Medical Analysis

CSF Examination Part 2: Comprehensive Diagnostic Evaluation of Cerebrospinal Fluid Pressure, Gross Interpretation, and Clinical Implications

Introduction to Cerebrospinal Fluid Examination

Cerebrospinal Fluid (CSF) Examination is an extensive and clinically significant topic [1, 2]. Its proper understanding is crucial, as the findings profoundly influence both diagnosis and prognosis, directly impacting patient care and clinical decision-making [1, 2]. Due to the vastness of this subject, it is not feasible to cover every aspect within a single presentation [1, 2]. This presentation is one of a series of six on CSF Examination [1, 2]. Viewers are encouraged to go through the remaining five presentations for a complete and comprehensive understanding of this topic [1, 2]. Thank you for your attention and commitment to learning [1, 2].

Opening Pressure Clinical Context and Measurement Procedure

Opening pressure measurement must be done in conjunction with clinical findings, patient history, and other diagnostic tests [1, 15]. Monitoring of CSF pressure (with or without an anterior fontanelle sensor) can be useful in the evaluation of the degree of cerebral edema, the development of obstructive hydrocephalus, and the occurrence of a major intracerebral mass or extracerebral collection [1, 15]. CSF pressure is directly related to jugular and vertebral venous pressures [1, 15].

Regarding the exact measurement procedure, after attaching the manometer to the hub of the spinal needle, the patient’s legs should be gently extended and the neck returned to the neutral position [6, 20]. The CSF pressure is then measured [6, 20]. The patient should be relaxed [6, 20]. Tension, straining, or breath-holding increase the CSF pressure, while hyperventilation can lower the opening pressure [6, 20].

Normal Opening Pressure Ranges and Critical Pressure Thresholds

• 60-180 mm of water in adults in the lateral recumbent position [3, 4].

• 10-100 mm of water in children less than 8 years [8].

• Up to 250 mm of water in an obese patient [3, 5, 6].

• If the opening CSF pressure is greater than 200 mm, no more than 1-2 ml of CSF should be removed [15, 20].

• If greater than 250 mm of water pressure, think of intracranial tension [3, 5, 17].

Elevated CSF Pressure and Intracranial Hypertension Pathologies

Elevated CSF pressure or intracranial hypertension can be triggered by several distinct pathological conditions [15, 17]:

• Idiopathic Intracranial Hypertension (IIH): Occurs without any detectable cause [16, 17].

• Space-occupying lesions: Includes tumors, abscesses, or other masses [15].

• Infections: Encompassing meningitis or encephalitis [15].

• Venous sinus thrombosis: Blockage of venous sinuses can impair CSF drainage [5].

• Hydrocephalus: The build-up of CSF in the brain can lead to increased pressure [15].

• Cerebral oedema [15]

• Subarachnoid hemorrhage [13, 14]

• Congestive cardiac failure [15]

• Benign intracranial hypertension (pseudotumor cerebri) [16]

Clinical Significance of Elevated Pressure

Symptoms include severe headache, blurred vision, nausea, vomiting, and papilledema (swelling of the optic disc) [16, 17].

Reduced CSF Pressure and Hypotenusive Etiologies

Reduced CSF pressure can result from multiple anatomical and physiological disruptions [15]:

• CSF leakage: A tear in the dura mater, which may also be possible due to trauma or a previous lumbar puncture [15].

• Dehydration: Reduced CSF volume can lead to lower pressure [15].

• Spinal stenosis: Narrowing of the spinal canal can restrict CSF flow [15].

• Leakage of spinal fluid following trauma or previous lumbar puncture [15].

A large difference between opening and closing pressures usually indicates the presence of a partial or complete spinal block [15].

Clinical Significance of Reduced Pressure

Symptoms consist of postural headaches (worsening when upright), dizziness, and neck stiffness [15].

Gross Examination Parameters

Normal CSF is clear, colorless like distilled water, and does not clot [1, 15]. During gross examination, practitioners must systematically check for six specific features [1, 15]:

• Appearance [1, 15]

• Colour [1, 15]

• Clot [1, 15]

• Blood [1, 15]

• Xanthochromia [1, 15, 18]

• Viscosity [1, 15]

CSF Appearance Analysis Table

Detailed CSF Colour Interpretation Table

Clot Formation Dynamics and Etiological Associations

Clot formation in CSF is abnormal and indicates increased proteins [1, 15]. A pellicle (thin membrane or scum on the surface of CSF) or clot formation (after 10 minutes of collection) indicates increased proteins (greater than 150 mg/dl) [1, 15].

