Upper motor neuron lesion
| Upper motor neuron lesion | |
 | |
|---|---|
| The motor tract. |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
An upper motor neuron lesion is a lesion of the neural pathway above the anterior horn cell or motor nuclei of the cranial nerves. This is in contrast to a lower motor neuron lesion, which affects nerve fibers traveling from the anterior horn of the spinal cord to the relevant muscle(s).
Causes
Life Threatening Causes
- Cerebral palsy
- Cerebrovascular accident
- Cervical myelopathy
- Multiple sclerosis
- Spinal cord injury
- Stroke
- Traumatic brain injury
Common Causes
- Cerebral palsy,
- Cerebrovascular accident,
- Cervical myelopathy,
- Cervical spondylosis,
- Friedreich ataxia,
- Juvenile primary lateral sclerosis,
- Konzo,
- Motor neuron disease,
- Multiple sclerosis,
- Pseudobulbar palsy,
- Spastic paralysis,
- Spina bifida,
- Spinal cord injury,
- Subacute combined degeneration of the cord,
- Syringomyelia,
- Traumatic brain injury,
- Weber syndrome,
- X-linked sideroblastic ataxia,
Causes by Organ System
Causes in Alphabetical Order
Symptoms
- Spastic increase in tone in the extensor muscles (lower limbs) or flexor muscles (upper limbs)
- Clasp-knife response where initial resistance to movement is followed by relaxation
- Weakness in the flexors (lower limbs) or extensors (upper limbs),[1] but no muscle wasting
- Brisk tendon jerk reflexes
- Babinski sign positive, where the big toe is raised rather than curled downwards on stimulation of the sole of the foot
Corticospinal/pyramidal tract
These are the neural tracts which descend in the spinal cord, in the lateral columns, carrying signals for voluntary movement of skeletal muscle. These nerve fibres usually originate in the cerebral cortex, then gather in the internal capsule before crossing over to the opposite side (decussation) in the medulla oblongata and proceeding down the spinal cord to meet lower motor neurons in the anterior horn.