Timothy C. Hain,
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The main BPPV page is here.
Displaced otoconia can migrate to the posterior canal, which is the lowest part of the ear when one's head is upright. Debris might also migrate into the lateral canal as well as the superior canal. For the superior canal, debris would tend to fall out spontaneously unless it was at the ampulated end. For the lateral canal, debris also would tend to fall out spontaneously. This may be the reason that non-posterior BPPV is unusual.
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.
There are several rare variants of BPPV which may occur spontaneously as well as after the Brandt-Daroff maneuvers or Epley/Semont maneuvers. They are thought to be caused by migration of otoconial debris into canals other than the posterior canal, such as the anterior or lateral canals. It is also theoretically possible for many aberrant patterns of BPPV to occur from an interaction of debris in several canals, location of debris within the canal, and central adaptation patterns to lesions. For this reason, in clinical practice, atypical BPPV is first treated with maneuvers as is typical BPPV, and the logic outlined below is entered into only after treatment failure.
Lateral canal BPPV is the most common atypical variant, accounting for about 3-9 percent of cases (Korres et al, 2002). Most cases are seen as a consequence of an Epley maneuver. It is diagnosed by seeing a horizontal nystagmus that changes direction depending on the down ear. The best position to see this nystagmus is not the Dix-Hallpike maneuver. Rather one starts with the body supine, head inclined forward 30 degrees, and then turns the head to either side.
The nystagmus can be either always towards the ground ("geotrophic") or always towards the sky ("ageotrophic"). (Bertholon et al, 2002) Nystagmus that is "ageotrophic" is thought to be caused by debris that is further around the canal and closer to the ampulla, than "geotrophic" nystagmus. Lateral canal BPPV can cause a very strong and prolonged vertigo. People with lateral canal BPPV are also generally more disturbed by ordinary sideways head-movements than people with posterior canal BPPV. Lateral canal BPPV may occur commonly but may also be self treated as people roll back and forth at night naturally during sleep (Korres et al, 2002).
In some cases, usually ones where the condition occurs spontaneously rather than as a consequence of treatment for regular BPPV, debris is adherent to the cupula. This causes a very prolonged and refractory nystagmus.
One should be more concerned in this condition that there is a cause other than BPPV. Disorders that resemble BPPV are discussed here.
When lateral canal BPPV follows a maneuver, the "bad" ear is considered to be the same one with the posterior canal BPPV.
In idiopathic cases with geotrophic nystagmus the "bad" ear is assigned to the side with the stronger nystagmus. With ageotrophic nystagmus, the bad ear is assigned to the side with the weaker nystagmus. Sometimes there will need to be judgment call on the part of the examiner, integrating together information about nystagmus and other data about which ear is diseased (such as hearing, fullness and the like). When horizontal nystagmus follows an Epley maneuver for posterior canal BPPV, in nearly all instances the most likely "bad" ear is the one in which posterior canal type BPPV was seen previously.. In situations where the side is unclear, it is our feeling that it may be worthwhile to first try treating the more likely side, and then switch to the other side after a week.
Treatment of lateral canal BPPV has not been as well established as in typical BPPV. In the author's experience, lateral canal BPPV after an Epley maneuver nearly always resolves without any treatment after a week. Accordingly, the lack of a control population in most of the studies discussed below is a serious flaw.
|Log roll exercises for Lateral Canal BPPV.|
The "log roll" exercises, are a procedure where an individual is rolled in steps of 90 deg, starting supine/affected ear down, to supine, to affected ear up, to nose-down, and then to sitting at intervals of 30 seconds or one minute. This procedure seems very reasonable and it is the one that we use in our own practice. There is a report of 75% efficacy (15/20) of a variant procedure (e.g. Fife, 1998) called the "iterative full-contralateral roll", going from supine nose up, a full 360 degrees in 90 degree increments, rotating towards the good ear. This procedure is performed once or twice in the clinic and repeated at home for 7 days. It seems to us that the difficulty of establishing which is the "bad" ear is an obvious drawback of this procedure and in some situations, we do the log roll to one side for a week, and follow with the log roll to the other side for another week. We also feel that it is preferable to begin with the bad-ear down rather than supine, for situations where there is debris close to the ampula. Vibration of the mastoid might theorecically add to efficacy of this procedure but no studies are available at the present writing. A DVD that provides more information about the log-roll is available here.
A variant of the Brandt-Daroff exercises (see here for details) can be used in lateral canal BPPV where the head is positioned upright on the trunk instead of inclined. This "modified Brandt-Daroff" also seems somewhat reasonable and might serve as a fall back strategy when the log-roll doesn't work. An big advantage of the modified Brandt-Daroff is that the side of the lesion need not be established. As previously mentioned, this can be difficult with lateral canal BPPV. At this writing, it is unclear which (if any) procedure is best. Simply sleeping with the "affected" ear up has been reported to cure about 75% of patients (see Vannucchi et al, 1997). This positioning is similar to recommended for posterior canal BPPV after the Epley or Semont maneuver, except for the 45 degree angle of the head with respect to the horizontal is not used here. Considering the mechanics of the situation, one would expect that bad-ear up would work only for case where the debris is not close to the ampula. In other words, it would not be expected to work for the ageotrophic variant of lateral canal BPPV.
Most recently, Appiani and associates (2001) proposed a "liberatory maneuver" for lateral canal BPPV. It is essentially a variant of the modified Brand-Daroff exercises, involving side-lying to the good side until geotrophic nystagmus stops and then one minute more, a quick turn of the head 45 degree downward remaining in this position for 2 minutes, and then a return to the upright position. A cure rate of 78% was reported. To us, this procedure seems likely to fail in several situations -- 1). If debris is close to the cupula 2). If debris is adherent to the cupula. Situation #1 might reasonably occur in half patients, even those with geotrophic nystagmus, as debris might migrate in two directions at the same time. The advantage of this procedure compared to the "iterative full contralateral roll" and the "modified Brandt-Daroff", is that it is a single step method.
Neuroradiological investigation may be warranted in persons who fail to improve these maneuvers as nystagmus similar to lateral canal BPPV can occur in persons with cerebellar lesions.
Currently it is generally felt that this is a poor prognosis variant of lateral canal BPPV. Because debris is stuck to the cupula, it may not be easily treated by physical maneuvers aimed at dislodging it. Debris could be stuck to either side of the cupula, leading to some uncertainty about which is the best way to treat it. Also, this pattern of nystagmus may derive from central disturbances.
Our approach is to initially try the usual treatments for lateral canal BPPV, possibly with the addition of mastoid vibration. If this fails, we will recommend a variant Brandt-Daroff exercise as tried above. Generally anti-emetic and anti-nausea treatment is necessary when treating cupulolithiasis.
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. Our own practice is located in Chicago Illinois. For uncomplicated BPPV treatment, we generally schedule new patients to see one of our physical therapists.
OFFICE LOCATION: Chicago Dizziness and Balance, 645 N Michigan, Suite 410, Chicago 60611
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(c) 1997-2002 Timothy C. Hain, email@example.com