Broad-spectrum neuroprotection exerted by DDD-028 in a mouse model of chemotherapy-induced neuropathy.

ABSTRACT: Neurotoxicity of chemotherapeutics involves peculiar alterations in the structure and function, including abnormal nerve signal transmission, of both the peripheral and central nervous system. The lack of effective pharmacological approaches to prevent chemotherapy-induced neurotoxicity necessitates the identification of innovative therapies. Recent evidence suggests that repeated treatment with the pentacyclic pyridoindole derivative DDD-028 can exert both pain-relieving and glial modulatory effects in mice with paclitaxel-induced neuropathy. This work is aimed at assessing whether DDD-028 is a disease-modifying agent by protecting the peripheral nervous tissues from chemotherapy-induced damage. Neuropathy was induced in animals by paclitaxel injection (2.0 mg kg -1 i.p). DDD-028 (10 mg kg -1 ) and the reference drug, pregabalin (30 mg kg -1 ), were administered per os daily starting concomitantly with the first injection of paclitaxel and continuing 10 days after the end of paclitaxel treatment. The behavioural tests confirmed the antihyperalgesic efficacy of DDD-028 on paclitaxel-induced neuropathic pain. Furthermore, the electrophysiological analysis revealed the capacity of DDD-028 to restore near-normal sensory nerve conduction in paclitaxel-treated animals. Histopathology evidence indicated that DDD-028 was able to counteract effectively paclitaxel-induced peripheral neurotoxicity by protecting against the loss of intraepidermal nerve fibers, restoring physiological levels of neurofilament in nerve tissue and plasma, and preventing morphological alterations occurring in the sciatic nerves and dorsal root ganglia. Overall, DDD-028 is more effective than pregabalin in preventing chemotherapy-induced neurotoxicity. Thus, based on its potent antihyperalgesic and neuroprotective efficacy, DDD-028 seems to be a viable prophylactic medication to limit the development of neuropathies consequent to chemotherapy.

Cannabinoid Effect and Safety in Spasticity Following Stroke: A Double-Blind Randomized Placebo-Controlled Study.

Background: Nabiximols is a cannabis-based drug to treat spasticity-associated symptoms currently approved for patients with multiple sclerosis only. Cannabinoids are useful in an increasing number of medical conditions but may bear an increased risk for cardiovascular events. SativexStroke is a double-blind randomized placebo-controlled crossover monocentric clinical trial investigating the efficacy and safety of nabiximols in patients with spasticity following stroke. Methods: Patients were treated with nabiximols oromucosal spray or placebo and assessed before and after two phases of 1-month duration each. Cardiovascular safety was assessed before and during the trial. Primary endpoints were changes in spasticity numeric rating scale scores and electromyographic recording of the stretch reflex in affected wrist flexors. Secondary outcome measures were numeric rating scale scores for pain, sleep and bladder function, the number of daily spasms and clinical assessment of spasticity with the modified Ashworth scale. The study was registered with the EudraCT number 2016-001034-10. Results: Between May 2, 2018, and February 20, 2020, 41 patients entered the study. Seven patients did not complete the study, so 34 were included in the analysis. Two serious adverse events occurred, but none related to cardiovascular function. Primary and secondary efficacy outcome measures did not change from baseline during nabiximols treatment relative to placebo. Conclusion: This study suggests that nabiximols use is probably safe in stroke patients, therefore cannabinoid usefulness may be further investigated. The lack of nabiximols effect could be related to low pain levels in recruited patients or different spasticity mechanisms between post-stroke and multiple sclerosis patients. Similarly, a beneficial effect of nabiximols could have emerged if more patients with a higher level of spasticity at baseline were recruited. Clinical Trial Registration: https://www.clinicaltrialsregister.eu/ctr-search/trial/2016-001034-10/IT.

Comparison of Threshold and Tolerance Nociceptive Withdrawal Reflexes in Horses.

