This section discusses disorders of the nervous system, some of which can have far-reaching effects in all body systems. They include Alzheimer’s disease, amyotrophic lateral sclerosis, arteriovenous malformations, Bell’s palsy, cerebral palsy, complex regional pain syndrome, Creutzfeldt-Jakob disease, Guillain-Barré syndrome, headache, head trauma, Huntington’s disease, hydrocephalus, intracranial aneurysm, meningitis, multiple sclerosis, myasthenia gravis, Parkinson’s disease, Reye’s syndrome, seizure disorder, spinal cord trauma, and stroke.
Alzheimer’s disease is a degenerative disorder of the cerebral cortex, especially the frontal lobe, which accounts for more than half of all cases of dementia.
Although primarily found in the elderly population, 1% to 10% of cases have their onset in middle age.
Because this is a primary progressive dementia, the prognosis for a patient with this disease is poor.
The exact cause of Alzheimer’s disease is unknown. Factors that have been associated with its development include:
♦ neurochemical factors, such as deficiencies in the neurotransmitters acetylcholine, somatostatin, substance P, and norepinephrine
♦ environmental factors, such as repeated head trauma or exposure to aluminum or manganese
♦ genetic factors.
Genetic studies show that an autosomal dominant form of Alzheimer’s disease is associated with early onset and early death. A family history of Alzheimer’s disease and the presence of Down syndrome are two established risk factors.
The brain tissue of patients with Alzheimer’s disease has three distinct and characteristic features:
♦ neurofibrillatory tangles (fibrous proteins)
♦ beta-amyloid plaques (composed of degenerating axons and dendrites)
♦ granulovascular degeneration of neurons.
Additional structural changes include cortical atrophy, ventricular dilation, deposition of amyloid (a glycoprotein) around the cortical blood vessels, and reduced brain volume. Also found is a selective loss of cholinergic neurons in the pathways to the frontal lobes and hippocampus, areas that are important for memory and cognitive functions. Examination of the brain after death commonly reveals an atrophic brain, in many cases weighing less than 1,000 g (normal: 1,380 g). (See Abnormal cellular structures in Alzheimer’s disease, pages 266 and 267.)
Signs and symptoms
The typical signs and symptoms reflect neurologic abnormalities associated with pathophysiologic changes of the disease:
♦ gradual loss of recent and remote memory, loss of sense of smell, and flattening of affect and personality
♦ difficulty with learning new information
♦ deterioration in personal hygiene
♦ inability to concentrate
♦ increasing difficulty with abstraction and judgment
♦ impaired communication
♦ severe deterioration in memory, language, and motor function
♦ loss of coordination
♦ inability to write or speak
♦ personality changes
♦ tendency to wander
♦ nocturnal awakenings
♦ loss of eye contact and fearful look
♦ signs of anxiety, such as wringing of hands
♦ acute confusion, agitation, compulsiveness, or fearfulness when overwhelmed with anxiety
♦ disorientation and emotional lability
♦ progressive deterioration of physical and intellectual ability.
♦ Injury secondary to violent behavior or wandering
♦ Pneumonia and other infections
Alzheimer’s disease is diagnosed by exclusion— that is, by ruling out other disorders as the cause for the patient’s signs and symptoms. The only true way to confirm Alzheimer’s disease is by finding pathologic changes in the brain at autopsy. However, these diagnostic tests may be useful:
♦ Positron emission tomography shows changes in the metabolism of the cerebral cortex.
♦ Computed tomography scan shows evidence of early brain atrophy in excess of that which occurs in normal aging.
♦ Magnetic resonance imaging shows no lesion as the cause of the dementia.
♦ EEG shows evidence of slowed brain waves in the later stages of the disease.
♦ Cerebral blood flow studies show abnormalities in blood flow.
