Sarah Andrus Gaines
AMYOTROPHIC LATERAL SCLEROSIS
EPIDEMIOLOGY
The typical time of onset for amyotrophic lateral sclerosis (ALS) is over age 50 years.
PATHOPHYSIOLOGY
ALS is caused by upper and lower motor neuron degeneration without other central nervous dysfunction.
CLINICAL FEATURES
Upper motor neuron dysfunction causes limb spastic-ity, hyperreflexia, and emotional lability.
Lower neuron dysfunction causes limb muscle weakness, atrophy, fasciculations, dysarthria, dysphagia, and difficulty in mastication.
Symptoms are often asymmetric.
Patients may initially have cervical or back pain consistent with an acute compressive radiculopathy.
Respiratory muscle weakness causes progressive respiratory depression.
DIAGNOSIS AND DIFFERENTIAL
The diagnosis is clinical and is often previously established.
Electromyography (EMG) is the most useful test.
Other illnesses that should be considered include myasthenia gravis (MG), diabetes, thyroid dysfunction, vitamin B12 deficiency, lead toxicity, vasculitis, and central nervous system (CNS) or spinal cord tumors.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Emergency care is required for acute respiratory failure, aspiration pneumonia, choking episodes, or trauma from falls.
The treatment goal is to optimize pulmonary function through the use of nebulizer treatments, steroids, antibiotics, or endotracheal intubation.
Admit patients with impending respiratory failure, pneumonia, inability to handle secretions, and worsening disease process that may require long-term care.
MYASTHENIA GRAVIS
EPIDEMIOLOGY
Peak age of onset for myasthenia gravis (MG) is in the second or third decade of life for females and in the fifth or eighth decade for males.
PATHOPHYSIOLOGY
MG is an autoimmune disease caused by antibody destruction of the acetylcholine receptors at the neuromuscular junction, which results in muscle weakness.
The thymus is abnormal in 75% of patients and thymectomy resolves or improves symptoms in most patients, especially in those with a thymoma.
CLINICAL FEATURES
Most MG patients have generalized weakness, specifically of the proximal extremities, neck extensors, and facial or bulbar muscles. There is usually no deficit in sensory, reflex, and cerebellar function.
Ptosis and diplopia are the most common symptoms. Symptoms usually worsen as the day progresses or with muscle use (eg, prolonged chewing or reading) and improve with rest. Ten percent of patients have ocular muscle weakness only.
Myasthenic crisis is a life-threatening condition involving extreme weakness of the respiratory muscles that may progress to respiratory failure.
DIAGNOSIS AND DIFFERENTIAL
The diagnosis is confirmed through administration of edrophonium (Tensilon test), electromyogram, and serum testing for acetylcholine receptor antibodies.
The differential diagnosis includes Lambert-Eaton syndrome, drug-induced disorders (eg, penicilla-mines, aminoglycosides, and procainamide), ALS, botulism, thyroid disorders, and other CNS disorders (eg, intracranial mass lesions, stroke).
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Implement supplemental oxygen and aggressive airway management with myasthénie crisis.
Avoid depolarizing and nondepolarizing paralytic agents. Etomidate, fentanyl, or propofol can be used.
If the Tensilon test is positive, then administer pyri-dostigmine (60-90 milligrams PO or 2-3 milligrams IV every 4 hours), with an onset of 15 to 30 minutes and duration for 3 to 5 hours. An alternative is neostigmine (0.5 milligram IV), which will be effective within 30 minutes and last for 4 hours.
Steroids, immunosuppressive medications, and plas-mapheresis may be used in consultation with a neurologist.
Several drugs should be used with caution in patients with MG (Table 149-1).
Consult a neurologist for disposition and admission.
TABLE 149-1 Drugs That Should Be Avoided in Myasthenia Gravis
MULTIPLE SCLEROSIS
EPIDEMIOLOGY
Three clinical courses are seen in multiple sclerosis (MS): relapsing and remitting (up to 90% of cases); relapsing and progressive; or chronically progressive.
Peak age of onset is the third decade of life. Females are two to three times more likely to contract MS than are males.
PATHOPHYSIOLOGY
Although the etiology of MS is unknown, it involves multifocal areas of CNS demyelination, causing motor, sensory, visual, and cerebellar dysfunction.
CLINICAL FEATURES
Deficits associated with MS are described as a heaviness, weakness, stiffness, or numbness of an extremity or clumsiness. Lower extremity symptoms are usually more severe.
Lhermitte’s sign is an electric shock-like sensation, a vibration, or dysesthetic pain going down into the arms or legs from neck flexion.
Physical examination may reveal decreased strength, increased tone, hyperreflexia, clonus, decreased proprioception, reduced pain and temperature, and a positive Babinski reflex.
Increases in body temperature, associated with exercise, hot baths, or fever, may worsen symptoms.
Optic neuritis, usually causing unilateral loss of central vision, is the first presenting symptom in up to 30% of cases and may cause an afferent papillary defect (Marcus Gunn pupil).
Acute bilateral internuclear ophthalmoplegia (INO), which causes abnormal adduction and horizontal nystagmus, is highly suggestive of MS.
Retrobulbar or extraocular muscle pain usually precedes vision loss. Fundoscopy is usually normal, but the disc may appear pale.
Rarely, acute transverse myelitis may occur. Cerebellar lesions may cause intention tremor or ataxia. Brain stem lesions may cause vertigo.
Cognitive and emotional problems are common (eg, mood disorders or dementia).
