Femoral and obturator neuropathies.

The femoral and obturator nerves both arise from the L2, L3, and L4 spinal nerve roots and descend into the pelvis before emerging in the lower limbs. The femoral nerve's primary function is knee extension and hip flexion, along with some sensory innervation to the leg. The obturator nerve's primary function is thigh adduction and sensory innervation to a small area of the medial thigh. Each may be injured by a variety of potential causes, many of them iatrogenic. Here, we review the anatomy of the femoral and obturator nerves and the clinical features and potential etiologies of femoral and obturator neuropathies. Their necessary investigations, including electrodiagnostic studies and imaging, their prognosis, and potential treatments, are discussed in this chapter.

The role of electrodiagnosis in focal neuropathies.

Electrodiagnostic (EDX) testing plays an important role in confirming a mononeuropathy, localizing the site of nerve injury, defining the pathophysiology, and assessing the severity and prognosis. The combination of nerve conduction studies (NCS) and needle electromyography findings provides the necessary information to fully assess a nerve. The pattern of NCS abnormalities reflects the underlying pathophysiology, with focal slowing or conduction block in neuropraxic injuries and reduced amplitudes in axonotmetic injuries. Needle electromyography findings, including spontaneous activity and voluntary motor unit potential changes, complement the NCS findings and further characterize chronicity and degree of axon loss and reinnervation. EDX is used as an objective marker to follow the progression of a mononeuropathy over time.

Physical function as a predictor of chemotherapy-induced peripheral neuropathy in patients with pancreatic cancer.

BACKGROUND: A growing body of research indicates that poor functional status before chemotherapy may be correlated with the severity of chemotherapy-induced peripheral neuropathy (CIPN) after the neurotoxic treatment. However, little is known about the associations between pre-chemotherapy physical function and CIPN in patients with pancreatic cancer. PURPOSE: To identify the predictors of CIPN in relation to pre-chemotherapy physical function in patients with pancreatic cancer. METHODS: This secondary analysis included data from patients with pancreatic cancer who participated in a longitudinal research study at National Cheng Kung University Hospital, Tainan, Taiwan. Four physical function tests (i.e., grip strength, Timed Up and Go (TUG), 2-minute step test (2MST), and Romberg test) and two questionnaires (The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 [EORTC QLQ-C30] and Chemotherapy-Induced Peripheral Neuropathy Module [CIPN20]) were assessed at baseline (i.e., before first chemotherapy session) and 2-, 3-, 4-, and 6-month follow-up. Multiple linear regression with adjustment for confounding factors was used to assess the associations between the four functional tests at baseline and the CIPN20 total score and individual subscale scores (sensory, motor, and autonomic) at 6-month follow-up. RESULTS: Data from a total of 209 pancreatic cancer patients (mean age: 64.4 years, 54.5% male) were analyzed. The findings showed that the severity of CIPN at 6-month follow-up was significantly associated with the baseline TUG completion time (ß = 0.684, p = 0.003). The TUG completion time was also positively correlated with the 6-month CIPN sensory and autonomic subscales. In addition, a baseline positive Romberg test (ß = 0.525, p = 0.009) was a significant predictor of the severity of motor neuropathy at 6-month follow-up. CONCLUSION: The TUG completion time and positive Romberg test before chemotherapy may be predictive factors of the CIPN severity 6 months after the commencement of chemotherapy. Accordingly, the incorporation of TUG and Romberg tests into the clinical assessment protocol emerges as imperative for individuals diagnosed with pancreatic carcinoma undergoing chemotherapy regimens.

Effects of taxane-induced peripheral neuropathy on hand dexterity impairment: evaluation of quantitative and subjective assessments.

PURPOSE: Chemotherapy-induced peripheral neuropathy (CIPN) commonly involves hand dexterity impairment. However, the factors affecting hand dexterity impairment are unknown and there is currently no established treatment. The purpose of the current study was to clarify factors influencing hand dexterity impairment in taxane-induced peripheral neuropathy using subjective and objective assessments. METHODS: We assessed patient characteristics, treatment-related factors, subjective symptoms of CIPN (Patient Neurotoxicity Questionnaire [PNQ]), psychological symptoms, and upper limb dysfunction (Quick Disabilities of the Arm, Shoulder and Hand [Quick DASH]). Quantitative assessments were pinch strength, sensory threshold, hand dexterity impairment, and grip force control. Multiple regression analysis was performed using hand dexterity impairment as the dependent variable and age and PNQ, Quick DASH, and control of grip force as independent variables. RESULTS: Forty-three breast cancer patients were included in the analysis. Hand dexterity impairment in taxane-induced peripheral neuropathy patients was significantly correlated with age, grip force control, and PNQ sensory scores (p < 0.008). Multiple regression analysis demonstrated that PNQ sensory scores and grip force control were significantly associated with hand dexterity impairment (p < 0.01). CONCLUSION: Subjective symptoms (numbness and pain) and grip force control contributed to impaired hand dexterity in taxane-induced peripheral neuropathy.

