Somatic Tremor (artifact) is caused by what?

• A. Muscle movement
• B. Electrical interference
• C. Baseline wander
• D. Calibration error

Answer: (A)

Somatic tremor is caused by muscle movement near the recording electrodes. When muscles contract, their electrical activity is picked up by the leads and appears as rapid, irregular spikes on the trace, often resembling small tremors. This artifact reflects the patient’s own muscle activity rather than the signal you’re trying to measure.

In contrast, electrical interference shows up as a steady line-frequency noise from power sources, and baseline wander is slow drift of the trace due to electrode impedance changes or breathing. Calibration error would shift or scale the entire signal rather than producing the characteristic tremor spikes. To reduce somatic tremor, have the patient relax and remain still, improve electrode contact and skin preparation, check impedance, and adjust shielding or filtering as needed.