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

Simple Summary

Nociception is the physiological basis of the complex experience of pain. An established model for its quantification in equine studies is based on the nociceptive withdrawal reflex evoked by electrical stimulation of a sensory nerve. The reflex is recorded via electromyography and it is common to determine the threshold at which a nociceptive-specific reflex activity can be observed. In the present study, the classical methodology was expanded for a deeper understanding of the physiology of nociceptive reflexes in horses. First, for each individual horse, a threshold was determined as the minimal stimulation intensity able to evoke a nociceptive withdrawal reflex. Second, the stimulation intensity was stepwise increased up to tolerance, which was defined as the stimulus that is able to elicit the maximal tolerable behavioral reaction. The characteristics of the reflex activity on the electromyographic records were compared for threshold and tolerance stimulation intensities. At tolerance, the reflex became faster and wider than at threshold, indicating that either a spinal summation mechanism or the recruitment of faster sensory fibers occurs in response to high-intensity noxious stimuli. A novel endpoint (i.e., tolerance) can now be considered when applying the nociceptive withdrawal reflex model in equine studies.

Abstract

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.

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.

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.

The chemotherapy-induced peripheral neuropathy outcome measures standardization study: from consensus to the first validity and reliability findings

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating and dose-limiting complication of cancer treatment. Thus far, the impact of CIPN has not been studied in a systematic clinimetric manner. The objective of the study was to select outcome measures for CIPN evaluation and to establish their validity and reproducibility in a cross-sectional multicenter study.

PATIENTS AND METHODS

After literature review and a consensus meeting among experts, face/content validity were obtained for the following selected scales: the National Cancer Institute-Common Toxicity Criteria (NCI-CTC), the Total Neuropathy Score clinical version (TNSc), the modified Inflammatory Neuropathy Cause and Treatment (INCAT) group sensory sumscore (mISS), the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30, and CIPN20 quality-of-life measures. A total of 281 patients with stable CIPN were examined. Validity (correlation) and reliability studies were carried out.

RESULTS

Good inter-/intra-observer scores were obtained for the TNSc, mISS, and NCI-CTC sensory/motor subscales. Test-retest values were also good for the EORTC QLQ-C30 and CIPN20. Acceptable validity scores were obtained through the correlation among the measures.

CONCLUSION

Good validity and reliability scores were demonstrated for the set of selected impairment and quality-of-life outcome measures in CIPN. Future studies are planned to investigate the responsiveness aspects of these measures.

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.

Therapy of trigeminal neuralgia secondary to multiple sclerosis

Trigeminal neuralgia occurs in approximately 1-2% of patients suffering from multiple sclerosis. Its pathophysiology is common to idiopathic forms and resides in altered properties of the sensory axonal membrane at the root entry zone into the pons, leading to parossistic firing. Antiepileptic drugs of the sodium channel blocker type, such as carbamazepine, lamotrigine, and phenytoin are highly effective in controlling pain. However, side effects on the CNS may, at higher doses, severely worsen the already impaired neurologic conditions in multiple sclerosis patients. Baclofen, a presynaptic muscle relaxant is also beneficial in trigeminal pain. Whatever the drug, habituation and loss of efficacy are likely to occur sooner or later. Symptomatic, neurolesive surgery is indicated in cases resistant or intolerant to medical therapy. Radiofrequency thermorhizotomy, either monitored by trigeminal evoked potentials or not, is the recommended procedure, as it may be considered the most reliable as far as localization and degree of lesion are concerned.

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.

Trigeminal sensory pathway function in patients with SUNCT

OBJECTIVE

Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) is a rare primary headache whose origins are unclear. To seek information on its pathophysiology, we studied the trigeminal Abeta and Adelta pathways by recording trigeminal reflexes and laser evoked potentials (LEPs) in patients with SUNCT.

METHODS

Trigeminal reflexes and LEPs were recorded in 11 consecutive patients. Ten patients had neuroimaging evidence documenting idiopathic SUNCT and one had a posterior fossa tumour that compressed the trigeminal nerve thus causing symptomatic SUNCT.

RESULTS

Whereas the patients with idiopathic SUNCT had normal trigeminal reflex and LEP responses, the patient with symptomatic SUNCT had abnormal responses.

