Lecture 11 Flashcards
conus medullaris
the termination of spinal cord located at T12/L1 vertebra in an adult
cauda equina
the lumbosacral nerve roots that descend in lower vertebral canal and sacral canal
lumbar cistern
enlargement of the subarachnoid space that is located distal to the conus medullaris
- contains cerebrospinal fluid and the cauda equina nerve roots
filum terminale
interna = a continuation of pia that extends to “bottom” of the lumbar cistern
externa = a continuation of dura that extends to the coccyx bone
denticulate ligaments
pia extension anchor spinal cord to arachnoid/dura layers
dorsal nerve root
sensory input FROM peripheral nerve
ventral nerve root
motor output TO peripheral nerve
gray matter
“H” shape located in the middle of a spinal cord cross section that contains nuclei/unmyelinated nerve fibers
grey matter - posterior horn
receives sensory input from the body - sensory (afferent) neurons of the dorsal nerve root terminate in the dorsal horn
gray matter - anterior horn
contains cell bodies of ventral nerve root neurons that exits out the ventral nerve root (lower motor neurons)
lower motor neuron lesion
damage to the motor pathways in the anterior horn of the spinal cord
muscle tone = hypotonia
reflexes = hyporeflexia
weakness = flaccid paralysis
atrophy = quick atrophy
white matter
contains myelinated ascending sensory tracts and descending motor tracts of the spinal cord
white matter - sensory function
ascending tracts in the white matter transmit sensory information from body up to the brainstem, cerebellum, dicephalon, and cerebrum
white matter - motor function
descending tracts in the white matter transmit motor information from cerebrum and brainstem to the muscles of the body
white matter - posterior (dorsal) column
location: posterior of the “H”
motor: no motor tracts
sensory: 1 sensory tract that carries proprioception, discriminating touch and vibration information
white matter - lateral column
location: lateral to the “H”
motor: contains 2 lateral motor tracts
sensory: contaisn 2 sensory tracts that carry pain/temp information and unconscious proprioception information
white matter - anterior (ventral) column
location: anterior to the “H”
motor: contains the “medial motor tracts”
sensory: contains a sensory tract that carries pain/temp information
anterior spinal artery
“single” artery that descends anteriorly along the length of the spinal cord
originates: R/L vertebral arteries, various segmental branches at different levels of the spinal cord
supplies anterior 2/3 of spinal cord (lateral and anterior columns)
posterior spinal arteries (R/L)
descend posteriorly along the length of the spinal cord
originate: small branches of the vertebral arteries, various segmental branches at different levels of the spinal cord
supply posterior 1/3 of spinal cord (posterior column)
lateral corticospinal tract function
controls fine motor movement of distal extremities
lateral corticospinal tract pathway
motor cortex output -> internal capsule -> ipsilateral anterior brainstem
- cross midline (decussate) in lower medulla (pyramids)
- descend in the lateral column of spinal cord
- TERMINATE on the anterior horn motor neurons that supply the UE/LE muscles
lateral corticospinal tract - lesion ABOVE medulla
stroke/tumor of motor cortex, internal capsule or anterior brainstem
CONTRALATERAL hemiparesis
lateral corticospinal tract - lesion BELOW medulla
spinal cord injury or MS/ALS in lateral spinal cord
IPSILATERAL hemiparesis below lesion
rubrospinal tract function
- supportive role of lateral corticospinal tract (fine motor movement)
- promotes UR flexors and inhibits UE extensord
- function is more involved in upper extremities vs, lower extremities
rubrospinal tract pathway
originates in red nucleus of the midbrain
descends in lateral column of spinal cord just anterior to lateral corticospinal tract
terminates on anterior horn motor neurons that supply the UE/LE muscles
rubrospinal tract lesion
lesions involving the red nucleus itself influence abnormal posturing responses known as decorticate and decerebrate
decerebrate
brainstem involving the red nucleus and BELOW
decreased UE flexor tone and allowes UE extensor tone to dominate
*more severe and worst prognosis
decorticate
brainstem damage ABOVE the red nucleus
excessive flexor tone of UE and allows excessive UE flexor tone to dominate
medial (anterior) motor tracts are involved in axial (trunk)/proximal limb control/balance
anteromedial corticospinal tract
tectospinal tract
reticulospinal tract
vestibulospinal tract - lateral/medial
anterior (medial) corticospinal tract function
control and maintain axial/proximal limb voluntary movement
anterior (medial) corticospinal tract pathway
motor cortex to brainstem
DOES NOT cross midline in medulla
descends in anteromedial spinal cord
terminates near medial ventral horn of most levels of spinal cord
tectospinal tract function
visual reflexes/coordination of head and eye movement
reflexive reactions to visual input
tectospinal tract pathway
originates in superior colliculi of midbrain -> crosses immediately -> descends in anteromedial spinal cord -> terminates in anterior horn cervical spine
supplies postiral muscles of head/neck
reticulospinal tract function
modulates reflexive/automatic motor movements related to posture/gait
