Testing taste in different cases

[Function]

Hello everyone

 

Soon I'll be taking exam on the CNS. In preparation for this exam, there are multiple example questions, which were frequently asked on previous editions of the exams. They are reconstructed by fellow students of older years, who already took the exam.

 

One of these questions is:

 

Testing the gustatory sense is useful in patients presenting with:

• Dysarthria
• Diplopia
• Loss of hearing
• Hemifacial paralysis

I think 3 of these answers could be correct:

• Dysarthria because speaking involves several cranial nerves, of which Nn. VII, IX, X and XII. Of these, VII, IX and X are important for gustatory sense (VII anterior 2/3 tongue; IX posterior 1/3 tongue; X uvula), so in this case I think testing the gustatory sense might help the physician distinguish the affected nerve.
• Hearing loss because the intermediofacial nerve runs through the petrous part of the temporal bone, along with the eighth cranial nerve, the vestibulocochlear nerve. I think any space taking mass (tumor, e.g. vestibular schwannoma) might compress both nerves, inducing hearing loss, loss of taste and also hemifacial paralysis (of type Bell's palsy)
• Hemifacial paralysis; facial muscles innervated by N. VII; I think that it is indeed useful to test the taste in patients presenting with full hemifacial paralysis, both upper and lower facial muscles (in order to determine at what level the lesion might have occured: before or after the splitting of the chorda tympani?); yet not so useful in patients presenting with paralysis of only lower facial paralysis, for this would already imply a higher order lesion than a peripheral N. VII Bell's palsy.

 

It may be that the question was reconstructed with errors.

However, should someone be able to give me an unambiguously answer, thank you very much.

 

F

[Xalatan]

You are on the right track. Taste is vii ix and x so as long as you mention the muscles supplied by these cn related to articulation you should be fine - buccinator, stylopharyngeus, palatopharyngeus, pharyngeal constrictors, intrinsic laryngeal muscles etc.

 

Not sure about diplopia - iii iv vi don't seem related to taste, unless there is some more generalised brain stem lesion (but patient would probably be decerebrate and comatose), or maybe disease like ms or tuberous sclerosis.

 

Loss of hearing you will probably mention the internal acoustic meatus and facial canal shared by vii and viii. Lesions obstructing the path of chorda tympani will affect taste to anterior 2/3. Like acoustic neuroma you mentioned.

 

Hemifacial pearlysis is ipsilaterial vii so this directly related to taste sensation by vii.