Although commonly seen in family medical practice, essential tremor may be difficult to diagnose and equally challenging to treat. Some patients may wait up to 20 years before seeking appropriate medical evaluation for their worsening symptoms. ET is a clinical diagnosis; there is no definitive test for essential tremor. Since most people with ET benefit somewhat from drug therapy, early diagnosis and prompt, appropriate treatment may delay or eliminate functional disability. Essential tremor is best diagnosed by a physician who has experience with tremor and movement disorders.
It is possible to measure tremor and assess its impacts on patients in a variety of ways. These include electrophysiologic techniques (e.g., EMG, accelerometer, spectral analysis, and weighting of the body part), clinical rating scales (e.g., tremor scale [see below]), and simple objective tests of hand and arm functions. The results of patient interviews and responses to questionnaires help to measure total disability, resultant handicap, and impact on quality of life.
Several tremor classification scales have been proposed to assist physicians to distinguish between the different types of tremor, such as action and resting tremors and other variants and to appropriately diagnosis the type of tremor (e.g., probable or possible ET, classic ET, etc.). These proposed classifications include Collaborative Clinical Classification of Tremor (which includes distinction between tremor types, data from medical history, and results of neurologic evaluation) and the Tremor Research Investigation Group (TRIG) Classification of Essential Tremor (which has inclusion and exclusion criteria for definite, probable, and possible ET).
Clinical evaluation is typically based on a thorough medical history and assessment of the patient's symptoms including:
Various methods may be used to evaluate the different aspects of ET. These include physiologic techniques, clinical assessments, and functional performance tests. For example, the physiologic aspects of hand tremor may be measured using a specialized device known as an accelerometer. During such testing, the device is attached to the underside of the index finger of the hand. The resulting tremorgram records the frequency and amplitude of the tremor. The frequency of ET varies from 4 to 12 Hz.
The severity of arm tremor may be clinically assessed by using a clinical rating scale and by scoring tremor in Archimedes spirals. Tremor and associated disability seems to increase with advancing age and increasing tremor duration. It is possible that the frequency of ET may decrease with advancing age; however, the amplitude of the tremor may increase, leading to increased disability. In addition, there seems a direct correlation between age at tremor onset and either tremor severity or disability.