As you have discovered, there are some risks with cervical injections. Pain and local infection at the site of the injection is the most common. But some patients have allergic reactions and others develop deep infections at the joint.
More serious problems such as brain or spinal cord injury can occur. There are no known studies to document exactly how often this happens. Usually, case reports or small series are published. This suggests the risks are fairly minimal.
Some experts suggest that the risk of neurologic injury from cervical injections is directly linked to the surgeon's technique. The use of fluoroscopy to guide epidural injections may help decrease the risk of serious complications. Fluoroscopy is the use of a special type of real-time X-ray. It allows the surgeon to see the needle as it moves through the skin and soft tissues to the target site.
Even with careful technique, there is still the risk of headache and increased pain.