Vertebral column

The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordates has been replaced by a segmented series of bone: vertebrae separated by intervertebral discs. The vertebral column houses the spinal canal, a cavity that encloses and protects the spinal cord.

Chiari I malformation
A Chiari malformation (CM) is a structural defect of the base of the skull and the cerebellum, characterized by a downward displacement of one or both cerebellar tonsils through the foramen magnum (the opening at the base of the skull). This can sometimes lead to non-communicating hydrocephalus as a result of obstruction of cerebrospinal fluid (CSF) outflow.

While many clinical criteria consider Chiari malformation to be a differential diagnosis, a Swedish study of 234 ME/CFS patients meeting the Canadian Consensus Criteria found that a substantial proportion of patients had signs on their brain MRIs suggestive of intracranial hypertension: 55% had increased diameter of the optic nerve sheath. In addition 80% had cerebellar tonsillar descent that could potentially cause disruptions to spinal fluid flow, and thus increased intracranial pressure. 13.2% had tonsillar herniations severe enough to be considered a Chiari Malformation.

Craniocervical instability
Craniocervical instability (CCI) is a pathological condition of increased mobility at the craniocervical junction, the area where the skull meets the spine. In CCI the ligamentous connections of the craniocervical junction can be stretched, weakened or ruptured.

CCI usually develops as a result of physical trauma such as a car accident, an inflammatory disease such as rheumatoid arthritis or a congenital disorder such as Down's syndrome. More recently, physicians have reported an increased prevalence of CCI in patients with hereditary disorders of connective tissue such as Ehlers Danlos Syndromes (EDS). There have also been anecdotal reports of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) who were later diagnosed with CCI,   although no scientific publication on this subject exists. It frequently co-occurs with atlantoaxial instability (AAI).

Atlantoaxial instability
Atlantoaxial instability (AAI) is characterized by excessive movement at the junction between the atlas (C1) and axis (C2) as a result of either a bone or ligament abnormality.

It can be caused by congenital conditions, inflammatory conditions like rheumatoid arthritis, as a result of physical trauma, or infection. It has been associated with Down syndrome, Morquio syndrome,  Marfan syndrome,  and Ehlers-Danlos syndrome.

Cervical stenosis
A 2018 case study published by Peter Rowe found marked post-operative improvement of symptoms in three patients with severe myalgic encephalomyelitis, orthostatic intolerance and cervical spinal stenosis.

Tethered cord syndrome
Tethered cord syndrome is a neurological disorder caused by tissue attachments that limit the movement of the spinal cord within the spinal column. It can be congenital or acquired and appear in childhood or adulthood. It is considered progressive. It causes spinal cord hypoperfusion, electrophysical changes and metabolic changes, including impaired glucose metabolism. As with craniocervical instability, There have also been anecdotal reports of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) who were later diagnosed with tethered cord, although no scientific publication on this subject exists.

Tarlov cysts
Perineural cysts or Tarlov cysts (TCs) are nerve root dilations resulting from pathologically increased cerebrospinal fluid pressure. A study of 197 ME/CFS patients found that the prevalence of Tarlov cysts was three times higher in ME/CFS patients than the general population, at 39%.

ME/CFS
A 2018 case study published by Peter Rowe found marked post-operative improvement of symptoms in three patients with severe myalgic encephalomyelitis, orthostatic intolerance and cervical spinal stenosis.

There have also been anecdotal reports of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) who were later diagnosed with Craniocervical instability and Tethered cord syndrome,   although no scientific publication on this subject exists.

A study of 197 ME/CFS and fibromyalgia patients found that the prevalence of Tarlov cysts was three times higher in ME/CFS patients than the general population, at 39%, a potential sign of elevated cerebrospinal fluid pressure.

Fibromyalgia
In the 1990s, there was a controversy  surrounding whether patients with some patients with Chiari malformation had been misdiagnosed with chronic fatigue syndrome or fibromyalgia or whether Chiari malformation could indeed cause the symptoms of each. A 2004 study of 270 patients with fibromyalgia diagnoses found that 46% had cervical spinal stenosis and 20% chiari malformation. However, a 2011 paper failed to find any increased rate of Chiari malformation among people with fibromyalgia. Chiari malformation is associated with Ehlers-Danlos syndrome, which is sometimes misdiagnosed as fibromyalgia, or with which there may be diagnostic overlap.

A significant improvement in physical and mental well-being was found in fibromyalgia patients with cervical stenosis who received surgery. A second study found that 71% had cervical spinal cord compression.

There are some cases of cervical stenosis that may not be apparent when the neck is in the neutral position, but may be quite severe in extension. Andrew Holman describes these cases as "positional cervical spinal cord compression." He argues that some symptoms of fibromyalgia may be an inflammatory response to intermittent cord irritation which may not be severe enough to cause more overt symptoms.

Ehlers-Danlos Syndromes
Several pathologies of the spine have been associated with Ehlers-Danlos Syndrome, including Chiari I malformation, Craniocervical instability, Atlantoaxial instability, Tethered cord syndrome, Tarlov cyst, as well intracranial hypertension.