[Differential Diagnosis of Trembling]

Trembling/shaking is among the most common complaints encountered in general or neurological clinics. The differential diagnosis of this symptom is important as it can be caused by various conditions and neurological diseases. Essential tremor (ET) is a dominantly inherited disorder that manifests as a bilateral fine (>8Hz) postural tremor. Physiological tremor can develop in patients with sympathetically activated conditions, such as hyperthyroidism, fever, anxiety, and muscle fatigue, in addition to being induced by many drugs. Patients with Parkinson's disease may demonstrate lateralized, moderately fast (4-6Hz) resting and postural tremors. Rubral (midbrain) tremors in the arms with low frequency (3Hz) oscillation or palatal myoclonus may suggest lesions within the Guillain-Mollaret's triangle, which comprises the contralateral midbrain rubral nucleus, contralateral medullary inferior olivary nucleus, and ipsilateral cerebellar dentate nucleus. Intension (terminal) tremor is defined as an action tremor showing an amplitude increases towards the end of the movement to touch a target, as in the finger-nose-finger test. Orthostatic tremor (also termed shaky legs syndrome) is a variant of ET involving the legs observed only in the standing still position. In conclusion, a precise diagnosis of symptoms allows the management of the condition according to its causal mechanism.