Laboratory screening tests of blood, urine, or other substances are used to help diagnose disease, better understand the disease process, and monitor levels of therapeutic drugs. Certain tests, ordered by the physician as part of a regular check-up, provide general information, while others are used to identify specific health concerns.
For example, blood and blood product tests can detect brain and/or spinal cord infection, bone marrow disease, hemorrhage, blood vessel damage, toxins that affect the nervous system, and the presence of antibodies that signal the presence of an autoimmune disease. Blood tests are also used to monitor levels of therapeutic drugs used to treat epilepsy and other neurological disorders. Genetic testing of DNA extracted from white cells in the blood can help diagnose Huntington’s disease and other congenital diseases.
Analysis of the fluid that surrounds the brain and spinal cord can detect meningitis, acute and chronic inflammation, rare infections, and some cases of multiple sclerosis. Chemical and metabolic testing of the blood can indicate protein disorders, some forms of muscular dystrophy and other muscle disorders, and diabetes. Urinalysis can reveal abnormal substances in the urine or the presence or absence of certain proteins that cause diseases including the mucopolysaccharidoses.
Genetic testing or counseling can help parents who have a family history of a neurological disease determine if they are carrying one of the known genes that cause the disorder or find out if their child is affected. Genetic testing can identify many neurological disorders, including spina bifida, in utero (while the child is inside the mother’s womb). Genetic tests include the following:
- Amniocentesis, usually done at 14-16 weeks of pregnancy, tests a sample of the amniotic fluid in the womb for genetic defects (the fluid and the fetus have the same DNA). Under local anesthesia, a thin needle is inserted through the woman’s abdomen and into the womb. About 20 milliliters of fluid (roughly 4 teaspoons) is withdrawn and sent to a lab for evaluation. Test results often take 1-2 weeks.
- Chorionic villus sampling, or CVS, is performed by removing and testing a very small sample of the placenta during early pregnancy. The sample, which contains the same DNA as the fetus, is removed by catheter or fine needle inserted through the cervix or by a fine needle inserted through the abdomen. It is tested for genetic abnormalities and results are usually available within 2 weeks. CVS should not be performed after the tenth week of pregnancy.
- Uterine ultrasound is performed using a surface probe with gel. This noninvasive test can suggest the diagnosis of conditions such as chromosomal disorders
Specific tests in a neurological examination include:
- Examination of posture
- Abnormal movements
- Cerebellar testing
- Finger-to-nose test
- Ankle-over-tibia test
- Rapid pronation-supination
- Assessment of gait
- Intension tremor
- Staccato speech
- Pronator drift
- Cogwheeling (abnormal tone suggestive of Parkinson's disease)
- Gegenhalten - is resistance to passive change, where the strength of antagonist muscles increases with increasing examiner force. More common in dementia.
- Romberg test to examine proprioception or cerebellar function
- Resting tremors
- Light touch
- Position sense
- Stereognosis, and
- Two-point discrimination (for discriminative sense)
Sources: National Institute of Neurological Disorders and Stroke; Wikipedia