Peripheral polyneuropathy from electrodiagnostic tests: a 10-year etiology and neurophysiology overview.

BACKGROUND: Polyneuropathies are characterized by a symmetrical impairment of the peripheral nervous system, resulting in sensory, motor and/or autonomic deficits. Due to the heterogeneity of causes, an etiological diagnosis for polyneuropathy is challenging. OBJECTIVE: The aim of this study was to determine the main causes of polyneuropathy confirmed by electrodiagnostic (EDX) tests in a tertiary service and its neurophysiological aspects. METHODS: This observational cross-sectional study from a neuromuscular disorders center included individuals whose electrodiagnostic tests performed between 2008 and 2017 confirmed a diagnosis of polyneuropathy. Through analysis of medical records, polyneuropathies were classified according to etiology and neurophysiological aspect. RESULTS: Of the 380 included patients, 59.5% were male, with a median age of 43 years. The main etiologies were: inflammatory (23.7%), hereditary (18.9%), idiopathic (13.7%), multifactorial (11.1%), and diabetes (10.8%). The main electrophysiological patterns were axonal sensorimotor polyneuropathy (36.1%) and "demyelinating and axonal" sensorimotor polyneuropathy (27.9%). Axonal patterns showed greater etiological heterogeneity, with a predominance of idiopathic and multifactorial polyneuropathy, while demyelinating and "demyelinating and axonal" polyneuropathies had a significantly fewer etiologies, with a predominance of hereditary and inflammatory polyneuropathies. CONCLUSION: The main causes of polyneuropathy confirmed by EDX test in this study were those that presented a severe, atypical and/or rapidly progressing pattern. Other causes were hereditary and those that defy clinical reasoning, such as multiple risk factors; some polyneuropathies did not have a specific etiology. EDX tests are useful for etiological diagnosis of rare polyneuropathies, because neurophysiological patterns are correlated with specific etiologies.

Ensuring safety and functionality of electroglottography measurements during dynamic pulmonary MRI.

PURPOSE: To combine vocal tract measurements with dynamic MRI of the lungs to provide fundamental insights into the lung physiology during singing. METHODS: To analyze vocal fold oscillatory patterns during dynamic lung MRI, an electroglottography (EGG) system was modified to allow for simultaneous EGG measurements during MR image acquisitions. A low-pass filter was introduced to suppress residual radiofrequency (RF) coupling into the EGG signal. RF heating was tested in a gel phantom to ensure MR safety, and functionality of the EGG device was assessed in a volunteer experiment at singing frequencies from A5 to A3. In the recorded EGG signals, remaining RF interferences were removed by independent component analysis post processing, and standard EGG parameters such as fundamental frequency, contact quotient and jitter were calculated. In a second volunteer experiment, EGG recordings were compared with lung diameter measurements from 2D time-resolved trueFISP acquisitions. RESULTS: RF heating measurements resulted in less than 1.2°C temperature increase in the gel phantom. EGG parameters measured during MR imaging are within the range of ideal values. In the lung measurement, both the lung diameter and the EGG recordings could be successfully performed with only minimal interference. CONCLUSION: EGG recording is pos sible during dynamic lung MRI, and glottal activity can be studied safely at 1.5T. Magn Reson Med 76:1629-1635, 2016. © 2015 International Society for Magnetic Resonance in Medicine.

Pulsed direct and constant direct currents in the pilocarpine iontophoresis sweat chloride test.

BACKGROUND: The classic sweat test (CST) is the golden standard for cystic fibrosis (CF) diagnosis. Then, our aim was compare the production and volume of sweat, and side effects caused by pulsed direct current (PDC) and constant direct current (CDC). To determine the optimal stimulation time (ST) for the sweat collection. To verify the PDC as CF diagnosis option. METHODS: Prospective study with cross-sectional experimental intervention. Experiment 1 (right arm): PDC and CDC. ST at 10 min and sweat collected at 30 min. Currents of 0.5; 0.75; 1.0 and 1.5 mA and frequencies of 0, 200, 1,000 and 5,000 Hz applied. Experiment 2 (left arm): current of 1.0 mA, ST at 5 and 10 min and sweat collected at 15 and 30 min with frequencies of 0; 200; 1,000 and 5,000 Hz applied Experiments 1 and 2 were performed with current density (CD) from 0.07 to 0.21 mA/cm2. Experiment 3: PDC was used in typical CF patients with two CFTR mutations screened and or with CF diagnosis by rectal biopsy and patients with atypical CF. RESULTS: 48 subjects (79.16% female) with average of 29.54 ± 8.87 years old were enrolled. There was no statistical difference between the interaction of frequency and current in the sweat weight (p = 0.7488). Individually, positive association was achieved between weight sweat and stimulation frequency (p = 0.0088); and current (p = 0.0025). The sweat production was higher for 10 min of stimulation (p = 0.0023). The sweat collection was better for 30 min (p = 0.0019). The skin impedance was not influenced by ST and sweat collection (p > 0.05). The current frequency was inversely associated with the skin impedance (p < 0.0001). The skin temperature measured before stimulation was higher than after (p < 0.0001). In Experiment 3 (29 subjects) the PDC showed better kappa index compared to CDC (0.9218 versus 0.5205, respectively). CONCLUSIONS: The performance of the CST with CDC and PDC with CD of 0.14 to 0.21 mA/cm2 showed efficacy in steps of stimulation and collection of sweat, without side effects. The optimal stimulation time and sweat collection were, respectively, 10 and 30 min.

