Spinal Cord MAIN BIG STUFF Flashcards
Ascending spinal cord paths are 3 neuron pathways.
What is the location of the 3 neurons?
1st neuron: dorsal root ganglion (receptor to brainstem/spinal cord)
2nd neuron: brain stem or spinal cord (crosses to other side of NS) (to thalamus)
3rd neuron: thalamus (to cerebral cortex)
Everything stops at the _____ before reaching the cortex.
Everything stops at THALAMUS before reaching the cortex.
Posterior Column (Dorsal Column) Pathway
Modalities? Components?
- position sense
- vibration sense
- 2 point discrimination
Fasciculus gracilis (lower body). Fasciculus cuneatus (upper body).
Fasiculus Gracilis
Info from T6 and BELOW enters the spinal cord here and travels medially.
Fasciculus Cuneatus
Info from T5 and ABOVE enters spinal cord here and travels laterally.
Spinothalamic Pathway
Modalities?
Mechanism?
localization of pain and temperature
dorsal root ganglion central processes synapse ON sensory neurons (2nd order neurons) in dorsal horn of the cord
then those neurons cross to other side (through ventral white commissure) and head up to thalamus/cortex CONTRALATERALLY.
Posterior Column (Dorsal Column) Pathway
General mechanism?
dorsal root ganglion sensory neurons transmit signal through central processes up the column IPSILATERALLY.
@ brainstem, meet nuclei of same name (2nd order neurons) and THEN cross over to other side of NS and head to cortex.
describe neurons/axons of posterior column (dorsal column) Pathway
large neurons, heavily myelinated axons
describe neurons/axons of spinothalamic pathway
small, poorly myelinated or non-myelinated axons
corticospinal pathway (modalities)
voluntary fine movement of distal extremities
corticospinal pathway (path of neurons)
Upper motor neuron (UMN) cell body in cerebral cortex (precentral gyrus).
Decussation in caudal medulla (85%) [other 15% decussate in anterior corticospinal pathway]
Lower motor neuron (LMN) cell body in ventral horn of spinal cord.
LMN axon heads to skeletal muscle.
where do corticospinal tract fibers cross?
85% - caudal medulla - form lateral corticospinal pathway
15% - travel in anterior corticospinal pathway - cross at level of the LMN they will contact
upper motor neuron lesion of corticospinal tract
1) hyperreflexia
2) spastic paralysis
3) increased muscle tone
4) clasp knife reflex
5) clonus
6) babinski sign present
7) large area of the body is affected (from level of lesion and below)
lower motor neuron lesion of corticospinal tract
1) flaccid paralysis
2) loss of deep tendon reflexes
3) decreased muscle tone
4) atrophy
5) fasciculations
6) segmental distribution of deficit
Brown-Sequard Syndrome
Hemisection of spinal cord.
Deficits in dorsal column, spinothalamic, and corticospinal tracts.
Ipsilateral loss of position and vibration sense.
Contralateral loss of pain and temperature sense (slightly below level of lesion due to movement of spinothalamic fivers up thru lissauer’s tract before decussation).
Ipsilateral paralysis.
syringomyelia
- affects ventral white commisure
- suspended sensory loss for pain and temperature
- starts small, gets bigger: can expand to VH –> LMN lesion –> next affected is burning fingers w/o realizing, LMN weakness
ALS
Amyotrophic Lateral Sclerosis
- motor disease only
- combined UMN and LMN disease [LMN signs predominate, fasciculations]
- affects corticospinal tract, LMNs
- does NOT affect sensory
- rare
- elderly
- progressive
- 2-3 yr survival
- death from infection
ALS - LMN lesions vs UMN lesions
LMN lesions: fasciculations
UMN lesions: clonus, babinski sign
tabes dorsalis
Predominant DORSAL COLUMN deficits
- loss of position/vibration sense
- difficulty maintaining erect posture
- Romberg sign
- patchy loss of pain/temp
- affects dorsal roots/ganglia
-form of tertiary neurosyphilis
poliomyelitis
Anterior (ventral) horn cells affected.
LMN syndrome.
-viral infection with predilection for anterior horn cells
-acute febrile illness
post-polio syndrome
- new weakness years after acute polio (stress to system)
- often in same distribution as original weakness
anterior spinal syndrome
Spinothalamic and Corticospinal affected.
Dorsal column preserved.
(due to loss of anterior spinal artery, providing blood to anterior 2/3 of spinal cord)
Loss of pain/temperature, motor function
extrinsic cord compression
osteophytes, herniations, tumors, abcesses
- commonly presents with pain (from root compression)
- early involvement of sacral segments (from compression of lateral aspects of spinothalamic tracts and lateral corticospinal tracts)
- localized LMN lesion from compression of ventral root
cervical enlargement
C5-T1
lumbar enlargement
L3-S2