The nociceptive withdrawal reflex (NWR) is used to investigate nociception in horses. The NWR threshold is a classical model endpoint. The aims of this study were to determine NWR tolerance and to compare threshold and tolerance reflexes in horses. In 12 horses, the NWR was evoked through electrical stimulation of the digital nerve and recorded via electromyography from the deltoid. Behavioral reactions were scored from 0 to 5 (tolerance). First, the individual NWR threshold was defined, then stimulation intensity was increased to tolerance. The median NWR threshold was 7.0 mA, whereas NWR tolerance was 10.7 mA. Upon visual inspection of the records, two main reflex components R1 (median latency 44 ms) and R2 (median latency 81 ms) were identified at threshold. Increasing stimulation intensity to tolerance led to a significant increase in the amplitude and duration of R1 and R2, whereas their latency decreased. At tolerance, a single burst of early, high-amplitude reflex activity, with a median latency of 39 ms, was detected in 15 out of 23 stimulations (65%). The results of this study suggest that (1) it is feasible to determine NWR tolerance in horses and (2) high-intensity stimuli initiate ultrafast bursts of reflex activity, which is well known in practice and has now been quantified using the NWR model.

Measuring Latency Variations in Evoked Potential Components Using a Simple Autocorrelation Technique.

Interpretation of averaged evoked potentials is difficult when the time relationship between stimulus and response is not constant. Later components are more prone to latency jitter, making them insufficiently reliable for routine clinical use even though they could contribute to greater understanding of the functioning of polysynaptic components of the afferent nervous system. This study is aimed at providing a simple but effective method of identifying and quantifying latency jitter in averaged evoked potentials. Autocorrelation techniques were applied within defined time windows on simulated jittered signals embedded within the noise component of recorded evoked potentials and on real examples of somatosensory evoked potentials. We demonstrated that the technique accurately identifies the distribution and maximum levels of jitter of the simulated components and clearly identifies the jitter properties of real evoked potential recording components. This method is designed to complement the conventional analytical methods used in neurophysiological practice to provide valuable additional information about the distribution of latency jitter within an averaged evoked potential. It will be useful for the assessment of the reliability of averaged components and will aid the interpretation of longer-latency, polysynaptic components such as those found in nociceptive evoked potentials.

Early nociceptive evoked potentials (NEPs) recorded from the scalp.

OBJECTIVE: Neurophysiological investigation of nociceptive pathway has so far been limited to late cortical responses. We sought to detect early components of the cortical evoked potentials possibly reflecting primary sensory activity. METHODS: The 150 IDE micropatterned electrode was used to selectively activate Aδ intraepidermic fibres of the right hand dorsum in 25 healthy subjects and 3 patients suffering from trigeminal neuralgia. Neurographic recordings were performed to assess type of stimulated fibres and check selectivity. Cortical evoked potentials were recorded from C3'-Fz and Cz-Au1. RESULTS: Neurographic recordings confirmed selective activation of Aδ fibres. Early components were detected after repetitive stimulation (0.83/s rate and 250-500 averages); the first negative component occured at 40 ms (N40) on the contralateral scalp. CONCLUSIONS: The provided data support the hypothesis that N40 could be the cortical primary response conducted by fast Aδ fibres. SIGNIFICANCE: This is the first report of early, possibly primary, cortical responses in humans by nociceptive peripheral stimulation. Although not perfected yet to allow widespread diagnostic use, this is probably the only method to allow fully objective evaluation of the nociceptive system, with important future implications in experimental and clinical neurophysiology.

Detection of movement related cortical potentials in freehand drawing on digital tablet.

BACKGROUND: Cortical activity connected to movements has been investigated long since, and is related, among other factors, to saliency of the gesture. However, experiments performed on movements in actual situations are rare, as most of them have been performed in laboratory simulations. Besides, no research seems to have been carried out on subjects during freehand drawing. NEW METHOD: We propose a method based upon a commercial drawing tablet and wireless pen, that has been synchronized with EEG recording by means of a piezoelectric sensor attached to the pen tip. Complete freedom of movement is allowed, and any kind of drawing style can be performed using currently available graphics software. RESULTS: EEG recordings during meaningful drawing were compared with recordings where the pen was tapped and shifted on tablet without specific purpose. With reference to T0 event (pen touching tablet), several components could be observed in pre- and post-T0 epochs. The most important appeared to be a triphasic wave (N-150, P-40 and N + 30), where P-40 showed a striking difference between drawing and tap session, being much larger in the former. COMPARISON WITH EXISTING METHODS: Onset of muscle EMG is usually employed for synchronization. In complex and free gestures too many muscles are active to allow reliable identification of such reference. Our method provides a precise trigger event easily detected without movement constraints. CONCLUSIONS: With this method it will be possible to record EEG activity related to creative aspects of drawing and explore other skilled movements.

