Utility and Prognostic Value of Intraoperative Blink Reflex in Trigeminal or Facial Nerve Monitoring in Skull Base Surgeries: A Systematic Review.

BACKGROUND: Blink reflex (BR) is an oligosynaptic reflex that involves the ophthalmic branch of the trigeminal nerve (TN), ipsilateral main sensory and trigeminospinal nuclei, bilateral facial nuclei, and the facial nerves (FNs). Theoretically, as BR tests the function of both TN and FNs simultaneously, it is an ideal tool for monitoring the status of TN and FNs during skull base surgeries. Nevertheless, it has been used only recently in surgeries as the use of anesthesia limits its use. METHODS: For this systematic review, 2 authors input the search terms [(Blink Reflex) AND (Intraoperative Neuromonitoring OR Neuro Intraoperative Monitoring OR Intraoperative OR NIOM OR IONM) AND (skull base surgery OR Facial Nerve OR Trigeminal Nerve OR Microvascular Decompression OR Hemifacial Spasm)] in MEDLINE through its PubMed interface and other search engines. Articles that fulfilled the inclusion and exclusion criteria were obtained and scrutinized. RESULTS: Seven observational articles with a total of 437 participants were included. All 5 studies that described the use of BR in FN surgery noted that intraoperative BR is beneficial, safe, sensitive, specific, and predictive of outcomes, while 2 articles describing patients with trigeminal neuralgia recommended use of BR in microvascular decompression of TN. CONCLUSIONS: Intraoperative BR is a sensitive, specific, and safe monitoring technique that has good predictability of facial paresis and paresthesia among patients undergoing MVD for trigeminal neuralgia and primary hemifacial spasm and patients undergoing cerebellopontine angle tumor resection.

Efficacy and safety of intravenous immunoglobulin retreatment amongst Guillain-Barré syndrome patients who poorly responded to initial IVIG cycle: a systematic review.

INTRODUCTION: Small cross-sectional studies and case reports observed improvement after administration of second IVIG dose (SID) amongst Guillain-Barré Syndrome (GBS) patients not responsive to initial IVIG cycle. Nevertheless, recent clinical trial and larger observational studies did not find any positive effects of SID. Instead, an increased risk of thromboembolism and mortality was noted. The conclusions of these studies however were not robust as confounding and selection bias were present. METHODOLOGY: Two neurologists conducted the search process (KBA and MBP) using the following terms in Medline: [(" Guillain-Barré Syndrome"[MeSH Terms] or GBS or Acute Motor Axonal Neuropathy or Acute Motor Axonal Neuropathy or Acute Inflammatory Demyelinating Polyneuropathy) AND (Poorly Responsive or Poor Prognosis or Progressive)] AND [("Intravenous Immunoglobulin"[MeSH Terms] or IVIG or IGIV) AND (second dose or retreatment or SID)]. RESULTS: Only 7 articles were included in this review. In terms of primary outcomes, although the cross-sectional study found improvement in GBS DS score at 4 weeks (Median GBS DS: 3 vs 5, p = 0.033) and the 2 case series observed improvement after SID, no significant differences between the control and intervention groups were found in the cohort [Early SIV OR: 0.7 (95% CI 0.16-3.04), Late SIV OR: 0.66 (CI: 0.18-2.5)] and clinical trial studies (Adjusted OR: 1.4 (95% CI:0.6-3.3, p = 0.45). Moreover, 4 patients who died in the clinical trial were from the intervention group. CONCLUSION: Based on studies with research designs of higher quality, SID is not effective in the management of GBS patients who poorly responded to initial IVIG. Nevertheless, an adequately powered, randomized, double-blinded, placebo-controlled clinical trial, using GBS-DS of 3 and above after first IVIG dose should be done to effectively establish the efficacy and safety of SID as intervention for this cohort of patients.

Clinical profile and outcomes of tetanus patients in a tertiary hospital in the Philippines: a ten-year retrospective study.

