Ask Elan Louis, MD, what drew him to the study of essential tremor, and he thinks about the patients he saw during his residency whose arms and hands would start shaking uncontrollably whenever they wanted to unlock a door, pour a glass of water, or type a letter.
“It seemed to me that something in the brain must be really wrong to produce such repetitive, involuntary tremors,” Louis says, “but at the time nobody knew what it was.”
Louis started with a project on how essential tremor runs in families and quickly realized that nothing was really known about the disorder at all. “And what little knowledge there was, has turned out to be wrong,” he adds.
Louis’ studies have found that essential tremor, once thought uncommon, is actually the most common neurological movement disorder, perhaps 20 times more prevalent than Parkinson’s disease (tremors in Parkinson’s disease occur when limbs are at rest; tremors in ET occur when the limbs are in use). About 7 to 10 percent of people between age 60 and 80, and 20 percent of nonagenarians, have the disorder.
A decade ago, doctors thought tremor was the only symptom of the disorder and would often dismiss others as signs of old age. But based on studies by Louis and his colleagues, doctors now know that ET patients are more likely to have mild cognitive problems and experience difficulties with gait and balance that lead to falls.
And post-mortem studies of the brains of ET patients, conducted with pathologist Phyllis Faust, MD, PhD, have now revealed essential tremor’s probable source in the brain’s Purkinje cells.
“The brain studies have really changed the field,” Louis says. “We’ve gone from not knowing what part of the brain is affected to knowing the cells involved.”
None of these studies has led to a new treatment for ET, but Louis says that may change soon as the focus of research concentrates on the genes, molecules, and possible environmental factors involved.
“It’s an exciting time for the field, because if we can find changes at the molecular and genetic level,” Louis says, “that’s when we can start thinking about new treatments.”