Which spinal nerves do not form plexus?

Spinal nerves that do not form plexi include:

- Cervical nerves C1 and C2: These spinal nerves form the suboccipital nerve and greater occipital nerve, respectively, and do not contribute to any brachial plexus.

- Thoracic nerves T12 and Lumbar nerves L1 and L2: These spinal nerves emerge from the vertebral column without forming a plexus and directly innervate specific structures, such as the subcostal, iliohypogastric, and genitofemoral muscles.