electron mobility and stable material properties. Some work has been performed to improve the mobility of InSe FETs. However, in practical applications, electrical stability of FETs is another essential factor to guarantee the performance of the electronic system. Here, we show a highly stable InSe FET with a field-effect mobility of 1200 cm2/V·s in the practical working regime. The bottom-gate staggered InSe FET was fabricated with a polymethyl methacrylate (PMMA)/HfO2 dual-layer gate dielectric and PMMA back-channel encapsulation. The hysteresis was maintained at 0.4 V after 30 days of storage under normal ambient conditions, and the threshold voltage shift was retained at 0.6 V with a gate stress VGS of 10 V, which represents the best electrical stability reported to date. Its high mobility and electrical stability enable reliable detection of the weak nerve action potential at a low power consumption. High-performance InSe FETs expand their promising applications in flexible and in situ real-time intelligent nerve action potential recording.

T97. A revisit of the clinically used methods for intraoperative nerve action potential recordings in nonhuman primate

Compound nerve action potential recordings are often used intraoperatively to assist the surgeon in decision making on surgical approaches during nerve repair surgeries. The methods used clinically are based on surgical recordings (Robert et al., 2009). Although these methods are of great simplicity as handheld electrodes are applied to a nerve dissected and isolated from surrounding tissues, implementation of the methods in the clinical setting remains challenging. Here, we report findings from an experiment where similar recordings were made in nonhuman primate in order to improve our understanding and the performance of the methods. Recordings were made from the median nerve at the upper arm of an adult female pigtail monkey under TIVA (pentobarbital) and full NMB (pancuronium). Core body temperature was maintained near 38 °C. Nerve action potentials were induced by constant current stimulation and recorded using laboratory equipment. IONM electrodes were used: triple and double hook electrodes (Cadwell) for stimulation and recording, respectively. Using the same recording configuration as in the clinical situation, we failed to record recognizable compound action potentials across a short conduction length of a nerve (3–4 cm) that was isolated and suspended from surrounding tissues as large stimulus artifacts obscured the neuronal signal. The stimulus artifacts were suppressed and the compound nerve action potential became unmasked after a saline-soaked gauze was placed underneath the nerve between the stimulating and recording electrodes to bridge the nerve and the surrounding tissues (i.e., ‘bridge grounding’). Furthermore, compound action potentials were of small amplitude when all prongs of the stimulation electrode were placed underneath the nerve. However, the potentials increased markedly in size with another modification, i.e. when the nerve was placed between the middle prong and the outer 2 prongs of the stimulation electrode (i.e., ‘sandwich stimulation’) after reshaping of the prongs. The recordings were made at room temperature (about 23 °C) without use of warm saline irrigation, at which the compound action potentials preserved good amplitudes but slowed in conduction, leading to a better separation of compound action potentials from stimulus artifacts. We reversely translated the clinical methods of nerve compound action potential recording to a laboratory setting in order to better understand the factors affecting performance. We observed that compound nerve action potentials could be reliably recorded with IONM electrodes when 2 modifications, the ‘bridge grounding’ and ‘sandwich stimulation’, were made. Confirmation and additional experiments are underway to revisit the clinically used recording techniques in the laboratory setting.

Jack bean urease modulates neurotransmitter release at insect neuromuscular junctions

BackgroundPlants have developed a vast range of mechanisms to compete with phytophagous insects, including entomotoxic proteins such as ureases. The legume Canavalia ensiformis produces several urease isoforms, of which the more abundant is called Jack Bean Urease (JBU). Previews work has demonstrated the potential insecticidal effects of JBU, by mechanisms so far not entirely elucidated. In this work, we investigated the mechanisms involved in the JBU-induced activity upon neurotransmitter release on insect neuromuscular junctions. MethodsElectrophysiological recordings of nerve and muscle action potentials, and calcium imaging bioassays were employed. Results and conclusionJBU (0.28 mg/animal/day) in Locusta migratoria 2nd instar through feeding and injection did not induce lethality, although it did result in a reduction of 20% in the weight gain at the end of 168 h (n = 9, p ≤ 0.05). JBU (0.014 and 0.14 mg) injected direct into the locust hind leg induced a dose and time-dependent decrease in the amplitude of muscle action potentials, with a maximum decrease of 70% in the amplitude at the highest dose (n = 5, p ≤ 0.05). At the same doses JBU did not alter the amplitude of action potentials evoked from motor neurons. Using Drosophila 3rd instar larvae neuromuscular preparations, JBU (10−7 M) increased the occurrence of miniature Excitatory Junctional Potentials (mEJPs) in the presence of 1 mM CaCl2 (n = 5, p ≤ 0.05). In low calcium (0.4 mM) assays, JBU (10−7 M) was not able to modulate the occurrence of the events. In Ca2+-free conditions, with EGTA or CoCl2, JBU induced a significant decrease in the occurrence of mEPJs (n = 5, p ≤ 0.05). Injected into the 3rd abdominal ganglion of Nauphoeta cinerea cockroaches, JBU (1 μM) induced a significant increase in Ca2+ influx (n = 7, p ≤ 0.01), similar to that seen for high KCl (35 mM) condition. Taken together the results confirm a direct action of JBU upon insect neuromuscular junctions and possibly central synapses, probably by disrupting the calcium machinery in the pre-synaptic region of the neurons.

