Decompressive craniectomy plus best medical treatment versus best medical treatment alone for spontaneous severe deep supratentorial intracerebral haemorrhage: a randomised controlled clinical trial.

BACKGROUND: It is unknown whether decompressive craniectomy improves clinical outcome for people with spontaneous severe deep intracerebral haemorrhage. The SWITCH trial aimed to assess whether decompressive craniectomy plus best medical treatment in these patients improves outcome at 6 months compared to best medical treatment alone. METHODS: In this multicentre, randomised, open-label, assessor-blinded trial conducted in 42 stroke centres in Austria, Belgium, Finland, France, Germany, the Netherlands, Spain, Sweden, and Switzerland, adults (18-75 years) with a severe intracerebral haemorrhage involving the basal ganglia or thalamus were randomly assigned to receive either decompressive craniectomy plus best medical treatment or best medical treatment alone. The primary outcome was a score of 5-6 on the modified Rankin Scale (mRS) at 180 days, analysed in the intention-to-treat population. This trial is registered with ClincalTrials.gov, NCT02258919, and is completed. FINDINGS: SWITCH had to be stopped early due to lack of funding. Between Oct 6, 2014, and April 4, 2023, 201 individuals were randomly assigned and 197 gave delayed informed consent (96 decompressive craniectomy plus best medical treatment, 101 best medical treatment). 63 (32%) were women and 134 (68%) men, the median age was 61 years (IQR 51-68), and the median haematoma volume 57 mL (IQR 44-74). 42 (44%) of 95 participants assigned to decompressive craniectomy plus best medical treatment and 55 (58%) assigned to best medical treatment alone had an mRS of 5-6 at 180 days (adjusted risk ratio [aRR] 0·77, 95% CI 0·59 to 1·01, adjusted risk difference [aRD] -13%, 95% CI -26 to 0, p=0·057). In the per-protocol analysis, 36 (47%) of 77 participants in the decompressive craniectomy plus best medical treatment group and 44 (60%) of 73 in the best medical treatment alone group had an mRS of 5-6 (aRR 0·76, 95% CI 0·58 to 1·00, aRD -15%, 95% CI -28 to 0). Severe adverse events occurred in 42 (41%) of 103 participants receiving decompressive craniectomy plus best medical treatment and 41 (44%) of 94 receiving best medical treatment. INTERPRETATION: SWITCH provides weak evidence that decompressive craniectomy plus best medical treatment might be superior to best medical treatment alone in people with severe deep intracerebral haemorrhage. The results do not apply to intracerebral haemorrhage in other locations, and survival is associated with severe disability in both groups. FUNDING: Swiss National Science Foundation, Swiss Heart Foundation, Inselspital Stiftung, and Boehringer Ingelheim.

Tranexamic Acid for Intracerebral Hemorrhage in Patients on Non-Vitamin K Antagonist Oral Anticoagulants (TICH-NOAC): A Multicenter, Randomized, Placebo-Controlled, Phase 2 Trial.

