The cell bodies of the pyramidal tract concentrate around the motor area of the cerebral cortex. Corticospinal tract fibers synapse with spinal nerves while corticobulbar fibers synapse with cranial nerves. The pyramidal tract divides into the corticospinal tract and the corticobulbar tract. The pyramidal tract provides a direct pathway between the cerebral cortex and the spinal cord, in contrast with extra-pyramidal tracts which provide indirect pathways for the coordination of movement. The major UMN tract that initiates voluntary movement is the pyramidal tract. Various descending UMN tracts are responsible for the coordination of movement. Upper motor neurons are first-order neurons which are responsible for carrying the electrical impulses that initiate and modulate movement. UMN’s lesions have a wide differential diagnosis which ranges from cerebrovascular accidents, traumatic brain injury, malignancy, infections, inflammatory disorders, neurodegenerative disorders, and metabolic disorders. These symptoms can include weakness, spasticity, clonus, and hyperreflexia. Damage to UMN’s leads to a characteristic set of clinical symptoms known as the upper motor neuron syndrome. 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. Injury or lesions to UMN’s are common because of the vast areas covered by the motor neuron pathways. The pyramidal tract divides further into the corticospinal tract and the corticobulbar tract. The primary tract which carries signals for voluntary movement is known as the pyramidal tract. The nerves in the CNS which carry the impulses for movement are known as upper motor neurons (UMN). A vast network of nerve tracts in the central nervous system (CNS) which spans the cerebral cortex, brainstem, cerebellum, and spinal cord control the initiation and modulation of movements.
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