Caloric Test; Vestibulo-Ocular Reflex!

[Dr.NickRiviera]

A 29-year old man has a 1-week history of feeling dizzy. Warm water instilled into the left ear while the patient is supine elicits nystagmus with a quick phase to the left; warm water instilled into the right ear elicits no eye movements. Which of the following is the most likely site of a lesion?

A. Left frontal eye fields
B. Right frontal eye fields
C. Left pontine gaze center
D. Right pontine gaze center
E. Left vestibular apparatus
F. Right vestibular apparatus.

[mbbs2010]

remember the mnemonic (see here http://www.usmle-forums.com/usmle-st...tion-viii.html)

CO WS

cold-- opposite.... ie with cold water the nystagmus (fast component) shud be towards opposite ear

warm-- same... ie with warm water the nystagmus (fast component) shud be towards same ear

answer is RIGHT VESTIBULAR apparatus

[Casandra]

Originally Posted by Dr.NickRiviera

A 29-year old man has a 1-week history of feeling dizzy. Warm water instilled into the left ear while the patient is supine elicits nystagmus with a quick phase to the left; warm water instilled into the right ear elicits no eye movements. Which of the following is the most likely site of a lesion?

A. Left frontal eye fields
B. Right frontal eye fields
C. Left pontine gaze center
D. Right pontine gaze center
E. Left vestibular apparatus
F. Right vestibular apparatus.

I always mess up vest-oc reflex and voluntary conjugate gaze qs...

I agree and I think F. Right vestibular apparatus is the answer.

@Dr.NickRiviera - what's the correct answer?

[Renaissance]

If the test was abnormal what does that mean?

[Casandra]

Originally Posted by Renaissance

If the test was abnormal what does that mean?

hmm... I don't think I understand your question...?
The test is abnormal here...

[Renaissance]

abnormal hah?
I guess i really don't understand this concept then haha

[Casandra]

Originally Posted by Renaissance

abnormal hah?
I guess i really don't understand this concept then haha

this concept is abnormal!!! I spent the last half an hour (I feel really stupid ) figuring it out.

Mnemonic (COWS) they give both in KLN and FA is good, meaning:

In normal individuals:

If you irrigate ear with Cold water, nystagmus (fast phase) should be in the Opposite direction (contralateral to the irrigated ear). (CO)

If you irrigate ear with ear with Warm water, nystagmus (fast phase) should be in the Same direction (ipsilateral to irrigated ear). (WS)

So: absence of the reactive eye movement indicates vestibular weakness/lesion (either semicircular canals or VIII nerve) in the irrigated side.

In cerebral lesion the fast phase of nystagmus will be absent (while slow phase remains) so cold water irrigation will cause deviation of the eyes towards irrigated ear.

[Renaissance]

Originally Posted by Casandra

this concept is abnormal!!! I spent the last half an hour (I feel really stupid ) figuring it out.

Mnemonic (COWS) they give both in KLN and FA is good, meaning:

In normal individuals:

If you irrigate ear with Cold water, nystagmus (fast phase) should be in the Opposite direction (contralateral to the irrigated ear). (CO)

If you irrigate ear with ear with Warm water, nystagmus (fast phase) should be in the Same direction (ipsilateral to irrigated ear). (WS)

So: absence of the reactive eye movement indicates vestibular weakness/lesion (either semicircular canals or VIII nerve) in the irrigated side.

In cerebral lesion the fast phase of nystagmus will be absent (while slow phase remains) so cold water irrigation will cause deviation of the eyes towards irrigated ear.

Thank you so much!
I got it completely, your explanation was awesome.

[Casandra]

Originally Posted by Renaissance

Thank you so much!
I got it completely, your explanation was awesome.

Glad I could help I feel so stupid though - 30 precious minutes on 1 concept!!!! Aaaaa!

[kdm0101]

thank you so much. i always thought COWS was about abnormal

Originally Posted by Casandra

this concept is abnormal!!! I spent the last half an hour (I feel really stupid ) figuring it out.

Mnemonic (COWS) they give both in KLN and FA is good, meaning:

In normal individuals:

If you irrigate ear with Cold water, nystagmus (fast phase) should be in the Opposite direction (contralateral to the irrigated ear). (CO)

If you irrigate ear with ear with Warm water, nystagmus (fast phase) should be in the Same direction (ipsilateral to irrigated ear). (WS)

So: absence of the reactive eye movement indicates vestibular weakness/lesion (either semicircular canals or VIII nerve) in the irrigated side.

In cerebral lesion the fast phase of nystagmus will be absent (while slow phase remains) so cold water irrigation will cause deviation of the eyes towards irrigated ear.