BACKGROUND: Evidence-based hemostatic treatment for intracerebral hemorrhage (ICH) associated with non-vitamin K antagonist oral anticoagulants (NOACs) is lacking. Tranexamic acid (TXA) is an antifibrinolytic drug potentially limiting hematoma expansion. We aimed to assess the efficacy and safety of TXA in NOAC-ICH. METHODS: We performed a double-blind, randomized, placebo-controlled trial at 6 Swiss stroke centers. Patients with NOAC-ICH within 12 hours of symptom onset and 48 hours of last NOAC intake were randomized (1:1) to receive either intravenous TXA (1 g over 10 minutes followed by 1 g over 8 hours) or matching placebo in addition to standard medical care via a centralized Web-based procedure with minimization on key prognostic factors. All participants and investigators were masked to treatment allocation. Primary outcome was hematoma expansion, defined as ≥33% relative or ≥6 mL absolute volume increase at 24 hours and analyzed using logistic regression adjusted for baseline hematoma volume on an intention-to-treat basis. RESULTS: Between December 12, 2016, and September 30, 2021, we randomized 63 patients (median age, 82 years [interquartile range, 76-86]; 40% women; median hematoma volume, 11.5 [4.8-27.4] mL) of the 109 intended sample size before premature trial discontinuation due to exhausted funding. The primary outcome did not differ between TXA (n=32) and placebo (n=31) arms (12 [38%] versus 14 [45%]; adjusted odds ratio, 0.63 [95% CI, 0.22-1.82]; P=0.40). There was a signal for interaction with onset-to-treatment time (Pinteraction=0.024), favoring TXA when administered within 6 hours of symptom onset. Between the TXA and placebo arms, the proportion of participants who died (15 [47%] versus 13 [42%]; adjusted odds ratio, 1.07 [0.37-3.04]; P=0.91) or had major thromboembolic complications within 90 days (4 [13%] versus 2 [6%]; odds ratio, 1.86 [0.37-9.50]; P=0.45) did not differ. All thromboembolic events occurred at least 2 weeks after study treatment, exclusively in participants not restarted on oral anticoagulation. CONCLUSIONS: In a smaller-than-intended NOAC-ICH patient sample, we found no evidence that TXA prevents hematoma expansion, but there were no major safety concerns. Larger trials on hemostatic treatments targeting an early treatment window are needed for NOAC-ICH. REGISTRATION: URL: https://clinicaltrials.gov; Unique identifier: NCT02866838.

Herniation World Federation of Neurosurgical Societies Scale Improves Prediction of Outcome in Patients With Poor-Grade Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND: Favorable outcomes are seen in up to 50% of patients with World Federation of Neurosurgical Societies (WFNS) grade V aneurysmal subarachnoid hemorrhage. Therefore, the usefulness of the current WFNS grading system for identifying the worst scenarios for clinical studies and for making treatment decisions is limited. We previously modified the WFNS scale by requiring positive signs of brain stem dysfunction to assign grade V. This study aimed to validate the new herniation WFNS grading system in an independent prospective cohort. METHODS: We conducted an international prospective multicentre study in poor-grade aneurysmal subarachnoid hemorrhage patients comparing the WFNS classification with a modified version-the herniation WFNS scale (hWFNS). Here, only patients who showed positive signs of brain stem dysfunction (posturing, anisocoric, or bilateral dilated pupils) were assigned hWFNS grade V. Outcome was assessed by modified Rankin Scale score 6 months after hemorrhage. The primary end point was the difference in specificity of the WFNS and hWFNS grading with respect to poor outcomes (modified Rankin Scale score 4-6). RESULTS: Of the 250 patients included, 237 reached the primary end point. Comparing the WFNS and hWFNS scale after neurological resuscitation, the specificity to predict poor outcome increased from 0.19 (WFNS) to 0.93 (hWFNS) (McNemar, P<0.001) whereas the sensitivity decreased from 0.88 to 0.37 (P<0.001), and the positive predictive value from 61.9 to 88.3 (weighted generalized score statistic, P<0.001). For mortality, the specificity increased from 0.19 to 0.93 (McNemar, P<0.001), and the positive predictive value from 52.5 to 86.7 (weighted generalized score statistic, P<0.001). CONCLUSIONS: The identification of objective positive signs of brain stem dysfunction significantly improves the specificity and positive predictive value with respect to poor outcome in grade V patients. Therefore, a simple modification-presence of brain stem signs is required for grade V-should be added to the WFNS classification. REGISTRATION: URL: https://clinicaltrials.gov; Unique identifier: NCT02304328.

