Cervical spinal nerve C7 controls triceps and wrist extension. Cervical spinal nerve C8 helps control the hand. The cervicocranial syndrome occurs when symptoms arise due to cervical vertebrae damage (misalignment, collapse, shift or disease, such as tumor) resulting in the improper functioning of the cervical spinal nerves. Examples of Cervicocranial Syndrome Pathophysiology
Chordoma
The craniocervical junction region comprises C1 (Atlas), C2 (Axis) and the lower part of the skull: occipital bone. In case of tumor: chordoma, in the craniocervical junction region, this leads to pressure on the cervical spinal nerves, which results in their improper functioning of the cervical spinal nerves. Hence, leading to symptoms of cervicocranial syndrome. To decompress the pressure on the nerves, the tumor is removed and the foramen through which the spinal nerve roots travel through is enlarged to allow the nerves to pass through so that symptoms of cervicocranial syndrome can be reduced and the nerves are sending signals. Atlanto-Occipital Assimilation
When the occipital bone and the atlas (C1) are fused together in a condition called atlanto-occipital assimilation, it causes improper functioning of the cervical spinal nerves due to the vascular compression. Surgical procedure can decompress the nerves and reduce symptoms. Trauma
Traumatic injuries are caused when external forces damage the cervical spine, giving rise to various symptoms. In a car accident, the vehicle jerks the neck forward and backward resulting in cervical spine damage resulting in a whiplash.
Cervicocranial syndrome or (Craniocervical Junction Syndrome: CCJ syndrome) is a neurological illness. It is a combination of symptoms that are caused by an abnormality in the neck. The bones of the neck that are affected are cervical vertebrae (C1 - C7). This syndrome can be identified by confirming cervical bone shifts, collapsed cervical bones or misalignment of the cervical bone leading to improper functioning of cervical spinal nerves. [1]  Cervicocranial syndrome is either congenital or acquired (as a result of injury or disease). Some examples of diseases that could result in cervicocranial syndrome are Chiari disease, Klippel-Feil malformation osteoarthritis, and trauma. Treatment options include neck braces, pain medication and surgery. The quality of life for individuals suffering from CCJ syndrome can improve through surgery. Signs and Symptoms
Cervicocranial syndrome has a wide range of symptoms. These symptoms often include:

Vertigo
Chronic Headache aka Cephalea
Tinnitus
Facial Pain
Ear Pain
Dysphagia
Carotidynia
Neck Pain (ex: during movement such extension and flexion)
Syncope
Sinus congestion
Neck Crepitus Sound
Loss of vision
Involuntary eye-movement
Severe Fatigue
Chest Pain
Brain Fog

Cause
The cause of cervicocranial syndrome is either due to a defect (genetic mutation or development of diseases later in life) or an injury pertaining to the neck: cervical area, that damages the spinal nerves traveling through the cervical region resulting in ventral subluxation. Examples of cases that can result in cervicocranial syndrome are: car accidents, trauma, osteoarthritis, tumor, degenerative pathology and other numerous causes of vertebral instability. There is no single cause that can mainly cause cervicocranial syndrome. Genetic
The genes GDF6, GDF3, MEOX1 used as examples, encode for making proteins that help with development.