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Enlargement of the vestibular aqueduct
Case Studies Am J Otolaryngol 5:411,--414, 1984
Enlargement of the Vestibular Aqueduct JAMES H. HILL, M.D., ALAN J. FREINT, M.D., AND MAHMOOD F. MAFEE, M.D.
Enlarged vestibular aqueduct, a recently identified anomaly, is typified by an enlarged vestibule, dilation of the ampullated portions of the horizontal and superior semicircular canals, an abnormal cochlea, and hearing loss. In the case described a 16-year-old boy had congenital hearing loss, episodic vertigo, and abnormal vestibular function testing. Tomograms and CT scans confirmed the diagnosis of bilaterally enlarged vestibular aqueducts. The vertiginous episodes decreased in frequency and severity with a no-saltadded diet. The authors conclude that the enlarged vestibular aqueduct is associated not only with other structural inner ear abnormalities and hearing loss, but also with abnormal vestibular function.
ital hearing loss and episodic vertigo. The patient had first sought medical therapy at the age of 3 years for hearing loss and delayed onset of speech. The parents related that he had had a vocabulary of only three words by the age of 4 years. An audiogram revealed a mixed severe-toprofound hearing loss, greater on the left Side than on the right. The patient underwent bilateral myringotomies with insertion of ventilation tubes; fluid was present in both middle ear cavities at that time, There was an average 20-dB hearing improvement postoperatively in the right ear only. The patient was fitted with a hearing aid for the right ear. Several times during
Identification of the enlarged vestibular aqueduct was described only recently by'Valvassort and Clemis? Involvement was bilateral twice as often as unilateral and in 60 per cent of cases was associated with radiographically identifiable inner ear anomalies. These anomalies included enlargement of the vestibule, dilation of the ampullated portions of the horizontal and superior semicircular canals, and cochlear abnormalities. 2 Most cases of enlarged vestibular aqueduct were associated with nonprogressive hearing loss (mixed or sensorineural), which was of a congenital or early acquired type. Vestibular complaints were few and were considered inconsequential. Further documentation of associated clinical findings is necessary to establish the importance of the enlarged vestibular aqueduct in the development and subsequent functioning of the audiovestibular system. The present case affords excellent clinical documentation with detailed audiovestibular testing.
Frequency ~n Hz
125 -10
250
500
1000
2000
4000
8000
0 10 20 30
REPORT OF A CASE
40 50
A 16-year-old boy was referred to the Illinois Eye and Ear Infirmary for evaluation of congen-
60 70 8O
Received July 18, 1984. from the Departments of Otolaryngology-Head and Neck Surgery (Drs. Hill and Freint) and Radiology (Dr. Mafee), University of Illinois College of Med!¢ine at Chicago, Illinois Eye and Ear Infirmary, and the West Side Veterans Administration Medical Center, Chicago, Illinois. Accepted for publication August 9, 1984, : Address correspondence reprint requests to Dr. Hill: Illinois Eye and Ear Infirmary, 1855 West Taylor Street, Chicago, IL 60612.
90 100 110
.
:c\
.
.
.
x,, ? "
I
I I]
1
Figure 1. Audiogram of a 16-year-old boy with enlarged vestibular aqueducts bilaterally. There were no responses by bony conduction at any frequency and no responses by air conduction above 1,000 Hz.
411
VESTIBULARAQUEDUCT ENLARGEMENT
1,0mm/sec I°RIGHT
I°LEFT
the e n s u i n g years v e n t i l a t i n g tubes w e r e reinserted, with similar findings and minimal he~i:ng i m p r o v e m e n t . At t h e age of 14 y e w s , t h e patient c o m p l a i n e d m the left side. mg ensued. The to t h r e e or four Tintervals. He had ; left, a n d he h a d a t e n d e n c y to fall f o r w a r d d u r i n g e a c h attack, R~p~d position changes d u r i n g the attack heighte n e d the vertigo. He was c o m p l e t e l y free of dizziness b e t w e e n attacks. He described a contin-
Figure 2 (tap). Electronystagmogram showing first-degree gaze nystagmus bilaterally on eye deviation 30 ° from the midline. No spontaneous nystagmus was present.
