What is Huntington’s Disease?

Huntington’s disease (HD) is an inherited disorder that causes nerve cells (neurons) in parts of the brain to gradually break down. It results from a defective gene that interferes with manufacturing of a protein (Huntingtin) which is essential for brain development. This defect causes the DNA building blocks to repeat many more times than normal.  This mutation is passed down from parent to child. 

When a parent has Huntington’s, each child has a 50% chance of inheriting a copy of the chromosome that carries the mutation.  In few cases Huntington’s can occur without a family history and I referred to as ‘sporadic HD’  

Huntington’s disease often begins when people are in their 30s or 40s. In lesser cases it can occur before the age of 20 years old. When this happens, progression of the disease tends to be more rapid.

The disease attacks areas of the brain that help to control voluntary  movement, as well as other areas. People develop uncontrollable movements known as ‘chorea’ and abnormal body postures. They also develop problems with behaviour, emotion, thinking, and personality.

Early signs of HD can vary, but often include mild clumsiness or problems with balance or movement, cognitive or psychiatric symptoms (problems with thinking or emotion), and changes in behaviour.

Movement 

Involuntary movements called chorea affect all muscles of the body, more specifically the arms and legs, the face and the tongue. Symptoms may include:

• Involuntary jerking or writhing movements.
• Muscle rigidity or contractures.
• Slow or unusual eye movements.
• Difficulties with walking, posture and balance.

Some people may develop a rigid or stiff and have limited or no movement at all. This is called ‘akinesia’ Some people may begin with chorea but become rigid as the disease progresses. Others may have unusual fixed postures known as ‘dystonia’. Akinesia and dystonia can blend or alternate. Other movement symptoms can include tremors and unusual eye movements. 

Eventually the person will require a wheelchair and often becomes bed bound.

Other Physical changes

• slurred speech
• difficulties swallowing, eating and speaking
• Insomnia
• loss of energy and fatigue
• seizures

Huntington’s disease can cause trouble with cognition. These symptoms may include:

• Trouble with organisation, prioritising or focusing
• Lack of flexibility or getting stuck on a thought
• behaviour or action, known as perseveration.
• Impulse control that can cause outbursts, acting without thinking and sexual promiscuity.
• Lack of awareness of self awareness 
• Slow processing thoughts or ”finding” words.
• Difficulty learning new information

Mental health conditions

It is not uncommon for people with Huntington’s disease to experience depression. This can be as a reaction to diagnosis and the changes in condition as well as damage to the brain and changes in brain function. Symptoms may include:

• Irritability, anger, sadness
• Social withdrawal, apathy.
• Difficulty sleeping.
• Fatigue, lack of energy.
• Suicidal thoughts, psychosis

People with Huntington’s disease can also experience other Mental Health disorders. This can be in isolation of Huntington’s disease  or due to changes in brain function. Other mental health conditions that can occur include:

• Obsessive-compulsive disorder- pattern of unwanted and intrusive thoughts and fears (obsessions). These obsessions lead to repetitive behaviours ‘compulsions’. These thoughts and behaviours severely impact on daily activities and cause immense distress. Mania- a condition characterised by elevated mood, overactivity, impulsive behaviour such as spending money and inflation in self-esteem.
• Bipolar disorder- a chronic condition that involves intense mood changes from extreme highs to extreme lows. They experience Manic (or hypomanic) episodes — feeling very euphoric or high During this phase people may feel very happy or irritable; have inflated self-esteem or grandiose ideas; have increased energy and activity and reduced need to sleep; have racing thoughts and speech; display impulsive or risky behaviours with spending, business or sexual activity. During a depressive phase, people may experience low mood; lack motivation and interest in usual activities or hobbies, have difficulty concentrating; withdraw from social contact and activities, have feelings of worthlessness or guilt and can have suicidal thoughts

How is Huntington’s disease diagnosed?

Often a combination of tests and other information is required to diagnose HD  including medical history, neurological and laboratory tests, brain imaging, and genetic testing.

• Neurological exam —A neurologist will obtain a medical and family history.  Neurological and physical exams are often performed including assessing reflexes, balance, movement, muscle tone, hearing, walking, and mental status. 
• Genetic tests—Genetic testing can confirm or rule out the suspected genetic condition. The most effective and accurate method of testing for HD “ direct genetic test”  involves counting the number of CAG repeats in the HD gene using DNA taken from a blood sample.  36 or more repeats supports a diagnosis of HD whilst a result of 26 or fewer repeats rules out HD.
• Individuals with HD may be referred to specialists such as psychiatrists, genetic counsellors, clinical neuropsychologists, or speech pathologists to support diagnosis.
• Diagnostic imaging— if a person’s family history and genetic testing are inconclusive, the doctor may recommend brain imaging, such as CT scans or MRI’s. This is more useful in advanced presentations where shrinkage in parts of the brain and enlargement of ventricles may show. These changes do not necessarily indicate HD, as they can be seen  in other disorders, however in combination with other tests they can be useful.  In early stages, there may be no changes in brain imaging. 

Treating HD

There is no treatment that can stop or reverse HD, all modalities tend to focus on symptom control.

• Drugs such as tetrabenazine and deuterabenazine can treat involuntary movements associated with HD
• Antipsychotic drugs may be used to manage chorea and help to control hallucinations, delusions, and violent outbursts.

Lotus Disability Care assists a number of clients with Huntington’s Disease and their families.  Ensuring people have opportunities to maintain independence, and caregivers have sufficient support and respite is imperative to keeping families healthy and able to care for their loved ones. 

For further information on Huntington’s Disease 

13 HEALTH: (13 43 25 84)

NeuroAssist InfoLine: 1800 177 591

MS QLD: 1800 177 591 – info@msqld.org.au

Huntington’s Australia

Tel: 1800 244 735

Email: admin@huntingtonsaustralia.au – huntingtonsaustralia.au