EXTRA PYRAMIDAL SYSTEM Flashcards
Tectospinal tract
brainstem (tectum of midbrain)–> crosses the midline –> passes medulla –> anterior grey horn of the SC
Function of the Tectospinal tract
thought to mediate reflex head and neck movement due to visual stimuli
define reticulum
a network of interconnected nuclei embedded loosely in the brainstem
reticulospinal tract and functions
fibres originate from the areas off reticular formation in pons and MO
fibres from pons facilitate extensor movements and inhibit flexor movements
fibres from MO –> opposite function
Vestibulospinal tract pathway and function
fibers originate in the vestibular nuclei of the pons and medulla
fibers descend down the brainstem to the appropriate spinal cord segment
NO CROSSING
excitatory input to ‘antigravity” muscles
consequences of brainstem lesion at the level of midbrain
lack of descending tract and other tracts –> domination of the extensor muscle tone & hyperextended spastic paralysis.
Hemisection of the Spinal Cord aka brown-Sequard’s Syndrome (BSS)
a rare spinal disorder that results from an injury to one side of the spinal cord in which the spinal cord is damaged but not severed completely.
causes of BSS
injury to the spine in the region of back or neck
eg: from puncture wound, gun shot
other spinal disorders such as cervical spondylosis, arachnoid cysts, or epidural hematoma
Sensory consequences of BSS
Injury to Dorsal column tract –> ipsilateral loss of two point discrimination, fine touch, conscious proprioception and vibration (bc fibres have not yet crossed, they only cross at the MO)
Injury to STT –> contralateral loss pf deep pressure, pain and temperature (bc fibres have already crossed at the SC level)
Motor consequences of BSS
Injury to CST
dominant Lateral CST –> ipsilateral paralysis
less dominant Anterior CST –> contralateral paralysis
