Radiation concerns preclude the use of fluoroscopy guidance in lumbar puncture procedures performed on pregnant women or other at-risk groups. We have developed an alternative method for guidance based on a simple, unscanned polarization-sensitive optical coherence tomography needle tip probe. Using the porcine spine as a model, we show that the polarization signals returned by the probe allow each layer from the skin to the subarachnoid space to be uniquely identified in situ. Combining these signals with needle-tip tracking using Doppler methods provides real-time anatomical localization of the needle tip.