Ultrasound Perfusion Imaging for the Detection of Cerebral Hypoperfusion After Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND: Delayed cerebral ischemia increases mortality and morbidity after aneurysmal subarachnoid hemorrhage (aSAH). Various techniques are applied to detect cerebral vasospasm and hypoperfusion. Contrast-enhanced ultrasound perfusion imaging (UPI) is able to detect cerebral hypoperfusion in acute ischemic stroke. This prospective study aimed to evaluate the use of UPI to enable detection of cerebral hypoperfusion after aSAH. METHODS: We prospectively enrolled patients with aSAH and performed UPI examinations every second day after aneurysm closure. Perfusion of the basal ganglia was outlined to normalize the perfusion records of the anterior and posterior middle cerebral artery territory. We applied various models to characterize longitudinal perfusion alterations in patients with delayed ischemic neurologic deficit (DIND) across the cohort and predict DIND by using a multilayer classification model. RESULTS: Between August 2013 and December 2015, we included 30 patients into this prospective study. The left-right difference of time to peak (TTP) values showed a significant increase at day 10-12. Patients with DIND demonstrated a significant, 4.86 times increase of the left-right TTP ratio compared with a mean fold change in patients without DIND of 0.9 times (p = 0.032). CONCLUSIONS: UPI is feasible to enable detection of cerebral tissue hypoperfusion after aSAH, and the left-right difference of TTP values is the most indicative result of this finding.

Electrical Stimulation for Cerebral Vasospasm After Subarachnoid Hemorrhage: A Systematic Review.

OBJECTIVES: Cerebral vasospasm is a severe and potentially lethal complication in patients with subarachnoid hemorrhage (SAH). Its pathogenesis is still not completely understood. The efficacy of current treatments, such as triple-H therapy or calcium channel blockers, is unsatisfactory, and a new therapy model would therefore be valuable. Electrical stimulation may have a considerable influence on cerebrovascular innervation. This systematic review gives an overview of the studies that have applied electrical stimulation in models of cerebral vasospasm. MATERIALS AND METHODS: We performed a systematic review of the literature, searching PubMed and Ovid Embase with the keywords "electric stimulation," "cerebral vasospasm," "subarachnoid hemorrhage," "sympathetic," and "parasympathetic." Additional papers were identified from the reference lists of the articles identified in the literature search. RESULTS: Increased cerebral blood flow (CBF) is a widely observed effect of spinal cord stimulation and sphenopalatine ganglion stimulation in models of physiological conditions or experimental cerebral vasospasm. Most studies were conducted in animals, 15 under physiological conditions and 11 in animals with SAH. Eight studies in humans were identified that examined the stimulation effect on CBF under physiological conditions. Only two studies looked at patients after SAH: one applied spinal cord stimulation (SCS) and the other transcutaneous electrical neurostimulation. Different mechanisms leading to stimulation-induced CBF increase that were discussed included "reversible functional sympathectomy," activation of brainstem vasomotor centers, involvement of central ascending pathways, release of neurohumoral factors, and interaction with sympathetic, parasympathetic, and trigeminal innervation. The results indicate that electrical stimulation is a promising procedure for prevention and treatment of cerebral vasospasm. CONCLUSION: Electrical stimulation, especially SCS and sphenopalatine ganglion stimulation, is a promising adjunct for existing therapies for vasospasm after SAH. Further experiments and prospective clinical studies are needed to establish its potential usefulness as a therapy or prevention option.

Effect of intermittent high-frequency stimulation on muscle velocity recovery cycle recordings.

The technique of multifiber muscle velocity recovery cycle recordings was developed as a diagnostic tool to assess muscle membrane potential changes and ion channel function in vivo. This study was undertaken to assess the impact of intermittent high-frequency stimulation on muscle velocity recovery cycle components and to study whether the changes can be modified by endurance training. We recorded muscle velocity recovery cycles with 1 and 2 conditioning stimuli in the left tibialis anterior muscle in 15 healthy subjects during intermittent 37-Hz stimulation and analyzed its effects on the different phases of supernormality. Recordings were conducted before and after 2-wk endurance training. Training effect was assessed by measuring the difference in endurance time, peak force, and limb circumference. Muscle velocity recovery cycle recordings during intermittent high-frequency stimulation were successfully recorded in 12 subjects. Supernormality for interstimulus intervals shorter than 15 ms (early supernormality) was maximally reduced at the beginning of repetitive stimulation and recovered during stimulation. Supernormality for interstimulus intervals between 50 and 150 ms (late supernormality) showed a delayed decrease and stayed significantly reduced after high-frequency stimulation. Training had no significant effect on any of the measured parameters, but we found that training induced changes in peak force correlated positively with baseline changes of early supernormality. Our results support the hypothesis that early supernormality represents membrane potential, which depolarizes in the beginning of high-frequency stimulation. Late supernormality probably reflects transverse tubular function and shows progressive changes during high-frequency stimulation with delayed normalization.NEW & NOTEWORTHY A conditioning impulse in human muscle fibers induces a prolonged phase of increased velocity (also called supernormality) with two phases related to an early and late afterpotential. We investigated the effects of intermittent 37-Hz stimulation on muscle fiber supernormality and found that the early and late phases of supernormality changed differently, and that the late phase may reflect the ionic interactions responsible for the counter-regulation of muscle fatigue.

