Back & Spinal Cord LO 7

7. Understand how the anatomy of the meninges relates to basic clinical procedures.

Lumbar puncture (also referred to as spinal tap) enter the subarachnoid space in order to evaluate potential central nervous system or meninges disorders.

  • Needle is typically inserted into the supracristal plane (a plane located at the level of tips of the iliac crests; typically ~L4) in the midline
    • The goal is to insert the needle between the spinous processes of L3-L4 or L4-L5
    • At this level, the practitioner does not need to be concerned with damaging the spinal cord (as it has ended) but is still within the dural sac

Epidural block (also referred to as ‘an epidural’) is the injection of an anesthetic agent into the epidural space. Common areas of injection include ~L3-L4 or at the level of the sacral hiatus or sacral foramina (caudal epidural block). This type of block will be discussed in more detail during the reproductive anatomy sessions.

Spinal anesthesia is the injection of an anesthetic agent into the subarachnoid space. This will anesthetize the region entered and inferiorly with the patient inclined. A typical location for entering the needle is the midline of supracristal plane, which will anesthetize all areas inferior to L4 including lower limbs.