Respiratory electrophysiological studies in Guillain-Barré syndrome

Emerging biomarkers to predict clinical outcomes in Guillain-Barré syndrome

INTRODUCTION

Guillain-Barré syndrome (GBS) is an immune-mediated poly(radiculo)neuropathy with a variable clinical outcome. Identifying patients who are at risk of suffering from long-term disabilities is a great challenge. Biomarkers are useful to confirm diagnosis, monitor disease progression, and predict outcome.

AREAS COVERED

The authors provide an overview of the diagnostic and prognostic biomarkers for GBS, which are useful for establishing early treatment strategies and follow-up care plans.

EXPERT OPINION

Detecting patients at risk of developing a severe outcome may improve management of disease progression and limit potential complications. Several clinical factors are associated with poor prognosis: higher age, presence of diarrhea within 4 weeks of symptom onset, rapid and severe weakness progression, dysautonomia, decreased vital capacity and facial, bulbar, and neck weakness. Biological, neurophysiological and imaging measures of unfavorable outcome include multiple anti-ganglioside antibodies elevation, increased serum and CSF neurofilaments light (NfL) and heavy chain, decreased NfL CSF/serum ratio, hypoalbuminemia, nerve conduction study with early signs of demyelination or axonal loss and enlargement of nerve cross-sectional area on ultrasound. Depicting prognostic biomarkers aims at predicting short-term mortality and need for cardio-pulmonary support, long-term patient functional outcome, guiding treatment decisions and monitoring therapeutic responses in future clinical trials.

Sensitivity and specificity of phrenic nerve electrophysiology to predict mechanical ventilation in the Guillain-Barré syndrome

INTRODUCTION/AIMS

In Guillain-Barré syndrome (GBS), the sensitivity and specificity of phrenic compound muscle action potential (CMAP) measurements to predict endotracheal mechanical ventilation are unknown. Hence, we sought to estimate sensitivity and specificity.

METHODS

We performed a 10-year retrospective analysis of adult GBS patients from our single-center laboratory database (2009 to 2019). The phrenic nerve amplitudes and latencies before ventilation were recorded along with other clinical and demographic features. Receiver operating curve (ROC) analysis with area under the curve (AUC) was used to determine the sensitivity and specificity with 95% confidence interval (CI) for phrenic amplitudes and latencies in predicting the need for mechanical ventilation.

RESULTS

Two hundred five phrenic nerves were analyzed in 105 patients. The mean age was 46.1 ± 16.2 years, with 60% of them being male. Fourteen patients (13.3%) required mechanical ventilation. The average phrenic amplitudes were lower in the ventilated group (P = .003), but average latencies did not differ (P = .133). ROC analysis confirmed that phrenic amplitudes could predict respiratory failure (AUC = 0.76; 95% CI, 0.61 to 0.91; P < .002), but phrenic latencies could not (AUC = 0.60; 95% CI, 0.46 to 0.73; P = .256). The best threshold for amplitude was ≥0.6 mV, with sensitivity, specificity, and positive and negative predictive values of 85.7%, 58.2%, 24.0%, and 96.4%, respectively.

DISCUSSION

Our study suggests that phrenic CMAP amplitudes can predict the need for mechanical ventilation in GBS. In contrast, phrenic CMAP latencies are not reliable. The high negative predictive value of phrenic CMAP amplitudes ≥0.6 mV can preclude mechanical ventilation, making these a useful adjunct to clinical decision-making.

Predictors of Mechanical Ventilation in Guillain-Barré Syndrome with Axonal Subtypes

BACKGROUND

The early clinical predictors of respiratory failure in Latin Americans with Guillain-Barré syndrome (GBS) have scarcely been studied. This is of particular importance since Latin America has a high frequency of axonal GBS variants that may imply a worse prognosis.

METHODS

We studied 86 Mexican patients with GBS admitted to the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, a referral center of Mexico City, to describe predictors of invasive mechanical ventilation (IMV).

RESULTS

The median age was 40 years (interquartile range: 26-53.5), with 60.5% men (male-to-female ratio: 1.53). Most patients (65%) had an infectious antecedent (40.6% gastrointestinal). At admission, 38% of patients had a Medical Research Council (MRC) sum score <30. Axonal subtypes predominated (60.5%), with acute motor axonal neuropathy being the most prevalent (34.9%), followed by acute inflammatory demyelinating polyneuropathy (32.6%), acute motor sensory axonal neuropathy (AMSAN) (25.6%), and Fisher syndrome (7%). Notably, 15.1% had onset in upper limbs, 75.6% dysautonomia, and 73.3% pain. In all, 86% received either IVIg (9.3%) or plasma exchange (74.4%). IMV was required in 39.5% patients (72.7% in AMSAN). A multivariate model without including published prognostic scores yielded the time since onset to admission <15 days, axonal variants, MRC sum score <30, and bulbar weakness as independent predictors of IMV. The model including grading scales yielded lower limbs onset, Erasmus GBS respiratory insufficiency score (EGRIS) >4, and dysautonomia as predictors.

CONCLUSION

These results suggest that EGRIS is a good prognosticator of IMV in GBS patients with a predominance of axonal electrophysiological subtypes, but other early clinical data should also be considered.

Utility of phrenic nerve conduction studies for identification of patients with neuromuscular diseases requiring invasive mechanical ventilation

INTRODUCTION/AIMS

Predicting when a patient will require invasive mechanical ventilation (IMV) is a major challenge in routine care for some neuromuscular diseases. In this study, we prospectively investigated whether phrenic nerve conduction studies (PNCS) can predict when IMV will be required in patients with amyotrophic lateral sclerosis (ALS), Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), and myotonic dystrophy (DM).

METHODS

PNCS amplitude (avAMP) and latency (avLAT) were compared between patients who required IMV (IMV group) and those who did not (non-IMV group). PNCS were performed in 62 healthy controls and in patients with four different diseases that may require IMV: ALS (n = 56), GBS (n = 72), CIDP (n = 38), and DM (n = 24).

