Cross-section of thorax at L3-L4 disc showing relevant lumbar anatomy; two spinal needles illustrate the medial and lateral approaches into the subarachnoid space where the cerebrospinal fluid is located.

Posterior view of head of infant, skull and brain are illustrated. A fiber-optic transducer-tipped catheter has been inserted through a subarachnoid bolt into the white matter of the brain.

Posterior view of the spinal cord in situ with vertebral arches and posterior aspect of sacrum removed and dural sac cut open to reveal the spinal cord and nerve roots.

Dura mater, meninges