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Hypermetria and Dysmetria in Cats

Dysmetria and hypermetria describe the incoordination of an animal's limbs during voluntary movement. More specifically, dysmetria is characterized by a cat's inability to judge the rate, range, and force of its movements -- literally, an inability to measure space. Hypermetria, meanwhile, describes the action of overreaching, or high stepping, the intended location.

Symptoms and Types

Signs of cerebellar disease that may be present include:

• Head tilt
• Body swaying
• Body tremors; often more pronounced with movement
• Wide leg stance
• Loss of the menace response – the reflexive closing of the eyes when a finger is stabbed toward the eye
• Unequal pupil size (anisocoria)
• Abnormal, jerky movements

Causes

Trauma to the brain or back is often the primary cause for spinal or brain injury, leading to incoordination or overreaching of the  limbs. Lesions on the cerebellum, the part of the brain that is responsible for coordinating voluntary movements and balance, or on the nerves leading to the cerebellum, are believed to be one of the causes for these symptoms. Lesions can be caused by strokes, or by tumors located near these nerves.

Diagnosis

Your veterinarian will perform a thorough physical exam on your cat, taking into account the background history of symptoms and possible incidents that might have led to this condition. If there are no other signs of cerebellar disease, it will be important to establish whether a high-stepping thoracic limb gait is physically normal for your cat. Diagnostic imaging, such as with X-ray or ultrasound, is generally performed to review possible injury or damage to the brain and spine, and is especially recommended for older animals.

Your veterinarian will check your cat's reactions and responses to stimulus, such as whether your cat responds when your veterinarian stabs a finger toward the its eyes. The reflexive closing of the eyes and jerking away is called the menace response, or menace reflex, and the lack of such of a response is indicative of loss of eye sight, or neurological dysfunction.