Abstract
Skull base lesions are enigmatic and often behave unpredictably. This report is about a case of skull base osteomyelitis as a complication of malignant otitis externa and how one can investigate such skull base lesions early. A 72-year-old known diabetic male patient with a previous history of recurrent otitis externa, presented with symptoms similar to syncopal attack to the emergency room.During a routine ENT consultation, a mass in the nasopharynx was discovered. Immediately,multimodality imaging was requested and it confirmed a soft destructive dense tissue mass in the skull contiguous with the posterior nasopharynx. Trans -nasal biopsy was inconclusive. However, to determine the exact nature of the lesion HRCT Temporal bone and T2 weighted Gadolinium MRI imaging was done. That confirmed our diagnosis of Malignant Otitis Externa. The lesion was controlled by broad spectrum IV antibiotics in the initial 3 weeks followed by oral antibiotics for several weeks to completely eradicate the lesion.
Case report
A 72-year-old male patient, with insulin dependent diabetes mellitus, chronic kidney disease and ischemic heart disease presented to the Emergency with chief complaints of severe headache. An ENT reference was opined, clinical examination with nasopharyngoscopy revealed a mass in the nasopharynx near to fossa of Rosenmüller. This patient had a past history of recurrent otitis externa which was managed conservatively in the outpatient clinic. In view of the recent headache, a CT head was requested, this confirmed a soft tissue dense mass of skull contiguous with the posterior nasopharynx, approximately measuring 3.6 × 3.5 cm involving the pharyngeal mucosal space, left parapharyngeal space and also eroding the left basioccipital and mastoid ( Fig. 1 ). As a protocol, in view of a suspected nasopharyngeal malignancy involving skull base, the patient was referred to Head and Neck team for Trans -nasal biopsy. The biopsy was done to access the histopathology of the lesion but the results were inconclusive.
The patient was referred back to ENT to reassess the lesion. However, due to COVID restrictions the patient lost the follow up. And around 3 months later, the patient was re-admitted to our tertiary care center due to headache, feeling of imbalance, and active left ear discharge and severe ear pain. Under microscopic examination, granulation was seen in the floor of external auditory canal. Tympanic membrane could not be visualized due to edematous canal and active discharge.T2 weighted Gadolinium MRI was performed for further investigation and it showed irregular marginated and infiltrative T2 hypointense mass lesion with necrotic component, likely arising from the nasopharynx (epicenter from left side) causing permeative bone destruction of clivus, left mastoid and inner ear bony labyrinth and floor of sphenoid sinus. This lesion measured approximately 5.6 x 3.9 × 4.2 cm. Inferiorly, the mass lesion extended up to the lower end of C2 in prevertebral region [ ]. Anteriorly, the mass lesion was infiltrating the sphenopalatine fossa and pterygopalatine fossa region with indistinct fat planes in the pterygoid muscles. There was also infiltration of left jugular foramina and encasement of the distal most cervical left jugular vein with active infiltration of round and oval foramina (likely perineural spread). Subtle leptomeningeal enhancement was noted in left temporal region [ , ] ( Fig. 2 ). A repeated nasopharyngeal biopsy was done due to the continued concern that on imaging this lesion suspected to be a nasopharyngeal malignancy infiltrating to skull base. The repeated biopsy demonstrated only a chronic inflammatory infiltrate and was inconclusive. In the blood routine, C- Reactive Protein(CRP), Erythrocyte sedimentation rate(ESR) and total leukocyte count(TLC) were found elevated confirming the inflammatory process. Serum angiotensin converting enzyme (ACE), anti-nuclear antibodies (ANA), rheumatoid factor (RF) and anti-neutrophilic cytoplasmic antibodies (ANCA) levels were done to rule out connective tissue disorders and vasculitis and these were all within the normal limits. Neurosurgery opinion was sought and they advised nil active intervention [ ]. Subsequently, cultures grew Pseudomonas species and a methicillin-resistant Staphylococcus aureus (MRSA). Simultaneously, HRCT Temporal bone was done and this revealed erosion of the left basiocciput and the mastoid with contiguous soft tissue opacification of the left middle ear cavity and soft tissue opacification involving the bony part of external auditory canal [ ]. However, floor of the external auditory canal was found intact without any erosion ( Fig. 3 ). All of the above, lead to a confirmed clinical diagnosis of Malignant Otitis Externa with skull base osteomyelitis.
