Understanding when and how to test for Huntington’s disease can be a life-changing decision. For those experiencing unusual movements or changes in thinking and mood, or for individuals who have a parent with the condition, knowing what diagnostic options exist offers both clarity and the chance to plan ahead—even though the journey ahead may be uncertain.

Introduction: Who Should Consider Diagnostic Testing

If you’ve started noticing small, unusual jerking movements in your hands or fingers, or if you’re finding it harder to focus, make decisions, or control your emotions, these could be early warning signs that something needs medical attention. Similarly, if one of your parents has been diagnosed with Huntington’s disease, you face a personal decision about whether to find out if you carry the gene that causes this condition. Understanding who should pursue diagnostic testing, and when, is an important first step.^[1]

People most commonly begin showing symptoms of Huntington’s disease between the ages of 30 and 50, although it can appear earlier or later in life. The condition gradually damages specific areas of the brain, leading to problems with movement, thinking, and emotional well-being. Because the disease is inherited in a very direct way—if one of your biological parents has it, you have a 50% chance of inheriting the altered gene—many people choose to get tested even before symptoms appear.^[2][4]

You should consider seeking medical advice if you notice early symptoms such as difficulty concentrating, memory troubles, low mood, personality changes like increased irritability or impulsiveness, or small twitching movements you cannot control. Sometimes these changes are easier for others to notice before you do. Clumsiness, trouble holding objects like a pen, or losing your balance may also be among the first physical signs.^[5]

For those who have a family history of Huntington’s disease but no symptoms yet, the decision to undergo genetic testing is deeply personal. Some individuals want to know their genetic status to help plan their future—whether that involves career decisions, starting a family, or preparing financially and emotionally. Others prefer not to be tested, especially if they don’t have symptoms, because there is currently no way to prevent the disease from developing if you carry the gene.^[5][9]

Classic Diagnostic Methods

The process of diagnosing Huntington’s disease typically begins with a visit to your family doctor, who will listen to your concerns and examine you. If they suspect Huntington’s disease based on your symptoms or family history, they will refer you to a specialist called a neurologist—a doctor who focuses on conditions affecting the brain and nervous system.^[5]

During your first appointment with a neurologist, the doctor will ask you detailed questions about your symptoms, when they started, and how they’ve changed over time. They’ll also want to know about your family medical history, particularly whether any of your parents, grandparents, or other relatives have had Huntington’s disease. This family history is extremely important because the disease is passed down through families in a predictable pattern.^[9]

Physical and Neurological Examination

The neurologist will perform a neurological exam, which is a series of relatively simple tests to check how well your brain and body are working together. During this exam, the doctor will observe your movements, checking for involuntary jerking or twitching—a symptom known as chorea, which resembles dance-like movements. They will test your reflexes, muscle strength, and balance. They’ll also assess your coordination by asking you to perform tasks like touching your nose with your finger or walking in a straight line.^[9]

The doctor will evaluate your senses as well, including your ability to see, hear, and feel touch. Your eye movements may be examined closely, as unusual eye movements can appear early in Huntington’s disease. All of these observations help the doctor understand which parts of your brain may be affected and how severely.^[2]

Mental and Cognitive Assessment

Because Huntington’s disease affects thinking abilities as well as movement, your doctor will want to assess your cognitive function. This may involve asking you questions to test your memory, attention, problem-solving skills, and ability to learn new information. They may also ask about your mood, emotions, and whether you’ve noticed changes in your behavior or personality—such as feeling more irritable, anxious, or sad than usual.^[9]

In some cases, you may be referred to a licensed psychologist for more thorough neuropsychological testing. These tests go deeper into examining your memory, reasoning ability, language skills, and spatial awareness—how you understand the position of objects around you. The results help doctors understand how Huntington’s disease may be affecting your thinking and daily functioning.^[9]

Brain Imaging Tests

To get a clearer picture of what’s happening inside your brain, your doctor may order brain imaging tests. The most common types are MRI scans (magnetic resonance imaging) or CT scans (computed tomography). These tests create detailed images of your brain and can show whether certain areas have become smaller or damaged, which is common in Huntington’s disease.^[9]

The images may reveal changes in a part of the brain called the striatum, which is deep inside the brain and plays a key role in controlling movement, mood, and behavior. The striatum is the area most affected by Huntington’s disease. However, these changes may not show up in the early stages of the disease. Brain imaging is also useful for ruling out other conditions that might be causing similar symptoms, such as a stroke or brain tumor.^[9]

