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Bloc J - Neuro > Oct3 M2,3-Spinal Cord > Flashcards

Oct3 M2,3-Spinal Cord Flashcards

1
Q

spinal cord basic dev

A

-neural tube with NCC arounds closes
-NCCs form dorsal root ganglion
ventral (anterior) horn = motor cell body
-dorsal (posterior) horn = sensory cell body
-white matter tracts running on periphery. the cell bodies are outside of the spinal cord
-grey matter centrally. the cell bodies are inside the spinal cord

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2
Q

why vertebra, muscle and skin have associated levels

A

bc all derived from somites

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3
Q

where spinal nerves exit the spinal COLUMN

A
  • C1 to C7 exit above the corresponding vertebrae
  • there is no C8 vertebrae
  • C8 root exits below the C7 vertebrae
  • T1 and below exit below their correspond vertebrae
  • 8 cervical nerves (whereas 7 cervical vert), 12 thoracic nerves, 5 lumbar, 5 sacral*
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4
Q

where do spinal nerves exit the spinal cord

A

a bit above the location where they will exit the spinal column (below or above a vertebrae) c spinal cord moved up in adult and ends in L1, L2 (vert). so nerves have to travel down when leave the spinal cord in order to reach their vertebrae (where they exit)

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5
Q

cauda equina def

A

lumbar and sacral nerve roots that descend below the adult spinal cord and travel below L1,2 (vert) to leave the spinal cord at the correct foraminae

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6
Q

why do cervical and lumbar cord enlargements exist

A

because of input and output to the limbs

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7
Q

conus medullaris def

A

most inferior part of the spinal cord (sacral levels)

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8
Q

what forms a spinal nerve (one spinal nerve on each side of each level)

A

the fusion of the dorsal root and the ventral root

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9
Q

how do segmental reflexes work (like tapping the patellar tendon)

A
  • stretch the muscle (bc tap tendon)
  • special Rs in the muslce (spindle Rs) sense this
  • Rs have their nucleus in the dorsal root ganglion
  • reflex to spinal cord
  • monosynpatic reflex onto a LMN (which goes in ventral horn)
  • whole root part of PNS*
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10
Q

cause of decreased reflexes

A

lesion anywhere in the arc of the monosynpatic reflex

LMN lesion for ex

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11
Q

cause of increased reflexes

A

damage to UMNs

-they normally act as a break (inhibition) on the spinal reflex)

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12
Q

cause of increased tone (spasticity)

A

damage to UMNs

-they normally act as a break (inhibition) on the LMNs and LMNs normally produce a normal resting tone

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13
Q

where does a spinal nerve (mix of ventral and dorsal root/horn) go + clinical relevance

A

exits in the intervertebral foramen

  • vertebrae articulate with each other with facet joints
  • common problem = pinched nerve from either 1. herniating disc bulging backwards or 2. aging and arthritis (caused by adaptive hypertrophy of the weight-bearing facet joints) or 3. calcification of ligaments around these bones
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14
Q

shape of the grey matter in the spinal cord

A

X shaped, butterfly shaped (being the ventral and dorsal horn on each side)

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15
Q

(imp) lateral corticospinal tract contains what

A

axons of the UMNs (have their cell bodies in the contralateral motor cortex (crossed in lower medulla). they synapse on LMNs in anterior horns)

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16
Q

(imp) lateral corticospinal tract location

A
  • is white matter
  • circle between two wings of butterfly shape, laterally
  • is bilateral
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17
Q

(imp) dorsal column is what

A

-tract responsible for touch, joint position (proprioception) and vibration in arms and legs

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18
Q

(imp) dorsal column location

A
  • is white matter
  • posteriorly and medially (the two dorsal columns are in the region between the dorsal horns (grey matter of the butterfly) on each side)
  • bilateral
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19
Q

divisions of the dorsal column

A
  • fasciculus grascilis (medial half, half of each of the two dorsal columns that touches the midline). carries info from legs
  • fasciculus cuneatus (lateral half.) carries info from the arms
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20
Q

(imp) where tracts of the dorsal column travel

A
  • cell body was in dorsal root ganglion
  • travel up spinal cord ipsilaterally
  • cross in lower medulla
  • go synapse in thalamus
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21
Q

(imp) anterior spinothalamic tract function

A

carries touch, pain and temperature information

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22
Q

(imp) anterior spinothalamic tract location

A
  • is white matter
  • band covering the wider anterior part of the ventral horn on each side
  • bilateral
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23
Q

(imp) where tracts of the anterior spinothalamic tract travel

A
  • cell body in the dorsal root ganglion
  • synapse immediately in the dorsal horn so that the second neuron crosses contralaterally immediately
  • ascend up the spinal cord contralaterally
  • go to thalamus
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24
Q

Wallerian degeneration def

A

if have a neuron with a cell body and an axon and you cut part of that axon, the part of the axon distal to the cut degenerates and the part linked to cell body survives
the function of the neuron is lost whatsoever