Safety of repetitive nerve stimulation in patients with cardiac implantable electronic devices.

INTRODUCTION: Pacemakers and implantable cardioverter-defibrillators (ICDs) are vulnerable to inappropriate sensing of electromagnetic interference (EMI), such as from nerve conduction studies. We conducted a prospective study to assess the safety of repetitive nerve stimulation (RNS). METHODS: Fourteen patients undergoing insertion of 10 ICDs and 4 pacemakers under general anesthesia received RNS of the median, axillary, and spinal accessory nerves at 2 HZ and 50 HZ. We recorded detection of EMI and whether or not this resulted in an arrhythmia diagnosis or change in pacing output. RESULTS: EMI was visible in 2 ICDs, without spurious tachyarrhythmia detection. EMI was observed in 3 of the 4 pacemakers, which led to pacing inhibition and a pause in 2, both of which were programmed to a unipolar sensing configuration. CONCLUSIONS: RNS is safe in patients with ICDs. In pacemaker patients, RNS appears safe during bipolar sensing, but caution is recommended in pacemaker patients with unipolar sensing.

Effect of hand size on the stimulation intensities required for median and ulnar sensory nerve conduction studies.

OBJECTIVES: To examine the effect of hand size on median and ulnar sensory nerve conduction study (NCS) stimulation intensities and pain scores. DESIGN: Prospective, single group design to compare main outcomes by using a standard distance of 14cm versus the proximal wrist crease in 3 different hand sizes. SETTING: Electrodiagnostic laboratory in a department of rehabilitation medicine. PARTICIPANTS: Healthy volunteers (N=25) aged 20 to 30 years. INTERVENTIONS: Hand size was determined, based on the distance between the proximal wrist crease and the base of the long finger, resulting in 3 groups (≤11cm, >11-12cm, >12cm) with 12 hands per group. Antidromic median and ulnar sensory NCSs were performed. The nerves were randomly stimulated at the proximal wrist crease and 14cm from the recording electrode. MAIN OUTCOME MEASURES: Supramaximal stimulation intensities and 10-cm visual analog scale (VAS) pain scores at each stimulating site were recorded and compared. RESULTS: Thirty-six hands from 25 young healthy volunteers were studied. There was no correlation between the body mass index (BMI) and stimulation intensity, and BMI and VAS (r<0.3) in both median and ulnar nerves. Overall analysis showed that the stimulation intensity and VAS at 14cm were significantly greater than at the proximal wrist crease. Subgroup analysis showed the same result in all groups for the median sensory NCS, but in only the small hand group for the ulnar sensory NCS. CONCLUSIONS: When the same distance is used for NCSs regardless of patient size, smaller individuals required greater stimulation and reported greater discomfort. This may reflect greater nerve depth and suggests that one size fits all may not be the best approach with NCSs.

False negative and positive motor evoked potentials in one patient: is single motor evoked potential monitoring reliable method? A case report and literature review.

STUDY DESIGN: A case report and literature review. OBJECTIVE: To report a false negative and delayed positive motor-evoked potential (MEP) in 1 patient. SUMMARY OF BACKGROUND DATA: An unreliable MEP can result in fatal outcomes because surgeons have recently begun to depend on the MEP for intraoperative decision-making. METHODS: We report a case of a false MEP during scoliosis surgery that showed false negative and positive MEPs during a series of operations. RESULTS: A 23-year-old man with a history of spondyloepiphyseal dysplasia presented with severe kyphoscoliosis. The initial neurologic examination did not reveal any neurologic abnormalities. Surgical correction and fusion were performed with transcranial MEP monitoring. During the entire procedure, the MEP did not reveal any signs of cord injury. However, lower limb paralysis and paresthesia was observed when the patient awakened. After 2 additional surgical procedures to recover the neurologic deficit, the MEP did not show any signs of cord injury but the patient's neurologic status had recovered slightly. At postoperative day 8, the neurologic status recovered, and a third operation was performed to fix the long rods. However, there were abnormal amplitudes in both lower limbs but the patient's neurologic status was almost normal. CONCLUSION: From our experience of false negative and positive MEP in 1 patient, it is concluded that undesirable events can occur with use of MEP in scoliosis or other spinal surgery. Therefore, we warn the surgeons too heavily rely on the MEP monitoring, and propose a further prospective study as well as use of alternative method that can improve the reliability of single MEP.

