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Timothy C. Hain,
MD
Page last modified:
December 30, 2007
Spanish Version of Lateral Canal Page
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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 canal 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 variants of BPPV (Benign Paroxysmal Positional Vertigo) 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 3-12 percent of cases (Cakir et al, 2006; Korres et al, 2002; Hornibrook, 2004). In the author's experience, most cases are seen as a consequence of an Epley maneuver, but others find that spontaneous occurence is more common (Hornibrook, 2004). 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 ("geotropic") or always towards the sky ("ageotropic", or "apogeotropic" -- we will use the shorter construction ). (Bertholon et al, 2002) Nystagmus that is "ageotropic" (about 25%) is thought to be caused by debris that is further around the canal and closer to the ampulla, than "geotropic" nystagmus (about 75%). It is unlikely that debris is actually adherent to the cupula as this should not cause much vertigo (Hain et al, 2005).
Lateral canal BPPV can cause a very strong and prolonged vertigo. People with lateral canal BPPV are also generally more disturbed by ordinary sideways rotational 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.
Supplemental material
on the site DVD: Movie
of lateral canal BPPV
When lateral canal BPPV follows a treatment maneuver for posterior canal BPPV, the "bad" ear is considered to be the same one with the posterior canal BPPV.
In idiopathic cases with geotropic nystagmus the "bad" ear is assigned to the side with the stronger nystagmus. With ageotropic nystagmus, the bad ear is assigned to the side with the weaker nystagmus.
Han et al (2006) recently suggested that the nystagmus seen on lying supine is can be used to determine which ear is affected. The methodology here is that the patient is initially sitting with head bent down for 3 minutes, and then rapidly brought into the supine position, with the head on a pillow. For geotropic nystagmus, nystagmus is away from the affected ear, and for ageotropic, towards the affected ear. In other words, for geotrophic nystagmus, the nystagmus follows the general rules for paretic ears, and vice-versi for ageotrophic nystagmus.
Some authors feel that a "null point" can be found, and the bad ear is on the side of the null point (Bisdorff and Debatisse, 2001). We find this generally implausible as if debris is movable within the canal, it should always die away, and thus there is no null point. If useful, it should only apply to cupulolithiasis, which is very rare.
Usually 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 practice to first treat the more likely side with home exercises, 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.
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| 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 theoretically add to efficacy of this procedure but no studies are available at the present writing.
Supplemental material
on the site DVD: Movie of the log
roll exercise
We offer a home treatment DVD that illustrates the Log-roll exercises.
Another variant is to move the head briskly towards the good ear during each step, which might add an inertial component to the repositioning process (Lempert and Tiel-Wielck, 1994). However, theory suggests that inertia contributes very little (Hain et al, 2005).
Several other procedures are discussed in a recent paper (Libonati et al. 2003)
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 ageotropic variant of lateral canal BPPV.
Most recently, Appiani and associates (2001; 2005) reviewed several repositioning maneuvers for lateral canal BPPV. Many of them are named after their inventor -- for example, the "Gufoni" maneuver. They generally involve side-lying for 2 minutes, a turn of the head 45 degrees, remaining in this position for 2 minutes, and then a return to the upright position. Abrupt movements of the head are suggested in these maneuvers - -we see no harm in doing this, but there is also unlikely to be a benefit (Hain et al, 2005).
For the geotrophic variant, one starts with the good ear down, and then proceeds to nose down. For the ageotrophic variant, a full log roll is more appropriate. For these maneuvers, one must both know if the nystagmus is geotrophic/ageotrophic as well as know the side of debris (which is not always the clearest).
The main advantage of these procedures are that they may be quicker as they cut out some of the useless steps of the Log-roll. We agree with the logic that the full log-roll is not always necessary. Nevertheless, for most situations, and especially when not done with apparatus to examine eye movements, the log-roll is the safer option.
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.
Little is known about recurrence of lateral canal BPPV. Sakaida and others (2003) reported that lateral canal BPPV recurs more frequently than posterior canal BPPV (by about a factor of two). Their report was based on a total of only 19 patients with lateral canal BPPV.
Currently it is generally felt that this is a poor prognosis variant of lateral canal BPPV (although not all agree -- e.g. Bisdorff and Debatisse, 2001). 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. Cupulolithiasis should not cause a strong nystagmus according to hydrodynamic theory (Hain et al, 2005).
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, 233 E. Erie, Suite 701, Chicago 60611
Published literature referred to above:
(c) 1997-2006 Timothy C. Hain, M.D.
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