Surgical corridors for congenital aural atresia with otogenic cerebellar abscess and lateral sinus thrombosis

Abstract

The following is a case report of an adolescent with mental retardation who had congenital aural atresia with contralateral congenital facial palsy. She developed multiple intracranial complications (cerebellar abscess and lateral sinus thrombosis) due to cholesteatoma. We managed her in a multidisciplinary approach. This report discusses case management, emphasising the meticulous intraoperative steps taken in identifying the landmarks and precautions adopted to avoid postoperative facial palsy and other complications.

Background

Congenital anomalies of ear results from failure of development of branchial arches ranging from various degrees of microtia to anotia (complete absence of external ear). The degree of middle ear deformities depends on auricular malformation, although the inner ear anomalies are relatively rare in these patients. When surgery is contemplated in patients with malformations of the ear, difficulty in identifying landmarks corresponds to the degree of malformations present. This case report attempts to elucidate the importance of landmarks in a patient with aural atresia planned for surgery.

Case presentation

An 18-year-old mentally challenged, deaf-mute girl presented to the emergency department with symptoms of fever, vomiting and irritability for 1 month. General examination showed other features like the depressed nasal bridge, congenital right facial palsy, and cleft lip and palate (which were operated in the childhood) with prognathism (figure 1). Parents gave her clinical history, and her father signed the consent for surgery as her intellectual status was low. There was bilateral congenital aural atresia (CAA) (grade 3 microtia Jahrsdoerfer staging) with slit-like external auditory canal (EAC) on examination of the external ear. A tender fluctuant swelling of 2×2 cm was present around the left ear tag (figure 2A, B). The rest of the pinna and ear canal were rudimentary. We could not visualise the tympanic membrane through slit-like EAC. The patient swayed to the left on Romberg’s test, and Cerebellar signs were present. However, there was no nystagmus or evidence of papilloedema.

Figure 1.

Bilateral anotia with right-sided facial palsy.

Figure 2.

(A, B) Bilateral anotia with subperiosteal abscess over left mastoid.

Investigations

Preoperative pure tone audiometry showed bilateral profound sensorineural hearing loss (right and left >90 dB HL).

Contrast-enhanced CT (CECT) of the brain with high-resolution CT (HRCT) of the temporal bone showed a well-defined hypodense lesion with thin smooth peripheral enhancement and surrounding oedema, measuring 3.3×3.5 cm in the left cerebellar hemisphere suggestive of an abscess (figure 3A, B). Filling defect in the sigmoid sinus was suggestive of lateral sinus thrombosis. Ossicular remnants were there with opacification of left middle ear and mastoid cavity with destruction of mastoid air cells; the tympanic segment of the facial nerve appeared to be dehiscent (figure 4A, B). The mastoid showed signs of mastoiditis with outer cortical erosion and subperiosteal abscess (figure 4C, D). As we considered an emergency surgery after the multidisciplinary meet and, as the diagnosis was certain with CECT, other investigations like MRI and magnetic resonance venography were not considered.

Figure 3.

(A and B) CT scan showing left-sided cerebellar abscess, lateral sinus thrombosis, mastoiditis and subperiosteal abscess.

Figure 4.

Preoperative high-resolution CT temporal bone showing ossicles remnants (black arrow) and the lateral semicircular canal (red arrow) (A); facial nerve (yellow arrow) (B); opacification of the mastoid cavity (yellow dot) with outer cortical erosion (brown arrow) and subperiosteal abscess (white dot) (C and D).

Differential diagnosis

Based on the history and clinical examination, our differential diagnosis was congenital cholesteatoma with mastoiditis with mastoid abscess, meningitis and brain abscess. In conjunction with radiological findings, our final diagnosis was left mastoid abscess with cerebellar abscess with lateral sinus thrombosis.

Treatment

The decision to perform emergency cerebellar abscess drainage via a retro mastoid suboccipital craniotomy followed by a radical mastoidectomy was made by the multidisciplinary team from neurosurgery, otology and radiology.

The patient was started empirically on intravenous antibiotics, ceftriaxone, amikacin and metronidazole, as per institution antibiotic guidelines.

