Platform
Company
Body Fluids
Review status
Currently under review
Pending specialist review and validation.
CSF Methionine measures the amount of the essential amino acid methionine in your cerebrospinal fluid, the clear liquid that cushions and surrounds your brain and spinal cord. Methionine is a building block for proteins and a key part of methylation pathways that help regulate many brain and body functions.
This test is usually performed as part of a cerebrospinal fluid amino acid profile using advanced chromatography and mass spectrometry methods. CSF is collected with a lumbar puncture under sterile conditions, then sent to the laboratory for analysis.
Changes in CSF methionine can be a clue to inherited metabolic conditions that affect the methionine and homocysteine cycle, as well as to liver or nutritional problems that alter amino acid balance. When evaluating seizures, developmental concerns, regression, or other unexplained neurologic symptoms, measuring amino acids directly in CSF can help show whether a metabolic process is affecting the central nervous system.
Findings in CSF complement results from blood and urine and can refine diagnosis, guide treatment choices, and help monitor certain conditions. The main risk associated with this testing is from the lumbar puncture itself, which may cause headache or local discomfort; the measurement performed by the laboratory does not add additional risk.
Your clinician will interpret your result alongside your symptoms, examination, imaging, and other lab tests. A result above the expected range can occur with specific inherited disorders of methionine metabolism or with significant liver dysfunction, but diet, supplements, and sample quality can also influence the level. A result below the expected range may be seen with protein insufficiency or with metabolic pathways that increase methionine use.
If your result is outside the expected range, follow up may include plasma amino acids, total homocysteine, vitamin B12 and folate status, liver enzymes, urine studies, and sometimes genetic testing. Your clinician may repeat testing if there is concern about blood contamination of the CSF sample or if your clinical situation changes. Share details about your diet, supplements, and medications so your care team can interpret the result accurately.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Even small amounts of blood from a difficult lumbar puncture can change CSF amino acid levels, potentially raising methionine; laboratories assess for this and may request a repeat sample if interference is suspected.
High protein intake, methionine or S-adenosylmethionine (SAMe) supplements, and parenteral nutrition can increase methionine; restrictive diets or poor intake can lower it, affecting interpretation.
Medicines that affect the liver, such as certain antiepileptics, and liver diseases can alter methionine handling and may raise levels; your care team will consider liver tests when reviewing results.
Correct tube type, prompt processing, and freezing are important for amino acid stability; delays, prolonged room temperature storage, or repeated freeze–thaw cycles can skew results.
Growing infants and children have different metabolic demands, and malnutrition or catabolic illness can shift amino acid patterns; clinicians interpret values in the clinical context.
Disorders of the methionine and homocysteine cycle can affect CSF methionine; results are usually interpreted together with plasma amino acids and total homocysteine to clarify the pattern.
References