## **Core Concept**
Malignant otitis externa, also known as necrotizing otitis externa, is a severe infection of the external auditory canal and temporal bone. It primarily affects diabetic or immunocompromised patients. The condition is characterized by its aggressive nature and potential for serious complications.

## **Why the Correct Answer is Right**
The correct answer involves understanding the key features of malignant otitis externa:
- **a) Caused by pseudomonas aeruginosa**: This is correct, as Pseudomonas aeruginosa is the most common pathogen responsible for malignant otitis externa.
- **c) Granulation tissue is seen in the floor of external auditory canal**: This is a hallmark of the disease, where granulation tissue is often observed at the junction of the bony and cartilaginous parts of the external auditory canal.
- **e) Gallium scan helpful for monitoring treatment**: Gallium scans can be useful in monitoring the response to treatment, as they can help assess the extent of the disease and its progression.

## **Why Each Wrong Option is Incorrect**
- **Option B: Malignancy of external auditory canal**: This option is incorrect because malignant otitis externa is not a form of cancer but a severe infectious process.
- **Option D: Radiotherapy can be given**: This option is incorrect as radiotherapy is not a standard treatment for malignant otitis externa; treatment typically involves antibiotics and supportive care.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that malignant otitis externa is often associated with diabetes mellitus and immunocompromised states. Early recognition and aggressive management are crucial to prevent serious complications, including cranial nerve palsies and further spread of infection.

## **Correct Answer: C. a, c, e**