Researching COVID to Enhance Recovery (RECOVER) adult study protocol: Rationale, objectives, and design

IMPORTANCE

SARS-CoV-2 infection can result in ongoing, relapsing, or new symptoms or other health effects after the acute phase of infection; termed post-acute sequelae of SARS-CoV-2 infection (PASC), or long COVID. The characteristics, prevalence, trajectory and mechanisms of PASC are ill-defined. The objectives of the Researching COVID to Enhance Recovery (RECOVER) Multi-site Observational Study of PASC in Adults (RECOVER-Adult) are to: (1) characterize PASC prevalence; (2) characterize the symptoms, organ dysfunction, natural history, and distinct phenotypes of PASC; (3) identify demographic, social and clinical risk factors for PASC onset and recovery; and (4) define the biological mechanisms underlying PASC pathogenesis.

METHODS

RECOVER-Adult is a combined prospective/retrospective cohort currently planned to enroll 14,880 adults aged ≥18 years. Eligible participants either must meet WHO criteria for suspected, probable, or confirmed infection; or must have evidence of no prior infection. Recruitment occurs at 86 sites in 33 U.S. states, Washington, DC and Puerto Rico, via facility- and community-based outreach. Participants complete quarterly questionnaires about symptoms, social determinants, vaccination status, and interim SARS-CoV-2 infections. In addition, participants contribute biospecimens and undergo physical and laboratory examinations at approximately 0, 90 and 180 days from infection or negative test date, and yearly thereafter. Some participants undergo additional testing based on specific criteria or random sampling. Patient representatives provide input on all study processes. The primary study outcome is onset of PASC, measured by signs and symptoms. A paradigm for identifying PASC cases will be defined and updated using supervised and unsupervised learning approaches with cross-validation. Logistic regression and proportional hazards regression will be conducted to investigate associations between risk factors, onset, and resolution of PASC symptoms.

DISCUSSION

RECOVER-Adult is the first national, prospective, longitudinal cohort of PASC among US adults. Results of this study are intended to inform public health, spur clinical trials, and expand treatment options.

REGISTRATION

NCT05172024.

Development of a Definition of Postacute Sequelae of SARS-CoV-2 Infection

Importance

SARS-CoV-2 infection is associated with persistent, relapsing, or new symptoms or other health effects occurring after acute infection, termed postacute sequelae of SARS-CoV-2 infection (PASC), also known as long COVID. Characterizing PASC requires analysis of prospectively and uniformly collected data from diverse uninfected and infected individuals.

Objective

To develop a definition of PASC using self-reported symptoms and describe PASC frequencies across cohorts, vaccination status, and number of infections.

Design, Setting, and Participants

Prospective observational cohort study of adults with and without SARS-CoV-2 infection at 85 enrolling sites (hospitals, health centers, community organizations) located in 33 states plus Washington, DC, and Puerto Rico. Participants who were enrolled in the RECOVER adult cohort before April 10, 2023, completed a symptom survey 6 months or more after acute symptom onset or test date. Selection included population-based, volunteer, and convenience sampling.

Exposure

SARS-CoV-2 infection.

Main Outcomes and Measures

PASC and 44 participant-reported symptoms (with severity thresholds).

Results

A total of 9764 participants (89% SARS-CoV-2 infected; 71% female; 16% Hispanic/Latino; 15% non-Hispanic Black; median age, 47 years [IQR, 35-60]) met selection criteria. Adjusted odds ratios were 1.5 or greater (infected vs uninfected participants) for 37 symptoms. Symptoms contributing to PASC score included postexertional malaise, fatigue, brain fog, dizziness, gastrointestinal symptoms, palpitations, changes in sexual desire or capacity, loss of or change in smell or taste, thirst, chronic cough, chest pain, and abnormal movements. Among 2231 participants first infected on or after December 1, 2021, and enrolled within 30 days of infection, 224 (10% [95% CI, 8.8%-11%]) were PASC positive at 6 months.

Conclusions and Relevance

A definition of PASC was developed based on symptoms in a prospective cohort study. As a first step to providing a framework for other investigations, iterative refinement that further incorporates other clinical features is needed to support actionable definitions of PASC.

Ubiquitous neurocognitive dysfunction in familial adenomatous polyposis: proof-of-concept of the role of APC protein in neurocognitive function

BACKGROUND

Familial adenomatous polyposis (FAP) is an autosomal dominant disorder caused by germline mutations in the APC gene. Patients with FAP have multiple extraintestinal manifestations that follow a genotype-phenotype pattern; however, few data exist characterizing their cognitive abilities. Given the role of the APC protein in development of the central nervous system, we hypothesized that patients with FAP would show differences in cognitive functioning compared to controls.

