The pattern of symptoms can vary depending on the type of Creutzfeldt-Jakob disease (CJD).

In sporadic CJD, the symptoms mainly affect the workings of the nervous system (neurological symptoms) and these symptoms rapidly worsen in the space of a few months.

In variant CJD, symptoms that affect a person's behaviour and emotions (psychological symptoms) will usually develop first.

These are then followed by neurological symptoms around 4 months later, which get worse over the following few months.

Familial CJD has the same sort of pattern as sporadic CJD, but it often takes longer for the symptoms to progress – usually around 2 years, rather than a few months.

The pattern of iatrogenic CJD is unpredictable, as it depends on how a person became exposed to the infectious protein (prion) that caused CJD.

Read more about the types of Creutzfeldt-Jakob disease and causes of Creutzfeldt-Jakob disease.

Initial neurological symptoms

Initial neurological symptoms of sporadic CJD can include:

• difficulty walking caused by balance and co-ordination problems
• slurred speech
• numbness or pins and needles in different parts of the body
• dizziness
• vision problems, such as double vision and hallucinations (seeing or hearing things that aren't really there)

Initial psychological symptoms

Initial psychological symptoms of variant CJD can include:

• severe depression
• intense feelings of despair
• withdrawal from family, friends and the world around you
• anxiety
• irritability
• difficulty sleeping (insomnia)

Advanced neurological symptoms

Advanced neurological symptoms of all forms of CJD can include:

• loss of physical co-ordination, which can affect a wide range of functions, such as walking, speaking and balance (ataxia)
• muscle twitches and spasms
• loss of bladder control and bowel control
• blindness
• swallowing difficulties (dysphagia)
• loss of speech
• loss of voluntary movement

Advanced psychological symptoms

Advanced psychological symptoms of all forms of CJD include:

• loss of memory, which is often severe
• problems concentrating
• confusion
• feeling agitated
• aggressive behaviour
• loss of appetite, which can lead to weight loss
• paranoia 
• unusual and inappropriate emotional responses

Final stages

As the condition progresses to its final stages, people with all forms of CJD will become totally bedridden.

They often become totally unaware of their surroundings and require around-the-clock care.

They also often lose the ability to speak and can't communicate with their carers.

Death will inevitably follow, usually either as a result of an infection, such as pneumonia (a lung infection), or respiratory failure, where the lungs stop working and the person is unable to breathe. 

Nothing can be done to prevent death in these circumstances.

Advancements in palliative care (the treatment of incurable conditions) mean that people with CJD often have a peaceful death.

Read more about treating Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD) is caused by an abnormal infectious protein in the brain called a prion.

Proteins are molecules made up of amino acids that help the cells in our body function.

They begin as a string of amino acids that then fold themselves into a 3-dimensional shape.

This "protein folding" allows them to perform useful functions within our cells.

Normal (harmless) prion proteins are found in almost all body tissues, but are at the highest levels in brain and nerve cells.

The exact role of normal prion proteins is unknown, but it's thought they may play a role in transporting messages between certain brain cells.

Mistakes sometimes occur during protein folding and the prion protein can't be used by the body.

Normally, these misfolded prion proteins are recycled by the body, but they can build up in the brain if they aren't recycled.

How prions cause CJD 

Prions are misfolded prion proteins that build up in the brain and cause other prion proteins to misfold as well.

This causes the brain cells to die, releasing more prions to infect other brain cells.

Eventually, clusters of brain cells are killed and deposits of misfolded prion protein called plaques may appear in the brain.

Prion infections also cause small holes to develop in the brain, so it becomes sponge-like.

The damage to the brain causes the mental and physical impairment associated with CJD, and eventually leads to death.

Prions can survive in nerve tissue, such as the brain or spinal cord, for a very long time, even after death.

Types of CJD

The different types of CJD are all caused by a build-up of prions in the brain. But the reason why this happens is different for each type.

Sporadic CJD

Even though sporadic CJD is very rare, it's the most common type of CJD, accounting for around 8 in every 10 cases.

It's not known what triggers sporadic CJD, but it may be that a normal prion protein spontaneously changes into a prion, or a normal gene spontaneously changes into a faulty gene that produces prions. 

Sporadic CJD is more likely to occur in people who have specific versions of the prion protein gene.

At present, nothing else has been identified that increases your risk of developing sporadic CJD.

Variant CJD

There's clear evidence that variant CJD (vCJD) is caused by the same strain of prions that causes bovine spongiform encephalopathy (BSE, or "mad cow" disease).

In 2000, a government inquiry concluded that the prion was spread through cattle that were fed meat-and-bone mix containing traces of infected brains or spinal cords.

The prion then ended up in processed meat products, such as beef burgers, and entered the human food chain.

Strict controls have been in place since 1996 to prevent BSE entering the human food chain, and the use of meat-and-bone mix has been made illegal.

It appears not everyone who's exposed to BSE-infected meat will go on to develop vCJD.

All definite cases of vCJD occurred in people with a specific version (MM) of the prion protein gene, which affects how the body makes a number of amino acids.

