Huntington’s Disease and Its Behavioral and Psychiatric Effects

By Uzair Ahmed

Introduction

•Huntington's disease (HD) is a neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and behavioral

symptoms.•HD is the most common genetic cause of

abnormal involuntary writhing movements calledchorea, which is why the disease used to be called Huntington's chorea.

Cause:

• HD is one of several trinucleotide repeat disorders which are caused by the length of a repeated section of a gene exceeding a normal range, a genetic defect on chromosome no. 4.

• Generally, people have fewer than 36 repeated glutamines which results in production of the cytoplasmic protein Huntingtin. However, a sequence of 36 or more glutamines results in the production of a protein which has different characteristics.This altered form, called mHtt (mutant Htt), increases the decay rate of certain types of neurons. 

Inheritance:• Huntington's disease has autosomal dominant

 inheritance, meaning that an affected individual typically inherits one copy of the gene with an expanded trinucleotide repeat (the mutant allele) from an affected parent.

• In this type of inheritance pattern, each offspring of an affected individual has a 50% risk of inheriting the mutant allele and therefore being affected with the disorder.

• As the disease is passed along in families, it becomes evident at younger and younger ages.

Signs and Symptoms:

•HD is considered a tripartite neurodegenerative disorder, with motor, cognitive, and psychiatric changes.

•Appear between age 30-50•Common physical symptoms are

uncontrollable rapid jerky movements , minor twitching in fingers and toes, poor balance, slurred speech, difficulty swallowing, and sensory sypmtoms like numbness and pain.

The Behavioural and Psychological Symptoms of HD (BPSHD)

• BPSHD are part of the disease process and present severe problems to those with HD, their families and caregivers, and wider society.

• Apathy, • depression, • lack of insight, • disinhibition, • impulsivity, • obsessive and compulsive symptoms, • anxiety, • frustration, • irritability, • and aggression.

Causes of the BPSHD • There are multiple causes of the BPSHD, with underlying factors

including a combination of the following:

• Neurobiological factors neurochemical and neuropathology, current health status, presence of coexistent medical or psychiatric syndromes, such as delirium, urinary tract infections, arthritis, insomnia,dehydration.

• Cognitive factors – cognitive impairment

• Psychological factors – personality traits, response to stress

• Social factors – changes in family structure, leaving work, changes in routine, stigmatisation and exclusion

• Environmental factors – changes in caregiver, moving house, unmet needs of the person with HD, such as the presence of pain, wetness, fatigue, or fear.

The common BPSHD

•There are many ways in which the BPSHD can be grouped, including in symptom clusters, function, or altered behaviour.

1. Affective (Mood-related) Sypmtoms

Apathy/ Indifference / lack of motivation Depression / Suicidal tendency Agitation / Aggression Anxiety and stress

2. Perceptual Symptoms & Mania

Psychotic symptoms like halucinations, which can involve sounds (especially voices), visions, olfactory (smells), gustatory (taste) and tactile (feeling of being touched).

Mania : People with HD may become manic, displaying elevated or irritable mood, impulsiveness, overactivity, decreased need for sleep, and grandiosity. Symptoms include increased levels of activity, pressured speech, uncharacteristic cheerfulness, large and inappropriate purchases, and a return of sexual interest after a long period of an inability to experience pleasure or impotence.

Disinhibition & Impulsivity : Disinhibition has been associated with impulsive and

inappropriate behaviours. People who are disinhibited have trouble controlling a sudden desire to do or say something that comes to mind, even if the behaviour is inappropriate, hurtful, or repetitive.

Perseveration, Obsessive-Compulsive behaviour, Inflexibility & Self-Centeredness:

Some people with HD appear to have an inability to see things from another person’s point of view. They can appear to be self-centred and selfish.

A person with HD may be perseverative or often become “stuck” on an idea or activity. They can be rigid in their behaviour and struggle to change, adapt, and/or alter routine.

Frustration & IrritabilityFrustration may be caused by clumsiness or difficulties with

communication, and also due to physical factors such as hunger and fatigue.

Irritability is typically manifested by verbal outbursts, threatening behaviours, aggression, and inflexible/uncooperative behaviour. Bad-tempered outbursts and irritability are among the most common and troublesome BPSHD.

Altered Sexuality

3. Personality Symptoms

4. Unawareness, Denial, & Lack of Insight

A lack of self awareness and an inability to evaluate one’s own performance may cause individuals to be unaware of mistakes that are obvious to others.

People with HD may have reduced capacity for self-reflection and insightfulness.

Deny having HD or accept this reality and accept their symptoms.

be unable to recognize their own disabilities or to evaluate their own behaviour and limitations. This can result in anger as some people with HD cannot understand why they can no longer, say, drive or work.

Treatment and Management of the BPSHD

BPSHD are treatable and are often more amenable to therapy than any other symptoms of HD. Therefore role of family as well as professional caregiver and psychiatrist is very important in the management of BPSHD.

Pharmacological Management :

Medication is typically used for moderate to severe BPSHD. When considering using medication in a person with HD, consideration must be given to their age and the disease-related changes.

Review of the medication regimen is also recommended at 12 week intervals, in order to measure efficacy (effect of the frequency and severity of the symptom) and its side effects.

Prognosis:• Life expectancy in HD is generally around 20 years following the

onset of visible symptoms. The earlier the symptoms appear in life, the faster the disease progresses!

• Most life-threatening complications result from muscle coordination and, to a lesser extent, behavioral changes induced by declining cognitive function.

•  The largest risk is pneumonia, which causes death in one third of those with HD. As the ability to synchronize movements deteriorates, difficulty clearing the lungs and an increased risk of aspirating food or drink both increase the risk of contracting pneumonia. 

• Suicide is the third greatest cause of fatalities, with 7.3% of those with HD taking their own lives and up to 27% attempting to do so.

• Other associated risks include choking, physical injury from falls, and malnutrition.