Please bear in mind that I have no medical degree and am not a medical professional. The advice given is that of a Yoga Teacher. Always consult with your physician for a professional opinion.
Firstly, a student, who has such a serious ailment, should get their doctor’s permission before starting to practice with a teacher. If possible, get a doctor’s referral to a particular Yoga teacher, who is more knowledgeable in this area. Many doctors often network with local teachers and ashrams, for the benefit of their patients.
The methods, personalities, knowledge, and patience, of yoga instructors who are teaching, will vary. Some of the poses that I would not recommend would be – Sirsasana (Headstand); Sarvangasana (Shoulderstand); Halasana (Plow Posture); or any other posture that could cause severe compression on the cervical vertebrae (neck). Also, your doctor should be made aware of any movements and positions, such as, chin locks, neck rolls, and fingers clasped behind the neck.
You may find it is important not to do any exercises that hurt, even a tiny bit. Pain is your body’s way of telling you, “not to do that.” The exercises that will help you the most are ones where you will feel a gentle stretch. If you don’t feel a gentle stretch or strain, I suspect the poses are not doing much for you.
If they hurt at all, stop doing them immediately. I’ve never seen any benefit from doing any asana, or any treatment of any kind (chiropractic, massage, physical therapy, etc.), that hurts.
Learning how to practice asanas for a serious condition, such as mentioned above, should be practiced under maximum supervision of a competent Yoga teacher. I would suggest at least one private lesson before trying a group class. A teacher may suggest, at least, a few private Yoga training sessions so that the student understands all the safety guidelines.
As educational as videos are, they are no substitution for the guidance of a competent Yoga instructor.