No cure or definitive treatment exists for Alzheimer’s disease. Therapy may include:
♦ a cholinesterase inhibitor, such as donepezil, rivastigmine, and galantamine, to prevent the breakdown of acetylcholine (involved in the brain’s memory and thinking skills)
♦ memantine, an uncompetitive low-to-moderate affinity N-methyl-D-aspartate receptor antagonist, to regulate the activity of glutamate (involved in the brain’s information processing, storing, and retrieval)
♦ a vitamin E supplement to help defend the brain against damage.
Many clinical trials are under way for the treatment of Alzheimer’s disease, including a vaccine that would stimulate the immune system to recognize and attack the beta-amyloid plaques that occur with the disease.
Overall care is focused on supporting the patient’s remaining abilities and compensating for those he has lost.
♦ Provide the patient with a safe environment. Encourage him to exercise, as ordered, to help maintain mobility.
♦ Establish an effective communication system with the patient and family to help them adjust to the patient’s altered cognitive abilities.
♦ Anxiety may cause the patient to become agitated or fearful. Intervene by helping him focus on another activity.
♦ Establish a routine for the patient to help him maintain a sense of control over his environment.
♦ Offer emotional support to the patient and family members. Behavior problems may be worsened by excess stimulation or change in established routine. Teach them about the disease, and refer them to social service and community resources for legal and financial advice and support.
AMYOTROPHIC LATERAL SCLEROSIS
Commonly called Lou Gehrig disease, after the New York Yankees first baseman that died of this disorder, amyotrophic lateral sclerosis (ALS) is the most common of the motoneuron diseases causing muscular atrophy. Other motoneuron diseases include progressive muscular atrophy and progressive bulbar palsy. Onset usually occurs between ages 40 and 70. A chronic, progressively debilitating disease, ALS may be fatal in less than 1 year or continue for 10 years or more, depending on the muscles affected. More than 30,000 Americans have ALS; about 5,000 new cases are diagnosed each year; and the disease affects three times as many men as women.
The exact cause of ALS is unknown, but 5% to 10% of cases have a genetic component—an autosomal dominant trait that affects men and women equally.
The first and most important breakthrough so far in ALS genetic research was the discovery of mutations in the SOD1 gene. This mutation is seen in about 20% of patients with familial ALS. However, this mutation is quite complex. Researchers understand how the gene functions, but the mutation is an acquisition of a toxic property, meaning that the gene gains a function, rather than losing its normal function. Researchers are perplexed about what that gain of function is, so genetic studies continue.
Several mechanisms have been considered, including:
♦ a slow-acting virus
♦ a nutritional deficiency related to a disturbance in enzyme metabolism
♦ a metabolic interference in nucleic acid production by the nerve fibers
♦ an autoimmune disorder that affects immune complexes in the renal glomerulus and basement membrane.
Precipitating factors for acute deterioration include any severe stress, such as a myocardial infarction, trauma, a viral infection, and physical exhaustion.
ALS progressively destroys the upper and lower motoneurons. It doesn’t affect cranial nerves III, IV, and VI and, therefore, some facial movements, such as blinking, persist. Intellectual and sensory functions aren’t affected.
Some believe that glutamate—the primary excitatory neurotransmitter of the CNS— accumulates to toxic levels at the synapses. The affected motor units are no longer innervated, and progressive degeneration of axons causes loss of myelin. Some nearby motor nerves may sprout axons in an attempt to maintain function but, ultimately, nonfunctional scar tissue replaces normal neuronal tissue.
Signs and symptoms
Typical signs and symptoms of ALS include:
♦ fasciculations accompanied by spasticity, atrophy, and weakness due to degeneration of the upper and lower motoneurons, and loss of functioning motor units, especially in the muscles of the forearms and the hands
♦ impaired speech, difficulty chewing and swallowing, choking, and excessive drooling from degeneration of cranial nerves V, IX, X, and XII
♦ difficulty breathing, especially if the brain stem is affected
♦ muscle atrophy due to loss of innervation.
Mental deterioration doesn’t usually occur, but patients may become depressed because of the disease. Progressive bulbar palsy may cause crying spells or inappropriate laughter.
