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\begin{document}

\title{Benign Paroxysmal Positional Vertigo: A Lesson in Clinical Reasoning}



\author[1]{Lisa Young}%
\author[2]{Shervin Badihian}%
\author[1]{David Zee}%
\author[1]{David E. Newman-Toker}%
\author[3]{Kevin Kerber}%
\author[4]{Anita Bhandari}%
\author[5]{Rajneesh Bhandari}%
\affil[1]{Johns Hopkins School of Medicine}%
\affil[2]{Cleveland Clinic Neurological Institute}%
\affil[3]{The Ohio State University}%
\affil[4]{Vertigo and Ear Clinic}%
\affil[5]{NeuroEquilibrium Diagnostic Systems Pvt Ltd}%


\vspace{-1em}



  
  \date{June 10, 2024}


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\textbf{Key Clinical Message}

Repositioning maneuvers for benign paroxysmal positional vertigo (BPPV)
designed to induce otoconial movement in one canal can trigger or treat
BPPV in other canals. We suggest for standardized testing protocols to
ensure correct diagnosis of BPPV.

\textbf{MeSH keywords} : BPPV; positional vertigo; horizontal canal;
positional nystagmus; case report

\textbf{Background:}

Benign paroxysmal positional vertigo (BPPV) is a common cause of
episodic vertigo in which otoconia (calcium carbonate crystals) become
detached from their normal location on the macula of the otolith
organs.{[}1{]} They can then find their way into the semicircular canals
(SCC), become free-floating or attached to the cupula, and create
abnormal sensations of motion when the position of the head is changed
with respect to the pull of gravity. BPPV of the horizontal canal
(hcBPPV) is less commonly diagnosed than BPPV of the posterior canal
BPPV (pcBPPV), in part because most emergency department and primary
care physicians do not attempt to distinguish the canal variants.{[}2,
3{]} The supine roll test (SRT) is primarily used to diagnose hcBPPV,
while the Dix-Hallpike test is primarily used to diagnose pcBPPV.{[}4,
5{]}

BPPV is usually treated with particle repositioning maneuvers that move
the otoconia out of the SCC: the Epley or Semont maneuvers for pcBPPV
and, for example, the Gufoni, Zuma, or Lempert (barbeque roll) maneuvers
for hcBPPV.{[}4-7{]} We report here a woman with hcBPPV who came to the
emergency department with acute positional vertigo and positional
nystagmus and experienced a favorable outcome despite the wrong side and
the wrong canal being diagnosed and consequently receiving the wrong
treatment maneuver. To explain this seeming paradox, we simulated the
movement of otoconia within the labyrinth in a right-sided hcBPPV in
response to an Epley treatment maneuver for left-sided pcBPPV. Our
simulations suggest that an extended Epley maneuver (i.e., the patient's
head being turned beyond the conventional 45\textsuperscript{o} angle to
60\textsuperscript{o} in the second step) caused the otoconia to leave
the horizontal SCC, resulting in this patient's successful outcome.

\textbf{Case Report:}

A 19-year-old woman came to the emergency department around noon because
of acute vertigo with unsteadiness and light-headedness triggered by
changing her head position. She woke up around 3:00 am with vertigo on
the day of the emergency department visit. Her symptoms partially
subsided when lying in bed and not moving. She denied headaches,
photophobia, migraines, vomiting, diarrhea, recent viral illness, head
injury, loss of hearing, or trauma. She previously had a similar episode
of vertigo that resolved on its own. She had no other relevant medical
history.