CONCLUSIONS

Our neurophysiological findings show that idiopathic SUNCT spares the trigeminal sensory pathways whereas symptomatic SUNCT does not.

SIGNIFICANCE

Neurophysiological testing can easily differentiate the idiopathic and symptomatic forms of SUNCT. It also suggests that the two forms are pathophysiologically distinct entities.

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.

Measurement of skin temperature after infrared laser stimulation

OBJECTIVES

Several types of lasers are available for eliciting laser evoked responses (LEPs). In order to understand advantages and drawbacks of each one, and to use it properly, it is important that the pattern of skin heating is known and duly considered. This study was aimed at assessing the skin temperature during and immediately after irradiation with pulses by Nd:YAP and CO(2) lasers.

MATERIALS AND METHODS

The back of the non-dominant hand was irradiated in 8 subjects. Temperatures were measured by a fast analogical pyrometer (5 ms response time). Stimuli were tested on natural colour (white) and blackened skin.

RESULTS

Nd:YAP pulses yielded temperatures that were correlated with pulse energy, but not with pulse duration; much higher temperatures were obtained irradiating blackened skin than white skin (ranges 100-194 degrees C vs 35-46 degrees C). Temperature decay was extremely slow in white skin, reaching its basal value in more than 30 s. CO(2) pulses delivered with power of 3W and 6W yielded temperatures of 69-87 degrees C on white skin, and 138-226 degrees C on blackened skin. Temperature decay was very fast (4-8 ms).

CONCLUSIONS

Differences in peak temperatures and decay times between lasers and tested conditions depend on energy and volume of heated skin. The highest temperatures are reached with lesser degree of penetration, as in the case of CO(2) laser and blackened skin. Taking into account the temperature decay time of the skin, the minimum interstimulus interval to get reliable LEPs should be no less than 10 s for Nd:YAP and 100 ms for CO(2) laser. Another important practical consequence of the heating pattern is that the Nd:YAP pulses will activate warmth receptors more easily than CO(2).

Aδ nociceptor response to laser stimuli: selective effect of stimulus duration on skin temperature, brain potentials and pain perception

OBJECTIVE

To disclose a possible effect of duration of pulsed laser heat stimuli on Adelta nociceptor responses, skin temperature profiles, brain evoked potentials and pain perception.

METHODS

We used a laser stimulator which works in the millisecond range and allows us to change the duration of the pulse while keeping the total energy of the stimulus constant. In 10 healthy volunteers, we measured the intensity of perceived pain with a 0-10 scale and the latency and amplitude of the early N1 and late N2 components of the scalp potentials evoked by laser pulses of equal energy and three different stimulus durations (2, 10, and 20 ms). Using a specifically developed pyrometer with a temporal resolution lower than 1 ms we also measured stimulus-induced changes of skin temperature.

RESULTS

Stimulus duration significantly influenced temperature rise times, pain perception, and brain potentials. Shorter stimulus durations yielded steeper slopes in the skin temperature profiles and higher pain ratings, shortened the latency of the N1 and N2 components, and increased the amplitude of N1.

CONCLUSIONS AND SIGNIFICANCE

The shorter stimulus duration shortens receptor activation times and yields a more synchronous afferent volley, thus providing a stronger spatial-temporal summation at central synapses that enhances intensity of first pain and brain potentials. This may prove useful in clinical applications.

Early abnormalities in sciatic nerve function and structure in a rat model of Charcot-Marie-Tooth type 1A disease

We investigated early peripheral nervous system impairment in PMP22-transgenic rats ("CMT rat"), an established animal model for Charcot-Marie-Tooth disease 1A, at postnatal day 30 (P30), when the clinical phenotype is not yet apparent. Hemizygous CMT1A rats and wildtype littermates were studied by means of behavioral examination, electrophysiology, molecular biology, and light microscopy analysis. Behavioral studies only showed, a mild, but significant, decrease in toe spread 1-5, suggesting a weakness of distal foot muscles in CMT1A rats compared with normal littermates. Nerve conduction studies disclosed a severe slowing in motor conduction velocity, a temporal dispersion and a dramatic decrease of amplitude of motor waves in P30 transgenic animals. Coherently with a demyelinating process, affected nerves showed a significant thinning of myelin. Interestingly, axonal diameter and area were unchanged, but expression of non-phosphorylated neurofilaments was increased in CMT1A rats compared with normal controls. Our results confirm the fidelity of this animal model to human disease. Similarly, in young CMT1A patients, the MCV is significantly reduced and the muscle weakness is confined to distal segments, whereas morphological and morphometrical signs of axonal atrophy are absent. However, the presence of a molecular and functional damage of the axons suggests that this may be the correct moment to start neuroprotective therapies.

