Weakness due to certain causes is common enough in the pediatric ED population to justify specific discussion.
Also known as acute inflammatory demyelinating polyradiculoneuropathy (AIDP), Guillain–Barré syndrome occurs in both children and adults. It is more common in the adult patient population. The pathogenesis is unknown, but it is thought to result from an immune response to an antecedent viral infection that triggers demyelination of nerve roots and peripheral nerves. Campylobacter infection is the most common preceding illness, occurring in 30% of cases. Other infections include cytomegalovirus, EBV, herpes simplex, Hemophilus influenzae, Mycoplasma pneumoniae, hepatitis A and B, enterovirus, and Chlamydophila pneumoniae.8 The form of GBS associated with campylobacter also results in acute axonal degeneration.8 The syndrome often starts with paresthesias in the toes and fingers, and nonspecific muscular pain, most often in the thighs. The pain is followed by weakness, which is most often symmetric and distal, and results in trouble walking.8 Weakness progresses upward and, in some cases, results in total paralysis within 24 hours. Cranial nerve involvement is common, with bilateral facial weakness. Deep tendon reflexes are usually absent, but plantar responses remain downgoing. Autonomic involvement can produce labile changes in blood pressure and bowel and bladder incontinence. The degree of weakness and the rate of progression of disease vary considerably. Laboratory findings are generally not helpful, although spinal fluid analysis may reveal a high protein (>45 mg/dL) and usually has fewer than 10 white blood cells.8
Diagnostic criteria exist which combine clinical, laboratory, and electrophysiologic features. Electrophysiologic studies demonstrate motor conduction bock, and slowed nerve conduction velocities.9
The basic treatment for Guillain–Barré syndrome is supportive care. Patients with vital capacity ½ normal for age usually require ventilatory support. Approximately 20% of patients require mechanical ventilation, which is associated with a poorer prognosis.10 Attention is given to fluid and electrolyte balance, heart rate, cardiac rhythm, blood pressure, and nutritional needs. Steroids and other immunosuppressive agents are of no value. Intravenous immunoglobulin (IVIG) has been shown to shorten the course, as have limited studies on plasmsapheresis.10 The American Academy of Neurology states that IVIG or plasmapheresis are treatment options for children with severe GBS.10,11
There are several variants of GBS/AIDP in children, including Miller–Fisher syndrome, which is characterized by ophthalmoplegia, hyporeflexia, and ataxia. Acute motor and sensory axonal neuropathy (ASMAN) and acute motor axonal neuropathy (AMAN) occur mainly in China, and are associated with a preceeding campylobacter infection.8 The latter two forms consist of acute ascending weakness, hyporelexia, and elevated CSF protein, with ASMAN having a more prolonged course and limited recovery.8,9
Transverse myelitis is a syndrome characterized by acute dysfunction at a level of the spinal cord. It can occur as an isolated phenomenon or as part of another illness, such as multiple sclerosis. As such, it represents a syndrome rather than a distinct entity. The onset can be insidious, but is usually over 24 to 48 hours. Patients may initially complain of paresthesias and weakness of the lower extremities. Those with the rapid form often complain of back pain. Progressive weakness, paraplegia, and urinary retention usually result, and a sensory level may develop, most commonly in the thoracic area. Flaccid paralysis and decreased reflexes are characteristic early in the process but are later followed by increased muscle tone.12
For a patient with signs of a rapidly advancing spinal cord lesion, it is imperative to exclude a treatable mass lesion that could be compressing the cord, such as an epidural abscess or hemorrhage. This is usually done by MRI, which shows a gladolinium signal abnormality over the spinal cord, and may show swelling on weighted T2 images. Most patients with transverse myelitis recover some function. Corticosteroids may benefit some patients.12
Tick paralysis is caused by a neurotoxin from the Rocky Mountain wood tick (Dermacentor andersoni) or the Eastern dog tick (Dermacentor variabilis). The tick produces a neurotoxin that prevents liberation of acetylcholine at neuromuscular junctions. Several days after the tick attaches, the patient begins to experience paresthesias, fatigue, and weakness, which progresses to ataxia and difficulty walking. Deep tendon reflexes are absent. In some cases, there can be facial and bulbar muscle involvement, or unilateral paralysis. If the tick is not removed, flaccid paralysis and death can result. Removal of the tick is generally curative within a few hours.6,13