RESULTS

The IMV group consisted of 12 patients with ALS, 14 with GBS, 2 with CIDP, and 4 with DM. avAMP was significantly lower in the IMV group with ALS than in the non-IMV group (P < .05), but no significant difference was observed in avLAT. avAMP was significantly lower and avLAT was significantly longer in the IMV group with GBS than in the non-IMV group (both P < .05). Receiver operating characteristic analysis showed that the avAMP cutoff between the IMV and non-IMV groups was 184.3 μV (area under the curve = 0.921; sensitivity, 84.6%; specificity, 88.2%) for ALS and GBS.

DISCUSSION

PNCSs may aid in determining whether a patient with ALS or GBS requires IMV.

Clinical predictors for mechanical ventilation and prognosis in patients with Guillian-Barre syndrome: a 10-year experience

INTRODUCTION

Guillain-Barré syndrome (GBS) is a common cause of flaccid paralysis. Up to a third of cases result in respiratory failure requiring mechanical ventilation.

AIM

We aim to study the possible predictors of respiratory compromise requiring mechanical ventilation in cases of GBS as well as their clinical outcome in the UAE population.

METHODOLOGY

A retrospective observational study was conducted between the periods of January 2009 till January 2019 in a tertiary center in Dubai. Cases were grouped according to their need for mechanical ventilation then compared for possible predicting factors. Up to 1-year follow-up was done to assess the clinical outcome.

RESULTS

Out of the 82 cases that were included in the study, 64 (78%) were males with a mean age at presentation being 37 ± 14.4. Most of the cases presented with disability score of 4 (n= 33, 40.2%), being bed bound or wheelchair bound. Twenty cases (24.4%) required mechanical ventilation at presentation. Axonal type of nerve injury was present in 11 (55%) patients requiring intubation, in contrast to 17 (27.4%) patients not requiring intubation. Cases that required mechanical ventilation were older (P .028). They also had a reduced rate of recovery after 1 month (P .004), and more residual deficit at 6 months (P .003) and 12 months (P <.001). This also translated in a longer duration of hospital stay (<.001).

CONCLUSION

Older age at presentation is a major predictor for the need of mechanical ventilation in GBS. This need for mechanical ventilation is associated with longer hospital stay as well as reduced rate of recovery up to 1 year after the onset of presentation.

Reliability of diaphragmatic motor-evoked potentials induced by transcranial magnetic stimulation

The diaphragmatic motor-evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) permits electrophysiological assessment of the cortico-diaphragmatic pathway. Despite the value of TMS for investigating diaphragm motor integrity in health and disease, reliability of the technique has not been established. The study aim was to determine within- and between-session reproducibility of surface electromyogram recordings of TMS-evoked diaphragm potentials. Fifteen healthy young adults participated (6 females, age = 29 ± 7 yr). Diaphragm activation was determined by gradually increasing the stimulus intensity from 60 to 100% of maximal stimulator output (MSO). A minimum of seven stimulations were performed at each intensity. A second block of stimuli was delivered 30 min later for within-day comparisons, and a third block was performed on a separate day for between-day comparisons. Reliability of diaphragm MEPs was assessed at 100% MSO using intraclass correlation coefficients (ICC) and 95% limits of agreement (LOA). MEP latency (ICC = 0.984, P < 0.001), duration (ICC = 0.958, P < 0.001), amplitude (ICC = 0.950, P < 0.001), and area (ICC = 0.956, P < 0.001) were highly reproducible within-day. Between-day reproducibility was good to excellent for all MEP characteristics (latency ICC = 0.953, P < 0.001; duration ICC = 0.879, P = 0.002; amplitude ICC = 0.789, P = 0.019; area ICC = 0.815, P = 0.012). Data revealed less precision between-day versus within-day, as evidenced by wider LOA for all MEP characteristics. Large within- and between-subject variability in MEP amplitude and area was observed. In conclusion, TMS is a reliable means of inducing diaphragm potentials in most healthy individuals.NEW & NOTEWORTHY Transcranial magnetic stimulation (TMS) is a noninvasive technique to assess neural impulse conduction along the cortico-diaphragmatic pathway. The reliability of diaphragm motor-evoked potentials (MEP) induced by TMS is unknown. Notwithstanding large variability in MEP amplitude, we found good-to-excellent reproducibility of all MEP characteristics (latency, duration, amplitude, and area) both within- and between-day in healthy adult men and women. Our findings support the use of TMS and surface EMG to assess diaphragm activation in humans.

Predictors of respiratory failure in patients with Guillain-Barré syndrome: a systematic review and meta-analysis

OBJECTIVE

To systematically review the literature regarding the ability of clinical features to predict respiratory failure in patients with Guillain-Barré syndrome (GBS).

DATA SOURCES

We searched the PubMed and Ovid MEDLINE databases with the search terms "guillain barre syndrome" OR "acute inflammatory demyelinating polyneuropathy" OR "acute motor axonal neuropathy" OR "acute motor sensory axonal neuropathy" AND "respiratory failure" OR "mechanical ventilation". We excluded articles that did not report the results of original research (eg, review articles, letters), were case reports or series (ten or fewer patients), were not available in English, reported research in paediatric populations (16 years of age or younger), or were interventional studies. Article quality was assessed with the Newcastle-Ottawa quality assessment scale.

DATA SYNTHESIS

Thirty-four relevant studies were identified. Short time from symptom onset to hospital admission (less than 7 days), bulbar (odds ratio [OR], 9.0; 95% CI, 3.94-20.6; P < 0.001) or neck weakness (OR, 6.36; 95% CI, 2.32-17.5; P < 0.001), and severe muscle weakness at hospital admission were associated with increased risk of intubation. Facial weakness (OR, 3.74; 95% CI, 2.05-6.81; P < 0.001) and autonomic instability (OR, 6.40; 95% CI, 2.83-14.5; P < 0.001) were significantly more frequent in patients requiring intubation in our meta-analyses; however, the differences were not statistically significant in individual multivariable analysis studies. Four predictive models have been developed to assess the risk of respiratory failure for patients with GBS, each with good to excellent discriminative power (area under the receiver operating characteristic curve, 0.79-0.96).