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25
Q

Wallerian degeneration application in the spinal cord

A
  • if cut spinal cord at a certain level and look at axons of the 3 main tracts above the cut, the axons of lateral corticospinal tract survived and the axons of dorsal column and anterior spinothalamic tract died
  • ALL THREE TRACTS LOST THEIR FUNCTION
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26
Q

blood supply to the spinal column and cord

A
  • single anterior spinal artery running along the length of the anterior spinal cord medially (comes from aorta). divides in branches called anterior radicular aa
  • multiple posterior spinal arteries running along the length of the posterior spinal cord. (come from aorta) divide in branches called posterior radicular aa
27
Q

importance of the spinal arteries

A
  • anterior spinal a = blood supply to anterior two thirds

- posterior spinal aa = to posterior third of spinal cord

28
Q

radicular aa imp thing to note anatomically

A
  • note like usual artery, capillary bed, vein sequence

- in radicual aa blood can go in both directions

29
Q

radicular aa imp thing clinically

A
  • areas where the number and size of radicular aa is decreased from rostral to caudal
  • these areas are more at risk for vascular problem (ischemia)
30
Q

example of an area where radicular a nbr and size is low (susceptible to ischemia)

A
  • lower thoracic cord
  • one dominant ANTERIOR radicular artery there called artery of Adamkiewicz
  • ischemia during aorta surgery (vascular surgeon) = region it supplies is affected
31
Q

tracts supplied by the anterior spinal artery

A
  • anterior spinothalamic tracts

- lateral corticospinal tracts

32
Q

tracts supplied by the posterior spinal arteries

A

dorsal columns

33
Q

why is the anterior spinal a and its region more susceptible to ischemia

A

bc it exists as a single dominant artery (whereas posterior spinal aa form an anastomotic network)

34
Q

anterior spinal a infarction clinically

A
  • bilateral leg weakness and loss of pain and temperature in the legs
  • no loss of touch, joint position and proprioception
35
Q

why do clinicians not like to test touch on a neuro exam

A

doesn’t help much for localization because touch will always be normal except when BOTH dorsal column and anterior spinothalamic tract are affected (bc both carry touch) so you can’t discriminate the two

36
Q

what patients with spinal cord lesions complain of

A
  • weakness in the limbs
  • sensory loss
  • pain and paraesthesias = tingling, burning, etc.(the spinal cord itself is not pain sensitive but if have pathology inside it damaging the tracts, you get these symptoms)
  • bowel and bladder dysfunction
37
Q

what is the Llerhmitte sign

A

unique symptom where patients complain that flexion of their neck results in electric current-like sensation running down their spine. this is caused by demyelination of axons in the DORSAL COLUMN (tract for touch, position, vibration). the exposed axons are stretched and irritated by the neck flexion (makes sense bc dorsal column is posterior)

38
Q

cause of the Llerhmitte sign

A

any pathology in spine causing demyelination

39
Q

neuro exam features that indicate towards a spinal cord lesion

A
  • UMN findings (normal bulk, increased tone and reflexes, weakness below lesion level)
  • BILATERAL signs (bc of small size of spinal cord).
  • crossed sensory findings, meaning that if unilateral, will get ipsilateral UMN findings + vibration and joint position loss + contralateral pain and temp loss
  • sensory levels (= patient feels nothing at or below a specific level on their body. tested with pin-prick (pain) sensation)
  • coordination seems normal (is abnormal bc cerebellum to spinal cord tracts are damaged but this is overshadowed by UMN problems (spasticity, etc.)
  • gait: weakness, spasticity and sensory loss
  • bowel and bladder dysfunction
40
Q

weakness in LMN vs UMN lesion

A

greater weakness in a LMN lesion bc you deprive the muscle form its LMN which is important for the muscle

41
Q

why no LMN symptoms also in a spinal lesion (bc there is LMNs at each level)

A
  • there are LMN signs but ONLY AT THAT LEVEL (only LMNs AT THAT LEVEL are damaged)
  • more importantly, damages all the UMN axons going below that level so UMN findings are greater
42
Q

normal tone in baby

A
  • when lie baby on their back, have normal resting tone
  • legs are not lying flat on bed and touching it, legs are flexed above the bed
  • arms also flexed
  • abnormal tone = baby completely flat against bed like frog’s legs
  • abnormal = if pick up baby by their abdomen, their back facing up = completely flaccid (normal = head, arms, legs up a little bit)
  • normal = pull baby up by their arms in a lying position, the head is up and not dropping to the back
  • all bc of normal resting tone in muscles*
43
Q

why is there a normal resting tone

A

LMN to a muscle constantly receiving info on how much muscle is stretched (contracted) and LMN gives back a normal level of contraction.
+ UMNs act as a brake on that to make sure not too much tone (just like the reflex arc)

