First, ear discharge could be due to an ear infection. But the presence of diplopia (double vision) and fever suggests something more serious. Diplopia is a red flag symptom because it can indicate cranial nerve involvement. The cranial nerves related to eye movement are III, IV, and VI. So, if there's an infection affecting these nerves, it could lead to diplopia.

Now, considering the combination of ear infection and cranial nerve palsy, I'm thinking about complications of otitis media. Acute otitis media can spread to adjacent structures. If the infection spreads to the mastoid or the petrous apex, it could cause a petrous apicitis, which is a type of osteomyelitis. This can lead to cranial nerve palsies, especially the abducens nerve (CN VI) which is involved in lateral eye movement. So petrous apicitis might be the culprit here. Alternatively, a brain abscess could form, but that usually presents with more focal neurological deficits and maybe other signs like headache or altered mental status. Another possibility is a cerebellar abscess, but again, the diplopia in this case seems more likely due to cranial nerve involvement rather than a mass effect.

Let me check the options. The correct answer is petrous apicitis. The other options might include something like mastoiditis, which is more about ear pain and swelling, or a brain abscess. But petrous apicitis specifically involves the petrous part of the temporal bone, leading to cranial nerve palsies. The key here is the combination of ear discharge, fever, and diplopia pointing towards an infection that's spread to affect the cranial nerves.

**Core Concept**
This question tests the recognition of **complications of otitis media**, particularly **petrous apicitis** (Gradenigo syndrome), which involves cranial nerve palsies due to osteomyelitis of the petrous temporal bone. Key features include **tria of otitis media, abducens nerve palsy (CN VI), and ophthalmoplegia**.

**Why the Correct Answer is Right**
Petrous apicitis is a rare but severe complication of **acute otitis media or mastoiditis**. The infection spreads to the **petrous apex** (part of the temporal bone), leading to **osteomyelitis** and direct injury to **CN VI (abducens nerve)**, causing **diplopia** due to lateral rectus muscle paralysis. Fever and ear discharge indicate an active infection. The classic triad includes **otalgia, abducens palsy, and ophthalmoplegia**, often with **facial nerve involvement (CN VII)**.

**Why Each Wrong Option is Incorrect**
**Option A:** Mastoiditis typically presents with **ear swelling, redness, and postauricular pain** without cranial nerve palsies.
**Option B:** Brain abscess may cause focal neurological deficits but usually lacks the **specific abducens palsy and ear discharge** seen here.
**Option C:** Cerebellar abscess would present with **ataxia, headache, and altered mental status**, not diplopia from CN VI