Which side is affected in lateral canal BPPV?

From the rate of vertigo talks you can probably infer that either I must be very interested In or very insecure with vertigo. In fact, both is true.

So here is today’s problem: assume we know how to recognize horizontal canal BPPV and how to differentiate it from the other forms. Then there is still the difficulty in determining the affected side, because often enough it is not evident at all (this is not just my experience).

More concretely, we have a 56 yo saleswoman that wome up with extremely disabling vertigo. The world started spinning (horizontally, she says) when she turned over in bed to her alarm clock and she is not able to move since then, vomiting profusely on the slighest head turn. We managed to throw her around through our basic screening maneuvers – Dix-Hallpike and head-roll-test (also known as Paganini-McLure), where she showed purely horizontal decrescendo nystagmus towards the underlying ear on turning to either side – this is geotropic nystagmus. There is slightly more vertigo on turning to the left äs compared to right, but the nystagmus is pretty much the same.

Many maneuvers have been proposed for this situation and there is even some basic data about test theoretic properties of some of them. From this evidence I suggest the following successive tests (which actually can be performed during the screening phase).

  • History: which side is worse to turn to when supine? About 56% of patients can determine that and they usually are right.
  • Pseudospontaneous nystagmus: 56,2% have a spontaneous nystagmus when sitting straight, which – in the canalolithiasis situation – will abate eventually and is due to the purported angle of about 20-30° the lateral canal has wrt the horizontal plane (frontal arm is higher up than the other).
  • Lying down = supine nystagmus: in the so called Asprella diagnostic maneuver (which I love as a screening method for positional vertigo) you just move your patient quickly to the supine position, holding the head straight and record eye movements. In most of positional vertigos some nystagmus will come up and depending on the form of nystagmus you perform other maneuvers. Well, in this position about 75% (!) of lateral canal BPPV patients have some nystagmus and you can use the direction of nystagmus to determine the affected side (see table below).
  • Nystagmus intensity during the head-roll-test: due to some of Ewald’s laws (in fact, the second), nystagmus should be worse on the affected side in canalolithiasis. This happens to be the case in about 81% in the above mentioned article.
  • Bow-and-lean-test: when you bow the head of the sitting patient over the 30° angle the affected lateral canal has wrt the horizontal plane you should be able to evoke a the bow- or bending-nystagmus in about 59%. When leaning back a similar nystagmus can be observed (this is actually the pseudospontaneous nystagmus mentioned above). Both happens in only 40%.
  • Head-shaking nystagmus: any proper vertigo workup should include the screening for head shaking effects. The nystagmus evoked can be due to several reasons, but in lateral canal BPPV it produces a nystagmus in 62,5%.

Performing all of these maneuvers and then integrating the results with the table below, you should get the affected side right most of the time. Yet, if your treatment maneuver is then not effective, you should try the other side at least once, before starting a workup for other etiologies (central positional vertigo) as well.

 

Geotropic

R

L

Apogeotropic

R

L

Vertigo worse when supine
and turning to

the affected side

R

L

the unaffected side

L

R

Pseudospontaneous nystagmus towards

the unaffected side

L

R

the affected side

R

L

Lying down (supine) nystagmus towards

the unaffected side

L

R

the affected side

R

L

Nystagmus worse during head roll test towards

the affected side

R

L

the unaffected side

L

R

Bowing nystagmus
towards

the affected side

R

L

the unaffected side

L

R

Leaning nystagmus
towards

the unaffected side

L

R

the affected side

R

L

Head shaking nystagmus towards

the unaffected side

L

R

the affected side

R

L

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