Prévalence des sténoses des artères rénales dépistées au cours de coronarographies diagnostiques : dans quels cas doit-on réaliser une aortographie abdominale ?

PURPOSE

To define a subgroup of patients at increased risk of renal artery stenosis (RAS) in a population of patients undergoing cardiac catheterization.

MATERIALS AND METHODS

A total of 467 patients (mean age of 64 Years +/-11) underwent cardiac catheterization and aortography Results were evaluated to detect correlations between the presence or absence of RAS and clinical and biological parameters.

RESULTS

A total of 42 (9%) patients had a renal artery stenosis. Univariate analysis defined parameters correlated with the presence of RAS: systolic blood pressure (p=0.03), pulse pressure (p=0.005), age (p<0.0001), creatinine clearance (p<0.0001), 2-vessel (p=0.028) and 3-vessel (p=0.037) coronary artery diseases. Multivariate analysis showed that the presence of RAS correlated to creatinine clearance (p=0.02) and 2-vessel coronary artery disease. A creatinine clearance between 30 and 60 ml/min and multi-vessel coronary artery disease defined a subgroup at increased risk of RAS with sensitivity, specificity, positive and negative predictive values of: 47.6, 90.1, 32.3 and 94.6%. The prevalence of renal artery stenosis was 5.2% when both parameters were absent.

CONCLUSION

Patients with mild renal insufficiency and multi-vessel coronary artery disease defined a subgroup of patients at increased risk of RAS (32.5%) that may benefit from abdominal aortography performed at the time of cardiac catheterization.

Excitability of the Adelta nociceptive pathways as assessed by the recovery cycle of laser evoked potentials in humans

To investigate the excitability of Adelta nociceptive pathways and the nature of the vertex laser evoked potentials (LEPs), we studied the recovery cycle of the P2-LEP component and compared it with that of the P200 of the somatosensory evoked potential (SEP). Using two identical CO(2)-laser stimulators, we delivered paired stimuli to two adjacent skin spots on the hand at interstimulus intervals ranging from 250 ms to 2 s. The test P2-LEP was strongly inhibited at the 250-ms interstimulus interval ( P<0.01) and progressively recovered by the 2-s interval. The P200-SEP, after paired stimuli to the median nerve, showed a time course even slower than the P2-LEP ( P<0.01). Besides providing the LEP recovery curve in normal subjects, our findings indicate that the P2-LEP relays through a number of synapses similar to (or even lower than) that for the P200-SEP, thus lending further support to the view that the nociceptive P2-LEP is not an endogenous potential equivalent to the P300.

