My friend experienced numbness on the top part of her brain on and off at a 10-20 minutes interval. why is it?

Scalp numbness: It's the scalp feeling numbness; the brain is insensate to pain. Some things that can cause abnormal scalp sensation include chronic migraine, hyperventilation, panic attacks, prior head trauma or surgery. Red flags for something bad include nerve pain or numbness in other parts of the body, seizures, altered level of consciousness, skin breaks where she is numb, or severe headaches. Good luck!