CSF Amino acids Test

Healthcare practitioners order a CSF amino acids test to check for inborn errors of amino acid metabolism, particularly in infants presenting with unexplained seizures. Some other symptoms that may prompt a doctor to order this test are:

• Poor feeding
• Lethargy
• Vomiting
• Seizures
• Developmental delay

Additionally, this test could also be ordered if a person has the following conditions with no apparent reasons:

• Cerebral oedema (brain swelling)
• Small size of the head
• Intellectual disability
• Psychiatric disorders 
• Mental retardation
• Movement disorders

No special preparations are needed for this test. If you are taking any prescribed, non-prescribed or illegal medications, please inform your doctor before the test. You may be advised to avoid drugs such as amphetamines, norepinephrine, levodopa and antibiotics before the test, as they can affect the test results. Do not stop any medication unless instructed by your doctor.

Also, it is advised to empty your bladder and bowels before the test.

Your healthcare practitioner or nurse will collect a sample of your cerebrospinal fluid through a procedure called a spinal tap or lumbar puncture. This procedure is done in the following manner:

• You will be asked to sit on the exam table or lie on your side.
• The doctor will clean your back and inject an anaesthetic to numb the area. A numbing cream may also be applied before the injection.
• When the area on the back becomes numb, a thin, hollow needle will be inserted between two bones (vertebrae) in the lower part of your spine and into the spinal canal. 
• Once the needle is in place, the doctor will draw a small amount of CSF for testing. 

The whole procedure takes no more than 30 minutes. It is important that you lie very still when the CSF is drawn. 

After the test, you may get some swelling and pain at the site where the needle was inserted, but these usually subside in a few days. Some people experience a headache after the test which may last for about a week. To prevent a headache, your doctor may ask you to lie on your back for at least an hour after the procedure.

If the symptoms persist or worsen, please inform your doctor.

Normal results: 

The normal values of different amino acids in the CSF are mentioned in the following table:

Abnormal results:

Low levels of amino acids in CSF are seen in the following conditions:

• Glutamine deficiency
• Serine deficiency disorders

High levels of amino acids in CSF are seen in the following conditions:

• Glycine encephalopathy (high levels of the amino acid glycine in CSF)
• Tyrosinaemia type II

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.