♦ Respiratory tract infections
♦ Respiratory failure
Although no diagnostic tests are specific to ALS, the following may aid in the diagnosis:
♦ Electromyography shows abnormalities of electrical activity in involved muscles.
♦ Muscle biopsy shows atrophic fibers interspersed between normal fibers.
♦ Nerve conduction studies show normal results.
♦ Computed tomography scan and EEG show normal results and thus rule out multiple
sclerosis, spinal cord neoplasm, polyarteritis, syringomyelia, myasthenia gravis, progressive muscular dystrophy, and progressive stroke.
ALS has no cure. Treatment is supportive and may include:
♦ riluzole, a neuroprotector, to modulate glutamate activity and slow disease progression
♦ diazepam, dantrolene, or baclofen to decrease spasticity
♦ quinidine to relieve painful muscle cramps
♦ an anticholinergic, such as glycopyrolate or transdermal scopalamine, to decrease oral secretions
♦ thyrotropin-releasing hormone (I.V. or intrathecally) to temporarily improve motor function (successful only in some patients)
♦ mechanical ventilation to support pulmonary function
♦ respiratory, speech, and physical therapy to maintain function as much as possible
♦ psychological support to assist with coping with this progressive, fatal illness.
Remember that because mental status remains intact while progressive physical degeneration takes place, the patient acutely perceives every change. This threatens the patient’s relationships, career, income, muscle coordination, sexuality, and energy.
♦ Implement a rehabilitation program designed to maintain independence as long as possible.
♦ Elevate the head of the bed to relieve orthopnea.
♦ Help the patient obtain assistive equipment, such as a walker and a wheelchair. Arrange for a visiting nurse to oversee the patient’s status, provide support, and teach the family about the illness.
♦ Depending on the patient’s muscular capacity, assist with bathing, personal hygiene, and transfers from wheelchair to bed. Help establish a regular bowel and bladder routine.
♦ To help the patient handle an increased accumulation of secretions and dysphagia, teach him to suction himself. He should have a suction machine handy at home to reduce the fear of choking.
♦ To prevent skin breakdown, provide good skin care when the patient is bedridden. Turn him often, keep his skin clean and dry, and use pressure-reducing devices, such as an alternating air mattress.
♦ If the patient has trouble swallowing, give him soft, solid foods and position him upright during meals. Gastrostomy, percutaneous jejunostomy, or nasogastric tube feedings may be necessary if he can no longer swallow. Teach the family (or the patient if he’s still able to feed himself) how to administer gastrostomy feedings.
♦ Provide emotional support. A discussion of directives regarding health care decisions should be instituted before the patient becomes unable to communicate his wishes. Prepare the patient and family members for his eventual death, and encourage the start of the grieving process. Patients with ALS may benefit from a hospice program or the local ALS support group chapter.
Arteriovenous malformations (AVMs) are tangled masses of thin-walled, dilated blood vessels between arteries and veins that don’t connect by capillaries. AVMs are common in the brain, primarily in the posterior portion of the cerebral hemispheres. Abnormal channels between the arterial and venous system mix oxygenated and unoxygenated blood and, thereby, prevent adequate perfusion of brain tissue.
AVMs range in size from a few millimeters to large malformations extending from the cerebral cortex to the ventricles. Commonly, more than one AVM is present. Males and females are affected equally, and some evidence exists that AVMs are hereditary. Most AVMs are present at birth; however, symptoms typically don’t occur until the person is between ages 10 and 20.
♦ Acquired from penetrating injuries such as trauma
♦ Congenital, due to a hereditary defect
AVMs lack the typical structural characteristics of the blood vessels. The vessels of an AVM are thin; one or more arteries feed into the AVM, causing it to appear dilated and tortuous. The typically high-pressured arterial flow moves into the venous system through the connecting channels to increase venous pressure, engorging and dilating the venous structures. An aneurysm may develop. If the AVM is large enough, the shunting can deprive the surrounding tissue of adequate blood flow. Additionally, the thin-walled vessels may ooze small amounts of blood or actually rupture, causing hemorrhage into the brain or subarachnoid space.