Using correlation analysis to assess the reliability of evoked potential components identified by signal averaging.

BACKGROUND: Signal averaging is the conventional method of enhancing the signal-to-noise ratio in recordings of evoked potentials (EPs) from the skin surface in humans. However there may be difficulties in reliably identifying the features of interest especially when a low number of trials are averaged or when large artefacts with similar waveform as the signal are present. NEW METHOD: This method uses the median cross-correlation coefficient of every possible pair of recording repetitions within user-defined windows across the time course of the evoked potential. This is shown to be a good surrogate of signal-to-noise ratio and can be superimposed on the averaged trace to provide reliability information for all components of interest. RESULTS: We applied our method both to simulated signals embedded within the noise component of EP recordings and to real examples of somatosensory EPs. We demonstrated that it can assess the reliability of recorded components independently from their amplitude and could identify artefacts which mimicked genuine components. COMPARISON WITH EXISTING METHODS: There have been a number of previous approaches to this problem but none has found widespread support. This method adds additional information to a common existing technique and is easy to interpret and apply. CONCLUSIONS: This method is used as a visual adjunct to the existing interpretation of averaged evoked potentials and will allow judgements of the reliability of each observed component to be made. This is particularly valuable for situations where few repetitions are possible such as nociceptive evoked potentials, which are of increasing clinical interest.

The new micropatterned interdigitated electrode for selective assessment of the nociceptive system.

BACKGROUND: In this neurophysiological study, we aimed at verifying the nociceptive selectivity of the new, micropatterned electrode (150IDE), recently designed to generate an electric field limited to the intraepidermal free nerve endings. METHODS: Using the new 150IDE, we recorded evoked potentials after stimulation of the face and hand dorsum in 22 healthy participants and in patients with exemplary conditions selectively affecting the nociceptive system. We also measured the peripheral conduction velocity at the upper arm and verified the nociceptive selectivity of 150IDE assessing the effect of a selective block of nociceptive nerve fibres of radial nerve with local anaesthetic infiltration. In healthy participants and in patients, we have also compared the 150IDE-evoked potentials with laser-evoked potentials. RESULTS: In healthy participants, the 150IDE-evoked pinprick sensation and reproducible scalp potentials, with latency similar to laser-evoked potentials. The mean peripheral conduction velocity, estimated at the upper arm, was 12 m/s. The selective nociceptive fibre block of the radial nerve abolished the scalp potentials elicited by the 150IDE stimulation. In patients, the 150IDE-evoked potentials reliably detected the selective damage of the nociceptive system. CONCLUSIONS: Our neurophysiological study shows that this new 150IDE provides selective information on nociceptive system. SIGNIFICANCE: 150IDE is a promising new tool for investigating nociceptive system in patients with neuropathic pain.

Micropatterned surface electrode for massive selective stimulation of intraepidermal nociceptive fibres.

BACKGROUND: No satisfactory neurophysiological test for nociceptive afferents is available to date. Laser stimuli present risks of skin damage, whilst electrical stimulation through specially designed electrodes is not selective enough. NEW METHOD: We present a new electrode designed according to critical issues identified in preliminary computer simulations concerning electric field gradient through the skin. To provide selective stimulation the activating electric field must be limited to intraepidermal free nerve endings. To this end, a new interdigitated electrode (IDE) was made of conductive rails arranged in a comb-like micropattern, situated only 150µm apart from each other (150 IDE) and alternately connected to the opposite poles of the stimulator. RESULTS: Evoked potentials recorded from the scalp were obtained after stimulation with the 150 IDE and with a similarly designed, but more widely spaced electrode (1000µm, or 1000 IDE). Small amplitude early and medium latency components were recorded with the 1000 IDE, suggesting activation of Aß fibres. On the other hand, the 150 IDE only evoked late responses, confirming sufficient selectivity in small fibre activation. COMPARISON WITH EXISTING METHOD(S): The main differences with existing electrodes are: 1) Microspaced interdigitated conductive rails. 2) The potentially unlimited surface of stimulation and high efficiency per surface unit, resulting in large numbers of activated nociceptors. CONCLUSIONS: A new electrode providing selective stimulation of nociceptive nerve free endings is presented. It is non-invasive, and its surface can be enlarged at will. It is expected that it may greatly help in neurophysiological assessment of conditions affecting the nociceptive pathway.

