Why do UMN lesions cause Hypertonia?

Hypertonia is caused by upper motor neuron lesions which may result from injury, disease, or conditions that involve damage to the central nervous system. The lack of or decrease in upper motor neuron function leads to loss of inhibition with resultant hyperactivity of lower motor neurons.

Why does pure pyramidal tract lesion cause hypotonia?

Pure corticospinal tract lesion cause hypotonia instead of spasticity The reason is that pure pyramidal tract lesion is very very rare, and spasticity is due to loss of inhibitory control of extrapyramidal tract. Increased Gamma efferent discharge is the main cause of increased muscle tone.

What causes UMN signs?

Causes

• Lou Gehrig’s disease (amyotrophic lateral sclerosis, or ALS)
• Primary lateral sclerosis (PLS)
• Traumatic brain injury.
• Spinal cord injury.
• Multiple sclerosis.
• Stroke.
• Huntington’s disease.

What causes an upper motor neuron lesion?

Upper motor neuron lesions occur in the brain or the spinal cord as the result of stroke, multiple sclerosis, traumatic brain injury, cerebral palsy, atypical parkinsonisms, multiple system atrophy, and amyotrophic lateral sclerosis.

What causes upper motor neuron lesion?

What are the signs of an upper motor neuron lesion?

Damage to upper motor neurons leads to a group of symptoms called upper motor neuron syndrome:

• Muscle weakness. The weakness can range from mild to severe.
• Overactive reflexes. Your muscles tense when they shouldn’t.
• Tight muscles. The muscles become rigid and hard to move.
• Clonus.
• The Babinski response.

Why do UMN lesions cause Hyperreflexia?

Hyperreflexia. Because of the loss of inhibitory modulation from descending pathways, the myotatic (stretch) reflex is exaggerated in upper motor neuron disorders. The stretch reflex is a major clinical diagnostic test of whether a motor disorder is caused by damage to upper or lower motor neurons.

What is the difference between hypotonia and Hypertonia?

Hypotonia causes decreased muscle tone and increased flexibility, making the body seem floppy or limp. Hypertonia is also known as “floppy infant syndrome”. A child with hypotonia will have problems lifting their limbs and performing fine and gross motor activities.

Why does cerebellar lesions cause hypotonia?

It is typically seen with acute hemispheric lesions and is often accompanied by hyporeflexia. Hypotonia likely results from decreased fusimotor activity resulting in decreased muscle spindle afferent response. It is usually a transient phenomenon after an acute lesion but can be seen in chronic lesions as well.

What is an UMN lesion?

UMN lesions are designated as any damage to the motor neurons that reside above nuclei of cranial nerves or the anterior horn cells of the spinal cord. Damage to UMN’s leads to a characteristic set of clinical symptoms known as the upper motor neuron syndrome.