Immunomodulatory treatment in postural tachycardia syndrome: A case series.

BACKGROUND AND PURPOSE: Postural tachycardia syndrome (POTS) is a form of autonomic dysfunction characterized by symptoms of orthostatic intolerance, often accompanied by sudomotor dysfunction and gastrointestinal dysmotility. Recently, evidence has accumulated that in a subset of patients, the pathogenesis of dysautonomia may be immune-mediated. The aim of the current report was to evaluate the use of intravenous immunoglobulin (IVIG) treatment in patients with progressive and/or refractory immune-mediated POTS. METHODS: We retroactively assessed the effect and tolerance of monthly administered IVIG in six patients using autonomic function testing, standardized symptom questionnaires, and patients' symptom diaries both before and 6 months into IVIG treatment. Objective outcome measures included heart rate increase after 10 min of head-up tilt as well as duration and anhidrotic area in a thermoregulatory sweat test. Subjective outcome measures were patient reports and symptom ratings from the symptom questionnaire. RESULTS: All patients responded to immunomodulatory treatment, regardless of disease duration. After 6 months of IVIG, symptom severity was reduced by nearly 40%. Autonomic function testing showed improved cardiovascular functioning by 50% and a reduction of anhidrotic areas by one third. Overall, tolerance of IVIG treatment was poor, but could be improved by a reduction in infusion rate, premedication with steroids, and additional intravenous hydration. CONCLUSIONS: Using subjective but also standardized objective measures, the case series describes promising effects of IVIG treatment in POTS patients with immune-mediated dysautonomia. By reducing the infusion rate, pretreatment with steroids, and intravenous hydration, tolerance could be improved, and no patient had to discontinue the treatment.

Leg pain in neuropathic postural tachycardia syndrome is associated with altered muscle membrane properties.

PURPOSE: In neuropathic postural tachycardia syndrome, peripheral sympathetic dysfunction leads to excessive venous blood pooling during orthostasis. Up to 84% of patients report leg pain and weakness in the upright position. To explore possible pathophysiological processes underlying these symptoms, the present study examined muscle excitability depending on body position in patients with neuropathic postural tachycardia syndrome and healthy subjects. METHODS: In ten patients with neuropathic postural tachycardia syndrome and ten healthy subjects, muscle excitability measurements were performed repeatedly: in the supine position, during 10 min of head-up tilt and during 6 min thereafter. Additionally, lower leg circumference was measured and subjective leg pain levels were assessed. RESULTS: In patients with neuropathic postural tachycardia syndrome, muscle excitability was increased in the supine position, decreased progressively during tilt, continued to decrease after being returned to the supine position, and did not completely recover to baseline values after 6 min of supine rest. The reduction in muscle excitability during tilt was paralleled by an increase in lower leg circumference as well as leg pain levels. No such changes were observed in healthy subjects. CONCLUSIONS: This study provides evidence for the occurrence of orthostatic changes in muscle excitability in patients with neuropathic postural tachycardia syndrome and that these may be associated with inadequate perfusion of the lower extremities. Insufficient perfusion as a consequence of blood stasis may cause misery perfusion of the muscles, which could explain the occurrence of orthostatic leg pain in neuropathic postural tachycardia syndrome.

Individualized Brain Tissue Oxygen-Monitoring Probe Placement Helps to Guide Therapy and Optimizes Outcome in Neurocritical Care.

