Pyramidal tracts??

[Profsnail]

Hi, I've a few questions actually:

1. Why are corticobulbar tracts pyramidal even though they do not pass through the pyramids like corticospinal tracts do?
2. I know corticobulbar tracts innervated CN3, 4, 5, 6, 7, 9, 10, 11, 12 directly or indirectly, but what happens to CN8?

Thank you!

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[RenegadeSynapse]

1) It's an artifact of the nomenclature. Pyramidal tracts are better thought of as primary motor fibers; in the pyramids, that mostly means corticospinal fibers. Corticobulbar motor fibers are primary motor fibers to the motor cranial nerves. Extrapyramidal means...well, not pyramidal, which technically refers to a whole lot more than basal ganglia, but most of the time the term is used it refers to basal ganglia referable pathology (e.g. extrapyramidal side effects of anti-dopaminergic agents).

2) Corticobulbar, by definition, are going to be motor (hence, going from the cortex to the bulb, corticobulbar). CN 8 is the vestibulocochlear nerve, so it's a sensory nerve that carries auditory and vestibular information from the inner ear into the brainstem.

 

[deathmerchant]

Hi, I've a few questions actually:

1. Why are corticobulbar tracts pyramidal even though they do not pass through the pyramids like corticospinal tracts do?
2. I know corticobulbar tracts innervated CN3, 4, 5, 6, 7, 9, 10, 11, 12 directly or indirectly, but what happens to CN8?

Thank you!

1. You are right. But like mentioned above, technically Corticobulbar fibers shouldn't be called pyramidal (it should be just corticospinal), but practically thats probably the most helpful for understanding their role and anatomy in the brain. Many experts will agree with you on the pedantics.

2. Yes Corticobulbar tract is just the 'descending motor' component for cranial nuclei.