Oval window perilymph fistula in child with recurrent meningitis and unilateral hearing loss

Abstract

A 2-year-old boy presented to Ears, Nose and Throat (ENT) surgeons with unilateral hearing loss. Following a prodrome of upper respiratory tract infection (URTI), he developed two episodes of pneumococcal meningitis in quick succession. This case demonstrates an unusual cause of perilymph fistula diagnosed on imaging and confirmed surgically. He had failed the Newborn Hearing Screening Programme and was therefore referred to audiology, who confirmed profound sensorineural hearing loss in the right ear. MRI showed incomplete partitioning (type 1) of the right cochlea, suggesting cerebrospinal fluid (CSF) leak from the region of the stapes. Exploratory tympanotomy confirmed this, and proceeded to CSF leak repair, obliteration of the Eustachian tube, subtotal petrosectomy, abdominal fat grafting and blind sac closure. Although middle ear effusions are common; particularly in children with recent URTI, the possibility of otogenic CSF leak needs to be considered, especially in cases of recurrent meningitis.

Background

Meningitis is a potentially fatal infection which may result in life-long complications and disability from irreversible neurological damage or hearing loss if not recognised and treated promptly.^{1 2} Although meningitis can affect patients of any age, it is most prevalent from birth to 4 years.³ Meningitis can be caused by bacterial, viral or fungal infections⁴; middle ear infections and sinusitis are recognised causes of bacterial meningitis.⁵ While congenital inner ear dysplasia and a history of trauma is found in a number of such cases, spontaneous cerebrospinal fluid (CSF) leak in patients with normal anatomy is also recognised.⁶

Recurrent bacterial meningitis warrants prompt investigation and treatment of underlying cause. In particular, CSF leak needs to be considered. This is particularly true if there is concomitant hearing impairment. Although studies have quoted up to 25% of children with otogenic CSF leak as the source of recurrent meningitis present with normal hearing and imaging.⁷ Therefore, physicians should remain vigilant and maintain a high level of suspicion.

Meningitis is associated with developing profound sensorineural hearing loss accompanied by labyrinthitis ossificans.⁸ It is therefore important to monitor the hearing of all patients who develop meningitis, as in these cases, prompt intervention is essential as cochlear implantation may be required before the cochlea ossifies and intervention becomes impossible.

Case presentation

The patient is a 2-year-old boy who failed the neonatal transient evoked otoacoustic emission test in his right ear as part of the Newborn Hearing Screening Programme. This prompted referral and assessment with automated auditory brainstem response, which he also failed and severe sensorineural hearing loss of the right ear was confirmed. He was otherwise fit and healthy with no relevant medical or surgical background. Despite travels abroad, the UK routine childhood vaccination schedule was adhered to. He was up to date with immunisations including the 13-strain pneumococcal conjugate vaccine (PCV-13) at the time of presentation. There is no known family history of hearing loss, renal or neurodevelopmental impairment.

Despite difficulty localising sounds, he is meeting developmental milestones, is sociable and initiates conversations. During the process of investigating his hearing loss, he developed two episodes of bacterial meningitis in quick succession, prompting further evaluation and assessment.

Investigations

Tympanometry in the neonatal period showed normal bilateral ‘type A’ patterns with normal compliance. Tympanometry subsequent to the onset of the first episode of meningitis demonstrates a flat ‘type B’ trace on the right with normal ear canal volume indicating right middle ear effusion. A peaked ‘type A’ trace on the left indicated an aerated, normal left middle ear.

Lumbar puncture was carried out during each episode of meningitis, and on both occasions, cultures showed Streptococcus pneumoniae. On the first episode of meningitis, blood cultures also showed fully sensitive S. pneumoniae. Serotype 35F was identified through analysis of the first blood culture, attempts to serotype the subsequent samples were unsuccessful.