Electrophysiological study of the palmar cutaneous nerves in diabetics

Background: Polyneuropathy in diabetics which may be asymptomatic, targets particularly sensory neurons and their axons, starting in their distal terminals. Aims and Objectives: Aim of the present study was to identify the presence of subclinical neuropathy in Type 2 diabetic patients with the help of sensory nerve conduction studies (NCS). Material and Methods: Diabetic and control groups underwent standard antidromic technique of sensory NCS and recording of sensory nerve action potentials (SNAPs) of the palmar digital branches of the median and ulnar nerves using Neuro perfect software on windows based computerized electromyographic/nerve conduction velocity/evoked response Mark II system and surface electrodes. Results: On comparing the parameters of NCS it was found that distal latency of both the nerves was higher in diabetics than controls with a statistically significant difference. Results also showed a statistically significant decrease in conduction velocities of both nerves in diabetics. The mean SNAP amplitudes for all tested nerves were found to be decreased significantly in diabetics. Conclusions: Sensory nerves are found affected in diabetics with no clinical sign and symptoms of neuropathy. NCS is a sensitive test which can be used to identify subclinical cases.

Axonal excitability and conduction alterations caused by levobupivacaine in rat.

In this study, effects of the long-acting amide-type local anesthetic levobupivacaine on axonal conduction and excitability parameters of the rat sciatic nerve were thoroughly examined both in vitro and in vivo. In order to deduce its effects on isolated nerve conduction, compound nerve action potential (CNAP) recordings were performed using the suction method over sciatic nerves of Wistar rats before and after administration of 0.05 % (1.7 mmol L-1) levobupivacaine. Levobupivacaine caused complete CNAP area and amplitude depression by blocking conduction in a time-dependent manner. To assess the influence of levobupivacaine on in vivo excitability properties, threshold-tracking (TT) protocols were performed at sciatic nerves of rats injected with perineural 0.05 % (1.7 mmol L-1) levobupivacaine or vehicle alone. Charge-duration TT results revealed that levobupivacaine increases the rheobase and decreases the strength-duration time constant, suggesting interference of the anesthetic with the opening of Na+ channels. Twenty and 40 % threshold electrotonus curves were found for both groups to follow the same paths, suggesting no significant effect of levobupivacaine on K+ channels for either the fastest or relatively slow conducting fibers. Current-threshold relationship results revealed no significant effect on axonal rectifying channels. However, according to the results of the recovery cycle protocol yielding the pattern of excitability changes following the impulse, potential deviation was found in the recovery characteristics of Na+ channels from the absolute refractory period. Consequently, conduction blockage caused by levobupivacaine may not be due to the passive (capacitive) properties of axon or the conductance of potassium channels but to the decrease in sodium channel conductance.

Measurement of electrochemical conductance of penile skin using Sudoscan®: A new tool to assess neurogenic impotence

To investigate the value of electrochemical skin conductance (ESC) measurement at penile level using Sudoscan® for the diagnosis of neurogenic impotence in diabetics. The following neurophysiological parameters were assessed in 25 male diabetics who complained of impotence and 25 age-matched normal male subjects without erectile dysfunction (age range: 29-70 years): ESC, sympathetic skin responses (SSR), warm detection thresholds (WDT), and cold detection thresholds (CDT) for the penis and the feet, vibration detection thresholds (VDT) for the penis, and sensory nerve conduction study of the dorsal nerve of the penis (DNP) with sensory nerve action potential (SNAP) recording. Diabetic patients with impotence differed from controls with regard to most neurophysiological results at both penile and foot levels. Among penile innervation variables in the group of impotent diabetics, penile ESC was found to be the most frequently abnormal (80% of patients), followed by penile WDT, CDT, and DNP-SNAP amplitude (52% of patients), and then penile SSR amplitude and VDT (44% of patients). Various combinations of abnormalities were observed: penile ESC was the only abnormal test in 2 patients, while all tests were abnormal in 2 patients and remained normal in only one patient. Erectile dysfunction is common in diabetic men, but the diagnosis of a neurogenic origin is challenging. This study showed that ESC measurement using Sudoscan® is feasible and more sensitive than SSR recordings to show penile sympathetic innervation impairment. This new test should be further studied to better define its diagnostic accuracy and clinical correlates.