Unmyelinated trigeminal pathways as assessed by laser stimuli in humans

Laser pulses excite superficial free nerve endings innervated by small-myelinated (Adelta) and unmyelinated (C) fibres. Whereas laser-evoked scalp potentials (LEPs) are now reliably used to assess function of the Adelta-fibre nociceptive pathways in patients with peripheral or central lesions, the selective activation of C-fibre receptors and recording of the related brain potentials remain difficult. To investigate trigeminal C-fibre function, we directed laser pulses to the facial skin and studied sensory perception and scalp evoked potentials related to Adelta- or C-fibre activation in healthy humans and patients--one having a bilateral facial palsy, two a trigeminal neuropathy, and two a Wallenberg syndrome. We also measured afferent conduction velocity and, with source analysis, studied the brain generators. Whereas laser pulses of low intensity and small irradiated area elicited pinprick sensations and standard Adelta-LEPs, laser pulses of very-low intensity and large irradiated area elicited warmth sensations and scalp potentials with a latency compatible with C-fibre conduction (negative wave 280 ms, positive wave 380 ms); the estimated conduction velocity was 1.2 m/s. The main waves of the scalp potentials originated from the anterior cingulate gyrus; they were preceded by activity in the opercular region and followed by activity in the insular region. The patient with bilateral facial palsy, who had absent trigeminal-facial reflexes, had normal Adelta- and C-related scalp potentials; the patients with trigeminal neuropathy, characterized by loss of myelinated and sparing of unmyelinated fibres, had absent Adelta- but normal C-related potentials; and the patients with Wallenberg syndrome had absent Adelta- and C-related potentials. We conclude that laser pulses with appropriate characteristics evoke brain potentials related to the selective activation of trigeminal nociceptive Adelta or thermal C fibres. The trigeminal territory yields rewarding LEP findings owing to the high density of thermal receptors and, because the short conduction distance, minimizes the problem of signal dispersion along slow-conducting unmyelinated afferents. The opercular-insular region and the cingulate gyrus are involved in the processing of C-fibre trigeminal inputs. The method we describe may prove useful in patients with lesions affecting the trigeminal thermal pain pathways.

Prevalence of carotid stenosis in type 2 diabetic patients asymptomatic for cerebrovascular disease

Stroke, with an incidence of 2.5 x 10(3) yr(-1) (95% CI, 2.3-2.8 x 10(3) yr(-1)), is the third most frequent cause of death and the first cause of disability in western society. Diabetes is an important risk factor for ischaemic stroke, second only to hypertension, whereas it does not seem to be associated with an increased risk of haemorrhagic stroke. The incidence of stroke in men and women between 45 and 74 yr has been found to be 2.5 and 3.5 times higher in diabetics than in non-diabetic subjects, with a relative risk higher in females than in males with diabetes and greater in both sexes in the 50-to-60-yr age group but decreased in subjects who were 70 and above. It is known that there is an association between ischaemic stroke and carotid stenosis. However, the prevalence of carotid stenosis in Type 2 diabetes mellitus (T2DM) patients has not been well investigated, mainly in the Italian diabetic population. Therefore, the aim of this study was to evaluate the prevalence of carotid artery stenosis in a population of T2DM patients asymptomatic for cerebrovascular disease selected from the files of the Diabetes Clinics, and from the computerised files of General Practitioners (GPs). Three hundred and sixty-five subjects were examined: 187 were non-diabetic (89 males, 98 females) and 178 were T2DM patients (82 males, 96 females). The mean age of all the subjects was 67 +/- 7.8 yr; 66 +/- 7.9 for the non-diabetic subjects and 67 +/- 7.5 yr in the diabetic subjects. In the echo-Doppler examination of the carotid, a degree of stenosis ranging 10-99% was recorded in 143/365 subjects (39.1%), 49/187 non-diabetics (26.2%) and 94/178 diabetics (52.8%). The differences were highly significant (p < 0.001). Severe stenosis was recorded in 17/143 subjects (12%); 12 of these were diabetic (70%) and 5 non-diabetic (30%). The diabetics were three times more likely to develop carotid stenosis than the non-diabetics with an odds ratio of 3.152, (95% CI, 2.032-4.889).

Quantitative assessment of nociception in horses by use of the nociceptive withdrawal reflex evoked by transcutaneous electrical stimulation

OBJECTIVES

To evoke and measure the nociceptive withdrawal reflex (NWR) by use of electromyographic recordings and to score the behavioral nociceptive responses to electrical pulses in standing nonsedated horses.

ANIMALS

10 adult horses.

PROCEDURE

The lateral palmar digital nerve of the forelimb was transcutaneously stimulated, and surface electromyographic responses were recorded from the ulnaris lateralis, extensor carpi radialis, and common digital extensor muscles. Stimuli consisted of a 25-millisecond train of 5 constant-current pulses delivered by a computer-controlled stimulator. The 80- to 250-milliseconds poststimulation interval was analyzed to detect the NWR. The current intensity was increased in steps of 0.5 mA until the NWR threshold intensity (lt) was reached. The stimulus at It was repeated twice. Latency and amplitude of the NWR, together with the behavioral reaction of horses, were analyzed. The latter was scored according to a scale from 0 (no reaction) to 5 (vigorous reaction). Finally, 3 suprathreshold stimuli at 1.2 X It were analyzed.

