Introduction: Who Should Undergo Diagnostics and When

If you notice unusual, uncontrollable movements in yourself or a loved one—especially slow, twisting motions of the hands, feet, arms, or face—it may be time to seek medical evaluation. Athetosis is not a disease by itself but a symptom of an underlying condition, often linked to damage in specific areas of the brain.^[1] This means that recognizing the signs early and pursuing proper diagnostics can make a meaningful difference in understanding what is happening and planning appropriate care.

Parents often notice the first signs of athetosis in infants and young children when developmental milestones are delayed. A baby may struggle to sit up, grasp objects, or coordinate movements. These writhing movements may not be obvious at birth; they can emerge gradually, sometimes becoming more noticeable by 18 months or later.^[11] In some cases, the movements worsen during childhood and adolescence, particularly during times of stress or when the child attempts to perform intentional actions like reaching for a toy or speaking.^[1]

Anyone experiencing new or worsening involuntary movements should seek medical attention. This includes not only children but also adults who develop symptoms later in life due to stroke, brain injury, or certain medications. Early diagnostic evaluation is especially important because athetosis can be associated with serious underlying conditions—such as brain damage from lack of oxygen at birth, severe jaundice in newborns, or degenerative brain diseases—that may require specific treatment or monitoring.^[2][5]

If you are a parent, caregiver, or patient, you should consider seeking diagnostics when you notice slow, continuous, worm-like movements that are involuntary and cannot be stopped at will. These movements typically worsen when the person tries to control them—for example, trying to type on a keyboard or hold a spoon can make the writhing motions more pronounced.^[1] Other warning signs include difficulty standing, problems with speech, drooling, or challenges with feeding and swallowing. The earlier these symptoms are recognized and evaluated, the sooner supportive therapies can begin.

Diagnostic Methods for Identifying Athetosis

Diagnosing athetosis involves a careful, step-by-step process. Because athetosis is a symptom rather than a disease, doctors must work to identify what is causing the abnormal movements. This process typically begins with a detailed medical history and a thorough physical examination, followed by specialized tests to look inside the body and assess brain function.

Medical History and Physical Examination

The first step in diagnosing athetosis is gathering a complete medical history. Your doctor will ask questions about when the symptoms started, how they have changed over time, and whether there were any complications during pregnancy or birth. For infants and children, the doctor will want to know if there were any problems such as lack of oxygen during delivery, severe jaundice, prematurity, or low birth weight—all of which are known risk factors for brain injury that can lead to athetosis.^[5][9]

During the physical examination, the doctor observes the patient’s movements closely. Athetosis is characterized by slow, writhing, and continuous motions, often affecting the fingers, hands, feet, arms, legs, face, tongue, and neck.^[1][4] The doctor will watch how the movements change when the patient is at rest versus when they try to perform a task. A key feature of athetosis is that the movements typically get worse with voluntary effort—such as trying to reach for an object or speak—and may lessen or disappear during sleep.^[1]

The doctor will also assess muscle tone, posture, coordination, and reflexes. People with athetosis often have fluctuating muscle tone, meaning their muscles may shift unpredictably between being very loose and very tight. This makes it hard to maintain a stable, symmetrical posture.^[1][9] The examination may reveal difficulties with balance, standing, and walking, as well as problems with fine motor skills like grasping small objects.

Imaging Tests to Examine the Brain

Once the doctor suspects athetosis based on the history and physical exam, imaging tests of the brain are usually the next step. These tests allow doctors to see inside the brain and identify areas of damage or abnormality that could be causing the symptoms.

Magnetic resonance imaging (MRI) is one of the most commonly used imaging tests. MRI uses magnets and radio waves to create detailed pictures of the brain’s soft tissues. It can reveal damage to the basal ganglia—a group of structures deep in the brain that control movement—as well as the thalamus, which is closely connected to the basal ganglia. Damage to these areas is the most common cause of athetosis.^[3][5][9]

Computed tomography (CT) scans may also be used, especially in emergency situations or when MRI is not available. CT scans use X-rays to create cross-sectional images of the brain. While not as detailed as MRI for soft tissue, CT scans can quickly detect bleeding, stroke, or major structural problems in the brain.^[20]

In some cases, doctors may use other imaging techniques, such as positron emission tomography (PET) scans or specialized nuclear medicine tests, to assess how different parts of the brain are functioning. These tests can show whether certain brain regions are less active or using less energy than normal, which may help pinpoint the cause of athetosis.

Laboratory Tests and Additional Evaluations

Blood tests and other laboratory evaluations are often performed to rule out or confirm specific underlying causes of athetosis. For example, if a newborn has severe jaundice, blood tests can measure the level of bilirubin, a substance that can damage the basal ganglia if it becomes too high. This condition, called kernicterus, is a known cause of athetoid cerebral palsy.^[5][9]

Other blood tests may check for metabolic disorders, genetic conditions, or infections that could affect the brain. For instance, Wilson’s disease—a rare hereditary disorder that causes copper to build up in the body—can lead to athetosis and other movement problems.^[11] Doctors may also test for thyroid problems, autoimmune diseases, or exposure to certain toxins or medications that are known to cause movement disorders.^[10]

If there is concern about inherited conditions, genetic testing may be recommended. Some cases of athetosis occur as part of genetic syndromes like Huntington’s disease, a progressive brain disorder that runs in families.^[4][11]

Electroencephalogram (EEG) and Other Neurological Tests

An electroencephalogram (EEG) is a test that records the electrical activity of the brain using small sensors placed on the scalp. While EEG is not used to directly diagnose athetosis, it can help rule out other conditions—such as epilepsy—that may cause abnormal movements or developmental delays. Some children with athetosis also have seizures as a complication, so EEG may be part of the diagnostic workup.^[9][19]

Other tests, such as electromyography (EMG) and nerve conduction studies, measure how well nerves and muscles are working. These tests are more commonly used to diagnose other types of movement disorders or nerve damage, but they can help doctors distinguish athetosis from conditions like peripheral nerve injury or muscle disease.

