ANTERIOR CANAL BPPV

Timothy C. Hain, MD Page last modified: January 20, 2008

The main BPPV page is here.

Anterior canal 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". Debris can not only migrate into the long arms of the canals, but might also become adherent to the cupulae. This is called "cupulolithiasis". Injuries to the cupula such as due to infection or poor circulation can also, in theory, cause cupulolithiasis.

Diagnosis

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

The Dix-Hallpike maneuver diagnoses both posterior canal BPPV as well as contralateral anterior canal BPPV.

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

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. An unsolved puzzle right now has to do with the torsional vector of AC nystagmus. From basic vestibular physiology, one would expect that it would beat towards the "up" side, but in our experience, it more often beats towards the down side, or just doesn't have any torsion at all.

Anterior canal BPPV can be provoked from the opposite ear to the side of the Dix-Hallpike maneuver -- in other words, if you get dizzy to the right side, the problem ear might 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. 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).

Anterior canal BPPV is probably rare because the anterior canal is normally 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.

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 (2007), there are no controlled studies. Thus we will mainly talk here about what we consider a reasonable approach.

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.

Just a year later, Kim and associates (2005) described a more logical treatment maneuver for the anterior canal. Their modified maneuver resembles Epley's CRP maneuver for posterior canal BPPV but it omits the nose-down position, which would be expected to worsen AC BPPV. They reported a cure rate of 96.7% in an uncontrolled study of 30 subjects. The Kim maneuver is logical, but we are concerned that in 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 the deep head-hanging to get that segment upside down, then go to the head 40 degrees to the symptomatic side.

In our clinic setting in Chicago, we have had good success in treating anterior canal BPPV with a "deep Dix-Hallpike", that gets around this particular problem. This can be performed on a mat table or using a tilt table. This procedure is essentially the positioning of Crevit's maneuver, without the 24 hours of immobilization. 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. An advantage of this maneuver is that determining the side of AC BPPV is not required.

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

Maneuvers that we don't reccomend:

We are unenthused about using the Epley or Semont maneuver to treat 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, the maneuver of Kim and associates is logical because it omits the nose-down position.

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 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:

• Bertholon, P., A. M. Bronstein, et al. (2002). "Positional down beating nystagmus in 50 patients: cerebellar disorders and possible anterior semicircular canalithiasis." J Neurol Neurosurg Psychiatry 72(3): 366-72.
• Crevits, L. (2004). "Treatment of anterior canal benign paroxysmal positional vertigo by a prolonged forced position procedure." J Neurol Neurosurg Psychiatry75(5): 779-81.
• Della Santina and others. Orientation of Human Semicircular Canals Measured by
  Three-Dimensional Multiplanar CT Reconstruction. JARO 6: 191–206 (2005)
• Jackson et al. Anterior Canal Benign Paroxysmal Positional Vertigo: An Underappreciated Entity. Otology & Neurotology 28:218-222, 2007
• Kim YK, Shin JE, Chung JW. The effect of canalith repositioning for anterior semicircular canal canalithiasis. ORL J Otorhinolaryngol Relat Spec. 2005;67(1):56-60.
• Squires, T., M. Weidman, T. Hain, et al. (2004). "A mathematical model for top-shelf vertigo: the role of sedimenting otoconia in BPPV." J. Biomech37(8): 1137-1146.