Case presentation

Patient familial consent was received for this case report. The patient was a five-year-old male with bilateral profound sensorineural hearing loss and no prior imaging studies. He also had a history of chronic left-sided clear rhinorrhea that had not previously been recognized as CSF. During a myringotomy to address recurrent otitis media, a cut was made in the usual inferior location in the left tympanic membrane. Clear fluid rapidly filled the ear canal and was suctioned. The fluid was continuously emitted in a pulsatile fashion from the incision despite repeated suctioning. A CSF leak was suspected and 2 mL of fluid was collected to be tested for beta-2 transferrin. It was then decided to decrease intracranial pressure and to close the myringotomy locally to prevent additional leakage and stabilize the patient for further assessment. Using an endoscope, a butterfly biodesign graft was deployed to close the perforation, but CSF continued to leak. A fibrin sealant was then implemented, followed by a gelatin sealant, and then additional fibrin sealant, which seemingly contained the leak. This was confirmed by performing a gentle Valsalva maneuver. The patient was then handed off to the anesthesia service and transferred to the PICU intubated. Given the patient’s abnormal CSF otorrhea, a labyrinthine anomaly was suspected and imaging was ordered. A CT scan of the left ear showed a large cystic cavity within the otic capsule with absence of internal bony architecture, dysmorphic semicircular canals, and an enlarged internal auditory canal, consistent with a common cavity deformity (Figures 1, 2).

Figure 1: Coronal CT of the left temporal bone demonstrating a cystic cochleovestibular malformation (common cavity deformity) with a focal bony deficit connecting the cystic cavity to the middle ear space (blue arrow). This abnormal communication corresponds to the pathway through which CSF was found to egress intraoperatively from the vestibule through the oval window.

Figure 2: Axial CT of the left temporal bone showing a bulbous, widened internal auditory canal (green arrow) and a common cavity deformity replacing the normal cochlear and vestibular architecture (blue arrow). These findings are consistent with common cavity deformity and explain the congenital fistulous connection that permitted high-flow CSF leakage into the middle ear.

Ten days later, a left lateral temporal bone resection was performed to identify and address the underlying source of the CSF otorrhea. The surgical course was initiated with standard posterior ear canal incisions, leading to the postauricular exposure of the mastoid cortex. The critical intraoperative finding occurred immediately upon elevation of the tympanomeatal flap, revealing a copious volume of clear, pulsatile drainage. This finding, which was inconsistent with typical middle ear effusion, confirmed a high-flow CSF leak, with fluid samples collected for definitive beta-2 transferrin analysis.

To achieve adequate visualization of the temporal bone floor and roof, the medial external auditory canal (EAC) skin and tympanic membrane were resected, followed by removal of the incus and a partial mastoidectomy with resection of the bony EAC. Inspection of the most common site for spontaneous leaks, the tegmen tympani, confirmed that it was intact, shifting the diagnostic focus. The presence of malformed semicircular canals further indicated a congenital inner ear anomaly. After skeletonizing the tympanic and the proximal mastoid facial nerve, the origin of the leak was precisely identified. Inspection of the oval window revealed high-flow CSF egressing from the vestibule through a congenital dehiscence in the oval window/footplate region, consistent with the underlying inner ear malformation. The stapedius tendon was then divided and the stapes footplate removed to fully expose the vestibule for packing.

The high-flow nature of the leak was managed with a multilayer closure technique. Temporalis fascia was harvested and packed tightly into the vestibule. This primary seal was augmented with a supportive cartilage graft placed over the promontory, stabilizing the packing beneath the malleus. To prevent CSF from being forced back up the Eustachian tube, its orifice was permanently occluded with a deep plug of sternocleidomastoid muscle. A Valsalva maneuver was performed to confirm a watertight seal. The final deep layer consisted of an absorbable collagen-based matrix patch placed over the medial temporal bone, secured with fibrin sealant. For protection, a pedicled temporalis muscle flap was rotated over the entire defect and secured to the surrounding fascia. Finally, the external auditory canal was permanently closed with a blind sac closure to eliminate any remaining pathway for fluid drainage or ascending infection. Postoperatively, the CSF otorrhea resolved, as did the patient's longstanding clear rhinorrhea. At follow-up, there was no recurrence of otorrhea or rhinorrhea and no episode of meningitis.