The following is an excerpt from the last portion of the article that addresses Mitochondrial Disease:
"Mitochondrial Diseases: Damage to the Brain
Of all the neuromuscular diseases covered in MDA’s program, those that have to do with the mitochondria — the tiny energy-producing units tucked inside human and animal cells — are perhaps the most mysterious, confusing and challenging for physicians and families.All cells and the tissues in which they’re located require energy to function, but some tissues — such as the brain and muscles — require more energy than others. That’s probably why defects in mitochondrial function hit these areas hard.
There are several types of mitochondrial diseases, and they all have different characteristics. What’s even more confusing is that even when a mitochondrial disease runs in a family, various family members can have different symptoms or degrees of severity, even though their mitochondrial flaw may be the same. Neuromuscular disease specialist Tim Miller at Arizona Health Sciences Center in Tucson says it isn’t so much the mitochondrial defect itself that makes the difference in cognitive functioning. Instead, as with the congenital muscular dystrophies, it’s the presence or absence of severe seizures, as well as two other aspects of mitochondrial disease — strokes and high levels of lactic acid in the blood.
“Seizures are a major factor,” Miller says. “For kids with underlying mitochondrial changes, you have to worry, because seizures can damage things even worse.”
Fortunately, Miller says, seizures can often be adequately controlled with medication. But these medications can themselves cause some side effects, which can include sleepiness, confusion, memory problems and trouble with vision. The benefits and side effects have to be carefully weighed by the doctor and parents and the dose meticulously monitored.
Strokes or “strokelike episodes” occur in some children with mitochondrial diseases. A “stroke” is the term for an interruption of blood supply to the brain, with resulting brain damage, either temporary or permanent. Strokes can be caused by either abnormal bleeding in the brain or an obstruction to blood flow in the brain.
“There are probably changes in the brain’s blood vessels,” Miller says. “We know that mitochondrial dysfunction can affect blood vessels.” (Other experts say strokelike episodes may sometimes be seizure-related.) Unfortunately, there’s little that can be done to prevent or control these episodes.
When mitochondria don’t produce energy for cells in the usual way, energy-producing pathways are altered, leading ultimately to the buildup of lactic acid. When enough of this chemical gets into the blood, it changes the blood’s acidity level, which leads to a host of unwelcome changes in body chemistry. This lactic acidosis isn’t good for the brain, causing a variety of cognitive symptoms.
“The body maintains a very strict level of acids and bases,” Miller says. “Any time that level is affected, it can affect thinking.”
Miller says a medication called lactulose (brand names Constilac, Chronulac and others) can sometimes be used effectively to draw off some of the acid into the intestines, but that the best approach may be to try to prevent lactic acid buildup from occurring in the first place.
Making sure the child’s respiratory function is adequate, preventing or promptly treating infections, and maintaining good nutrition can all help prevent lactic acidosis, Miller says.
“When kids are challenged with something like an infection, that may make it more difficult for them to stay in [metabolic] balance,” he says. Parents have to be on the lookout for signs of infection and for cognitive symptoms that suggest lactic acid may be building up. Diminished concentration, diminished talking, confusion and irritability are among those symptoms.
The brain’s vision-processing cells, as well as the retina at the back of the eye and the muscles that control eye movements, can all be affected in mitochon-drial diseases, so vision can be a problem.
Vision therapy may be helpful, as can assistive technology such as adapted computer screens and computer-operating devices.
Hearing can also be affected, and some children need hearing aids and/or devices to help them communicate.
Children with mitochondrial diseases and their families often need referrals to hearing and speech specialists, vision specialists, respiratory doctors and therapists, educational specialists, and social workers or counselors. (Ask about these specialists at your MDA clinic and through the public school system in your area.)"