MRI with three dimensional (3D) T2 high resolution sequence on the inner ears demonstrated right congenital cochlear dysplasia, with incomplete partitioning type 1,⁹ a widened internal auditory canal with deficiency of the lamina cribrosa, enlargement of the oval window and aplasia of the cochlear nerve (see figures 1 and 2). Left ear anatomy was unremarkable. The presence of fluid extending between the labyrinth and the middle ear through an enlarged oval window suggested CSF leak from the stapes. Further evaluation was done using CT petrous bones, which showed an opacified middle ear and confirmed the enlarged oval window.

Figure 1.

Axial 3D T2 WI (Fast Imaging Employing Steady-state Acquisition (FIESTA) sequence) shows malformed right labyrinth with cystic appearance of the vestibule and the cochlea in keeping with common cavity (white arrow). The stapes is surrounded by fluid and is connected with a markedly enlarged oval window (arrowhead). There was fluid filling the tympanic cavity, mastoid and along the course of a patent Eustachian tube (double arrow). Note normal inner ear anatomy on the left.

Figure 2.

High resolution petrous bone CT confirm enlargement of the oval window (arrow in A), malformed labyrinth and fluid filling the tympanic cavity and mastoid cells (arrow in B).

The hearing in the contralateral ear was closely monitored and remained within normal limits.

Treatment

Pneumococcal meningitis was initially treated with intravenous ceftriaxone before a further 3 weeks with oral amoxicillin and then prophylactic penicillin was prescribed. Unfortunately, he rapidly developed a second episode of bacterial meningitis, and surgical treatment for the CSF leak was expedited.

The 23-strain pneumococcal polysaccharide vaccine (PPV-23) is considered now that he is over the age of 2.

On exploratory tympanotomy, the CSF leak was found to be arising from the circumferential margin of the oval window, in keeping with the imaging findings. A lateral petrosectomy was performed for optimum access. Clearance of adhesions from the oval window resulted in the stapes being mobilised and removed to allow packing of the defect (see figure 3). The defect was packed with temporalis fascia, and the leak was controlled. The repair was tested and then reinforced with fibrin glue. The Eustachian tube was obliterated with fascia and bone wax. A blind sac closure of the ear canal was performed. The petrosectomy defect was packed with an abdominal fat graft. A postoperative course of ceftriaxone was given for 4 weeks to treat any residual infection.

Figure 3.

Clearance of adhesions from the oval window resulted in the stapes being mobilised and removed to allow packing of the defect.

Outcome and follow-up

The patient was discharged day 2 postoperatively. At 8 weeks follow-up there is no clinical evidence of CSF leak, the blind sac closure had healed well and there is no further reported signs of meningism.

Discussion

Otogenic CSF leak can be broadly categorised into congenital or acquired, unilateral or bilateral.¹⁰ It consists of an abnormal connection between the middle and inner ear (perilymph leak), and also an abnormal or persistent connection between the CSF and inner ear (CSF leak). While a leak is more likely in patients with abnormal inner ear anatomy, it is important to note that spontaneous CSF leak in patients with normal anatomy is recognised.⁶ In this case, it is likely that the leak arose from the persistent exposure of the oval window to intracranial pressure fluctuations due to the cochlear dysplasia. The dehiscence of the vestibule into the internal auditory meatus (IAM) meant that the stapes, which is mobile within the oval window, was subject to persistent pressure fluctuation with coughing/straining/etc. In cases of cochlear dysplasia where the vestibule is continuous with the IAM, for example incomplete partitioning type 3, it is more common for the stapes to be fixed.¹¹ It is likely that the lack of fixation led to the CSF leak. This case raises a number of important points to consider.