BACKGROUND/OBJECTIVE: In order to monitor tissue oxygenation in patients with acute neurological disorders, probes for measurement of brain tissue oxygen tension (ptO2) are often placed non-specifically in a right frontal lobe location. To improve the value of ptO2 monitoring, placement of the probe into a specific area of interest is desirable. We present a technique using CT-guidance to place the ptO2 probe in a particular area of interest based on the individual patient's pathology. METHODS: In this retrospective cohort study, we analyzed imaging and clinical data from all patients who underwent CT-guided ptO2 probe placement at our institution between October 2017 and April 2019. Primary endpoint was successful placement of the probe in a particular area of interest rated by two independent reviewers. Secondary outcomes were complications from probe insertion, clinical consequences from ptO2 measurements, clinical outcome according to the modified Rankin Scale (mRS) as well as development of ischemia on follow-up imaging. A historical control group was selected from patients who underwent conventional ptO2 probe placement between January 2010 and October 2017. RESULTS: Eleven patients had 16 CT-guided probes inserted. In 15 (93.75%) probes, both raters agreed on the correct placement in the area of interest. Each probe triggered on average 0.48 diagnostic or therapeutic adjustments per day. Only one infarction within the vascular territory of a probe was found on follow-up imaging. Eight out of eleven patients (72.73%) reached a good outcome (mRS ≤ 3). In comparison, conventionally placed probes triggered less diagnostic and therapeutic adjustment per day (p = 0.007). Outcome was worse in the control group (p = 0.024). CONCLUSION: CT-guided probe insertion is a reliable and easy technique to place a ptO2 probe in a particular area of interest in patients with potentially reduced cerebral oxygen supply. By adjusting treatment aggressively according to this individualized monitoring data, clinical outcome may improve.

Standardized visual EEG features predict outcome in patients with acute consciousness impairment of various etiologies.

BACKGROUND: Early prognostication in patients with acute consciousness impairment is a challenging but essential task. Current prognostic guidelines vary with the underlying etiology. In particular, electroencephalography (EEG) is the most important paraclinical examination tool in patients with hypoxic ischemic encephalopathy (HIE), whereas it is not routinely used for outcome prediction in patients with traumatic brain injury (TBI). METHOD: Data from 364 critically ill patients with acute consciousness impairment (GCS ≤ 11 or FOUR ≤ 12) of various etiologies and without recent signs of seizures from a prospective randomized trial were retrospectively analyzed. Random forest classifiers were trained using 8 visual EEG features-first alone, then in combination with clinical features-to predict survival at 6 months or favorable functional outcome (defined as cerebral performance category 1-2). RESULTS: The area under the ROC curve was 0.812 for predicting survival and 0.790 for predicting favorable outcome using EEG features. Adding clinical features did not improve the overall performance of the classifier (for survival: AUC = 0.806, p = 0.926; for favorable outcome: AUC = 0.777, p = 0.844). Survival could be predicted in all etiology groups: the AUC was 0.958 for patients with HIE, 0.955 for patients with TBI and other neurosurgical diagnoses, 0.697 for patients with metabolic, inflammatory or infectious causes for consciousness impairment and 0.695 for patients with stroke. Training the classifier separately on subgroups of patients with a given etiology (and thus using less training data) leads to poorer classification performance. CONCLUSIONS: While prognostication was best for patients with HIE and TBI, our study demonstrates that similar EEG criteria can be used in patients with various causes of consciousness impairment, and that the size of the training set is more important than homogeneity of ACI etiology.

Sonography of the optic nerve sheath diameter before and after microsurgical closure of a dural CSF fistula in patients with spontaneous intracranial hypotension - a consecutive cohort study.