Alcohol-related peripheral neuropathy: Clinico-neurophysiological characteristics and diagnostic utility of the neuropathy symptoms score and the neuropathy impairment score.

Alcohol overconsumption is well known to cause damage to the peripheral nervous system, affecting both small and large nerve fibers. The aim of this descriptive study was to investigate peripheral nerve damage, and to correlate clinical, epidemiological and neurophysiological findings, in patients diagnosed with Alcohol Use Disorder (AUD). Ninety alcohol-dependent subjects on inpatient basis were enrolled in this prospective study over a 3-year period. Every subject was assessed by the Neuropathy Symptoms Score (NSS) questionnaire and the Neuropathy Impairment Score (NIS) clinical examination grading scale, followed by Nerve Conduction Studies, Quantitative Sensory Testing and Sympathetic Skin Response (SSR) testing. Peripheral neuropathy was diagnosed in 54 subjects (60%), by abnormal neurophysiological tests and presence of clinical signs or symptoms. Among them, pure large fiber neuropathy (LFN) was found in 18 subjects, pure small fiber neuropathy (SFN) in 12 subjects, and both large and small fiber neuropathy was diagnosed in 24 subjects. Using linear regression, we found that higher NSS and NIS scores correlated with lower amplitudes of the sural sensory nerve action potential and of the SSR. We also found a significant longer duration of alcohol abuse in subjects with neuropathy, using Student's t-test (p = 0.024). Additionally, applying NIS abnormal cut-off score ≥4, using ROC analysis, we predicted the majority of subjects with LFN, confirming 95.23% sensitivity and 93.75% specificity. Our study confirmed that peripheral neuropathy involving large and small nerve fibers, with a symmetrical length-dependent pattern, is common between patients with AUD and related to the duration of the disorder. We suggest that NSS and NIS scales could be used for the assessment of neuropathy in clinical practice, when the essential neurophysiological testing is not available.

Posterior Interosseous Neuropathy with Peripheral Dystonia: A Case Report.

Background: Posterior interosseous neuropathy is an uncommon cause of peripheral dystonia. Case Report: A 62-year-old man awakened and noticed right finger drop. A neurological examination revealed posterior interosseous neuropathy with dystonia-like finger movements. Abnormal movements were predominantly observed in the right thumb, ring finger, and little finger. Within 2 weeks, the muscle weakness in the right fingers had completely improved. However, a brief abnormal posture of the right thumb was persistent. Discussion: The residual abnormal posture of the right thumb may reflect pre-existing motor control abnormalities, which may have contributed to the onset of posterior interosseous neuropathy-associated peripheral dystonia.

Electrodiagnostic studies and new diagnostic modalities for evaluation of peripheral nerve disorders.

Electrodiagnostic studies (EDx) are frequently performed in the diagnostic evaluation of peripheral nerve disorders. There is increasing interest in the use of newer, alternative diagnostic modalities, in particular imaging, either to complement or replace established EDx protocols. However, the evidence to support this approach has not been expansively reviewed. In this paper, diagnostic performance data from studies of EDx and other diagnostic modalities in common peripheral nerve disorders have been analyzed and described, with a focus on radiculopathy, plexopathy, compressive neuropathies, and the important neuropathy subtypes of Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), vasculitic neuropathy and diabetic neuropathy. Overall EDx retains its place as a primary diagnostic modality in the evaluated peripheral nerve disorders. Magnetic resonance imaging and ultrasound have developed important complementary diagnostic roles in compressive and traumatic neuropathies and atypical CIDP, but their value is more limited in other neuropathy subtypes. Identification of hourglass constriction in nerves of patients with neuralgic amyotrophy may have therapeutic implications. Investigation of radiculopathy is confounded by poor correlation between clinical features and imaging findings and the lack of a diagnostic gold standard. There is a need to enhance the literature on the utility of these newer diagnostic modalities.

