Acute quadriplegic myopathy with loss of thick (myosin) filaments following heart transplantation

Neuromuscular problems of the critically Ill neonate and child

Acute neuromuscular disorders occasionally occur in the Pediatric Neurologic Intensive Care Unit. Many of these are primary disorders of the motor unit that may present acutely or exacerbate during an intercurrent illness. Additionally, acute neuromuscular disorders may develop during an acute systemic illness requiring intensive care management that predispose the child to another set of acute motor unit disorders. This chapter discusses acute neuromuscular crises in the infant, toddler, and adolescent, as well as neuromuscular disorders resulting from critical illness.

Critical illness-associated weakness and related motor disorders

Weakness of limb and respiratory muscles that occurs in the course of critical illness has become an increasingly common and serious complication of adult and pediatric intensive care unit patients and a cause of prolonged ventilatory support, morbidity, and prolonged hospitalization. Two motor disorders that occur singly or together, namely critical illness polyneuropathy and critical illness myopathy, cause weakness of limb and of breathing muscles, making it difficult to be weaned from ventilatory support, commencing rehabilitation, and extending the length of stay in the intensive care unit, with higher rates of morbidity and mortality. Recovery can take weeks or months and in severe cases, and may be incomplete or absent. Recent findings suggest an improved prognosis of critical illness myopathy compared to polyneuropathy. Prevention and treatment are therefore very important. Its management requires an integrated team approach commencing with neurologic consultation, creatine kinase (CK) measurement, detailed electrodiagnostic, respiratory and neuroimaging studies, and potentially muscle biopsy to elucidate the etiopathogenesis of the weakness in the peripheral and/or central nervous system, for which there may be a variety of causes. These tenets of care are being applied to new cases and survivors of the coronavirus-2 disease pandemic of 2019. This chapter provides an update to the understanding and approach to critical illness motor disorders.

Neurological Complications in Patients with Heart Transplantation

Neurological complications after heart transplantation are common and include cerebrovascular events (ischemic strokes, hemorrhagic strokes, and transient ischemic attacks), seizures, encephalopathy, central nervous system (CNS) infections, malignancies, and peripheral nervous system complications. Although most neurological complications are transient, strokes and CNS infections can result in high mortality and morbidity. Early recognition and timely management of these serious complications are crucial to improve survival and recovery. Diagnosing CNS infections can be challenging because their clinical presentation can be subtle in the setting of immunosuppression. Immunosuppressive medications themselves can cause a broad spectrum of neurological complications including seizures and posterior reversible encephalopathy syndrome. This article provides a review of the diagnosis and management of neurological complications after cardiac transplantation.

Neuromuscular complications of critical illness

Patients admitted to intensive care units (ICUs) suffer from a wide range of neurological disorders. Some develop within the ICU rendering weakness and difficulty in weaning patients from ventilator support. ICUAW, or ICU acquired weakness, is a broad term that includes several more specific neuromuscular problems. After exclusion of other causes of weakness, ICUAW includes critical illness polyneuropathy (CIP), first described by Charles Bolton, critical illness myopathy (CIM), and disorders of neuromuscular junction transmission. This chapter reviews the clinical, electrophysiological, and pathological features of these conditions and provides clinicians with approaches toward diagnosing and investigating ICUAW.

Neurologic aspects of heart transplantation

Cardiac transplantation remains the best treatment option for patients with end-stage, NYHA class IV heart failure who have failed conventional therapy. However, transplant rates have remained static largely due to limited organ donor supplies. Therefore, appropriate allocation of this precious resource is critical to maximize benefit, both at a patient level and at a societal level. Neurologic diseases, such as cerebrovascular disease and peripheral neuropathy, are prevalent in this patient population, as the major risk factors for heart disease place patients at risk for neurologic disease as well. Examples include hypertension, smoking, hypercholesterolemia, obesity, and diabetes. Pretransplant neurologic evaluation is very important to identify conditions that may limit survival after cardiac transplantation. In general, systemic diseases exacerbated by immunosuppression, conditions limiting ability to rehabilitate, and dementias are considered contraindications. Post-transplant neurologic complications are divided into central versus peripheral, and early versus late. The most common early complication is ischemic stroke. Other serious complications include hemorrhagic stroke, encephalopathy, and critical illness neuropathy. Over the long term, post-transplant immunosuppressive regimens are considered "a double edged sword." Although immunosuppressive medications are critical to preventing rejection and allograft dysfunction, they do have significant risk of morbidity and mortality associated with them, including neurologic side-effects. These include: (1) drug toxicities, such as lowering of seizure thresholds; (2) encephalopathy, such as posterior reversible encephalopathy syndrome (PRES); (3) infections; (4) malignancies, such as post-transplant lymphoproliferative disorder (PTLD). Many of the same considerations discussed in adult heart transplant recipients apply to pediatric heart transplant recipients as well. In children, seizures are the most common neurologic complication, although other neurologic complication rates are comparable.

