Huntington's disease is a genetic neurodegenerative disorder which causes progressive degeneration of the cells in areas of brain called the cerebral cortex and basal ganglia. The functions of these brain areas include control of movement, motivation, planning and personality. So, the progressive damage to these neural cells leads to changes in personality, and a progressive loss of movement & mental ability, which ultimately results in motor & cognitive decline and dementia. This inherited neurodegenerative disorder was first described by Dr. George Huntington in 1872, and it was named Huntington’s disease (HD) in memory of him. This disease was previously known as Huntington's chorea; the meaning of chorea is involuntary, jerky movements - a main symptom of the condition.
HD crosses all racial and ethnic boundaries, and affects both males and females equally. In the US, HD occurs in approximately 1 of every 10,000 to 20,000 people. Generally, the signs and symptoms of HD develop between the ages of thirty and fifty; however the onset of disease may start at any age. When disease develops in the early 20s age, it is called juvenile Huntington's disease and it is generally more severe. Approximately 5 to 10 % of individuals with Huntington's disease develop the symptoms before age 20. This earlier onset frequently leads to a faster disease progression and somewhat different presentation of symptoms.
Approximately 3 in 100 individuals having Huntington's disease seem to have no family history of the disease. This may be because relatives of preceding generations were not diagnosed - either due to untimely death from other causes, or loss of contact, for instance - due to adoption.
The later Symptoms of HD vary from person to person that worsen gradually, sometimes above a period of up to 20 years. Later symptoms may arouse in the following 3 areas: motor control (movement symptoms); behavior (psychiatric symptoms); and cognition (thinking symptoms). There is a wide spectrum of signs and symptoms with these 3 areas and which symptoms appear first differ greatly amid affected people. During the period of disease, some symptoms appear to be more dominant with a greater outcome on functional ability.
The inception and development of HD in younger people may be somewhat diverse from that in adults. Symptoms, which frequently present in them early in the course of the disease include:
Treatments for all kinds of HD symptoms are outlined below.
HD crosses all racial and ethnic boundaries, and affects both males and females equally. In the US, HD occurs in approximately 1 of every 10,000 to 20,000 people. Generally, the signs and symptoms of HD develop between the ages of thirty and fifty; however the onset of disease may start at any age. When disease develops in the early 20s age, it is called juvenile Huntington's disease and it is generally more severe. Approximately 5 to 10 % of individuals with Huntington's disease develop the symptoms before age 20. This earlier onset frequently leads to a faster disease progression and somewhat different presentation of symptoms.
Causes of Huntington's Disease
HD is a hereditary disorder passed down through a parent to child by means of a mutant gene. This mutant or faulty gene produces a protein named Huntingtin. This is still in a research that how this mutant gene develops the disease. Most of our genes inherit in 2 copies: one from mother and one from father. HD is an autosomal dominant disorder that means there is a need of only one copy of the mutant gene to cause the disorder. If you inherit a mutant gene from any of your parent, you are on prone to develop the disorder at some point in your life. A parent having a faulty Huntington gene can pass either the healthy copy of gene or the defective copy. That’s why every child in the family has a 50% chance of inheriting faulty Huntington gene.Approximately 3 in 100 individuals having Huntington's disease seem to have no family history of the disease. This may be because relatives of preceding generations were not diagnosed - either due to untimely death from other causes, or loss of contact, for instance - due to adoption.
Symptoms of Huntington's Disease
The early symptoms of HD are sometimes unnoticed because they are easygoing at first and individuals without the disorder can have the similar symptoms. You may have the HD symptoms for a long time prior to you realize that you have the disorder.- Early symptoms are:
- Lack of concentration
- Short-term memory problems
- Mild tremor
- Irritability
- Depression
- Clumsiness
- Mood changes
The later Symptoms of HD vary from person to person that worsen gradually, sometimes above a period of up to 20 years. Later symptoms may arouse in the following 3 areas: motor control (movement symptoms); behavior (psychiatric symptoms); and cognition (thinking symptoms). There is a wide spectrum of signs and symptoms with these 3 areas and which symptoms appear first differ greatly amid affected people. During the period of disease, some symptoms appear to be more dominant with a greater outcome on functional ability.
- Movement Symptoms: The movement symptoms related to HD can consist of both involuntary movements as well as impairments in voluntary movements.
- Chorea – involuntary writhing or jerking movements of limbs, face and other body parts
- Dystonia – involuntary, frequent contracture of muscles
- Stiffness of the legs
- Clumsiness of the arms and legs
- Muscle rigidity
- Impaired posture, balance and gait
- Slow, uncoordinated fine movements
- Difficulty in walking
- Abnormal or slow eye movements
- Difficulty in swallowing
- Problems in the physical production of speech
- Impairments in voluntary movements with a greater impact on an individual's ability to work, communicate, perform daily activities and remain independent.
- Cognitive Symptoms: The Cognitive Symptoms often related to HD are:
- Lack of the propensity to get stuck on a behavior, thought or action (perseveration)
- Difficulties in spatial perception, which can lead to clumsiness, falls or accidents
- Problems with organizing, planning and prioritizing tasks
- Inability to begin a conversation or task
- Lack of impulse control, which can cause outbursts, sexual promiscuity and acting without thinking
- Lack of awareness about individual's own abilities and behaviors
- Slowness in finding words or processing thoughts
- Complicatedness in learning new information
- Problems in focusing on a task for long periods
- Psychiatric Symptoms: Depression is the most common psychiatric disorder related with HD. However, this is not significant that depression patients must have the HD, because depression also occurs as a result of injury to the brain and the consequent changes in brain function.