Signs and symptoms
Typically, the patient experiences few, if any, signs and symptoms unless the AVM is large,
leaks, or ruptures. Possible signs and symptoms include:
♦ chronic mild headache and confusion from AVM dilation, vessel engorgement, and increased intracranial pressure (ICP)
♦ seizures secondary to compression of the surrounding tissues by the engorged vessels
♦ systolic bruit over carotid artery, mastoid process, or orbit, indicating turbulent blood flow
♦ focal neurologic deficits (depending on the location of the AVM) resulting from compression and diminished perfusion
♦ signs and symptoms of intracranial (intracerebral, subarachnoid, or subdural) hemorrhage, including sudden severe headache, seizures, confusion, lethargy, and meningeal irritation from bleeding into the brain tissue or subarachnoid space
♦ hydrocephalus from AVM extension into the ventricular lining.
Complications depend on the severity (location and size) of the AVM and may include:
♦ aneurysm development and subsequent rupture
♦ hemorrhage (intracerebral, subarachnoid, or subdural, depending on the location of the AVM)
♦ Cerebral arteriogram confirms the presence of AVMs and evaluates blood flow.
♦ Doppler ultrasonography of cerebrovascular system indicates abnormal, turbulent blood flow.
Treatment can be supportive, corrective, or both, and includes:
♦ support measures, including aneurysm precautions to prevent possible rupture
♦ surgery—block dissection, laser, or ligation— to repair the communicating channels and remove the feeding vessels
♦ embolization or stereotactic radiosurgery if surgery isn’t possible, to close the communicating channels and feeder vessels and thus reduce the blood flow to the AVM.
♦ Monitor vital signs frequently.
♦ Control hypertension, seizure activity, and other activity or stress that could elevate the patient’s systemic blood pressure by administering drug therapy as ordered, conducting ongoing neurologic assessments, and maintaining a quiet, therapeutic environment.
♦ If the AVM has ruptured, intervene to control elevated ICP and intracranial hemorrhage. The patient with a ruptured AVM may have intracerebral or intraventricular bleeding; bleeding into the subarachnoid, subdural, or epidural space; or bleeding into the brain itself, usually causing a concurrent elevation in ICP.
Bell’s palsy is a disease of the seventh cranial nerve (facial) that produces unilateral or bilateral facial weakness or paralysis, although bilateral involvement occurs in less than 10% of cases. The onset of symptoms is rapid. Although it affects all age-groups, Bell’s palsy occurs most commonly in people younger than age 60. In 80% to 90% of patients, it subsides spontaneously, with complete recovery in 1 to 8 weeks; however, recovery may be delayed in elderly patients. If recovery is partial, contractures may develop on the paralyzed side of the face. Bell’s palsy may recur on the same or opposite side of the face.
♦ Local trauma
Bell’s palsy reflects an inflammatory reaction around the seventh cranial nerve, usually at the internal auditory meatus where the nerve leaves bony tissue. This inflammatory reaction produces a conduction block that inhibits appropriate neural stimulation to the muscle by the motor fibers of the facial nerve, resulting in the characteristic unilateral or bilateral facial weakness.
Signs and symptoms
The signs and symptoms exhibited by the patient typically reflect interference in motor function associated with the seventh cranial nerve. Bell’s palsy usually produces unilateral facial weakness, occasionally with aching pain around the angle of the jaw or behind the ear. On the weak side, the mouth droops (causing the patient to drool saliva from the corner of his mouth), and taste perception is distorted over the affected anterior portion of the tongue. The forehead appears smooth, and the patient’s ability to close his eye on the weak side is markedly impaired. When he tries to close this eye, it rolls upward (Bell’s phenomenon) and shows excessive tearing. Although Bell’s phenomenon also occurs in people who are otherwise healthy, it isn’t apparent because the eyelids close completely and cover
this eye motion. In Bell’s palsy, incomplete eye closure makes this upward motion obvious. Other symptoms include loss of taste and ringing in the ear.