BACKGROUND: Tetanus is a life-threatening but preventable neurologic disorder characterized by trismus and muscle spasms. Despite its decreasing global incidence, it remains to be endemic in resource-limited settings such as the Philippines. This study aimed to determine the incidence, demographic characteristics, risk factors, clinical presentation, management, complications, and outcomes of non-neonatal tetanus cases in a tertiary hospital in the Philippines. It also aimed to compare the clinical profile and outcomes between the adult and pediatric subgroups. METHODS: This study used a retrospective cross-sectional design including all adult and pediatric non-neonatal tetanus patients admitted at the University of the Philippines - Philippine General Hospital from January 2012 to June 2023. Data was extracted from department censuses and inpatient charts. RESULTS: One hundred thirty-eight cases were included. The incidence rate was 0.03%, while mortality rate was 29%. Majority of patients were males presenting with trismus and spasms after sustaining a puncture wound. Chronic hypertension was associated with an increased hazard of death by 4.5 times (p = 0.004), while treatment with magnesium sulfate was associated with a decreased hazard of death by 35 times (p = 0.005). The mode of infection and the medications administered differed between the adult and pediatric subgroups. CONCLUSIONS: Although the total number of cases has decreased over the past decade, tetanus remains to have a high incidence and mortality rate in the Philippines. Increasing vaccination coverage, improving public awareness, and educating health professionals can help reduce morbidity and mortality from this disease.

Ranking Alpha Lipoic Acid and Gamma Linolenic Acid in Terms of Efficacy and Safety in the Management of Adults With Diabetic Peripheral Neuropathy: A Systematic Review and Network Meta-analysis.

OBJECTIVES: Current medications for diabetic neuropathy (DN) recommended by the American Diabetes Association and American Academy of Neurology do not address the pathologic process of denervation among DN patients, because ancillary treatments, such as reactive oxygen scavengers, may be needed. The purpose of this work was to summarize the available evidence about the efficacy and safety of alpha lipoic acid (ALA) and gamma linolenic acid (GLA) in the management of DN. METHODS: Using the search terms [(alpha lipoic acid or ALA or thioctic acid or thioctacid) or (gamma linolenic acid or GLA)] AND [(diabetes or diabetes mellitus) AND (polyneuropathy or neuropathy or sensorimotor polyneuropathy or radiculopathy)], 11 studies were included in this review and combined meta-analysis. RESULTS: Eight of the 11 articles (73%) reported significant benefit of ALA vs placebo. In the meta-analysis, the Total Symptom Score (TSS) for ALA 600 mg/day (ALA600) was 1.05 points lower (standard mean difference [SMD] -1.05, 95% confidence interval [CI] -2.07 to -0.04, p=0.04, I2=98.18%) compared with control at the end of the study. In the network meta-analysis, ALA600 (SMD -1.68, 95% CI -2.8 to -0.6) and GLA (SMD -2.39, CI -4.3 to -0.5) had significantly lower TSSs compared with placebo. Moreover, GLA had the highest probability of being the best (52.7%) for improving DN symptoms. In all studies, most adverse events include gastrointestinal disturbances. In terms of tolerability, no differences were detected between ALA and control groups. CONCLUSION: ALA and GLA appear to be safe and efficacious biofactors for improvement of DN symptoms.

Neuromuscular Ultrasound Findings of Myokymia in a Young Woman With Generalized Anti-LGI-1 and Anti-Caspr2 Antibodies Negative Isaac Syndrome.

ABSTRACT: Isaac syndrome is one of the rare peripheral nerve hyperexcitability (PNH) syndromes, which manifests with gross fasciculations, muscle undulation, twitching, and cramps, with or without autonomic and sensory symptoms. The diagnosis relies on characteristic electromyogram findings and the presence of anti-leucine-rich glial inactivated 1 and anti-contactin-associated protein 2 antibodies in the serum. Here, we report the case of a 21-year-old woman, who presented with extremities and tongue myokymia whose electromyogram findings were compatible with PNH, albeit seronegative for antibodies. Neuromuscular ultrasound was performed showing high-frequency rotatory, to-and-fro, high-amplitude movement of superficial and deep muscle fascicles, more prominent in the proximal than distal muscles. Neuromuscular ultrasound may be a useful adjunct in the diagnosis of PNH.

Characteristic and management motor neuron disease in the largest tertiary hospital in the Philippines: A one-year period cross sectional analytic study.