With the present episode, the emergency department physician performed a
Dix-Hallpike maneuver and diagnosed a \emph{left-sided BPPV,}presumably
of the \emph{posterior canal} , though the details of any elicited
nystagmus were not reported. The patient was treated with
a\emph{left-sided Epley} maneuver, and upon a repeat Epley maneuver, her
symptoms and nystagmus were documented as resolved by the emergency
department physician. During the first Epley maneuver, the patient
developed vertigo when lying with her head turned to the left side.
After her head was moved to point to the floor for two minutes more, her
vertigo stopped. No imaging was obtained, and the patient was discharged
directly from the emergency department with a diagnosis of
a\emph{left-sided BPPV} , presumably \emph{pcBPPV.}

While the patient was in the emergency department, she was also enrolled
in a clinical trial to assess her vertigo symptoms. A video-oculography
(VOG) study was obtained by our research staff before undergoing any
treatment maneuvers. The VOG study was not repeated after the emergency
department physicians' treatment, as the patient had been discharged
following the resolution of symptoms. The details of the recording and
analysis are described in the legend of Supplemental Video 1. Hearing
was normal.

Video Head Impulse Testing (vHIT) was performed for the horizontal
canals, and gains were within normal limits without corrective saccades
(head left, 0.83; head right, 0.97). With the VOG, with the patient
sitting upright in the dark at center gaze, there was a right-beating
spontaneous nystagmus of 1-2 \selectlanguage{ngerman}°/s. In the supine position, there was a
right-beating spontaneous nystagmus of 3 °/s. The cause of the weak
spontaneous nystagmus on center gaze and in the supine position could
have been from the residual effects of prior testing maneuvers, the
presence of pseudo-spontaneous nystagmus, or be within normal
limits.{[}8-12{]} In the chin-down (bow position), there was a
right-beating sustained horizontal nystagmus (maximum slow-phase
velocity {[}SPV{]} of 7°/s). In the right Dix-Hallpike maneuver, no
nystagmus occurred. In the left Dix-Hallpike maneuver, there was a
right-beating horizontal nystagmus that was sustained (maximum SPV of 12
°/s). In the SRT, in the right ear-down position, there was a
crescendo-decrescendo right-beating nystagmus, lasting around 40 seconds
(maximum SPV of 12 °/s), as shown in Supplemental Video 1. In the left
ear-down position, there was a briefer decrescendo left-beating
nystagmus, lasting around 15 seconds (maximum SPV of 13°/s), as shown in
Supplemental Video 2. Since the chin-down position elicited
right-beating nystagmus, a diagnosis of \emph{right-sided hcBPPV} , with
\emph{geotropic} horizontal positional nystagmus was thought most
likely.{[}13{]}

In summary, the diagnosis by the emergency department clinicians
was\emph{left-sided BPPV} , presumably of the \emph{posterior canal} ,
for which they applied an ``appropriate''\emph{left-sided Epley}
maneuver. However, after the emergency department visit, the expert
review of the research VOG recordings found the overall picture was most
consistent with \emph{hcBPPV, geotropic variant, on the right side} .
The BPPV was likely\emph{right-sided} , based on the intense
right-beating nystagmus induced in the bow position.{[}13{]} Thus, in
the emergency department, the patient was diagnosed with the incorrect
side, the incorrect canal, and applied the incorrect treatment.
Nevertheless, the patient's symptoms and nystagmus resolved. Despite
several diagnostic and treatment errors in this patient with BPPV, we
wondered why the treatment worked, so we performed simulations to test
the hypothesis.

\textbf{Simulation Findings}

Simulations of possible treatment maneuvers for this patient were
created using a 3D model of the inner ear. This generic model (i.e., not
specific to the patient described in this case report) was based on
reconstructed images from high-resolution computed tomography of the
temporal bone (Digital Imaging and Communication in Medicine files).
This methodology has been described by Bhandari and colleagues.{[}14{]}
The orientation of the canals and the angles between the canals were as
previously reported.{[}15{]} The simulations allowed the placement of
the debris in any of the canals and at variable positions within the
canal. Given the uncertainty of whether the emergency department
physician correctly performed the Epley maneuver on this patient, we
simulated both possibilities: a correctly performed Epley maneuver and
an extended Epley maneuver.