CONCLUSIONS AND RELEVANCE

Early identification of GBS patients at risk of respiratory failure could reduce the rates of adverse outcomes associated with delayed intubation. Algorithms that predict a patient's risk of subsequent respiratory failure at hospital admission appear more reliable than individual clinical variables.

Phrenic Nerve Conduction Study in the Early Stage of Guillain-Barre Syndrome as a Predictor of Respiratory Failure

BACKGROUND

Guillain-Barré syndrome (GBS) has unpredictable clinical course with severe complication of respiratory failure.

OBJECTIVE

To identify clinical profiles and electrophysiological study particularly non-invasive Phrenic nerve conduction study in patients of early GBS to predict respiratory failure.

METHODS

64 adult (age≥18yrs) patients of early GBS (onset ≤ 14 days) during the study period from January 2014 to October 2015 were evaluated by clinical profiles of age, gender, antecedent infection, time to peak disability, single breath counts, cranial nerve involvement, autonomic dysfunction and non-invasive Phrenic nerve conduction study. Patients with predisposition factors of polyneuropathy like diabetes mellitus, hypothyroidism, vitamin deficiency, renal failure were excluded.

RESULTS

Among 64 patients abnormal phrenic nerve conduction study was seen in 65.62% cases (42/64) and 45.23% (19/42) of them developed respiratory failure. Phrenic nerve sum latency, amplitude, duration and area were abnormal in those who developed respiratory failure and they had sum of phrenic nerve latency >28 msec, sum of CMAP amplitude <300 μV, sum of CMAP duration >50 msec and sum of area < 4 mVmS. None with normal phrenic nerve study developed respiratory failure. It was found that age, gender, preceding infection, autonomic involvement and types of GB syndrome had no influence on development of respiratory failure (p>0.05). Rapid disease progression to peak disability, more severe disease, shorter single breath counts and cranial nerve involvement were seen more often in patients with respiratory failure.

CONCLUSION

Abnormal Phrenic nerve conduction study in the early Guillain-Barré syndrome might be of great value independently in predicting impending respiratory failure.

Reliability of the diaphragmatic compound muscle action potential evoked by cervical magnetic stimulation and recorded via chest wall surface EMG

INTRODUCTION

Stimulation of the phrenic nerve via cervical magnetic stimulation (CMS) elicits a compound muscle action potential (CMAP) that allows for assessment of diaphragm activation. The reliability of CMS to evoke the CMAP recorded by chest wall surface EMG has yet to be comprehensively examined.

METHODS

CMS was performed on healthy young males (n=10) and females (n=10). Surface EMG electrodes were placed on the right and left hemi-diaphragm between the 6-8th intercostal spaces. CMAPs were analysed for: latency, duration, peak-to-peak amplitude, and area. Reliability within and between experimental sessions was assessed using intraclass correlation coefficients (ICC). Bilateral (right-left) and sex-based (male-female) comparisons were also made (independent samples t-test).

RESULTS

All CMAP characteristics demonstrated high reproducibility within (ICCs>0.96) and between (ICCs>0.89) experimental sessions. No statistically significant bilateral or sex-based differences were found (p>0.05).

DISCUSSION

CMS is a reliable and non-invasive method to evaluate phrenic nerve conduction.

Respiratory Muscle Assessment in Acute Guillain-Barré Syndrome

PURPOSE

Guillain-Barré Syndrome (GBS) is a life-threatening disease due to respiratory muscle involvement. This study aimed at objectively assessing the course of respiratory muscle function in GBS subjects within the first week of admission to an intensive care unit.

METHODS

Medical Research Council Sum Score (MRC-SS), vigorimetry, spirometry, and respiratory muscle function tests (inspiratory/expiratory muscle strength: PImax/PEmax, sniff nasal pressure: SnPna) were assessed twice daily. GBS Disability Score (GBS-DS) was assessed once daily. On days one (d1) and seven (d7), blood gases and twitch mouth pressure during magnetic phrenic nerve stimulation (Pmo,tw) were additionally evaluated.

RESULTS

Nine subjects were included. MRC-SS, vigorimetry, PImax, and SnPna increased between d1 and d7. GBS-DS, spirometry and Pmo,tw remained unaltered. Only SnPna correlated closely with the MRC-SS on both d1 (r = 0.77, p = 0.02) and d7 (r = 0.74, p = 0.02).

CONCLUSION

SnPna was the only parameter that correlated with MRC-SS, while the current gold standard of spirometry measurement did not.

Sleep and breathing disorders in myotonic dystrophy type 2

OBJECTIVES

In patients who exhibit myotonic dystrophy type 1 (DM1), sleep disorders and breathing impairments are common; however, in those with DM type 2 (DM2), limited studies on polysomnography (PSG) and none on phrenic compound motor action potential (CMAP) have been performed, which is the aim of this study.

MATERIALS AND METHODS

Sixteen patients with DM2 were questioned about respiratory symptoms. They underwent PSG with morning arterial gas analyses (AGA). Respiratory functions and phrenic CMAPs were studied. The data were compared to those of 16 healthy controls and 25 patients with DM1.

RESULTS

Daytime tiredness is the most common symptom, but orthopnea was reported in 13% of patients with DM2. A detailed sleep architecture analysis revealed a significantly greater proportion of time in stage 3 and REM sleep, and a shorter time in stage 2 in the DM2 than in controls. Lower respiratory volumes and pressures, abnormalities in AGA, night oxygen desaturation and higher EtCO2 are present in DM2, but are less pronounced than in the DM1 population. Small CMAP amplitudes were presented in 12% of patients with DM2, correlating with smaller respiratory functions and poorer sleep quality. AHI was abnormal in 38% of DM2, mainly due to obstructive apneas. PSG did not reveal hypoventilation.

