Pyramidal Tract

Question 1

What layers of the cortex contain the pyramidal neurons (and the gigantic pyramidal neurons of Betz)

Answer 1

External pyramidal (layer3)
Internal pyramidal (layer 5) - gigantic pyrimidal neurons of betz

Question 2

What is the origin of the pyramidal tract and the 3 areas of it

Answer 2

Precentral gyrus- lat 1/3= upper limb, sup 1/3= mm of trunk

Paracentral gyrus- med 1/3 mm of lower limb

Question 3

What supplies the precentral gyrus and paracentral gyrus

Answer 3

Pre- middle cortical branches of middle cerebral aa

Para- colossal marginal artery (br of ant cerebral aa)

Question 4

What part of the internal capsul does the corticospinal tract occupy and what is it supplied by

Answer 4

Post limb

Supplied by deep branches of middle cerebral aa (lenticulostriate aa)

Question 5

Path of the corticospinal tract thru the brainstem and blood supply at each lvl

Answer 5

1. enters peduncle where it occupies mid 1/3 (supplied by post cerebral aa)
2. Descend thru pons (upper limb more medial) (supplied by pontine aa of basilar)
3. Thru medulla( upper limb more medial) (supplied by medullary branches of vert/ant spinal)

Question 6

what is the path of neurons as it exits the medulla

Answer 6

85% of corticospinal tract will cross midline at decussion of pyramids (lat corticospinal tract)
15% stay ispilaterally w origin (will cross over at specific level thru ant white comissure)

Question 7

Somatopy of lat and ant corticospinal tract

Answer 7

Lat- upper limb will be more medial

ant- upper limb will be more post

Question 8

What supplys the corticospinal tract in spinal cord

Answer 8

Medullary branches of ant spinal aa

• Most post part of lat tract get supply from medullary branches of vasocorona

Question 9

What is the target of innervation of corticospinal tract

Answer 9

lamina 9 +7 contrallaterally

Question 10

What will a lesion in the precentral or paracentral gyrus cause

Answer 10

Precentral- contralateral upper limb

Paracentral- contralateral lower limb

Question 11

What will a lesion in the post limb of int capsul cause

Answer 11

loss of motor control of CL upper and lower l

Question 12

What will a lesion in the cerebral puduncles, pons or medulla cause

Answer 12

CL upper limb, lower limb and trunk

Question 13

What will a lesion at the motor decussion cause

Answer 13

Will cause bilateral paralysis of upper and lower limb

Question 14

What will a lesion at the spinal cord cause

Answer 14

Will cause functional deficit at the level of the lesion ipilaterally (LMN type lesion)