ENT - vertigo?

[Mirror Form]

Hey,
Any of you ENT buffs out there know why scratching your ear canal w/ your finger (b/c it's itchy) can induce vertigo? I have a oral test on that coming up and I can't find it in any books or anywhere else on the internet!
-Sledge

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[mpp]

An oral test on scratching your ear...what will they think of next?

 

[DODODO]

maybe it has something to do with the fact that the vestibulocochlear nerve runs behind the tympanic membrane, and irritating the membrane/nerve leads to vertigo. Same reason why if you stick a cutip in your ear too far and it hits the membrane you get a gag reflex. B/c the cranial nerve for the back of the throat which controls the "gag reflex" also runs along with the vestibulocochlear nerve. Not positive though.

 

[citygirl]

DODODO, that sounds reasonable. I know when they do an ENG test for Meniere's disease they shoot water on the TM to induce vertigo and then measure the eye movements (N of ENG = nystagmus). At least, that is how they used to do it.

 

[Mirror Form]

hey,
that logic sounds pretty good to me.
Thanks!

 

[mpp]

The old COWS menomonic...Cold Opposite/Warm Same

 

[durphy]

the chorda tympani runs behind the TM - it's a branch of the facial nerve and has nothing to do with vertigo. The facial nerve controls the stapedius muscle and buffers the ear from harsh noises via the stapedius muscle. Chorda tympani innervates salivary glands and isn't associated with vertigo. Vertigo is related to the inner ear specifically and the endolymph which is in the inner ear. When you pour cold water into a conscious (or unconscious) person's ear, you change the density of the the endolymph and induce nystagmus and vertigo. CN 8 is the nerve involved with the inner ear - hearing and vertigo.

I've never heard of the scratching phenomenon, but I imagine it's a pressure phenomenon also involving the endolymph.

 

[mpp]

Actually, the chorda tympani carries taste from the anterior 2/3 of the tongue...

 

[DODODO]

vestibulocochlear nerve = CN 8

 

[durphy]

oops, you're right. i forgot. internship is making me dumber day by day....

 

[durphy]

you know, i just looked it up - it does both: taste and salivary glands (submandibular and sublingual. so, i'm only half as dumb now...

 

[Mirror Form]

Hey, my oral exam went alright, but not on this question. Apparently, MPP was pretty much right, the CN 8 doesn't run anywhere near the external ear canal or the TM, and it's the thermal effect of water transmitted to the inner ear that caues nystagmus. The scratching the external ear canal causing vertigo is some guy's sign (his name starts w/ an H) and it indicates a cholesteatoma!

 

[DODODO]

sorry that we couldn't be of any help. Man, I feel pretty lousy that it was partly my fault that you got it wrong. What was this test for anyways.

 

[Mirror Form]

The test was no big deal, it counts for only like 3% of my final grade in surgery. So that one question wasn't all that significant, especially since I probably wouldn't have got it right anyway!

 

[neutropeniaboy]

The bottom line about vertigo patients is that working them up truly sucks, because the majority of them don't have clear cut answers like schwannomas, fistulas, Menieres, or whatever's on your hotlist.

 

[ent_doc]

Originally posted by Sledge2005
Hey, my oral exam went alright, but not on this question. Apparently, MPP was pretty much right, the CN 8 doesn't run anywhere near the external ear canal or the TM, and it's the thermal effect of water transmitted to the inner ear that caues nystagmus. The scratching the external ear canal causing vertigo is some guy's sign (his name starts w/ an H) and it indicates a cholesteatoma!

Hitselberger's sign is anesthesia of the posterior canal wall and usually indicates acoustic neuroma (compression of 7th nerve contribution to EAC sensation). Haven't seen one yet.

As to the vertigo, it could indicate Lateral semicircular canal fistula (with cholesteatoma). You can do calorics with air, so in theory just scratching could cause vertigo.