METHODS

Matched case-control study designed to evaluate cognitive function using the Test of Nonverbal Intelligence-4, the Bateria III Woodcock-Munoz, and the Behavior Rating Inventory of Executive Functions-Adult. Twenty-six individuals with FAP (mean age = 34.2 ± 15.0 years) and 25 age-gender and educational level matched controls (mean age = 32.7 ± 13.8 years) were evaluated.

RESULTS

FAP-cases had significantly lower IQ (p = 0.005). Across all tasks of the Batería III Woodcock-Muñoz, FAP-cases performed significantly lower than controls, with all of the summary scores falling in the bottom quartile compared to controls (p < 0.0001). Patients with FAP scored within the deficient range for Long-Term Retrieval and Cognitive Fluency.

CONCLUSION

APC protein has an important role in neurocognitive function. The pervasive nature of the observed cognitive dysfunction suggests that loss or dysfunction of the APC protein impacts processes in cortical and subcortical brain regions. Additional studies examining larger ethnically diverse cohorts with FAP are warranted.

The Research Centers in Minority Institutions (RCMI) Translational Research Network: Building and Sustaining Capacity for Multi-Site Basic Biomedical, Clinical and Behavioral Research

The Research Centers in Minority Institutions (RCMI) program was established by the US Congress to support the development of biomedical research infrastructure at minority-serving institutions granting doctoral degrees in the health professions or in a health-related science. RCMI institutions also conduct research on diseases that disproportionately affect racial and ethnic minorities (ie, African Americans/Blacks, American Indians and Alaska Natives, Hispanics, Native Hawaiians and Other Pacific Islanders), those of low socioeconomic status, and rural persons. Quantitative metrics, including the numbers of doctoral science degrees granted to underrepresented students, NIH peer-reviewed research funding, peer-reviewed publications, and numbers of racial and ethnic minorities participating in sponsored research, demonstrate that RCMI grantee institutions have made substantial progress toward the intent of the Congressional legislation, as well as the NIH/NIMHD-linked goals of addressing workforce diversity and health disparities. Despite this progress, nationally, many challenges remain, including persistent disparities in research and career development awards to minority investigators. The continuing underrepresentation of minority investigators in NIH-sponsored research across multiple disease areas is of concern, in the face of unrelenting national health inequities. With the collaborative network support by the RCMI Translational Research Network (RTRN), the RCMI community is uniquely positioned to address these challenges through its community engagement and strategic partnerships with non-RCMI institutions. Funding agencies can play an important role by incentivizing such collaborations, and incorporating metrics for research funding that address underrepresented populations, workforce diversity and health equity.

Implementation and Evaluation of Guillain-Barré Syndrome Surveillance in Puerto Rico during the 2016 Zika Virus Epidemic

OBJECTIVE

Guillain-Barré syndrome (GBS) is an uncommon autoimmune disorder that follows infection or vaccination, and increased incidence has been reported during Zika virus (ZIKV) transmission. During the 2016 ZIKV epidemic, the Puerto Rico Department of Health (PRDH) implemented the Enhanced GBS Surveillance System (EGBSSS). Here, we describe EGBSSS implementation and evaluate completeness, validity, and timeliness.

METHODS

GBS cases were identified using passive surveillance and discharge diagnostic code for GBS. Completeness was evaluated by capture-recapture methods. Sensitivity and positive predictive value (PPV) for confirmed GBS cases were calculated for both case identification methods. Median time to completion of key time steps were compared by quarter (Q1-4) and hospital size.

RESULTS

A total of 122 confirmed GBS cases with onset of neurologic illness in 2016 were identified. Capture-recapture methodology estimated that four confirmed GBS cases were missed by both identification methods. Identification of cases by diagnostic code had a higher sensitivity than passive surveillance (89% vs. 80%), but a lower PPV (60% vs. 72%). There was a significant decrease from Q1 to Q3 in median time from hospital admission to case reporting (11 days vs. 2 days, p = 0.032) and from Q2 to Q3 in median time from specimen receipt to arbovirus laboratory test reporting (35 days vs. 26 days, p = 0.004).

CONCLUSION

EGBSSS provided complete, valid, and increasingly timely surveillance data, which guided public health action and supported healthcare providers during the ZIKV epidemic. This evaluation provides programmatic lessons for GBS surveillance and emergency response surveillance.