44
Q

can’t move legs after surgery on aorta: other expected findings

A
  • this surgery preferentially damages anterior spinal a
  • would first test for pain and temp. joint position and vibration are spared most often
  • STILL, vibration and joint position (dorsal column) could still be affected
  • touch most often normal except if both dorsal column + anterior spinothalamic tract affected
45
Q

can you get spinal cord compression in a patient with a metastasis to the L3 vertebral body

A

no because the adult spinal cord ends at L1, L2 vertebral levels

  • L3 metastasis = compression damaging cauda equina
  • L1 metastasis = compression damaging conus medullaris
  • metastasis above L1 = compressing spinal cord
46
Q

(imp) 3 syndromes of spine compression

A
  • spinal cord compression
  • conus medullaris syndrome
  • cauda equina syndrome
47
Q

(imp) characteristic findings of spinal cord compression (lesion)

A
  • motor weakness
  • sensory level (all lost below a level)
  • bladder dysfunction
  • no pain (but possible if metastasis to vertebral body bc vert body + meninges feel pain)
48
Q

(imp) charact findings of conus medullaris syndrome

A

the conus medullaris carries sacral and coccygeal nerves:

  • sacral perianal sensory loss
  • ALWAYS bladder dysfunction
  • no pain
  • no motor findings (no weakness, etc.)
49
Q

(imp) charact findings of cauda equina syndrome

A
  • patchy LMN findings (bc some ‘‘cords’’ affected)
  • patchy sensory loss
  • PAIN
  • sometimes bladder dysfunction
50
Q

example of central cord syndrome

A

syringomyelia (syrinx)

  • there is a central canal (fluid filled opening) in the middle of the spinal cord INVOLVING ONLY A FEW LEVELS
  • can expand and develop abnormalities
51
Q

neuro exam findings in a central cord syndrome

A

suspended sensory loss

  • lesion in centre affects only pain and temp fibers crossing at the level of the lesion and not fibers that already crossed
  • suspended sensory loss in the sense that pain and temp are loss only for a few dermatomes (for where the central cord is affected)
52
Q

some extrinsic (compression, extramedullary) things affecting the cord

A
  • mechanical
  • malignancy
  • blood (aco causing hematoma)
  • infection (abscess, TB)
53
Q

some intrisinc (intramedullary) things affecting the cord

A
  • nutritional (vit B12 deficiency)
  • MS
  • infection (myelitis)
  • vascular (ischemic)
  • tumor (rare)
54
Q

myelitis vs myelopathy

A
  • myelopathy = general term, anything intrisic or extrinsic affecting the cord
  • myelitis = specific. intramedullary. usually inflammatory
55
Q

mechanical compression pathologies in younger patients

A

disc herniation

  • central = affects cord, conus, cauda
  • lateral = compresses nerve root exiting at that level
  • majority of disc herniations resolve on their own (pop back in)
56
Q

mechanical compression pathologies in older patients

A

degenerative and multifactorial

  • wear and tear on facet joints (from weight-bearing) leads to dev of osteophytes
  • calcification and hypertrophy of supportive ligaments with age
  • disc bulging
  • all these affect central canal or neural foramen = intervertebral foramen)
  • new bone growth + thick and calcified ligaments don’t resolve on their own*
57
Q

consequence of vitB12 deficiency on spinal cord

A
  • abnormal findings corresponding to lesions to lat corticospinal tract + dorsal column only
  • is called sub-acute combined degeneration of the dorsal column and the the corticospinal tract (bc these two regions are sensitive to low B12)
  • easily tx with B12
58
Q

anatomy of the meninges in the spinal cord

A
  • pia mater very tough and tightly stuck to the spinal cord white matter
  • subarachnoid space (CSF filled space between pia mater and arachnoid)
  • arachnoid (circle shaped, around spinal cord)
  • dura mater (right outside arachnoid, stuck to it)
  • epidural space filled with fat
  • vertebral body anteriorly or spinous process and other bone posteriorly
59
Q

lumbar puncture def

A
  • done in subarachnoid space
  • is a diagnostic test
  • done below L2 vertebra to not damage the spinal cord, needle will simply brush away the cauda equina and rarely damages it*
60
Q

spinal anaesthesia is done where

A

subarachnoid space
done below L2 vertebra to not damage the spinal cord, needle will simply brush away the cauda equina and rarely damages it

61
Q

epidural anaesthesia is done where

A

epidural space

62
Q

diff layers to get through in a LP

A
  • skin
  • fat
  • interspinous ligaments between spinous processes (there is no bone between spinous processes, there’s these ligaments)
  • longitudinal ligament (ligament flavum)
  • dura mater and arachnoid
  • spinal column where cauda equina is.
  • remove CSF
63
Q

spinal anaesthetic done when

A
  • for surgery in leg or pelvis

- is done below the level of the spinal cord

64
Q

how do they control the spread of spinal anaesthesia (how does it not spread in all the CSF and subarachnoid space of all the spine)

A

use diff baricity (density) for the anaesthesia

Bloc J - Neuro (60 decks)

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