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ANTERIOR CANAL BPPV -- and supine position triggered downbeating nystagmus (DBN)

Timothy C. Hain, MD Page last modified: July 17, 2014

The main BPPV page is here. This page is pretty technical (warning !)

Abbreviations used here:

Anterior canal or AC-BPPV may account for about 2% of cases of BPPV (Korres et al, 2002).

Ear Rocks

Displaced otoconia can migrate to any of the three semicircular canals. When it goes to the top canal, it is called "anterior canal BPPV". This type of BPPV is thought to be characterized by down-beating nystagmus (DBN) on lying flat, and upbeating nystagmus (UBN) on reassuming upright position.

 

Prevalence

It is best here to just say that the prevalence of AC-BPPV is low, and uncertain. It is uncertain because the diagnostic criteria are nonspecific, and there is simply a lack of solid evidence that the common DBN seen supine is due to AC-BPPV or something else (see following for a list of the "somethings").

Anterior canal BPPV is probably very rare because the anterior canal is the highest part of the ear. Debris would naturally tend to fall out of the posterior half of the anterior canal, and getting debris into the anterior canal would not be easy. From the geometry of the ear, it would seem likely that anterior canal BPPV might occasionally result as a complication of the Epley maneuver. In persons who don't spend a lot of time upside down, other than perhaps Yoga enthusiasts, it is difficult to imagine a plausible mechanism otherwise.

 

Dix Hallpike Test

The Dix-Hallpike maneuver diagnoses both posterior canal BPPV as well as contralateral anterior canal BPPV. Variants of the Dix-Hallpike maneuver may also treat anterior canal BPPV (see below).

The conventional (loose) criteria for AC-BPPV are a supine-position triggered DBN, with or without torsion.

Diagnosis

AC BPPV is almost certainly grossly over diagnosed, as the patterns of nystagmus attributed to AC BPPV by most clinicians make no sense.

What logic would say:

From basic vestibular physiology (i.e. Flourens, Ewald), nystagmus from the inner ear is mainly oriented in the plane of the stimulated canal. Because in AC BPPV, the stimulated canal is "up", on lying flat, one would expect that the torsion also would beat towards the "up" side (i.e. opposite side).

Anterior canal BPPV should also be mainly provoked (i.e. strongest) from the opposite ear to the side of the Dix-Hallpike maneuver -- in other words, if you get dizzy with DBN to the right side, the problem ear should be the left. Some authors have suggested that because the anterior limb of the anterior canal is oriented so that parts are near the sagittal plane, anterior canal BPPV can be provoked with a Dix-Hallpike maneuver to either side as well as in the "head hanging" position (Bertholon et al, 2002). We generally agree with this idea and we have also encountered a few patients who ONLY have nystagmus in the head-hanging position (but this doesn't prove that it is due to AC BPPV). On the other hand, the anterior canal as a whole is not at all aligned with the sagittal plane -- it is about 40 degrees away (Della Santina et al, 2005). Just because part of the canal is sagittal, does not mean that stimulation of the canal should cause purely vertical nystagmus in one segment, and mixed in another. It should be mixed all through.

In our experience, supine position triggered DBN more often beats (i.e. torsion) towards the "down" ear or just doesn't have any torsion at all. Both possibilities should be impossible for AC BPPV.

Furthermore, in AC BPPV, considering the physiology, there also should be an upbeating nystagmus on reassuming upright as well as a low level UBN all the time. In our very large experience with BPPV, while DBN supine is very common, especially with ipsi-torsion, UBN upright is rare.

So to summarize -- There are two sets of criteria for AC-BPPV. While people that fit the loose (illogical) criteria are common, almost nobody fits the strict (logical) criteria, and it may be that the whole syndrome is a misnomer.

Dogma:

AC BPPV is supposedly diagnosed by a positional nystagmus with components of downbeating and (sometimes) torsional movement on taking up the Dix-Hallpike position (shown above).