Label-Free Visualization and Morphological Profiling of Neuronal Differentiation and Axonal Degeneration through Quantitative Phase Imaging.

Understanding the intricate processes of neuronal growth, degeneration, and neurotoxicity is paramount for unraveling nervous system function and holds significant promise in improving patient outcomes, especially in the context of chemotherapy-induced peripheral neuropathy (CIPN). These processes are influenced by a broad range of entwined events facilitated by chemical, electrical, and mechanical signals. The progress of each process is inherently linked to phenotypic changes in cells. Currently, the primary means of demonstrating morphological changes rely on measurements of neurite outgrowth and axon length. However, conventional techniques for monitoring these processes often require extensive preparation to enable manual or semi-automated measurements. Here, a label-free and non-invasive approach is employed for monitoring neuronal differentiation and degeneration using quantitative phase imaging (QPI). Operating on unlabeled specimens and offering little to no phototoxicity and photobleaching, QPI delivers quantitative maps of optical path length delays that provide an objective measure of cellular morphology and dynamics. This approach enables the visualization and quantification of axon length and other physical properties of dorsal root ganglion (DRG) neuronal cells, allowing greater understanding of neuronal responses to stimuli simulating CIPN conditions. This research paves new avenues for the development of more effective strategies in the clinical management of neurotoxicity.

Neuropathy in ARSACS is demyelinating but without typical nerve enlargement in nerve ultrasound.

BACKGROUND: To specify peripheral nerve affection in autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) by correlating high-resolution nerve ultrasound and nerve conduction studies. METHODS: We assessed a cohort of 11 ARSACS patients with standardized nerve conduction studies and high-resolution ultrasound of peripheral nerves and compared nerve ultrasound findings to a healthy control group matched for age, sex, size and weight. RESULTS: Mean age of patients was 39.0 (± 14.1) years and disease duration at assessment 30.6 (± 12.5) years. All patients presented with a spasticity, ataxia and peripheral neuropathy. Neuropathy appeared to be primarily demyelinating in 9/11 cases and was not classifiable in 2/11 cases due to not evocable potentials. Nerve ultrasound revealed a normal ultrasound pattern sum score (UPSS) in each ARSACS patient and no significant nerve enlargement compared to the control group. CONCLUSIONS: Peripheral neuropathy in ARSACS showed primarily demyelinating rather than axonal characteristics and presented without nerve enlargement. As demyelinating neuropathies do commonly present enlarged nerves we recommend further genetic testing of the SACS gene in patients who present with this combination of demyelinating neuropathy without nerve enlargement. ARSACS cases that initially presented only with neuropathy without spasticity or ataxia and therefore were misdiagnosed as Charcot-Marie-Tooth disease are supporting this suggestion.

Subclinical motor involvement in nonsystemic vasculitic neuropathy determined by the motor unit number estimation method MScanFit.

INTRODUCTION/AIMS: Nonsystemic vasculitic neuropathy (NSVN) is characterized by a predominant lower limb involvement in many patients. Motor unit changes in upper extremity muscles have not been investigated in this subgroup but may be of interest for improving our understanding of the multifocal nature of the disease and counseling of patients about potential future symptoms. In this study we aimed to better understand subclinical motor involvement in the upper extremity muscles of patients with lower limb-predominant NSVN using the new motor unit number estimation (MUNE) method MScanFit. METHODS: In this single-center, cross-sectional study, 14 patients with biopsy-proven NSVN, with no clinical signs of upper extremity motor involvement, were investigated and compared with 14 age-matched healthy controls. All participants were assessed clinically and by the MUNE method MScanFit to the abductor pollicis brevis muscle. RESULTS: The number of motor units and peak CMAP amplitudes were significantly reduced in patients with NSVN (P = .003 and P = .004, respectively). Absolute median motor unit amplitudes and CMAP discontinuities were not significantly different (P = .246 and P = .1, respectively). CMAP discontinuities were not significantly correlated with motor unit loss (P = .15, rho = 0.4). The number of motor units did not correlate with clinical scores (P = .77, rho = 0.082). DISCUSSION: Both MUNE and CMAP amplitudes showed motor involvement in upper extremity muscles in lower limb-predominant NSVN. Overall, there was no evidence of significant reinnervation. Investigations of the abductor pollicis brevis muscle did not show a correlation with overall functional disability of the patients.