Clinical Features of Guillain-Barré Syndrome With vs Without Zika Virus Infection, Puerto Rico, 2016

Importance

The pathophysiologic mechanisms of Guillain-Barré syndrome (GBS) associated with Zika virus (ZIKV) infection may be indicated by differences in clinical features.

Objective

To identify specific clinical features of GBS associated with ZIKV infection.

Design, Setting, and Participants

During the ZIKV epidemic in Puerto Rico, prospective and retrospective strategies were used to identify patients with GBS who had neurologic illness onset in 2016 and were hospitalized at all 57 nonspecialized hospitals and 2 rehabilitation centers in Puerto Rico. Guillain-Barré syndrome diagnosis was confirmed via medical record review using the Brighton Collaboration criteria. Specimens (serum, urine, cerebrospinal fluid, and saliva) from patients with GBS were tested for evidence of ZIKV infection by real-time reverse transcriptase-polymerase chain reaction; serum and cerebrospinal fluid were also tested by IgM enzyme-linked immunosorbent assay. In this analysis of public health surveillance data, a total of 123 confirmed GBS cases were identified, of which 107 had specimens submitted for testing; there were 71 patients with and 36 patients without evidence of ZIKV infection. Follow-up telephone interviews with patients were conducted 6 months after neurologic illness onset; 60 patients with and 27 patients without evidence of ZIKV infection participated.

Main Outcomes and Measures

Acute and long-term clinical characteristics of GBS associated with ZIKV infection.

Results

Of 123 patients with confirmed GBS, the median age was 54 years (age range, 4-88 years), and 68 patients (55.3%) were male. The following clinical features were more frequent among patients with GBS and evidence of ZIKV infection compared with patients with GBS without evidence of ZIKV infection: facial weakness (44 [62.0%] vs 10 [27.8%]; P < .001), dysphagia (38 [53.5%] vs 9 [25.0%]; P = .005), shortness of breath (33 [46.5%] vs 9 [25.0%]; P = .03), facial paresthesia (13 [18.3%] vs 1 [2.8%]; P = .03), elevated levels of protein in cerebrospinal fluid (49 [94.2%] vs 23 [71.9%]; P = .008), admission to the intensive care unit (47 [66.2%] vs 16 [44.4%]; P = .03), and required mechanical ventilation (22 [31.0%] vs 4 [11.1%]; P = .02). Six months after neurologic illness onset, patients with GBS and evidence of ZIKV infection more frequently reported having excessive or inadequate tearing (30 [53.6%] vs 6 [26.1%]; P = .03), difficulty drinking from a cup (10 [17.9%] vs 0; P = .03), and self-reported substantial pain (15 [27.3%] vs 1 [4.3%]; P = .03).

Conclusions and Relevance

In this study, GBS associated with ZIKV infection was found to have higher morbidity during the acute phase and more frequent cranial neuropathy during acute neuropathy and 6 months afterward. Results indicate GBS pathophysiologic mechanisms that may be more common after ZIKV infection.

Acute Zika Virus Infection as a Risk Factor for Guillain-Barré Syndrome in Puerto Rico

This case-control study conducted during the Zika virus epidemic in Puerto Rico estimates the association between preceding Zika virus infection and subsequent Guillain-Barré syndrome.

Incidence and clinical characteristics of Guillain-Barré syndrome before the introduction of Zika virus in Puerto Rico

BACKGROUND

Zika virus has been associated with increases in Guillain-Barré syndrome (GBS) incidence. A GBS incidence estimation and clinical description was performed to assess baseline GBS epidemiology before the introduction of Zika virus in Puerto Rico.

METHODS

Hospitalization administrative data from an island-wide insurance claims database and U.S. Census Bureau population estimates provided a crude GBS incidence for 2013. This estimate was adjusted using the proportion of GBS cases meeting Brighton criteria for confirmed GBS from nine reference hospitals. Characteristics of confirmed GBS cases in the same nine hospitals during 2012-2015 are described.

RESULTS

A total of 136 GBS hospitalization claims were filed in 2013 (crude GBS incidence was 3.8 per 100,000 population). The adjusted GBS incidence was 1.7 per 100,000 population. Of 67 confirmed GBS cases during 2012-2015, 66% had an antecedent illness. Median time from antecedent illness to GBS onset was 7days. Most cases (67%) occurred during July-September.

