Bilateral symmetrical infratentorial subdural empyema: Delay proves detrimental.

Authors report a case of infratentorial subdural empyema, a rare complication of neglected otitis media in a child.

Introduction

Cranial subdural empyema (SDE) accounts for 15–20% of all intracranial infections.[1] A few cases of infratentorial empyema are described, and all are a consequence of neglected otitis media.[2] As pyogenic meningitis is a more common complication of otitis media, it usually masquerades the formation of SDE. Delayed establishment of the diagnosis of SDE may result in a detrimental outcome.

Case Report

A 12-year-old boy presented to surgical casualty with intermittent discharge from the left ear for the last 12 years and decreased hearing. Recently, he had developed high grade fever for a week. On examination, the patient was conscious, oriented to time and place but had a toxic appearance. Fundoscopy showed grade one papilledema and patient had bilateral sixth nerve palsies. There were no sensorimotor or cerebellar deficits. Contrast computed tomography (CT) scan revealed a hypodense extra-axial collection, located inferior to tentorium, and spread symmetrically across the midline [Figure 1a–f]. As the patient was being prepared for posterior fossa craniectomy, he became unconscious and deteriorated to decerebrating posture. Both pupils became fixed in size and nonreactive to direct light reflex. The patient was intubated and started on mechanical ventilation. Frontal horn of lateral ventricle was tapped as a last salvage measure, but proved of no benefit.

Figure 1

Contrast computed tomography scan, axial section (a) coronal section (b) shows bilaterally spread collection of purulent material along the inferior surface of the tentorium. Axial section (c) showing hydrocephalus. Bone window of computed tomography scan (d) shows opacification of left mastoid air cells indicative of chronic suppurative otitis media. Computed tomography scan, axial section (e) shows patent fourth ventricle. Contrast computed tomography scan (f) showing spread of infective pathology from mastoid to intracranial compartment

Discussion

Common intracranial complications of unsafe otitis media are pyogenic meningitis, petrositis, subperiosteal abscess, SDE, and septic thrombophlebitis. Pure infratentorial SDE is a rare occurrence. Development of clinical triad of fever, vomiting, and headache in cases of chronic suppurative otitis media (CSOM) suggest the intracranial spread of infective pathology. As this clinical triad is a harbinger of pyogenic meningitis, diagnostic cerebrospinal fluid studies are undertaken. Contrast CT scan should precede such a diagnostic test. As SDE along the tentorial surface may remain undetected in axial sections of CT scans, a lumbar puncture may precipitate fatal tonsillar herniation.[2] Therefore, coronal sections of CT scans should be performed for such cases [Figure 1b]. It is noteworthy that clinical triad of fever, vomiting, and headache is common clinical finding for both SDE and meningitis. Moreover, cerebellar signs may not be evident, as in the present case. Hence, differentiating these two complications is highly relevant in view of the entirely different management strategies for both complications.

CT scan is also relevant in ruling out associated hydrocephalus, which is a frequent associated occurrence of complicated CSOM [Figure 1c and d]. Supratentorial ventriculomegaly may result from a middle ear infection, complicated by sigmoid sinus thrombosis. However, crowding of posterior fossa structures is a major cause of hydrocephalus in CSOM associated cerebellar abscesses. As dedicated magnetic resonance imaging evaluation is not possible in such emergent clinical conditions, we speculate that abrupt cut off at the level of aqueduct is the cause of hydrocephalus and a probable explanation of sudden deterioration [Figure 1a, c and e]. The deterioration got further expedited by the caudal herniation of cerebellar tonsils into the foramen magnum. Patent fourth ventricle in CT scan is noteworthy [Figure 1e]. The absence of any localizing signs may be attributed to the symmetrical bilateral spread of SDE [Figure 1a and b]. Probably, thrombosis of sigmoid sinus added on to the insult by increasing intracranial pressure (ICP).

Surgery in the form of wide posterior fossa decompression with the evacuation of pus along with antibiotic therapy is the mainstay of treatment. Evacuation of pus reduces ICP in the infratentorial compartment and loosens the noose around aqueduct. Also, bacterial load is decreased, and caudal descent of cerebellar tonsils is hampered. Pus culture provides the exact offending organism, and appropriate antibiotics can be continued.[2] Broad spectrum antibiotics should be initiated empirically and changed according to culture report.

Conclusion

Even when CSOM is a commonly seen pediatric health problem in developing countries, a rare complication, like infratentorial SDE may be noted. As this complication warrants urgent surgical intervention, clinicians should be well-versed with the requirement of coronal scans and open surgery for this problem.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.