What is Craniocervical Instability: Causes, Symptoms, Treatment, Prognosis, Pathophysiology

Craniocervical instability is a pathological deformity of the brainstem, upper spinal cord and cerebellum that causes structural instability of the craniocervical junction. It is also known as the syndrome of occipitoatlantoaxial hypermobility. It is a common finding in individuals affected by Ehlers-Danlos syndrome.

Ehlers-Danlos Syndrome is a rare genetic order characterized by abnormal or faulty production of the collagen. There may be a structural defect in the collagen or a fault with the proteins that binds with the collagen. Symptoms include hypermobility of joints, stretchy skin, easy tearing of skin, vascular fragility and increased risk of developing cardiovascular complications such as aneurysms.

• Constant headache with a persistent feeling of heavy head and weak neck.
• Pressure Headache: One of the symptoms of craniocervical instability is pressure headache which is caused by disruption in flow of Cerebrospinal fluid which in turn increases the intracranial pressure. This may be aggravated by the Valsalva manoeuvres such as crying, laughing, yawning, coughing, sneezing or straining.
• Dysfunctional Autonomic Nervous System: This is also known as dysautonomia. It is characterised by increased heart beat or tachycardia, intolerance to heat, orthostatic intolerance, frequent episodes of fainting or syncope, increased thirst, slow gastric emptying, excessive fatigue etc.

Other common symptoms of craniocervical instability include:

• Sleep apnea
• Neck pain
• Unsteady balance
• Weakness in muscles
• Facial pain and numbness
• Vertigo or dizziness
• Visual issues
• Tinnitus and hearing deficiency
• Nausea
• Vomiting
• Dysphagia and reduced gag reflux
• Lack of coordination
• Irregular eye movement or nystagmus
• Paralysis.

Craniocervical instability when diagnosed early can be treated and the condition can be reversed. In severe cases, craniocervical instability causes permanent disability and nerve damage.

Craniocervical instability is caused by absence of connective tissue support at the craniocervical junction. This is commonly seen in patients with Ehlers-Danlos syndrome. The risk of developing craniocervical instability increases with exposure to head and neck injury and other repetitive stretch injuries. This can be caused by simple repetitive injuries such as turning his or her head. Stretch injuries may lead to craniocervical instability in the following ways:

• Craniocervical Instability Caused Due to Dysfunctioning of the Nerve: Repetitive stress over the head and neck region can lead to nerve injury in the area.
• Pannus Formation as a Cause of Craniocervical Instability: A pannus may form in the hypermobile joints, which in turn may erode the articular cartilage and bone. When a pannus is formed over the odontoid bone it leads to compression of the brainstem. This can lead to craniocervical instability.
• Craniocervical Instability Caused Due to Misalignment of the Bone: Loose ligaments can cause retro flexion of the odontoid. This is caused by misalignment and improper angulation of the odontoid bone. Over a period of time it can cause compression of the brainstem.
• Chiari Malformation: There may be pressure build up on the cerebellum and brainstem due to downward displacement of the cerebellar tonsils. This can progressively damage the area over a period of time and can also block the flow of cerebral spinal fluid leading to craniocervical instability.
• Cranial Settling: In some cases there may be downward shift of the skull into the spine. Basilar invagination may occur characterised by projection of the tip of the odontoid process into the foramen magnum.

The risk factors include

• Structural abnormalities such as os odontoideum, atlas assimilation, congenital klippel-feil malformation, atlas hypoplasia, Chiari malformations.
• General or systemic disorders such as Achondroplasia, Down syndrome, Morquio syndrome, osteogenesis imperfecta etc.
• Trauma and injuries
• Rheumatoid arthritis and Paget disease
• Metastatic tumors
• Meningioma
• Chordoma.

Most of the histopathological changes may not be noted on routine diagnostic changes. MRI taken in an upright position may be helpful in certain conditions. Rotational 3D CT scan is quite helpful in diagnosis of craniocervical instability. In some cases, invasive cervical traction may be used. It is a procedure where the individual’s head is pulled by a pulley upwards over a course of 48 hours. Physical examination may be done by an experienced physician to arrive at a conclusion. The patients’ head may be physically pulled upwards or downwards to check for pain, discomfort and tenderness.

The treatment modality for Craniocervical Instability includes cervical traction followed by cervical fusion. The head is pulled upward mechanically and brought to the correct anatomical position. In order to hold the structure at the right position, the occipital bone is fused with the upper cervical vertebrae. Titanium hardware, bone grafts or morphogenic proteins may be used for this procedure. Post-surgical immobilization is suggested for complete fusion of the bones. A cervical brace, halo vest or customized Minerva may be given to maintain a neutral posture and restrict mobility until there is complete healing. In some cases electrocautery may be used to shrink the cerebellar tonsils. This also improves blockage of flow of cerebrospinal fluid.

Craniocervical instability is a condition characterised by deformity and instability of the craniocervical junction. Craniocervical instability is commonly associated with Ehlers-Danlos syndrome and other connective tissue syndrome. Craniocervical instability is caused by lack of support at the craniocervical junction leading to compression over the brain stem. Craniocervical instability is reversible if detected early. However, if left untreated it can lead to permanent deformity.