Metabolic Testing

Metabolic testing in neurology refers to a variety of tests which evaluate the body's ability to break-down ("metabolize") dietary compounds (i.e. proteins, fats, carbohydrates, and related structures). There are many cases in which a parent compound (e.g. a large fat molecule) is normally broken down into smaller compounds by a specific enzyme. Many diseases are characterized by a missing or dysfunctional enzyme, which can lead to a build-up of the parent compound in the brain (and other tissues), thereby causing problems such as epilepsy or infantile spasms. Metabolic testing is typically performed on blood and urine for convenience, but in many cases it is necessary to conduct metabolic tests on cerebrospinal fluid (CSF), the fluid that bathes the brain and spinal cord. To obtain CSF, a lumbar puncture (spinal tap) is required. Like genetic testing, metabolic testing can (1) help identify the cause of infantile spasms, and (2) impact the choice of medication or other therapy (including a variety of potential diet changes or perhaps institution of a ketogenic diet). Metabolic testing is not required for all patients with infantile spasms, i.e. those patients for whom a cause is already identified. 

The most frequently performed metabolic tests are screening panels which examine numerous metabolic "pathways" with a single sample of blood, urine, and/or CSF. These panels include testing for 'serum amino acids', 'urine organic acids', and 'CSF amino acids'. There are numerous other metabolic tests tailored to individual patients with symptoms or other features suggesting a specific metabolic abnormality.


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