Dysmetria is a lack of coordination of body movement caused by damage to the cerebellum or its neural pathways. It can be diagnosed through simple tests and managed with medication, but a complete cure is not possible. Experimental treatments include cannabis and chiropractic neurology.
Dysmetry is a lack of coordination of body movement, in which a person appears to over- or under-estimate distance with their eyes, hands, or legs. The condition is often not just a motor dysfunction, but a cognitive one. Hypermetry is overcoming the distance, such as when a person reaches farther than expected, while hypometry is overcoming the distance.
The cerebellum is the part of the brain responsible for motor coordination, and dysmetria can occur if it or one of its neural pathways is damaged. The cerebellum receives visual and spatial information from the eyes and sends corresponding motor information to the limbs. Dysmetria is caused by lesions on the cerebellum, or in the nerves connected to the cerebellum, and is often associated with other cognitive disorders of the cerebellum, including symptoms such as speech impairment and problems with reasoning and memory. Associated disorders include amyotrophic lateral sclerosis (ALS), autism, autosomal dominant spinocerebellar ataxia (ACS), multiple sclerosis (MS), schizophrenia, and stroke.
Motor dysmetria occurs when a person is unable to correctly interpret the position of their extremities in space. It is often characterized by an inability to make rapid tapping or other coordinated movements of the extremities. Saccadic dysmetry is characterized by abnormal eye movements, including twitching of the eye at rest. Ocular dysmetry is characterized by gaze and focusing problems, overestimation or underestimation of the distance with the eyes.
The first step in diagnosing dysmetria is usually a simple hand-to-nose test, in which the doctor holds up a finger in front of the patient and the patient is asked to touch the doctor’s finger and then their own nose, several times. Similar tests can be used to examine the coordinated movement of the arms and legs. If such tests suggest motor problems, magnetic resonance imaging (MRI) can be used to locate lesions in the brain and make a more robust diagnosis.
Since dysmetria is a symptom, it can only be cured if the underlying cause is treated. In most cases, a complete cure is not possible. However, the condition can be managed through medications such as isoniazid and clonazepam.
More experimental treatments include cannabis and chiropractic neurology. Research is also investigating the utility of eye movement testing, in which the patient is trained to practice eye movements before attempting the physical movement. Deep brain stimulation (DBS) can help improve the motor skills of multiple sclerosis patients.
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