Causes of Clot Formation:

• Tuberculous meningitis: rightarrow fine cobweblike clot after 12-24 hours [1, 15]

• Purulent meningitis: pellicle forms early followed by a large clot [1, 15]

• Spinal block: complete clotting of CSF [1, 15]

• Traumatic LP [1, 15]

Clot formation does not occur in subarachnoid hemorrhage [13, 14, 15].

Blood Presence and Differential Diagnosis

Normally, CSF is colorless and clear [1, 15]. Blood-stained CSF may result from a traumatic tap (due to injury to the venous plexus in the spinal wall) or subarachnoid hemorrhage [13, 14, 15, 19]. Differentiation of a traumatic tap from subarachnoid hemorrhage is very important [13, 14, 19].

Comprehensive Comparison: Traumatic Tap versus Subarachnoid Hemorrhage

Xanthochromia Evaluation and Froin’s Syndrome

Xanthochromia is yellow discoloration of CSF [18]. CSF is centrifuged and the supernatant is compared with another tube of the same size filled with distilled water [18].

Causes of Xanthochromia:

• Subarachnoid Hemorrhage [13, 14, 18]

• Jaundice (Bilirubin greater than 6.0 mg/dl) [1, 15]

• CSF Protein (greater than 150 mg/dl) [1, 15]

Froin’s Syndrome: It is a combination of xanthochromia, excess proteins in CSF, and spontaneous formation of a coagulum in CSF on standing [12, 15]. It results from a complete block of the subarachnoid space [12, 15].

Viscosity Characteristics and Pathological Elevation

Normally, CSF is not viscous [1, 15]. Causes of raised viscosity include [1, 15]:

• Cryptococcal meningitis [1, 15]

• Meningeal metastatic mucinous adenocarcinoma [1, 15]

• Severe meningitis [1, 15]

• Release of nucleus pulposus fluid in CSF due to needle injury to the intervertebral disk [1, 15]

Summary and Acknowledgments

Trusted Insights. Curated by Dr. Dipak Ladda [1, 2].

For Non-Medicos

Quick Guide to CSF Pressure and Appearance

What is This Test About?

This guide explains part two of Dr. Dipak Ladda’s series on analyzing cerebrospinal fluid (CSF), focusing on pressure readings, physical appearance, and warning signs [1, 2].

Understanding CSF Pressure

• Normal Pressures: Usually 60-180 mm of water for adults, 10-100 mm for young children, and up to 250 mm for obese individuals [3, 4, 5, 8].

• High Pressure: Can point to severe conditions like brain swelling, tumors, infections (meningitis), or hydrocephalus, causing severe headaches and vision changes [15, 16, 17].

• Low Pressure: Often caused by fluid leaks from spinal tears, dehydration, or spinal narrowing, resulting in posture-dependent headaches [15].

What Gross Examination Reveals

• Color and Clarity: Normal CSF looks clear and colorless like distilled water [1, 15]. Yellowish tints (xanthochromia) or cloudiness point to bleeding, old hemorrhages, or high white blood cells [1, 15, 18].

• Blood vs. Needle Injury: Doctors carefully check if blood in the samples comes from an accidental poke during the procedure (traumatic tap) or actual internal bleeding (subarachnoid hemorrhage) [13, 14, 19].

• Clots and Thickness: Clots or thick fluid can indicate severe infections, high protein levels, or spinal blocks [1, 12, 15].

References:

1. Daroff, R. B., Bradley, W. G., & Marsden, C. (2004). Neurology in clinical practice. Boston: Butterworth-Heinemann (Elsevier).

2. Warrell, D. A., Cox, T. M., Cox, J. D., & Benz, E. J. (Eds.). (2005). Oxford textbook of medicine. Oxford, UK: Oxford University Press.

3. Corbett, J. J., & Mehta, M. P. (1983). Cerebrospinal fluid pressure in normal obese subjects and patients with pseudotumour cerebri. Neurology, 33, 1386–1388.

4. Gilland, O., Tourtellotte, W. W., O’Tauma, L., & Henderson, W. G. (1974). Normal cerebrospinal fluid pressure. J Neurosurg, 40, 587–593.