CONCLUSIONS

Diaphragm weakness and sleep apneas might be present in patients with DM2; therefore, we suggest regular questioning about symptoms of respiratory insufficiency and monitoring of phrenic CMAP. PSG should be recorded, when patients have suggestive symptoms, abnormalities in AGA or higher BMI.

Simple bedside predictors of mechanical ventilation in patients with Guillain-Barre syndrome

OBJECTIVE

The objective of the study is to develop and validate a predictor score for assessing the requirement of mechanical ventilation (MV) in patients with Guillain-Barre syndrome (GBS).

STUDY DESIGN

The study was conducted in patients admitted with GBS in neurointensive care unit in a tertiary care hospital. The demographic, clinical factors, electrophysiological, and spirometric data of all consecutive patients were prospectively collected. The study was undertaken in 2 stages. In the first stage, data were collected for development of a predictor score. In the second stage, the score developed was validated on a separate set of patient data.

RESULTS

The data collected were compared between the 2 groups (ventilated vs nonventilated). On univariate analysis, time taken to reach maximum deficit, neck weakness, bulbar weakness, facial weakness, single breath count (SBC), forced vital capacity, and phrenic nerve latency predicted the need for MV. On multivariate analysis, only neck weakness, bulbar weakness, SBC, and forced vital capacity were independent predictors of MV. There was a good correlation between SBC and the spirometric tests and phrenic nerve distal motor latency, as reflected in receiver operating characteristics curve. The predictor score developed using the regression coefficient of independent predictors showed that the best cutoff score for prediction of ventilation was 60 (sensitivity, 0.95; 1--specificity, 0.065). Internal cross validation of the neck weakness, SBC, and bulbar palsy (NSB) score showed good correlation (Pearson R = 0.76; P = .00). There was no statistically significant difference between predicted and observed outcomes (sensitivity, 95%; specificity, 93%).

CONCLUSION

Several independent risk factors were found to predict the requirement for MV in patients with GBS at admission. However, after scoring and analyzing them, it was found that combining a few of them was more useful to predict the need for MV. A model using NSB score, developed using clinical variables, accurately predicted the requirement of MV. In addition, among the NSB score parameters, simple bedside SBC could adequately assess the adequacy of vital capacity.

Respiratory muscle weakness in peripheral neuropathies

Common peripheral neuropathies do not usually cause diaphragmatic weakness and subsequent respiratory compromise. However, respiratory involvement is relatively common in Guillain-Barré syndrome (GBS). Experience in GBS has led to a standardized approach to manage respiratory problems in peripheral neuropathies. Diaphragmatic weakness is not common in chronic inflammatory demyelinating polyneuropathy and extremely rare in multifocal motor neuropathy. The linkage has been described between certain subtypes of Charcot-Marie-Tooth (CMT) disease such as CMT2C and CMT4B1 and diaphragmatic weakness. A correlation usually has not been found between electrophysiologic findings and clinical respiratory signs or spirometric abnormalities in peripheral neuropathies except in amplitudes of evoked phrenic nerve responses. Careful and frequent assessment of respiratory function by a qualified team of healthcare professionals and physicians is essential. Criteria established for mechanical ventilation in GBS cases may be applied to other peripheral neuropathies with respiratory compromise as necessary.

Management of critical illness polyneuropathy and myopathy

A syndrome of generalized weakness, areflexia, and difficulty with weaning from a ventilator is a common clinical presentation in the critically ill patient, especially in the setting of sepsis, multiorgan failure, and hyperglycemia. At first believed to be a manifestation of nerve (critical illness neuropathy, CIN) or muscle (critical illness myopathy, CIM) dysfunction, our current conceptualization is as a spectrum (critical illness neuromuscular abnormalities, CINMA) that varies in extent and site(s) of involvement, but often a similar clinical presentation. Signs and symptoms of CINMA must be identified early to foster recovery and limit morbidity and mortality. The medical history is crucial in excluding preexisting neuromuscular conditions and electrodiagnostic testing helps to establish the diagnosis and prognostication. A stepwise approach to the management of a patient with CINMA is outlined, but avoiding potential medications, and ensuring supportive care are the primary interventions to consider. Recently intensive insulin therapy for hyperglycemia has been shown to lower the risk of CINMA and decrease the time of ventilatory support, but with a greater risk of hypoglycemia. Future therapeutic interventions will require a better understanding of disease pathogenesis, but may target proinflammatory cytokine and free-radical pathways, muscle gene expression, ion channel function, or proteolytic muscle protein mechanisms. Rehabilitation is an equally essential component in a patient's management. Although prognosis depends on the extent of the underlying muscle and nerve damage, mild persistent deficits are common and severe disability may be persistent.

Conduction velocity of the human phrenic nerve in the neck

PURPOSE

To measure phrenic nerve conduction velocity in the neck in humans.

SCOPE

We studied 15 healthy subjects (9 men, 32.4+/-6.7). We performed bipolar electrical phrenic stimulation in the neck, from a distal and a proximal stimulation site, and recorded diaphragm electromyographic responses on the surface of the chest. The ratio of the between-site distance to the latency difference provided phrenic velocities. Ulnar motor velocity was assessed similarly. In addition, five homogeneous patients with Charcot-Marie-Tooth disease type 1A (CMT1A) were studied for validation purposes. We obtained diaphragmatic responses from the two stimulation sites in all cases. The distal latencies (anterior axillary line recording) were 6.51+/-0.63ms (right) and 6.13+/-0.64ms (left). The minimal between site distance was 39mm. Phrenic motor velocity was 55.2+/-6.3ms(-1) (right) and 56.3+/-7.2ms(-1) (left). In CMT1A, phrenic velocities were 17.1+/-8.1ms(-1) (from 7 to 32ms(-1)) and were similar to ulnar and median velocities.

CONCLUSIONS

Phrenic nerve velocities can be estimated in humans and compare with upper limb motor conduction velocities. This should refine the investigation of phrenic function in peripheral neuropathies.

