If you or a loved one has essential tremor (ET) you are all too familiar with the visible shaking of hands, head, voice, legs or trunk that characterize ET. No one knows what causes ET’s abnormal brain signals to start. Once it begins, most people with ET will experience worsening of their shaking over time. As a rule, however, the older a person is when ET starts, the more rapidly it seems to progress.

Involuntary, rhythmic shaking that occurs with intentional movement (e.g. reaching for a glass of water or engaging a zipper) is a motor (that is, movement) symptom of ET. At this time, there is no lab test or imaging scan that can identify ET, so diagnosis is based on motor symptoms – the tremors, which can be seen and measured – as well as family history, age of onset, what aggravates or lessens tremors, exposure to toxins, ruling out other tremor-causing conditions, etc. In fact, neurological evidence of a brain abnormality cannot even be found when tissue is examined microscopically on autopsy.ⁱ

Nonmotor symptoms

While physical symptoms are the primary diagnostic information, it’s important to note that ET also has nonmotor symptoms, that is, not related to movement. Since they are not evident to the eye, they might be thought of as “invisible.” At the time a doctor is evaluating for ET, he/she may not ask about or even observe nonmotor symptoms such as:

• Mild cognitive impairment (reduced executive function, impaired memory, attention deficits, etc.)
• Apathy
• Depression
• Anxiety
• Sleep disturbances
• Reduced quality of lifeⁱⁱ

Furthermore, just as individual patterns of tremors vary from one person to another, heterogeneous nonmotor symptoms may not manifest with every person. This raises questions regarding neurobiological abnormality as the cause of both motor and nonmotor symptoms vs. the emotional stress of living with tremors as the source of nonmotor symptoms. There are also questions as to whether nonmotor symptoms progress, and if so, is nonmotor degeneration biologically linked with tremor progression?

In “Non-Motor Symptoms of Essential Tremor Are Independent of Tremor Severity and Have an Impact on Quality of Life” the authors theorize that ET-related apathy, anxiety, depression and diminished quality of life are not so much a byproduct of the underlying biological abnormality in the brain as much as the interaction between having tremors and the person’s personality and life situation. To put it another way, developing anxiety, depression, etc. is an understandable response to life with tremor-related disability, but some people may cope better than others and have fewer nonmotor symptoms.

What’s important is recognizing the need to assess both motor and nonmotor symptoms when a person with tremors comes for help. Clear criteria need to be developed and defined, especially regarding neuropsychiatric or emotional distress, and its impact on a person’s quality of life.

At Sperling Neurosurgery Associates, we find that when an individual with ET undergoes noninvasive Focused Ultrasound that eliminates tremors in the dominant hand, distress is alleviated, and nonmotor symptoms quickly subside. While this does not rule out a biology-based explanation for apathy, depression or anxiety, it certainly supports the evidence that without tremors, quality of life improves by a quantum leap when nonmotor symptoms truly become invisible – for life.

For more information on MRI-guided Focused Ultrasound to control ET, visit our website.

ⁱKlaming R, Annese J. Functional anatomy of essential tremor: lessons from neuroimaging. Am J Neuroradiol. 2014 Aug;35(8):1450-57.

ⁱⁱFois AF, Briceño HM, Fung VSC. Nonmotor symptoms in essential tremor and other tremor disorders. Int Rev Neruobiol. 2017;134:1373-96.