BACKGROUND: Motor neuron disease (MND) is largely understudied in many underdeveloped and developing countries, including the Philippines. The practice and management of MND is generally insufficient, and thus, the quality of life of these patients are consequently compromised. OBJECTIVES: The aim of this study is to determine the clinical profile and describe the management of MND patients seen in the largest tertiary hospital in the Philippines for one year. METHODS: This is a cross-sectional study of MND patients diagnosed clinically and via electromyogram-nerve conduction study (EMG NCS) in the Philippine General Hospital (PGH) from January to December 2022. Clinical characteristics, diagnostics and management information were obtained and summarized. RESULTS: The incidence of MND in our neurophysiology unit was 4.3% (28/648), with amyotrophic lateral sclerosis (ALS) being the most common variant (67.9%, n = 19). Male to Female ratio was 1:1, with the median age of onset of 55 (36-72) years old and median onset duration to diagnosis of 1.5 (0.25-8) years. Limb onset was more prevalent (82.14%, n = 23) with upper limbs initially involved (79.1%, n = 18). Split hand syndrome was found in almost half (53.6%) of the patients. The median ALS functional rating score-revised (ALSFRS-R) and medical research council (MRC) scores were 34 (8-47) and 42(16-60) respectively while the median King's clinical stage was 3 (1-4). Only half of the patients were able to undergo magnetic resonance imaging (MRI) and only one had neuromuscular ultrasound. Only one of the 28 patients was able to take riluzole, and only one was on oxygen support. None had gastrostomy and none used non-invasive ventilation. CONCLUSION: This study showed that the management of MND in the Philippines is largely inadequate and further improvement in the health care system in handling rare neurologic cases must be implemented to enhance their quality of life.

Spatial and Temporal Protein Modules Signatures Associated with Alzheimer Disease in 3xTg-AD Mice Are Restored by Early Ubiquinol Supplementation.

Despite its robust proteopathic nature, the spatiotemporal signature of disrupted protein modules in sporadic Alzheimer's disease (AD) brains remains poorly understood. This considered oxidative stress contributes to AD progression and early intervention with coenzyme Q10 or its reduced form, ubiquinol, delays the progression of the disease. Using MALDI-MSI and functional bioinformatic analysis, we have developed a protocol to express how deregulated protein modules arise from hippocampus and cortex in the AD mice model 3xTG-AD in an age-dependent manner. This strategy allowed us to identify which modules can be efficiently restored to a non-pathological condition by early intervention with ubiquinol. Indeed, an early deregulation of proteostasis-related protein modules, oxidative stress and metabolism has been observed in the hippocampus of 6-month mice (early AD) and the mirrored in cortical regions of 12-month mice (middle/late AD). This observation has been validated by IHC using mouse and human brain sections, suggesting that these protein modules are also affected in humans. The emergence of disrupted protein modules with AD signature can be prevented by early dietary intervention with ubiquinol in the 3xTG-AD mice model.

Assessment of genotoxicity induced by subchronic exposure to graphene in HaCaT human skin cell line.

The applications of graphene-based materials (GBMs) and their processing involve prolonged contact with cellular barriers such as human skin. Even though the potential cytotoxicity of graphene has been studied in recent years, the impact of long-term graphene exposure has rarely been explored. We tested in the HaCaT epithelial cells, in vitro, the effect of subchronic treatments with sublethal doses of four different, well-characterized GBMs, two commercial graphene oxides (GO) and two few-layer graphenes (FLG). Cells were exposed weekly to low doses of the GBMs for 14 days, 30 days, 3 months, and 6 months. GBMs-cells uptake was assessed by confocal microscopy. Cell death and cell cycle were determined by fluorescence microscopy and cytometry. DNA damage was measured by comet assay and γ-H2AX staining, followed by the determination of p-p53 and p-ATR by immunolabeling. Subchronic exposure to different GBMs at noncytotoxic doses has potential genotoxic effects on HaCaT epithelial cells that can be recovered depending on the GBM and exposure time. Specifically, GO-induced genotoxicity can be detected after 14 and 30 days from treatment. At this time, FLG appears less genotoxic than GO, and cells can recover more quickly when genotoxic pressure disappears after some days of removal of the GBM. Long-term exposure, 3 and 6 months, to different GBMs induces permanent, nonreversible, genotoxic damage comparable to the exerted by arsenite. This should be considered for the production and future applications of GBMs in scenarios where low concentrations of the material interact chronically with epithelial barriers.