Genetic Testing for Confirmation

The most definitive way to confirm a diagnosis of Huntington’s disease is through genetic testing. This test looks for a specific error, or mutation, in a gene called the HTT gene. This gene contains the instructions for making a protein called huntingtin, which is important for the normal functioning of brain cells. In people with Huntington’s disease, the HTT gene contains an abnormal expansion of a sequence called CAG trinucleotide repeats.^[6]

The genetic test is done using a blood sample. The laboratory analyzes your DNA to count how many CAG repeats are present in the HTT gene. People without Huntington’s disease typically have fewer than 27 repeats. If you have 40 or more repeats, you will develop Huntington’s disease at some point in your life. Having between 36 and 39 repeats means you may or may not develop symptoms. The more repeats you have, the earlier symptoms tend to appear.^[6]

Genetic testing can confirm the diagnosis if you already have symptoms that suggest Huntington’s disease. It can also be used as a predictive test if you have a parent with the condition but no symptoms yourself. This type of testing is sometimes called presymptomatic testing.^[5]

Genetic Counseling

Before undergoing genetic testing—especially predictive testing when you don’t yet have symptoms—you will typically meet with a genetic counselor. This specialist helps you understand what the test results might mean for you and your family. They will discuss why you want to be tested, what you hope to learn, and how the results could affect your life, relationships, and plans for the future.^[9]

Genetic counseling also provides emotional support. Learning that you carry the gene for Huntington’s disease can be overwhelming, even if you don’t have symptoms yet. A genetic counselor can help you think through the implications and connect you with resources and support groups. You must usually be 18 years or older to have predictive genetic testing, as it’s important that the decision is yours to make.^[5]

Diagnostics for Clinical Trial Qualification

If you’re considering participating in a clinical trial for Huntington’s disease, you’ll need to undergo additional testing beyond the standard diagnostic process. Clinical trials are research studies that test new treatments or approaches to managing the disease. They have strict rules about who can participate, known as inclusion and exclusion criteria, to ensure the safety of participants and the accuracy of the results.^[10]

One of the most important requirements for most Huntington’s disease clinical trials is genetic confirmation that you carry the altered HTT gene. If you haven’t already had genetic testing, this will be one of the first steps. The trial researchers need to know not only that you have the gene, but also how many CAG repeats you have, as this information helps predict disease progression and ensures the study includes participants at similar stages.^[6]

Disease Stage Assessment

Clinical trials often enroll people at specific stages of Huntington’s disease. Some trials focus on people who have the gene but haven’t developed symptoms yet, while others include only those who are already showing signs of the disease. To determine which stage you’re in, researchers use standardized rating scales and assessments.^[10]

One commonly used tool is the Unified Huntington’s Disease Rating Scale, which measures motor function (how well you move), cognitive function (how well you think), and behavioral and psychiatric symptoms. Your performance on these assessments helps researchers classify the severity of your disease and determine if you’re eligible for a particular trial.^[10]

Baseline Testing

Before you can join a clinical trial, researchers will perform a series of baseline tests to establish your current health status. This serves as a starting point for measuring any changes that occur during the trial. Baseline testing typically includes detailed neurological examinations, cognitive tests, brain imaging (such as MRI scans), and blood tests.^[10]

Blood tests may check your liver and kidney function, blood cell counts, and other markers of general health. These are important because some experimental treatments could affect these systems, so researchers need to know your starting values. Brain imaging provides a detailed picture of your brain structure at the beginning of the trial, allowing researchers to track any changes over time.^[10]

Functional and Quality of Life Assessments

Clinical trials also measure how Huntington’s disease affects your daily life and your ability to perform everyday tasks. You may be asked to complete questionnaires about your quality of life, independence, and ability to work, drive, manage finances, or care for yourself. These assessments help researchers understand whether a new treatment improves not just medical measurements but also real-world functioning.^[10]

Ongoing Monitoring

Once enrolled in a clinical trial, you’ll undergo regular testing throughout the study period. The frequency and types of tests depend on the specific trial, but they generally include repeated neurological exams, cognitive assessments, imaging scans, and blood work. This ongoing monitoring is essential for tracking how you respond to the treatment being tested and for identifying any potential side effects early.^[10]

Some recent clinical trials have tested experimental treatments like gene therapy, which involves complex procedures such as brain surgery to deliver the treatment directly to specific areas of the brain. These advanced trials require highly specialized testing and monitoring, including real-time MRI scanning during the procedure to guide the delivery of the treatment with precision. Follow-up assessments continue for months or even years after the treatment to evaluate its long-term effects.^[8]