Huntington’s Disease

HUNTINGTON’S DISEASE

Huntington’s disease is a chronic, progressive, hereditary disease of the nervous system that results in progressive involuntary cho-reiform movement and dementia. It affects men and women of all races. Because it is transmitted as an autosomal dominant ge-netic disorder, each child of a parent with Huntington’s disease has a 50% risk of inheriting the illness (Bradley et al., 2000).

Pathophysiology

The basic pathology involves premature death of cells in the stria-tum (caudate and putamen) of the basal ganglia, the region deep within the brain involved in the control of movement. There is also loss of cells in the cortex, the region of the brain associated with thinking, memory, perception, and judgment, and in the cerebellum, the area that coordinates voluntary muscle activity. 

Researchers now believe that a building block for protein called glutamine abnormally collects in the cell nucleus, causing cell death. The reason that the protein destroys only certain brain cells is unknown. The cells’ destruction results in a lack of the neurotransmitters gamma-aminobutyric acid (GABA) and acetyl-choline, which inhibit nerve action (Bradley et al., 2000). Onset usually occurs between the ages of 35 and 45 years, although about 10% of patients are children. The disease progresses slowly. Despite a ravenous appetite, patients usually become emaciated and exhausted. Patients succumb in 10 to 20 years to heart failure, pneumonia, or infection, or as a result of a fall or choking.

Clinical Manifestations

The most prominent clinical features of the disease are abnormal involuntary movements (chorea), intellectual decline, and, often, emotional disturbance. As the disease progresses, a constant writhing, twisting, uncontrollable movement may involve the entire body. These motions are devoid of purpose or rhythm, although patients may try to turn them into purposeful move-ment. All of the body musculature is involved. Facial movements produce tics and grimaces. Speech is affected, becoming slurred, hesitant, often explosive, and eventually unintelligible. Chewing and swallowing are difficult, and there is a constant danger of choking and aspiration. Choreiform movements persist but di-minish during sleep.

As with speech, the gait becomes disorganized to the point that ambulation eventually is impossible. Although independent ambulation should be encouraged for as long as possible, a wheel-chair usually becomes necessary. Eventually, the patient is con-fined to bed when the chorea interferes with walking, sitting, and all other activities. Bladder and bowel control is lost.

Cognitive function is usually affected, with dementia usually occurring. Initially, the patient generally is aware that the disease is responsible for the myriad dysfunctions that are occurring. The mental and emotional changes that occur may be more devastat-ing to the patient and family than the abnormal movements. Per-sonality changes may result in nervous, irritable, or impatient behaviors. In the early stages, patients are particularly subject to uncontrollable fits of anger, profound, often suicidal depression, apathy, anxiety, psychosis, or euphoria (Hofmann, 1999). Judg-ment and memory are impaired, and dementia eventually ensues. Hallucinations, delusions, and paranoid thinking may precede the appearance of disjointed movements. Emotional symptoms often become less acute as the disease progresses.

Assessment and Diagnostic Findings

The diagnosis is made based on the clinical presentation of char-acteristic symptoms, a positive family history, and exclusion of other causes. Imaging studies, such as CT and MRI, may show atrophy of the caudate nuclei once the disease is well established (Bradley et al., 2000).

A genetic marker for Huntington’s has been identified through the use of recombinant DNA technology. As a result, re-searchers can now identify presymptomatic individuals who will develop this disease. Although this presymptomatic test can re-move the uncertainty, it offers no hope of cure or even specific prediction of the timing of its onset. Researchers continue to study the genetic causes that lead to the death of brain cells (Bradley et al., 2000).

Management

Although no treatment halts or reverses the underlying process, several methods of management have fairly good palliative results (Bradley et al., 2000; Sawle, 1999). Thiothixene hydrochloride (Navane) and haloperidol decanoate (Haldol), which predomi-nantly block dopamine receptors, improve the chorea in many patients (Bradley et al., 2000). Chorea also is lessened by reser-pine (depletes presynaptic dopamine) and tetrabenazine (reduces dopaminergic transmission). Motor signs must be assessed and evaluated on an ongoing basis so that optimal therapeutic drug levels can be reached. Akathisia (motor restlessness) in the over-medicated patient is dangerous because it may be mistaken for the restless fidgeting of the illness and consequently can be over-looked.

In certain types of the disease, hypokinetic motor impairment resembles parkinsonism. In patients who present with rigidity, some temporary benefit may be obtained from antiparkinson medication, such as levodopa.

Patients who have emotional disturbances, particularly de-pression, may be helped by antidepressant medications. The threat of suicide is always present. Psychotic symptoms usuallyrespond to antipsychotic medications. Psychotherapy aimed at allaying anxiety and reducing stress may be beneficial (Hofman, 1999). It is imperative that nurses look beyond the disease to focus on the patient’s needs and capabilities (Chart 65-5). One study showed improved physical, mental, and social functioning in a small group of patients with Huntington’s disease using re-motivation therapy and providing a more stimulating environ-ment (Sullivan, Bird, Alpay et al., 2001). Surgically implanted fetal neural allografts are being tested in hopes of improving the functional, motor, and cognitive function of patients (Bachoud-Levi, Remy, Nguyen et al., 2000; Diederich & Goetz, 2000).

PROMOTING HOME AND COMMUNITY-BASED CARE

Teaching Patients Self-Care.

The needs of the patient and fam-ily for education depend on the nature and severity of physical, cognitive, and psychological changes experienced by the patient. Patients and family members are taught about the medications prescribed and about signs indicating a need for change in med-ication or dosage. The teaching plan addresses strategies to man-age symptoms such as chorea, swallowing problems, limitations in ambulation, and loss of bowel and bladder function. Con-sultation with a speech therapist may be indicated to assist in identifying alternative communication strategies if speech is affected.

Individuals of child-bearing age often seek information about their risk for transmitting the disease. Even though presympto-matic testing has been offered since 1986, approximately 75% of individuals at risk choose not to be tested (Hayden, 2000). For most people, the benefits of testing are unclear because of ethical and confidentiality issues. Genetic counseling is crucial following testing, and patients and their families may require long-term psychological counseling and emotional, financial, and legal sup-port (Williams, Schutte, Evers et al., 2000).

Continuing Care.

A program combining medical, nursing, psy-chological, social, occupational, speech, and physical rehabilita-tion services is needed to help the patient and family cope with this severely disabling illness. Huntington’s exacts enormous emotional, physical, social, and financial tolls on every member of the patient’s family. The family often live under a heavy burden of uncertainty, anxiety, and guilt. Regular follow-up helps to allay the fear of abandonment.

Home care assistance, day care centers, respite care, and even-tually skilled long-term care can assist the patient and family in coping with the constant strain of the illness. Although the re-lentless progression of the disease cannot be halted, families can benefit from supportive care.

Voluntary organizations can be major aids to families and have been largely responsible for bringing the illness to national atten-tion. The Huntington’s Disease Foundation of America helps pa-tients and families by providing information, referrals, family and public education, and support for research.