Intrathecal

Intrathecal (intra- + theca, “within a sheath”) is an adjective that refers to something occurring in or introduced into the anatomic space or potential space inside a sheath, most commonly the arachnoid membrane of the brain or spinal cord (under which is the subarachnoid space). For example, intrathecal immunoglobulin production is production of antibodies in the spinal cord, and an intrathecal injection (often simply called “an intrathecal”) is a route of administration for drugs via an injection into the spinal canal, more specifically into the subarachnoid space so that it reaches the CSF and is useful in spinal anaesthesia, chemotherapy, or pain management applications.