Developmental and Functional Assessments

For children, developmental assessments are an important part of the diagnostic process. Specialists such as pediatric neurologists, developmental pediatricians, or physical and occupational therapists will evaluate whether the child is meeting age-appropriate milestones for movement, communication, and cognitive skills. Delays in sitting, crawling, walking, or using the hands can be early signs of athetosis and related conditions.^[5][9]

Functional assessments also help doctors understand how athetosis affects daily life. They may observe how the child or adult performs specific tasks—such as reaching for objects, walking, eating, or speaking—and measure the severity of the involuntary movements. This information is valuable for planning therapy and tracking progress over time.

Distinguishing Athetosis from Similar Conditions

Because athetosis shares features with other movement disorders, part of the diagnostic process involves distinguishing it from conditions like chorea and dystonia. Chorea is characterized by brief, irregular, dance-like movements, while athetosis involves slower, more flowing, writhing motions. Sometimes these two conditions occur together, a situation called choreoathetosis.^[1][10]

Dystonia involves involuntary muscle contractions that cause twisting, repetitive movements and abnormal postures. While both dystonia and athetosis can make it hard to maintain a normal posture, dystonia tends to involve more sustained, fixed positions, whereas athetosis is more fluid and continuous.^[1]

Careful observation by an experienced neurologist is often the key to making these distinctions. Video recordings of the patient’s movements can also be helpful for review and consultation with specialists.

Diagnostics for Clinical Trial Qualification

When patients with athetosis are being considered for enrollment in clinical trials, additional diagnostic tests and criteria may be required. Clinical trials are research studies designed to test new treatments or therapies, and they often have strict eligibility rules to ensure that participants are suitable and that results are accurate and meaningful.

Confirming the Diagnosis and Underlying Cause

Before a patient can join a clinical trial, researchers need to confirm the diagnosis of athetosis and identify the underlying cause. This typically involves the same diagnostic steps used in routine clinical practice—such as MRI or CT imaging to document damage to the basal ganglia, blood tests to rule out metabolic or genetic disorders, and detailed medical history to understand the origins of the movement disorder.^[5][9]

For trials focused on specific conditions—such as athetoid cerebral palsy or Huntington’s disease—there may be additional requirements, such as genetic testing or specific imaging findings that prove the patient has that particular disorder.

Assessing Severity and Functional Status

Clinical trials often require standardized assessments to measure the severity of athetosis and its impact on daily functioning. These assessments help researchers determine whether a patient meets the inclusion criteria and provide baseline data to measure whether the treatment is working.

For children with athetoid cerebral palsy, doctors may use classification systems such as the Gross Motor Function Classification System (GMFCS), which rates a child’s ability to move and perform physical activities on a scale from level I (least impaired) to level V (most impaired). Similar rating scales may be used to assess fine motor skills, speech, and self-care abilities.^[9]

For adults or older children, functional tests might include timed tasks—such as walking a set distance, picking up small objects, or completing writing exercises—to objectively measure the degree of movement impairment.

Excluding Other Conditions

Clinical trials often exclude patients who have other medical conditions or complications that could interfere with the study results or put the patient at risk. For example, a trial testing a new medication for athetosis might exclude individuals who have severe epilepsy, uncontrolled infections, heart disease, or other serious health problems.^[9]

Diagnostic tests to rule out these exclusions may include blood tests to check organ function, EEG to assess for seizures, echocardiograms to evaluate heart health, and imaging studies to ensure there are no tumors or other unexpected findings in the brain.

Biomarker and Laboratory Testing

Some clinical trials may require specific biomarker testing—measurements of substances in the blood, urine, or cerebrospinal fluid that indicate disease activity or severity. For example, trials investigating treatments for Huntington’s disease might measure levels of certain proteins or genetic markers that are associated with the progression of the disease.^[11]

In trials for athetoid cerebral palsy, researchers might collect blood samples to study genetic variations, immune system markers, or other biological factors that could influence how well a patient responds to treatment.

Informed Consent and Ethical Considerations

Before enrolling in a clinical trial, patients or their legal guardians must provide informed consent. This means they receive detailed information about the purpose of the study, the tests and procedures involved, potential risks and benefits, and their right to withdraw at any time. For children or individuals who cannot make their own decisions, consent is provided by a parent or guardian, and the patient’s assent (agreement) is also sought when appropriate.

Ethical guidelines require that all diagnostic tests performed as part of a clinical trial are necessary for the study and do not expose participants to unnecessary harm. Institutional review boards and ethics committees review and approve all trial protocols to protect participants’ rights and safety.