Rehabilitation of balance disturbances due to chemotherapy-induced peripheral neuropathy: a pilot study.

BACKGROUND: Cancer patients with chemotherapy-induced peripheral neuropathy (CIPN) have sensory and motor deficits leading to inappropriate proprioceptive feedback, impaired postural control, and fall risk. Balance training with computerized force platforms has been successfully used in rehabilitation of balance disturbances, but programs specifically developed for CIPN patients are lacking. AIM: This pilot study evaluated a rehabilitation protocol exclusively based on visual computer-feedback balance training (VCFBT) to improve balance in patients with CIPN. DESIGN: Open-label, non-randomized pilot study, 4-week intervention with pre- vs. post-treatment evaluation. SETTING: Outpatients of the Rehabilitation Institute of the Salvatore Maugeri Foundation, in Genoa, Italy. POPULATION: Seven out-patients with clinical-instrumental diagnosis of CIPN. METHODS: At admission, patients were administered the Berg Balance Scale (BBS) and underwent static-dynamic posturography using a computerized force platform to objectively quantify their balance impairment. Their performance was compared to values of a normal age-matched population. Patients then underwent 4 weeks of VCFBT (three 60-minute sessions/week). At discharge, BBS and posturography were repeated and the results compared with those at admission. RESULTS: A significant pre- vs. post-treatment improvement was found in balance as measured by static-dynamic posturography (P=0.004) and BBS (P<0.002). CONCLUSIONS: Despite caution needed for the low sample size, this pilot study has shown preliminary evidence that intensive rehabilitation, based on VCFBT can produce a significant improvement in balance outcomes. CLINICAL REHABILITATION IMPACT: To our knowledge, this is the first report in CIPN patients of a rehabilitation program based exclusively on VCFBT.

Relationship between balance and cognitive performance in older people.

We investigated the relationship between balance and cognitive level in a group of 70 women with no definite Alzheimer's disease or mild cognitive impairment diagnosis and no impairment of daily activity. Static stabilometry and the Montreal Cognitive Assessment (MoCA) test were performed. The antero-posterior sway component was demonstrated to be the best predictor of the MoCA overall score. As visual and proprioceptive components of balance could safely be excluded in our assessments, the vestibular system is to be considered as a putative link between balance and cognitive impairment.

Cutaneous innervation of the human face as assessed by skin biopsy.

The morphology of cutaneous sensory and autonomic innervation in human trigeminal territory is still unknown. The aim of this study is to describe facial cutaneous innervation using skin biopsy. This new tool could be useful in understanding the mechanisms underlying several facial pain conditions. In 30 healthy subjects, we quantified epidermal nerve fibers (ENFs) and dermal myelinated fibers (MFs) in V1, V2 and V3, using indirect immunofluorescence and confocal microscopy applied to 2-mm punch skin biopsies from areas adjacent to the eyebrow, upper and lower lip. Using selective markers, we also evaluated the distribution of peptidergic, cholinergic and noradrenergic fibers. Facial skin appeared abundantly innervated and rich in annexes. The ENF density decreased and the MF density increased, moving from the supraorbital to the perioral skin. Noradrenergic sudomotor fibers were particularly and constantly expressed compared with other body sites. Distribution of vasoactive intestinal peptide-immunoreactive (VIP-ir) fibers appeared peculiar for their constant presence in the subepidermal neural plexus - in close contact, but without colocalization with calcitonin gene related peptide (CGRP) and substance P (Sub-P)-ir fibers. Finally, in perioral skin samples, we observed striated muscle fibers with their motor nerves and motor endplates. Our work provides the first morphological study of human facial cutaneous innervation, highlighting some unique features of this territory. Quantification of unmyelinated and myelinated fibers on 2-mm punch biopsies appeared to be feasible and reliable. Facial skin biopsy may be a new approach with which to study and to better characterize facial pain syndromes.

Electrophysiological features of the mouse tail nerves and their changes in chemotherapy induced peripheral neuropathy (CIPN).