Surgical technique

We positioned the patient in a ‘park bench’ position with the left side up. The head was flexed laterally for 20° and rotated towards the floor so that the region of the mastoid was at the highest point using a Mayfield 3 pin head clamp (figure 5A). The ipsilateral shoulder was depressed and strapped. We made the craniotomy incision 4 cm posteriorly to the aural tag. The soft tissues were dissected and suboccipital craniotomy performed. We took meticulous care not to elevate the periosteum close to the proposed mastoid antrum to avoid communication with the craniotomy defect and future mastoidectomy cavity. Oedematous brain tissue with dilated blood vessels was visualised (figure 6A). Cerebellar abscess drained and around 30 mL of frank pus drained out and sent for culture sensitivity (figure 6B). The capsule of the abscess cavity was excised with some remnants over the brainstem left undisturbed (figure 6C). The dural layer was closed primarily and craniotomy defect and wound were closed in layers. For performing radical mastoidectomy, we made a long curvilinear incision just posterior to the aural tag. Care was taken not to elevate the periosteum more posteriorly to avoid communication with the craniotomy site. As the external ear canal and usual landmarks were deformed, an attempt was first made to identify the zygomatic process of the temporal bone. The periosteum was elevated posteriorly from the zygomatic process. The soft tissue filling the external ear canal was removed. Based on these two landmarks (the zygomatic process of temporal bone and external ear canal) mastoidectomy was performed. Cholesteatoma in the attic, aditus and sclerosed mastoid antrum was removed entirely (figure 6D). There were ossicular remnants which were removed. We found the tympanic segment of the facial nerve lying barely without overlying bone and slipping downwards into the middle ear; the vertical part of the facial nerve was found to be intact. With blunt dissection, we separated the disease from the underlying facial nerve. Using a diamond burr, the bone over the sigmoid sinus was thinned out. We took a 20 G needle to aspirate the blood from the sigmoid sinus. As we could aspirate clear blood, we do not attempt to manipulate the sigmoid sinus. We blocked the Eustachian tube with remnant deformed external ear cartilage, and we obliterated the middle ear and mastoid cavity with fat harvested from the thigh. Finally, a ‘Cul-de-sac’ closure of the atretic ear canal was done before closing the soft tissue and skin in layers (figure 5B).

Figure 5.

Left craniotomy incision marked with head in park bench position (A); immediate postoperative picture showing both incisions (B).

Figure 6.

Intraoperative image showing oedematous brain tissue with dilated blood vessels (A); abscess cavity (pink arrow) with capsule (red asterisk) (B and C); mastoid cavity with granulation tissue in mastoid, aditus and attic (D) (blue arrow).

The postoperative course in the hospital was uneventful. Purulent discharge from the brain abscess on bacteriological culture showed a multidrug-resistant Neisseria flava sensitive to meropenem. She received 6 weeks of intravenous meropenem. At the end of 6 weeks, the cerebellar signs had completely resolved.

Outcome and follow-up

The patient has left intact facial nerve function and a CT scan of the brain and temporal bone after 6 weeks shows no evidence of residual disease in the brain and mastoid cavity (figure 7A–C).

Figure 7.

At 6 weeks of the postoperative period, a CT scan of the brain shows no evidence of residual abscess (A); CT temporal bone showing mastoid cavity (black dot) with suboccipital craniotomy site (orange arrow) (B and C).

Discussion

Most literature on otogenic brain abscesses has found temporal lobe abscesses to be the most common abscess followed by the cerebellar abscess.^{1 2} Infectious thrombophlebitis of the sigmoid sinus is also a known complication of complicated chronic otitis media and if left untreated has a high mortality rate.¹

It has been noted that the incidence of otogenic brain abscess in acute and chronic otitis media was 0.5% and 3%, respectively.^{3 4} Literature review revealed extensive data on cerebellar abscess with chronic otitis media in anatomically normal ears^{5 6} and cholesteatoma involving the middle ear cleft in microtic ears.⁷ However, cerebellar abscess in a deformed ear and its management has not been mentioned so far. Cholesteatoma in CAA may remain undiagnosed that may result in intra temporal and intracranial complications.⁸ This report highlights the management of a mentally challenged patient with bilateral anotia, right congenital facial palsy with left otogenic cerebellar abscess, and sigmoid sinus thrombophlebitis.

