Pneumolabyrinth in a Case of Squamous Chronic Otitis Media - a Rare Entity

Abstract

Pneumolabyrinth is a rare entity in a case of squamous chronic otitis media in the practice of otology. We report a case of 56 year male, a known case of Squamous Chronic Otitis Media who was diagnosed as a case of Pneumolabyrinth associated with a Perilymphatic fistula. Diagnosis was done with the help of audiometry and High-Resolution Computed Tomography of Temporal Bone in background of his symptoms. Tympanomastoid exploration revealed a perilymphatic fistula at round window and a labyrinthine fistula of Lateral semicircular canal. The sealing of defect was performed with reinforcement technique by utilizing fascia and fibrin glue.

Introduction

Pneumolabyrinth is an abnormal condition of the inner ear in which air is present by abnormal pathways. It is also called as Pneumocochlea or Pneumovestibule depending on the air site in the inner ear [1]. Pneumolabyrinth associated with a perilymphatic fistula (PLF) is rare. A PLF is an abnormal communication between perilymphatic space and the middle ear with perilymph extravasation into the tympanomastoid cavity. Pneumolabyrinth resulting from PLF has been associated with temporal bone fracture, barotrauma, iatrogenic injury, middle ear surgery, chronic ear disease like cholesteatoma, otologic malignancy, cochlear implantation and may develop spontaneously too [1–3]. Patient presents with variable symptoms related to inner ear like sudden or fluctuating hearing loss, tinnitus, aural fullness and vertigo. It is usually identified on High-Resolution Computed Tomography of Temporal Bone (HRCT-TB) [4].

We report a case of Squamous Chronic Suppurative Otitis Media (CSOM) with pneumolabyrinth involving the vestibule and the cochlea secondary to PLF which was evident on HRCT-TB and the same was verified on surgical exploration.

Case Presentation

56-year male, resident of Kerala, soldier by occupation presented to our centre with new onset fluctuating hearing loss and tinnitus in left ear. Patient was a known case of bilateral Squamous CSOM. The patient on otosopy, had posterosuperior retraction pocket of Pars tensa with cholesteatoma flakes on left side. He had well epithelialized right mastoid cavity (sequalae of previous surgery).

The patient gave history of chronic cough a week ago with raised eosinophil count (as per medical documentation) following which he had fresh onset tinnitus and fluctuating hearing loss on left side. The episodes of left hearing loss and tinnitus was also associated with spinning sensation of surroundings (vertigo), nausea and vomiting. On audiological evaluation, the patient was found to have bilateral mixed hearing loss (more on right side). Previous audiometry reports were suggestive of right mixed (predominantly conductive) and left conductive hearing loss. Neuro-otological examination was normal except for audiometric loss as above.

HRCT-TB demonstrated post op status of right ear with no evidence of active disease. On left side, soft tissue attenuating content was noted in middle ear cavity with erosion of ossicular chain and dehiscence of lateral semicircular canal. The alarming finding was air within anterior turn of superior semicircular canal, cochlea and vestibule (Figs. 1 and 2).

Fig. 1.

HRCT-TB (axial view) revealing air bubbles trapped in the vestibule (arrow) and cochlea (arrow head) of the left ear

Fig. 2.

HRCT-TB (coronal view) revealing air bubbles trapped in anterior turn of superior semicircular canal (arrow) dehiscent lateral semicircular canal (arrowhead) of the left ear and soft tissue density in Prussacks space (*)

The patient failed to improve by conservative management in form of bed rest, head elevation, stool softeners and avoidance of straining. On day 3 of admission, the vestibular symptoms of patient worsened and hence a left Tympanomastoid exploration was undertaken. Intraoperatively, cholesteatoma sac was seen in mastoid cavity extending to aditus ad antrum and epitympanum engulfing ossicular chain. Lateral semicircular canal (LSCC) fistula (Sanna- small, Dornhoffer grade-1) was noted. Mesotympanum examination revealed a PLF at the location of round window (Fig. 3). The defect in round window was repaired with reinforcement technique using temporalis fascia and fibrin glue. LSCC fistula was repaired by resurfacing technique utilizing fascia, bone dust and fascia in layers strengthened with fibrin glue.

Fig. 3.

Intraoperative verification of perilymphatic fistula at the location of the round window and Lateral SCC fistula

In the postoperative period, intravenous corticosteroids (Dexamethasone 0.1 mg/kg/dose thrice) and intravenous antibiotics (as per hospital antibiotic policy) were prescribed. Patient was also recommended strict bed rest. The vestibular symptoms dramatically improved by second post-op day.