Electrophysiology of tail nerves in rodents has been demonstrated a reliable method to investigate models of peripheral neuropathies. Nevertheless, data concerning mouse models are lacking. We assessed the normal features of sensory and motor conduction of tail nerves in adult mice. We found that, as in rats, a sensory compound action potential and motor responses could be recorded with the non invasive and highly reliable technique proposed, especially if bipolar derivations were used. We also investigated the changes related to chemotherapy induced peripheral neuropathy (CIPN) after paclitaxel treatment (times 1 and 2), compared to pre-treatment (time 0) and to controls. It was found that only the sensory compound action potential was involved in CIPN, with decrease in amplitude and conduction velocity, suggesting a significant reduction in number of fast conducting fibres and a correspondent increase in the number of slow conducting ones, although the total amount of active myelinated fibres was deemed to be unchanged through time 0, time 1 and time 2. The results obtained in CIPN provide new functional evidence about the involvement of sensory fibres and may help in better understanding the underlying mechanisms.

The ITFR, impulsive tail flick reflex by short duration nociceptive stimuli.

A new method for evoking the tail flick reflex is introduced, using short duration or "impulsive" nociceptive stimuli, which allow synchronization and recording of electrophysiological responses. Ten adult rats were studied, by means of thermal (CO(2) laser infrared pulse with 30 ms duration, 7.5 or 10W), electric (a 25 ms train of five 0.2 ms pulses, with 5 or 10 mA intensity) or mechanical (pin pressed with 5 g force) stimuli. Both electromyographic and strain gauge mechanical responses were recorded from the tail. All three types of stimulation gave rise to three components, named early, late and ultralate, respectively occurring in the range of 19-97 ms, 190-519 ms, 1,523-2,765 ms. Conduction velocities of the underlying afferent fibres were calculated by moving the stimulation site. The early component could be linked to Aδ afferents, while late and ultralate components were due to unmyelinated C afferents. Experiments with Fentanyl (20 µg/kg) showed that only the C linked components were depressed, with the ultralate component the most affected, possibly because supraspinally originated. Tail flick reflex evoked by impulsive stimuli is believed to be an important electrophysiological complement to behavioural procedures, useful in identifying the site of action of analgesics and other drugs upon the spinal and supraspinal centres involved in nociception.

Both Schwann cell and axonal defects cause motor peripheral neuropathy in Ebf2-/- mice.

Charcot-Marie-Tooth neuropathies are frequent hereditary disorders of the nervous system and most cases remain without a molecular definition. Mutations in transcription factors have been previously associated to various types of this disease. Mice carrying a null mutation in Ebf2 transcription factor present peripheral nerve abnormalities. To get insight into Ebf2 function in peripheral nervous system, here we characterize the peripheral neuropathy affecting these mice. We first show that Ebf2 is largely expressed in peripheral nerve throughout postnatal development, its expression being not only restricted to non-myelin forming Schwann cells, but also involving myelin forming Schwann cells and the perineurium. As a consequence, the onset of myelination is delayed and Schwann cell differentiation markers are downregulated in Ebf2-/- mice. Later in development, myelin pathology appears less severe and characterized by isolated clusters of hypomyelinated fibers. However, we find defects in the nerve architecture, such as abnormalities of the nodal region and shorter internodal length. Furthermore, we demonstrate a significant decrease in axonal calibre, with a lack of large calibre axons, and a severe impairment of motor nerve conduction velocity and amplitude, whereas the sensory nerve parameters are less affected. Interestingly, a clinical case with peripheral motor neuropathy and clinical features similar to Ebf2-/- mice phenotype was associated with a deletion encompassing EBF2 human genomic locus. These findings demonstrate that Ebf2 is a new molecule implicated in peripheral nerve development and a potential candidate gene for peripheral nerve disorders.

Balance features in Alzheimer's disease and amnestic mild cognitive impairment.

We evaluated alterations of balance by stabilometry in patients with amnestic mild cognitive impairment (aMCI) and with mild-moderate Alzheimer's disease (AD). Fifteen patients with aMCI and 15 with mild AD were recruited according to the current diagnostic criteria. Fifteen healthy subjects of the same age range were recruited as controls. Stabilometry was carried out using a commercial 4 load cell platform. Statistical analysis of between group differences was performed using one-way analysis of variance for parametric data and Kruskal-Wallis tests for non-parametric data. Spearman correlation coefficients were used to investigate the association between cognitive test scores and stabilometric data. All stabilometry measures were significantly altered in mild AD patients compared to normal controls. Antero-posterior sway was found to be the most sensitive parameter, since it correlated with the ADAS-cog orientation subscale in AD patients, and also discriminated between aMCI and normal controls. Our study shows that impairment in balance is a feature not only of AD, but also of aMCI. The alterations found suggest that a progressive failure of the vestibular system, possibly linked to reduced hippocampal performance, may be responsible for such a feature. Further research must be focused on studying the predictive value of stabilometry in the conversion of aMCI.

