12.9.15 VA Ambulatory Report Pearls – Tremors, Fasciculations, and EMGs

The pearls could be endless with this case (!) but we will focus on the following tidbits:

Suggested top 5 features to elicit for a chief complaint of tremor

  1. When does it occur? For example, is it only at rest versus positional (e.g., standing only).
  2. Are there specific actions that cause the tremor to occur or worsen? For example, it only occurs with extension of the arm.
  3. Are there exacerbating or alleviating features? For example, commonly we think of improvement in an essential tremor with the use of alcohol.
  4. Are there associated symptoms? For example, is it associated with gait instability or ROS c/w hyperthyroidism.
  5. What is the laterality and location of the tremor?

Evaluating tremors on exam

We discussed the difference between frequency and amplitude of a tremor.

You can consider the frequency (measured in Hz and is movements per second) as the rapidity of the tremor. An example given was when we are anxious or awaiting something exciting, we may have a “fast” tremor of our hand which would be considered a high frequency tremor.

The amplitude of the tremor can be high, low, or variable. We discussed that one could think of this as the change in height or delta of the tremor.

How do we distinguish tremors vs fasciculations?

We discussed that tremors are rhythmic movements across joints or involving multiple body parts versus fasciculations which are isolated to the muscle itself (result from the action of a single motor unit that innervates muscle fibers).

Check out an example of fasciculations here. Note the hand is still and the muscle is contracting:

https://www.youtube.com/watch?v=sVgQS_6iUGE

I just ordered an EMG? What are the results going to mean?

EMG involves both an EMG and a nerve conduction study and you will receive a report documenting both of those different studies in an “EMG” study.

EMG Portion

Study to evaluate electrical activity of muscle fibers both individually and collectively.

There are four stages to testing:

  1. Muscle activity upon insertion of the needle electrode into the muscle. Insertion of the electrode typically results in bursts of activity due to mechanical irritation. If these bursts continue, that is abnormal.
  2. Spontaneous activity of the muscle at complete rest. One can identify myotonic discharges, fibrillations, and fasciculations at this stage.
  3. Analysis during minimal voluntary contraction.
  4. Analysis during increasing voluntary muscle contractions to maximal levels.

The take home: It can differentiate between a primary muscle process versus a motor nerve process.

Nerve Conduction Portion

The nerve conduction study evaluates summated electrical activity of individual nerve fibers. It evaluates conduction speed/velocity and amplitude/strength of the signal.

We discussed that the finding of a conduction block can occur with acquired demyelinating lesions. For example, if conduction speed and amplitude were measured at point A, point B, and point C then a conduction block would be when the signal from A to B is dropped.

The take home: The primary feature of axonal degeneration is reduced amplitude/strength of the signal from point A to point B. Speed/velocity decreases in primary myelin process.

Want more?

Shoutout to Manuel Diaz for passing on this gem of a resource. Neuroanatomy page a la University of Wisconsin where you can find approaches to common neurologic complaints and conditions as well as a video library on neurologic findings on exam or the approach to specific maneuvers. It is a great teaching resource!

http://www.neuroanatomy.wisc.edu/anatomy.htm

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