First, this case is a reminder of the importance of investigation of recurrent meningitis. In this case, the referral to ENT had been made even prior to the second episode of meningitis due to the known cochlear dysplasia on one side. In the presence of vestibulocochlear dysplasia and an ipsilateral middle ear effusion, pneumococcal meningitis is highly suggestive of CSF leak and an urgent referral to an appropriate centre should be made. Even in the absence of such history, patients with recurrent bacterial meningitis should be investigated with imaging of the anterior and lateral skull base to look for evidence of CSF leak. Patients with CSF leak from the anterior skull base are more likely to present with watery anterior rhinorrhoea, however, a proportion of patients presenting in this way will have a fluid in the middle ear cavity, and this can be investigated with tympanocentesis and/or exploratory tympanotomy. CSF rhinorrhoea can be confirmed by transferrin testing of the leaking fluid.¹² A small case series of more recently published literature suggests that 25% of cases with otogenic CSF leak may present with normal radiology and hearing tests.⁷ This highlights the difficulties physicians face when diagnosing an otogenic CSF leak and the ability to successfully carry out repair of the defect before complications such as meningitis may arise. Where CSF leak is thought to be highly likely, but a source is unknown, radionucleotide cisternography is an option, but this is exceptionally challenging in a paediatric population.

Second, it is essential to monitor the hearing of patients with meningitis. Hearing monitoring may provide a clue to aetiology, in cases such as these but also in cases with normal anatomy and a unilateral middle ear effusion. Hearing monitoring in patients with meningitis is also important as hearing loss may indicate fibrosis and subsequent ossification of the cochlear duct, and urgent cochlear implantation may be needed before ossification makes insertion of a cochlear implant impossible.¹³

Third, it is important to consider the roles of pneumococcal vaccination and prophylactic antibiotics in these patients. Over 90 serotypes of S. pneumoniae have been identified.¹⁴ Different strains cause varying symptoms ranging from mild to life-threatening, some of which may cause invasive pneumococcal disease such as meningitis and septicaemia. Vaccinations were developed to protect against the most common and lethal strains. There are currently two pneumococcal vaccines, PCV-13 which is offered as part of the routine childhood immunisation schedule in the UK and PPV-23 which is available for children and adults aged between 2 and 64 years old who are at higher risk of pneumococcal infections.¹⁵ The Centre for Disease Control and Prevention considers individuals with immunocompromising conditions, CSF leak and cochlear implants in the high-risk group. However, the PPV vaccine has been found to be ineffective in children under the age of 2.¹⁶ Furthermore, in this case, serotype 35F which was isolated from the initial blood culture is not protected against in either of the pneumococcal vaccines.

After the initial episode of meningitis, prophylactic penicillin was started, but this did not have a sufficiently broad spectrum of activity, or dose within the middle ear to prevent further infection.

It is therefore essential to note that repair of the CSF leak, rather than prophylactic antibiotics, is the essential step in the management of these patients.

Surgical exploration is the gold-standard of management of otogenic CSF leak.¹⁷ The nature of the surgery depends on the location of the leak, intraoperative findings, and underlying hearing function of the affected ear. CSF leaks may be repaired maintaining the hearing function in the ear when the leak arises from the tegmen, but this is very difficult when the leak arises from the oval window. In cases where there is a pre-existing hearing loss, subtotal petrosectomy, abdominal fat grafting, obliteration of the Eustachian tube and blind sac closure provide additional layers of support to the CSF leak repair and protection from further infection. While they remove any useable hearing from that ear, they do not preclude cochlear implantation in future if the hearing on the contralateral side is lost; although in this case, the cochlear nerve deficiency and cochlear dysplasia would limit the potential benefit from such a device.

Learning points.

• Recurrent meningitis should prompt further investigation for cerebrospinal fluid (CSF) leak—including imaging of the anterior and lateral skull base.

• All paediatric patients with unilateral/bilateral sensorineural hearing loss must have imaging (an MRI) soon after diagnosis.

• Prompt management of CSF leak is essential to prevent recurrent episodes of life-threatening meningitis.

• All patients with bacterial meningitis should have their hearing monitored to identify sensorineural hearing loss and labyrinthitis ossificans as early as possible.

• In patients with recurrent meningitis and unilateral middle ear effusion, tympanocentesis can confirm CSF leak