Alternative mechanisms to AC BPPV for supine DBN with contratorsion (torsion beating towards up ear)

Considering causes within the ear, a mixed-DBN/contratorsional nystagmus might also be caused by debris close to the common crus of the PC. In other words, following along the same logic as geotrophic-ageotrophic LC BPPV, especially after an Epley or Dix Hallpike maneuver, debris in the PC might move towards the ampulla/cupula rather than away. Here, the nystagmus should be strongest with the bad PC down, and the torsion should be oppositely directed. This nystagmus pattern is very uncommon (i.e. contra torsion). Although to our knowledge, this idea was first posted on this web page, this mechanism was also discussed at a 2013 conference in Siena Italy by two different research groups. Califano et al (2014) discussed this mechanism in detail in a recent paper and coined the name "apogeotropic posterior canal BPPV". Califano use the term "apogeotropic" rather than "contra" for the torsional component, but they are the same entity.

Yacovino et al (2014), suggested that AC-BPPV occurs "de novo" in about 38%, as a canal conversion in about 35%, and in individuals with previous BPPV but without a recent treatment, in 27%. Califano et al (2014) suggested that roughly 2.5% of all BPPV was the common crus mechanism, and 1.5% of all BPPV was the true AC mechanism. It seems to us that these statistics might depend on how the clinics treat their posterior canal BPPV, as some treatment protocols might tend to be incomplete and result in more of the common-crus type BPPV than others.

Mechanisms for supine DBN with ipsi-torsion (torsion beating towards down ear)

This nystagmus is not in a "canal plane", and thus should not be directly peripheral (due to the inner ear alone). It might reasonably be due to a mixture of a pure DBN, perhaps due to saccular damage or cerebellar damage, and an ordinary PC BPPV. See the next section for possible mechanisms of pure DBN. One would expect for this situation that the timing of the two components would differ - -i.e. the DBN should last longer than the torsion. We do not know if this is the case.

Supplemental material on the site DVD: Nystagmus of Anterior canal BPPV.

When there is DBN on supine without torsion -- pure DBN -- (e.g. Cambi et al, 2013), the origin is probably not BPPV of any type, as there is an intrinsic pairing between stimulation of the canals and a mixed torsion-vertical nystagmus. Here some alternative possibilities.

Anterior canal BPPV, especially when there is no torsional component, has a much wider differential than posterior canal (PC) BPPV, as it includes the numerous other causes of downbeating nystagmus. One should be considering other possible explanations - -especially cerebellar lesions, in persons with nystagmus attributed to AC-BPPV. See this link for a case of a person who was thought to have AC-BPPV, but actually had a brain tumor. It is very rare than anyone with dizziness has a brain tumor. It would seem to us unlikely that someone who clearly has dizziness from their ear, would have a central nystagmus either. So for this situation - -be wary, but don't expect to find much central disease.

A more speculative cause of pure supine DBN, is central adaptation. This idea allows for the appearance of DBN after treatment for PC BPPV, without attributing it to AC BPPV. Should debris on either the short arm of the PC (this location seems reasonable) or long arm of the AC (this location seems unlikely), it could load down the cupula and cause a tonic UBN. After a maneuver that moved debris out of either place, such as an Epley maneuver, there could be a DBN that had built up to counteract the peripheral UBN, via central adaptation. The rules for central nystagmus are not the same as peripheral nystagmus, they don't have to be in canal planes, and a purely DBN is conceivable. This logic suggests that a supine DBN that follows a successful Epley maneuver might not be AC BPPV, but rather might be central DBN. If there is both ipsitorsion and DBN, perhaps a mixture of residual PC BPPV and central DBN. This should be self-limiting.

Another possibility is canalith jam. The idea here is that debris from the PC "jams" some canal (presumably the PC), causing a constant nystagmus. It might jam causing negative pressure leading to upbeating/ipsitorsion, or positive pressure leading to downbeating/contratorsion. For this situation you would expect "canal plane" nystagmus, and no response for the canal plugged (should it possible to measure these things -- perhaps with the new "vHIT" device").

Treatment of Anterior Canal BPPV

Treatment of anterior canal BPPV has not been as well established as in typical BPPV and at the present writing (2012), there are no controlled studies. Thus we will mainly talk here about what we consider a reasonable approach. You can skip down to "our recommendation" if you just want to get to the take home message.

