**Question:** A 25-year-old woman suffering from bilateral hearing loss for 6 years which became profound with pregnancy. On tympanogram, which of the following curve is obtained?

A. Type A
B. Type B
C. Type C
D. Type D

**Core Concept:** Tympanograms are an audiometric test used to assess the function of the middle ear. They are obtained by inflating a small balloon in the ear canal and measuring the pressure change in relation to the acoustic reflex. Types of tympanograms are based on the shape and position of the air-bone gap (ABG) and the mobility of the tympanic membrane (TM) in response to air and bone conduction stimuli.

**Why the Correct Answer is Right:** In this case, the patient's bilateral hearing loss became profound during pregnancy. This indicates a likely immune-mediated inner ear damage, which is more likely to occur in Type C tympanogram. Type C tympanogram is characterized by a significant air-bone gap at low frequencies, suggesting middle ear pathology, and a relatively flat ABG at high frequencies, indicating inner ear pathology.

**Why Each Wrong Option is Incorrect:**

**Option A (Type A)**: Type A tympanogram is seen in normal middle ear function and a minimal or absent air-bone gap at all frequencies. In this case, the ABG would not be significant, making it an incorrect choice.

**Option B (Type B)**: Type B tympanogram represents a conductive hearing loss due to middle ear pathology, presenting with a significant air-bone gap at all frequencies. In this case, the ABG would be significant at all frequencies, making it an incorrect choice.

**Option D (Type D)**: Type D tympanogram is seen in a mixed hearing loss, indicating a combination of middle ear and inner ear pathology. In this case, the ABG would be significant at low frequencies and minimal at high frequencies, making it an incorrect choice.

**Core Concept:** Tympanograms help in distinguishing between conductive and sensorineural hearing loss, guiding the clinician in determining the cause of hearing loss and directing appropriate diagnostic investigations and management strategies.

**Clinical Pearl:** Pregnancy-induced sudden hearing loss should raise suspicion of an immune-mediated inner ear disease, prompting further evaluation for autoimmune disorders, often involving immunoglobulin G4 (IgG4) related disease or autoimmune neuropathy.