Compound action potential of sensory tail nerves in the rat.

Assessment of the conduction velocity of motor fibers of the rat tail nerves has been used by some authors in the past, but very little is known about the sensory fibers. In 10 adult rats, weighing between 320 and 380 g, responses from the nerves and muscles of the tail have been recorded after stimulation at its root and tip. It was found that stimulation of the tip involved mainly sensory fibers, of which two main groups could be identified. One faster group, conducting within the range of 38-27 m/s, and one slower group with range 14-7 m/s. The bipolar recording configuration was found to be optimal for sensory recording. Stimulation of the tail root evoked a motor response, which was preceded by a very small neurographic activity, due to the fastest sensory fibers conducting antidromically. The conduction velocity of motor fibers was calculated to be approximately 19 m/s. Distance traveled by the volley can be assessed with excellent precision on the tail nerves; hence the calculated conduction velocities are highly reliable and reproducible. We propose that the tail nerves may be a useful tool for evaluation of conduction velocity of Abeta and Adelta afferents. As the technique is just minimally invasive, the test can be repeated a number of times in animals under chronic experimental conditions.

Persistence of high-dose oxaliplatin-induced neuropathy at long-term follow-up.

Oxaliplatin (L-OHP) has become a standard treatment for advanced colorectal cancer and a valid option for patients in the adjuvant setting. Compared with cisplatin, L-OHP has no renal toxicity, only mild hematological and gastrointestinal toxicity, while neurotoxicity is the limiting toxicity. This side effect has been described as a transient distal dysesthesia, enhanced by exposure to cold, and as a dose-related cumulative mild sensitive neuropathy. We studied two groups of patients (18 and 13) with advanced colorectal cancer, treated with median cumulative doses of L-OHP 862 mg/m2 and 1,033.5 mg/m2. All the patients had been evaluated previously, during treatment, after discontinuation and after a long follow-up of 5 years to verify the incidence and the characteristics of the neuropathy induced by this antineoplastic agent. The clinical and neurophysiological examinations showed an acute and transient neurotoxicity and a cumulative dose-related sensory neuropathy in nearly all the patients. The reversibility of these effects was studied. Five patients continue to manifest symptoms and signs of neurotoxicity after a long follow-up, indicating persistence of this peculiar type of neuropathy.

Evaluation of administration of isoflurane at approximately the minimum alveolar concentration on depression of a nociceptive withdrawal reflex evoked by transcutaneous electrical stimulation in ponies.

OBJECTIVE: To investigate effects of isoflurane at approximately the minimum alveolar concentration (MAC) on the nociceptive withdrawal reflex (NWR) of the forelimb of ponies as a method for quantifying anesthetic potency. ANIMALS: 7 healthy adult Shetland ponies. PROCEDURE: Individual MAC (iMAC) for isoflurane was determined for each pony. Then, effects of isoflurane administered at 0.85, 0.95, and 1.05 iMAC on the NWR were assessed. At each concentration, the NWR threshold was defined electromyographically for the common digital extensor and deltoid muscles by stimulating the digital nerve; additional electrical stimulations (3, 5, 10, 20, 30, and 40 mA) were delivered, and the evoked activity was recorded and analyzed. After the end of anesthesia, the NWR threshold was assessed in standing ponies. RESULTS: Mean +/- SD MAC of isoflurane was 1.0 +/- 0.2%. The NWR thresholds for both muscles increased significantly in a concentration-dependent manner during anesthesia, whereas they decreased in awake ponies. Significantly higher thresholds were found for the deltoid muscle, compared with thresholds for the common digital extensor muscle, in anesthetized ponies. At each iMAC tested, amplitudes of the reflex responses from both muscles increased as stimulus intensities increased from 3 to 40 mA. A concentration-dependent depression of evoked reflexes with reduction in slopes of the stimulus-response functions was detected. CONCLUSIONS AND CLINICAL RELEVANCE: Anesthetic-induced changes in sensory-motor processing in ponies anesthetized with isoflurane at concentrations of approximately 1.0 MAC can be detected by assessment of NWR. This method will permit comparison of effects of inhaled anesthetics or anesthetic combinations on spinal processing in equids.