Upper Motor vs. Lower Motor Neuron Disease: All the neurons supplying to the pyramidal and extrapyramidal systems are upper motor neurons (UMN). The anterior horn cells and the associated neurons in the motor nuclei of some cranial nerves are lower motor neurons (LMN).
Upper Motor Neuron Disease
- Reflexes are hyperactive in this motor neuron disease.
- Fasciculations are absent in this motor neuron disease.
- Atrophy may be mild from disuse in this motor neuron disease.
- The Hypertonic tone in this motor neuron disease.
Upper Motor Neuron Disease Characterized
A lesion found in descending motor tracts within the cerebral motor cortex, internal capsule, brainstem or the spinal cord.
Upper Motor Neuron Disease Symptoms
The weakness of involved muscles, hyperreflexia, hypertonicity, mild disuse atrophy, and abnormal reflexes; damaged tracts are in the lateral white column of the spinal cord. (Remember: all symptom are higher)
Upper Motor Neuron Disease Examples
Cerebral palsy, CVA, hydrocephalus, birth injuries, multiple sclerosis, and tumors in the brain.
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Lower Motor Neuron Disease
- Reflexes are diminished or absent in this motor neuron disease.
- Fasciculations are present in this motor neuron disease.
- Atrophy is present in this motor neuron disease.
- Hypotonic to flaccid tone in this motor neuron disease.
Lower Motor Neuron Disease Characterized
A lesion that affects nerves or their axons at or below the level of the brainstem, usually within the “final common pathway”.
Lower Motor Neuron Disease Symptoms
Flaccidity or weakness of the involved muscles decreased tone, fasciculations, muscle atrophy and decreased or absent reflexes. (Remember: all symptom are lower)
Lower Motor Neuron Disease Examples
Poliomyelitis, tumors involving the spinal cord, infection, trauma, and muscular dystrophy.