OBJECTIVE: Spontaneous intracranial hypotension is caused by spinal cerebrospinal fluid leakage. Patients with orthostatic headaches and cerebrospinal fluid leakage show a decrease in optic nerve sheath diameter upon movement from supine to upright position. We hypothesized that the decrease in optic nerve sheath diameter upon gravitational challenge would cease after closure of the leak. METHODS: We included 29 patients with spontaneous intracranial hypotension and refractory symptoms admitted from 2013 to 2016. The systematic workup included: Optic nerve sheath diameter sonography, spinal MRI and dynamic myelography with subsequent CT. Microsurgical sealing of the cerebrospinal fluid leak was the aim in all cases. RESULTS: Of 29 patients with a proven cerebrospinal fluid leak, one declined surgery. A single patient was lost to follow-up. In 27 cases, the cerebrospinal fluid leak was successfully sealed by microsurgery. The width of the optic nerve sheath diameter in supine position increased from 5.08 ± 0.66 mm before to 5.36 ± 0.53 mm after surgery ( p = 0.03). Comparing the response of the optic nerve sheath diameter to gravitational challenge, there was a significant change from before (-0.36 ± 0.32 mm) to after surgery (0.00 ± 0.19 mm, p < 0.01). In parallel, spontaneous intracranial hypotension-related symptoms resolved in 26, decreased in one and persisted in a single patient despite recovery of gait. CONCLUSIONS: The sonographic assessment of the optic nerve sheath diameter with gravitational challenge can distinguish open from closed spinal cerebrospinal fluid fistulas in spontaneous intracranial hypotension patients. A response to the gravitational challenge, that is, no more collapse of the optic nerve sheath while standing up, can be seen after successful treatment and correlates with the resolution of clinical symptoms. Sonography of the optic nerve sheath diameter may be utilized for non-invasive follow-up in spontaneous intracranial hypotension.

In vivo assessment of muscle membrane properties in the sodium channel myotonias.

INTRODUCTION: The gain-of-function mutations that underlie sodium channel myotonia (SCM) and paramyotonia congenital (PMC) produce differing clinical phenotypes. We used muscle velocity recovery cycles (MVRCs) to investigate membrane properties. METHODS: MVRCs and responses to trains of stimuli were compared in patients with SCM (n = 9), PMC (n = 8), and normal controls (n = 26). RESULTS: The muscle relative refractory period was reduced in SCM, consistent with faster recovery of the mutant sodium channels from inactivation. Both SCM and PMC showed an increased early supernormality and increased mean supernormality following multiple conditioning stimuli, consistent with slowed sodium channel inactivation. Trains of fast impulses caused a loss of amplitude in PMC, after which only half of the muscle fibers recovered, suggesting that the remainder stayed depolarized by persistent sodium currents. DISCUSSION: The differing effects of mutations on sodium channel function can be demonstrated in human subjects in vivo using this technique. Muscle Nerve 57: 586-594, 2018.

Muscle membrane properties in A pig sepsis model: Effect of norepinephrine.

INTRODUCTION: Sepsis-induced myopathy and critical illness myopathy are common causes of muscle weakness in intensive care patients. This study investigated the effect of different mean arterial blood pressure (MAP) levels on muscle membrane properties following experimental sepsis. METHODS: Sepsis was induced with fecal peritonitis in 12 of 18 anesthetized and mechanically ventilated pigs. Seven were treated with a high (75-85 mmHg) and 5 were treated with a low (≥60 mmHg) MAP target for resuscitation. In septic animals, resuscitation was started 12 h after peritonitis induction, and muscle velocity recovery cycles were recorded 30 h later. RESULTS: Muscles in the sepsis/high MAP group showed an increased relative refractory period and reduced early supernormality compared with the remaining septic animals and the control group, indicating membrane depolarization and/or sodium channel inactivation. The membrane abnormalities correlated positively with norepinephrine dose. DISCUSSION: Norepinephrine may contribute to sepsis-induced abnormalities in muscle by impairing microcirculation. Muscle Nerve 57: 808-813, 2018.

Management of spontaneous intracranial hypotension - Transorbital ultrasound as discriminator.

