Upper and Lower Motor Neurons
The cell bodies of most UMNs are located in this anatomical region.
Primary motor cortex (pre-central gyrus)
Most corticospinal fibers decussate in this anatomical location.
The medullary pyramids
Trauma at the level of C3 that damages the lateral corticospional tract will present with these symtpoms:
Ipsilateral weakness of arms and legs.
Loss of inhibitory input onto LMNs leads to this hallmark UMN lesion sign.
Hyperreflexia
This structure is formed from densely-packed fibers of the corona radiata traveling inferiorly from the motor cortex toward the midbrain.
Internal capsule
An infarct to the left posterior internal capsule will present with these symptoms.
Right-sided hemiparesis (right face, arms, legs)
This term describes a single lower motor neuron plus all the muscle fibers that it innervates.
Motor unit
This pathology presents as a "stocking-glove" distribution.
Peripheral neuropathy
This spinal cord syndrome causes ipsilateral loss of motor function and proprioception with contralateral loss of pain and temperature below the lesion.
Brown Séquard Syndrome
Bundles of UMN axons descending from the cortex are referred to by this term before entering the internal capsule.
Corona radiata
This anterior midbrain structure carries descending UMN fibers.
A small right ACA stroke would present with motor symptoms in this area.
Left lower limb
In patients with an UMN lesion, flicking of the distal phalanx of the middle finger results in this involuntary response.
Flexion of thumb and index finger (Hoffman's Sign)
Corticospinal UMNs innervate the cell bodies of LMNs within this structure.
Ventral/anterior horn of the spinal cord
Contralateral limb weakness, internuclear ophthalmoplegia, and ipsilateral tongue deviation is characteristic of this brainstem syndrome.
Medial medullary syndrome (Dejerine Syndrome)