Teaching Case

A 24-year-old male patient presented at the emergency department with headache, high-grade fever and sensory disturbance. He had a history of deafness and otorrhoea.

NECT temporal bone shows a soft-tissue mass that affects the right middle ear with ossicular chain erosion and bone defect of the ipsilateral tegmen tympani (Fig. 1).

CECT brain shows a well-defined hypodense focal lesion in the right temporal lobe with peripheral ring enhancing and mass effect. Moreover, affection of ipsilateral tentorium (Fig. 2).

MRI brain shows an internal content hypointense on T1WI, markedly hyperintense on T2WI and mildly hyperintense to CSF on FLAIR (Fig. 3). Gd-enhanced T1WI shows smooth, complete ring enhancing with extension to ipsilateral tentorium (Fig. 4). T2* GRE shows the dual rim sign (Fig. 3). DWI with b-value 1000 s/mm² demonstrates diffusion restriction (Fig. 5).

In the last 20 years, the incidence of intracranial complications of chronic otitis media has decreased due to the early use of antibiotics; however, the presence of cholesteatoma is an important risk factor for them. The otogenic brain abscess accounts for 25% of brain abscesses in children, whereas in adults it accounts for > 50%. Moreover, it occurs predominantly in men [1].

The cholesteatoma is a non-neoplastic lesion in the temporal bone composed of desquamated keratinising stratified squamous epithelium that form a mass. The cholesteatomas are classified as either congenital or acquired. The acquired cholesteatoma can be primary (80% of all middle ear cholesteatomas) or secondary [2].

The mechanics of spread are either through a bone defect on the tegmen tympani or by the dissemination of an infected blood clot within an emissary vein of the skull to a venous sinus. The otogenic brain abscess most frequently affects the adjacent medial segment of the temporal lobe and lateral lobe of the cerebellum [1].

The clinical presentation is variable. The most frequent symptoms are headache, nausea, vomiting and deafness. Other signs and symptoms include sensory disturbance, seizures and neurological focalisation. If it affects the cerebellum, it can present dysmetria, dysdiadochokinesia and spontaneous nystagmus (cerebellar signs) [3].

The abscess development has four stages: 1) early cerebritis; 2) late cerebritis; 3) early capsule and 4) late capsule. On MRI, the cerebritis stages show low signal on T1WI and high signal on T2WI with patchy enhancement. When the abscess capsule forms, it shows a hyperintense center, hypointense border and hyperintense vasogenic oedema on T2WI with well-defined ring enhancement. Central high signal on DWI with low ADC is present [4]. Another finding on MRI is the dual rim sign (a hyperintense line located inside the low intensity rim) that can be seen on T2 * GRE and SWI.

CT is the imaging technique of choice to diagnose cholesteatoma in patients in whom it is clinically suspected. The findings associated with cholesteatoma include an expansile soft-tissue mass lateral in Prussak space with extension into lateral epitympanic recess. In addition, destruction in bones like ossicles, tegmen tympani and semicircular canals is seen, among others findings [4].

The pillars of the treatment are drainage of the abscess, eradication of the primary otogenic focus and prevention of recurrence of the abscess [1].

The patient was subjected to radical mastoidectomy. The diagnostic of cholesteatoma was made surgically.