Abstract
Background: Diabetes mellitus (DM) is a systemic metabolic disorder that possesses macro- and microangiopathic consequences. Studies have demonstrated that a relationship exists between sensorineural hearing loss (SNHL) and DM, particularly in patients of older age, longer disease duration, and uncontrolled DM. The pathophysiology of DM related hearing loss is poorly understood, however proposed mechanisms include ischemia, fibrosis, demyelination, and atrophy of the eighth cranial nerve. We however, present a case of acute, transient sensorineural hearing loss in the setting of diabetic ketoacidosis that resolved with blood glucose control.
Clinical Case: A 34-year-old male with type 2 diabetes mellitus (A1c 6.5% -diagnosed 6 months prior), hypertension, hyperlipidemia, and morbid obesity presented with shortness of breath and acute hearing loss without tinnitus, after being treated for pneumonia and otitis media with a course of levofloxacin for 7 days. On presentation, patient was tachypneic and tachycardic. Physical examination was significant for mild erythema of the right tympanic membrane without bulging, fluid level, mastoid tenderness, or discharge. Laboratory values were significant for hyperglycemia with blood glucose of 628 mg/dL(n 70–99 mg/dL), A1c 15.9% (n 4.8–5.6%), bicarbonate 8 mmol/L (21–31 mmol/L), anion gap 37 mmol/L (9–16 mmol/L), beta-hydroxybutyrate 11.7 mmol/L (0.02–0.27 mmol/L). Venous gas was suggestive of metabolic acidosis, urinalysis was positive for moderate ketones and glucose >500 mg/dL. The patient was diagnosed with diabetic ketoacidosis and was started on an insulin drip. An audiogram revealed profound bilateral sensorineural hearing loss. A Computerized tomography (CT) scan of the bilateral temporal bones was negative for abnormalities, and a magnetic resonance imaging (MRI) of the brain was negative for morphologic abnormalities of 7th and 8th cranial nerves. Infectious and rheumatologic etiologies were excluded with normal syphilis FTA-ABs, Lyme PCR, Rheumatoid factor, ANCA, and ANA. The patient received one dose of empiric prednisone. His hearing improved after 2 days with normalization of blood glucose to a range of 100–200 mg/dL. A repeat audiogram and auditory brainstem response showed significant improvement with normal bilateral hearing.
Discussion: SNHL in DM typically presents in a gradual progression with bilateral involvement, affecting higher frequencies. In patients with DM, studies show that chronicity (greater than 10 years) is strongly associated with SNHL. Other variables include older age and HbA1c greater than 8%. This is the first case to demonstrate acute bilateral SNHL, associated with uncontrolled type 2 diabetes mellitus, which resolved after blood glucose control. In the appropriate context, clinicians should consider significant hyperglycemia as a possible etiology of acute hearing loss.
FEATURES OF PATHOGENESIS OF SENSORINEURAL HEARING LOSS IN PATIENTS WITH TYPE 2 DIABETES MELLITUS
