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Huntington's Disease

Neurodegenerative / Genetic

Side view: Outer surface of the left hemisphere, front of the head to the left. Dashed outlines show deep structures as if seen through the surface. Highlighted: Basal Ganglia, Frontal Lobe.

Side view

Midline view: Inner surface of the left hemisphere, as if the brain were sliced down the middle, front of the head to the left. Highlighted: Basal Ganglia, Frontal Lobe.

Midline view

Brain regions discussed on this page. Research on huntington's disease points to these areas, though most conditions involve networks of regions working together rather than one region alone. The diagram shows the left hemisphere, with the front of the head to the left; dashed outlines are deep structures.

By Stuart Mathieson · Independent web developer in Scotland with an interest in all things science. · Last updated 2026-10-14 · Editorial policy

Educational overview, not medical advice. This page explains what huntington's disease is and which brain regions are involved. It isn't a diagnostic tool. If you have symptoms or concerns, please speak with a qualified healthcare professional.

An inherited neurodegenerative disorder caused by a single faulty gene, leading to progressive breakdown of neurons in the basal ganglia and producing involuntary movements, cognitive decline, and psychiatric symptoms.

Common Signs & Symptoms

  • Involuntary, jerking movements (chorea)
  • Difficulty with coordination and balance
  • Progressive decline in planning, organising, and other cognitive skills
  • Mood and personality changes, including irritability or depression
  • Difficulty with speech and swallowing in later stages

Why These Symptoms Happen

Each symptom can be traced, at least in part, to the job a particular part of the brain normally does. These links are simplified: real symptoms usually come from several connected regions.

SymptomBrain regionWhy it happens
Involuntary, dance-like movements (chorea) Basal Ganglia The striatum, part of the basal ganglia, normally suppresses unwanted movements. It's the first area to lose neurons in Huntington's, so movements "leak" through that would usually be held back - the opposite of the stiffness of Parkinson's.
Trouble planning, organising, and switching tasks Frontal LobeBasal Ganglia The basal ganglia work in loops with the frontal lobe for thinking as well as movement. As both are affected, executive skills decline - often before movement symptoms are obvious.
Irritability, depression, and loss of motivation Frontal LobeBasal Ganglia Circuits linking the basal ganglia and frontal lobe also regulate mood and drive. Psychiatric symptoms are common and can appear years before diagnosis.

Overview

Huntington's disease is an inherited neurodegenerative disorder caused by a single expanded gene - an abnormally long repeated DNA sequence in the HTT gene - that is passed down in an autosomal dominant pattern, meaning each child of an affected parent has a 50% chance of inheriting it. Symptoms most commonly emerge in a person's thirties or forties, though the age of onset and the specific mix of movement, cognitive, and psychiatric symptoms vary considerably between individuals, even within the same family.

Affected Brain Regions

Huntington's disease centres on progressive degeneration of the basal ganglia, particularly the striatum, which disrupts the normal balance of the circuit that selects and smooths voluntary movement - producing chorea, the involuntary, dance-like movements that are the condition's hallmark. As the disease progresses, degeneration extends to the frontal lobe and its connections, contributing to the decline in planning, judgment, and impulse control, along with the personality and mood changes many patients experience.

How It's Studied

The gene responsible was identified in 1993 after a decade-long international hunt, partly based on a large family affected by Huntington's in Venezuela. The faulty section is a repeated three-letter DNA "word" - CAG - and a genetic test simply counts the repeats. People with 40 or more repeats will develop the disease if they live long enough, 36 to 39 repeats carry a risk, and fewer than 36 do not cause Huntington's. Longer repeats tend to mean earlier onset.

MRI shows shrinkage of the caudate nucleus, part of the striatum, which makes the nearby fluid spaces look enlarged. Because the gene test can identify people years before symptoms, long-term studies have followed gene carriers and found that brain changes begin a decade or more before diagnosis.

Common Myths

"Huntington's can skip a generation."

Huntington's is dominant, so it doesn't skip generations: someone who doesn't inherit the gene can't pass it on. It can appear to skip if a parent died before symptoms started, or if the family history wasn't known.

"It's only a movement disorder."

The movements are the most visible sign, but changes in thinking and mood are often just as disabling, and sometimes appear first.

"Everyone at risk should get tested."

Testing is a personal decision with major consequences, and many at-risk people choose not to be tested. Genetic counselling before and after the test is standard, to help people decide what's right for them.

Current Research Directions

Because Huntington's has a single, well-identified genetic cause, it has become a major focus of gene-silencing research - therapies designed to reduce production of the harmful expanded protein using antisense oligonucleotides or related techniques, several of which are in active clinical trials. Current treatment otherwise focuses on managing movement and psychiatric symptoms, alongside multidisciplinary care as the disease progresses.

Compare

Parkinson's vs Huntington's

Key Terms

Related Brain Regions

Explore the regions involved in huntington's disease in more depth:

Basal Ganglia Frontal Lobe

This article is for general education and isn't a substitute for professional medical advice or diagnosis.

Sources & Further Reading

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