Diagnosing functional tremor: positive signs on exam

Functional tremor can change in frequency or shift from one body part to another. Three patient presentations illustrate how those changes, along with how the tremor began and what happens with distraction, help distinguish functional tremor from essential tremor and Parkinson’s disease.

In this lesson from our Tremors Masterclass course you'll learn how to:

• Compare sudden and gradual tremor onset
• Identify distractibility using serial 7s
• Assess variability in tremor location and frequency
• Recognize entrainment during rhythmic tapping
• Use positive exam findings to support a diagnosis of functional tremor

Functional tremor differential diagnosis

[0:00]
Now that you know the signs of functional tremor, in this Medmastery lesson, I'll teach you how to use that information to distinguish functional tremor from other conditions like essential tremor and Parkinson's disease. Let's review some patient cases.

Case 1: a consistent action tremor

[0:17]
Andrew is a 60-year-old with a consistent tremor in both hands. It's especially noticeable when he tries to hold objects or perform tasks like writing. The tremor is minimal when he's relaxed, but increases in intensity when he's using his hands. Its frequency remains consistent when you ask him to tap his right foot.

Case 2: a variable and distractible tremor

[0:39]
Sarah is a 35-year-old with no significant medical history. She reports a tremor in her right hand that started suddenly six weeks ago. The intensity of her tremor varies throughout the day, but is present both when her hand is relaxed and when she uses it. It's more pronounced when she's anxious and when she focuses on it, the tremor will sometimes move to her right leg. When you ask her to perform Serial 7s, where she subtracts 7 from 100 repeatedly, the tremor disappears. When she stops the task, it reappears. When you ask her to tap her left hand on her lap, her right hand tremor matches the rhythm of her left hand tapping.

Case 3: a unilateral rest tremor

[1:21]
Lastly, Mary is a 70-year-old who gradually developed a tremor in her left hand. It's noticeable when her hand is resting in her lap or when she's walking. She also noticed that her left leg drags slightly when she walks. She has no tremor when she's using the hand. When she performs Serial 7s, the left hand tremor worsens. She doesn't have tremor elsewhere, and the frequency of her tremor stays the same when you ask her to tap her right hand.

Which patient has functional tremor?

[1:53]
So which patient's presentation is most consistent with functional tremor? Pause the video and think about the answer before continuing. If you suspect that Sarah has functional tremor, then you're correct. Andrew's presentation is more consistent with essential tremor, and Mary most likely has Parkinson's disease. Let's talk about why.

Sudden onset of functional tremor

[2:16]
The first sign that points to a functional tremor is a sudden onset that reaches maximal severity quickly. In Sarah's case, her tremor started one day and caused disability within six weeks, a progression more consistent with functional tremor. On the other hand, the tremor seen in Parkinson's disease or essential tremor typically has a gradual onset, which is what we see with Mary and Andrew. Next, remember the three tremor pattern characteristics that highly suggest functional tremor? Distractibility, variability, and entrainment.

Distractibility and serial 7s

[2:54]
Distractibility is a key feature of functional tremors. In Sarah's case, her tremor goes away when she performs serial 7s. In contrast, essential or Parkinson's tremors tend to persist and often worsen with distraction. For example, Mary's tremor gets worse when she performs Serial 7s.

Variability in functional tremor

[3:19]
On to variability. A functional tremor is variable, like Sarah's, and is often a mixed rest and action tremor. Sarah's tremor affects her hand, but sometimes moves to her leg. In Parkinson's disease or essential tremor, the tremor's distribution and frequency are consistent, like in Andrew's case. It doesn't affect one body part one day and then move to another body part the next day. Any observation of variability in the body part affected or in frequency is a positive sign for functional tremor.

Entrainment in functional tremor

[3:55]
Entrainment is also a defining feature of functional tremor. In Sarah's case, when you ask her to tap her left hand on her lap, her right hand tremor matches the rhythm of her left hand tapping. In contrast, the frequency of Andrew and Mary's tremors remains consistent with tapping maneuvers of other body parts.

Positive signs of functional tremor

[4:16]
So a functional tremor should be suspected when the tremor has a sudden onset and becomes severe quickly. A history of tremor affecting different body parts or suddenly involving the whole body should also make you suspect functional tremor. And remember distractibility, variability, and entrainment. If any of these positive signs are present, then you can make a diagnosis of functional tremor. Functional tremor isn't a diagnosis of exclusion, meaning you don't have to rule out other conditions first.