A 11-year-old boy presented with increasing left sided pain below his ear for 4 days along with high grade fever. There was some nasal congestion over the last 3 weeks due to high pollen counts. The pain has worsened despite taking decongestants and acetaminophen. The patient is a known case of allergic rhinitis and has had multiple episodes of otitis media in the past. On examination, there is tenderness and swelling of the left mastoid process and fluid behind the left temporal membrane. CT scan of the concerned region was done. Which of the following is the most likely diagnosis: -

CT shows a fluid collection in the left mastoid air cells consistent with acute mastoiditis. CT doesn't show any mass, so it is not meningioma. No history of diabetes or any destructive inflammatory process rules out mucormycosis. Acute mastoiditis Infection spreads from the mucosa, lining the mastoid air cells, to involve bony walls of the mastoid air cell system. Accompanies or follows ASOM More common in children M/C organism- beta-hemolytic streptococcus Presents with pain behind the ear, fever and ear discharge Signs are mastoid tenderness and sagging of the posterior meatal wall. Hearing loss may also accompany.