Northeast Florida Medicine
Vol. 66, No. 1 2015
51
Otolaryngology
quantify hearing changes, but do not provide information
regarding symptoms of autophony and pseudoconductive
hyperacusis. Standard vestibular tests primarily measure
horizontal semicircular canal function, which is uninvolved
by the pathology of the superior semicircular canal. Advanced
vestibular testing, such as cVEMP (cervical vestibular evoked
myogenic potential), oVEMP (ocular vestibular evoked
myogenic potential), and rotary chair testing (on axis and
eccentric axis) measure otolith (saccule and utricle) function,
which also are uninvolved by the pathology of the dehis-
cent superior semicircular canal. The only accurate way to
measure superior canal function is with scleral search coils,
a research tool which is not widely available. A relatively
new system, vHIT (vertical head impulse test) can measure
superior semicircular canal function, but has been available
commercially for only about one year, and lacks accepted
norms and standardization.
18,19
Therefore, the most realistic metrics for outcome are
standardized, validated patient survey questionnaires (DHI
– dizziness handicap inventory and/or ABC Scale – activ-
ities specific balance confidence scale). One well accepted
objective metric for gait and balance is the FGA – functional
gait assessment – a standardized, age normed, and validated
test of gait and balance. The FGA is a 10 item assessment,
typically administered by a physical therapist, and includes
challenges such as walking while turning the head side to
side and up and down, walking backwards, stepping over
obstacles, pivot and turn, etc.
Since July 2009, the cartilage cap technique has been
exclusively used for the surgical management of a dehiscent
superior semicircular canal.
9,20
Prior to July 2009, themiddle
fossa and transmastoid plugging techniques were used, with
variable success. Preliminary data for more than 90 patients
who have undergone the cartilage cap surgical procedure are
quite encouraging. The above metrics, and more are used
to assess outcomes.
Summary
A dehiscent superior semicircular canal is a pathological
condition that manifests a spectrum of symptoms from
nuisance autophony to debilitating dizziness and dis-
equilibrium. Most patients require only reassurance and
conservative treatment once the diagnosis is made. Patients
with debilitating vestibular symptoms are candidates for
surgical management. Surgical management is evolving,
with cartilage cap resurfacing providing a less involved, less
morbid procedure with much shorter hospitalization and
comparable outcomes to plugging.
v
Bibliography
1. Ewald JR.
Physiologische Untersuchungen uber das Endor-
gan des Nervus Octavus.
Wiesgaden, Germany: Verlag Von
J. F. Bergmann; 1892.
2. Tullio P.
Das Ohr und die Entstehung der Sprache und
Schrift:
Urban und Schwarzenberg; 1929.
3. Hennebert C. Reactions vestibulaires dans les labyrin-
thites heredo-syphili-tiques. Archives internationals de
laryngology, otologie-rhinologie, bro-cho-oesophagosco-
pie. 1909;28:93-6.
4. Minor LB, Solomon D, Zinreich JS, et al. Sound- and/
or pressure-induced vertigo due to bone dehiscence of the
superior semicircular canal.
Arch Otolaryngol Head Neck
Surg.
1998;124(3):249-58.
5. Carey JP, Minor LB, Nager GT. Dehiscence or thinning
of bone overlying the superior semicircular canal in a
temporal bone survey.
Arch Otolaryngol Head Neck Surg.
2000;126(2):137-47.
6. Tsunoda A, Terasaki O. Dehiscence of the bony roof
of the superior semicircular canal in the middle cranial
fossa.
J Laryngol Otol.
2002;116(7):514-8.
7. Agrawal SK, Parnes LS. Transmastoid superior semicircu-
lar canal occlusion.
Otol Neurotol.
2008;29(3):363-7.
8. Crovetto M, Areitio E, Elexpuru J, et al. Transmastoid
approach for resurfacing of Superior Semicircular Canal
dehiscence.
Auris Nasus Larynx.
2008;35(2):247-9.
9. Lundy L, Zapala D, Moushey J. Cartilage cap occlusion
technique for dehiscent superior semicircular canals.
Otol
Neurotol.
2011;32(8):1281-4.
10. Mikulec AA, Poe DS, McKenna MJ. Operative manage-
ment of superior semicircular canal dehiscence.
Laryngo-
scope.
2005;115(3):501-7.
11. Phillips DJ, Souter MA, Vitkovic J, et al. Diagnosis and
outcomes of middle cranial fossa repair for patients with
superior semicircular canal dehiscence syndrome.
J Clin
Neurosci.
2010;17(3):339-41.
12. Agrawal Y, Migliaccio AA, Minor LB, et al. Vestibular
hypofunction in the initial postoperative period after sur-
gical treatment of superior semicircular canal dehiscence.
Otol Neurotol.
2009;30(4):502-6.
13. Carey JP, Migliaccio AA, Minor LB. Semicircular canal
function before and after surgery for superior canal dehis-
cence.
Otol Neurotol.
2007;28(3):356-64.
14. Niesten ME, McKenna MJ, Grolman W, et al. Clin-
ical factors associated with prolonged recovery after
superior canal dehiscence surgery.
Otol Neurotol.
2012;33(5):824-31.
15. Rabbitt RD, Boyle R, Highstein SM. Physiology of the
semicircular canals after surgical plugging.
Ann N Y Acad
Sci.
2001;942:274-86.