Infection with C. botulinum can produce three neurologic diseases. Ultimately, symptoms result from a toxin generated from spores of the bacteria that inhibits calcium-dependent release of acetylcholine at the prejunction of terminal nerve fibers.14
Food-borne botulism results from ingestion of food containing the toxin. Diarrhea and vomiting are followed by neurologic symptoms, often secondary to cranial nerve dysfunction. Blurred vision, dysarthria, and diplopia can occur and can be followed by weakness of the extremities. Mucous membranes of the mouth and pharynx may be dry. Deep tendon reflexes may be weak or absent. Antitoxin may be effective in food-borne botulism.14
Wound botulism results from infection of a contaminated wound, 4 to 14 days after the wound is infected. Clinically, it is usually indistinguishable from food-borne botulism. Treatment includes wound debridement and antibiotic therapy. Antitoxin may also be useful.14
Infantile botulism is caused by colonization of the intestinal tract by spores of C. botulinum, which releases toxin that is systemically absorbed. It has been related to the ingestion of contaminated honey, but many cases are linked to nearby construction projects, as soil harbors the spores. The affected age group is 6 weeks to 9 months. A prominent manifestation is constipation. The infant develops a descending paralysis, with ptosis, difficulty in sucking and swallowing, and reduced facial expression and can become hypotonic. Symmetrical paralysis can develop with occasional respiratory involvement.14
Diagnosis is by isolating the toxin in the infant's stool. Electromyography is also useful. The management of infant botulism is supportive and may require mechanical ventilation. Treatment with antitoxin and antibiotics does not seem to be of benefit.
The term myasthenia gravis comprises a group of autoimmune diseases characterized by easy fatigability. It is associated with anti-acetylcholine receptor antibodies resulting in decreased transmission of nerve impulses across the neuromuscular junction. It is the most common disorder of the myoneural junction in children.14 In children, the striated muscles innervated by the cranial nerves are particularly affected. The diagnosis is usually established by demonstrating improvement in muscle strength after administration of the anticholinesterase edrophonium (Tensilon). The two basic categories of myasthenia gravis in the pediatric population are as follows:
- Neonatal transient myasthenia
- Juvenile myasthenia gravis
Neonatal transient myasthenia gravis occurs in infants born to mothers with the disease, and is caused by maternal anti-acetylcholine receptor antibodies that cross the placenta. It affects 10% to 15% of infants whose mothers have myasthenia gravis. The infant may have a weak cry or suck, ptosis, generalized weakness, hypotonia, and respiratory distress. It presents in the first few hours of life, but may be delayed up to 3 days. Treatment is with neostigmine or pyridostigmine. The disease usually improves in 4 to 6 weeks, but may last for months.14
Juvenile myasthenia gravis is similar to that seen in adults. It commonly has its onset at around 10 years of age, and is more common in females. Ptosis, ophthalmoplegia, and weakness of other facial muscles are commonly present. This results in difficulty in chewing, dysarthria, and dysphagia. Bulbar weakness develops in 75% of patients.14 Symmetrical limb weakness is usually present, and affects the proximal muscles more than the distal muscles. The disease tends to become worse throughout the day, but can also worsen with stress or exertion. Symptoms and signs can be scored on a validated myasthenia scoring system and activities of daily living scale. Both remissions and exacerbations are common. To diagnose myasthenia gravis, the edrophomium (tensilon) test is helpful, but electrophysiologic testing and the presence of serum antiacetylcholine receptor antibodies are more specific.14 The primary treatment is with anticholinesterase agents. In refractory or severe cases, immunosuppressive agents, corticosteroids, IVIG, plasmapheresis, or thymectomy may be necessary. Erythromycin, tetracycline, aminoglycoside antibiotics, anesthetic drugs, neuromuscular blockers, and muscle relaxants therapy can exacerbate symptoms and should be avoided.14,15
Occasionally, exacerbations of symptoms can occur that result in profound weakness, difficulty in swallowing secretions, and respiratory insufficiency. It is often precipitated by infection, surgery, or decreasing immunosuppressive drugs. It can also be exacerbated by the use of antibiotic therapy, especially aminoglycosides as well as antiarrhythmics, and ophthalmologic medications.15 If a myasthenic crisis is suspected, the patient is admitted to an intensive care unit where respiratory status can be monitored, and elective intubation can occur if needed.