A New Surface Technique for Phrenic Nerve Conduction Study.

Objective: To report a new patient friendly and convenient technique for phrenic nerve conduction with alternative sites of stimulation and recording. Methods: Phrenic nerve conduction was performed in forty volunteers and ten patients of peripheral neuropathy. Active recording electrode was placed in tenth intercostal space 2.5 cm away from para-spinal muscles (mid-scapular line), reference electrode in eighth intercostal space just medial to subcostal margin with ground between stimulating and recording electrode. Stimulation was done at the level of crico-thyroid space near or under the posterior margin of sternocleidomastoid muscle. This new method was compared with existing ones. Analysis: Data was analysed using SPSS 23 version. Correlation between height, weight, body mass index, age, and chest expansion was done using bi-variate correlation. Mean latency and amplitude of the study method were compared with other methods using MANNOVA test. Results: Total of forty subjects were studied. Thirty-seven were male subjects. Mean age was 28.03 ± 9.63 years, height 168.0 ± 9.60 cm and chest expansion 3.53 ± 0.64 cm. Right sided phrenic nerve mean latency was 5.99 ± 0.629 ms and amplitude 1.088 ± 0.178 mV. Left sided phrenic nerve conductions showed mean latency of 6.02 ± 1.82 ms, amplitude of 1.092 ± 0.2912 mV. These standard deviations were smaller than what were observed with other methods suggesting increased consistency of our results. There was no correlation between phrenic nerve conduction with age, height, gender or chest expansion. Conclusion: This study method gave a better as well as consistent morphology, higher amplitude and required lower amount of current strength. It was superior to previously reported methods in consistency of normative data.

Peripheral Neuropathy Evaluations of Patients With Prolonged Long COVID.

BACKGROUND AND OBJECTIVES: Recovery from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection appears exponential, leaving a tail of patients reporting various long COVID symptoms including unexplained fatigue/exertional intolerance and dysautonomic and sensory concerns. Indirect evidence links long COVID to incident polyneuropathy affecting the small-fiber (sensory/autonomic) axons. METHODS: We analyzed cross-sectional and longitudinal data from patients with World Health Organization (WHO)-defined long COVID without prior neuropathy history or risks who were referred for peripheral neuropathy evaluations. We captured standardized symptoms, examinations, objective neurodiagnostic test results, and outcomes, tracking participants for 1.4 years on average. RESULTS: Among 17 patients (mean age 43.3 years, 69% female, 94% Caucasian, and 19% Latino), 59% had ≥1 test interpretation confirming neuropathy. These included 63% (10/16) of skin biopsies, 17% (2/12) of electrodiagnostic tests and 50% (4/8) of autonomic function tests. One patient was diagnosed with critical illness axonal neuropathy and another with multifocal demyelinating neuropathy 3 weeks after mild COVID, and ≥10 received small-fiber neuropathy diagnoses. Longitudinal improvement averaged 52%, although none reported complete resolution. For treatment, 65% (11/17) received immunotherapies (corticosteroids and/or IV immunoglobulins). DISCUSSION: Among evaluated patients with long COVID, prolonged, often disabling, small-fiber neuropathy after mild SARS-CoV-2 was most common, beginning within 1 month of COVID-19 onset. Various evidence suggested infection-triggered immune dysregulation as a common mechanism.

Blood Vessels: The Pathway Used by Schwann Cells to Colonize Nerve Conduits.

The repair of severe nerve injuries requires an autograft or conduit to bridge the gap and avoid axon dispersion. Several conduits are used routinely, but their effectiveness is comparable to that of an autograft only for short gaps. Understanding nerve regeneration within short conduits could help improve their efficacy for longer gaps. Since Schwann cells are known to migrate on endothelial cells to colonize the "nerve bridge", the new tissue spontaneously forming to connect the injured nerve stumps, here we aimed to investigate whether this migratory mechanism drives Schwann cells to also proceed within the nerve conduits used to repair large nerve gaps. Injured median nerves of adult female rats were repaired with 10 mm chitosan conduits and the regenerated nerves within conduits were analyzed at different time points using confocal imaging of sequential thick sections. Our data showed that the endothelial cells formed a dense capillary network used by Schwann cells to migrate from the two nerve stumps into the conduit. We concluded that angiogenesis played a key role in the nerve conduits, not only by supporting cell survival but also by providing a pathway for the migration of newly formed Schwann cells.