RESULTS

The median It to elicit NWR was 2.5 mA. Median onset latency of the NWR was 96.0 milliseconds at It and 89.6 milliseconds for suprathreshold stimuli. The amplitude of the reflexes was higher for suprathreshold stimulations, and behavioral reactions were slightly stronger when stimulus intensity increased.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of our study indicate that it is possible to record NWR in conscious standing horses, to define a reflex threshold, and to measure reflexes in response to increasing stimulus intensity.

Autoantibodies to inner ear and endothelial antigens in Cogan's syndrome

BACKGROUND

Cogan's syndrome is a chronic inflammatory disease of unknown origin, characterised by sensorineural hearing loss, episcleritis, and vasculitis. An autoimmune origin has been suggested but not proven. Our aim was to establish whether or not an autoimmune process is the cause of the disease.

METHODS

We used pooled IgG immunoglobulins derived from eight patients with Cogan's syndrome to screen a random peptide library to identify disease relevant autoantigen peptides. Among the identified peptides, one was recognised by all the patients' sera. Antibodies against peptides were affinity purified from patients' sera and used to characterise the autoantigen, to stain human cochlea, and to transfer the features of Cogan's disease into animals.

FINDINGS

We identified an immunodominant peptide that shows similarity with autoantigens such as SSA/Ro and with the reovirus III major core protein lambda 1. The peptide sequence shows similarity also with the cell-density enhanced protein tyrosine phosphatase-1 (DEP-1/CD148), which is expressed on the sensory epithelia of the inner ear and on endothelial cells. IgG antibodies against the peptide, purified from the patients' sera, recognised autoantigens and DEP-1/CD148 protein, bound human cochlea, and inhibited proliferation of cells expressing DEP-1/CD148. The same antibodies bound connexin 26, gene mutations of which lead to congenital inner-ear deafness. Furthermore, these antibodies were able to induce the features of Cogan's disease in mice.

INTERPRETATION

Our results indicate that Cogan's syndrome is an autoimmune disease, characterised by the presence of autoantibodies able to induce tissue damage on binding of cell-surface molecules present on the sensory epithelia of the inner ear and on endothelial cells.

Endothelin-1 plasma levels in cluster headache

BACKGROUND AND OBJECTIVE

A role for endothelin-1, a potent vasoconstrictor peptide, in some cerebrovascular diseases has been proposed. To obtain preliminary data about peripheral concentrations of endothelin-1 in acute cluster headache, we measured the plasma endothelin-1 secretory pattern in 10 men with cluster during and independent of a headache attack.

METHODS

We collected blood samples for plasma endothelin-1 determinations at 0, 15, 30, 45, 60, 90, and 120 minutes during a cluster attack and closely monitored blood pressures. We repeated the same sampling during an asymptomatic period.

RESULTS

The mean values of plasma endothelin-1 (before a cluster headache, 3.3 +/- 0.3 pg/mL) significantly increased (F = 2.578, P < .05) during an attack, reaching their peak at 30 minutes (5.0 +/- 0.5 pg/mL, P < .05). We found no significant variations in mean arterial pressure.

CONCLUSION

Endothelin-1 may play a role in the pathophysiology of cluster attacks. The increase in plasma observed during cluster attacks may be linked to alterations in systemic hemodynamics and vascular tone.

Head extensor reflex evoked by trigeminal stimulation in humans

OBJECTIVE

Excitatory and inhibitory responses have been recognized in human cervical muscles following trigeminal stimulation. However, no evidence has so far been published of a crossed, short-latency, excitatory response resembling the early head extensor reflex seen in the cat. We seek its existence in humans.

METHODS

The study was carried out in 14 voluntary healthy subjects. Percutaneous and surface electrical stimulation of the supraorbital and infraorbital nerves was performed with single, double and repetitive stimuli. Signals were recorded from the relaxed splenius and sternomastoid muscles bilaterally.

