CNS: Huntington's Disease

• Huntington Disease (HD), also known as Huntington Chorea, affects the central nervous system.

Characteristics

• Inherited neurodegenerative disease with choreiform movements and progressive dementia.
• Progressive, often leading to death 15-20 years after neurological or psychological impairment onset.
• Causes involuntary movements in adults, but rigidity can also occur.
• Males and females are diagnosed in equal numbers.
• Symptoms typically emerge between 35-55 years but may appear earlier (youth 20 and under with Juvenile HD (10%)) or later (60+ years with Late Onset HA (10%)).
• Prevalence in North America ranges from 4 to 8 cases per 100,000 people.

Etiology

• Caused by a mutation in the gene for the huntingtin protein, located on chromosome 4.
• The defect leads to replication of cytosine, adenine, and guanine (CAG) sequence.
• Each child of a parent with HD has a 50/50 chance of inheriting the gene.
• A child not inheriting the gene will not develop or pass on the disease.

Pathophysiology

• Inherited as an autosomal dominant disorder.
• Pathological findings show tissue changes in the brain.
• Enlarged ventricles result from atrophy of the adjacent basal ganglia, specifically the caudate nucleus and putamen.
• Extensive loss of small and medium-sized neurons leads to the basal ganglia atrophy.
• The brain volume can decrease by 20%.
• Loss of neurons affects neurotransmitters.
• The normal balance of excitation and inhibition responses is disrupted in the basal ganglia and thalamus.

Signs & Symptoms

• Physical: weight loss, involuntary movements (chorea), diminished coordination, difficulty in walking, talking, and swallowing.
• Voluntary movement impairment impacts the ability to work, perform ADLs, communicate, and maintain independence.
• Cognitive: difficulty with focus, planning, recalling information, and making decisions; impaired judgment.
• Emotional: depression, apathy, irritability, anxiety, obsessive behavior potentially due to a brain injury and subsequent changes in brain function.

Early Stage

• Individuals can still function well at work and home.
• Difficulties appear around organizing routines and coping with new situations.
• Abilities decline in recalling, making decisions, and paying attention to detail.
• Mood changes and irritability arise.
• Minor involuntary movements as well as fidgeting, twitching, or excessive restlessness start.
• Changes in handwriting and difficulties with daily tasks like driving begin.

Intermediate Stage

• Increases difficulties in working and managing a household, but can still deal with ADLs.
• Symptoms progress from the early stage Symptoms include:
  • Obvious involuntary movements (chorea)
  • Difficulties with walking, coordination, and balance
  • Challenges with speaking (slurred)
  • Problem-solving becoming more difficult
  • Difficulties with swallowing
  • Weight loss from energy expenditure from choreoathetoid movements

Advanced Stages

• Individuals cannot manage ADLs and usually require professional care.
• Symptoms:
  • Decrease in involuntary movements and increase in rigidity.
  • Increased difficulty with swallowing.
  • The ability to communicate diminishes, but understanding remains possible.
  • Significant weight loss occurs.
  • Dementia and Bradykinesia arises.
  • Dystonia (involuntary mm contractions)

Juvenile HD (JHD) & Late Onset HD (LOHD)

• Juvenile HD (JHD) follows a rapid course, chorea is less prominent or absent.
• Initial symptoms of JHD:
  • Slow, stiff movement (rigidity), sometimes with tremors.
  • Seizures, falls, clumsiness.
  • Contracted and rigid muscles impacting gait, especially in young children.
  • Difficulties learning in school, attention deficits.
  • Increase in responsive behaviours.
• Late Onset HD (LOHD) is diagnosed past 60, sometimes misdiagnosed due to the belief patients cannot develop HD after the typical onset of 35-55.

Diagnosis

• No diagnostic testing available.
• Diagnosis bases clinical symptoms, family history, genetic testing.
• Contributing assessments:
  • Neurological examination tests for motor, sensory, and psychiatric symptoms.
  • Neuropsychological testing checks memory, reasoning, mental agility, language skills, and spatial reasoning.
  • Psychiatric evaluation by a psychiatrist assesses emotional state, behaviors patterns, judgment quality, coping skills, signs of disorder thinking, and evidence of substance abuse.
  • MRI, CT, genetic counseling, and predictive genetic tests.

Treatment

• No cure, treatment focuses on symptom management.
• Medications help control chorea.
• Medications for psychiatric disorders include antidepressants, antipsychotics, and mood-stabilizing drugs.
• Psychotherapy by a psychiatrist, psychologist, or clinical social worker is used.
• Speech, physical, and occupational therapy are used

Massage & Clinical Manifestations

• Classic choreiform movements manifest as piano-playing motions in fingers and facial grimaces.
• Trunk involvement can result in a dancing gait.
• Balance may appear off, but overall, the ability to balance is well preserved.
• Patients who develop HD by age 35 often become bedridden within 15-20 years.
• Patients may become argumentative, impulsive, or erratic.
• Sleep disorders and urinary incontinence may occur.
• Muscle strength and tendon reflexes are usually normal.

Huntington's Disease (HD) is a genetic neurodegenerative disorder affecting the central nervous system. This progressive disease leads to involuntary movements and dementia, typically emerging between 35-55 years old. HD is caused by a mutation in the huntingtin protein gene, with each child of an affected parent having a 50% chance of inheriting it.