It's estimated up to 40% of the UK population have this version of the gene.

Cases of vCJD peaked in the year 2000, in which there were 28 deaths from this type of CJD. There were no confirmed deaths in 2014.

Some experts believe that the food controls have worked and further cases of vCJD will continue to decline, but this doesn't rule out the possibility that other cases may be identified in the future.

It's also possible for vCJD to be transmitted by blood transfusion, although this is very rare and measures have been put in place to reduce the risk of it happening.

We don't know how many people in the UK population could develop vCJD in the future and how long it'll take for symptoms to appear, if they ever will.

A study published in October 2013 that tested random tissue samples suggested around 1 in 2,000 people in the UK population may be infected with vCJD, but show no symptoms to date.

Familial or inherited CJD

Familial or inherited CJD is a rare form of CJD caused by an inherited mutation (abnormality) in the gene that produces the prion protein.

The altered gene seems to produce misfolded prions that cause CJD. Everyone has 2 copies of the prion protein gene, but the mutated gene is dominant.

This means you only need to inherit 1 mutated gene to develop the condition. So if 1 parent has the mutated gene, there's a 50% chance it will be passed on to their children.

As the symptoms of familial CJD don't usually begin until a person is in their 50s, many people with the condition are unaware that their children are also at risk of inheriting this condition when they decide to start a family.

Iatrogenic CJD

Iatrogenic CJD (iCJD) is where the infection is spread from someone with CJD through medical or surgical treatment.

Most cases of iatrogenic CJD have occurred through the use of human growth hormone to treat children with restricted growth.

Between 1958 and 1985, thousands of children were treated with the hormone, which at the time was extracted from the pituitary glands (a gland at the base of the skull) of human corpses.

A minority of those children developed CJD, as the hormones they received were taken from glands infected with CJD.

Since 1985, all human growth hormone in the UK has been artificially manufactured, so there's now no risk.

But a small number of people exposed before 1985 are still developing iCJD.

A few other cases of iCJD have occurred after people received transplants of infected dura (tissue that covers the brain) or came into contact with surgical instruments that were contaminated with CJD.

This happened because prions are tougher than viruses or bacteria, so the normal process of sterilising surgical instruments had no effect.

Once the risk was recognised, the Department of Health tightened the guidelines on organ donation and the reuse of surgical equipment. As a result, cases of iCJD are now very rare.

BSE ('mad cow' disease)

Bovine spongiform encephalopathy (BSE), also known as "mad cow" disease, is a relatively new disease that first occurred in the UK during the 1980s.

One theory about why BSE developed is that an older prion disease that affects sheep, called scrapie, may have mutated. 

The mutated disease may have then spread to cows that were fed meat-and-bone mix from sheep containing traces of this new mutated prion.

Is CJD contagious?

In theory, CJD can be transmitted from an affected person to others, but only through an injection or consuming infected brain or nervous tissue.

There's no evidence that sporadic CJD is spread through ordinary day-to-day contact with those affected or by airborne droplets, blood or sexual contact. 

But in the UK, variant CJD has been transmitted on 4 occasions by blood transfusion.

A diagnosis of Creutzfeldt-Jakob disease (CJD) is usually based on medical history, symptoms and a series of tests.

A neurologist (a doctor who specialises in conditions of the nervous system) will carry out the tests to rule out other conditions with similar symptoms, such as Alzheimer's disease, Parkinson's disease, or a brain tumour.

The only way to confirm a diagnosis of CJD is to examine the brain tissue by carrying out a brain biopsy or, more commonly, after death in a post-mortem examination of the brain.

Specialist services at the National CJD Research and Surveillance Unit in Edinburgh and the National Prion Clinic in London advise local teams when making a diagnosis.

Tests for CJD

A clinical neurologist will rule out other conditions with similar symptoms.

They'll also check for some common signs of CJD by carrying out the following tests:

• an MRI brain scan – uses strong magnetic fields and radio waves to produce a detailed image of the brain, and can show up abnormalities particular to CJD
• an EEG – records brain activity and may pick up abnormal electrical patterns seen in sporadic CJD
• a lumbar puncture – a procedure where a needle is inserted into the lower part of the spine to draw out a sample of cerebrospinal fluid (which surrounds your brain and spinal cord) so it can be tested for a certain protein that indicates you may have CJD
• a prototype blood test for variant CJD has also been developed by the prion unit at the Medical Research Council (MRC) and is available through the National Prion Clinic
• tonsil biopsy – a small piece of tissue can be taken from the tonsils and checked for the abnormal prions found in variant CJD (they're not present in other types of CJD)
• genetic test – a simple blood test to find out whether you have a mutation (fault) in the gene that produces normal protein; a positive result may indicate familial (inherited) prion disease

Brain biopsy

During a brain biopsy, a surgeon drills a tiny hole into the skull and removes a small piece of brain tissue using a very thin needle.

It's carried out under general anaesthetic, which means the person will be unconscious during the procedure.

