**Question:** All of the following are MRI features of Mesial temporal sclerosis, except:

A. Enlarged hippocampus
B. Increased signal intensity in the hippocampus
C. Normal hippocampus
D. Reduced signal intensity in the hippocampus

**Core Concept:** Mesial temporal sclerosis (MTS) is a condition characterized by the degeneration of the hippocampus and adjacent structures in the medial temporal lobes, which leads to epilepsy. MRI (Magnetic Resonance Imaging) is a useful diagnostic tool to detect MTS.

**Why the Correct Answer is Right:** The correct answer, "Normal hippocampus" (option C), is not considered a typical MRI finding in Mesial temporal sclerosis. In contrast, MTS is typically associated with:

1. Enlarged hippocampus (option A): In some cases, the hippocampus may appear enlarged due to the atrophy of other brain structures.
2. Increased signal intensity in the hippocampus (option B): This is often seen on T2-weighted MRI sequences, which highlights areas of increased water content or inflammation.
3. Reduced signal intensity in the hippocampus (option D): This is typically observed on FLAIR sequences and represents areas of reduced water content due to neuronal loss, gliosis, or demyelination.

**Why Each Wrong Option is Incorrect:**

Option A (enlarged hippocampus) may be present in some cases, but it is not a consistent finding in MTS. In contrast, a reduced hippocampus is more typical of MTS.

Option B (increased signal intensity in the hippocampus) is often observed in MTS due to inflammation or increased water content, while reduced signal intensity in the hippocampus is a more common finding.

Option D (reduced signal intensity in the hippocampus) is a typical MRI feature of MTS, which reflects neuronal loss, gliosis, or demyelination.

**Clinical Pearl:**

MRI is a non-invasive diagnostic tool that can help identify Mesial temporal sclerosis in patients with intractable temporal lobe epilepsy. Understanding these MRI findings is crucial for accurate diagnosis and treatment planning.