Interruption of autonomic nerve transmission at the spinal nerve roots or sympathetic ganglion can produce autonomic nerve block, providing treatment for severe pain and visceral pain syndromes. Block of spinal nerve roots with subarachnoid, epidural, or paravertebral blocks results in the blockade of somatic, sympathetic-mediated, and psychogenic pain origins.
Sympathetic ganglion blocks can be used to help differentiate pain that arises from sympathetic origins. They are widely used for both diagnostic and therapeutic purposes. Pain syndromes responsive to initial sympathetic blocks are then treated with repeated blocks or followed up with surgical, chemical, or radiofrequency sympathectomy.
AUTONOMIC NERVOUS SYSTEM ANATOMY
The sympathetic chain receives afferent visceral fibers that conduct pain from the head, neck, abdominal and pelvic viscera, and extremities. The sympathetic nervous system (SNS) is part of the autonomic nervous system (ANS), which innervates a variety of visceral organs, smooth muscle and glandular tissues, mediating a variety of reflexes. In certain pathologic pain states, neuronal hyperactivity in the SNS may be involved in the maintenance of chronic pain.
The peripheral sympathetic system arises from the intermediolateral column of the spinal cord. The axons of these cells leave the spinal cord via the ventral nerve roots of T1 to L2. The ventral nerve root initially proceeds as part of a spinal nerve, separates from the somatic motor neuron, forming white rami communicans, which synapses with sympathetic ganglia located along the anterolateral surface of the vertebral bodies.
Preganglionic fibers may transverse variable distances cephalad and caudad, forming synapses with many postganglionic neurons in different ganglia at other levels in the chain. Postganglionic axons exit the ganglia as gray rami communicans, which join the spinal nerve to their peripheral targets.
Painful syndromes that may benefit from stellate ganglion blocks include those that cause face, neck, arm, and upper chest pain. Stellate blocks may also be used for vasospastic disorders causing vascular insufficiency of the arm.
In the cervical and thoracic regions, the sympathetic chain lies anterolateral to the vertebral body, just anterior to the transverse processes. The cervical sympathetic chain is composed of a superior, middle, and inferior cervical ganglion. The inferior cervical ganglion and first thoracic ganglion fuse to form the stellate ganglion. The stellate ganglion receives preganglionic sympathetic fibers via white rami communicans from the intermediolateral cell column of T1 to T6 in the spinal cord.
The ganglion resides within a fascial space, anterior to the first rib along the anterior tubercle of C7. The dome of the pleura binds it inferiorly. Anterior to the ganglion lies the carotid sheath and vertebral artery. Posterior to the ganglion lies the transverse process of C7 and T1. Superior to the stellate ganglion is the transverse process of the C6 vertebrae, or Chassaignac’s ...