4 – Rami communicantes anatomy

Gray rami contain postganglionic sympathetic fibres from each ganglion of the sympathetic trunk to the adjacent spinal nerves (somatic fibre) or to internal organs (visceral fibres – only in some cervical and thoracic segments). In the cervical spine region, the gray rami penetrate the prevertebral layer of the deep cervical fascia and also the longus colli muscle on their way to the spinal nerves of the brachial plexus.

White rami are only present from T1-L2. I.e. they are not present in the cervical spine segment. They contain efferent preganglionic sympathetic fibres from the ipsilateral intermediolateral cell column (only present from T1-L2) of the spinal cord. These preganglionic fibres synapse with ganglia of the sympathetic trunk either at the same level or ascend or descend within the sympathetic trunk before they synapse. The white rami also contain afferent sympathetic fibres from the cell bodies in the dorsal root ganglia.