At 6 weeks of follow up, the patient had no vestibular symptoms. Postoperative HRCT-TB revealed post op status of left ear with no evidence of pneumolabyrinth (Fig. 4). Pure tone audiogram was suggestive of left moderate conductive hearing loss. Patient is at present using bilateral hearing aid and shows benefit.

Fig. 4.

Repeat HRCT-TB (axial view and coronal view) revealing no evidence of pneumolabyrinth

Discussion

Pneumolabyrinth associated with a PLF is a rare clinical manifestation. It was first described by Fee in 1968 [4]. Goodhill was the first to propose implosive and explosive forces as potential causes. Implosive forces are often a post-traumatic sequel in which external forces on the oval and round window membranes, fistula ante fenestram, microfissures and Hyrtl’s fissure allow air entry into the inner ear. These can be triggered by barometric pressure changes, compression trauma to ear, Valsalva maneuver and pinched nose sneezing. Explosive forces were defined as those which exert an internal pressure by increasing cerebrospinal fluid pressure (CSF) which is transmitted to inner ear through patent cochlear aqueduct and lamina cribrosa of the internal auditory canal. These can be due to weight-lifting, straining, coughing or sneezing [2, 5, 6].

In the context of acute trauma, it can occur after stapedectomy (iatrogenic) and post cochlear implantation (iatrogenic), barotrauma or after head trauma. It can also occur as a result of chronic ear disease like Cholesteatoma and otologic malignancy with inner ear involvement [1–3].

Pneumolabyrinth usually occurs with temporal bone fracture in case of head trauma. However, pneumolabyrinth with PLF in a case of Chronic otitis media without temporal bone fracture, as in the present case, is a very rare occurrence [1–3]. In our case, the possible cause of pneumolabyrinth may be due to chronic cough (due to eosinophilia) in a pre-existing Squamous Chronic otitis media.

There is no established algorithm for diagnosis nor standard treatment protocol for pneumolabyrinth in view of the limited number of reported cases [5]. An initial conservative approach which includes bed rest, head elevation, use of stool softener and avoidance of Valsalva’s maneuver and straining; is preferred for 5 days. Exploration is reserved for progressive hearing deterioration, non-improvement of vestibular symptoms and incomplete resolution after 1 month of conservative management [4, 7]. An exploratory tympanotomy is recommended for patients who present with aggravation of vestibular symptoms and suspected perilymph leakage in the middle ear cavity [3, 4]. In this case, vestibular symptoms of patient worsened and hence we switched on to surgical management. Also, the existing squamous disease in that ear had to be treated surgically. Hence, we undertook tympanomastoid exploration.

Clinical history and physical examination are the most important tools to suspect the diagnosis. Although the diagnostic workup is relatively non-specific; early audiometry and HRCT-TB can suggest possible clues for diagnosis of pneumolabryinth [1, 3]. In our case, clinical history, symptoms, audiometry and HRCT-TB were crucial to reach to diagnosis.

There is great variability in the hearing outcome after pneumolabyrinth, and it is likely that the severity of permanent injury depends on the type and severity of cochlear trauma [4, 5]. It has been postulated that vestibular pneumolabyrinth alone appears to cause reversible or partial hearing loss [3]. Furthermore, pneumolabyrinth involving both the vestibule and the cochlea appears to have higher probability of inducing irreversible or progressive hearing loss after conservative management [4]. Early intervention leads to a more rapid resolution of vestibular symptoms and preservation of existing auditory function. Delayed (> 2 weeks) closure of perilymphatic fistula increases the possibility of permanent auditory loss [8–10].

Due to early intervention in our case, there was complete resolution of vestibular symptoms. Also, the patient had presented with mixed moderate hearing loss which post-operatively improved to purely moderate conductive hearing loss. The cochlear reserve was preserved and maintained post-operatively.

Conclusion

Pneumolabyrinth with PLF can occur in Squamous Chronic otitis media. Early audiometry and HRCT-TB in the light of clinical history and examination is crucial for diagnosis. Early surgical intervention is vital to preserve auditory function.

Funding

No funding was received to assist with the preparation of this manuscript.

Declarations

Research Involving Human Participants and/or Animals

Nil.

Informed Consent

Informed consent was taken from the patient.

Conflict of interest

Nil. The authors have no financial or non- financial interests to disclose.