♦ Corneal abrasion
♦ Infection (masked by steroid use)
♦ Poor functional recovery
Diagnosis is based on clinical presentation: distorted facial appearance and inability to raise the eyebrow, close the eyelid, smile, show the teeth, or puff out the cheek on the affected side. After 10 days, electromyography helps predict the level of expected recovery by distinguishing temporary conduction defects from a pathologic interruption of nerve fibers.
Treatment consists of prednisone, an oral corticosteroid that reduces facial nerve edema and improves nerve conduction and blood flow. After the 14th day of prednisone therapy, electrotherapy may help prevent atrophy of facial muscles. Persistent paralysis may require surgical treatment.
Patient care includes observation for adverse reactions to prednisone, pain relief, and emotional support.
♦ During treatment with prednisone, watch for adverse reactions, especially GI distress and fluid retention. If GI distress is troublesome, a concomitant antacid usually provides relief. If the patient has diabetes, prednisone must be used with caution, which necessitates frequent monitoring of the serum glucose level.
♦ To reduce pain, apply moist heat to the affected side of the face, taking care not to burn the skin.
♦ To help maintain muscle tone, massage the patient’s face with a gentle upward motion two or three times daily for 5 to 10 minutes, or have him massage his face himself. When he’s ready for active exercises, teach him to exercise by grimacing in front of a mirror.
♦ Advise the patient to protect his eye by covering it with an eye patch, especially when outdoors and at night (when sleeping). Tell him to keep warm and avoid exposure to dust and wind. When exposure is unavoidable, instruct him to cover his face.
♦ To prevent excessive weight loss, help the patient cope with difficulty in eating and drinking. Instruct him to chew on the unaffected side of his mouth. Provide a soft, nutritionally balanced diet, eliminating hot foods and fluids. Arrange for privacy at mealtimes to reduce embarrassment. Give the patient frequent and complete mouth care, being particularly careful to remove residual food that collects between the cheeks and gums.
♦ Offer psychological support.
The most common cause of crippling in children, cerebral palsy (CP) is a group of neuromuscular disorders caused by prenatal, perinatal, or postnatal damage to the upper motoneurons. Although nonprogressive, these disorders may become more obvious as an affected infant grows.
The three major types of CP—spastic, athetoid, and ataxic—may occur alone or in combination. Motor impairment may be minimal (sometimes apparent only during physical activities, such as running) or severely disabling. Common associated defects are seizures, speech disorders, and mental retardation.
Cerebral palsy occurs in an estimated 2 to 3 per 1,000 live births in the United States every year. Incidence is highest in premature infants (anoxia plays the greatest role in contributing to cerebral palsy) and in those who are small for gestational age. Almost one-half of the children with CP are mentally retarded, approximately one-fourth have seizure disorders, and more than three-fourths have impaired speech. Additionally, many children with CP have dental abnormalities, vision and hearing defects, and reading disabilities.
CP is more common in whites than in other ethnicities. The prognosis varies. Treatment may make a near-normal life possible for children with mild impairment. Those with severe impairment require special services and schooling.
The exact cause of CP is unknown; however, conditions resulting in cerebral anoxia, hemorrhage, or other CNS damage are probably responsible. Potential causes vary with time of damage.
Prenatal causes include:
♦ abnormal placental attachment
♦ exposure to radiation
♦ maternal diabetes
♦ maternal infection (especially rubella)
Perinatal and birth factors may include:
♦ abruptio placentae
♦ breech presentation
♦ depressed maternal vital signs from general or spinal anesthesia
♦ forceps delivery
♦ infection or trauma during infancy
♦ multiple births (especially infants born last)
♦ placenta previa
♦ premature birth
♦ prolapsed cord with delay in blood delivery to the head
♦ prolonged or unusually rapid labor. Postnatal causes include:
♦ brain infection or tumor
♦ cerebral circulatory anomalies causing blood vessel rupture
♦ head trauma
♦ kernicterus resulting from erythroblastosis fetalis
♦ prolonged anoxia
♦ systemic disease resulting in cerebral thrombosis or embolus.