Methotrexate in generalized myasthenia gravis: a systematic review.

Current myasthenia gravis guidelines recommend the use of azathioprine as first-line steroid sparing agent. However, due to its high cost, compliance to azathioprine is low in developing countries. To determine the efficacy and safety of the cheaper methotrexate as an alternative immunosuppressant, Medline/Pubmed, Embase and Cochrane databases and references were searched for clinical trials and observational studies using the search terms: "Myasthenia OR Myasthenia Gravis OR anti AchR antibody positive Myasthenia Gravis OR anti-MuSK antibody Myasthenia Gravis OR MG" AND "Methotrexate". Of 78 possible articles, only 4 were selected using the following eligibility criteria: population: generalized MG patients; intervention: methotrexate; and outcome: effectiveness, steroid sparing efficacy and adverse effects. Two clinical trials and one observational study noted improvement in different MG outcomes in patients given methotrexate. While one randomized controlled clinical trial concluded that methotrexate has no steroid sparing benefit, a single blinded clinical trial established that methotrexate was a better steroid sparing agent than azathioprine starting at 10th month of use. Adverse effects were rare with non-specific pain and elevated transaminases as the most common complaints. Based on available evidence, MTX may be a safe and effective alternative to AZA as steroid sparing agent in developing countries.

Easy and Versatile Synthesis of Bulk Quantities of Highly Enriched 13C-Graphene Materials for Biological and Safety Applications.

The preparation of bulk quantities of 13C-labeled graphene materials is relevant for basic investigations and for practical applications. In addition, 13C-labeled graphene materials can be very useful in biological and environmental studies, as they may allow the detection of graphene or its derivatives in cells or organs. In this paper, we describe the synthesis of 13C-labeled graphene materials (few-layer graphene, FLG, and graphene oxide, GO) on a tens of mg scale, starting from 13C-labeled methane to afford carbon fibers, followed by liquid-phase exfoliation (FLG) or oxidation (GO). The materials have been characterized by several analytical and microscopic techniques, including Raman and nuclear magnetic resonance spectroscopies, thermogravimetric analysis, X-ray photoelectron spectroscopy, and X-ray powder diffraction. As a proof of concept, the distribution of the title compounds in cells has been investigated. In fact, the analysis of the 13C/12C ratio with isotope ratio mass spectrometry (IRMS) allows the detection and quantification of very small amounts of material in cells or biological compartments with high selectivity, even when the material has been degraded. During the treatment of 13C-labeled FLG with HepG2 cells, 4.1% of the applied dose was found in the mitochondrial fraction, while 4.9% ended up in the nuclear fraction. The rest of the dose did not enter into the cell and remained in the plasma membrane or in the culture media.

CoQ10 reduces glioblastoma growth and infiltration through proteome remodeling and inhibition of angiogenesis and inflammation.

PURPOSE: Most monotherapies available against glioblastoma multiforme (GBM) target individual hallmarks of this aggressive brain tumor with minimal success. In this article, we propose a therapeutic strategy using coenzyme Q10 (CoQ10) as a pleiotropic factor that crosses the blood-brain barrier and accumulates in cell membranes acting as an antioxidant, and in mitochondrial membranes as a regulator of cell bioenergetics and gene expression. METHODS: Xenografts of U251 cells in nu/nu mice were used to assay tumor growth, hypoxia, angiogenesis, and inflammation. An orthotopic model was used to explore microglial infiltration, tumor growth, and invasion into the brain parenchyma. Cell proliferation, migration, invasion, proteome remodeling, and secretome were assayed in vitro. Conditioned media were used to assay angiogenesis, monocyte chemoattraction, and differentiation into macrophages in vitro. RESULTS: CoQ10 treatment decreased tumor volume in xenografts and orthotopic models, although its effect on tumor cell proliferation was not direct. Tumors from mice treated with CoQ10 were less hypoxic and vascularized, having less infiltration from inflammatory cells. Treatment-induced downregulation of HIF-1α and NF-kB led to a complete remodeling of the tumor cells proteome and secretome, impacting angiogenesis, monocyte infiltration, and their differentiation into macrophages. Besides, tumor cell migration and invasion were drastically restricted by mechanisms involving modulation of the actin cytoskeleton and downregulation of matrix metalloproteases (MMPs). CONCLUSIONS: CoQ10 has a pleiotropic effect on GBM growth, targeting several hallmarks simultaneously. Thus, its integration into current treatments of this fatal disease should be considered.