Two pathophysiological mechanisms have been described for otogenic brain abscess formation. One is the contiguous focus of infection like otitis media and the other is haematogenous spread from a distant infectious focus.⁹ In the present case, as there was no bone erosion and direct continuity noted in the imaging, venous thrombophlebitis was the likely pathophysiological mechanism for both cerebellar abscess and sigmoid sinus thrombosis as mentioned by Nissen.¹⁰

HRCT is necessary for preoperative evaluation and surgical planning in these cases.⁷ Although MRI gives better soft tissue details and the extent of intracranial disease, in an emergency setting CECT scan gives quick information.^{5 7}

The management of otogenic cerebellar abscess has been controversial. A few decades ago, aspiration of brain abscess with high doses of antibiotics was recommended.¹¹ However, recent data have found survival benefits in early neurosurgical excision of the abscess.¹² Single-stage surgery with complete removal of abscess and mastoidectomy when possible gives excellent results.^{6 13} However, a review of publications about a single-stage surgery has no mention of intraoperative steps adopted to optimise results. As the anterior limit of the craniotomy for cerebellar abscess drainage is the mastoid cavity, there is always a chance of communication between the infectious middle ear cleft (mastoid antrum) with the meninges which can lead to perioperative Cerebro Spinal Fluid (CSF) otorrhoea and postoperative meningitis. Hence, scrupulous intraoperative attention towards this entity prevents perioperative and postoperative complications. In the present case, a bridge of soft tissue and occipital bone was left between these distinct operative cavities (mastoid cavity and craniotomy site).

Performing mastoidectomy in an atretic ear is another challenge. The first step to be taken is to identify the zygomatic process of mastoid bone which is a constant landmark. The diseased and inflamed soft tissue in the atretic canal has to be excised and the external ear canal forms the second landmark. ‘Inside out’ mastoid drilling needs to be considered in these cases as there will be sclerotic mastoid cavities in most of the cases. Radical mastoidectomy with ‘Cul-de-sac’ closure of the external canal will reduce postoperative cavity problems.

The facial nerve has been reported to be more laterally and anteriorly displaced in microtia/anotia patients. The tympanic segment is more often involved with malformation than the labyrinthine segment than the mastoid segment.¹⁴ The ventral displacement can be severe in higher grades of microtia rarely resulting in the exit point of the nerve being at the temporomandibular joint itself rather than at the stylomastoid foramen.¹⁴ In the present patient, the tympanic segment was dehiscent along its entire course and displaced ventrally into the middle ear space. This is similar to other reports in the literature. The anticipation of an anomalous course and natural dehiscence most commonly in the tympanic segment is important to avoid inadvertent injury to the nerve during mastoidectomy for patients with anotia. Finally, even though the variations of the oval, round window and inner ear are less commonly seen in aural atresia due to the different embryological origins, these have to be kept in mind to avoid surgical surprises.

Long-term culture-sensitive antibiotics with postoperative care are also important in speedy recovery.

Patient’s perspective.

Patient’s mother: My daughter is happy without any pain, ear discharge and able to sleep happily. We are happy with the treatment and care are given to my daughter.

Learning points.

• Congenital cholesteatoma in external auditory canal atresia occurs due to the entrapment of epithelium medial or lateral to the atretic plate and complications rates are more in the medial epithelial entrapment.

• Since embryological development of external ear is independent of middle ear, complications of middle ear disease including intracranial complications can occur even if the external ear is rudimentary or absent.

• The exit of the facial nerve can be as anterior through the temporomandibular joint.

• The presentations with complications are due to coexisting congenital cholesteatoma, poor aeration of mastoid and middle ear, and entrapped epithelium.

• Better the development of the auricle, the better the development of the middle ear and mastoid.