RESULTS

Percutaneous stimulation of infraorbital nerve with single stimuli evoked an early response in the contralateral splenius muscle, with onset latency ranging from 11 to 14 ms (HR1). This response was greatly facilitated by double or repetitive stimuli. Single stimuli also gave rise to two larger responses in all 4 muscles in the latency ranges 50-70 ms (HR2) and 100-160 ms (HR3). Surface stimulation of one nerve alone could not elicit any early activity. Single surface stimuli delivered simultaneously to the supraorbital and infraorbital nerves evoked HR1 in only 5 subjects.

CONCLUSIONS

We detected a crossed early reflex of the head extensor muscles to trigeminal stimuli. Its timing is similar to the 8-ms response seen in cats. The evidence provided suggests that the reflex is mediated by an oligosynaptic circuit and that it needs a strong spatial summation at central synapses.

Drug-resistant cluster headache responding to gabapentin: a pilot study

Prompted by the results of gabaergic drugs, such as valproate and topiramate, we performed this pilot study to assess the effect of gabapentin in cluster headache. Eight patients suffering from episodic cluster headache and four suffering from chronic cluster headache were studied. All of them had failed to respond to traditional prophylactic drugs. The design of the study was an open trial. The main parameter for effectiveness was the number of daily attacks. Gabapentin was given at the daily dosage of 900 mg. All patients were pain free after a maximum of 8 days after starting therapy, with a bout duration thus reduced to 16-40% of the average previous bouts (only applies to episodic cluster patients). We hypothesize that the gabaergic action of gabapentin, perhaps combined with other mechanisms, such as calcium channel blockade, may be responsible for its remarkable effects on cluster headache.

Small-fiber dysfunction in trigeminal neuralgia: carbamazepine effect on laser-evoked potentials

BACKGROUND

In patients with trigeminal neuralgia, results of clinical examination of sensory function are normal. Reflex and evoked potential studies have already provided information on large-afferent (non-nociceptive) function. Using laser-evoked potentials (LEP), the authors sought information on small-afferent (nociceptive) function.

METHODS

The brain potentials evoked by CO(2)-laser pulses directed to the perioral and supraorbital regions were studied in 67 patients with idiopathic or symptomatic trigeminal neuralgia and 30 normal subjects. Of the 67 patients, 49 were receiving carbamazepine.

RESULTS

All patients with symptomatic and 51% of those with idiopathic trigeminal neuralgia had frankly abnormal LEP on the painful side. The mean latency was significantly higher and mean amplitude lower on the painful than the nonpainful side. However, even on the nonpainful side, the mean latency was significantly longer than that of the age-matched controls. The nonpainful-side latency correlated significantly with the carbamazepine dose.

CONCLUSIONS

LEP detect severe impairment of the nociceptive afferent system on the painful side of patients with idiopathic as well as symptomatic trigeminal neuralgia. A dysfunction of small-myelinated afferents may play an important role in the pathophysiology of neuralgic pain. Carbamazepine markedly dampens these brain potentials. The authors propose that this effect may result from inhibition of nociceptive transmission in the cingulate gyrus.

Low-dose gabapentin combined with either lamotrigine or carbamazepine can be useful therapies for trigeminal neuralgia in multiple sclerosis

Paroxysmal symptoms occur frequently in multiple sclerosis (MS). Usually they are treated with carbamazepine (CBZ) and phenytoin, although these medications are often interrupted due to adverse effects. We report 11 MS patients with trigeminal neuralgia (TN): 6 intolerant to a therapeutic dosage of CBZ, showing serious adverse effects and subsequently treated with a combination of low-dose CBZ and gabapentin (GBP) (group 1); 5 treated with lamotrigine (LMT), showing adverse effects and subsequently treated with GBP (group 2). Subjective pain level and impairment in performing daily activities were rated utilizing a 3-point scale at time 0 and at optimal dosage time (T1). GBP was initiated at 300 mg daily and titrated, until pain control was achieved without new adverse effects, to a maximum dose of 1,200 mg daily. CBZ or LMT were reduced to a level which no longer produced adverse effects, although resulting in a lack of efficacy in relieving pain. Pain control was obtained in all patients but 1, with no side effects. The plasma level analysis, performed in 5 patients, resulted in normal values. The mean dosages at T1 were: group 1 CBZ 400 mg and GBP 850 mg daily; group 2 LMT 150 mg and GBP 780 mg daily. Combining drugs with complementary modes of action may provide a rational pharmacological approach to the management of TN in MS.