As a general rule, there is "only one" geometry to a maneuver to treat any particular canal type of BPPV, because however one maneuvers the person, in the end, you always have to bring the debris around the same circle of the canal. Thus, even though things might appear complex below, in essence, all of these maneuvers are just trying to get the person upside down, let the debris fall to the top of the canal, and then put them into a position where it will continue around the circle and go backwards into the vestibule.

Our "in the trenches" experience with these maneuvers is that they don't work nearly as well as the Epley maneuver does for PC BPPV. In other words, our thought is that the response rate of maneuvers for supine DBN is low -- perhaps < 50%, and that this is basically due to the lack of a clear cut method of diagnosing AC-BPPV. We think it is interesting that there is no controlled study of AC treatment at this writing (2014). The studies published to date, not only are uncontrolled, but also use loose diagnostic criteria. This is probably because almost nobody fits the strict criteria.

Honrubia et al (1999) mentioned a "reverse Epley" maneuver, and results in 4 cases. Similarly, a "reverse Semont" maneuver has been suggested. These maneuvers, starting with nose down to the side that makes the AC vertical, are at least somewhat logical, but their biomechanics are not as good as ones where the head is literally upside-down, as for the Kim or Yacovino maneuvers discussed below. In other words, less likely to work.

Rahko (2002) suggested a maneuver similar to the Gufoni maneuver for the lateral canal. Start with the head 45 deg down, then move to 45 up. This maneuver does not make much sense, as in at least one of the two positions, the AC must be horizontal, and we don't think it is currently in use today. It is possible that Rahko was actually treating lateral canal BPPV.

Crevits (2004), reported a total of 2 cases in which BPPV was successfully treated with a "prolonged forced position" procedure. In this procedure, there is an attempt to bring the head backwards as far as possible -- 60 degrees beyond supine, (in theory, upside down would be best), followed by return to upright and immobilization of the head in this position for 24 hours. In our opinion, the positions of this maneuver are reasonable, but the rationale for 24 hours of immobilization of the head is difficult to comprehend. It is clear both from biomechanical considerations (e.g. Squires et al, 2004) as well as from experience with other types of BPPV that, at most, debris moves in minutes. Also, the results of Kim (2005) and Yacovino (2009) see below, in a much shorter time, suggest that prolonged positions are not needed.

yacovino BPPV
Treatment for AC BPPV as proposed by Kim and associates (2005). In position 'b', the head is turned 45 degrees towards the symptomatic side. Note that the illustrations of the canals from the Kim article (shown above) are anatomically impossible artists renditions. Deep head hanging treatment for AC BPPV as proposed by Yacovino, Hain and Gualtieri. (2009). This treatment differs from that of Kim (above) in that the head is not turned to either side, and it is positioned so that it is further back with respect to horizontal in position 2.

Just a year later, Kim and associates (2005) described a more logical treatment maneuver for the anterior canal. Their modified maneuver is essentially just a deep Dix-Hallpike. They reported a cure rate of 96.7% in an uncontrolled study of 30 subjects. We find this very difficult to believe, as nothing is ever this good, and there are some other issues (see end of paragraph below), but still the authors seem to be enthused about the maneuver, and maybe it works.

The Kim maneuver is fairly logical, but it could be more logical- -in particular, position 'c' debris close to the cupula might not move around the turn. Also, if one accepts the idea that the most anterior part of the AC is nearly saggital, one should logically start this maneuver with deeper head-hanging to get that segment upside down, then go to the head 40 degrees to the symptomatic side. Note that the illustrations of the canal anatomy taken from the Kim paper (see above) are not anatomically correct -- you should use an actual physical model of the semicircular canals to work this out for yourself. As is the case for uncontrolled studies in general that seem to violate common sense and conventional experience -- like this one -- perhaps this study is simply overly enthusiastic.

Yacovino, Hain and Gualtieri (2009) reported results of using a maneuver similar to that of Kim in 13 patients. This again was an uncontrolled study, and the diagnostic criteria for AC BPPV were not as tight as suggested above (criteria were supine DBN with or without torsion). In 5 of these patients, the nystagmus arose after an Epley maneuver for PC BPPV. From the discussion above, other potential mechanisms than AC BPPV include long-arm PC BPPV, and central adaptation nystagmus. The maneuver in this study, like that of Kim, while designed for AC-BPPV, might also be effective for PC BPPV of any variety as prolonged inversion might move debris from close to the cupula to a position near the common crus for the PC. They reported "symptom free" status in 85%. Similar results were reported in a larger study (Yacovino et al, 2014).

