View source for Medicine:Enlarged vestibular aqueduct

{{short description|Human disease}}
{{Infobox medical condition (new)
| name          = Enlarged vestibular aqueduct
| synonyms      = '''Enlarged vestibular aqueduct''', '''Dilated vestibular aqueduct''' or '''Widened vestibular aqueduct'''
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| caption       = Interior of right osseous labyrinth
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'''Large vestibular aqueduct''' is a structural deformity of the inner ear. Enlargement of this duct is one of the most common inner ear deformities and is commonly associated with [[Medicine:Hearing loss|hearing loss]] during childhood.<ref name=PdsMutation>{{citation |title=Non-syndromic hearing loss associated with enlarged vestibular aqueduct is caused by PDS mutations |author1=S. Usami |author2=Satoko Abe |author3=Mike D. Weston |author4=Hideichi Shinkawa |author5=Guy Van Camp |author6=William J. Kimberling |volume= 104|issue=2 |year= 1999 |doi=10.1007/s004390050933 |journal=Human Genetics |pages=188–192 |pmid=10190331|s2cid=3116063 }}</ref> The term was first discovered in 1791 by Mondini when he was completing a temporal bone dissection. It was then defined by Valvassori and Clemis as a vestibular aqueduct that is greater than or equal to 2.0 mm at the operculum and/or greater than or equal to 1.0 mm at the midpoint.<ref>{{cite journal |last1=Yang |first1=Christina |title=Vestibular Pathology in Children with enlarged vestibular aqueduct |journal=The Laryngoscope |date=2016 |volume=126 |issue=10 |pages=2344–50 |doi=10.1002/lary.25890|pmid=26864825 }}</ref> Some use the term '''enlarged vestibular aqueduct syndrome''', but this is felt by others to be erroneous as it is a clinical finding which can occur in several syndromes.{{Citation needed|date=November 2022}}

==Symptoms==
Although large vestibular aqueducts are a congenital condition, hearing loss may not be present from birth. Age of diagnosis ranges from infancy to adulthood, and symptoms include fluctuating and sometimes progressive sensorineural hearing loss and disequilibrium. It is possible that a small portion of those with large vestibular aqueducts will not exhibit auditory symptoms such as hearing loss. While this is uncommon, hearing loss can progress later in life, especially after [[Medicine:Head injury|head trauma]].<ref>{{citation |title=Enlarged Vestibular Aqueduct Syndrome in the Pediatric Population |author1=Madden, Colm |author2=Halsted, Mark |author3=Benton, Corning |author4=Greinwald, John |author5=Choo, Daniel |date=July 2003 |journal=Otology & Neurotology|volume=24 |issue=4 |pages=625–632 |doi=10.1097/00129492-200307000-00016|pmid=12851556 |s2cid=44980735 }}</ref> Hearing loss can be unilateral or bilateral and can be sensorineural, conductive, or mixed. Vestibular symptoms, such as [[Medicine:Vertigo|vertigo]] and imbalance, occur in adult patients 45% of the time. <ref>{{cite journal |last1=Grimmer |first1=J |title=Vestibular symptoms in children with enlarged vestibular aqueduct anomaly |journal= International Journal of Pediatric Otorhinolaryngology|date=2007 |volume=71 |issue=2 |pages=275–82 |doi=10.1016/j.ijporl.2006.10.010|pmid=17113162 }}</ref>

==Pathology==
[[Image:Gray923.png|right|thumb|The cochlea and vestibule, viewed from above. (Vestibular aqueduct labeled at bottom right.)]]