Simulation 1 (Supplemental Video 3) shows the effect of a correctly
performed left ear Epley maneuver on a right ear hcBPPV. When the
subject is brought to the head-hanging position in the second step of
the maneuver, the debris moves through but not out of the horizontal
canal away from the ampulla, which could generate a left-beating
horizontal nystagmus. When the subject's head is turned by
90\textsuperscript{o} to the right side, the debris moves back through
the horizontal canal toward the ampulla and could generate a
right-beating horizontal nystagmus. Thus, performing the correct Epley
maneuver with a hcBPPV of the opposite side causes free-floating
otoconia to move within but not out of the offending horizontal SCC. The
patient's hcBPPV symptoms would likely not be resolved.

Simulation 2 (Supplemental Video 4) showed the effect of a left Epley
maneuver when the head is turned by 15\textsuperscript{o} more than the
usual 45\textsuperscript{o} in the second step of the maneuver, in a
right hcBPPV. In this case, when the subject is brought to the
head-hanging position, the contralateral horizontal SCC becomes nearly
vertical, allowing the debris to move not only within but also out of
the right horizontal SCC under the effect of gravity, thus successfully
treating a hcBPPV on the contralateral side before the patient is rolled
over. Note this simulation also applies to the second stage of an
extended Dix-Hallpike maneuver.

\textbf{Discussion:}

In sum, despite diagnosing the wrong side, the wrong canal, and applying
the wrong treatment maneuver, the emergency department clinicians cured
the patient's BPPV.

Among patients experiencing acute vertigo symptoms, hcBPPV is often
underdiagnosed in favor of pcBBPV.{[}2, 3{]} While the Dix-Hallpike Test
(DHT) is the preferred test to diagnose pcBPPV, other diagnostic tests,
such as the supine roll test (SRT), are often needed so that a diagnosis
of hcBPPV is not missed.{[}4-7{]} Our simulations emphasize the
importance of performing these diagnostic tests using standardized
maneuvers in a specific sequence. We have shown that the Dix-Hallpike
maneuver can cause debris to move within the horizontal SCC, producing
symptoms and potentially leading to a misdiagnosis of pcBPPV instead of
hcBPPV. However, if the SRT is performed first, there will be little to
no movement of particles within the posterior SCC, and even if there was
movement in the posterior SCC, it would produce a vertical / torsional
nystagmus pointing to the posterior SCC being the affected canal. This
is consistent with the findings of Bhandari et al. (2022) and Li and
Yang (2023), who showed that the sequence of performing the SRT steps
can alter the position of otoconial debris within the canal as well as
the resultant nystagmus patterns, which could lead to ambiguity of the
type and side of a hcBPPV.{[}16, 17{]} Thus, following a protocol in
which the SRT is performed first in patients with the triggered
(positional) episodic vestibular syndrome should provide an optimal
window to observe Ewald's 1\textsuperscript{st} law in action (``the
plane of nystagmus parallels the anatomic plane of the semicircular
canal that generated it''), with pcBPPV producing vertical / torsional
nystagmus and hcBPPV producing horizontal nystagmus.{[}18{]}

These issues raise the question of whether the approach to BPPV should
change to clinicians first performing the SRT to optimally assess for
hcBPPV. If the SRT is negative, clinicians should then perform the DHT
to optimally assess for pcBPPV. Alternatively, clinicians could be
trained to start with the DHT but, more specifically, observe nystagmus
patterns of pcBPPV or hcBPPV since the DHT triggers nearly all pcBPPV
and at least half of hcBPPV.{[}19{]} Lastly, this case also raises the
possibility that the approach to BPPV could be simplified for frontline
doctors since it is possible that single maneuvers can treat multiple
variants. Future clinical trials about training physicians in the
approach to BPPV could better address this issue.