Patients with myasthenia gravis can also suffer from overdose of anticholinesterase medications, which can provoke a cholinergic crisis. Unfortunately, the symptoms of cholinergic excess are similar to those of a myasthenic crisis. In both, increasing weakness is the predominant finding.16 Patients suffering a cholinergic crisis may also have associated vomiting, diarrhea, and hypersalivation. In patients with obvious severe cholinergic excess, atropine or glycopyrrolate may be useful in drying airway secretions.16 However, in most cases, it will be difficult to distinguish between a cholinergic crisis and an exacerbation of myasthenia, and hospital admission and close observation are indicated.
Bell's palsy is a condition that results in unilateral facial weakness. In severe cases, there can be total paralysis of the facial muscles. It is thought to result from swelling and edema of cranial nerve VII, the facial nerve, as it traverses the facial canal within the temporal bone. As such, it is a peripheral neuropathy, and the distribution of the weakness reflects the territory innervated by the facial nerve. The nerve has motor, sensory, and autonomic functions and, in addition to supplying the muscles of the face, it innervates the lacrimal and salivary glands, and the anterior two-thirds of the tongue. In most cases, Bell's palsy is idiopathic. Certain conditions are associated with unilateral facial weakness, including viral infections, otitis media, Lyme disease, and temporal bone trauma.17
Symptoms may begin with ear pain, which is followed by the development of facial weakness, characterized by a drooping mouth and inability to close the eye on the affected side. In some cases, lacrimation and taste are impaired. Inability to close the mouth can make eating and drinking difficult.17
The lesion is identified as a peripheral neuropathy, as opposed to a lesion of the central nervous system, by the fact that Bell's palsy affects the muscles of the forehead on the side of the lesion. In a lesion of the central nervous system, the forehead is spared, because it receives innervation from both sides of the brain. A lesion in a cerebral hemisphere will cause weakness confined to the lower part of the face.17
Laboratory studies are not necessary in uncomplicated cases. If the child has been in a Lyme disease endemic region, testing may be useful. If mastoiditis is suspected, a CT scan is helpful.17
The prognosis of Bell's palsy is generally good, with recovery usually beginning in 2 to 4 weeks, but may take 6 to 14 weeks to resolve fully. Steroid therapy may be beneficial if started early in the course of illness, and is given for 1 week. Treatment includes lubricating solutions for the eye on the affected side to maintain moisture of the cornea.17 Patients with inability to close the eye may require patching. In young children, ophthalmologic consultation may be advisable.
Myopathies are diseases that affect skeletal muscle. They are relatively uncommon in children, and, in most cases, a child affected with a myopathy will present to the ED with a known diagnosis. Many myopathies are congenital.
Muscular dystrophies are disorders associated with progressive degeneration of muscle. The many different varieties of muscular dystrophy vary in their mode of inheritance, age of onset, muscles involved, progression of disease, and ultimate outcome. The most common is Duchenne muscular dystrophy, usually an X-linked recessive disorder resulting in the absence of the protein dystrophin.7 Clinical manifestations usually become apparent before age 4, when patients begin to develop weakness of the hip girdle and shoulder muscles. Patients may have difficulty standing and characteristically rise from all fours by placing their hands on the thighs and pushing up (Gower's sign). There is hypertrophy of the calf muscles. The disease is characterized by a progressive loss of muscle strength. Lordosis and kyphoscoliosis develop as the disease progresses. Pulmonary involvement due to weakness of the diaphragmatic and intercostal muscles results in impaired lung function. While the use of mechanical ventilators has increased survival, pulmonary infections and respiratory insufficiency are the main causes of mortality.7 Cardiac insufficiency and cardiomyopathy of varying degrees occur in the majority of children. In adolescence, cardiac fibrosis can lead to left ventricular dysfunction, arrhythmias, heart failure, and sudden death.7 The use of daily prednisone is the only treatment. It has been shown to improve ambulation, reduce contractures, and preserve respiratory function.7
Periodic paralysis is an example of metabolic myopathies that result in muscle weakness. The disorders are usually inherited, but can also be acquired. The inherited forms are autosomal dominant. There are several varieties, which include the channelopathies affecting the potassium, sodium, and calcium channels in skeletal muscle.18
