**Core Concept**
Magnetic Resonance Spectroscopy (MRS) is a non-invasive imaging technique that provides information on the metabolic composition of tissues. N-Acetylaspartate (NAA) is an amino acid found predominantly in neurons, and its peak is often used as a marker of neuronal integrity.

**Why the Correct Answer is Right**
NAA peak is typically seen in conditions where there is neuronal damage or loss, such as in cerebral ischemia, trauma, or neurodegenerative diseases. This is because NAA is broken down into NAA and acetate in the presence of neuronal damage, leading to an increase in the NAA peak on MRS. In conditions where there is neuronal damage, such as **Option C: Ischemic Stroke**, the NAA peak is seen on MRS due to the breakdown of NAA in the damaged neurons.

**Why Each Wrong Option is Incorrect**
**Option A:** In Traumatic Brain Injury (TBI), the NAA peak may be decreased due to neuronal loss, but it is not typically seen as a peak.
**Option B:** In Multiple Sclerosis (MS), the NAA peak may be decreased due to demyelination and axonal loss, but it is not typically seen as a peak.
**Option D:** In Normal Brain, the NAA peak is typically present, but it is not seen as a peak in the context of this question.

**Clinical Pearl / High-Yield Fact**
The NAA peak on MRS is a sensitive marker of neuronal damage, and its presence can be used to monitor the progression of neurological diseases.

**Correct Answer: C. Ischemic Stroke. NAA peak is seen on MRS in conditions where there is neuronal damage, such as in ischemic stroke.**