In our patient, in view of the inaccurate classification of BPPV in the
emergency department, the ``curative'' effect of the Epley treatment was
initially surprising. The Epley maneuver, if correctly performed, should
be specific for resolving pcBPPV.{[}6{]} There have been anecdotal
reports, however, that hcBPPV may resolve with the Epley maneuver, but
it is unclear how the Epley maneuver was applied in those cases. Our
simulation of a left Epley maneuver with extended (i.e., head turned too
far) angulation of the head successfully resolving a right hcBPPV is
like a proposed treatment maneuver for hcBPPV that involves starting in
the supine position, turning the head towards the healthy side (left in
our patient's case) for 45°, then another 45° towards the healthy side,
and then sitting up.{[}20{]} The optimal repositioning maneuvers for
hcBPPV and pcBPPV are well-documented in prior studies and should be
encouraged in clinical practice.

Our patient illustrates that a successful outcome does not always depend
on the correct classification of BPPV and correct treatment. While the
adage, ``It's better to be lucky than good,'' may have been at play in
this case, benefitting this patient, our results should not be
interpreted to suggest that clinicians need not strictly follow testing
or treatment protocols. Rather, our results suggest the
\emph{opposite}-- that placing the head in the correct position for a
canal-plane-specific BPPV is critical to interpreting nystagmus and
accurate clinical diagnosis.

Limitations of our study include the lack of precise knowledge of how
the testing and treatment maneuvers were performed by the clinical staff
in the emergency department, the lack of precise knowledge of the
nystagmus patterns observed by the treating clinician, the
unavailability of the patient for evaluation by our research team after
treatment, and the lack of follow-up data on the long-term response of
the patient. It remains possible that the patient initially had pcBPPV,
and the treating clinician's repositioning moved the particles out of
the posterior canal and into the horizontal canal -- known as `canal
switch.' Furthermore, since there was only a small difference in the
intensity of the horizontal nystagmus elicited in the two ear-down
positions during the SRT, the localization of the offending labyrinth by
the research team was primarily based on the response to the bow test.
The lack of significant asymmetry between the two sides during the SRT
could be related to the relatively low peak slow phase velocity of
nystagmus induced in the SRT due to the relatively low velocity of the
movements of the head to the ear down position.{[}21, 22{]} In this
case, the head movements were not fast enough for Ewald's
2\textsuperscript{nd} law -- excitation produces a stronger response
than inhibition -- to take effect. The asymmetry between right and left
ear-down positions may be better brought out by moving the head quickly
to the ear-down positions. Additionally, our simulations assume an
average anatomical orientation of the canals, the membranous labyrinth,
and the cupula.{[}15{]} The variability of the orientation of the canals
in the head, the membranous labyrinth within them, and the cupula among
individual subjects; the presumed differences among subjects in the
location and constitution (otoconia and sluffed otolith membrane) of the
debris within the SCCs; and the speed at which the head is brought to a
new position in the diagnostic and treatment maneuvers, can all
contribute to the uncertainty of the classification of the canal subtype
of BPPV and of the effects of different treatment maneuvers.{[}1,
21-24{]} Despite these limitations, our analysis and simulations are
most compatible with diagnosing a right-sided hcBPPV, treated with an
extended left Epley maneuver for a misdiagnosed left-sided pcBPPV.

\textbf{Conclusion:}

This case and our simulations emphasize that maneuvers that are designed
to induce the movement of displaced otoconia in one specific canal can
trigger or treat BPPV in other canals. Our study also raises the
question of whether the diagnosis and treatment of BPPV could be
improved if clinicians perform the SRT first and then if no nystagmus is
elicited, perform the Dix-Hallpike maneuver. Finally, we recommend that
clinicians place the head in the correct position for all diagnostic and
therapeutic maneuvers, carefully observe and report the direction of the
nystagmus, and always consider the location of otoconia within the
canals and the possibility of other canals being involved when rendering
a canal-specific diagnosis and treatment for BPPV.

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