Neuromuscular disorders in critically ill patients: review and update

Neuromuscular disorders that are diagnosed in the intensive care unit (ICU) usually cause substantial limb weakness and contribute to ventilatory dysfunction. Although some lead to ICU admission, ICU-acquired disorders, mainly critical illness myopathy (CIM) and critical illness polyneuropathy (CIP), are more frequent and are associated with considerable morbidity. Approximately 25% to 45% of patients admitted to the ICU develop CIM, CIP, or both. Their clinical features often overlap; therefore, nerve conduction studies and electromyography are particularly helpful diagnostically, and more sophisticated electrodiagnostic studies and histopathologic evaluation are required in some circumstances. A number of prospective studies have identified risk factors for CIP and CIM, but their limitations often include the inability to separate CIM from CIP. Animal models reveal evidence of a channelopathy in both CIM and CIP, and human studies also identified axonal degeneration in CIP and myosin loss in CIM. Outcomes are variable. They tend to be better with CIM, and some patients have longstanding disabilities. Future studies of well-characterized patients with CIP and CIM should refine our understanding of risk factors, outcomes, and pathogenic mechanisms, leading to better interventions.

[Neuromuscular complications in transplant recipients]

Neuromuscular complications in transplant recipients are common and contribute to morbidity and mortality. Complications such as acute and chronic inflammatory demyelinating polyneuropathies and toxic myopathies are related to the changes in immune modulation that occur after transplantation or result from immunosuppressive treatment toxicity. Alternatively, other complications such as myositis, myasthenia gravis, and mononeuropathy multiplex may result from a dysimmune systemic disorder such as post-transplant lymphoproliferative disorder, graft-versus-host disease or hepatitis C virus or hepatitis B virus chronic infection. Lastly, some of these complications, e.g., compression or stretch of individual nerves or plexus, are commonly seen in a postoperative setting and are not specific of patients with organ transplantation. This review focuses on the characteristic features, management, prognosis and pathophysiology of common and immune-related neuromuscular complications in organ transplant recipients.

Acute neuromuscular weakness in the intensive care unit

INTRODUCTION

Patients in the intensive care unit develop generalized weakness due to a number of factors. Neuromuscular weakness is a common cause of failure to wean from the ventilator and decreased limb movements. A rational approach to evaluation of weakness will help to identify most of the common causes of neuromuscular weakness in the intensive care unit.

AIMS

This review provides an analysis of neuromuscular weakness and a practical algorithm to assist in diagnostic evaluation.

CONCLUSIONS

The most common acquired causes of weakness in the critically ill patient in the intensive care unit are critical illness polyneuropathy and critical illness myopathy. In the intensive care unit setting, electrophysiological studies, biopsies, and imaging studies are often necessary to complement the clinical impression.

Neuromuscular disorders in medical and surgical ICUs: case studies in critical care neurology

The differential diagnosis of generalized weakness in ICU patients is quite broad. Although neuromuscular disorders are the most common causes of generalized weakness, a thorough evaluation is necessary to delineate the underlying cause of weakness. Biochemical studies, neuroimaging, and electrophysiologic studies help to delineate most of the common disorders associated with weakness. Prompt identification of a neurologic disorder and initiation of therapy speeds up recovery and reduces morbidity and mortality in these patients.

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.

Flaccid quadriplegia due to necrotizing myopathy following lung transplantation

Critical illness myopathy (CIM) which is common after sepsis and multiorgan failure also has been described after organ transplantation. Prior reports of CIM after lung transplantation have not recorded a necrotizing myopathy. We present a 42-year-old man who developed a necrotizing critical illness myopathy following bilateral orthotopic lung transplantation. In addition we provide pathological confirmation that the ventral roots, spinal cord and the rest of the neuraxis are preserved in this condition. Extensive muscle necrosis is documented.

Neuromuscular problems of the critically ill neonate and child

This review presents insights gained over 24 years of clinical and laboratory evaluations of children, newborn to 18 years of age, who present with acute weakness in the intensive care setting. The differential diagnosis of neuromuscular disorders in these cases begins with recognition of three categories-the infant and toddler, the older child and adolescent, and the child with critical illness-within which predisposition to specific disorders may be identified. Disorders originating from anterior horn cell, peripheral nerve, neuromuscular junction, and muscle cell are discussed with emphasis on presentation and electrophysiologic findings. Nerve conduction studies, electromyography, electroencephalography, cerebrospinal fluid analysis, and magnetic resonance imaging each play important diagnostic roles in the differentiation of neuromuscular disorders in the critically ill child. Case studies suggest the wide range of presentations these disorders may make to the pediatrician or pediatric neurologist.

The utility of muscle biopsy

Despite major advances in molecular genetics, histopathologic evaluation of muscle biopsy specimens continues to provide important diagnostic information in patients with suspected muscle diseases and in patients with vasculitic neuropathies. Muscle biopsy specimens are used in diagnosing many inherited as well as inflammatory and toxic myopathies. Furthermore, the study of muscle histopathology can also enhance our understanding of disease pathogenesis.