Dysautonomia causes vesicourethral, gastrointestinal tract, and sexual dysfunction.
DIAGNOSIS AND DIFFERENTIAL
The diagnosis of MS is clinical and is suggested by two or more episodes, lasting days to weeks, causing dysfunction that implicates different sites in the white matter.
MRI of the brain may demonstrate various abnormalities, including discrete lesions in the supratentorial white matter or periventricular areas.
Cerebrospinal fluid (CSF) protein and gamma-globulin levels are often elevated.
The differential diagnosis includes systemic lupus erythematosus, Lyme disease, neurosyphilis, and HIV disease.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Treat severe motor or cerebellar dysfunction with steroids: high-dose pulsed intravenous methylprednisolone (250 milligrams IV every 6 hours), followed by a PO prednisone taper.
Fever must be reduced to minimize symptoms. Perform a careful search for a source of infection. Evaluate for acute UTI or pyelonephritis; postvoid residuals >100 mL require intermittent catheterization.
Respiratory infections and distress must be aggressively managed.
Admission is required for those at risk for further complications, respiratory compromise, depression with suicidal ideation, and those requiring IV antibiotics or steroids.
LAMBERT-EATON MYASTHENIC SYNDROME
Lambert-Eaton myasthenie syndrome is an autoimmune disorder that causes fluctuating proximal limb muscle weakness and fatigue.
Lambert-Eaton syndrome is seen mostly in older men with lung cancer.
Strength is improved with sustained activity.
Patients complain of myalgias, stiffness, paresthesias, metallic tastes, and autonomic symptoms (eg, impotence and dry mouth). Eye movements are unaffected.
The EMG is abnormal and serum tests are specific for antibodies to voltage-gated calcium channels.
Treatment of the underlying neoplasm greatly improves symptoms.
Pyridostigmine and immunosuppressive drugs may reduce symptom severity.
PARKINSON’S DISEASE
EPIDEMIOLOGY
The average age of onset for Parkinson’s disease (PD) is 55 to 60 years of age.
PATHOPHYSIOLOGY
The etiology of PD is unknown, but patients have reduced functional dopaminergic receptors in the substantia nigra.
CLINICAL FEATURES
PD presents with four classic signs (mnemonic “TRAP”): resting tremor, cogwheel rigidity, akinesia or bradykinesia, and impaired posture and equilibrium.
Other signs include facial and postural changes, voice and speech abnormalities, depression, and muscle fatigue.
Initially, most complain of a unilateral resting arm tremor, described as pill rolling, or a general feeling of stiffness or slowness, which may have been present for years.
DIAGNOSIS AND DIFFERENTIAL
The diagnosis is clinical and is most often previously established. No laboratory test or neuroimaging study is pathognomonic.
Parkinsonism can result from street drugs, toxins, neuroleptic drugs, hydrocephalus, head trauma, and other rare neurologic disorders.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
PD patients may be on medications that increase central dopamine (eg, levodopa, carbidopa, and amantadine), anticholinergics (eg, benztropine), and dopamine receptor agonists (eg, bromocriptine).
Medication toxicity includes psychiatric or sleep disturbances, cardiac dysrhythmias, orthostatic hypotension, dyskinesias, and dystonia.
With significant motor or psychiatric disturbances (eg, hallucinations or frank psychosis) or decreased drug efficacy, a “drug holiday” for 1 week should be initiated in consultation with a neurologist.
POLIOMYELITIS AND POSTPOLIO SYNDROME
EPIDEMIOLOGY
Poliomyelitis leads to paralysis in less than 5% of infected patients.
PATHOPHYSIOLOGY
Poliomyelitis is caused by an enterovirus that causes paralysis via motor neuron destruction and muscle denervation and atrophy.
In developed countries, transmission is oral to oral; however, transmission is fecal to oral in developing countries.
CLINICAL FEATURES
Most symptomatic patients have only a mild viral syndrome and no paralysis. Symptoms include fever, malaise, headache, sore throat, and gastrointestinal symptoms.
Spinal polio results in asymmetric proximal limb weakness and flaccidity, absent tendon reflexes, and fasciculation. Maximal paralysis occurs within 5 days.
Other sequelae include bulbar polio (speech and swallowing dysfunction) and encephalitis.
Postpolio syndrome is the recurrence of motor symptoms after a latent period of several decades.
Symptoms of postpolio syndrome may include muscle fatigue, joint pain, or weakness of new and previously affected muscle groups. Patients may have new bulbar, respiratory, or sleep difficulties.
DIAGNOSIS AND DIFFERENTIAL
Consider the diagnosis of polio in patients with an acute febrile illness, aseptic meningitis, and asymmetric flaccid paralysis.
CSF may reveal a pleocytosis (mostly neutrophils) and positive cultures for poliovirus.
Throat and rectal swabs are higher yield tests than CSF.
The diagnosis of postpolio syndrome is based on a prior history of paralytic polio with recovery and new symptoms.
The differential diagnosis includes Guillain–Barré syndrome, peripheral neuropathies (eg, mononucleosis, Lyme disease, and porphyria), abnormal electrolyte levels, toxins, inflammatory myopathies, and other viruses (eg, coxsackievirus, mumps, echovirus, and various enteroviruses).
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Treatment is supportive.
Lamotrigine may improve quality of life.
Disposition should be made in consultation with a neurologist.
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 167, “Chronic Neurologic Disorders,” by Edward R Sloan, Daniel A. Handel, and Sarah Andrus Gaines.