What CSF findings are typically indicative of subarachnoid hemorrhage?

Subarachnoid hemorrhage (SAH) typically presents with a distinct profile in cerebrospinal fluid (CSF) analysis. The most indicative finding in cases of SAH is the presence of numerous red blood cells (RBCs) in the CSF, especially when comparing serial samples taken over time. This finding is important because it suggests that there has been an acute bleed into the subarachnoid space, which can occur due to various causes, such as ruptured cerebral aneurysms.

When evaluating CSF in SAH, the concentration of RBCs can be high, and it's crucial to observe for a consistent presence of blood across samples taken at different times, thus affirming an ongoing or recent bleeding event. In contrast, other CSF findings mentioned, while they may arise from different pathologies, do not characterize subarachnoid hemorrhage specifically.

For example, low glucose levels and neutrophil (PMN) predominance might suggest bacterial meningitis rather than SAH. Increased gamma globulins could indicate chronic infections or inflammatory conditions, and normal glucose with lymphocytic predominance is typically associated with viral infections or autoimmune processes rather than SAH. The presence of numerous RBCs distinctly points to the acute