Transient babinski & hyper reflex

I took my son (11 yrs) to the doctor with back pain (just arrived when sitting in his desk at school. Sais his leg did not want to stretch for the morning. When this went away, the back pain started. No injury that we can think of, but he was active with high jump, swimming and tennis). A very strong patella (LHS) reflex presented, and he also had a positive Babinski reflex. He went for an emergency MRI and brain scan (has a history of meningitis) and blood tests. EVERYTHING was normal. Then, five hours later, the reflexes were normal too. He still gets the back pain, but it seems to be muscular. Should I be worried? What should I look out for?