For all of the supine AC BPPV maneuvers, there is a problem in that they may be physically impossible due to neck flexibility. One way to get around this is to use devices that flip the person upside down -- e.g. the Epley omniax, and similar devices. These are generally inaccessible, and thus it seems prudent to think about how to attain an upside down position, without a specialized machine.

Along this line, there is also a "forward" AC BPPV maneuver. In this maneuver, the patient is prone on a table, with the head over the end and bent forward off the end of the table, as if one was looking for a piece of gum under the mat table. Thus again the head is upside down. After a reasonable length of time (perhaps based on how long the downbeating nystagmus persists), one is flipped onto the back so that the debris falls towards the vestibule. This maneuver (so far unaccompanied by any clinical trial) may be the most reasonable for older patients where the head may be anteriorly positioned due to kyphosis. No study is yet available - -but as the geometry is identical as all of the other maneuvers, it seems likely to have similar results.

Our recommendation:

In our clinic setting in Chicago, we have had reasonable success in treating anterior canal BPPV -- roughly a 50% response rate -- (defined using loose criteria) with the "Deep head hanging maneuver" as illustrated above (Yacovino et al, 2009; 2014). This can be performed on a mat table, or if necessary, using a tilt table or similar gadget that can turn the patient upside down (e.g. Epley Omniax). It does not seem to us that the added effort of getting the patient upside down, is rewarded by a higher cure rate. Nevertheless, one would think that it should help.

This procedure is essentially the positioning of Crevit's maneuver, without the 24 hours of immobilization. It could also be considered as a simplified and deeper Kim maneuver. All of these maneuvers are really the same thing -- with minor variations. The idea is to invert the anterior canal, to allow debris to fall to the "top" of the canal, and then, on sitting, to allow it to further migrate into the common crus and then vestibule. This maneuver has an advantage over the "Kim" maneuver in that one does not need to know the affected side.

At this writing (2009), home treatment of AC BPPV has not been studied (unlike the case for PC BPPV). We are doubtful that it is effective at this writing (2013).

Suppose the patient really has something else ? Long arm PC BPPV should be treated with the Epley (see below). Central adaptation nystagmus needs no treatment. Other central nystagmus -- an MRI seems reasonable.

A controlled randomized study of a rational AC maneuver is needed.

Maneuvers that we are less enthused about (i.e. could be treating something else).

We, like Hetzler (2007) are unenthused about using the conventional Epley or Semont maneuvers to treat clear cut AC-BPPV (e.g. Herdman et al, 1996; Jackson et al, 2007). Oddly enough, Herdman states in her illustration that for the L AC, "note that the position changes are the same as in the treatment of the left posterior canal". The geometry of the AC is such that one would expect these maneuvers could even make it worse, because they involve nose-down positioning.

Still, these maneuvers would make some sense for debris in the "long arm" -- i.e. top of the PC, and falling the opposite way as usual BPPV. A clue may be that the torsional component for this mechanism should be "contra" -- i.e. directed towards the up ear. Here one is not treating AC-BPPV at all, but variant PC BPPV.

Overall, the diagnosis of AC-BPPV is often not "clear-cut", so it could be reasonable to be liberal with maneuvers.


WHERE ARE ANTERIOR CANAL BPPV EVALUATIONS AND TREATMENTS DONE?

The Vestibular Disorders Association (VEDA) maintains a large and comprehensive list of doctors who have indicated a proficiency in treating BPPV. Please contact them to find a local treating doctor.

Because anterior canal BPPV is more complex than posterior canal BPPV, and includes far more central nervous system conditions (i.e. brain tumors, strokes, Chiari Malformation) as alternative possibilities, we think that seeing a neurologist experienced with dizziness is usually best option.

Our own practice is located in Chicago Illinois. Chicago Dizziness and Hearing, 645 N Michigan, Suite 410, Chicago 60611


REFERENCES CONCERNING ANTERIOR CANAL BPPV:

Copyright July 17, 2014 , Timothy C. Hain, M.D. All rights reserved. Last saved on July 17, 2014