The need for and the challenges of measuring renal sympathetic nerve activity

Renal denervation (RDN) was primarily developed to treat hypertension and is potentially a new method for treating arrhythmias. Because of the lack of a standardized protocol to measure renal sympathetic nerve activity, RDN is administered in a blind manner. This inability to assess efficacy at the time of treatment delivery may be a large contributor to the ambiguity of RDN outcomes reported in the hypertension literature. The advancement of RDN as a treatment of hypertension or arrhythmias will be hampered by the lack of delivery assessment, a deficiency that the cardiovascular electrophysiology community, with its expertise in recording and mapping, may have a role in addressing and overcoming. The development of endovascular recording of renal nerve action potentials may provide a useful accessory tool for RDN. Innovation in this area will be crucial as we as a community reconsider the therapeutic value of RDN.

Surgical management and outcome of iatrogenic radial nerve injection injuries

ObjectiveIatrogenic injury to the radial nerve can occur following intramuscular or intravenous injections of the upper extremity. In this study, we review the injury mechanism, operative techniques, and outcomes of patients evaluated for radial nerve injection injuries. MethodsData from 33 patients evaluated by the senior authors (DGK and DHK) from 1970–2011 with radial nerve injection injuries were reviewed retrospectively. All patients had injury of the nerve during injection. All corrective operations involved the use of direct intraoperative nerve action potential (NAP) recordings and either neurolysis, neurectomy, or suture/graft repair. The Louisiana State University Health Science (LSUHS) grading system was used for clinical assessment. ResultsOf the 33 patients, 23 underwent surgical intervention for persistent neurological deficit and/or pain. Of the 24 patients evaluated for injuries at the arm level, 17 required surgical exploration and repair for persistent symptoms. Nine patients required external neurolysis because the lesions were in continuity and positive NAP recording was across the lesion. All of these patients achieved a Grade 4 or better in functional recovery. Eight patients with lesions in continuity but in which NAP could not be recorded underwent either end-to-end suture (7) or graft repair (1) following resection of a 3.0cm non-recordable segment. All patients achieved Grade 3 or 4 functional recovery. Six patients with forearm injuries involving the superficial sensory branch of radial nerve underwent either neurolysis (3) or neurectomy (3). ConclusionsSurgical exploration may be indicated when pain or disabling motor deficits persist. Early diagnosis and operative intervention can achieve favorable outcomes through exploration and radial nerve repair.

Surgical outcomes of 156 spinal accessory nerve injuries caused by lymph node biopsy procedures.

Iatrogenic injuries to the spinal accessory nerve (SAN) are not uncommon during lymph node biopsy of the posterior cervical triangle (PCT). In this study, the authors review the operative techniques and surgical outcomes of 156 surgical repairs of the SAN following iatrogenic injury during lymph node biopsy procedures. This retrospective study examines the authors' clinical and surgical experience with 156 patients with SAN injury between 1980 and 2012. All patients suffered iatrogenic SAN injuries during lymph node biopsy, with the vast majority (154/156, 98.7%) occurring in Zone I of the PCT. Surgery was performed on the basis of anatomical and electro-physiological findings at the time of the operation. The mean follow-up period was 24 months (range 8-44 months). Of the 123 patients who underwent graft or suture repair, 107 patients (87%) improved to Grade 3 functionality or higher using the Louisiana State University Health Science Center (LSUHSC) grading system. Neurolysis was performed in 29 patients (19%) when the nerve was found in continuity with recordable nerve action potential (NAP) across the lesion. More than 95% of patients treated by neurolysis with positive NAP recordings recovered to LSUHSC Grade 3 or higher. Forty-one patients (26%) underwent end-to-end repair, while 82 patients (53%) underwent graft repair, and Grade 3 or higher recovery was assessed for 90% and 85% of these patients, respectively. The average graft length used was 3.81 cm. Neurotization was performed in 4 patients, 2 of whom recovered to Grade 2 and 3, respectively. SAN injuries present challenges for surgical exploration and repair because of the nerve's size and location in the PCT. However, through proper and timely intervention, patients with diminished or absent function achieved favorable functional outcomes. Surgeons performing lymph node biopsy procedures in Zone I of the PCT should be aware of the potential risk of injury to the SAN.

The optimal distance between two electrode tips during recording of compound nerve action potentials in the rat median nerve.