In the early stages of brain development, a lesion or abnormality causes structural and functional defects that in turn cause impaired motor function or cognition. Even though the defects are present at birth, problems may not be apparent until months later, when the axons have become myelinated and the basal ganglia are mature.
Signs and symptoms
Shortly after birth, the infant with CP may exhibit some typical signs and symptoms, including:
♦ excessive lethargy or irritability
♦ high-pitched cry
♦ poor head control
♦ weak sucking reflex.
Additional physical findings that may suggest CP results from impaired development or damage to the motor areas of the brain and may include:
♦ delayed motor development (inability to meet major developmental milestones)
♦ abnormal head circumference, typically smaller than normal for age (because the head grows as the brain grows)
♦ abnormal postures, such as straightening the legs when the patient is lying on his back, toes down; holding the head higher than normal when in a prone position due to arching of the back
♦ abnormal reflexes (neonatal reflexes lasting longer than expected, extreme reflexes, or clonus)
♦ abnormal muscle tone and performance (scooting on the back to crawl, toe-first walking).
Each type of CP typically produces a distinctive set of clinical features, although some children display a mixed form of the disease. (See Assessing signs of cerebral palsy, page 272
Complications depend on the type of CP and the severity of the involvement. Possible complications include:
♦ skin breakdown and ulcer formation
♦ muscle atrophy
♦ seizure disorders
♦ speech, hearing, and vision problems
♦ language and perceptual deficits
♦ mental retardation
♦ dental problems
♦ respiratory difficulties, including aspiration from poor gag and swallowing reflexes.
No diagnostic tests are specific to CP. However, neurologic screening will exclude other possible conditions, such as infection, spina bifida, or muscular dystrophy. Diagnostic tests that may be performed include:
♦ Developmental screening reveals delay in achieving milestones.
♦ Vision and hearing screening demonstrates degree of impairment.
♦ EEG identifies the source of seizure activity.
Suspect CP whenever an infant exhibits an alteration in neurologic function during clinical observation. This may include difficulty in sucking or moving voluntarily. Infants particularly at risk include those with a low birth weight, low Apgar score at 5 minutes, seizures, and metabolic disturbances. However, all infants should have a screening test for CP as a regular part of their 6-month checkup.
CP can’t be cured, but treatment can help affected children reach their full potential within the limits set by this disorder. Such treatment requires a comprehensive and cooperative effort, involving physicians, nurses, teachers, psychologists, the child’s family, and occupational, physical, and speech therapists. Home care is usually possible. Treatment typically includes:
♦ braces, casts, or splints and special appliances, such as adapted eating utensils and a low toilet seat with arms, to help the child perform activities of daily living independently
♦ an artificial urinary sphincter for the incontinent child
♦ range-of-motion exercises to minimize contractures
♦ an anticonvulsant to control seizures
♦ a muscle relaxant (sometimes) to reduce spasticity
♦ surgery to decrease spasticity or correct contractures
♦ muscle transfer or tendon lengthening surgery to improve function of joints
♦ rehabilitation, including occupational, physical, and speech therapy, to maintain or improve functional abilities.
A child with CP may be hospitalized for orthopedic surgery or for treatment of other complications.
♦ Speak slowly and distinctly. Encourage the child to ask for items he wants. Listen patiently and don’t rush him.
♦ Plan a high-calorie diet that’s adequate to meet the child’s high energy needs.
♦ During meals, maintain a quiet, unhurried atmosphere with as few distractions as possible. The child should be encouraged to feed himself and may need special utensils and a chair with a solid footrest. Teach him to place food far back in his mouth to facilitate swallowing.
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