VOL: 101, ISSUE: 20, PAGE NO: 52
Blaire Smith-Bathgate, RGN, AdvDMT, is nurse practitioner, The National CJD Surveillance Unit, University of Edinburgh, Western General Hospital, EdinburghCreutzfeldt-Jakob disease (CJD) is one of a group of diseases known as transmissible spongiform encephalopathies. It was first described in the 1920s by two German neurologists - Hans Gerhard Creutzfeldt and Alfons Jakob. It is a rare and fatal human neurodegenerative condition that is characterised by a rapidly progressive dementia associated with ataxia (unsteady gait) and myoclonus (involuntary 'jerks'). There are four known types of the disease: sporadic, iatrogenic, genetic and variant.
Creutzfeldt-Jakob disease (CJD) is one of a group of diseases known as transmissible spongiform encephalopathies. It was first described in the 1920s by two German neurologists - Hans Gerhard Creutzfeldt and Alfons Jakob. It is a rare and fatal human neurodegenerative condition that is characterised by a rapidly progressive dementia associated with ataxia (unsteady gait) and myoclonus (involuntary 'jerks'). There are four known types of the disease: sporadic, iatrogenic, genetic and variant.
Sporadic CJD is the most common form of Creutzfeldt-Jakob disease, occurring in approximately one per million of the population annually in the UK, with an equal worldwide distribution (National CJD Surveillance Unit, 2003). Males and females appear to be equally affected, with the average age of onset being the mid-sixties (NCJDSU, 2003). The cause of sporadic CJD remains unknown and it is not transmissible by normal person-to-person contact.
The most common presenting features are cognitive impairment and cerebellar ataxia, with relentless deterioration. Visual symptoms, myoclonus and problems with speech and swallowing also occur. In the terminal stages, patients are usually confined to bed, unable to speak or swallow and require total nursing care. About 65 per cent of patients die within four to six months of the onset of the disease (Knight et al, 2004).
Diagnosis of sporadic CJD is difficult, owing to the rarity of the disease and the absence of a simple diagnostic test. A definite diagnosis can only be reached following examination of brain tissue, usually at post-mortem. A probable or possible diagnosis is based on the presence of characteristic features of the disease and assumes that alternative diagnoses have been excluded. Diagnosis can be aided by the findings of an electroencephalogram (EEG), a cerebrospinal fluid (CSF)14-3-3 test, or magnetic resonance imaging (MRI) of the brain.
In sporadic CJD, the EEG may show characteristic periodic sharp wave complexes, but in some cases the EEG changes may not appear until very late in the progression of the disease, if at all. A positive CSF 14-3-3 test is strongly supportive of a diagnosis of sporadic CJD. In approximately two-thirds of cases of sporadic CJD an MRI brain scan may show changes in the caudate and putamen, which are specific areas deep within the brain.
Iatrogenic CJD is a very rare form of the disease and occurs through accidental transmission of infection during medical or surgical procedures. It has occurred as a result of transmission via contaminated human pituitary growth hormone, human dura mater grafts and, rarely, via corneal grafts and instruments used in neurosurgery. The clinical features are partially dependent on the route of transmission, but some cases present in a manner that is clinically indistinguishable from sporadic CJD.
Diagnosis essentially rests on the history of a known risk factor (as above) in a patient with a progressive and unexplained neurological illness.
Genetic CJD is rare, accounting for 10-15 per cent of CJD cases (WHO, 1998). Over 30 disease-associated mutations of the prion protein gene that causes this type of CJD have been identified, and inheritance is autosomal dominant, meaning that each offspring of an affected person has a 50 per cent chance of inheriting the abnormal gene (Knight at al, 2004). In some cases, no known family history has been identified. There are two notable geographical clusters of genetic CJD in Israel and Slovakia.
Genetic CJD can have diverse clinical features although, overall, these patients tend to present at a younger age and may survive longer than those with sporadic CJD. A blood test to exclude genetic CJD is available for those at risk of the disease.
