Understanding Physical Exam Findings Associated With FND - Part 1

In part one of this four-part series, Casey Kozak breaks down tremors observed during the physical examination of FND. 

Show transcript: 

Casey Kozak:

Welcome back to Neurology Minute. This is Casey Kozak with Rutgers, and today we'll be discussing a very important and evolving topic, that is Functional Neurological Disorder, or FND. If you're a regular fan of the Minute, you'll have already heard a great miniseries on FND by Jon Stone and Gabriela Gilmour, which focuses on diagnosis and treatment. If you haven't listened yet, I encourage you to check it out. In this series, we're going to focus in on physical exam findings associated with FND to help you excel on the floors.

Talking about the physical exam, it's important to keep in mind that FND looks different for every patient. However, some general characteristics of symptoms may include inconsistency, variability, selectivity of impairment, meaning mismatch of impairment with different tasks, distractibility, suggestibility, and incongruence with symptoms seen in other neurological disorders. Since tremors are one of the most common presentations of FND, we'll start there.

Even while taking their history, you may notice features consistent with FND. And in fact, this is a great time to make natural observations of the patient and their symptoms. Unlike tremors associated with degenerative movement disorders like Parkinson's, functional tremors may exhibit variability of frequency and amplitude, especially during periods of shifted attention. You can further evaluate the tremor using the entrainment test. To perform the entrainment test, ask the patient to make a tapping motion. As the patient taps, look for a change in frequency in their tremor. The frequency of the tremor may begin to match the frequency of the patient's tapping. Any change in the tremor while the patient is tapping is considered a positive finding.

Alternatively, you can also test the whack-a-mole sign. To elicit the whack-a-mole sign, the examiner holds down the tremulous body part while looking for the emergence of a tremor in a different body part. This finding is consistent with a functional tremor, as tremors related to neurodegenerative diseases do not jump limbs. Let's break now to practice. Join us again for our next episode where we will turn to functional weakness. See you then.