What Is It, Causes, Diagnosis, Treatment, and More
Author: Anna Hernández Castillo, MD
Illustrator: Aileen Lin
What is dysmetria?
Dysmetria is the inability to control the distance, speed, and range of motion necessary to perform smoothly coordinated movements. Dysmetria is a sign of cerebellar damage, and often presents along with additional signs, such as loss of balance and poor coordination of walking, speech, and eye movements. More specifically, dysmetria is a type of cerebellar ataxia, which is the general term used to describe an abnormal coordination of movements.
What causes dysmetria?
Dysmetria is a common finding seen in individuals with lesions of the cerebellum, which is the part of the central nervous system that integrates visual, spatial, and other sensory inputs with motor control in order to coordinate and plan movement as well as maintain balance. Damage to the nerves that carry sensory information to the cerebellum, or to the cerebellum itself, can lead to difficulty judging when and where movements should end; such difficulty can be described as undershooting or overshooting.
Cerebellar damage may result from a variety of causes, including traumatic brain injury, stroke, brain tumors, infection of the brain (encephalitis), cerebral palsy, autoimmune disorders, demyelinating disorders (such as multiple sclerosis), hereditary degenerative conditions of the nervous system (such as Friedreich’s ataxia or spinocerebellar ataxia), or metabolic diseases (for instance, thiamine or vitamin B12 deficiency).
How do you diagnose dysmetria? How do you treat dysmetria?
As part of the neurological examination, dysmetria can be diagnosed through a series of clinical tests that assess coordination. For instance, in the finger to nose test, an individual is asked to reach for the examiner’s finger with an outstretched arm and then touch their own nose several times. Another test is the heel to shin test, in which the individual is asked to place the heel of one foot on the shin of the other leg and then slide the heel down the shin towards the foot. A person without cerebellar ataxia will be able to perform these tests without difficulty, but people with dysmetria may have a hard time controlling the movement and may undershoot or overshoot their target, as well as make movement corrections along the way.
Treatment of dysmetria depends on the cause of cerebellar damage and the severity of the condition. Currently, there are no specific medications to cure dysmetria, but physical and occupational therapy can help strengthen muscles and improve motor function. Additionally, some tools can be used to assist in daily activities, such as weighted tools and utensils to facilitate eating and self-care.
What are the most important facts to know about dysmetria?
Dysmetria is the inability to control the distance, speed and range of motion necessary to perform smoothly coordinated movements. It can be seen in individuals with cerebellar damage due to brain trauma, brain tumors, metabolic diseases, and demyelinating or degenerative disorders. Dysmetria can be demonstrated by clinical tests to assess coordination, such as the finger to nose test and heel to shin test. Currently, there’s no specific treatment to cure dysmetria, although physical and occupational therapy can be useful to improve quality of life.
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Resources for research and reference
Marsden, J. and Harris, C. (2011). Cerebellar ataxia: pathophysiology and rehabilitation. Clinical Rehabilitation, 25(3): 195–216. DOI: 10.1177/0269215510382495
Stephen, C. D., Brizzi, K. T., Bouffard, M. A., et al. (2019) The Comprehensive Management of Cerebellar Ataxia in Adults. Current Treatment Options in Neurology, 21(9). DOI: 10.1007/s11940-019-0549-2