[eizou]

Originally Posted by Casandra

this concept is abnormal!!! I spent the last half an hour (I feel really stupid ) figuring it out.

Mnemonic (COWS) they give both in KLN and FA is good, meaning:

In normal individuals:

If you irrigate ear with Cold water, nystagmus (fast phase) should be in the Opposite direction (contralateral to the irrigated ear). (CO)

If you irrigate ear with ear with Warm water, nystagmus (fast phase) should be in the Same direction (ipsilateral to irrigated ear). (WS)

So: absence of the reactive eye movement indicates vestibular weakness/lesion (either semicircular canals or VIII nerve) in the irrigated side.

In cerebral lesion the fast phase of nystagmus will be absent (while slow phase remains) so cold water irrigation will cause deviation of the eyes towards irrigated ear.

I understood every part of what you wrote except "In cerebral lesion the fast phase of nystagmus will be absent (while slow phase remains)". Can you please further explain. Nystagmus is driving me crazy!

[DrNewB]

Horizontal Jerk Nystagmus = Eye repeated move slowly towards one side and then quickly back.

Slight horizontal Nystagmus can be seen normally, when attempted extreame lateral gaze. Marked degree is abnormal.

Vertal Nystagmus always abnormal = Disorder in brain stem function.

Pendular Nystagmus = Equal speed in both direction. Seen in congenital or after prolonged blindness.

A little story to remember cold caloric test,

Brain stem is very dumb and slow and Cerebral cortex is very fast and smart.

One day a man was driving a car when someone sitting to his right squirted some cold water in his right ear. The dumb brainstem sluggishly moved its eyes to the right (slow component). But the smart cortex quickly jerked the eye back towards the road (fast component)


Moral of the story: In normal waking state, Cold component towards the side of stimulus, followed by fast component (cortex and brainstem doing their job well.)

In lethargic, the cortex is slow so fast component less pronounced

In Obtundation, Cortex affected. No fast component, just the deviation (Slow component).

In Coma, Even the brain stem is affected. So no movement at all. (That's how you know if the person actually is in Coma or is faking it)

Concept and story from Clinical Neuroanatomy Made Ridiculously Simple

[eizou]

Originally Posted by DrNewB

Horizontal Jerk Nystagmus = Eye repeated move slowly towards one side and then quickly back.

Slight horizontal Nystagmus can be seen normally, when attempted extreame lateral gaze. Marked degree is abnormal.

Vertal Nystagmus always abnormal = Disorder in brain stem function.

Pendular Nystagmus = Equal speed in both direction. Seen in congenital or after prolonged blindness.

A little story to remember cold caloric test,

Brain stem is very dumb and slow and Cerebral cortex is very fast and smart.

One day a man was driving a car when someone sitting to his right squirted some cold water in his right ear. The dumb brainstem sluggishly moved its eyes to the right (slow component). But the smart cortex quickly jerked the eye back towards the road (fast component)


Moral of the story: In normal waking state, Cold component towards the side of stimulus, followed by fast component (cortex and brainstem doing their job well.)

In lethargic, the cortex is slow so fast component less pronounced

In Obtundation, Cortex affected. No fast component, just the deviation (Slow component).

In Coma, Even the brain stem is affected. So no movement at all. (That's how you know if the person actually is in Coma or is faking it)

Concept and story from Clinical Neuroanatomy Made Ridiculously Simple

Thanks for your time mate! I researched nystagmus on the internet (frankly spent a lot of time on it) and stumbled on few sources that cleared the concept for me, but your input did help me a lot so cheers for that!

I will post the link if you're interested: http://www.usmleforum.com/files/forum/2010/1/504944.php

[DrNewB]

Originally Posted by eizou

Thanks for your time mate! I researched nystagmus on the internet (frankly spent a lot of time on it) and stumbled on few sources that cleared the concept for me, but your input did help me a lot so cheers for that!

I will post the link if you're interested: http://www.usmleforum.com/files/forum/2010/1/504944.php

Thanks for the link

[Davit Eliauri]

Originally Posted by Dr.NickRiviera

A 29-year old man has a 1-week history of feeling dizzy. Warm water instilled into the left ear while the patient is supine elicits nystagmus with a quick phase to the left; warm water instilled into the right ear elicits no eye movements. Which of the following is the most likely site of a lesion?

A. Left frontal eye fields
B. Right frontal eye fields
C. Left pontine gaze center
D. Right pontine gaze center
E. Left vestibular apparatus
F. Right vestibular apparatus.

Of course F