This study looks at *how well Dexmedetomidine (DEX)*, a calming medicine, works for children getting an MRI scan. An MRI is a special picture of the brain, and it can be tricky for kids to stay still during this. DEX helps calm kids, especially those with autism or other brain development issues. Usually, kids are given a strong sleep medicine called propofol, but it needs a tube in the throat to help them breathe, which can be scary. DEX is a simpler option and is given through the nose. The study wants to see if DEX works better and is safer for kids, especially those with special needs. Kids under 18 who get DEX before an MRI can join the study, unless their medical records are not complete.

• Study Length: This study is looking back at past cases, so no extra visits are needed.
• Risks: Minimal, as DEX is already used for calming kids for different tests.
• Participation: No special treatment needed apart from usual care.