Indian Pediatrics 1999; 36:401-406 

Mondini dysplasia of the Inner Ear with CSF Leak - A Rare Cause of Recurrent Meningitis

From the Departments of Pediatrics and Otorhino- laryngology*, Seth C.S. Medical College and K.E.M. Hospital, Mumbai, India.

Reprint requests.~ Dr. M.N. Muranjan, Lecturer of Pediatrics K.E.M. Hospital, Parel,
Mumbai 400012, India.

Manuscript Received: July 7, ]998; Initial review completed: August 6. 1998;
Revision Accepted: September 26, 1998.

Meningitis associated with cerebrospinal fluid (CSF) leaks is a common sequel of traumatic fractures or surgery resulting in CSF otorrhea or rhinorrhea. In absence of a precipitating event, CSF leaks can' occur spontaneously through congenital fistulae in the region of the labyrinth and base of the anterior cranial fossa (1), especially when associated with congenital anomalies(2). The Mondini dysplasia is one such rare anomaly, which usually remains undiagnosed until deafness or recurrent meningitis warrants radiological imaging. We report one such child in whom bilateral Mondini dysplasia was detected during the course of investigations for recurrent meningitis.

Case Report

The patient was a 4-year-old male, offspring of a nonconsanguineous marriage, delivered at term after an uncomplicated pregnancy. He was born centrally cyanosed, with two loops of the umbilical cord around the neck and signs of mild asphyxia within the first 24 hours. The subsequent postnatal period was unremarkable, however there was a lag in mental as well as motor development. Social smile was attained by 6 months. The child started reaching out for objects at 6 months. By 12 months head control had been achieved, whereas sitting unaided and independent walking were attained by 15 and 18 months, respectively. The child was making vowel sounds by 18 months, could point to familiar objects by 3 years, but even at 4 years was unable to speak in sentences.

The first documented episode of meningococcal meningitis was at 3 years of age; followed by a second, 6 months later. On both the occasions he was adequately treated at a local hospital with 14 days of intravenous Ceftriaxone. He had received 2 doses of meningococcal vaccine and oral Rifampicin prophylaxis, which failed to prevent a third recurrence and prompted a referral for investigations. During this admission, on careful probing the parents denied history of antecedent trauma or recurrent infections. The child was noted to be microcephalic, but other anthropometric parameters were normal. There were no facial dysmorphisms, physical or systemic abnormalities. Neurologically, tone, power, deep tendon reflexes and plantar responses were normal. Except for a left LMN type of facial paresis, other cranial nerve examination was normal.

He was tested for immunolgic abnormalities. Total white cell count was 11000/cumm, absolute lymphocyte count was 3520/cumm with T cells constituting 65% of the population. Leucocyte phagocytosis opsonisation and nitroblue tetrazolium reduction test were normal (8 f%, 61 % and 100%, respectively). The levels of IgG, IgM and IgA were within the normal range for age and serum C3 and C4 levels were normal. ELISA test for HIV was nonreactive. Having ruled out immunologic abnormalities, he was. referred for an Otolaryngologic evaluation which revealed bilateral profound sensorineural hearing loss (SNHL) on BAER testing. Bilatenil Mondini malformation of the cochlea (more severe 'on the right) was diagnosed on temporal bone high resolution CT (HRCT) scans (Fig. 1) with otitis media and mastoiditis of the' left. ear. A cisternography with metrizamide' detected CSF fistula through the left internal aCQustic canal (lAC). A left ear exploration was done. No defect or leak could be demonstrated at the time of surgery through tegmen plate, sinus plate, round window or oval window. The ossicular chain was intact but the stapes was thick; almost a solid piece of bone, and fixed. The round window reflex was absent, confirming fixation of the stapes. Since no obvious leak was apparent, the probable sites of leak were sealed off. The child was discharged a week later.

Fig.1. HRCT showing the mondini dysplasia. The cochlea (1) is represented by a sac-like remnant; (2) = middle ear cleft with "ice-cream" cone appearance of ossicles; and (3) = internal acoustic meatus

 

Fig. 2. CSF leak along the left vestibulocochlear nerve through a widely patent IAC (while on MRI T2 weighted image), indicated by arrow. On the right side, SCF is normally seen stopping short at the fundus of the vestibulocochlear nerve. CSF is visualized tracking through the eustachian tube (curved arrow) and filling up the middle ear cleft (arrow head)

Unfortunately, meningitis recurred at 4 years of age. This time a MRI was advised. The MRI now precisely defined the site of leak on the left through a patent lAC via a deficient fundus into a dysplastic vestibule and CSF was seen filling the. middle ear cleft and. tracking down the left eustachian tube (Figs. 2 & 3). The child was subjected to re-exploration of the left ear. The leak was apparent through the stapes footplate. The facial nerve in this area (second genu) was dehiscent and abutting against the stapes. Since there was total deafness on the left, the stapes along with the footplate was removed and CSF was seen gushing through the oval window. The leak was sealed appropriately. Post operatively, the child developed facial paresis on the left. After a 4 week course of intravenous Ceftriaxone with steroids and a documented CSF cure, he was discharged. He was seen 6 months following surgery. The facial paresis had not recovered completely, but there was no recurrence of meningitis; though the period was too short to be of significance.

