Impact of clinical neurophysiological assessment on diagnosis and management of tremor disorders

Abstract

Objective: To assess the clinical utility of a standardized, non-invasive electrodiagnostic testing protocol in refining the diagnosis and management of patients referred for tremor evaluation.

Methods: In this prospective observational study, patients with tremulous limb movements with indeterminate clinical diagnoses involving tremor as a cardinal symptom were referred by movement disorders neurologists. Participants underwent standardized phenotyping and electrodiagnostic studies for tremor analysis including four-channel surface electromyography polygraphy and two-channel accelerometry.

Results: Clinical and electrophysiological data from 31 consecutive individuals were analyzed. Electrodiagnostic testing refined the differential diagnosis in 25/31 (80.6 %) participants and changed therapy in 14/29 (48.3 %). Changes included adjusting pharmacotherapy (n = 10), undergoing deep brain stimulation surgery (n = 2), or avoiding invasive procedures (n = 2).

Conclusions: We propose that electrodiagnostic testing is a clinically valuable tool that can narrow the differential diagnosis and impact treatment of tremor.

Significance: Clinical evaluation alone may be insensitive in diagnosing the tremor type when findings are subtle or when multiple movement disorders coexist. This may lead to inaccurate diagnosis and management, increasing cost and patient burden, and prolonging or preventing a successful journey towards adequate treatment. Clinical neurophysiology is a useful diagnostic procedure that can detect and quantify movements that may be otherwise indistinguishable by visual observation.

Keywords: Accelerometry; Electromyography; Electrophysiology; Movement disorders; Neurophysiology; Tremor.

Fig. 1

Sankey diagram showing differential diagnosis before electrophysiological tremor analysis and diagnosis after electrophysiological testing in 31 participants referred by movement disorders specialists for evaluation of indeterminate tremor syndrome. Multiple diagnoses may be included for each participant.

Fig. 2

Case 1 electromyography (EMG) and accelerometry recording from bilateral upper limbs during posture, 2.5-Hz tapping task (entrainment), and contralateral ballistic maneuvers. 0.2A. EMG recording during posture shows rhythmic movements and alternating muscle bursts in the right hand. 2B. Spectral analysis shows a 6.3 Hz right hand tremor and a small peak in the left-hand accelerometer that is likely transduction artifact from the large amplitude right hand tremor, since no tremor was observed clinically, and coherence was significant between both right and left accelerometers at ∼ 6.3 Hz but not significant between the right and left EMG.. Abbreviations: EMG: electromyography; L: Left; R: Right; Acc: accelerometer; FCU: flexor carpi ulnaris; EDC: extensor digitorum communis.

Fig. 3

Case 1 electromyography (EMG) and accelerometry recording from bilateral upper limbs during contralateral ballistic maneuvers and during 2.5-Hz tapping task (entrainment). 3A. EMG recording shows attenuation of right hand tremor (in posture) with left hand ballistic maneuvers. 3B.Spectral analysis of recording during entrainment task with right hand in posture and left hand tapping at 2.5 Hz shows a dominant frequency in the left hand at 2.5 Hz and dominant frequency in the right-hand accelerometer with EMG correlate at 2.5 Hz, demonstrating entrainment. The right-hand tremor amplitude is lower, demonstrating distractability. Coherence analysis between right and left EDC shows significant coherence at 2.5 Hz. Abbreviations: EMG: electromyography; L: Left; R: Right; Acc: accelerometer; FCU: flexor carpi ulnaris; EDC: extensor digitorum communis.

Fig. 4

Case 2 electromyography (EMG) and accelerometry recording from bilateral upper limbs during posture. 4A. EMG recording. 4B. Spectral analysis. During posture, both accelerometric frequencies were about 7 Hz, with EMG correlate (left hand about 7 Hz, right hand about 9 Hz). The amplitude of the left-hand tremor was 1–2 times greater than the right. Abbreviations: EMG: electromyography; L: Left; R: Right; Acc: accelerometer; FCU: flexor carpi ulnaris; EDC: extensor digitorum communis.

Fig. 5

Case 2 electromyography (EMG) and accelerometry recording from bilateral upper limbs during posture with weight-loading. 5A. EMG recording. 5B. Spectral analysis. During weight loading with 1.5 lbs. during posture, the left-hand accelerometer showed a 4.1-Hz mechanical component without EMG correlate and an 8.3 Hz central component with EMG correlate, and the right-hand accelerometer showed a 3.8 Hz mechanical component without EMG correlate and an 8.9 Hz central component with EMG correlate. The left EDC spectrum is artifact. Abbreviations: EMG: electromyography; L: Left; R: Right; Acc: accelerometer; FCU: flexor carpi ulnaris; EDC: extensor digitorum communis.

Fig. 6

Case 3 electromyography (EMG) and accelerometry recording from bilateral upper limbs at rest and during posture. 6A. Spectral analysis showed a 5.2 Hz rest tremor in the right hand. A 5.2 Hz tremor signal was also seen on accelerometry and surface EMG recordings in the left hand, but no tremor was observed visually. This signal detected from the left upper limb was most likely due to motion artifact from the large amplitude right upper limb tremor. 6B. During posture, there was a right-hand tremor with 5.9 Hz frequency. The left-sided accelerometer and EMG tracings showed a 5.9 Hz signal. Again, no tremor was observed visually in the left upper limb, so this signal from the left upper limb was most likely due to motion artifact. Abbreviations: EMG: electromyography; L: Left; R: Right; Acc: accelerometer; FCU: flexor carpi ulnaris; EDC: extensor digitorum communis.

Fig. 7

Case 3 electromyography (EMG) and accelerometry recording from bilateral during 2.5-Hz tapping and contralateral ballistic maneuver. 7A. During entrainment maneuvers with the left hand tapping at 2.5 Hz, the right-hand tremor frequency remained 5.6 Hz. 7B. There was no change in the right-hand tremor during contralateral ballistic maneuvers. Abbreviations: EMG: electromyography; L: Left; R: Right; Acc: accelerometer; FCU: flexor carpi ulnaris; EDC: extensor digitorum communis.