There are some sensory nerves that can be stretched with the position your wife holds her head to bring on the symptoms. This may indicate a mild neuropathy (temporary inflammation of this nerve). If the symptoms really disturb her, it may be that a physical therapy program with some ultrasound may be helpful. You would need a physician to diagnose and write a script for therapy.
Multiple Sclerosis normally does not present with the symptoms you describe. This does sound like a mechanical nerve disorder.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.