Subgrouping of Peripheral Neuropathic Pain Patients According to Sensory Symptom Profile Using the Korean Version of the PainDETECT Questionnaire.

BACKGROUND: A culturally validated Korean version of the PainDETECT Questionnaire (PD-Q) was used to identify neuropathic pain components (NeP) in patients suffering from chronic pain. The purpose of this study was to determine if the Korean PD-Q can be used to subgroup patients with peripheral NeP according to sensory symptom profiles. METHODS: This study included 400 Korean patients with peripheral neuropathic pain diagnosed as probable or definite NeP. The total scores and subscores for each item in PD-Q were transformed into a Z-score for standardization. Hierarchical cluster analysis was performed to identify clusters of subjects by PD-Q scores. RESULTS: The mean total PD-Q score of the study participants was 14.57 ± 6.46. A hierarchical cluster analysis identified 5 clusters with distinct pain characteristic profiles. Cluster 1 had relatively severe burning and tingling sensations. The mean total PD-Q score for cluster 2 was the lowest of the 5 clusters. Cluster 3 tended to be vulnerable to pain in response to cold/heat stimulation. Cluster 4 showed relatively severe pain induced by physical stimuli, such as light touch or slight pressure. Cluster 5 had high scores for all NeP symptoms. CONCLUSION: This study demonstrates the ability of patients to cluster by symptoms using the Korean PD-Q. Subgrouping of peripheral neuropathic pain by sensory symptom profile may be useful in making effective drug treatment decisions.

A 65-Year-Old Man With Weight Loss, Peripheral Neuropathy, and Lower Extremity Swelling.

CASE PRESENTATION: A 65-year-old man with no past medical history sought treatment at the hospital with lower extremity swelling, pain, tingling in a stocking-glove distribution, and syncope. He reported a 23-pound unintentional weight loss. He felt unsteady walking with a couple of falls, and his exercise tolerance was limited to several hundred feet. He did not report vision changes, dysphagia, bowel or bladder problems, tremor, orthopnea, lightheadedness, or chest pain. He did not report any history of substance misuse, high-risk sexual behavior, or concerning exposures. The patient was admitted for further workup.

Mechanistic insights into the pathogenesis of microtubule-targeting agent-induced peripheral neuropathy from pharmacogenetic and functional studies.

Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting toxicity that affects 30%-40% of patients undergoing cancer treatment. Although multiple mechanisms of chemotherapy-induced neurotoxicity have been described in preclinical models, these have not been translated into widely effective strategies for the prevention or treatment of CIPN. Predictive biomarkers to inform therapeutic approaches are also lacking. Recent studies have examined genetic risk factors associated with CIPN susceptibility. This review provides an overview of the clinical and pathologic features of CIPN and summarizes efforts to identify target pathways through genetic and functional studies. Structurally and mechanistically diverse chemotherapeutics are associated with CIPN; however, the current review is focused on microtubule-targeting agents since these are the focus of most pharmacogenetic association and functional studies of CIPN. Genome-wide pharmacogenetic association studies are useful tools to identify not only causative genes and genetic variants but also genetic networks implicated in drug response or toxicity and have been increasingly applied to investigations of CIPN. Induced pluripotent stem cell-derived models of human sensory neurons are especially useful to understand the mechanistic significance of genomic findings. Combined genetic and functional genomic efforts to understand CIPN hold great promise for developing therapeutic approaches for its prevention and treatment.

Patient reported outcomes for cisplatin and radiation followed by carboplatin/paclitaxel versus carboplatin/paclitaxel for locally advanced endometrial carcinoma: An NRG oncology study.