Phrenic nerve stimulation

Weakness of the limbs and respiratory muscles has increasingly been found to be a frequent event that complicates the medical history of patients in Intensive Care. The problem normally affects more serious cases and presents as muscular weakness leading to flaccid paralysis and difficulty in weaning patients off mechanical ventilation. This latter sign leads the intensivist to suspect possible involvement of the neuromuscular respiratory system. Unfortunately, in-depth clinical assessment of the neuromuscular respiratory system is difficult with critically ill patients, and electrophysiological studies have been used instead to overcome this problem. Of these latter, electric and electromagnetic stimulation of the phrenic nerve have been successful (along with needle electromyography of the diaphragm) in identifying the causes of neuromuscular respiratory insufficiency, especially in Intensive Care. In this brief chapter, we will be discussing the technique of electric stimulation of the phrenic nerve and neuromuscular respiratory insufficiency within the field of critical illness polyneuropathy.

Brachial neuritis with bilateral diaphragmatic paralysis following herpes zoster: a case report

We present a case of supine respiratory failure due to a bilateral diaphragmatic paralysis associated with brachial neuritis secondary to thoracic herpes zoster. Fluoroscopy in both the standing and supine positions revealed bilateral diaphragmatic paralysis accentuated in the supine position. To our knowledge, this is the first case of thoracic herpes zoster associated with brachial neuritis and bilateral diaphragmatic paralysis.

Phrenic nerve conduction in the early stage of Guillain-Barre syndrome might predict the respiratory failure

OBJECTIVE

To investigate whether phrenic nerve conduction in the early phase of Guillain- Barre syndrome (GBS) predicts the need for respiratory assistance during the subsequent clinical course.

MATERIAL AND METHODS

We performed electrophysiological examinations of conventional peripheral nerve conduction and phrenic nerve conduction for GBS patients within 14 days from the onset. We excluded patients who had already been treated with immuno-related therapy and respiratory assistance.

RESULTS

Fifteen patients were enrolled. Three patients with the sum of phrenic nerve latency longer than 30 ms and the sum of bilateral diaphragmatic compound muscle action potential amplitude smaller than 0.3 mV required respiratory assistance after the conduction test.

CONCLUSION

Our findings showed that not only delayed distal latency but also decreased amplitude may predict the need for respiratory assistance during the subsequent disease course.

Clinical and electrophysiological predictors of respiratory failure in Guillain-Barré syndrome: a prospective study

BACKGROUND

Respiratory failure is the most serious short-term complication of Guillain-Barré syndrome and can require invasive mechanical ventilation in 20-30% of patients. We sought to identify clinical and electrophysiological predictors of respiratory failure in the disease.

METHODS

We prospectively assessed electrophysiological data and clinical factors, including identified predictors of delay between disease onset and admission, inability to lift head, and vital capacity, in patients admitted with Guillain-Barré syndrome. We related these factors to subsequent need for ventilatory support. Neurophysiological findings were classified as demyelinating, axonal, equivocal, unexcitable, or normal. Predictive values of clinical and electrophysiological data were tested using classification trees to build up a predictive model. This model was initially built up in a two-third (fitting set) then validated in a one-third (validation set) of the total sample. The fitting and validation sets were randomly selected. We also assessed the predictive value of this model for disability at 6 months.

FINDINGS

From 1998, to 2006, 154 patients with Guillain-Barré syndrome were included in the study and 34 (22%) were subsequently ventilated. Demyelinating Guillain-Barré syndrome was more common in patients who went on to be ventilated than in those who were not (85%vs 51%, p=0.0003). Vital capacity and the proximal/distal compound muscular amplitude potential (p/dCMAP) ratio of the common peroneal nerve were retained in the tree model, with a probability of needing ventilation of less than 2.5% in patients with a ratio of greater than 55.6% and a vital capacity more than 81% of predicted. A p/dCMAP ratio of the peroneal nerve less than 55.6% and age older than 40 years were retained as independent predictors of disability at 6 months.

INTERPRETATION

Neurophysiological testing is helpful for assessing risk of respiratory failure, which is highest in patients with evidence of demyelination and very low in those without both 55.6% conduction block of the common peroneal nerve and a 20% reduction in vital capacity.

The cortico-diaphragmatic pathway involvement in amyotrophic lateral sclerosis: neurophysiological, respiratory and clinical considerations

Cortico-diaphragmatic pathway was investigated by means of transcranial magnetic stimulation (TMS), in 14 patients affected by definite amyotrophic lateral sclerosis (ALS) without clinical signs of respiratory impairment. Spirometry, gas analysis, and measurement of static inspiratory and expiratory pressures were performed in all patients. Forced vital capacity, forced expiratory volume at the first and second peak expiratory flow, sniff effort from FRC level (SNIP), maximal inspiratory and expiratory pressure at mouth (MIP/MEP), maximal transdiaphragmatic pressure (Pdimx) were considered. TMS was performed, recording by surface electrodes from hemidiaphragm, bilaterally. Latency of cortical and spinal motor-evoked potentials (Cx-MEP/Sp-MEP) and central motor conduction time (CMCT) were measured. None of the patients showed altered spirometry and gas levels. Seven patients showed decreased Pdimx and eight of MEP values. Four patients showed a delayed Sp-MEP. In one patient the Cx-MEP was abolished while the mean values of both Cx-MEP and CMCT were significantly increased (19.2+/-4.1 ms, P<0.0001; 10.8+/-4.8 ms, P<0.0001). Cx-MEP and CMCT did not show significant correlations with any of the respiratory measures. The patients with prolonged Sp-MEP, showed longer disease duration, lower Norris score, lower Pdimx and MEP values. In conclusion, cortico-diaphragmatic study is a sensitive measure to reveal subclinical diaphragmatic impairment although not correlated to respiratory measures.

