SM Shah, SS Prabhu, RH Merchant
Department of Paediatrics, Bai Jerbai Wadia Hospital for Children, Parel, Mumbai - 400 012, India. , India
S M Shah
Department of Paediatrics, Bai Jerbai Wadia Hospital for Children, Parel, Mumbai - 400 012, India.
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Shah S M, Prabhu S S, Merchant R H. Mondini defect. J Postgrad Med 2001;47:272-3
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Shah S M, Prabhu S S, Merchant R H. Mondini defect. J Postgrad Med [serial online] 2001 [cited 2016 May 28 ];47:272-3
Available from: http://www.jpgmonline.com/text.asp?2001/47/4/272/170
A 3-year-old girl presented with repeated pyogenic meningitis following a minor head injury at 1 year of age. During the last two years she had three episodes of pyogenic meningitis due to staphylococci and pneumococci. On detailed questioning of parents, we could obtain a definite history of clear watery discharge from right nostril. On examination, there was pallor, neck rigidity and asymmetry of face. CNS examination revealed a right-sided spastic hemiparesis with right-sided facial paresis.
Cerebrospinal fluid (CSF) examination showed cell count of 3750/cmm with 95% polymorph, proteins and sugar were 12 mg /dl and 21 mg/dl respectively. Her Mauntoux test was negative and radiogram of chest was normal. Test for HIV antibodies was negative. There was sensorineural deafness in right ear with hearing threshold of 38 db.
Magnetic resonance (MR) cisternography showed CSF leak into the middle ear. High resolution computerised tomographic (CT) scan of temporal bone showed right-sided Mondini defect. It showed dysplasia of the vestibulocochlear complex, with incomplete cochlear turns [Figure:1]. The internal auditory canal entered into dysplastic vestibulocochlear complex. There was CSF leak in the middle ear due to communication of the internal auditory canal with dysplastic dilated vestibulocochlear complex through the dehiscent lamina cribrosa. The mastoid air cells and middle ear cavity show fluid level with patchy opacification [Figure:2]. MR cisternography showed fluid in the right middle ear and mastoid air cells due to CSF leak [Figure:3].
Patient was treated with antibiotic and after two weeks of antibiotic treatment CSF showed clearance. An exploratory tympanostomy was done and defect was closed by a patch of fascia. Patient is asymptomatic on follow-up.
The reported incidence of significant sensorineural hearing loss in young children varies from 1:1000 to 1:2000. Mondini defect accounts for 50% of cases of sensory neural hearing loss unassociated with any known syndrome. Mondini defect which was first described by Mondini in1791, is a developmental anomaly of otic capsules with an arrest in the development of the cochlear modiolus in the seventh foetal week. This leads to development of only one and half turns of cochlea instead of normal two and half turns of cochlea. The cochlea is an amorphous sac lacking a modiolus or central bony spiral without the normal basal turn. There is absence of the interscalar septum in the upper part of the cochlea, with the formation of a common scala (scala communis). There is a wide communication between the cochlear sac and the vestibule, which is itself abnormal and enlarged especially in horizontal plane. The semicircular canal may be dilated to a varying degree, especially lateral ones.
Patients with the Mondini defect are at an increased risk of developing recurrent meningitis or perilymphatic fistula. They are predisposed to develop a CSF leak due to the enlarged cochlear aqueduct or an abnormal connection between the internal auditory canal and membranous labyrinth. The labyrinthine malformation is often accompanied by a defective stapes and the defect consists of a hole in its footplate. The cerebrospinal fluid enters into middle ear through trans-labyrinthine route via oval window or less commonly round window leading to CSF rhinorrhoea or CSF otorrhoea. The fistula is either spontaneous or as a result of head injury as in our case.
Cerebrospinal fistula associated with Mondini defect presents in first 5 to 10 years of life with CSF rhinorrhoea if tympanic membrane is intact. CSF passes down the Eustachian tube causing a nasal discharge. It can also cause CSF otorrhoea if there is a perforation in the tympanic membrane, or if myringotomy is performed for presumed serous otitis media. At times meningitis, which may be recurrent, is sole presenting manifestation of the defect. In a series of patients with recurrent meningitis Ohlm et al found that 67% of patients had unilateral Mondini defect. Hence in any child with sensorineuronal deafness or two unexplained attacks of meningitis make a CT study of temporal bone is mandatory.
The deafness in Mondini defect is sensorineuronal. It may be severe and complete, but it is difficult to diagnose and assess, especially in a young child. It is frequently unrecognised if it is unilateral, as in our case. In some cases Mondini defect is associated with congenital cytomegalovirus infection or Pendred syndrome.
The CSF leak is best visualised on MR cisternography and Mondini defect is best seen with high-resolution temporal bone computed tomography.
The management of Mondini dysplasia is based on clinical presentation. In asymptomatic patients, most otologists adopt wait and watch policy. Patients are advised to avoid contact sports because of the increased risk of CSF leak following minor head injury. Middle ear infections are treated aggressively because of increased risk for meningitis. Hearing rehabilitation, including amplification and especially educational efforts are also included. Cochlear implantation with aural rehabilitation may augment acquisition of language and enhance education of patient with Mondini malformation and profound sensorineural impairment when conventional amplification is ineffective. In a symptomatic patient surgical exploration and packing of vestibule with temporalis muscle is recommended. In some of the cases a stapedectomy is performed and the vestibule is obliterated.
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