INTRODUCTION: Chemotherapy plus radiation (Cis-RT + CP) did not demonstrate superiority in prolonging relapse-free survival compared to chemotherapy alone in patients with stage III or IVA endometrial carcinoma. The impact of treatment on quality of life (QOL), neurotoxicity (NTX) and psychometric properties of the gastrointestinal (GI) symptoms subscale during treatment and up to 1 year are described herein. METHODS: QOL assessments were scheduled at baseline, 6 weeks (post completion of RT (Cis-RT + CP) or prior to cycle 3 (CP)), then 18 weeks (end of treatment) and 70 weeks (1 year after the end of treatment) after starting treatment. QOL instruments included the FACT-En TOI, FACT/GOG-neurotoxicity (Ntx) subscale (short), and the gastrointestinal (GI) symptoms subscale. RESULTS: At the end of treatment, patients receiving Cis-RT + CP reported a statistically significant decreased QOL when compared to CP. The decline in QOL was reflected in physical well-being, functional well-being, and endometrial cancer specific concerns, but the minimally important differences (MID) were not considered clinically meaningful. Patients in both groups reported increased chemotherapy-induced Ntx symptoms with the CP group having worse scores and reaching peak symptoms at the time of chemotherapy completion. Patients on Cis-RT + CP reported statistically significantly worse GI symptoms after radiation therapy compared to patients on CP, this occurred across assessment intervals, though the MID was not meaningful. Psychometric evaluations indicated that the GI symptom scale is reliable, valid, and responsive to change. CONCLUSIONS: PROs indicate that the chemoradiotherapy group experienced worse HRQoL and GI toxicity compared to patients randomized to chemotherapy alone for locally advanced endometrial cancer though based on the MID, these were not clinically meaningful differences. The GI symptom subscale was a reliable and valid scale that has value for future trials. TRIAL REGISTRATION: NCT00942357.

Evaluating patient-reported symptoms and late adverse effects following completion of first-line chemotherapy for ovarian cancer using the MOST (Measure of Ovarian Symptoms and Treatment concerns).

OBJECTIVES: Knowledge on the course of symptoms patients with ovarian cancer experience is limited. We documented the prevalence and trajectories of symptoms after first-line chemotherapy using the Measure of Ovarian Symptoms and Treatment concerns (MOST). METHODS: A total of 726 patients who received platinum-based chemotherapy for ovarian cancer were asked to complete the MOST every 3 months, beginning 6 months post-diagnosis and continuing for up to 4 years. We used descriptive statistics to examine temporal changes in MOST-S26 index scores for disease or treatment-related (MOST-DorT), neurotoxicity (MOST-NTx), abdominal (MOST-Abdo), and psychological (MOST-Psych) symptoms, and wellbeing (MOST-Wellbeing) and selected individual symptoms. We used group-based trajectory models to identify groups with persistently poor symptoms. RESULTS: The median MOST-Abdo, MOST-DorT and MOST-Wellbeing score were worst at chemotherapy-end but improved and stabilised by 1, 3 and 12 months after treatment, respectively. The median MOST-NTx score peaked at 1 month after treatment before improving, while the median MOST-Psych score did not change substantially over time. Long-term moderate-to-severe fatigue (32%), trouble sleeping (31%), sore hands and feet (21%), pins and needles (20%) and anxiety (18%) were common. Trajectory models revealed groups of patients with persistent symptoms had MOST-DorT scores above 30 and MOST-NTx scores above 40 at treatment-end. CONCLUSIONS: Although many patients report improvements in symptoms by 3 months after first-line chemotherapy for ovarian cancer, patients who score > 30/100 on MOST-S26-DorT or > 40/100 on MOST-S26-NTx at the end of chemotherapy are likely to have persistent symptoms. The MOST could triage this at-risk subset for early intervention.

iMAX: A new tool for assessment of motor axon excitability. A multicenter prospective study.

OBJECTIVE: This study was undertaken to establish by a multicentric approach the reliability of a new technique evaluating motor axon excitability. METHODS: The minimal threshold, the lowest stimulus intensity allowing a maximal response by 1 mA increments (iUP) and then by 0.1 mA adjustments (iMAX) were prospectively derived from three nerves (median, ulnar, fibular) in four university centers (Liège, Marseille, Fraiture, Nice). iMAX procedure was applied in 28 healthy volunteers (twice) and 32 patients with Charcot-Marie-Tooth (CMT1a), chronic inflammatory demyelinating polyneuropathy (CIDP), Guillain-Barré syndrome (SGB) or axonal neuropathy. RESULTS: Healthy volunteers results were not significantly different between centers. Correlation coefficients between test and retest were moderate (> 0.5). Upper limits of normal were established using the 95th percentile. Comparison of volunteers and patient groups indicated significant increases in iMAX parameters especially for the CMT1a and CIDP groups. In CMT1a, iMAX abnormalities were homogeneous at the three stimulation sites, which was not the case for CIDP. CONCLUSIONS: The iMAX procedure is reliable and allows the monitoring of motor axon excitability disorders. SIGNIFICANCE: The iMAX technique should prove useful to monitor motor axonal excitability in routine clinical practice as it is a fast, non-invasive procedure, easily applicable without specific software or devices.