Of course otoconia can theoretically find its way into the Anterior Canal creating Anterior Canal BPPV, but come on... how often would you really see this as a clinician? Most of my patient's in the older population aren't performing head stands in yoga class for any length of time. I was so convinced that I would rarely, or even ever, see this that I didn't even put a ring on the anterior canals of my early Functional Inner Ear models. Boy, was I proven wrong.
In June of this year, I evaluated a woman who came into the clinic complaining of positional related vertigo. At the initial evaluation she reported that every time she went to lie down in bed or turn to her right side in bed, she would feel that the room would spin for about 30 seconds, and then it would go away. She stated that she had something similar happen to her a year ago, and after some maneuvers at the ENT, the vertigo resolved. My first thought was "awesome! Text book BPPV". At this visit, I was right. Her testing revealed that she only presented with Right Posterior Canal BPPV, Canalithiasis-type. She had some little unexpected eye movements throughout the Epley maneuver, but all-in-all she was pretty straight forward, and tested negative after 2 cycles of a Right Modified Epley Maneuver. Here is the testing from her first visit:
After the patient's first visit, I was pretty confident that she'd test negative on positional testing the next time she came in. When she returned 7 days later, she reported that she initially felt much better and that her symptoms were resolved after the Modified Epley maneuvers for a few days. HOWEVER, two days before returning for her second visit she was working out with her personal trainer who had her performing inverted push-ups over a stability ball. Something like this I'd imagine:
She stated that after performing that exercise, her dizziness symptoms returned, but they were a little different. She continued to feel dizziness with changes in position, but the room wasn't spinning like it had before. My immediate thought was "no way... really? Could she have converted herself to Anterior Canal BPPV?" Up to this point, I hadn't studied Anterior Canal BPPV too closely. All I remembered was that a typical indication was down beating nystagmus with positional testing. When I first dropped her into a Right Dix-Hallpike, I didn't see much. Then she started to feel dizzy, and when I removed fixation, there it was... down-beating nystagmus.
Still skeptical, I jumped onto Dr. Timothy Hain's amazing website www.dizziness-and-balance.com. (everyone really should know about this site... and if you haven't been there, check it out right now!) I quickly looked at his information about Anterior Canal BPPV, and we tried the deep head hanging maneuver. The patient reported feeling a little better, and I asked her to return a few days later, giving me the chance to do some more extensive research. I immediately dove into any journal article I could find, and I came across "Anterior canal BPPV, and apogeotropic posterior canal BPPV: two rare forms of vertical canalolithiasis" by L. Califano et al.
This is a good article which was published in 2014. Over the course of 16 months, the authors observed 934 BPPV patients. From that patient population, they found a very small prevalence of two rare forms of BPPV. One form was Anterior Canal BPPV (1.2% of their cases), and the other was what they described as Apogeotropic Posterior Canal BPPV (2.5% of their cases). The difference in these diagnoses is where the displaced otoconia are located. Take a look at Figure 1 from the article which differentiates Traditional Posterior Canal BPPV and Apogeotropic Posterior Canal BPPV .
Left posterior canal BPPV in sitting position. (a) Traditional Posterior Canal: otoliths are in the ampullary arm of the canal; (b) Apogeotropic Posterior Canal: otoliths are in the non-ampullary arm of the canal.
Below is a picture showing otoconia displaced in the Anterior Canal.
Both conditions are rare, and both conditions cause the presentation of down-beating nystagmus. There is a small difference, however. Anterior Canal BPPV should present with down beating nystagmus but also with an ipsilateral torsional component when in a Dix-Hallpike or Head Hang position. Apogeotropic Posterior Canal BPPV presents with down-beating nystagmus and a contralateral torsional component. Here's my problem... I did not observe any torsional component to my patient's Down Beat Nystgamus.
Typically when I see persistent Down Beat Nystagmus, I usually start to think central nervous system involvement. The article suggests that this should be your first thought considering it is typically associated with cerebellar diseases. However, I felt comfortable excluding central involvement because Down Beating Nystagmus and all other central findings were not found my the patient's initial evaluation. Another thought I had included the idea that she could have a posterior canalith jam... but that's a topic for a different blog on a different day. I ruled that possibility out too. What made me feel more confident in an Anterior Canal BPPV diagnosis was when the article sited that "a unilateral form of Anterior Canal (BPPV) can cause a vertical down-beating nystagmus, due to the orientation of the anterior canal which is closer to the sagital plane (usualy by a 41 degree angle) than the posterior canal (usually by a 56 degree angle). These two considerations are enough to justify the frequent occurrence of a purely vertical down-beating nystagmus on both sides even in unilateral forms".
Whew! Okay! Here's how I summed my case up, and justified Anterior Canal BPPV:
I'm a little more confident in my diagnosis that the patient did in fact convert herself to Right Anterior Canal BPPV, Canalithiasis-type. At the patient's third and final visit, all positional tests were negative. Only faint down-beating nystagmus was observed with fixation removed in a head hang position, and the patient was asymptomatic.
Here is an example of how the Deep Head Hang maneuver is performed and how the otoconia moves through the maneuvers:
I was recently very fortunate to email back and forth a little bit with Dr. Kimberley Bell, DPT of The Bell Method (be sure to check her website out too!). I shared with her my excitement to have seen 1 case of Anterior Canal BPPV, to which she replied "I see a lot of anterior canal BPPV that is missed by other providers and I think it's because I live in Encinitas California, which boasts to be the "yoga capital" of the world. Most of my clients with anterior canal BPPV are middle-aged women - who I believe had posterior canal BPPV that they were trying to ignore - and they went to their regular yoga class and did a headstand, a handstand or some kind of an inversion like downward dog pose." She went on to note that she also sees cases of Anterior Canal BPPV where head trauma likely caused the displacement of the otoconia after a motor vehicle collision or a sports-related concussion, and then the patient moved into an inverted position
I have to say, my position on Anterior Canal BPPV has greatly changed. I would suspect to see the prevalence of this condition rise as our patient population continues to be more active, even later on in life. In the Rockville, Maryland area, it is becoming increasingly common for senior and community centers to offer yoga and tai chi classes to help individuals improve their balance and mobility.
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