Spinal Cord MAIN BIG STUFF

Question 1

Ascending spinal cord paths are 3 neuron pathways.

What is the location of the 3 neurons?

Answer 1

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)

Question 2

Everything stops at the _____ before reaching the cortex.

Answer 2

Everything stops at THALAMUS before reaching the cortex.

Question 3

Posterior Column (Dorsal Column) Pathway

Modalities? Components?

Answer 3

• position sense
• vibration sense
• 2 point discrimination

Fasciculus gracilis (lower body).
Fasciculus cuneatus (upper body).

Question 4

Fasiculus Gracilis

Answer 4

Info from T6 and BELOW enters the spinal cord here and travels medially.

Question 5

Fasciculus Cuneatus

Answer 5

Info from T5 and ABOVE enters spinal cord here and travels laterally.

Question 6

Spinothalamic Pathway

Modalities?
Mechanism?

Answer 6

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.

Question 7

Posterior Column (Dorsal Column) Pathway

General mechanism?

Answer 7

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.

Question 8

describe neurons/axons of posterior column (dorsal column) Pathway

Answer 8

large neurons, heavily myelinated axons

Question 9

describe neurons/axons of spinothalamic pathway

Answer 9

small, poorly myelinated or non-myelinated axons

Question 10

corticospinal pathway (modalities)

Answer 10

voluntary fine movement of distal extremities

Question 11

corticospinal pathway (path of neurons)

Answer 11

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.

Question 12

where do corticospinal tract fibers cross?

Answer 12

85% - caudal medulla - form lateral corticospinal pathway

15% - travel in anterior corticospinal pathway - cross at level of the LMN they will contact

Question 13

upper motor neuron lesion of corticospinal tract

Answer 13

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)

Question 14

lower motor neuron lesion of corticospinal tract

Answer 14

1) flaccid paralysis
2) loss of deep tendon reflexes
3) decreased muscle tone
4) atrophy
5) fasciculations
6) segmental distribution of deficit

Question 15

Brown-Sequard Syndrome

Answer 15

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.

Question 16

syringomyelia

Answer 16

• 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

Question 17

ALS

Answer 17

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

Question 18

ALS - LMN lesions vs UMN lesions

Answer 18

LMN lesions: fasciculations

UMN lesions: clonus, babinski sign

Question 19

tabes dorsalis

Answer 19

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

Question 20

poliomyelitis

Answer 20

Anterior (ventral) horn cells affected.
LMN syndrome.
-viral infection with predilection for anterior horn cells
-acute febrile illness

Question 21

post-polio syndrome

Answer 21

• new weakness years after acute polio (stress to system)

- often in same distribution as original weakness

Question 22

anterior spinal syndrome

Answer 22

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

Question 23

extrinsic cord compression

Answer 23

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

Question 24

cervical enlargement

Answer 24

C5-T1

Question 25

lumbar enlargement

Answer 25

L3-S2