From the Guidelines
Lumbar puncture findings indicative of subarachnoid hemorrhage include xanthochromia and red blood cells that do not clear between sequential collection tubes, with xanthochromia being the most specific finding, as noted in the guidelines for the management of aneurysmal subarachnoid hemorrhage 1. The cerebrospinal fluid typically shows elevated opening pressure, increased protein levels, and normal glucose concentration.
- Key factors for the examination of CSF include an understanding of the timing of lumbar puncture in relation to SAH, red and white blood cell counts, the presence of xanthochromia, and detection of bilirubin.
- The presence of xanthochromia, which develops 2-12 hours after bleeding due to hemoglobin breakdown, is a critical finding that persists for up to two weeks.
- A traumatic tap can be distinguished from true subarachnoid hemorrhage by the clearing of red blood cells in successive tubes and absence of xanthochromia.
- Spectrophotometry provides the most sensitive detection of xanthochromia, though visual inspection is commonly used in clinical practice, as mentioned in the context of diagnosing subarachnoid hemorrhage 1. These findings are crucial for diagnosis when neuroimaging is negative but clinical suspicion remains high, particularly in patients presenting with thunderclap headache or other suspicious neurological symptoms.
- It is essential to consider the clinical context and other diagnostic findings, such as those from CT scans and MRI, to make an accurate diagnosis of subarachnoid hemorrhage, as outlined in the guidelines for the management of aneurysmal subarachnoid hemorrhage 1.
From the Research
Lumbar Puncture Findings Indicative of Subarachnoid Hemorrhage
The lumbar puncture (LP) is a diagnostic test used to assist in the diagnosis of subarachnoid hemorrhage (SAH). The findings of an LP can be indicative of SAH, and several methods can be used to distinguish traumatic LP from true SAH.
- The timing of the LP in relation to the onset of the SAH affects the results of the cerebrospinal fluid (CSF) analysis, with typical findings changing over time 2.
- Xanthochromia, the yellow discoloration of the CSF resulting from hemoglobin catabolism, is often critical in making a diagnosis of SAH 2.
- Other methods for distinguishing traumatic LP from true SAH include the "three tube test," opening pressure, and inspection for visual xanthochromia 2.
Diagnostic Challenges
Diagnosing SAH using LP can be challenging, especially when the CT scan is negative. In such cases, LP is recommended to exclude the presence of blood breakdown products 3.
- A retrospective analysis of prospectively recorded data found that LP-driven decision making in patients with a normal scan and suspected SAH is suboptimal in over a third of cases 3.
- The study suggests that secondary investigations, such as secondary imaging, may be more effective than LP in diagnosing SAH in patients with a normal CT scan 3.
Complications and Rare Cases
While LP is generally considered a safe procedure, severe complications, such as intracranial and intraspinal subarachnoid hematoma, can occur 4.
- A rare case report describes a patient who developed severe intracranial and intraspinal subarachnoid hemorrhage after a lumbar puncture, highlighting the potential risks of the procedure 4.
- Another case report describes a patient who developed spontaneous spinal subarachnoid hemorrhage after severe coughing, emphasizing the need to consider SAH in patients with sudden back pain and headache 5.