Variant CJD (vCJD)
This form of the disease was first reported in 1996 and most probably resulted from human exposure to bovine spongiform encephalopathy (BSE) in the food chain. The majority of cases have occurred in the UK, although a small number have been recorded in France, Ireland, Italy, Canada and the USA. The mean age of onset in vCJD is 28 years, with a range of 14-74 years (NCJDSU, 2003).
The most common presentation of vCJD is psychiatric/behavioural disturbance, with pain and unpleasant sensory symptoms also reported in the early stages of the disease. Other features include anxiety, agitation, delusions and hallucinations (Spencer et al, 2002).
Variant CJD progresses at a much slower rate than the sporadic form of the disease, with a median duration of illness of 14 months (range 6-39 months) (NCJDSU, 2003). As the disease progresses, dementia, ataxia and involuntary movements can occur. The terminal stages of this disease will render the individual being unable to speak, incontinent and confined to bed. Death is usually due to intercurrent infection (Zeidler et al, 1997).
As with sporadic CJD, diagnosis depends on the exclusion of other treatable diseases. The three tests that can assist in the diagnosis are an MRI brain scan, a tonsil biopsy and analysis of the cerebrospinal fluid for the 14-3-3 protein.
In the majority of cases, an MRI scan showing a pulvinar sign, together with the relevant clinical picture, can lead to a diagnosis of probable vCJD without the need for any invasive procedures. The pulvinar sign has been found in over 90 per cent of pathologically proven vCJD cases (Collie et al, 2001).
A tonsil biopsy may show the presence of the prion protein, which adds weight to the diagnosis, but this procedure carries the risk of anaesthesia and surgical complications.
The presence of 14-3-3 protein in the cerebrospinal fluid may provide support for the diagnosis, but a negative result does not exclude vCJD. A definite diagnosis depends on the study of brain tissue either at post-mortem or following a brain biopsy.
Related nursing care issues
Normal social or routine clinical contact does not present a risk to health care workers, families or others. There is no evidence of infectivity in saliva, body fluids or excreta (Department of Health, 2000). Standard infection control practices should be applied to patients with CJD, regardless of the type. Special precautions are required only when handling high-risk tissues such as central nervous system or eye tissue, including cerebrospinal fluid. However, it is advisable to consult local infection control guidance.
Post-mortems are carried out in high-risk suites, which provide a safe environment for those involved in the procedure. Results of the post-mortem may take weeks or months to become available. Body bags are used for the transportation of potential cases in order to protect against the possibility of accidental seepage of body fluids after death.
It should be emphasised that viewing a body, even after autopsy, is safe. There are no special burial requirements for those patients suspected of having had CJD.
The role of the National CJD Surveillance Unit
The National CJD Surveillance Unit (NCJDSU) was set up in 1990 in response to a recommendation made in the Report of the Working Party on Bovine Spongiform Encephalopathy (Southwood Committee,1989). Funding comes from the Department of Health and the Scottish Executive. The initial aim of the unit was to monitor CJD in order to identify any changes in the pattern of the disease. As a result of this process, and with the co-operation of colleagues throughout the UK, vCJD was identified in 1996. The unit continues surveillance of CJD and monitors characteristics of CJD and trends in incidence rates. It also studies risk factors for the disease.
In response to concerns regarding the care of patients with CJD, a national care team was formed, and this is based at the NCJDSU. The aims of the team are available on: www.cjd.ed.ac.uk
Currently, there is no proven therapy for CJD. However, the Medical Research Council has funded a formal treatment trial of CJD, which began in 2004. In the first instance it aims to study the drug quinacrine, which was originally used as an anti-malarial drug.
Progress has been made in all aspects of CJD, from diagnosis to nursing care and related issues. With the advent of a drug trial there is the possibility of some form of treatment being available in the future.
Continuing surveillance of CJD is necessary, not just from an epidemiological point of view but also to monitor the clinical presentation to identify if new variants arise.
National CJD Surveillance Unit:www.cjd.ed.ac.uk
CJD Support Network:www.cjdsupport.net/
National Prion Clinic:www.nationalprionclinic.org/