Motor Control and the Corticobulbar Tract

Question 1

what is the pathway of the upper motor neurons in the corticobulbar tract

Answer 1

primary motor cortex - corona radiata - genu of internal capsule - midbrain cranial nerve nuclei

Question 2

which is the only cranial nerve to supply the contralateral side of the face

Answer 2

trochlear

Question 3

how is a pseudobulbar palsy caused

Answer 3

damage to contralateral innervation (ipsilateral can still innervate but is not as strong so partial paralysis)

Question 4

which nuclei of cranial nerves are in the midbrain

Answer 4

oculomotor, trochlear

Question 5

which nuclei of cranial nerves are in the pons

Answer 5

trigeminal, abducens, facial nerve

Question 6

which nuclei of cranial nerves are in the medulla

Answer 6

nucleus ambiguus, hypoglossal nucleus, spinal accessory

Question 7

which nuclei has an upper and lower nucleus

Answer 7

facial nerve nuclei

Question 8

what nerves share the nucleus ambiguus

Answer 8

glossopharyngeal and vagus

Question 9

what nerves make the pharyngeal plexus

Answer 9

glossopharyngeal and vagus

Question 10

what are the 4 rules of the corticobulbar tract

Answer 10

1. UMN is called supranuclear fibre
2. corticobulbar travels with corticospinal (commonly injured together)
3. UMN connects bilaterally to cranial nuclei (not hypoglossal/lower facial nuclei)
4. LMN are also cranial nerves
5. cranial nerve cell bodies innervated by UMN’s must have a motor neuron

Question 11

what nuclei do not have bilaterally synapsing UMN

Answer 11

facial nerve lower nuclei and hypoglossal

Question 12

what are the 3 exceptions to the corticobulbar rules

Answer 12

1. common bilateral innervation using oculomotor nerve
2. facial nerve upper and lower nuclei
3. contralateral innervation of hypoglossal nerve to tongue

Question 13

what does a lesion at upper motor neuron level (on lower nucleus) mean for the facial innervation

Answer 13

upper face will be face and only one side of the lower face will be paralysed

Question 14

what does a lesion at lower motor neuron level at the facial nuclei mean for facial innervation

Answer 14

the whole side of the face will be paralysed as neurons from both upper and lower nuclei leave together

Question 15

what does UMN lesions mean for hypoglossal innervation of the tongue

Answer 15

deviates tongue to protrude to opposite side

Question 16

what does LMN lesions mean for hypoglossal innervation of the tongue

Answer 16

deviates tongue to protrude at the same side