Functional jerks, tics, and paroxysmal movement disorders.

Area of Science:

• Neurology
• Movement Disorders
• Neuroscience

Background:

• Functional jerks are a prevalent type of functional movement disorder.
• Diagnosis relies heavily on specific clinical signs identified during neurologic examination.
• Distinguishing functional jerks from similar conditions like tics, organic myoclonus, and primary paroxysmal dyskinesias presents diagnostic challenges.

Purpose of the Study:

• To delineate the key features of functional jerks.
• To outline diagnostic criteria for functional jerks.
• To provide a comprehensive differential diagnosis for functional jerks.

Main Methods:

• Clinical examination and identification of positive signs.
• Assessment of phenomenology (onset, variability, complexity).
• Evaluation of suggestibility, distractibility, and entrainment.
• Consideration of neurophysiologic tests like Bereitschaftspotential.

Main Results:

• Functional jerks often present with acute onset in adulthood, triggered by physical events, and exhibit variable, complex phenomenology.
• Key differentiating features from tics include the absence of an urge, later onset, and lack of specific family history or comorbid psychiatric symptoms.
• Distinguishing from organic myoclonus involves movement localization, onset, phenomenology consistency, and medication response.
• Primary paroxysmal dyskinesias are differentiated by family history and consistent symptom patterns on video recording.

Conclusions:

• Accurate diagnosis of functional jerks necessitates a thorough evaluation of clinical signs, symptom characteristics, and patient history.
• Understanding the differential diagnoses, including tics, organic myoclonus, and primary paroxysmal dyskinesias, is crucial for appropriate management.
• Neurophysiologic findings can support the diagnosis and differentiation of functional jerks.