CONCLUSIONS

Puerto Rico's GBS incidence for 2013 was estimated using a combination of administrative data and medical records review; this method could be employed in other regions to monitor GBS incidence before and after the introduction of GBS infectious triggers.

Local Transmission of Zika Virus--Puerto Rico, November 23, 2015-January 28, 2016

Zika virus, a mosquito-borne flavivirus, spread to the Region of the Americas (Americas) in mid-2015, and appears to be related to congenital microcephaly and Guillain-Barré syndrome (1,2). On February 1, 2016, the World Health Organization (WHO) declared the occurrence of microcephaly cases in association with Zika virus infection to be a Public Health Emergency of International Concern.* On December 31, 2015, Puerto Rico Department of Health (PRDH) reported the first locally acquired (index) case of Zika virus disease in a jurisdiction of the United States in a patient from southeastern Puerto Rico. During November 23, 2015-January 28, 2016, passive and enhanced surveillance for Zika virus disease identified 30 laboratory-confirmed cases. Most (93%) patients resided in eastern Puerto Rico or the San Juan metropolitan area. The most frequently reported signs and symptoms were rash (77%), myalgia (77%), arthralgia (73%), and fever (73%). Three (10%) patients were hospitalized. One case occurred in a patient hospitalized for Guillain-Barré syndrome, and one occurred in a pregnant woman. Because the most common mosquito vector of Zika virus, Aedes aegypti, is present throughout Puerto Rico, Zika virus is expected to continue to spread across the island. The public health response in Puerto Rico is being coordinated by PRDH with assistance from CDC. Clinicians in Puerto Rico should report all cases of microcephaly, Guillain-Barré syndrome, and suspected Zika virus disease to PRDH. Other adverse reproductive outcomes, including fetal demise associated with Zika virus infection, should be reported to PRDH. To avoid infection with Zika virus, residents of and visitors to Puerto Rico, particularly pregnant women, should strictly follow steps to avoid mosquito bites, including wearing pants and long-sleeved shirts, using permethrin-treated clothing and gear, using an Environmental Protection Agency (EPA)-registered insect repellent, and ensuring that windows and doors have intact screens.

Epidermal innervation in healthy children and adolescents

INTRODUCTION

Epidermal nerve fiber (ENF) density, morphology, and epidermal innervation patterns were examined in children using 2 different techniques, punch biopsy and suction blister.

METHODS

Healthy children without symptoms or history of peripheral neuropathy and normal by neurologic examination were studied. Punch biopsy and suction blister specimens were collected from the lateral thigh and distal leg. ENFs were traced from confocal images of immunohistochemically stained samples. Statistical methods included repeated-measures analysis of covariance.

RESULTS

Blister and biopsy nerve counts were associated. ENF density in children was dense, lower for older children (P<0.01) and with no difference between boys and girls (P=0.92). Many ENFs appeared multibranched and elongated.

CONCLUSIONS

Epidermal innervation in the pediatric population is dense and age-dependent. Blister specimens are less invasive and may provide an alternative to punch biopsy for determining ENF density in children at risk for neuropathy.

Decoding pathogenesis of slow-channel congenital myasthenic syndromes using recombinant expression and mice models

Despite the fact that they are orphan diseases, congenital myasthenic syndromes (CMS) challenge those who suffer from it by causing fatigable muscle weakness, in the most benign cases, to a progressive wasting of muscles that may sentence patients to a wheelchair or even death. Compared to other more common neurological diseases, CMS are rare. Nevertheless, extensive research in CMS is performed in laboratories such as ours. Among the diverse neuromuscular disorders of CMS, we are focusing in the slow-channel congenital myasthenic syndrome (SCS), which is caused by mutations in genes encoding acetylcholine receptor subunits. The study of SCS has evolved from clinical electrophysiological studies to in vitro expression systems and transgenic mice models. The present review evaluates the methodological approaches that are most commonly employed to assess synaptic impairment in SCS and also provides perspectives for new approaches. Electrophysiological methodologies typically employed by physicians to diagnose patients include electromyography, whereas patient muscle samples are used for intracellular recordings, single-channel recordings and toxin binding experiments. In vitro expression systems allow the study of a particular mutation without the need of patient intervention. Indeed, in vitro expression systems have usually been implicated in the development of therapeutic strategies such as quinidine- and fluoxetine-based treatments and, more recently, RNA interference. A breakthrough in the study of SCS has been the development of transgenic mice bearing the mutations that cause SCS. These transgenic mice models have actually been key in the elucidation of the pathogenesis of the SCS mutations by linking IP-3 receptors to calcium overloading, as well as caspases and calpains to the hallmark of SCS, namely endplate myopathy. Finally, we summarize our experiences with suspected SCS patients from a local perspective and comment on one aspect of the contribution of our group in the study of SCS.

