Normal Appearance of Cerebrospinal Fluid
Normal cerebrospinal fluid is clear and colorless, resembling water, with no visible turbidity or clotted material. 1, 2, 3, 4
Physical Characteristics
- CSF should be crystal clear and colorless when examined visually 3, 4
- The fluid is an ultrafiltrate of plasma with very low protein content, which accounts for its water-like transparency 3, 5
- Any deviation from this clear, colorless appearance suggests pathology 4
Volume and Production
- Approximately 140 mL of CSF exists in the subarachnoid space in adults, a volume that remains relatively constant regardless of height or weight 1, 6
- The body produces approximately 500-800 mL of CSF daily, meaning the entire CSF volume is replaced 4-5 times per day 1, 6
Normal Composition Profile
When CSF appears normal (clear and colorless), the characteristic laboratory profile includes: 1
- Normal opening pressure (6-25 cmH₂O, mean ~18 cmH₂O) 6
- Normal glucose levels (approximately 2/3 of serum glucose) 1, 6
- Normal protein content (low levels) 1, 3
- Absence of pleocytosis (no excess white blood cells) 1
Abnormal Appearances and Their Significance
Any cloudiness, turbidity, or color change indicates pathology: 2, 4
- Turbid or cloudy CSF suggests elevated white blood cell counts, typically seen in bacterial meningitis 2
- Xanthochromia (yellow discoloration) indicates breakdown products from red blood cells, suggesting prior hemorrhage 2
- Bloody CSF may indicate subarachnoid hemorrhage or traumatic tap 2
Common Pitfall
CSF that appears grossly normal does not exclude all pathology—microscopic and chemical analysis remain essential for complete evaluation, as some infections and inflammatory conditions may not alter the gross appearance initially 2, 5