An Unusual Cause of Dyspnea in a Patient with Relapsing Breast Cancer

Bilateral diaphragmatic paralysis (BDP) is usually caused by anatomic lesions of both phrenic nerves or generalized neurologic diseases. BDP has also been observed during and after infections, associated with mediastinal tumors, or may have an idiopathic etiology. A 57-year-old woman with breast cancer had progressive dyspnea that worsened when in the supine position. Lung function tests and phrenic nerve stimulation revealed bilateral diaphragmatic paralysis. Clinical suspicion of BDP should always be raised in patients suffering from progressive dyspnea and orthopnea. Determination of (VC) when standing and in the supine position and measurement of trandiaphragmatic pressure should reveal this uncommon diagnosis.

Neuromuscular manifestations of critical illness

Critical illness, more precisely defined as the systemic inflammatory response syndrome (SIRS), occurs in 20%-50% of patients who have been on mechanical ventilation for more than 1 week in an intensive care unit. Critical illness polyneuropathy (CIP) and myopathy (CIM), singly or in combination, occur commonly in these patients and present as limb weakness and difficulty in weaning from the ventilator. Critical illness myopathy can be subdivided into thick-filament (myosin) loss, cachectic myopathy, acute rhabdomyolysis, and acute necrotizing myopathy of intensive care. SIRS is the predominant underlying factor in CIP and is likely a factor in CIM even though the effects of neuromuscular blocking agents and steroids predominate in CIM. Identification and characterization of the polyneuropathy and myopathy depend upon neurological examination, electrophysiological studies, measurement of serum creatine kinase, and, if features suggest a myopathy, muscle biopsy. The information is valuable in deciding treatment and prognosis.

A prospective evaluation of phrenic nerve conduction in multifocal motor neuropathy and chronic inflammatory demyelinating polyneuropathy

The purpose of the study was to evaluate electrophysiologically phrenic nerve involvement in multifocal motor neuropathy (MMN) and chronic inflammatory demyelinating polyneuropathy (CIDP). The response latencies following phrenic nerve stimulation were increased in 11 of 14 (80%) patients in the CIDP group but in only 1 of 14 (8%) patients in the MMN group. The mean diaphragmatic compound muscle action potential (CMAP) was significantly lower in amplitude in the CIDP group compared to the MMN group and to a control group of 8 subjects (P < 0.001). There were no significant differences between the MMN and control groups. Only the reduction in CMAP amplitude correlated with the presence of restrictive lung function. Phrenic nerve conduction measurement should be performed more systematically, especially in CIDP and, when diaphragmatic CMAPs are reduced in amplitude, pulmonary function tests should be performed to look for a restrictive lung syndrome.

Disorders of the respiratory muscles

The act of breathing depends on coordinated activity of the respiratory muscles to generate subatmospheric pressure. This action is compromised by disease states affecting anatomical sites ranging from the cerebral cortex to the alveolar sac. Weakness of the respiratory muscles can dominate the clinical manifestations in the later stages of several primary neurologic and neuromuscular disorders in a manner unique to each disease state. Structural abnormalities of the thoracic cage, such as scoliosis or flail chest, interfere with the action of the respiratory muscles-again in a manner unique to each disease state. The hyperinflation that accompanies diseases of the airways interferes with the ability of the respiratory muscles to generate subatmospheric pressure and it increases the load on the respiratory muscles. Impaired respiratory muscle function is the most severe consequence of several newly described syndromes affecting critically ill patients. Research on the respiratory muscles embraces techniques of molecular biology, integrative physiology, and controlled clinical trials. A detailed understanding of disease states affecting the respiratory muscles is necessary for every physician who practices pulmonary medicine or critical care medicine.

Electrophysiology to predict mechanical ventilation in Guillain-Barré syndrome

To determine whether electrophysiological features predict endotracheal mechanical ventilation (ETMV) in Guillain-Barré syndrome (GBS). Non-ventilated GBS patients admitted to an ICU underwent standard electrophysiological testing. Endotracheal mechanical ventilation was decided by physicians who were unaware of electrophysiological results. Sixty consecutive patients underwent electrophysiological testing within 17 days of GBS onset; based on Hadden's criteria, 37 (62%) had primary demyelinating, 18 (30%) equivocal and five (8%) axonal disease. Time at electrophysiological testing and proportions of patients treated by plasma exchange and intravenous immunoglobulins were similar in the three groups, whereas primary demyelinating patients had worse results for disability grade and arm grade. The ETMV was required within 20 days of electrophysiological testing in 20 patients, 17 (46%) in the primary demyelinating group, three (17%) in equivocal group and none in the axonal group (P = 0.02). This prospective study suggests that electrophysiological demyelination may predict a need for ETMV in GBS.

Early predictors of mechanical ventilation in Guillain-Barré syndrome

OBJECTIVE

Although mechanical ventilation is required in 30% of patients with Guillain-Barré syndrome, early predictors of this treatment remain unknown.

DESIGN

Analysis of two cohorts of patients enrolled in two multicenter randomized clinical trials.

SETTING

French intensive care and neurologic units.

MEASUREMENTS

Demographic, neurologic, and biologic data; vital capacity; and time of onset, admission, and endotracheal mechanical ventilation were collected.

RESULTS

Amid 722 consecutive adults not ventilated at admission, endotracheal mechanical ventilation was required in 313 (43%) patients. Multivariate analyses identified six predictors of endotracheal mechanical ventilation: time from onset to admission of <7 days (odds ratio, 2.51), inability to cough (odds ratio, 9.09), inability to stand (odds ratio, 2.53), inability to lift the elbows (odds ratio, 2.99) or head (odds ratio, 4.34), and liver enzyme increases (odds ratio, 2.09). In the 196 (27%) patients whose vital capacity was measured, time from onset to admission of <7 days (odds ratio, 5.00), inability to lift the head (odds ratio, 5.00), and vital capacity <60% (odds ratio, 2.86) predicted endotracheal mechanical ventilation.

CONCLUSIONS

Patients with at least one of these predictors should be monitored in an intensive care unit. Mechanical ventilation was required in >85% of patients with at least four predictors from the first multivariate model and in 85% of patients with all three predictors from the second multivariate model. In these patients at high risk of respiratory failure, the value of early mechanical ventilation may deserve investigation.