Fatal granulomatous meningoencephalitis associated to mycobacterium mucogenicum-like microorganism: a case report

Mycobacterium mucogenicum is rarely associated to human infections. However, in the last year, a few reports of sepsis and fatal cases of central nervous systems have been documented. Here we report a fatal case of granulomatous meningoencephalitis of three weeks of evolution where DNA from a M. mucogenicum-like microorganism was identified postmortem in samples of brain tissue.

Subcutaneous IGF-1 is not beneficial in 2-year ALS trial

BACKGROUND

Previous human clinical trials of insulin-like growth factor type I (IGF-1) in amyotrophic lateral sclerosis (ALS) have been inconsistent. This phase III, randomized, double-blind, placebo-controlled study was undertaken to address whether IGF-1 benefited patients with ALS.

METHODS

A total of 330 patients from 20 medical centers were randomized to receive 0.05 mg/kg body weight of human recombinant IGF-1 given subcutaneously twice daily or placebo for 2 years. The primary outcome measure was change in their manual muscle testing score. Secondary outcome measures included tracheostomy-free survival and rate of change in the revised ALS functional rating scale. Intention to treat analysis was used.

RESULTS

There was no difference between treatment groups in the primary or secondary outcome measures after the 2-year treatment period.

CONCLUSIONS

Insulin-like growth factor type I does not provide benefit for patients with amyotrophic lateral sclerosis.

Recent developments in the HIV neuropathies

PURPOSE OF REVIEW

With the introduction of highly active antiretroviral therapy peripheral neuropathies have become the most common neurological complications in HIV infection. The frequency and spectrum of these neuropathies are changing, as the various toxic and immune factors are modified by new treatment strategies. Recent studies have provided a better understanding of the risk factors, markers and relevant pathogenic mechanisms, and a thorough review of these is critical for an improved understanding of this important and increasingly common complication.

RECENT FINDINGS

The combined use of dideoxynucleosides, in association with immune-mediated mechanisms triggered by HIV infection, are critical in the development of distal sensory polyneuropathy. Valuable markers of neuropathy such as intraepidermal nerve fiber density from skin biopsies have been validated and promise to be a valuable tool in the detection and monitoring of distal sensory polyneuropathy. Markers of virological activity have also been associated with the severity of neuropathic pain in distal sensory polyneuropathy. In some instances, the enhanced viral suppression from antiretroviral agents may actually improve or decrease the frequency of certain types of neuropathy. New evidence supports mitochondrial toxicity as a principal mechanism for dideoxynucleoside-associated sensory neuropathy, and questions arise about enhanced risk with pre-existing mitochondrial defects. Confirmed treatments are limited to the reduction of symptoms, with a need for the further investigation of corrective therapies.

SUMMARY

Increased and improved surveillance for HIV-associated neuropathy will allow earlier interventions to improve quality of life and prevent severe toxicities. A better understanding of the prevailing mechanisms will allow for more effective interventions.

Physiological characterization of neuropathy in Fabry's disease

Fabry's disease is commonly associated with a painful, debilitating neuropathy. Characterization of the physiological abnormalities is an important step in evaluating response to specific therapies. Twenty-two patients with Fabry's disease, and with relatively preserved renal function, underwent conventional and near-nerve conduction studies, electromyography, sympathetic skin responses, and quantitative sensory testing (QST). Nerve conduction studies were mostly normal except for an increased frequency of median nerve entrapment at the wrist in 6 (27%) patients. Sympathetic skin responses were preserved in 19 of 20 (95%) of the patients. The QST showed increased or immeasurable cold and warm detection thresholds in patients, significantly different from controls (n = 28) in the hand (P < 0.001, P = 0.04, respectively) and foot (P < 0.001 for both). Cold thresholds were more often abnormal than were warm thresholds. Vibration thresholds were normal in the feet and, in some patients, elevated in the hand only, probably due to frequent median nerve entrapment at the wrist. Our findings suggest that the neuropathy of Fabry's disease is characterized by an increased prevalence of median nerve entrapment at the wrist and by thermal afferent fiber dysfunction in a length-dependent fashion, with greater impairment of cold than warm sensation.

