“Variety is the spice of life.” How often in your life did you hear those words? They first appeared in a 1785 poem by William Cowper, a popular 18th century poet who also wrote words to many hymns. He was also an ardent supporter of the anti-slavery movement of his time. It’s true that the human brain relishes diversity of experience. Variety makes life interesting. We are entertained, stimulated, amused…anything but bored. Consumers thrive on increasing variety. For instance, think about table salt. When I was young, we had white salt and black pepper on the table. The choices were limited. Today, there are at least 12 different kinds of salt commonly available, and the range of colors is surprising. Such diversity is truly the spice of life!
Variety of tremors
Does it surprise you to learn that tremors are a universal condition? Everyone has them, but in their natural state they are undetectable. They normally can’t be seen or felt, and are called physiologic tremors. They may become more pronounced in times of anxiety, fatigue, or great physical effort, but they generally fade away as the situation calms down.
On the other hand, tremors can be a symptom of an abnormal condition. There are many conditions, including troubling diseases such as Parkinson’s disease, that come with uncontrollable shaking of hands, head, voice, trunk or legs. Not all tremors are alike, so there have been many attempts to sort them into types based on their characteristics.
It is generally accepted that there are six main types of tremors.
- Resting tremor occurs when the affected body part is not active and is supported against gravity. For example, persons with Parkinson’s may have trembling hands even when they are just lying on a tabletop.
- Action tremor occurs during voluntary muscle activation, and includes essential tremor (ET) as well as other conditions.
- Postural tremor occurs while the affected limbs are voluntarily maintained against gravity, such as when the patient extends the arms forward in front of the body. ET, along with several other conditions, can manifest as postural tremors.
- Kinetic tremor occurs in both goal-directed and non goal-directed movements, as typically seen during the finger-to-nose-to-finger test in a neurological exam. This is also typical of ET.
- Intention tremor is characterized by an increase in tremor amplitude as the target is approached, as many with ET experience.
- Task-specific tremors occur during isolated tasks such as Primary Writing Tremor, and there are differences of opinion as to whether writing tremor is ET or something else.
Other ways to characterize tremors
Tremors can also be described based on their properties of amplitude and frequency.
- Amplitude means the range of motion. Think of a playground swing. If no one is in it and a wind comes up, it will be begin to sway as it dangles. In a gentle breeze it will act like a pendulum with a limited range of motion. But if a passing child walks up to it and gives it a hard push, the arc of its motion will have greater width back and forth. That’s the amplitude.
- Frequency is now many times something occurs within a specified amount of time. The faster the motion of the swing, the more times per minute it will swing from one end to another.
Thus, there are tremors that are low amplitude/low frequency (short range and slow speed); low amplitude/high frequency (short range and fast speed); high amplitude/low frequency (wide range and slow speed); and high amplitude/high frequency (wide range and fast speed).
When you think about the variations that can occur with tremors, it’s clear that diagnosing the underlying condition or disease may be somewhere between a science and an art. Even when a neurologist has diagnosed a person as having ET, one person’s ET is not identical with another’s. There is much room for variation.
Sperling Neurology Associates is proud to offer a treatment called Neuravive that can literally free a person from his or her tremors. Neuravive uses MRI-guided Focused Ultrasound (MRgFUS), a noninvasive intervention that stops tremors at their source in the brain. No cutting or drilling, no radiation, no more dependence on medications. For more information, or to set up a consultation, visit Sperling Neurosurgery Associates.