Creutzfeldt-Jakob and New-Variant Creutzfeldt-Jakob Disease

CREUTZFELDT-JAKOB AND NEW-VARIANT CREUTZFELDT-JAKOB DISEASE

Creutzfeldt-Jakob disease (CJD) and new-variant Creutzfeldt-Jakob (nvCJD) disease belong to a group of degenerative, infectious neurologic disorders called transmissible spongiform enceph-alopathies (TSE). Although CJD and nvCJD have distinct clini-cal and histologic differences, they have many features in common. Both are rare and have incubation periods ranging from months to decades. In both, the symptoms are progressive, there is no definitive treatment, and the outcome is fatal.

CJD occurs primarily in adults ages 50 to 70. The incidence of disease is 1 per million worldwide (Weihl & Roos, 1999). nvCJD occurs in younger patients and has a prolonged duration of illness compared to CJD. The risk of nvCJD in the United States is thought to be low as cattle are fed primarily with soy-derived feed (see Pathophysiology, below). Only a few rare cases of TSE have occurred in the United States to date (Weihl & Roos, 1999).

Pathophysiology

Although still debated, the causative agent appears to be a prion, a proteinaceous, infectious particle smaller than a virus (Davis & Kennedy, 2000). The prion converts a normal cellular protein to an abnormal form, thus destroying neurons and glial cells. The gray matter takes on a spongy appearance (spongiform changes). Lesions, or plaques, also appear in various locations in the CNS (Weihl & Roos, 1999).

In CJD, the method of transmission is frequently unknown; however, direct transmission (by contact with infected animals) of the prion to humans may initiate the degenerative neurologic process. The disease is also heritable, and familial groups account for approximately 15% of cases, clustering in certain parts of the world. Iatrogenic transmission accounts for approximately 5% of cases and is due to contaminated neurosurgical devices and blood transfusions and the use of cadaver-derived growth hormone (growth hormone is now created synthetically) (World Health Organization, 2001).

Based primarily on an outbreak of cases in England in the late 1980s and through the 1990s, it was discovered that in nvCJD, the primary mode of transmission appeared to be the ingestion of CNS tissue of infected cattle. However, in 1998, additional con-cerns were raised about the safety of the English blood supply. The prion exists in lymphoid tissue and blood in all of the TSEs, but the incidence is higher in nvCJD. In light of the rising in-cidence of nvCJD, concern arose about the risk of infection through transfusion of blood products. There is no method avail-able to screen blood for infectivity. All blood must be leukocyte-depleted prior to transfusion. In 1998, the use of plasma derived from citizens of the United Kingdom for use in manufacturing blood-derived products was banned in the U.S. (Weihl & Roos, 1999).

Clinical Manifestations

Many patients with CJD have vague prodromal symptoms prior to specific neurologic changes. Symptoms usually include be-havioral changes, dementia, mutism, visual changes, cerebellar, pyramidal, and extrapyramidal signs, and myoclonic jerks. The myoclonic jerks may be spontaneous or precipitated by auditory or tactile stimuli. The myoclonus (spasms) may involve a single muscle group, a limb, or the entire body. The symptoms progress until the patient is completely unaware of the environment and immobilized.

Although the same type of agent, a prion, causes nvCJD, there are distinct differences in the clinical manifestations of nvCJD and CJD. In nvCJD, there are more prion-reactive plaques, re-ferred to as florid plaques, surrounding spongiform tissue through-out the cerebrum and cerebellum. The characteristic EEG changes present in CJD are absent in nvCJD. Anxiety, depression, and be-havioral changes are the initial symptoms of nvCJD. Cerebellar symptoms occur, with gait changes and ataxia. Myoclonus is present in most patients diagnosed with nvCJD. Memory and cognitive impairments occur late in the course of nvCJD. Mutism occurs in both nvCJD and CJD (Almond, 1998).

Assessment and Diagnostic Findings

Historically, sharp waves and spikes on the EEG were the only features available to support the diagnosis of CJD. Recent detec-tion of a polyclonal antibody (protein 14-3-3) in CSF has enabled the diagnosis of CJD (Poser, Mollenhauder, Krab et al., 1999). In addition to the presence of a polyclonal antibody in CSF, a protein increase is demonstrated along with the presence of en-zymes indicative of neuronal loss. CT scan is used to rule out dis-orders that may mimic the symptoms of CJD. MRI scans are useful, identifying lesions in the basal ganglia in most cases of CJD. Definitive diagnosis is made by brain biopsy or at autopsy.

Medical Management

After the onset of specific neurologic symptoms, progression of disease occurs quickly. There is no effective treatment for CJD or nvCJD. The care of the patient is supportive and palliative. Goals of care include prevention of injury related to immobility and de-mentia, promotion of patient comfort, and provision of support and education for the family. The duration of disease is 4 to 5 months in CJD and 16 months in nvCJD, with death occurring as a result of respiratory failure or sepsis (Weihl & Roos, 1999).

Nursing Management

As with medical management, the nursing care of patients is pri-marily supportive and palliative. Psychological and emotional support of patients and families throughout the course of the ill-ness is needed This care extends to providing for a dignified death and supporting the family through the processes of grief and loss. Hospice care should be used either at home or at an inpatient facility.

Prevention of disease transmission is an important part of nursing care. Although patient isolation is not necessary, use of standard precautions is important. Institutional protocols are fol-lowed for blood and body fluid exposure and decontamination of equipment. Conventional methods of sterilization do not destroy the prion. The CDC guidelines (based on WHO guidelines) outline the stringent sterilization methods that must be used to de-stroy the prion on surfaces.