Nerve conduction abnormalities in aging mice deficient for myelin-associated glycoprotein

Ultrastructural, biochemical, and electrophysiological analyses were done on 12-14-month-old mice deficient for myelin-associated glycoprotein (MAG) to further characterize the neuropathy that develops as they age. Electron microscopy demonstrated normal myelin compaction and axonal degeneration in a large number of myelinated nerve fibers. Western blots showed that the proteins of compact myelin, P0 glycoprotein, and myelin basic protein were not significantly altered in the mutants; however, the Schwann cell protein, 2',3'-cyclic nucleotide 3'-phosphodiesterase, was reduced to less than half the control level. Also, both total and phosphorylated high-molecular-weight neurofilament proteins (TNFH and PNFH, respectively) were significantly decreased, as was the PNFH:TNFH ratio. Electrophysiological evaluation revealed a mild, but statistically significant, reduction of conduction velocity and a nonsignificant mild decrease in compound muscle action potential amplitudes. This constellation of findings in aging MAG-null mice is consistent with an axonopathy that resembles axonal Charcot-Marie-Tooth (CMT2) disease in many respects. Thus, mutation of a myelin-associated gene expressed by Schwann cells can induce axonal degeneration and cause a neuropathy with minimal signs of demyelination.

Cutaneous silent periods in patients with Fabry disease

We assessed the cutaneous silent period (CSP) in 24 patients with Fabry disease with small-fiber sensory neuropathy and 12 normal subjects to test the hypothesis that small-diameter afferents are responsible for producing the CSP. Sensory nerve conduction studies and quantitative sensory testing for cold and vibration detection thresholds were also measured. Overall, Fabry patients had impaired thermal, but not vibration, detection thresholds, with greatest impairment in the feet. In the upper extremity, CSP latencies, duration, and suppression of electromyographic activity (EMG) did not differ. In the lower extremity, patients had reduced suppression of EMG during the CSP compared to normal controls. CSP durations exhibited a bimodal distribution in patients, including a subset of seven patients with durations shorter than all controls. This subset had profound loss of thermal sensation in the feet, but this was also true of some patients who had normal CSPs. Patients with shortened CSPs had modestly elevated vibration thresholds and reduced sensory potentials in comparison to patients with normal CSPs. Reduced CSPs in Fabry patients are associated with, but not entirely explained by, the severity of small-fiber neuropathy as measured by quantitative sensory testing. The possibility that large-diameter fibers provide a minor contribution to producing the CSP should be considered.

[Important aspects of the diagnosis and management of peripheral neuropathies]

INTRODUCTION

The peripheral neuropathies represent a diverse group of disorders of the peripheral nervous system of very varied aetiology. It is therefore important to classify them, so as to reduce the number of possible diagnoses and to identify the correct cause.

OBJECTIVE

To review the most important principles of the initial examination and the management of peripheral neuropathies.

DEVELOPMENT

The clinical features of these diseases may be debilitating and incapacitating, and may be part of a symptom complex of very serious diseases. It is necessary to carry out systematic evaluation of the symptoms, signs and laboratory tests so as to establish the correct diagnosis and begin treatment. Some of the most important elements used in the process of classification are: functional findings, topography or the anatomical pattern of the deficits, and the physiological or pathological findings. Treatment of the peripheral neuropathies may be divided into four groups: elimination of the casual agent, treatment of symptoms, modulation of the immune system and rehabilitation.

CONCLUSION

The possibilities of diagnosis and treatment continue to increase as the mechanisms responsible become clearer.

[Chronic inflammatory neuropathies]

INTRODUCTION

The group of chronic inflammatory neuropathies is made up of a variety of neuropathies of autoimmune or infectious origin.

DEVELOPMENT

We describe three types of neuropathies and their treatment: demyelinating chronic neuropathy, motor multifocal neuropathy and demyelinating neuropathy associated with monoclonal gammapathy. These three types of neuropathy have uniform characteristics and features, which permit precise identification and suggest that they are separate entities.

CONCLUSIONS

In the management of any type of neuropathy it is essential to make the correct diagnosis. Initial investigations should include detailed electrophysiological examination to detect the presence of demyelination, lumbar puncture and, if pleocytosis is found, the possibility of associated acquired immunodeficiency syndrome should be investigated. Also, before immunosuppressive treatment is begun, a systematic medical examination should be done to detect any other coexisting illness which might affect use of the different drugs involved.

[Plasmapheresis, immunotherapy and chemotherapy in polyneuropathies]

INTRODUCTION

Although the precise cause of many of the polyneuropathies evaluated clinically is unknown, there is substantial evidence that many are caused by autoimmune disorders. Currently treatment is directed towards production of immunomodulation or immunosuppression.

