Diagnosing BPPV: interpreting nystagmus case 8

[Liping Li]

In the video, since the eye is L eye and the horizontal beating is away from the nose, the beating I think should be L horizontal nystagmus. However, the correct answer is R horizontal nystagmus. I read the explanation and still feel confused why it’s R horizontal nystagmus. Can anyone explain it? Thank you very much!

[Chrissy Durrough Lugge]

Thanks for this question! Remember – nystagmus is named for the FAST phase relative to the patient. In this case, the fast beat is actually toward the nose (since it is the left eye, the fast phase is to the right). Watch the video again and see if you can pick up on it. At the 6-second mark, you will see horizontal nystagmus with a fast phase going to the patient’s right. We are looking at the patient’s eyes, so the viewer will see nystagmus beating across our screen to the left, which is the patient’s right.

Chrissy

[Liping Li]

Got it. I focused too much on the first 6 sec and ignored the fast phase nystagmus after it. I did see the fast beat to L on screen which should be patient’s right. Thank you for the clarification!

[Alyson Huber]

For interpreting nystagmus on case 3, It’s very difficult for me to see that the upbeat is toward the right… I see the torsion and quick beat going toward the left side, since I am looking at the right eye. Am I looking at this incorrectly? Should I be thinking of it as clockwise vs counter-clockwise?

[Chrissy Durrough Lugge]

Hi Alyson,
Are you working through the “Diagnosing BPPV: Interpreting Nystagmus” tutorial or the “Diagnosing BPPV: Bonus Videos”?

Since you refer to looking at only one eye, I am assuming it is the “Diagnosing BPPV: Interpreting Nystagmus” tutorial (case 3 on the bonus videos is a binocular video) – and I think you might actually have it mostly figured out. We are looking at the patient’s LEFT eye in this video. As you could tell the nystagmus is torsional and upbeating. On our screens, the fast phase is going to the right, which is the patient’s left. The patient has upbeating and left torsional nystagmus, consistent with left posterior canal involvement.

This nystagmus is more subtle than some of the other examples. Finding a specific point on the patient’s eye can lend some clarity on what is actually happening. In this case, I think some of the markings right around the pupil are the easiest to identify the nystagmus’ characteristics.

You can think of it as clockwise and counterclockwise, but this can easily be converted to left/right (personally, I find it simpler to think in terms of left/right). CW/CCW would still be from the patient’s vantage point. Clockwise nystagmus would be torsional with the fast phase to the patient’s right. Counterclockwise would be torsional with the fast phase to the patient’s left. This patient has CCW upbeating nystagmus.

Chrissy

[Alyson Huber]

SORRY! I should have been more clear. I was referring to the Vimeo video from the example of the case based exam #3, question number 2. It is the patient’s right eye and at first it looks to me as if the fast phase is going in medially toward the left. After watching it a few more times, I can slightly see how the fast phase is going toward the right. Hopefully with more practice it will clear up for me.

Is there any pattern with the direction of the dix-hallpike being performed and the symptomatic side being the involved ear? For example, since the is a dix-hallpike with right head rotation and there is positive nystagmus, can it be assumed that the involved canal is on the right side? Or would a left dix-hallpike also produce this result? THANK YOU!!

[Chrissy Durrough Lugge]

Ha! Sorry for the long explanation of the wrong video!

This is a grainy video. A big hint is that you know he is in right Dix-Hallpike. Left posterior canalithiasis wouldn’t produce this robust response in right Dix-Hallpike position. For me, the nystagmus is most clear when the patient has his eye open completely and the nystagmus starts to “settle” a bit – around 17 seconds and 28 seconds are little windows where I think it is easier to see.

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