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Table 3 Clinical features of organic tremor evaluated and described in studies

From: Diagnosis and therapy of functional tremor a systematic review illustrated by a case report

Clinical features
A typical feature of PMD is its paroxysmal nature and a sudden onset of the symptoms with no progression [16]
The symptoms are (almost) maximal at or near onset [16]
The tremor can have different directions and change them over time, this can especially be seen in mass loading testing ([2, 16, [20])
Frequency analysis can help to differentiate between organic and functional tremors. Based on a classification of frequency into low (< 4 Hz), medium (4–7 Hz) and high (> 7 Hz) tremors with frequency > 11 is usually organic, but there is no rule with lower frequencies. Essential tremor is often 6 or 7 Hz, many tremor frequencies were suggested between 6 and 11 Hz to be often functional ([1, 2, 16, 20])
The amplitude, frequency as well as direction show a higher variability in functional tremor than in organic forms, usually the frequency of organic tremor does not show a variation higher than 0.5 to 1.0 Hz, in functional tremor a larger variation in frequency may be observed ([1, 2, 16, 20])
Tremor shows different reactions to distraction and can cease or vary in intensity or frequency ([16, 20])
In an entrainment test, the tremor takes up the frequency of a tapping in an unaffected extremity e.g. finger tapping ([16, 20])
Often functional tremor can be precipitated by suggestion [16]
Impaired walking and standing without a tendency to fall is often detected in functional tremor, meaning swaying gait and apparent balance problems without falling [16]