- The Psychiatric signs and symptoms of HD may include:
- Loss of attention in regular activities
- Excessive sleeping or Insomnia
- Social withdrawal
- Feelings of unhappiness or sadness
- Loss of energy, fatigue and drowsiness
- Feelings of guilt or worthlessness
- Frequent thinking of suicide, dying or death
- Reduced sex drive
- Distractibility, indecisiveness and reduced concentration
- Loss of drive and initiative
- Alterations in appetite
- Other changes in personality or mood, but not necessarily specific psychiatric symptoms, may include:
- Anxiety
- Hallucinations
- Apathy
- Inappropriate sexual behaviors or sexual inhibition
- Psychosis
- Paranoia
- Irritability
- Agitation or fidgeting
- Dementia that slowly gets worse, including:
- Loss of judgment
- Disorientation or confusion
- Speech changes
- Personality changes
- Memory Loss
- The common psychiatric disorders associated with HD include:
- Mania – over-activity, elevated mood, inflated self-esteem and impulsive behavior
- Bipolar disorder – alternating episodes of mania and depression
- Obsessive-compulsive disorder – persistent, invasive thoughts and repetitive behaviors
- The Psychiatric signs and symptoms of HD may include:
The inception and development of HD in younger people may be somewhat diverse from that in adults. Symptoms, which frequently present in them early in the course of the disease include:
- Quick, noteworthy fall in overall school performance
- Loss of formerly learned physical or academic skills
- Behavioral problems - inappropriate social behavior
- Irritable and aggressive behavior
- Alterations in fine motor skills, which might be conspicuous in skills like handwriting
- Slight involuntary movements or tremors
- Seizures
- Rigid and contracted muscles, which affect gait
Treatments
Presently, there is no cure for HD and there is no treatment to sluggish its progression. Medications are there in the market to help for dealing with symptoms of HD, but treatments cannot prevent the behavioral, mental and physical decline associated with the condition. All the different symptoms listed above require different treatments; however one treatment rule highlights the all. HD progresses steadily over years, so it is very important that patient takes proper care of general health needs like dental care, immunizations and other age-appropriate evaluations. As the condition progresses, a GP can help patient for treating the expected medical complications of HD.Treatments for all kinds of HD symptoms are outlined below.
- Treatments for Movement Symptoms
- The symptom chorea can be treated with the medications like dopamine-depleting agents (Tetrabenazine) and dopamine-blocking agents (Haloperidol, Risperidone, Olanzapine).
- Other medications which can help to suppress muscle rigidity, chorea and dystonia include antianxiety drugs like diazepam and antiseizure drugs like clonazepam.
- Stiffness of the legs can be improved with the medications like Diazepam, Tizanidine, Baclofen and Dantrolene. For more twisted-looking stiff muscles, Dopamine agonists (Ropinirole, Pramipexole), Carbidopa-levodopa, Anticholinergic agents (Benztropine, Trihexyphenidyl) and a Botulinum toxin (Botox) injection can be utilized. Occupational and physical therapy are also good alternatives.
- There are no medications to improve the control of voluntary movements like clumsiness of the arms and legs, but both occupational therapy and physical therapy consultation are very helpful.
- Consultation of speech and language therapists can be useful to improve the problems of oral motor function like communication problems and swallowing problems.
- Treatments for Cognitive Symptoms
- There are no medications available to improve the declining cognitive function in the disease, but majority of cognitive symptoms can be decreased using checklists to help the patient keep on track, or using simple techniques like breaking tasks down into bit-by-bit tasks.
- Treatments for Behavioral Symptoms
- The most common symptom is depression, which can be life-threatening if left untreated. The medications usually utilized for treating depression include Tricyclic antidepressants (Imipramine, Nortriptyline, Amitriptyline), serotonin-norepinephrine reuptake inhibitors (Buproprion and Venlafaxine), selective serotonin reuptake inhibitors (Fluoxetine, Citalopram, Paroxetine), and others (Mirtazapin and Trazodone). Medications like olanzapine, haloperidol or quetiapine can be included if the depression is severe and accompanied by hallucinations, delusions or agitation.
- Agitation, violent outbursts and other symptoms of psychosis or mood disorders can be suppressed by antipsychotic drugs.
- The lows and highs associated with bipolar disorder can be prevented using the mood-stabilizing drugs such as lithium and anticonvulsants (valproic acid, amotrigine, divalproex). There is a requirement of periodic blood tests with lithium use because it can cause kidney and thyroid problems.
- A psychologist, psychiatrist or clinical social worker can provide talk therapy to assist a patient to deal with behavioral problems, develop coping strategies, facilitate effective communication and manage prospects during progression of the disease.
- Seizures are a major symptom associated with juvenile HD, which can be treated by anticonvulsant medications such as Valproic acid, lamotrigine, Phenytoin, topiramate and levetiracetam. However, the drug should be selected carefully after complete evaluation.
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