Final answer:
A stellate ganglion block is a medical procedure aimed at relieving pain but can have unintended consequences due to the anatomical complexity of the injection site, such as accidental injection, hoarseness, or Horner's syndrome.
Step-by-step explanation:
The stellate ganglion block is a procedure usually performed to relieve pain or to diagnose the source of pain. The stellate ganglion is a collection of nerves (sympathetic) found at the level of the sixth and seventh cervical vertebrae (the last cervical vertebra and the first thoracic vertebra). It's considered to be a sympathetic ganglion, part of the sympathetic nervous system, which can influence various parts of the body, including the face and arms.
An unintended consequence of the stellate ganglion block can sometimes occur because the injection site is close to other structures in the neck. Complications might include accidental injection into a blood vessel, hoarseness due to a blocked recurrent laryngeal nerve, or Horner's syndrome which is characterized by drooping of the eyelid (ptosis), constricted pupil (miosis), and lack of sweating (anhidrosis) on one side of the face.