Figure
3
(bottom).
Saccadic eye tracking on electronystagmogram.
u o u s " s t a t i c " noise in his ears that s h o w e d no relation to t h e d i z z y spells. T h e p a t i e n t ' s ear fullness was s i m i l a r l y always p r e s e n t w i t h o u t variation. A fistula test was negative. T h e p a t i e n t e x p e r i e n c e d s o m e r e l i e f of s y m p t o m s w i t h a t r e a t m e n t r e g i m e n that i n c l u d e d a l o w - s a l t diet a n d m e c l i z i n e . No history of e x p o s u r e to ototoxic drugs c o u l d be elicited. T h e c h i l d h a d contracted rubella well after the h e a r i n g loss h a d b e c o m e evident. At the age of 10 years, h e was struck by a n a u t o m o b i l e w h i l e r i d i n g his b i c y c l e , but there was no loss of c o n s c i o u s n e s s . N o app a r e n t a d d i t i o n a l change in h e a r i n g was attrib-
Lateral polytomogram of the left temporal bone showing a markedly enlarged vestibular aqueduct (arrows), the common crus (open arrow), and jugular fosse (JF]. Figure 4.
American JournQl of
Otola ryngo~ogy
HILL ET AL.
Figure 5. Top, Axial computed tomographic scan of the left temporal bone showing enlarged vestibular aqueduct (arrows}, the internal auditory canal {IAC), and the vestibule (V). Bottom, Axial scan of the right temporal bone showing the enlarged vestibular aqueduct (arrows), the internal auditory canal (IAC), and the vestibule (V).
utable to the trauma. The child had had no surgery, and there were no other illnesses or trauma. Physical examination revealed an apparently healthy, c o m f o r t a b l e patient with a longstanding hearing loss. The auricles and ear canals were normal bilaterally, Ventilating tubes were present bilaterally with areas of tympanosclerosis on the t y m p a n i c membrane. An audio-
gram d o c u m e n t e d bilateral severe-to-profound sensorineural hearing loss, worse on the left (Fig. 1). There were no responses to bone conduction at any frequency and no responses to air conduction above 1,000 Hz. T y m p a n o g r a m s indicated bilateral patent v e n t i l a t i n g tubes. Acoustic reflexes were absent. F u r t h e r audiometric testing was not possible due to the severity of the hearing loss.
Volume 5 Number 6 November 1984
413
VESTIBULAR AQUEDUCT ENLARCEMENT
Vestibular function tests revealed bilateral first-degree gaze nystagmus at 30 ° eye deviation from the midline (Fig. 2), saccadic eye tracking (Fig. 3), and no spontaneous nystagmus. There were no responses to 20°C air caloric testing. Water calorics were not possible due to the presence of ventilating tubes. Results of pastural studies were normal. Inner ear tomograms showed large, symmetric internal auditory canals. The vestibular aqueducts were enlarged bilaterally. The left side was more prominent, measuring twice (3.0 mm) the normal upper limit in anteroposterior diameter (Fig. 4). High-resolution computed tomographic scans were obtained at l-ram intervals, They confirmed the enlargement of the vestibular aqueducts, greater on the left side (Fig. 5). The vestibules were also enlarged bilaterally, but no other inner ear anomalies were present. The temporal bones were otherwise normal. No abnormalities were present in the cerebellopontine angle. The patient was maintained on a no-addedsalt diet and reported a marked decrease in the frequency and severity of vertiginous episodes,
DISCUSSION The vestibular aqueduct is a bony canal in the otic capsule; it contains the endolymphatic duct, which originates from the ubicle and saccule in the vestibule and terminates at an orifice on the posterior surface of the petrous pyramid. ~ In the last 25 years, multiple gross and histologic studies of the vestibular aqueduct have confirmed the variability in size and shape of this structure. 4-6 Many m e a s u r e m e n t s have been taken, including length, diameter of internal and external apertures, width, height, area, and angulation. The range of values determined varies, depending on the technique of measurement and the method of tissue preparation. Radiologically, measurements of the vestibular aqueduct are obtained halfway between the external aperture
American Journal of OtoloryngoJogy 414
and the c o m m o n crus. An aqueduct is considered enlarged whenever its anteroposterior diameter is 1.5 mm or greater. 2 Valvassori and Clemis 1 reported 50 cases of enlarged vestibular aqueducts. In 60 per cent of the cases other r a d i o g r a p h i c a l l y identifiable anomalies of the inner ear were present. These investigators concluded that the enlarged vestibular aqueduct represents an arrested phase of inner ear development. Congenital or early acquired hearing loss was frequently involved. A family history of hearing loss was not an important factor in their study, Finally, vestibular complaints were of little consequence. The present case report is important for several reasons. Early d o c u m e n t a t i o n of mixed, nonprogressive, congenital hearing loss reaffirms the finding that the enlarged vestibular aqu e d u c t is associated with audiometric abnormalities. Vertigo, which was previously reported to be mild or inconsequential, may be of greater i m p o r t a n c e than suspected. Our case affords documentation of vestibular testing abnormalities in association with episodically disabling vertigo. We conclude that the enlarged vestibular aqueduct comprises abnormalities not only in the structure of the inner ear, but also in the physiology of the auditory and vestibular systems.
