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Meningoencephalitis caused by masked mastoiditis that was diagnosed during a follow‐up in an elderly patient with diabetes mellitus: A case report

Subclinical serious infections can occur in diabetic patients. Viral encephalitis and meningitis are crucial infections even in the antibiotic era; the onset of these infections depends on the pathogen and the immunologic status of the host. We treated an elderly patient with diabetes who developed meningoencephalitis due to masked mastoiditis, which is a subclinical infection without the typical findings of mastoiditis. A 75-year-old man with left hemiparesis and aphasia had fever and disturbed consciousness. His medical history included cerebral infarction, chronic otitis media, hypertension, type 2 diabetes mellitus, chronic kidney disease and myocardial infarction. He had been previously treated with oral hypoglycemic drugs. With a reduction in body weight during the previous 7 years (from 95 to 70 kg), his glycemic control had improved. His glycosylated hemoglobin (HbA1c) level was 6.1%–6.2% (National Glycohemoglobin Standardization Program) and he had discontinued the medications. He presented to our emergency department with a Glasgow coma scale of E4V4M4 and a body temperature of 41.1 C. His height was 165 cm, weight 70.1 kg and body mass index 25.7 kg/m. On admission, his white blood cell count was 16 050 cells/μL, C-reactive protein level was 10.83 mg/dL, creatinine level 0.92 mg/dL, blood urea nitrogen 16 mg/dL, albumin level 2.8 g/dL, blood glucose level 281 mg/dL, HbA1c 6.7% and serum ammonia level was in the normal range. Arterial blood gas analysis revealed the following findings: pH 7.576; arterial partial pressure of oxygen 69.1 mmHg; partial pressure of carbon dioxide 16.9 mmHg; and HCO3 15.3 mmol/L. The cerebrospinal fluid (CSF) was turbid and white in appearance. CSF analysis showed an elevated cell count (3008 cells/μL), high protein level (616 mg/ dL) and low glucose (<1 mg/dL) level. Computed tomography (CT) scan detected liquid density in the left mastoid air cells; the skull base was partially destroyed (Fig. 1, left) and diffusionweighted magnetic resonance imaging showed hyperintense lesions with a fluid–fluid level in the bilateral lateral ventricles and the left mastoid (Fig. 1, right). No otorrhea was observed with normal tympanic membrane findings. Thus, he was diagnosed with meningoencephalitis caused by masked mastoiditis. Antibiotics (meropenem and vancomycin), antiviral therapy (acyclovir) and steroid treatment were initiated. The doses were determined as per the clinical practice guideline 2014 for bacterial meningitis (Fig. S1). Penicillin-sensitive Streptococcus pneumoniae (PSSP) was then detected in his blood and CSF culture, and the CSF viral polymerase chain reaction test confirmed the absence of herpes and varicella-zoster virus. PSSP was sensitive to β-lactam antibiotics. Ceftriaxone therapy was continued with weekly CSF analysis for a period of 6 weeks. The conservative therapy was continued and physical, blood and CSF findings improved, resulting in remission (Fig. S1). After 4 months, he developed pneumonia and was readmitted. His CSF findings were normal, and recurrent meningoencephalitis was not