Only about 5% of our patients suffer from side effects after stem cell injections. Side effects are generally minor and appear right after injection. Side effects can include headache, fever, nausea, dizziness, vomiting, pain in the legs or back pain. Side effects are temporary and fade away quickly in most cases. It is important to note that in most cases side effects are not caused by the stem cells but by the intrathecal injection procedure itself.