As a brain biopsy carries the risk of causing brain damage or seizures (fits), it's only performed in a few cases where there's a concern that someone doesn't have CJD but some other treatable condition.

There's no proven cure for Creutzfeldt-Jakob disease (CJD), but clinical studies are underway at the National Prion Clinic to investigate possible treatments.

At present, treatment involves trying to keep the person as comfortable as possible and reducing symptoms with medicines.

For example, psychological symptoms of CJD, such as anxiety and depression, can be treated with sedatives and antidepressants, and muscle jerks or tremors can be treated with medicines like clonazepam and sodium valproate.

Any pain experienced can be relieved using powerful opiate-based painkillers.

Advance directive

Many people with CJD draw up an advance directive (also known as an advance decision).

An advance directive is where a person makes their treatment preferences known in advance in case they can't communicate their decisions later because they're too ill.

Issues that can be covered by an advance directive include:

• whether a person with CJD wants to be treated at home, in a hospice, or in a hospital once they reach the final stages of the condition
• what type of medications they'd be willing to take in certain circumstances
• whether they'd be willing to have a feeding tube if they were no longer able to swallow food and liquid
• whether they're willing to donate any of their organs for research after they die (the brains of people with CJD are particularly important for ongoing research)
• if they lose lung function, whether they'd be willing to be resuscitated by artificial means – for example, by having a breathing tube inserted into their neck

Your care team can provide more advice about making an advance directive.

Specialist team

If a person is thought to have CJD, they're referred to the National Care Team for CJD at the National CJD Research and Surveillance Unit in Edinburgh, or the National Prion Clinic in London, for diagnosis and care.

A doctor and nurse from these services will be assigned to liaise with local services, including the person's GP, social worker, physiotherapist and occupational therapist.

Specialist teams are available for diagnosis and to offer clinical and emotional support to patients and their families, and work alongside the local care team.

A local care team may include doctors and nurses, occupational therapists, dietitians, continence advisers and social workers.

Treating symptoms of CJD

For more information about how some of the specific symptoms of CJD may be treated, see:

• treating ataxia (loss of physical co-ordination)
• treating urinary incontinence (loss of bladder control)
• treating bowel incontinence (loss of bowel control)
• treating dysphagia (swallowing difficulties)
• treating dystonia (muscle spasms and stiffness)
• help and support for blindness or vision loss

Care and support in the advanced stages of CJD

As CJD progresses, people with the condition will need significant nursing care and practical support.

As well as help with feeding, washing and mobility, some people may also need help peeing. A tube inserted into the bladder to drain urine (a catheter) is often required.

Many people will also have problems swallowing, so they may have to be given nutrition and fluids through a feeding tube.

It may be possible to treat someone with CJD at home, depending on the severity and progression of their condition.

Caring for someone with CJD can be distressing and difficult to cope with, so many carers prefer to use the specialist services of a hospital or hospice.

Read more about end of life issues, end of life care, and your own emotional wellbeing if you're caring for someone else.

Although Creutzfeldt-Jakob disease (CJD) is very rare, the condition can be difficult to prevent.

This is because most cases occur spontaneously for an unknown reason (sporadic CJD) and some are caused by an inherited genetic fault (familial CJD).

Sterilisation methods used to help prevent bacteria and viruses spreading also aren't completely effective against the infectious protein (prion) that causes CJD.

But tightened guidelines on the reuse of surgical equipment mean that cases of CJD spread through medical treatment (iatrogenic CJD) are now very rare.

There are also measures in place to prevent variant CJD spreading through the food chain and the supply of blood used for blood transfusions.

Protecting the food chain

Since the link between bovine spongiform encephalopathy (BSE, or "mad cow" disease) and variant CJD was confirmed, strict controls have been in place to stop BSE entering the human food chain.

These controls include:

• a ban on feeding meat-and-bone mix to farm animals
• the removal and destruction of all parts of an animal's carcass that could be infected with BSE
• a ban on mechanically recovered meat (meat residue left on the carcass that's pressure-blasted off the bones)
• testing on all cattle more than 30 months old (experience has shown that infection in cattle under 30 months of age is rare, and even cattle that are infected haven't yet developed dangerous levels of infection)

Blood transfusions

In the UK, there have been 4 cases where variant CJD has been transmitted by blood transfusion.

In each case, the person received a blood transfusion from a donor who later developed variant CJD.

Three of the 4 recipients went on to develop variant CJD, while the fourth recipient died before developing variant CJD but was found to be infected following a post-mortem examination.

It's not certain whether the blood transfusion was the cause of the infection, as those involved could have contracted variant CJD through dietary sources.

Nevertheless, steps were taken to minimise the risk of the blood supply becoming contaminated.

These steps include:

• not allowing people potentially at risk from CJD to donate blood, tissue or organs (including eggs and sperm for fertility treatments)
• not accepting donations from people who have received a blood transfusion in the UK since 1980
• removing white blood cells, which may carry the greatest risk of transmitting CJD, from all blood used for transfusions