5. Bono, F., Lupo, M. R., & Serra, P. (2002). Obesity does not induce abnormal CSF pressure in subjects with normal cerebral MR venography. Neurology, 59, 1641–1643.

6. Berdahl, J. P., Fleischman, D., Zaydlarova, J., Stinnett, S., Allingham, R. R., & Fautsch, M. P. Body mass index has a linear relationship with cerebrospinal fluid pressure.

7. Albeck, M. J., Skak, C., Borgesen, S. E., & Gjerris, F. (1990). A simple manometric method for clinical measurement of cerebrospinal fluid pressure. Br J Neurosurg, 4, 195–200.

8. Avery, R. A., Shah, S. S., Chun, T. T., & Liu, G. T. (2010). Normal cerebrospinal fluid opening pressure in children. J Neurosurg Pediatr, 3, 201–205.

9. Ekstedt, J. (1978). CSF hydrodynamic studies in man. 2. Normal hydrodynamic variables related to CSF pressure and flow. J Neurol Neurosurg Psychiatry, 41, 345–353.

10. Minns, R. A., Engleman, H. M., & Stirling, H. (1989). Cerebrospinal fluid pressure in pyogenic meningitis. Arch Dis Child, 64, 811–819.

11. Link, H., & Tibbling, G. (1977). Principles of CSF analysis in patients with multiple sclerosis. Scand J Clin Lab Invest, 37, 397–401.

12. Froin, G. (1903). Lésions sous-arachnoïdiennes et liquidiennes. Variations de l’albumine et de la coagulation. Gaz Hop Paris, 76, 1005–1006.

13. Vermeulen, M., & van Gijn, J. (1982). The diagnostic value of lumbar puncture in subarachnoid hemorrhage. Neurology, 32, 381–384.

14. Edlow, J. A., & Caplan, L. R. (2000). Avoiding pitfalls in the diagnosis of subarachnoid hemorrhage. N Engl J Med, 342, 29–36.

15. Ropper, A. H., Samuels, M. A., & Klein, J. P. (2019). Adams and Victor’s Principles of Neurology (11th ed.). New York: McGraw-Hill Education.

16. Landy, S. H., & Tyler, H. R. (1985). Pseudotumor cerebri and pregnancy. Neurology, 35, 1581–1583.

17. Wall, M., & George, D. (1991). Idiopathic intracranial hypertension. A prospective study of 50 patients. Brain, 114, 155–180.

18. Gray, L. W., Currie, S., & Hutchinson, P. J. (2008). Spectrophotometric analysis of cerebrospinal fluid for xanthochromia in suspected subarachnoid hemorrhage. Ann Clin Biochem, 45, 285–288.

19. Bonnici, J., O’Connell, M., & O’Donovan, D. (2011). Diagnostic utility of D-dimer in cerebrospinal fluid for distinguishing traumatic lumbar puncture from subarachnoid hemorrhage. Clin Chim Acta, 412, 432–435.

20. Kjellberg, R. N., Davis, K. R., Lyons, S., & Richardson, E. P., Jr. (1976). Intracranial pressure monitoring via lumbar puncture manometry. J Neurosurg, 45, 329–335.

FAQ’s:

1. What is CSF part 2 about?
It covers cerebrospinal fluid pressure readings, gross interpretation, and clinical implications.

2. What is normal adult CSF pressure?
Normal adult CSF pressure is 60-180 mm of water in lateral recumbent position.

3. What causes elevated CSF pressure?
Idiopathic intracranial hypertension, tumors, infections, hydrocephalus, and cerebral oedema cause elevated pressure.

4. What indicates reduced CSF pressure?
CSF leaks, dehydration, spinal stenosis, and previous lumbar punctures indicate reduced pressure.

5. What does normal CSF look like?
Normal CSF is clear, colorless like distilled water, and does not clot.

6. What causes turbid CSF?
Turbid CSF is caused by over 200 leucocytes per c.mm or microorganisms.

7. What does CSF color indicate?
Colorless is normal; yellow, pink, red, brown, or orange indicate bleeding, jaundice, or melanoma.

8. What causes CSF clot formation?
Clot formation indicates increased proteins above 150 mg/dl, seen in meningitis or spinal blocks.

9. How to differentiate traumatic tap?
Traumatic taps show clearing blood in later tubes and clear supernatant after centrifugation.

10. What is Froin’s syndrome?
It combines xanthochromia, excess CSF proteins, and spontaneous coagulum from complete subarachnoid block.