|Year : 2004 | Volume
| Issue : 2 | Page : 86-89
Unilateral congenital stenosis of internal auditory meatus with normal vestibular and facial nerve functions
Hussein J Al Shammari1, Jamal M Al Harbi2, Salwa Ramadan3
1 Consultant Department of ENT Al Adan Hospital, Kuwait
2 Consultant Department of ENT Al Sabah Hospital, Kuwait
3 Consultant Department of Radiology Al Adan Hospital, Kuwait
|Date of Web Publication||12-Jul-2020|
MD Hussein J Al Shammari
P O BOX 1605 Mishref 40167
Source of Support: None, Conflict of Interest: None
Congenital stenosis of the internal auditory meatus is rare and only few cases have been reported.
A case of unilateral congenital stenosis of the internal auditory meatus presenting as a long-standing severe sensorineural hearing loss without vestibular symptoms or facial weakness in a nine-year-old girl is reported. The diagnosis was evident on images obtained on computerized tomography and magnetic resonance imaging. This is the first ever-documented case of its kind in The State of Kuwait.
Keywords: internal acoustic meatus, stenosis, congenital malformation, hearing loss
|How to cite this article:|
Al Shammari HJ, Al Harbi JM, Ramadan S. Unilateral congenital stenosis of internal auditory meatus with normal vestibular and facial nerve functions. Saudi J Otorhinolaryngol Head Neck Surg 2004;6:86-9
|How to cite this URL:|
Al Shammari HJ, Al Harbi JM, Ramadan S. Unilateral congenital stenosis of internal auditory meatus with normal vestibular and facial nerve functions. Saudi J Otorhinolaryngol Head Neck Surg [serial online] 2004 [cited 2022 Nov 30];6:86-9. Available from: https://www.sjohns.org/text.asp?2004/6/2/86/289589
| Introduction|| |
Narrowing of the internal auditory meatus secondary to local bone pathology such as exostosis and osteoma or generalized skeletal disease e.g. Paget’s disease, osteopetrosis (Albert’s Schonberg Disease) and fibrous dysplasia is well documented . Association of anomalies of the internal auditory meatus with systemic congenital malformations such as polycystic kidney, cardiac septal defects, skeletal deformities and duodenal atresia have been documented. However, review of English literature shows only a few case reports of congenital stenosis the of internal auditory meatus. The latter may exist either independently or in conjunction with developmental anomalies of the inner ear and often middle ear . Clinical presentation relates to the degree to which the development and function of the cochlear and vestibular components of the eighth cranial nerve and facial nerve are affected.
Computerized tomography is very helpful in the diagnosis of stenosis of the bony meatus whereas magnetic resonance imaging delineates the neural structures within the meatus.
In this report, we present a case of unilateral congenital stenosis of the internal auditory meatus. Diagnostic workup and review of literature is presented.
| Case Report|| |
A nine years old Kuwaiti schoolgirl presented to the Otolaryngology-Head & Neck Services of A1 Adan hospital, State of Kuwait, on January 1999 with a long standing history of hearing loss in her right ear. Three years earlier she had undergone adenoidectomy and bilateral myringotomy for adenoid hypertrophy and serous otitis media but the desired improvement in hearing was not obtained. She denied any spells of dizziness and had never experienced facial weakness. There was no history of mumps, herpes zoster oticus or head trauma. Her mother had pregnancy-induced diabetes but no febrile illness or other risk factors during first and second trimester of pregnancy were obtained. The patient was normally delivered as a full term baby with normal birth weight and without any apparent congenital malformations. There was no history of familial deafness and the other siblings were normal. On examination she appeared to be a healthy child with stable vital signs. There was no apparent facial weakness, disturbance of gait or vision or features suggestive of branchial arch anomalies. Otological examination revealed normal external ears and tympanic membranes. Neurological examination was normal. Tuning fork tests showed a false negative Rinne test and severely reduced absolute bone conduction test on the right side with Weber test lateralized to the left side suggestive of severe sensorineural hearing loss on the right side. The Rinne and Absolute bone conduction tests were normal on the left side. Pure Tone Audiometry showed a 75 dB sensorineural hearing loss on the right side and a normal hearing on the left. Tympanograms showed normal middle ear pressure and compliance, lpsilateral stapedial reflex was present on the left side but absent on the right side. Otoacoustic emission test revealed absence of the cochlear echo on right side. Brainstem evoked response audiometry showed a 30 dB threshold on the left side with normal latencies and a 100 dB threshold on the right side. The vestibular profile revealed robust and symmetrical nystagmus on both sides on bithermal caloric stimulation. Optic fixation suppression was normal. On electronystag- mography ocular saccades demonstrated normal saccadic velocity and symmetry. Visual pursuit and optokinetic tests were normal as well. Anti Varicella titres were normal. A non-enhanced axial and coronal CT scan of the petrous temporal showed marked narrowing of the right internal auditory meatus (less than 2 mm) with dilatation of the vestibule and the horizontal semicircular canal. The cochlea and other semicircular canals were normal and there was no evidence of local or generalized bone disease [Figure 1].