References 1. Valvassori GE, Clemis ]D: The large vestibular aqueduct syndrome. Laryngoscope 88: 723-728, 1978 2, Valvassori GE: The vestibular aqueduct and associated anomalies of the inner ear, Otolaryngol Clin North Am 16:95-101, 1983 3. Anson BJ, Donaldson ]A: Surgical Anatomy of the Temporal Bone and Ear, ed 3. Philadelphia, WB Saunders Co, 1961, pp 64; 396 4, AnsanBJ, Donaldson]A, Warpeha RL, etah A critical appraisal of the anatomyof the perilymphatic system in man, Laryngoscope 74:945-966, 1964 5. Ogura Y, Clemis JD: A study o[ the gross anatomy of the human vestibular aqueduct, Ann Otol Rhinol Laryngol 80:813-825, 1971 6. Kodama A, Sando h Dimensional anatomy of the vestibular aqueduct and the endolymphatic sac (rugose portion) in human temporal banes, Ann Otol Rhinol Laryngol 91 (suppl 96]:13-20, 1982
Enlargement of the Vestibular Aqueduct JAMES H. HILL, M.D., ALAN J. FREINT, M.D., AND MAHMOOD F. MAFEE, M.D.
Enlarged vestibular aqueduct, a recently identified anomaly, is typified by an enlarged vestibule, dilation of the ampullated portions of the horizontal and superior semicircular canals, an abnormal cochlea, and hearing loss. In the case described a 16-year-old boy had congenital hearing loss, episodic vertigo, and abnormal vestibular function testing. Tomograms and CT scans confirmed the diagnosis of bilaterally enlarged vestibular aqueducts. The vertiginous episodes decreased in frequency and severity with a no-saltadded diet. The authors conclude that the enlarged vestibular aqueduct is associated not only with other structural inner ear abnormalities and hearing loss, but also with abnormal vestibular function.
ital hearing loss and episodic vertigo. The patient had first sought medical therapy at the age of 3 years for hearing loss and delayed onset of speech. The parents related that he had had a vocabulary of only three words by the age of 4 years. An audiogram revealed a mixed severe-toprofound hearing loss, greater on the left Side than on the right. The patient underwent bilateral myringotomies with insertion of ventilation tubes; fluid was present in both middle ear cavities at that time, There was an average 20-dB hearing improvement postoperatively in the right ear only. The patient was fitted with a hearing aid for the right ear. Several times during
Identification of the enlarged vestibular aqueduct was described only recently by'Valvassort and Clemis? Involvement was bilateral twice as often as unilateral and in 60 per cent of cases was associated with radiographically identifiable inner ear anomalies. These anomalies included enlargement of the vestibule, dilation of the ampullated portions of the horizontal and superior semicircular canals, and cochlear abnormalities. 2 Most cases of enlarged vestibular aqueduct were associated with nonprogressive hearing loss (mixed or sensorineural), which was of a congenital or early acquired type. Vestibular complaints were few and were considered inconsequential. Further documentation of associated clinical findings is necessary to establish the importance of the enlarged vestibular aqueduct in the development and subsequent functioning of the audiovestibular system. The present case affords excellent clinical documentation with detailed audiovestibular testing.