Chronic Myopathy as the Initial Manifestation of Thyrotoxicosis: A Report of 2 Cases.

INTRODUCTION: Rarely, hyperthyroidism will initially present with chronic myopathy characterized by progressive and sometimes fluctuating proximal muscle weakness, along with elevated creatine kinase and myopathic pattern in the electromyogram, mimicking other muscle and neuromuscular junction disorders with poorer prognosis. CASES: Here, we present 2 young patients who complained of 1-4 months duration of chronic proximal muscle lower extremity weakness, supported by elevated creatine kinase and myopathic pattern in electromyogram, who later found to have markedly low thyroid-stimulating hormone, high free T3 and free T4, enlarged thyroid gland on ultrasound, and elevated anti-thyroid-stimulating hormone receptor antibody, characteristic of Grave disease. CONCLUSIONS: Although rare, thyrotoxicosis should always be ruled out in a patient with chronic myopathy because this has better prognosis than other primary muscle conditions presenting similarly.

Incidence and risk factors for stroke in patients with COVID-19 in the Philippines: An analysis of 10,881 cases.

BACKGROUND: While most large studies on the possible association of COVID-19 and stroke were done in high-income countries, only a few studies consisting of small sample populations have been done in low- to middle-income countries like the Philippines. OBJECTIVES: To determine the risk factors of stroke among hospitalized COVID19 patients in the Philippines; to determine the possible association between these risk factors and stroke among the same cohort; and to determine if there is an association between mortality and stroke in this same group. METHODOLOGY: We obtained relevant clinical and neurological, including stroke data from the Philippine CORONA study, an observational study involving 10,881 patients with COVID-19 admitted in 37 referral hospitals from all over the Philippines. RESULTS: The incidence of stroke among patients with COVID-19 was 3.4% (n = 367). There were more deaths among patients with stroke and COVID-19 than those without stroke and COVID-19 (42.2% vs 14.7%, p < 0.01). In addition, more patients with stroke were admitted in the ICU (43.3% vs 15.0%, p < 0.01) regardless of cause. Smoking (OR: 1.5, 95% CI: 1.3 to 1.7, p < 0.0001), hypertension (OR:1.75, 95% CI:1.53 to 1.97, p < 0.0001), presence of heart failure (OR: 1.4, 95% CI: 1.07 to 1.86, p = 0.01), presence of any neurologic co-morbidities (OR: 1.4, 95% CI:1.11 to 1.46, p = 0.004), and history of stroke (OR:2.3, 95% CI:1.82 to 2.97, p < 0.0001) had direct significant correlation with stroke; while being a health care worker (OR: 0.5, 95% CI: 0.33 to 0.70, p < 0.0004) had an inverse significant association with stroke. CONCLUSION: COVID-19 stroke patients in the Philippines have a higher mortality and ICU admission rates than patients with COVID-19 alone or COVID-19 stroke patients from developed countries. Our cohort has similar cardiovascular and metabolic risk factors to western patients with stroke, highlighting that COVID-19 may only have a small contribution to stroke incidence.

Relationship between motor cortical and peripheral axonal hyperexcitability in amyotrophic lateral sclerosis.