MRI with gadolinium enhancement revealed normal seventh and eighth cranial nerves in the left internal auditory meatus but an obvious discrepancy on the right side where only one nerve could be visualized which continued into the fallopian canal and was thus assumed to be the seventh nerve.
| Discussion|| |
An average cross sectional area of a normal internal auditory meatus is stated to be 4 mm , The neural crest tissue forms an otic placode in the embryo at 22 days gestation. The placode forms a pit and then a vesicle by 30th day. Embryologically, development of meatal portion of vestibulocochlear nerve and bony internal auditory meatus appear to be concurrent , It has been shown in experimental animals that fibres of the vestibulocochlear nerve grow to meet target end organs in the labyrinth through a chemotactic mechanism and this provides impetus for condensation of mesoderm around it which turns into cartilage and subsequently ossifies into the internal auditory meatus . The facial nerve develops independently and is caught in the substance of otic capsule during chondrification.
The embryological events occurring between the 4th and 8th weeks of foeta! life are crucial to occurrence of congenital deformities of the internal auditory meatus. Failure of chemotactic mechanism between growing nerve and target sensory end organs may result in hypoplasia or aplasia of the vestibulocochlear nerve or its components and consequently the internal auditory meatus may have a variable degree of stenosis ,. A stenotic internal auditory meatus may be associated with a normal inner ear , a deformed inner ear such as labyrinthine aplasia (Michel syndrome), common cavity deformity or incomplete partition (Mondini syndrome)  or cochlear nerve agenesis .
Occasionally accompanying middle or external ear anomalies such as Goldenhar syndrome and Treacher Collins syndrome are seen .
Although bilateral anomalies have been described, unilateral anomalies are more common. Guirado, 1992, reported a range of anomalies from stenosis to extreme narrowing to complete atresia. He further described a duplicated meatus with a bony partition and an abnormal communication of cerebrospinal fluid and the tympanic cavity. Shelton et a1,1989, investigated three children with congenital profound hearing loss who had received cochlear implants but had not responded to electric stimulation and attributed it to agenesis of cochlear nerve in association with stenosis of the internal auditory meatus. Acute events in a patient with long standing sensorineural hearing loss in a case of stenotic internal auditory meatus have been reported . Having ruled out a bony tumour, exostosis or a generalized skeletal disease, the stenosis of the internal auditory meatus in our patient appears to be a congenital malformation. The eighth cranial nerve in our patient was presumably too hypoplastic to be seen, its agenesis being unlikely in view of the audiovestbilar profile of the patient. Indeed it is possible that the patient has a normal vestibular component but a hypoplastic cochlear component of the eighth nerve [Figure 2]. We believe that the severe sensorineural hearing loss in our patient is due to hypoplasia of the cochlear nerve. Late presentation is by no means unusual for a unilateral loss. Currently there is no surgical intervention available to correct such anomaly and the aim of management ought to be preservation of hearing in the contralateral ear by avoidance of ototoxic factors.
| Conclusion|| |
Stenosis of the internal auditory canal with norma! facial and vestibular nerve function is extremely rare. Diagnosis is based upon demonstration of narrowed meatus on CT scan and neural structures displayed on MRI.
We wish to express our appreciation to Mrs. Maiyam Al Hussaini for her assistance in manuscript preparation.
| References|| |
Clerico DM, Jahn AF, Fontanella S. Osteoma of the internal auditory canal. Case report and literature review. Ann Otol Rhinol Laryngol 1994;103:619-623.
Yates JA, Patel PC, Millman B, Gibson WS. Isolated congenital internal auditory canal atresia with normal facial nerve function. Int J Pediatr Otorhinol 1997;41:1-8.
Vavassori GE, Pierce RH. The normal internal auditory canal Am J
Anson BJ, DonaldsonJA. Surgical anatomy of the temporal bone and ear.2d Ed.Philadelphia W B Saunders 1973.
Van de Water TR, Ruben RJ. Neurotrophic interactions during in vitro development of the inner ear. Ann Otol Rhinol Laryngol 1984;93:558-564.
Phelps PD, Llyod GAS, Sheldon PW. Deformity of the labyrinth and internal auditory meatus in congenita! deafness British J Radiol 1975;48:973-8.
Terrahe K. Tomographic studies in congenital malformations of internal and middle ears. Ann Radiol 1972;15:247-52.
Lagundoye SB, Martinson FD, Fajemisin AA. The syndrome of enlarged vestibule and dysplasia of lateral semicircular canal in congenital deafness. Radiology 1975;1 15:377-8.
Shelton C, Luxford WM, Tonokawa LL, William W M Lo, House WF. The narrow internal auditory canal in children; A contraindication to cochlear implants.Otolaryngol Head Neck Surg 1989;100:227-231.
Guirado CR. Matformations of the inner auditory canal Rev Laiyngol Otol Rhinol (Bord) 1992;l 13(5):419-421.
Nakamura K, Koda J, Koike Y. Stenosis of the Internal Auditory Canal with VHth and Vlllth Cranial Nerve Dysfunctions. ORL 1999;61:16-18.
[Figure 1], [Figure 2]