Dysmetria is an impaired ability to control the speed, distance, or range of physical movement. People with dysmetria may overshoot or undershoot their movements. They may also have difficulty with balance or with coordinating speech and eye movements.
The condition occurs due to damage in the cerebellum, which is part of the brain. Dysmetria is a type of ataxia, which is the general term for difficulties with coordination.
A doctor can ask a person to perform physical tests to determine whether a person has dysmetria, while scans, such as an MRI, may help with identifying the cause. Treatment aims to improve symptoms and includes physical therapy.
Read on to learn more about dysmetria, including the symptoms, causes, and outlook.
Dysmetria is a loss of ability to control and coordinate movement. It is a type of ataxia, a group of disorders that affect a person’s coordination, balance, and speech.
People with dysmetria have difficulty controlling the speed, distance, and range of motion of their movements. They may undershoot or overshoot their movements. These individuals can also have ocular dysmetria, which affects eye movements.
Dysmetria can be progressive, meaning its symptoms get more pronounced over time.
One of the main symptoms of dysmetria is a loss of ability to move with the right amount of speed or distance. This does not occur because a person has accidentally misjudged their movement but because the brain is not coordinating movement as it should.
Dysmetria can involve:
- Hypometria: This is when a person undershoots their movements. For example, they may try to reach something and miss it because their hand is not close enough.
- Hypermetria: This is the opposite of hypometria, meaning a person overshoots their movements. When trying to reach for an object, their hand may reach past the object.
- Ocular dysmetria: This refers to difficulty controlling eye movements. A person’s eyes may switch objects and need to move a second time to catch up. Doctors call this condition hypometric saccades. Alternatively, the eyes need to correct an overshoot to focus on the desired object — healthcare professionals call this hypermetric saccades.
- Other forms of ataxia: People with dysmetria may also experience difficulties with balance, walking, and speech.
Due to these difficulties, a person with dysmetria may make multiple corrections to their movements to try and make them more precise.
Dysmetria occurs due to an injury in the cerebellum or nerves that connect to the cerebellum. This is part of the brain that processes visual, spatial, and other sensory inputs to coordinate and plan movements. The cerebellum also helps a person maintain balance.
Conditions and injuries that can damage the cerebellum include:
- traumatic brain injury
- brain tumor
- encephalitis, or inflammation of the brain
- cerebral palsy
- autoimmune disorders
- demyelinating disorders, such as multiple sclerosis, which damage the protective sheath surrounding the nerves
- inherited degenerative conditions of the nervous system, such as Friedreich’s ataxia and spinocerebellar ataxia
- metabolic diseases, including thiamine (vitamin B1) or vitamin B12 deficiency
Doctors can run a series of coordination tests to determine if a person has dysmetria. These include the following:
- Finger to nose test: During this test, a doctor asks the person to reach for the doctor’s finger with an outstretched arm. They then ask them to touch their own nose several times.
- Heel to shin test: In this test, a doctor asks the person to place the heel of one foot on the shin of the other leg and slide it down the shin toward the foot.
A person without an injured cerebellum should be able to complete these tasks easily. However, someone with dysmetria may have difficulties controlling their movement. They may also need to correct themselves while trying.
Doctors can also use an MRI scan to assess the brain. This can not only help with making a diagnosis but also with monitoring disease progression, if relevant. People who may have an inherited condition may also require genetic tests.
The underlying cause and severity of the damage to the cerebellum determine how a doctor treats a person with dysmetria.
There are no specific medications that treat or cure dysmetria. However, someone can strengthen their muscles and improve their motor function through physical and occupational therapy.
Physical therapy focuses on strengthening muscles via special exercises that a physical therapist tailors to a person’s needs. Occupational therapy focuses on adapting the home, workplace, and a person’s routines to make living with a condition easier. This may involve:
- switching to weighted tools and utensils such as cutlery
- using voice-activated software on phones and computers
- removing tripping hazards
- changing the layout of desks, workspaces, or the home to make it easier to move around
- opting for devices, light switches, and appliances with large buttons
- using nonslip mats while working, cooking, or eating
- choosing cups with lids and straws to prevent spilling
These are just a few adjustments that can enable someone to carry out everyday activities themselves. An occupational therapist can put together an individual plan and provide support with implementing it.
Because dysmetria can be progressive, a person’s needs may change over time. For example, they may initially find their symptoms do not affect their ability to drive, but others may find driving is no longer safe.
A person may need to discuss plans for the future with their healthcare team to make sure there is additional support in place when they need it.
According to a 2019 study, many people with progressive ataxia have a typical life expectancy. Doctors may be able to help a person improve the symptoms of dysmetria by treating the underlying cause.
In the absence of a cure, doctors can recommend treatments and support above to help a person manage their condition.
Ataxia can have a significant effect on a person’s quality of life and mental health. Some people may benefit from speaking with a therapist or counselor with experience helping people with long-term health conditions.
Additionally, support groups can allow individuals to connect with others who have had similar experiences. The National Ataxia Foundation offers support groups across the United States.
A person with dysmetria has difficulty controlling the distance and speed of their movements and their range of motion. Traumatic brain injury, stroke, brain tumors, and a range of other conditions can cause dysmetria.
Doctors test for the condition using specific physical tests, such as the finger to nose test and the heel to shin test, and MRI scans. Treatments for dysmetria include physical therapy to strengthen muscles and occupational therapy to improve quality of life and independence.