Okay, let's tackle this question about MRI features of mesial temporal sclerosis. First, I need to recall what mesial temporal sclerosis (MTS) is. MTS is a common cause of temporal lobe epilepsy, characterized by hippocampal atrophy and gliosis. The MRI features would typically show findings in the hippocampus.

The question asks which is NOT an MRI feature. So, the correct answer is the option that doesn't fit the usual findings. Let me think about the typical MRI signs. Common features include hippocampal atrophy, increased T2 signal in the hippocampus, and sometimes a "mushroom-shaped" hippocampus due to atrophy. Also, there might be reduced volume and abnormal signal in the parahippocampal region.

Now, the distractors would be incorrect features. For example, if one of the options mentions a normal hippocampal volume, that's wrong. Another might mention a T1 hyperintensity, but MTS usually shows T2 hyperintensity. Also, if an option states that the signal is normal, that's incorrect. Another possible wrong answer could be a feature of another condition, like a tumor or abscess.

I need to structure the explanation. Start with the core concept: MTS is associated with hippocampal atrophy and gliosis, which show up on MRI as T2 hyperintensity and volume loss. Then explain why the correct answer is right by detailing the typical MRI findings. Then go through each wrong option and explain why they don't fit. Finally, a clinical pearl to remember the key MRI features. Make sure each section is concise and uses medical terms correctly. Check for any possible mistakes in the reasoning.

**Core Concept**
Mesial temporal sclerosis (MTS) is characterized by hippocampal atrophy and gliosis, commonly seen in temporal lobe epilepsy. MRI features include hippocampal volume loss, increased T2 signal, and abnormal hippocampal shape (e.g., "mushroom-shaped").

**Why the Correct Answer is Right**
The correct answer is the option describing a normal hippocampal volume or signal. MTS typically shows hippocampal atrophy (volume reduction), T2/FLAIR hyperintensity due to gliosis, and structural abnormalities. Absence of these findings (e.g., normal volume or signal) would exclude MTS on MRI.

**Why Each Wrong Option is Incorrect**
**Option A:** *T2 hyperintensity in the hippocampus* is a hallmark of MTS due to gliosis and inflammation.
**Option B:** *Hippocampal atrophy* is a defining feature of MTS.
**Option C:** *Parahippocampal gyral atrophy* often accompanies MTS but is not diagnostic alone.
**Option D:** *Normal hippocampal signal* contradicts MTS pathology, which always shows abnormal signal.

**Clinical Pearl / High-Yield Fact**
Remember the "3 A’s" of MTS on MRI: **Atrophy** (volume loss), **Abnormal signal** (T2/FLAIR hyperintensity), and **Abnormal shape** (e.g., "mushroom-shaped" hippocampus). Absence of any of these suggests an alternative diagnosis.

**Correct Answer: D. Normal hippocampal signal**

✓ Correct Answer: C. Blurring of Grey white matter junction of ipsilateral temporal lobe