Safety of nerve conduction studies in patients with peripheral intravenous lines.

Nerve conduction studies (NCS) may be deferred because of a perceived risk of cardiac arrhythmia in the presence of same-limb peripheral intravenous lines. Patients with implanted pacemakers or defibrillators provide a model in whom this risk can be assessed. Twenty patients, seven with pacemakers and 13 with defibrillators, had peripheral intravenous lines placed during routine care and underwent NCS in the same limb. NCS were performed with the intravenous line clamped and then with saline open to gravity. The implanted cardiac device was interrogated before and after the study. During NCS the surface electrocardiogram and intracardiac electrograms were monitored continuously. Electrical impulses generated during routine NCS were never detected by the sensing amplifiers of the pacemakers/defibrillators and did not affect the programmed settings or interfere with pacing of the device. Routine NCS are safe in patients with same-limb peripheral intravenous lines, even with saline open to gravity.

Infection control: 2008 review and update for electroneurodiagnostic technologists.

In 1995 and 2000, recommendations for infection control in electroneurodiagnostic laboratories were published in this journal (Altman 1995, Altman 2000). This article is an update of those recommendations, reviewing books, journal articles, and information appearing on the Internet from 1995 through 2008. Knowledge of current infection control practices and recommendations is essential for every electroneurodiagnostic technologist, no matter if you work in a hospital, in an ambulatory setting, in an intensive care unit, or in the operating room. All technologists who have direct patient contact are responsible for ensuring effective infection control.

Complications of needle electromyography: hematoma risk and correlation with anticoagulation and antiplatelet therapy.

Electromyography (EMG) is considered a relatively safe procedure based primarily on clinical experience. Literature review reveals few reported complications from bleeding or hematoma formation. No evidence-based guidelines exist for EMG procedures in patients who are taking anticoagulant or antiplatelet medications. The purpose of this study was to determine if patients taking anticoagulant or antiplatelet agents exhibit an increased risk of hematoma formation after routine needle EMG of the tibialis anterior muscle when compared to controls. Study subjects underwent routine needle EMG of the tibialis anterior muscle followed by ultrasound examination to evaluate for the presence of hematoma formation. A mean of 30.8 min elapsed between needle insertion and ultrasound evaluation. A total of 101 patients who were taking warfarin were studied. They had International Normalized Ratio (INR) values at or above 1.5, and two were found to have small, subclinical hematomas. Of 57 patients taking clopidogrel and/or aspirin, 1 was found to have a small, subclinical hematoma. In the control group (51 patients taking neither class of medication), no hematomas were found on ultrasound. This study suggests that hematoma formation from a standard needle EMG is rare. In addition, hematoma formation in our study group of patients on anticoagulant or antiplatelet medications was also uncommon, and no patients with documented hematomas experienced symptoms. These findings should be considered when determining the feasibility of electrodiagnostic evaluation of patients who are taking anticoagulant or antiplatelet medications.

Safety of nerve conduction studies in patients with implanted cardiac devices.

Patients with implanted cardiac devices and their physicians may defer important electrodiagnostic testing because of anxiety about potential negative effects on the device. To determine the safety of routine nerve conduction studies (NCS) in this population, 10 patients with permanent dual-chamber pacemakers of various types and five patients with implanted cardiac defibrillators (ICD) underwent nerve stimulation at sites commonly used during NCS. The implanted cardiac device was interrogated before and after the study and there was continuous monitoring of the surface electrocardiogram (ECG) and atrial and ventricular electrograms. Electrical impulses generated during routine NCS were never detected by the sensing amplifier and did not affect the programmed settings of the implanted cardiac device. We conclude that routine NCS is safe in patients with implanted cardiac pacemakers with bipolar sensing configurations and defibrillators.

F-wave acquisition using low-current stimulation.

The purpose of this study was to assess the feasibility of utilizing low-current stimulation for F-wave generation, thereby avoiding the discomfort of repetitive supramaximal stimulation. We employed the same technique as is used for generating F waves in the conventional way, except for using a stimulating current that was just strong enough to evoke a motor response on the oscilloscope. This usually required a stimulus of about 10-15 mA at 0.2-ms duration. Both median nerves of 30 subjects were evaluated with this technique and with F waves generated by the conventional technique in the same subjects. Amplitudes were larger when using supramaximal current stimulation. However, there was no statistical difference between F-wave latencies, chronodispersion, and persistence (penetrance) elicited with maximal and low-current stimulation. This procedure should represent a significant improvement for patient comfort during electrodiagnostic procedures involving F-wave studies.