OBJECTIVE: Spontaneous intracranial hypotension (SIH) is most commonly caused by cerebrospinal fluid (CSF) leakage. Therefore, we hypothesised that patients with orthostatic headache (OH) would show decreased optic nerve sheath diameter (ONSD) during changes from supine to upright position. METHODS: Transorbital B-mode ultrasound was performed employing a high-frequency transducer for ONSD measurements in the supine and upright positions. Absolute values and changes of ONSD from supine to upright were assessed. Ultrasound was performed in 39 SIH patients, 18 with OH and 21 without OH, and in 39 age-matched control subjects. The control group comprised 20 patients admitted for back surgery without headache or any orthostatic symptoms, and 19 healthy controls. RESULTS: In supine position, mean ONSD (±SD) was similar in patients with (5.38±0.91 mm) or without OH (5.48±0.89 mm; p=0.921). However, in upright position, mean ONSD was different between patients with (4.84±0.99 mm) and without OH (5.53±0.99 mm; p=0.044). Furthermore, the change in ONSD from supine to upright position was significantly greater in SIH patients with OH (-0.53±0.34 mm) than in SIH patients without OH (0.05±0.41 mm; p≤0.001) or in control subjects (0.01±0.38 mm; p≤0.001; area under the curve: 0.874 in receiver operating characteristics analysis). CONCLUSIONS: Symptomatic patients with SIH showed a significant decrease of ONSD, as assessed by ultrasound, when changing from the supine to the upright position. Ultrasound assessment of the ONSD in two positions may be a novel, non-invasive tool for the diagnosis and follow-up of SIH and for elucidating the pathophysiology of SIH.

Force training induces changes in human muscle membrane properties.

INTRODUCTION: Human muscle membrane properties can be assessed in vivo by recording muscle velocity recovery cycles (MVRCs). This study was undertaken to study the effect of muscle force training on MVRC parameters. METHODS: MVRCs with 1 to 5 conditioning stimuli were recorded from brachioradialis muscle before and after 2 weeks of muscle force training in 12 healthy subjects. The effects of training on relative refractory period and early and late supernormality were quantified. RESULTS: Force training induced a reduction of relative refractory period (P < 0.0001), while early supernormality was increased (P < 0.02) and peaked earlier (P < 0.01). Late supernormality and the increases in late supernormality due to 2 and 5 conditioning stimuli remained unchanged. CONCLUSIONS: Muscle force training leads to hyperpolarization of the resting muscle membrane potential, probably caused by an increase in the number of sodium pump sites. Muscle Nerve 54: 144-146, 2016.

Muscle velocity recovery cycles: Comparison between surface and needle recordings.

INTRODUCTION: Recording of muscle velocity recovery cycles (MVRCs) has been developed as a technique to investigate the pathophysiology of muscle diseases. MVRCs have been measured by direct muscle stimulation and concentric electromyographic needle recording. This study was undertaken to determine whether recordings can be made with surface electrodes. METHODS: MVRCs with 1 and 2 conditioning stimuli were recorded simultaneously with concentric needle and surface electrodes from the brachioradialis muscle in 12 healthy volunteers. Muscle relative refractory period, early and late supernormality, and extra-late supernormality were compared between the recording techniques. RESULTS: Surface recordings were possible in all subjects. The multifiber action potentials recorded with surface electrodes were smaller than those recorded with needles, but there was no significant difference between any of their MVRC properties. CONCLUSIONS: MVRCs can be recorded with surface electrodes in healthy subjects. The use of surface electrodes may facilitate the technique of recording MVRCs.

In vivo assessment of muscle membrane properties in myotonic dystrophy.

INTRODUCTION: Myotonia in myotonic dystrophy types 1 (DM1) and 2 (DM2) is generally attributed to reduced chloride-channel conductance. We used muscle velocity recovery cycles (MVRCs) to investigate muscle membrane properties in DM1 and DM2, using comparisons with myotonia congenita (MC). METHODS: MVRCs and responses to repetitive stimulation were compared between patients with DM1 (n = 18), DM2 (n = 5), MC (n = 18), and normal controls (n = 20). RESULTS: Both DM1 and DM2 showed enhanced late supernormality after multiple conditioning stimuli, indicating delayed repolarization as in MC. Contrary to MC, however, DM1 showed reduced early supernormality after multiple conditioning stimuli, and weak DM1 patients also showed abnormally slow latency recovery after repetitive stimulation. CONCLUSIONS: These findings support the presence of impaired chloride conductance in both DM1 and DM2. The early supernormality changes indicate that sodium currents were reduced in DM1, whereas the weakness-associated slow recovery after repetitive stimulation may provide an indication of reduced Na(+) /K(+) -ATPase activation. Muscle Nerve 54: 249-257, 2016.

