By Michiel Tak in Science For ME.
CCI/AAI has little in common with ME/CFS
Three ME/CFS patients, Jeff, Jennifer, and Matt, have reported spectacular improvements of their ME/CFS symptoms following surgical interventions for craniocervical instability (CCI) and atlantoaxial instability (AAI).
CCI refers to increased mobility and instability of the craniocervical junction, the transition between the spine and the skull. It normally develops as a result of physical trauma such as a car accident, an inflammation disease such as rheumatoid arthritis or a congenital disorder such as Down syndrome.  The main symptoms of CCI consist of severe neck pain,  and neurological abnormalities  that are quite different from the characteristic ME/CFS symptoms. Young et al. for example describe a case of CCI with chronic neck pain, headache, left-sided facial pain, and numbness. Another case example had progressive worsening of neck pain and frequent falls, which were attributed to balance issues.  The case report by Botelho et al. describes a man with insensibility to pain in the left hemithorax and paresis of the hands.  Kukrejo et al. report on 49 cases that underwent fusion surgery.
The most common presenting symptoms were gait instability, motor weakness, numbness, neck pain and dysphagia (difficulties swallowing).  More severe forms of cervical cord compression and trauma to the spinal cord or the brainstem do not result in ME/CFS symptoms but in respiratory distress, pain, cranial nerve dysfunction, paresis and paralysis and in rare cases, sudden death.