Timothy C. Hain, MD Page last modified: April 20, 2013
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).
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.
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 somthing 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.
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.
AC BPPV is almost certainly grossly overdiagnosed, 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 saggital 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 saggital plane -- it is about 40 degrees away (Della Santina et al, 2005). Just because part of the canal is saggital, does not mean that stimulation of the canal should cause purely vertical nystagmus in one segement, 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 stict (logical) criteria, and it may be that the whole syndrome is a misnomer.
- Loose criteria -- supine DBN, with or without torsion, in any direction, but usually ipsitorsional referred to the down side
- Strict criteria -- supine DBN, with contra-torsion referred to the down side, and UBN on upright
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).
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 ampula/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.
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.
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 appearence of DBN after treatment for PC BPPV, without attributing it to AC BPPV. Should debris on either the short arm of the PC (this locaiton 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 concievable. 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.
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.
Our "in the trenches" experience with these manuevers 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 (2013). The studies published to date, not only are uncontrolled, but also use loose diagnostic citeria. This is probably because almost nobody fits the strict criteria.
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 impressive results of Kim (2005) see below, in a much shorter time, suggest that prolonged positions are not needed.
|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 cruse for the PC. They reported "symptom free" status in 85%.
In our clinic setting in Chicago, we have had reasonable success in treating anterior canal BPPV -- roughly a 50% respone rate -- (defined using loose criteria) with the "Deep head hanging maneuver" as illustrated above (Yacovino et al, 2009). 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. 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).
Some clinicians use "reverse" versions of treatments for PC BPPV - -for example the "reverse" Semont (starting with nose down to the asymptomatic side), or the "reverse" Epley (again starting with nose down). These treatments are somewhat geometrically reasonable, although less so than the Kim or deep Dix-Hallpike discussed above. We are doubtful that these treatments are effective.
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 maneuver is needed.
We, like Hetzler (2007) are unenthused about using the conventional Epley or Semont maneuvers to treat clear cut AC-BPPV (e.g. Jackson et al, 2007). The geometry of the AC are such that one would expect these maneuvers could even make it worse, because they involve nose-down positioning.
On the other hand, these maneuvers would make some sense for debris in the "long arm" of the PC. Here one is not treating AC-BPPV at all, but variant PC BPPV. Also, the diagnosis of AC-BPPV is almost never "clear-cut", so would seem reasonable to be liberal with maneuvers.
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 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
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