Frequency ~n Hz
125 -10
250
500
1000
2000
4000
8000
0 10 20 30
REPORT OF A CASE
40 50
A 16-year-old boy was referred to the Illinois Eye and Ear Infirmary for evaluation of congen-
60 70 8O
Received July 18, 1984. from the Departments of Otolaryngology-Head and Neck Surgery (Drs. Hill and Freint) and Radiology (Dr. Mafee), University of Illinois College of Med!¢ine at Chicago, Illinois Eye and Ear Infirmary, and the West Side Veterans Administration Medical Center, Chicago, Illinois. Accepted for publication August 9, 1984, : Address correspondence reprint requests to Dr. Hill: Illinois Eye and Ear Infirmary, 1855 West Taylor Street, Chicago, IL 60612.
90 100 110
.
:c\
.
.
.
x,, ? "
I
I I]
1
Figure 1. Audiogram of a 16-year-old boy with enlarged vestibular aqueducts bilaterally. There were no responses by bony conduction at any frequency and no responses by air conduction above 1,000 Hz.
411
VESTIBULARAQUEDUCT ENLARGEMENT
1,0mm/sec I°RIGHT
I°LEFT
the e n s u i n g years v e n t i l a t i n g tubes w e r e reinserted, with similar findings and minimal he~i:ng i m p r o v e m e n t . At t h e age of 14 y e w s , t h e patient c o m p l a i n e d m the left side. mg ensued. The to t h r e e or four Tintervals. He had ; left, a n d he h a d a t e n d e n c y to fall f o r w a r d d u r i n g e a c h attack, R~p~d position changes d u r i n g the attack heighte n e d the vertigo. He was c o m p l e t e l y free of dizziness b e t w e e n attacks. He described a contin-
Figure 2 (tap). Electronystagmogram showing first-degree gaze nystagmus bilaterally on eye deviation 30 ° from the midline. No spontaneous nystagmus was present.
Figure
3
(bottom).
Saccadic eye tracking on electronystagmogram.
u o u s " s t a t i c " noise in his ears that s h o w e d no relation to t h e d i z z y spells. T h e p a t i e n t ' s ear fullness was s i m i l a r l y always p r e s e n t w i t h o u t variation. A fistula test was negative. T h e p a t i e n t e x p e r i e n c e d s o m e r e l i e f of s y m p t o m s w i t h a t r e a t m e n t r e g i m e n that i n c l u d e d a l o w - s a l t diet a n d m e c l i z i n e . No history of e x p o s u r e to ototoxic drugs c o u l d be elicited. T h e c h i l d h a d contracted rubella well after the h e a r i n g loss h a d b e c o m e evident. At the age of 10 years, h e was struck by a n a u t o m o b i l e w h i l e r i d i n g his b i c y c l e , but there was no loss of c o n s c i o u s n e s s . N o app a r e n t a d d i t i o n a l change in h e a r i n g was attrib-
Lateral polytomogram of the left temporal bone showing a markedly enlarged vestibular aqueduct (arrows), the common crus (open arrow), and jugular fosse (JF]. Figure 4.
American JournQl of
Otola ryngo~ogy
HILL ET AL.
Figure 5. Top, Axial computed tomographic scan of the left temporal bone showing enlarged vestibular aqueduct (arrows}, the internal auditory canal {IAC), and the vestibule (V). Bottom, Axial scan of the right temporal bone showing the enlarged vestibular aqueduct (arrows), the internal auditory canal (IAC), and the vestibule (V).
utable to the trauma. The child had had no surgery, and there were no other illnesses or trauma. Physical examination revealed an apparently healthy, c o m f o r t a b l e patient with a longstanding hearing loss. The auricles and ear canals were normal bilaterally, Ventilating tubes were present bilaterally with areas of tympanosclerosis on the t y m p a n i c membrane. An audio-
gram d o c u m e n t e d bilateral severe-to-profound sensorineural hearing loss, worse on the left (Fig. 1). There were no responses to bone conduction at any frequency and no responses to air conduction above 1,000 Hz. T y m p a n o g r a m s indicated bilateral patent v e n t i l a t i n g tubes. Acoustic reflexes were absent. F u r t h e r audiometric testing was not possible due to the severity of the hearing loss.
