Causes and Symptoms
What causes these diseases?
Symptoms of Batten disease/NCLs are linked to a buildup of substances called lipopigments in the body's tissues. These lipopigments are made up of fats and proteins. Their name comes from the technical word lipo, which is short for “lipid” or fat, and from the term pigment, used because they take on a greenish-yellow color when viewed under an ultraviolet light microscope. The lipopigments build up in cells of the brain and the eye as well as in skin, muscle, and many other tissues. Inside the cells, these pigments form deposits with distinctive shapes that can be seen under an electron microscope. Some look like half-moons (or commas) and are called curvilinear bodies, others look like fingerprints and are called fingerprint inclusion bodies and still others resemble gravel (or sand) and are called granual osmophilic deposits (grods). These deposits are what doctors look for when they examine a skin sample to diagnose Batten disease.
The diseases cause death of neurons (specific cells found in the brain, retina and central nervous system). The reason for neuron death is still not known.
How are these disorders diagnosed?
Because vision loss is often an early sign, Batten disease/NCL may be first suspected during an eye exam. An eye doctor can detect a loss of cells within the eye that occurs in the three childhood forms of Batten disease/NCL. However, because such cell loss occurs in other eye diseases, the disorder cannot be diagnosed by this sign alone. Often an eye specialist or other physician who suspects Batten disease/NCL may refer the child to a neurologist, a doctor who specializes in disease of the brain and nervous system. In order to diagnose Batten disease/NCL, the neurologist needs the patient's medical history and information from various laboratory tests.
Diagnostic tests used for Batten disease/NCLs include:
- Skin or tissue sampling The doctor can examine a small piece of tissue under an electron microscope. The powerful magnification of the microscope helps the doctor spot typical NCL deposits. These deposits are found in many different tissues, including skin, muscle, conjunctiva, rectal and others. Blood can also be used.
- Electroencephalogram or EEG An EEG uses special patches placed on the scalp to record electrical currents inside the brain. This helps doctors see telltale patterns in the brain's electrical activity that suggest that a patient has seizures.
- Electrical studies of the eyes These tests, which include visual-evoked responses (VER) and electro-retinagrams (ERG), can detect various eye problems common in childhood Batten disease/NCLs.
- Brain scans Imaging can help doctors look for changes in the brain's appearance. The most commonly used imaging technique is computed tomography (CT), which uses x-rays and a computer to create a sophisticated picture of the brain's tissues and structures. A CT scan may reveal brain areas that are decaying in NCL patients. A second imaging technique that is increasingly common is magnetic resonance imaging, or MRI. MRI uses a combination of magnetic fields and radio waves, instead of radiation, to create a picture of the brain.
- Enzyme assay A recent development in the diagnosis of Batten disease/NCL is the use of enzyme assays that look for specific missing lysosomal enzymes for Infantile and Late Infantile forms only. This is a quick and easy diagnostic test.