Introduction
Congenital oval window defect is a rare anatomical abnormality that can predispose patients to recurrent cerebrospinal fluid (CSF) leaks and life-threatening bacterial meningitis [
1]. This condition is seldom reported in literature, with only a few documented case reports for the past few decades linking congenital oval window abnormalities to recurrent meningitis episodes due to persistent CSF leakage. Patient presentations include recurrent meningitis or hearing loss, often necessitating extensive diagnostic imaging for accurate identification and confirmation. This case highlights a particularly complex clinical scenario of a 19-year-old male patient with a congenital left oval window defect, leading to recurrent meningitis despite multiple prior surgical interventions. Imaging revealed a recurrent CSF leak at the oval window, necessitating a specialized multi-layered surgical approach for repair. This case underscores the critical role of comprehensive radiological assessment and individualized surgical strategies in managing rare congenital defects complicated by recurrent infections.
Case Report
A 19-year-old male patient with a known congenital left oval window defect who underwent multiple previous repairs was referred to the ENT department during admission in our tertiary adult hospital for recurrent bacterial meningitis. He presented with symptoms similar to those of previous culture-proven meningitis, including fever, headache, and neck stiffness. However, on clinical examination, there were no neurological deficits, and Kernig and Brudzinski’s signs were negative. On otoscopic examination, the tympanic membrane was intact, but there was a large collection of fluid pulsating in the roof of the mastoid cavity and middle ear (
Fig. 1). There was otherwise no vestibular deficit. Nasoendoscopic examination showed no frank fluid draining from the left Eustachian tube. Audiometric evaluation revealed left profound hearing loss with normal right-sided hearing (
Fig. 2). He was commenced empirically on ceftriaxone, vancomycin, and acyclovir upon admission for early source control as per previous sensitivities. The patient eventually agreed to a lumbar puncture on the third day of admission, which showed features suggestive of bacterial meningitis (low glucose, high opening pressures) but was culture negative. He then recovered well from this episode of meningitis.
The patient has had recurrent admissions to a children’s hospital for bacterial meningitis since he was 7 years old. Initial examination of his left ear then revealed otitis media with effusion. However, persistent otorrhea after myringotomy prompted computed tomography (CT) scans, which showed a left-sided type 1 incomplete partition deformity of the left ear with a left congenital oval window defect leading to communication of the cranium with the middle ear. He underwent left canal wall down mastoidectomy and oval window defect repair and remained well for 3 years. He had two more episodes of bacterial meningitis at ages 10 and 11, which prompted repeated exploratory tympanotomy and repair of the CSF leak after each episode. The first surgery revealed an area of CSF leak at the oval window, which was fluctuant and bulging, while the second surgery revealed a leak over the tegmen tympanicum instead. To reduce the risk of recurrent bacterial meningitis, he was then started on regular pneumococcal vaccinations.
During his current admission, high-resolution CT imaging of the temporal bone revealed widened left oval window and absent stapes footplate once again (
Fig. 3), with an intact tegmen tympani. The middle ear and mastoid were completely opacified. T2-weighted magnetic resonance imaging (MRI) of the inner and middle ear demonstrated fluid signals in the middle ear and mastoid, which were similar to the fluid signals in the internal acoustic meatus and vestibule (
Fig. 3). This raises the suspicion that there was likely CSF within the middle ear and mastoid, which is most probably leaking through the oval window defect and absent stapes footplate. MRI also showed expanded internal acoustic meatus, fundus, and inner ear, with similar fluid signal within the distended Eustachian tube. Nonetheless, the other differentials for the fluid signal in the middle ear include otitis media with effusion and granulation formation from chronic otitis media.
To reduce the risk of recurrent meningitis, the patient underwent left external ear canal transection, obliteration of mastoid and middle ear with harvest muscle and abdominal fat, and transnasal obliteration of left Eustachian tube. Intraoperatively, CSF was encountered whilst raising the meatal flap and the oval window membrane was bulging with small amount of fluid leaking around it (
Fig. 4). The oval membrane bulge was compressed with pieces of bone harvested from the remnant mastoid cortex and TISSEEL. The oval window defect was then reinforced with multiple layers of fascia, muscle, and fat. The facial nerve was in its expected position and the bony canal over the facial nerve was intact intraoperatively.
Postoperatively the blind sac closure remained intact, the left Eustachian tube orifice was scarred down with no obvious lumen, and the patient has remained free of bacterial meningitis without any vestibular sequelae.
Discussion
Congenital oval window defect is rare and may present with recurrent bacterial meningitis secondary to spontaneous cerebrospinal fluid leak via the oval window [
1]. The defect could be due to a faulty development of the stapes, such as a hole in the footplate or absent footplate, of which the latter is seen in our case. It could also be due to displacement of the footplate due to increased vestibular perilymph pressures causing defects in the annulus [
2]. When CSF rhinorrhoea or otorrhea is present in a young patient with hearing impairment, high-resolution CT of the temporal bone should be performed to identify vestibulo-cochlear abnormalities and any other bony defects within the temporal bone.
In this patient, radiology played a crucial role in pinpointing the source of the CSF leak, facilitating more precise preoperative counseling and surgical intervention, given that the patient has had previous surgical repairs of the oval window defect. The T2-weighted MRI complemented the CT as it alluded that the opacification in the middle ear and mastoid seen in the CT was likely CSF due to the similar fluid signal and the communication between the dilated vestibule and the middle ear.