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Upper Motor Neuron Lesion
Aka: Upper Motor Neuron Lesion, Upper Motor Neuron Deficit, Upper Motor Neuron
- See Also
- Motor Exam
- Lower Motor Neuron Deficit
- Physiology
- Corticospinal tract (motor, lateral cord) transmits motor signals from the cerebral cortex
- Fibers cross the midline at the Brain Stem and course to the contralateral muscles
- Motor fibers Synapse in the anterior horn (grey matter of the spinal cord)
- Upper Motor Neurons (UMN) are from the cerebral cortex to the Synapse
- Affect the cerebral cortex, Brainstem and Corticospinal tracts
- Lower Motor Neurons (LMN) are from the Synapse to the muscle
- Affect the anterior horn (spinal cord), nerve roots, and peripheral nerves
- Causes: Examples
- See Muscle Weakness
- CNS Lesion
- Spinal Cord Syndrome
- Multiple Sclerosis
- Signs: Upper Motor Neuron Lesion findings
- Muscle group weakness (not complete paralysis)
- Minimal muscle atrophy
- "Clasp-knife" spasticity
- Initial resistance to motion is strongest
- Once initial resistance gives-way, resistance to motion is less for remaining range of motion
- Hyperreflexia with or without Clonus
- Babinski Reflex positive response
- Pathologic spread of reflexes
- Muscle contractions produce motions in muscles other than the one tested
- Precaution
- Cauda equina are all peripheral nerves
- Upper Motor Neuron findings for levels below T12 or L1 must be central lesions in the higher cord
- Strongly consider severe Cervical Spinal Stenosis
- Reference
- Robbins (2012) Board Review Express, San Jose