Narcolepsy is a medical condition where there is inability of the brain to regulate waking and sleeping cycles normally. A person suffering from narcolepsy is likely to have an overwhelming urge to fall asleep. While in some cases, a person may fall asleep for a few seconds or few minutes, others may remain asleep for much longer. Such episodes of daytime sleepiness can be dangerous and disabling. Narcolepsy can result in excessive daytime sleepiness or sudden sleep attacks. In many cases, narcolepsy remains undiagnosed.
Major symptoms of narcolepsy include REM sleep disturbance, cataplexy, hallucinations and sleep paralysis. Cataplexy indicates sudden loss of muscle control leading to weakness. This can occur during the initial attacks of narcolepsy. Such episodes are not to be confused with seizures. While some patients notice weakness in some muscles such as eyelids, others may suffer a loss of tone in all voluntary muscles. Hallucinations are another symptom of narcolepsy. The patient is likely to experience delusions that can often be frightening. Sleep paralysis refers to a temporary inability to move while suffering a sleeping attack during narcolepsy. The patient might notice this while falling asleep or waking up.
Diagnostic tests such as overnight polysomnography or Multiple Sleep Latency Test (MSLT) are used. Polysomnogram involves placement of electrodes on your scalp before falling asleep. This test measures the movement of the eyes and muscles and monitors the electrical activity of the brain. MSLT is a test to check how long it takes you to fall asleep. This throws light on the sleep patterns of the patient and helps in understanding and measuring sleep latency. Medications for narcolepsy can help reduce signs and symptoms. These medicines may interfere with other health conditions such as hypertension and diabetes. Antidepressants can reduce symptoms of cataplexy and sleep paralysis.
EEG or Electroencephalography is a diagnostic test that measures the brain's electrical activity. This non-invasive test is used to detect any abnormality in the brain's electrical impulses. Nearly 16 - 25 electrodes are placed over different areas of your head and they record electrical activity. A study of the pattern of these electrical activities of the brain help in detecting any abnormality. Electroencephalography helps in detecting causes of seizures, epilepsy or degenerative diseases.
It helps in evaluating head injury, tumor or infections. But an EEG cannot help diagnose mental illness. Sleep disorders such as narcolepsy can be evaluated with the help of EEG. An EEG helps confirm brain death in comatose patients. Brain tumors, encephalitis, meningitis, Parkinson's disease or cerebral infarct can be detected with EEG test.
The patient will need to lie down with eyes closed during the EEG test. Sometimes the doctor may ask the patient to breathe deeply or look at bright flickering lights. Sometimes the patient may also be asked to go to sleep. The patient must not consume caffeine, tea, cola or chocolate for about 8 hours prior to the EEG test. The hair must be free of oils, creams or sprays. Medications such as tranquilizers, muscle relaxants and anti-epilepsy medicines might need to be discontinued for a short period.
The Human Leukocyte Antigen HLA are proteins or markers that are present on the White blood cells and tissues of the body. HLA test, also known as HLA typing or tissue typing, identifies antigens on the WBCs that determine tissue compatibility for organ transplantation. These HLA markers are inherited from parents. This test is performed for kidney, bone marrow, liver, pancreas, and heart transplants. The transplant will be successful if HLA of donor closely matches with HLA of the patient. If the HLA of the donor and recipient do not match, the immune system of the recipient will assume the donor's HLA antigens as foreign. This causes rejection of the transplanted tissue or organ. This condition is called GVHD or Graft Vs Host disease. Recipients who receive mismatched transplant are at the highest risk of developing this condition. However, GVHD can occur even with proper HLA matching. HLA test also screens recipients for the presence of antibodies that might attack the transplanted tissue or organ as part of an immune response.
Though HLA typing is normally used to screen patients and donors for matching HLA antigens, it can also be undertaken for diagnostic purposes. The presence of HLA antigen B27 is explored to diagnose certain auto immune diseases like ankylosing spondylitis, reactive arthritis and anterior uveitis. HLA-DR15, HLA-DQ6 is associated with Narcolepsy.
Each HLA gene can have huge number of variations called alleles. There are 3 general groups of HLA that play an important role in matching prior to transplantation. They are the A, B and DR antigens. These are inherited from parents, one set of A, B and DR from mother and another set of A, B and DR from father. Thus there are two antigens for each letter and they are identified by different numbers.
HLA Test Process
HLA Test matches alleles of donors and recipients either by performing serological HLA testing or molecular (DNA) typing. Children from the same set of parents are likely to have the best HLA match possible. There is 1 in 4 chances that siblings will inherit the same genes from their parents. This is considered as ideal match.
Once the match has been identified, the next step would be to test for antibodies in the recipient. It is a vital step in HLA testing as antibodies have the potential to attack donor tissues that have the corresponding HLA type.
After testing for antibodies in the recipient, cross matching test is performed to identify donor specific antibodies. Cross matching is performed right before transplant. A cross match determines if the recipient's body contains antibodies formed against the potential donor's antigens. To perform the cross matching, a small amount of the recipient's serum is combined with the donor's white blood cells (T and B lymphocytes). If the recipient has antibodies that are specific to donors HLAs, the donors cells get damaged. This type of reaction is called positive cross match and indicates the incompatibility between recipient and the donor. A blood sample is needed to perform HLA typing. Testing is done using white blood cells and DNA. It takes about two weeks to receive the results.
Bibliography / Reference
Collection of Pages - Last revised Date: October 18, 2017