The distance between the two electrode tips can greatly influence the parameters used for recording compound nerve action potentials. To investigate the optimal parameters for these recordings in the rat median nerve, we dissociated the nerve using different methods and compound nerve action potentials were orthodromically or antidromically recorded with different electrode spacings. Compound nerve action potentials could be consistently recorded using a method in which the middle part of the median nerve was intact, with both ends dissociated from the surrounding fascia and a ground wire inserted into the muscle close to the intact part. When the distance between two stimulating electrode tips was increased, the threshold and supramaximal stimulating intensity of compound nerve action potentials were gradually decreased, but the amplitude was not changed significantly. When the distance between two recording electrode tips was increased, the amplitude was gradually increased, but the threshold and supramaximal stimulating intensity exhibited no significant change. Different distances between recording and stimulating sites did not produce significant effects on the aforementioned parameters. A distance of 5 mm between recording and stimulating electrodes and a distance of 10 mm between recording and stimulating sites were found to be optimal for compound nerve action potential recording in the rat median nerve. In addition, the orthodromic compound action potential, with a biphasic waveform that was more stable and displayed less interference (however also required a higher threshold and higher supramaximal stimulus), was found to be superior to the antidromic compound action potential.

Neurophysiological examination of dorsal sural nerve

Nerve conduction study of the dorsal sural nerve (DSN) has been reported to be a sensitive method for early detection of peripheral neuropathies. However, normal reference values are scarce and vary greatly among the different studies. A comprehensive neurophysiological study, including nerve conduction velocity (NCV) and sensory nerve action potential (SNAP) recording, was performed in 294 healthy subjects (21-86 years) with no evidence of neuropathy. The amplitude of the DSN SNAP ranged from 2.50 to 15.90 μV, and NCV ranged from 28.9 to 52.8 m/s. A significant age-related decrease in DSN SNAP amplitude and NCV was observed. The mean ratio of sural NCV to DSN NCV was 1.33 ± 0.19, and the mean ratio of sural nerve SNAP amplitude to DSN SNAP amplitude was 3.17 ± 1.33. These normative data of the DSN might be used as reference values for the study of this very distal peripheral nerve.

Direkte Ableitung vom Nervus cochlearis bei transtemporaler Resektion von Vestibularisschwannomen

Intraoperative monitoring (IOM) of the cochlear nerve function during acoustic neuroma surgery is employed to assist in preserving hearing. So far, Auditory Brain-stem Response (ABR) is considered to be an optimal method for intraoperative monitoring in transtemporal approach. The aim of this study was to perform direct recording of the cochlear nerve action potential after resection of the tumor by using a ball-electrode and to evaluate the use of this method in predicting the postoperative hearing. The obtained data were compared to the simultaneous ABR results and to the postoperative hearing. In 2009, 38 patients have undergone acoustic Neuroma Surgery at the ENT University hospital, Wuerzburg. In 33 patients an intraoperative ABR as well as a direct measurement from the cochlear nerve using a ball electrode were performed. In 5 patients the postoperative hearing was predicted using the direct measurement at the cochlear nerve only. The direct recording from the cochlear nerve gave very robust responses. Even in cases where ABR recording was not possible, the identification of clear cochlear nerve action potential could still be reached. Using the direct recordings from the cochlear nerve to predict the post operative hearing turned out to have a sensitivity of 100% and a specificity of 70%. These results show that intraoperative monitoring with direct recording from the cochlear nerve via a ball-electrode in transtemporal approaches offers a valuable method to predict the postoperative hearing. Further investigation will be made to provide additional information.

Axillary nerve injury associated with sports

The aim of this retrospective study was to present and investigate axillary nerve injuries associated with sports. This study retrospectively reviewed 26 axillary nerve injuries associated with sports between the years 1985 and 2010. Preoperative status of the axillary nerve was evaluated by using the Louisiana State University Health Science Center (LSUHSC) grading system published by the senior authors. Intraoperative nerve action potential recordings were performed to check nerve conduction and assess the possibility of resection. Neurolysis, suture, and nerve grafts were used for the surgical repair of the injured nerves. In 9 patients with partial loss of function and 3 with complete loss, neurolysis based on nerve action potential recordings was the primary treatment. Two patients with complete loss of function were treated with resection and suturing and 12 with resection and nerve grafting. The minimum follow-up period was 16 months (mean 20 months). The injuries were associated with the following sports: skiing (12 cases), football (5), rugby (2), baseball (2), ice hockey (2), soccer (1), weightlifting (1), and wrestling (1). Functional recovery was excellent. Neurolysis was performed in 9 cases, resulting in an average functional recovery of LSUHSC Grade 4.2. Recovery with graft repairs averaged LSUHSC Grade 3 or better in 11 of 12 cases Surgical repair can restore useful deltoid function in patients with sports-associated axillary nerve injuries, even in cases of severe stretch-contusion injury.