Idiopathic bilateral diaphragmatic paralysis

A 41-year-old man complained of subacute onset of dyspnea and pain in the neck and chest. He was diagnosed with bilateral diaphragmatic paralysis, based on clinical inspection of the breathing pattern and transdiaphragmatic pressure recording, and was trained to use a portable bi-level positive airway pressure apparatus (BiPAP). Needle electromyography showed profuse fibrillation potentials and positive waves in the diaphragm, more abundant on the right than left side, and no response to phrenic nerve stimulation. Other muscles were not involved. Follow-up examinations, performed at 9 and 12 months after onset of paralysis, demonstrated a slow but progressive improvement of the patient's respiratory function, together with the appearance of reinnervation potentials in the diaphragm, and polyphasic, long-latency responses to phrenic nerve stimulation. The subacute onset of the paralysis associated with local pain, and its subsequent recovery, suggest bilateral proximal lesions in the phrenic nerves. In the absence of traumatic or metabolic causes, these findings suggest that the phrenic nerve can be a target in idiopathic neuritis.

Unilateral cranial and phrenic nerve involvement in axonal Guillain-Barré syndrome

A 49-year-old woman developed acute left facial, hypoglossal, and phrenic nerve palsies, as well as dysphagia and weakness in the neck and arms. Electrophysiologic studies showed an acute motor axonal neuropathy. Serum anti-GM1 IgG antibody was positive. Intravenous immunoglobulin treatment resulted in good clinical recovery. The present report indicates that the cranial and phrenic nerves may be affected unilaterally in Guillain-Barré syndrome, and that there is clinical variability in the axonal subtype of this syndrome.

Phrenic nerve conduction study in demyelinating neuropathies and open-heart surgery

OBJECTIVES

The aim of this study was to determine normal values of phrenic nerve conduction (PNC) in healthy individuals; to evaluate the subclinical extent of phrenic nerve involvement in Guillain-Barré syndrome (G-B) and hereditary motor and sensory neuropathy-I (HMSN-I), and to evaluate phrenic nerve damage after cardiac surgery.

MATERIALS AND METHODS

PNC was performed by transcutaneous stimulation in the neck and recording the diaphragmatic potential from surface electrodes placed at the seventh and eight intercostal spaces. PNC was performed bilaterally in 25 healthy volunteers and 25 patients before and after open-heart surgery. Right PNC was also performed in 5 cases with G-B and 5 patients with HMNS-I.

RESULTS

Latency and amplitude of the diaphragmatic potential were the same in controls and in patients with cardiac disease before surgery. After surgery, 28% of patients had left phrenic nerve inexcitability, and 8% had reduced amplitude of the response. These 9 patients demonstrated elevation of the left hemidiaphragm on chest radiography. Left PNC performed 1 year after the operation showed improvement in latency and amplitude of the responses in all except one patient. PNC was prolonged in 4 out of 5 cases with G-B and in all patients with HMNS-I.

CONCLUSIONS

PNC is an easy and reliable method in evaluating phrenic nerve damage due to hypothermia or primary stretch injury in patients after cardiac surgery. PNC may be helpful in detecting diaphragmatic involvement before clinical ventilatory insufficiency in demyelinating neuropathies such as G-B and HMNS-I.

Post-intubation pulmonary function test in Guillain-Barré syndrome

The value of daily postintubation respiratory function tests in predicting duration of ventilation in 37 mechanically ventilated patients with Guillain-Barré syndrome (GBS) was studied. Patients ventilated for less than 3 weeks were compared with those ventilated more than 3 weeks. Daily vital capacity and maximal inspiratory and expiratory pressures were summed to an integrated pulmonary function (PF) score. We calculated the PF ratio, which represents the PF score at day 12 after intubation divided by the PF score on the day of intubation. The PF ratio was greater than 1 in all 10 patients ventilated less than 3 weeks and was less than 1 in 19 of 27 patients ventilated for longer (P = 0.0001, Fisher exact test). The sensitivity of a PF ratio less than 1 for predicting duration of ventilation greater than 3 weeks was 70%; the specificity and positive predictive value were 100%. This study thus suggests that serial postintubation respiratory tests can provide a measure of respiratory status in patients with GBS. These parameters may help predict duration of ventilation and need for tracheostomy. If, at day 12, the PF ratio is less than 1, it is highly unlikely that patients will be weaned within 3 weeks, and tracheostomy should be performed. If the ratio is greater than 1, tracheostomy should be deferred, because a substantial proportion of these patients may be successfully weaned from the ventilator within 3 weeks.

Phrenic nerve conduction studies in acute organophosphate poisoning

Phrenic nerve conduction studies were performed within 48 h of admission and subsequently in 29 patients (14 of whom required mechanical ventilation) with acute organophosphate (OP) poisoning. The mean (+/-SD) amplitude of the diaphragmatic compound muscle action potential (CMAP) in patients requiring mechanical ventilation (119.09 +/- 173.85 microV) was significantly lower than in those not requiring mechanical ventilation (461.63 +/- 138.69 microV) (P < 0.0001). Diaphragmatic CMAP amplitudes in ventilated patients increased with time during the course of hospitalization and were normal in 5 (36%) patients and only mildly reduced in another 6 (43%) patients prior to discontinuation of mechanical ventilation, which was undertaken 4-18 days (mean 7 +/- 3 days) after poisoning. Eleven patients (79%) were successfully weaned from mechanical ventilation at the first attempt. In the 3 (21%) remaining patients, mechanical ventilation had to be reestablished because of weaning failure. The mean (+/-SD) diaphragmatic CMAP amplitude, prior to discontinuation of ventilatory assistance, was 242.6 +/- 94.1 microV in these 3 patients. After ventilatory discontinuation, it fell to 95.5 +/- 105.8 microV. Thus, reduced diaphragmatic CMAP amplitudes correlate with the need for mechanical ventilation in acute OP poisoning.

