Audiogram — Mondini Inner Ear Malformation (Incomplete Partition Type II)

A 7-year-old boy presents with bilateral progressive sensorineural hearing loss detected on routine school screening. His parents report a sudden worsening of hearing 2 weeks after a minor head injury during play. On examination, he has a firm, non-tender thyroid mass. Audiometry shows bilateral high-frequency predominant SNHL with an air-bone gap at low frequencies. High-resolution CT temporal bone reveals a cystic apex with only 1.5 cochlear turns, dilated vestibule, and enlarged vestibular aqueduct (midpoint width 2.2 mm). The audiogram pattern marked **A** in the diagram is consistent with which of the following diagnoses?