Trigeminal evoked potentials in cluster headache

We sought out alterations of early trigeminal evoked potenials (TEPs) in patients suffering from episodic cluster headache, in order to evaluate a possible direct involvement of the trigeminal nerve. The study was carried out at the Centre for Pain Relief, National Institute for Cancer Research, Genoa in collaboration with the Interuniversity Centre for Pain Neurophysiology, unit of the University of Genoa. We studied 32 patients suffering from episodic cluster headache. TEPs were recorded from the scalp, after stimulation of the infraorbital nerve on both sides. The recordings were performed during the patients' bouts, but outside attacks in 24 cases. In 8 patients the recordings were performed during attacks. All 8 patients tested during an attack showed a delayed or absent W2 and W3 of the TEP, while only 3 of the 24 patients tested outside the attack had delayed W2 and W3. The alterations detected point towards a temporary impairment of conduction along the nerve fibres, approximately at the gasserian ganglion. Such a situation is consistent with a moderate compression by a swollen internal carotid artery or cavernous sinus upon the ganglion, during the attack.

Cluster headache-like pain in multiple sclerosis

We describe a case with simultaneous occurrence of cluster headache-like pain and multiple sclerosis. Both neuroimaging and neurophysiology (trigeminal evoked potentials) revealed a demyelination plaque in the pons, at the trigeminal root entry zone, on the side of pain. Although that type of lesion is usually associated with trigeminal neuralgia pain, we hypothesize that in this case it may be linked with the concomitant cluster headache, possibly by activation of trigemino-vascular mechanisms.

Recovery of nerve conduction following microvascular decompression for trigeminal neuralgia

OBJECTIVE

To assess the function of trigeminal nerve before and after microvascular decompression for trigeminal neuralgia.

BACKGROUND

To date there is no direct evidence that microvascular decompression of the trigeminal root restores normal conduction in the nerve.

METHODS

The authors examined 10 patients with trigeminal neuralgia in whom preoperative MRI and MR angiography demonstrated neurovascular contact. During microvascular decompression, the trigeminal nerve was monitored by recording early scalp trigeminal evoked potentials immediately before, during, and after decompression. Direct recordings from the root entry zone were also performed.

RESULTS

In all patients preoperative scalp evoked potentials showed impaired conduction of the trigeminal root. Microvascular decompression was associated with immediate recovery of conduction in seven patients, demonstrated by both scalp evoked potentials and direct root recordings. All 10 patients were pain free postoperatively.

CONCLUSIONS

Improvement in trigeminal neuralgia following microvascular decompression is often associated with normalization of neurophysiologic data, suggesting recovery of nerve function. Rapid electrophysiologic recovery and pain relief following microvascular decompression argue that neither phenomenon is linked to remyelination. It is possible that the trigeminal evoked potentials might predict an effective microvascular decompression.

Migraine with aura and right-to-left shunt on transcranial Doppler: a case-control study

Right-to-left shunt (RLS), usually due to patent foramen ovale, is a well-established risk factor for ischemic stroke in young patients, while the role of migraine as an independent factor is still debated. We evaluated 44 patients suffering from migraine with aura, and compared them with 73 patients younger than 50 with focal cerebral ischemia, and 50 controls, asymptomatic for cerebrovascular disease, and without a history of migraine. All the subjects underwent bilateral transcranial Doppler with injection of contrast medium in an antecubital vein. The test was performed during normal ventilation and during Valsalva maneuver, recording both the middle cerebral arteries and the basilar artery. Criteria for diagnosing RLS was the presence of at least 3 microbubbles within 15 s from injection. Eighteen out of 44 migraine patients (41%) showed RLS, as opposed to 8 of 50 controls (16%) (p < 0.005). Twenty-six out of 73 patients with cerebral ischemia had RLS (35%). We conclude that the prevalence of RLS in patients with migraine with aura is significantly higher than in normal controls, and is similar to the prevalence of RLS in young patients with stroke. These findings could be helpful in understanding the relationship between migraine and stroke.