BACKGROUND: Previous studies have shown that patients with amyotrophic lateral sclerosis (ALS) have hyperexcitability in both the motor cortex and peripheral motor axons, but the relationship between central and peripheral excitability has not been fully disclosed. METHODS: Threshold tracking transcranial magnetic stimulation (TMS) and motor nerve excitability testing were prospectively performed in 53 patients with ALS and 50 healthy subjects, and their relations to compound muscle action potential (CMAP) amplitude and revised ALS Functional Rating Scale were cross-sectionally analysed. RESULTS: Compared with controls, patients with ALS showed both cortical and peripheral hyperexcitability; TMS showed reduced short-interval intracortical inhibition (interstimulus interval 1-7 ms) (p<0.001) and shortened silent period (p<0.05), and median nerve excitability testing revealed greater changes in depolarising threshold electrotonus (TEd) and greater superexcitability (p<0.0001, both), suggesting reduced axonal potassium currents. Significant correlations between cortical and peripheral excitability indices were not found. Greater changes in TEd (90-100 ms) (R=-0.33, p=0.03) and superexcitability (R=0.36, p=0.01) were associated with smaller amplitude of CMAP, whereas cortical excitability indices had no correlation with CMAP amplitude. More rapid motor functional decline was associated with only greater TEd (90-100 ms) (ß=0.46, p=0.001). CONCLUSIONS: Our results suggest that in ALS, cortical excitability is continuously high regardless of the extent of the peripheral burden, but peripheral hyperexcitability is associated with the extent of the peripheral burden and disease evolution speed. Alterations of ion channel function may play an important role in ALS pathophysiology.

Facial Diplegia as the Sole Manifestation of Post-Vaccination Guillain-Barre Syndrome: A Case Report and Literature Review.

Introduction: Recently, a large study concluded that certain brands of vaccines may increase the risk of Bell's palsy and Guillain Barre Syndrome (GBS). As to whether vaccination after COVID-19 modify the risk of Bell's palsy or GBS has not yet been studied. Case: Here we report a 35 years old COVID-19 survivor whom in less than 2 weeks after his second dose of inactivated SARS-CoV2 vaccine, developed bilateral facial nerve paralysis. In addition, he had hyperacusis, dysgeusia and decreased lacrimation without any signs of sensory and motor deficits in the limbs. His limb nerve conduction study (NCS) was unremarkable in contrast to bilaterally abnormal facial NCS and blink reflexes. Although he had negative anti-GM1 IgG and IgM antibodies, he has marked albuminocytologic dissociation, classic of acute inflammatory demyelinating polyneuropathy. Conclusion: To date, there were no similar case reports which published the occurrence of facial diplegia as sole manifestation of GBS in a post COVID-19 patient who recently completed vaccination. We believe that molecular mimicry, induced by magnified immune response from both COVID-19 and vaccination may have caused the symptom.

Rapid and efficient testing of the toxicity of graphene-related materials in primary human lung cells.

Graphene and its derivative materials are manufactured by numerous companies and research laboratories, during which processes they can come into contact with their handlers' physiological barriers-for instance, their respiratory system. Despite their potential toxicity, these materials have even been used in face masks to prevent COVID-19 transmission. The increasingly widespread use of these materials requires the design and implementation of appropriate, versatile, and accurate toxicological screening methods to guarantee their safety. Murine models are adequate, though limited when exploring different doses and lengths of exposure-as this increases the number of animals required, contrary to the Three R's principle in animal experimentation. This article proposes an in vitro model using primary, non-transformed normal human bronchial epithelial (NHBE) cells as an alternative to the most widely used model to date, the human lung tumor cell line A549. The model has been tested with three graphene derivatives-graphene oxide (GO), few-layer graphene (FLG), and small FLG (sFLG). We observed a cytotoxic effect (necrosis and apoptosis) at early (6- and 24-h) exposures, which intensified after seven days of contact between cells and the graphene-related materials (GRMs)-with cell death reaching 90% after a 5 µg/mL dose. A549 cells are more resistant to necrosis and apoptosis, yielding values less than half of NHBE cells at low concentrations of GRMs (between 0.05 and 5 µg/mL). Indeed, GRM-induced cell death in NHBE cells is comparable to that induced by toxic compounds such as diesel exhaust particles on the same cell line. We propose NHBE as a suitable model to test GRM-induced toxicity, allowing refinement of the dose concentrations and exposure timings for better-designed in vivo mouse assays.

Subchronic Graphene Exposure Reshapes Skin Cell Metabolism.