 

Fig. 3. Simplified sketch of the MR image. The CSF (depicted as a stippled area) along the leftvestibulocochlear nerve (VCN) leaks into the middle ear cleft (ME) and along the eustachian tube (ET). On the right, the subarachnoid space with the CSF surrounding the VCN is ending normally at the fundus of the nerve. L = Left, R = Right.

Discussion

In the antibiotic era, meningitis is rarely difficult to treat or eradicate; but when recur- rent, it poses a diagnostic challenge. In absence of a breach in mucocutaneous barriers serving as portals for infecting organisms, a battery of investigations need to be under- taken for diagnosis of immune deficiencies which include immunoglobulin and complement levels, tests for functional leucocyte abnormalities, as well as neuroimaging to detect cranial defects. .Meningococci and pneumococci are the pathogens causing recurrent meningitis as a result of complement deficiency, functional or anatomic asplenia, hypogammaglobulinemia and cranial defects(3).

Our child presented with recurrent meningococcal meningitis. Investigations excluded immunologic incompetence. The inner ear anomaly, associated CSF - perilymph fistula via the lAC and CSF leak into the middle ear and eustachian tube was demonstrated by modem neuroimaging, namely HRCT and MRI.

Cranial defects and the resultant CSF fistulae are notoriously difficult to detect radio- logically(1,4). Traditional modalities for diagnosis of inner ear anomalies such as skull polytomography(5) and intrathecal instillation of fluorescent dyes and radioisotope tracers to detect CSF fistulae have given way to CT with metrizamide cistemography and MRI as imaging techniques of choice(4,6-8). Anomalies of the labyrinth and middle ear are best diagnosed on HRCT(2).

Inner ear anomalies like the Mondini dysplasia with CSF fistula should be suspected in deaf children with recurrent meningitis(4,7), especially those having stigmata of syndromes such as Klippel-Feil, Pendred, DiGeorge and chromosomal trisomies(7,9). In our patient, the malformation occurred in isolation, there being no characteristic features of any of the preceding syndromes.

The classical Mondini malformation consists of 1^1/2 cochlear coils instead of the usual 2^1/2, a cystic dilatation of the common apical chamber with absence of interscalar septum between the middle and apical coil and a hypoplastic modiolus. Etiologically it is believed to result from a developmental arrest at the sixth or seventh week of embryonic life possibly due to teratogenicinsults(9,10). The anatomic and histopathologic characteristics have been reviewed extensively in otolaryngologic literature(5,7).

A variety of otologic anomalies have been described; involving semicircular canals, vestibule, endolymphatic sac and duct, ossicular chain, facial canal, round window, oval window and IAC(8,l0). Our patient was noted to have a dehiscent facial canal at surgery. The stapes was abnormal, with a thick- ened suprastructure. A defect in the footplate served as a site for pathogens to gain access to the subarachnoid space. The lAC was widely patent, resulting in CSF-perilymph fistula along the perineural sheath of the vestibulocochlear nerve. Similar defects of the stapes and lAC have been described in ears with the Mondini malformation presenting with recurrent meningitis(2,4,6,7).

These children may be referred for hearing loss (HL), but often it is to the pediatrician that they present with recurrent meningitis. There is a record of 29 admissions with 20 attacks of meninigitis in a child before the underlying anomaly was suspected and diagnosed(4). The HL is sensorineural, resulting from abnormalities of organ of Corti, and progressive due to altered pressure in the perilymphatic space as a result of its communication with the subarachnoid space(2). Mixed HL may also occur, the conductive component either due to ossicular abnormality or CSF otorrhea. In fact, conductive deafness due to fluid in the middle ear is often not perceived, occurring as it does in a ear deaf due to Mondini dysplasia. In presence of an intact tympanic membrane, CSF in middle ear does not manifest as otorrhea; but may be seen trickling through the eustachian tube orifice on nasopharyngoscopy or manifesting as rhinorrhea if the leak is profuse(7). The child's parents had not noted the deafness, possibly attributing the speech delay as part of overall developmental lag. Both on otoscopy and nasopharyngoscopy, no CSF leak could be detected. Though mental retardation has not been reported with isolated Mondini malformations, its presence in our patient could probably be a sequel of the hypoxic-ischaemic event suffered during labor.

Though rare, inner ear anomalies must be suspected when recurrent meningitis occurs in a deaf child (particularly when deafness is unilateral) and in children with certain craniofacial syndromes known to be associated with SNHL; especially in the absence of antecedent trauma. The associated CSF-perilymph fistula and leak are best diagnosed on MRI ot CT with metrizamide cisternography. Surgery may not always result in definitive cure, multiple attempts often being necessary(4,1l). Whenever feasible amplification aids must be prescribed since some residual hearing may be preserved(10).

Acknowledgement

The authors wish to thank Dr. P.M. Pai, Dean of the Seth G.S. Medical College & K.E.M. Hospital, Mumbai, for granting per- mission to publish this article.
 

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