DEVELOPMENT AND CONCLUSIONS

The degree of subjective symptoms such as fatigue, pain or other sensory symptoms are not good criteria for determination of the need for immunosuppressive treatment. Treatment should be orientated towards serious neuropathic defects, not minimal deficits. It is therefore important to record the defect precisely, so as to be able to determine objectively the effect of therapy. For this, tables or diagrams using established scales, such as that of the Medical Research Council, are recommended. Similarly, evaluation and follow-up by the physical therapy and occupational therapy departments should be considered when deciding the treatment to be used for autoimmune neuropathies such as corticosteroids, plasmapheresis, ev immunoglobulin, cytopathic agents and alpha interferon.

Molecular mimicry in chronic inflammatory demyelinating polyneuropathy and melanoma

Polyclonal immunoglobulin M antibodies to the monosialoganglioside GM2, sulfoglucuronyl glycolipids, and sulfatide were detected by thin-layer chromatography and enzyme-linked immunosorbent assay in the serum of a patient with melanoma and chronic inflammatory demyelinating polyneuropathy. Both the patient's serum and polyclonal antibodies against GM2 reacted strongly with a biopsy of melanomatous tissue from the patient, suggesting a process of molecular mimicry.

Central motor conduction time: reproducibility and discomfort of different methods

Central motor conduction time, a useful measure for studying central motor pathways, is calculated by determining the difference between the latency of motor-evoked potentials and peripheral conduction time. The intraindividual trial-to-trial variability of central motor conduction time and the discomfort associated with three methods of measuring peripheral motor conduction time (F-wave latency, cervical magnetic stimulation, and cervical needle stimulation) were studied in 5 healthy subjects with the use of transcranial magnetic stimulation to elicit motor-evoked potentials. Central motor conduction time was calculated by using measurements, made on 3 separate days, from the same three muscles on each hand. A visual analog pain scale was used to determine the level of discomfort for each method. Intraindividual trial-to-trial variability of central motor conduction time was similar for all methods, with coefficients of variation of 13% for the F-wave latency, 15% for cervical magnetic stimulation, and 11% for cervical needle stimulation. The last method was significantly more painful than the other two methods; there was no significant difference in discomfort between the F-wave method and cervical magnetic stimulation. To assess peripheral motor conduction time, when determining central motor conduction time, either the F-wave method or cervical magnetic stimulation is preferable to cervical needle stimulation.

Peripheral neuropathy in children with HIV infection

Peripheral neuropathy is infrequently reported in children with HIV infection, but may be underrecognized. To provide a better understanding of the patterns of peripheral neuropathy in these children, we surveyed the charts of 50 children with HIV infection referred to the EMG laboratory at the National Institutes of Health for evaluation of suspected peripheral neuropathy. Twelve children had an abnormal nerve conduction study. The findings suggested a distal sensory or sensorimotor axonal neuropathy in seven children, median nerve compression at the carpal tunnel in three, a demyelinating neuropathy in one child, and a lumbosacral polyradiculopathy in one adolescent. Distal symmetric polyneuropathy occurred mostly in older-aged children.

Inclusion body myositis: no evidence for a neurogenic component

Because electrophysiologic, clinical, and histopathologic observations have suggested that inclusion body myositis (IBM) may have a coexistent neurogenic component, we used macro-electromyography (macro-EMG) to search for changes in the motor unit territory and signs of reinnervation. We studied 11 patients, aged 53 to 77 years (mean, 65.2 years), with typical, nonfamilial IBM lasting a mean of 8.5 years, and eight healthy volunteers aged 54 to 70 years (mean, 64.6 years), as control subjects. Nerve conduction studies showed focal abnormalities in 5 of the patients, but no evidence of a polyneuropathy. Concentric needle EMG in various proximal and distal muscles of the upper and lower limbs revealed short- or long-duration complex motor unit potentials (MUPs) or a mixture of both types of MUPs. Macro-EMG studies in the tibialis anterior muscle showed smaller macro-MUP amplitudes and areas in patients than in normal subjects. Four patients had abnormal macro-EMG studies with an increased number of small macro-MUPs, 1 patient had an equivocal study with large-amplitude but normal-area macro-MUPs, and the remaining 6 patients had normal studies. These findings are consistent with a primary muscle disorder similar to those seen in other myopathies. We conclude that macro-EMG does not support a coexistent neurogenic component in patients with IBM compared with normal subjects of similar age.