reticulospinal tract pathway
originates in reticular nuclei in lower 2/3 of brainstem -> descends in anteromedial spinal cord -> terminates on motor nuclei in the anterior horn in all levels of spinal cord
does NOT cross
medial vestibulospinal tract function
control head and neck movement/posture
medial vestibulospinal tract pathway
begins medial vestibular nuclei or medulla -> descends in aneromedial spinal cord BILATERALLY -> terminates on motor nuclei of the neck muscles located in the anterior horn of cervical spinal cord
vestibulospinal tract only found in cervical spine
lateral vestibulospinal tract function
maintain balance and extensor tone
lateral vestibulospinal tract pathway
begins lateral vestibular nuclei of medulla -> descends in anteromedial spinal cord -> terminates on motor nuclei of antigravity (extensor) muscles located in the anterior horn in all levels of spinal cord
corticobulbar tract function
contralateral voluntary motor movement of the lower facial muscles (lower CN 7) and tongue (CN 12)
bilateral voluntary motor movement of upper face/mouth/pharynx/larynx muscles
corticobulbar tract pathway
begins in the primary motor cortex -> descends through the internal capsule -> descend in the anterior brainstem and terminates on the motor nuclei of CN 5, 7,10, and 12
corticobular tract CN 7
upper face - BILATERAL innervation
lower face - CONTRALATERAL innervation
corticobular tract CN 12
tongue - CONTRALATERAL innervation
corticobulbar tract lesion
lesion in cortex or corticobulbar tract - contralateral hemiparesis of the lower facial muscles (CN 7) and the tongue (CN 12)
Bell’s palsy - damage to CN 7, hemiparesis to both upper and lower facial muscles
upper motor neuron (UMN)
cortex, internal capsule, descending motor tracts in brainstem/spinal cord, terminal end of descending neuron before synapse with motor nucleus in the anterior horn
lower motor neuron (LMN)
anterior horn - motor nucleus
motor root
motor postion of spinal nerve root and peripheral nerve
UMN lesion
damage to motor pathway anywhere above the anterior horn cell
cortex, internal capsule, descending motor tracts in brainstem/spinal cord
pathologies = stroke SCI, tumor, MS, ALS
UMN lesion signs/symptoms
hyper reflexia
hyper tonicity
spastic weakness
small amount of muscle atrophy due to disuse
UMN lesion pathological reflexes
plantar reflex test + Babinski’s sign = extension of the great toe and fanning of other toes
Hoffman’s sign = flexion of thumb or index after flicking middle or ring finger at DIP joint
LMN lesion
damage to motor pathway to, or distal to, the anterior horn
LMN lesion signs/symptoms
hyporeflexia
hypotonicity
flaccid weakness
severe muscle atrophy
pathological reflexes NOT present
dorsal column-medial lemniscus system function
discriminating touch (well-localized touch), pressure, vibration, and proprioception (joint position sense) from the body
dorsal column-medial lemniscus system pathway
sensory information enters posterior horn and ascends in the ipsilateral posterior column up to the medulla -> crosses midline at the medulla, ascends to thalamus in medial leminiscus and projects to primary somatosensory cortex (3,1,2)
dorsal column-medial lemniscus system - lesion ABOVE medulla
CONTRALATERAL loss of proprioception, discriminating touch and vibration
dorsal column-medial lemniscus system - lesion BELOW medulla
ipsilateral loss of proprioception, discriminating touch and vibration below the level of the lesion
dorsal column-medial lemniscus system clinical exam procedures
vibration sense test
joint position sense test
discriminating touch tests
romberg’s test
spinocerebellar tracts function
transmits unconscious proprioception to cerebellum
spinocerebellar tracts pathway
proprioceptive information enters spinal cord and ascends in the ipsilateral lateral column of spinal cord -> ascend to brainstem and enter cerebellum
does NOT cross midline
spinocerebellar tracts lesion
ataxia but isolated lesion is rare
any ataxia impairment from a lateral column injury/lesion is often overshadowed by co-existing hemiparesis
lateral spinothalamic tract function
mediates discriminative aspects of pain/temp sensation from the body
detect and localize pain/temp from body
fast pain pathway
lateral spinothalamic tract pathway
nociceptive information enters spinal cord and crosses midline immediately -> ascends in the contralateral lateral column up to the thalamus and projects to primary somatosensory cortex
lateral spinothalamic tract lesion
contralateral loss of pain and temperature below the lesion
lateral spinothalamic tract clinical exam procedures
pinprick/pinwheel test - detect ability to sense sharp pain
temperature test - compare cold vs. warm object
anterior spinothalamic tract function
mediate visceral, consciousness, autonomic and emotional/behavioral reactions to pain
involved in central modulation of pain
slow pain pathways
anterior spinothalamic tract pathway
nociceptive information enters posterior horn and immediately crosses midline in spinal cord -> ascends contralaterally in anterior column and terminates in different CNS structures
reticular nuclei in brainstem
tectum-superior colliculi
pretectal (periaqueductal gray)
thalamus and project to limbic
anterior spinothalamic tract clinical exam procedures
response to painful stimuli
Glasgow Coma Scale