Esophageal versus surface recording of diaphragm compound muscle action potential.

INTRODUCTION: Repeated diaphragm compound muscle action potential (CMAP) recordings may help to understand the pathophysiology of respiratory muscle weakness. Neurally adjusted ventilator assist (NAVA) uses esophageal EMG electrodes to drive the ventilator. We evaluated the feasibility of CMAP recordings using these electrodes and established normal values. METHODS: Bilateral cervical phrenic nerve electrical stimulation was performed in 15 healthy volunteers. CMAP recordings with esophageal NAVA electrodes were compared with surface electrode recordings during inspiratory and expiratory pause. RESULTS: Compared with surface recordings, esophageal CMAP amplitudes were higher with increased latencies. Differences between the 2 techniques were most prominent in inspiration. For both recording techniques, amplitudes were higher, and latencies were longer during inspiration. Latencies were also longer when measured on the left side. CONCLUSIONS: Diaphragm CMAPs can be measured using the commercially available esophageal NAVA probe. This may facilitate repeated diaphragm CMAP studies in mechanically ventilated patients.

Chloride channels in myotonia congenita assessed by velocity recovery cycles.

INTRODUCTION: Myotonia congenita (MC) is caused by congenital defects in the muscle chloride channel CLC-1. This study used muscle velocity recovery cycles (MVRCs) to investigate how membrane function is affected. METHODS: MVRCs and responses to repetitive stimulation were compared between 18 patients with genetically confirmed MC (13 recessive, 7 dominant) and 30 age-matched, normal controls. RESULTS: MC patients exhibited increased early supernormality, but this was prevented by treatment with sodium channel blockers. After multiple conditioning stimuli, late supernormality was enhanced in all MC patients, indicating delayed repolarization. These abnormalities were similar between the MC subtypes, but recessive patients showed a greater drop in amplitude during repetitive stimulation. CONCLUSIONS: MVRCs indicate that chloride conductance only becomes important when muscle fibers are depolarized. The differential responses to repetitive stimulation suggest that, in dominant MC, the affected chloride channels are activated by strong depolarization, consistent with a positive shift of the CLC-1 activation curve.

Early changes of muscle membrane properties in porcine faecal peritonitis.

INTRODUCTION: Sepsis-induced myopathy and critical illness myopathy (CIM) are possible causes of muscle weakness in intensive care patients. They have been attributed to muscle membrane dysfunction. The aim of this study was to investigate membrane properties in the early stage of experimental sepsis by evaluating muscle excitability. METHODS: In total, 20 anesthetized and mechanically ventilated pigs were randomized to either faecal peritonitis (n = 10) or to non-septic controls (n = 10). Resuscitation with fluids and vasoactive drugs was started 3 hours after peritonitis induction. Muscle membrane properties were investigated by measuring muscle velocity recovery cycles before induction of peritonitis as well as 6, 18 and 27 hours thereafter. Muscle relative refractory period (MRRP) and early supernormality (ESN) were assessed. RESULTS: Peritonitis lasting 27 hours was associated with an increase of MRRP by 28% from 2.38 ± 0.18 ms (mean ± SD) to 3.47 ± 1.79 ms (P <0.01) and a decrease of ESN by 31% from 9.64 ± 2.82% to 6.50 ± 2.64% (P <0.01). ESN reduction was already apparent 6 hours after induction of peritonitis. Values in controls did not show any significant alterations. CONCLUSIONS: Muscle membrane abnormalities consistent with membrane depolarization and/or sodium channel inactivation occurred within 6 hours of peritonitis induction. This indicates that changes that have been described in established sepsis-induced myopathy and/or CIM start early in the course of sepsis. Muscle excitability testing facilitates evaluation of the time course of these changes.