Hypokalemic periodic paralysis is actually one of five channelopathies that is due to a disorder in the skeletal muscle sodium, calcium, or potassium channel gene, or is associated with thyroid disease, or cardiac dysrhythmias (Anderson syndrome).18 Most episodes of hypokalemic periodic paralysis have their onset during the first or second decade of life. They are often precipitated by excitement, cold, rest after exercise, or ingestion of high-carbohydrate meals, but can also be associated with hyperthyroidism, excessive insulin, renal tubular acidosis, or laxative abuse. Paralysis usually begins proximally and spreads distally. The patient may be areflexic. The episode can last for 6 to 12 hours.6,18 Attacks tend to decrease with age. Serum potassium during an attack is usually decreased compared with a baseline value. Treatment with oral potassium during an attack may be helpful; intravenous potassium may be needed for severe attacks. Long-term therapy with a low-sodium and low-carbohydrate diet, avoidance of exposure to cold, and potassium supplement can be beneficial. Acetazolamide taken daily may reduce the number of attacks.18
The three forms of hyperkalemic periodic paralysis are also autosomal dominant conditions associated with intermittent attacks beginning in the first decade of life. Attacks can be provoked by cold exposure, periods of rest following heavy exertion, and oral potassium loads. Weakness can develop rapidly, and lasts a shorter period of time than that of hypokalemic periodic paralysis.6,18 Myalgia develops at the outset, and is followed by proximal then distal muscle weakness. Some patients develop myotonia during attacks.18 The serum potassium is elevated above baseline values, although the degree of hyperkalemia varies. Treatment with oral glucose may speed recovery. Most attacks respond to treatment with glucose and insulin. In severe cases, intravenous calcium gluconate is necessary. In such cases, nebulized albuterol is also helpful.18 Preventive treatment includes avoidance of exposure to cold and avoidance of fasting. Eating frequent high-carbohydrate meals may be helpful, as is treatment with hydrochlorothiazide or acetazolamide.18
Viral myositis is a common cause of weakness in children. It may follow influenza or other viral illnesses. Fever and other constitutional symptoms are accompanied by myalgias. Affected muscles are tender to touch, and may be boggy. The creatine kinase is often elevated. The urine should be examined for myoglobinuria, as this may indicate rhabdomyolysis, a serious complication. Most cases are self-limited, and are treated with bed rest, hydration, and NSAIDs or acetaminophen.3,19,20
This is caused by ingestion of inadequately cooked meat (usually pork) containing the parasitic nematode Trichinella spiralis. While most infections are asymptomatic, invasion of the muscles results in an acute systemic infection characterized by fever, headache, generalized myalgias, abdominal pain, and weakness 2 to 12 days after ingestion of the meat. Myalgias and weakness are more profound in the third week of infection. Other complications include myocarditis and CNS infection. Diagnosis is by serum antibody levels, which peak 3 to 4 weeks after infection. Many patients also have elevated creatine kinase and eosinophilic leuckocytosis. Treatment includes thiabendazole and prednisone, to prevent a Herxheimer-like reaction after degeneration of the larvae.19
This is an abscess or multifocal abscesses within the muscle. While it is more likely to occur in an immunocompromised host, it has been occurring more frequently with the emergence of methicillin resistant Staphylococcus aureus (MRSA). Other bacterial causes include streptococci, Escherichia coli, Yersinia, and Legionella.3,19 The child presents with fever, muscle pain, and tenderness. The abscess can be seen on ultrasound, CT scan, or MRI. Treatment involves appropriate intravenous antibiotics.3,19
Although polio is rare, there are still sporadic cases. The virus attacks the anterior horn cells, resulting in asymmetrical weakness. The child may develop nuchal rigidity, muscle tightness, and fever. In infants younger than 1 year, spasm of the back muscles is also prominent. Bulbar involvement results in respiratory compromise, circulatory and autonomic instability, and mandates ventilatory support. The cerebrospinal fluid has pleocytosis with mononuclear cells, and a normal or slightly elevated protein.5
This RNA virus has rapidly become endemic in the United States, due to its vector of the Culex mosquito. Although most infections are asymptomatic, those that are symptomatic are more severe in the elderly; there have been cases in children as well. Symptoms include fever, headache, nausea, vomiting, and meningoencephalitis. Weakness may develop, and may be asymmetric or involve the face. Diagnosis is by demonstrating a rising IgM titer, or by reverse transcriptase PCR.5