In recent years, the toxicity of graphene-related materials (GRMs) has been evaluated in diverse models to guarantee their safety. In most applications, sublethal doses of GRMs contact human barriers such as skin in a subchronic way. Herein, the subchronic effect (30 day exposure) of three GRMs (GO 1, GO 2, and FLG) with different oxidation degrees and sizes was studied. The effects of these materials on human skin cells, HaCaTs, were assayed through high-throughput metabolic-based readout and other cell-based assays. A differential effect was found between the different GRMs. GO 2 induced a metabolic remodeling in epithelial cells, increasing the level of tricarboxylic acid components, mirrored by increased cell proliferation and changes in cell phenotype. The oxidation degree, size, and method of manufacture of GRMs dictated harmful effects on cell metabolism and behavior generated by nontoxic exposures. Therefore, a "safe by design" procedure is necessary when working with these nanomaterials.

Different patterns of sensory nerve involvement in chronic inflammatory demyelinating polyneuropathy subtypes.

INTRODUCTION/AIMS: Among subtypes of chronic inflammatory demyelinating polyneuropathy (CIDP), different immune pathophysiologies have been proposed. In this study, sensory nerve conduction studies were compared among clinical subtypes to attempt to better understand the underlying pathophysiology. METHODS: A total of 138 patients with CIDP was classified into clinical subtypes: typical CIDP (N = 68), multifocal CIDP (N = 27), or other (N = 2). Patients with immunoglobulin M (IgM) neuropathy anti-myelin-associated glycoprotein neuropathy (MAG; N = 19) were also included as disease controls. Sensory nerve action potentials (SNAPs) were recorded in the median, ulnar, and superficial radial and sural nerves. RESULTS: SNAP amplitudes (P < .05) and conduction velocities (P < .01) in the median nerve and conduction velocities (P < .05) in the ulnar nerve were lower in typical CIDP than in multifocal CIDP, whereas those in the radial and sural nerves were comparable in each group. Low median and normal sural SNAP amplitudes were more common in typical CIDP (P < .005) than in multifocal CIDP, suggesting predominant involvement at terminal portions of the nerves. DISCUSSION: Terminal portions of sensory nerves are preferentially affected in typical CIDP compared with multifocal CIDP. These findings might be partially explained by the hypothesis of antibody-mediated demyelination in typical CIDP at the regions where the blood-nerve barrier is anatomically deficient, whereas multifocal CIDP predominantly affects the nerve trunks, largely due to cell-mediated demyelination, with disruption of the blood-nerve barrier.

Fatigue and activity-dependent conduction block in neuromuscular disorders.

Objective: Fatigue is a major disabling problem in patients with neuromuscular disorders. Both nerve demyelination and increased axonal branching associated with collateral sprouting reduce the safety factor for impulse transmission and could cause activity-dependent hyperpolarization and conduction block during voluntary contraction, and thus fatigue. This study aimed to investigate whether activity-dependent conduction block is associated with fatigue in demyelinating neuropathies and lower motor neuron disorders. Methods: This study included 31 patients (17 with chronic inflammatory demyelinating polyneuropathy [CIDP] and 14 with spinal and bulbar muscular atrophy [SBMA]). Sixteen healthy subjects served as normal controls. Fatigue was assessed using the Fatigue Scale for Motor and Cognitive Functions (FSMC). Compound muscle action potential (CMAP) recording and nerve excitability testing after median nerve stimulation in the wrist were performed before and after maximal voluntary contraction of the abductor pollicis brevis for 1 min. Results: Patients with CIDP/SBMA had prominent fatigue with higher FSMC motor scores (P < 0.0001) than normal controls. After voluntary contractions, CMAP amplitudes decreased significantly in four of the 17 patients with CIDP and one of the 14 patients with SBMA. The reduction in CMAP amplitude was associated with the fatigue score in the motor but not in the cognitive domain. After voluntary contraction, excitability testing showed axonal hyperpolarization in the normal and CIDP/SBMA groups. Conclusions: In CIDP or SBMA, fatigue is caused by voluntary contraction-induced membrane hyperpolarization and conduction block, presumably due to the critically lowered safety factor due to demyelination or increased axonal branching. Significance: Peripheral fatigue can be objectively assessed using CMAP amplitudes and nerve excitability testing.