Electrophysiologic and histologic studies in clinically unaffected muscles of patients with prior paralytic poliomyelitis

Macro-electromyography (macro-EMG) studies have provided important information about the size of the motor units and the degree of reinnvervation in clinically affected muscles of patients with a history of poliomyelitis and postpolio syndrome. The study of clinically unaffected muscles and correlation of their electrophysiologic characteristics with the muscle architecture could provide meaningful information about the ongoing subclinical denervation. We performed macro-EMG and concomitantly measured fiber density in the clinically unaffected gastrocnemius muscle of 10 patients with postpolio syndrome and 10 normal subjects of similar age. We also performed biopsies on the gastrocnemius muscle of 8 of the patients. The median amplitude and area of the macro-motor unit potentials (macro-MUPs) were increased in 8 of the 10 patients, and occasionally were five times as large as the mean median value for the normal subjects. Seven biopsy specimens showed moderate to very large fiber-type grouping. In 5 patients, there was correlation between the electrophysiologic and histologic indices of reinnervation. Amplitude and area of the macro-MUPs were associated with the muscle fiber cross-sectional area. We conclude that clinically unaffected muscles of patients with postpolio syndrome often have large motor units as the result of effective reinnervation after the original motor neuron loss. In spite of possible differences in the cytoarchitecture of muscles affected to different degrees, macro-EMG and fiber density measurements are reliable noninvasive techniques for studying the extent and effectiveness of reinnervation in patients with postpolio syndrome.

Mixed nerve action potentials in acquired demyelinating polyneuropathy

Uncertainty about motor and sensory contributions in abnormal nerves has limited the use of mixed nerve action potentials (MNAPs). We recorded MNAPs in 21 patients with an acquired demyelinating neuropathy, 18 age-matched control subjects, and 10 patients with an axonal polyneuropathy. Bipolar and unipolar recordings from median and ulnar nerves were made above the elbow after electrical stimulation of the nerves at the wrist. Antidromic digital sensory action potentials and motor conduction velocity were also recorded for both nerves. In 19 median and 12 ulnar nerves from demyelinating polyneuropathy patients, compared with control subjects, MNAP amplitudes were significantly reduced (mean, 6 microV vs. 31 microV), MNAP velocities were mildly reduced (mean, 50 m/s vs. 62 m/s), motor conduction velocities were significantly reduced (mean, 33 m/s vs. 57 m/s), and MNAPs were significantly dispersed, with markedly prolonged rise times (mean 2.0 ms vs. 1.0 ms). Compared with the axonal polyneuropathy group, MNAP amplitudes from the median nerve were similarly reduced (mean, 8 microV vs. 9 microV), MNAP velocities were only slightly slower (mean, 52 m/s vs. 58 m/s), but the rise times were significantly prolonged (mean, 2.0 ms vs 1.2 ms). We conclude that, in acquired demyelinating neuropathies, the onset and, in some cases, the whole MNAP is from afferent fibers, which can be abnormally dispersed, and that, over the same segment MNAP velocity is less affected than motor conduction velocity.

Distal vacuolar myopathy in nephropathic cystinosis

Nephropathic cystinosis is a lysosomal storage disorder leading to renal failure by age 10 years. Prolonged patient survival following renal transplantation has allowed the development of previously unknown long-term complications. Muscle involvement has been reported in a single posttransplant cystinosis patient, but the range of clinical, electrophysiologic, and histologic features has not been fully described. Thirteen of 54 post-renal-transplant patients that we examined developed weakness and wasting in the small hand muscles, with or without facial weakness and dysphagia. Tendon reflexes were preserved and sensory examinations were normal. Electrophysiologic studies in 11 affected patients showed normal nerve conduction velocities and preserved sensory action potentials. The voluntary motor units in the affected distal muscles had reduced amplitude and brief duration, confirmed with quantitative electromyography in 4 patients. Biopsy of the severely affected abductor digiti minimi or extensor carpi radialis brevis muscles in 2 patients revealed marked fiber size variability, prominent acid phosphatase-positive vacuoles, and absence of fiber type grouping or inflammatory cells. Crystals of cystine were detected in perimysial cells but not within the muscle cell vacuoles. The muscle cystine content of clinically affected muscles was markedly elevated. We conclude that a distal vacuolar myopathy is a common late complication of untreated nephropathic cystinosis. Although the cause is unclear, the general lysosomal defect in this disease may also affect the lysosomes within muscle fibers.