The vestibular aqueduct acts as a canal between the inner ear and the cranial cavity. Running through it is a tube called the endolymphatic duct, which normally carries a fluid called [[Biology:Endolymph|endolymph]] from the inner ear to the endolymphatic sac in the cranial cavity.  When the endolymphatic duct and sac are larger than normal, as is the case in large vestibular aqueduct syndrome, endolymph is allowed to travel back from the endolymphatic sac into the inner ear.  This often results in fluctuations in hearing levels.  Enlarged vestibular aqueducts are caused by mutations in gene SLC26A4, which is also associated with [[Medicine:Pendred syndrome|Pendred syndrome]] and non-syndromic recessive deafness. Enlarged vestibular aqueducts often occur with other inner ear development problems, such as [[Medicine:Cochlea|cochlea]]r deformities. Enlarged vestibular aqueducts are part of the classic  Mondini deformity. Enlarged vestibular aqueducts with enlarged endolymphatic sacs occur in Pendred syndrome, which is caused by a defect on chromosome 7q31.<ref name=PdsMutation /> Enlarged vestibular aqueducts can also occur in [[Medicine:Branchio-oto-renal syndrome|branchio-oto-renal syndrome]], [[Medicine:CHARGE syndrome|CHARGE syndrome]] and [[Medicine:Renal tubular acidosis|renal tubular acidosis]].

Enlarged vestibular aqueducts can be bilateral or unilateral.

Hearing loss caused by large vestibular aqueduct syndrome is not inevitable, although people with the syndrome are at a much higher risk of developing hearing loss than the general population. Hearing loss is very likely.

==Diagnosis==

Enlarged vestibular aqueducts are commonly picked up after newborn hearing screen when a child is identified as having a hearing loss. The hearing loss is commonly mixed and can be of any degree when first identified. The conductive component is due to a third window effect caused by the widened vestibular aqueduct. 
During an audiologic assessment, an air-bone gap in the low frequencies can occur due to the enlarged vestibular aqueduct acting as a third mobile window. Hearing loss in the contralateral ear to the enlarged vestibular aqueduct can also occur due to the chemical composition on both sides.<ref>{{cite journal |last1=Greinwald |first1=J |title=Significance of unilateral enlarged vestibular aqueduct |journal=The Laryngoscope |date=2013 |volume=123 |issue=6 |pages=1537–46 |doi=10.1002/lary.23889 |pmid=23401162 }}</ref> 
Torticollis has also been found to be an indicator of an enlarged vestibular aqueduct in children.<ref>{{cite journal |last1=Brodsky |first1=J |title=Torticollis in children with enlarged vestibular aqueducts |journal=  International Journal of Pediatric Otorhinolaryngology|date=2020 |volume=131 |pages=109862 |doi=10.1016/j.ijporl.2020.109862|pmid=31927148 }}</ref>
Identification of the enlarged vestibular aqueduct in a child is usually by [[Physics:Magnetic resonance imaging|MRI scan]] which identifies the fluid within the endolymphatic duct and sac. [[CT scan]] may be needed to see the vestibular aqueduct clearly. In adults, CT scan may be the first investigation.
In order to diagnose the cause of the enlarged vestibular aqueduct, the physician will need a detailed family history, full examination to include vestibular examination and, if a bilateral finding, molecular [[Medicine:Genetic testing|genetic testing]] as appropriate. With unilateral enlarged vestibular aqueducts, molecular genetic testing is currently not recommended.

==Management==
 There is no treatment to correct an enlarged vestibular aqueduct. Any hearing loss will need management with amplification and support in education and at work. If the hearing loss becomes severe to profound, [[Cochlear implant|cochlear implants]] can be of significant value. Vestibular disturbance is usually short-lived and associated with head trauma, but significant vestibular hypofunction may require rehabilitation.

People with enlarged vestibular aqueducts are advised to avoid head trauma where possible. This usually means avoiding contact sports such as football, boxing, rugby, horse riding, trampolining and other sports where head injury may occur. Some have symptoms when flying and should limit these activities if affected.

==References==
{{reflist}}

== External links ==
{{Medical resources
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| OMIM            = 600791
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| MeshID          = C566366
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{{Transcription factor/coregulator deficiencies}}

[[Category:Syndromes affecting hearing]]

{{Sourceattribution|Enlarged vestibular aqueduct}}