Tracheostomy in Guillain-Barré syndrome

Specific treatment has been shown to shorten the duration of mechanical ventilation in Guillain-Barré syndrome (GBS) and could obviate the need for tracheostomy in a significant proportion of patients. However, the factors predictive of prolonged ventilation are undetermined, and the timing and use of tracheostomy in patients with GBS have not been systematically studied. The medical records of 60 patients ventilated for GBS were reviewed. Only 13 patients (22%) could be weaned within 3 weeks. Patients ventilated longer were significantly older (P = 0.04), and 21% had underlying pulmonary disease. Median duration of ventilation in patients treated with plasma exchange (n = 31) was not shortened. Fifty-two patients (87%) received a tracheostomy at a median of 9 days after intubation. In this series, where patients with comorbidity were included, tracheostomy was still necessary in the majority of ventilated patients. This procedure can be anticipated in elderly patients and in the presence of preexisting pulmonary disease.

Neuralgic amyotrophy with phrenic nerve involvement

Phrenic nerve involvement is a rare feature in patients with neuralgic amyotrophy (Parsonage-Turner syndrome). We report four patients who initially presented with severe dyspnea in the absence of lung disease. All patients had a history of infectious disease or surgery and of pain of sudden onset in the shoulder region. Weakness of the proximal arm was observed in only one. Radiographic and pulmonary function studies, phrenic nerve conduction studies, and needle electromyogram (EMG) of the diaphragm documented diaphragmatic paralysis which was unilateral in one patient, bilateral in two patients, and recurrent on alternating sides in another one. Follow-up studies remained abnormal for up to 4 years. Neuralgic amyotrophy with phrenic nerve involvement should be considered in patients presenting with severe, unexplained dyspnea of sudden onset.

AAEM case report 4: Guillain-Barré syndrome. American Association of Electrodiagnostic Medicine

A 57-year-old woman developed rapidly progressive, symmetric, extremity weakness, facial diplegia, ophthalmoplegia, respiratory insufficiency, and sensory ataxia over a 3-week period. Electrodiagnostic studies were performed on days 6, 13, and 50 following the onset of weakness. Motor nerve conduction abnormalities were the predominant findings. Prolonged motor distal latencies, prolonged or absent F waves, and partial motor conduction blocks were present and form the diagnostic features of an acquired, demyelinating polyneuropathy. Abnormalities in sensory nerve conductions and blink reflexes were also present. Guillain-Barré syndrome was diagnosed prompting the initiation of therapeutic plasma exchange. The patient's clinical status continued to worsen over the next 10 days before stabilizing. Considerable improvement in extremity strength, ocular motility, and respiratory function occurred in the subsequent weeks. Well-planned and well-executed electrodiagnostic studies generate key adjunctive data to the clinical diagnosis of Guillain-Barré syndrome.

Respiratory aspects of neurological disease

Neurological disease may result in respiratory dysfunction; however the manifestations of respiratory dysfunction in such patients may be atypical because of wider effects of their underlying condition. In the present review we have considered separately acute neuromuscular respiratory disease (as well as aspects of respiratory muscle function relevant to intensive care), chronic neuromuscular respiratory disease, sleep related disorders, respiratory consequences of specific neurological diseases, and neurological features of respiratory disease. Approaches to specific clinical problems are discussed; in many instances this can be expedited by close cooperation with a respiratory physician. We suggest that management of respiratory dysfunction in neurological disease depends critically on three factors: firstly, knowledge of when respiratory dysfunction is likely to occur; secondly, maintaining a high index of clinical suspicion (specifically apparently vague symptoms should not be uncritically attributed to the underlying neurological condition); and, thirdly, the pursuing of appropriate investigations.

Clinical and electrophysiological findings in critical illness polyneuropathy

Sixty two patients with critical illness polyneuropathy (CIP) were studied prospectively to determine the clinical and electrophysiological profile, to assess the prognostic value of respiratory electrophysiology in determining the duration of ventilation and to analyze the role of neuromuscular blocking agents (NMBA) and steroids. Limb motor and sensory nerve conductions, bilateral phrenic nerve onset latencies, bilateral diaphragmatic compound muscle action potentials (CMAP), unilateral diaphragmatic needle electromyography (EMG), limb muscle EMG, time on the ventilator, time in the intensive care unit (ICU), dosage of NMBA and steroids were analyzed in 62 patients. The diagnosis of CIP was made by clinical criteria, electrophysiological criteria and exclusion of any other condition suspicious of an axonal neuropathy. The results of phrenic nerve conduction studies and diaphragmatic EMG were compared to normal mean values in 25 healthy subjects. The most common finding in our study were reduced CMAPs and abnormal spontaneous activity in muscle, occuring in 100%. Forty per cent had reduced CMAPs but normal sensory nerve action potentials (SNAP). These patients had normal CK-levels and normal findings, unspecific changes, type 2 fibre atrophy or denervation atrophy on muscle biopsy. Seventy seven per cent of patients had abnormal diaphragmatic CMAPs and spontaneous activity in the diaphragm indicating denervation of the diaphragm is common in CIP. There was no statistically significant relationship to the dosage of NMBA and steroids, and the respiratory electrophysiological studies, duration of ventilation and stay in the ICU.

Electrophysiological respiratory studies in the critical care unit

Respiratory electrophysiological studies are useful in the investigation and monitoring of respiratory failure. Phrenic nerve conduction studies and needle electromyography of the diaphragm are invaluable in establishing the diagnosis, determining the severity, and following the progression of peripheral respiratory muscle dysfunction. In addition to these established methods, repetitive phrenic nerve stimulation is of diagnostic value in patients with neuromuscular transmission defects and dyspnea. The diagnosis of impaired central respiratory drive can often be accomplished by the newly-developed techniques of transcortical magnetic stimulation of the motor cortex with recording of the diaphragm and phrenic nerve somatosensory evoked potentials. These studies are of particular value in critically ill patients where both the central and peripheral lesions may impair respiration.