Volume 5 Number 6 November 1984
413
VESTIBULAR AQUEDUCT ENLARCEMENT
Vestibular function tests revealed bilateral first-degree gaze nystagmus at 30 ° eye deviation from the midline (Fig. 2), saccadic eye tracking (Fig. 3), and no spontaneous nystagmus. There were no responses to 20°C air caloric testing. Water calorics were not possible due to the presence of ventilating tubes. Results of pastural studies were normal. Inner ear tomograms showed large, symmetric internal auditory canals. The vestibular aqueducts were enlarged bilaterally. The left side was more prominent, measuring twice (3.0 mm) the normal upper limit in anteroposterior diameter (Fig. 4). High-resolution computed tomographic scans were obtained at l-ram intervals, They confirmed the enlargement of the vestibular aqueducts, greater on the left side (Fig. 5). The vestibules were also enlarged bilaterally, but no other inner ear anomalies were present. The temporal bones were otherwise normal. No abnormalities were present in the cerebellopontine angle. The patient was maintained on a no-addedsalt diet and reported a marked decrease in the frequency and severity of vertiginous episodes,
DISCUSSION The vestibular aqueduct is a bony canal in the otic capsule; it contains the endolymphatic duct, which originates from the ubicle and saccule in the vestibule and terminates at an orifice on the posterior surface of the petrous pyramid. ~ In the last 25 years, multiple gross and histologic studies of the vestibular aqueduct have confirmed the variability in size and shape of this structure. 4-6 Many m e a s u r e m e n t s have been taken, including length, diameter of internal and external apertures, width, height, area, and angulation. The range of values determined varies, depending on the technique of measurement and the method of tissue preparation. Radiologically, measurements of the vestibular aqueduct are obtained halfway between the external aperture
American Journal of OtoloryngoJogy 414
and the c o m m o n crus. An aqueduct is considered enlarged whenever its anteroposterior diameter is 1.5 mm or greater. 2 Valvassori and Clemis 1 reported 50 cases of enlarged vestibular aqueducts. In 60 per cent of the cases other r a d i o g r a p h i c a l l y identifiable anomalies of the inner ear were present. These investigators concluded that the enlarged vestibular aqueduct represents an arrested phase of inner ear development. Congenital or early acquired hearing loss was frequently involved. A family history of hearing loss was not an important factor in their study, Finally, vestibular complaints were of little consequence. The present case report is important for several reasons. Early d o c u m e n t a t i o n of mixed, nonprogressive, congenital hearing loss reaffirms the finding that the enlarged vestibular aqu e d u c t is associated with audiometric abnormalities. Vertigo, which was previously reported to be mild or inconsequential, may be of greater i m p o r t a n c e than suspected. Our case affords documentation of vestibular testing abnormalities in association with episodically disabling vertigo. We conclude that the enlarged vestibular aqueduct comprises abnormalities not only in the structure of the inner ear, but also in the physiology of the auditory and vestibular systems.
References 1. Valvassori GE, Clemis ]D: The large vestibular aqueduct syndrome. Laryngoscope 88: 723-728, 1978 2, Valvassori GE: The vestibular aqueduct and associated anomalies of the inner ear, Otolaryngol Clin North Am 16:95-101, 1983 3. Anson BJ, Donaldson ]A: Surgical Anatomy of the Temporal Bone and Ear, ed 3. Philadelphia, WB Saunders Co, 1961, pp 64; 396 4, AnsanBJ, Donaldson]A, Warpeha RL, etah A critical appraisal of the anatomyof the perilymphatic system in man, Laryngoscope 74:945-966, 1964 5. Ogura Y, Clemis JD: A study o[ the gross anatomy of the human vestibular aqueduct, Ann Otol Rhinol Laryngol 80:813-825, 1971 6. Kodama A, Sando h Dimensional anatomy of the vestibular aqueduct and the endolymphatic sac (rugose portion) in human temporal banes, Ann Otol Rhinol Laryngol 91 (suppl 96]:13-20, 1982