The spinal cord is a thick nerve trunk that forms the brain’s most important connection to the body and carries all signals to and from the brain that are not provided by the cranial nerves.The spinal nerve extends from the inferior end of the brain stem and passes through the foramen magnum of the skull into the neck.ight spinal nerves branch off from the spinal cord in the neck to form a network of nerves called the cervical plexus. The cervical plexus forms many connections between the brain and the skin and muscles of the head and neck, similar to the cranial nerves.