1. Essential Tremor: Red Flags/Epidemiology
Part 2 of 7

2. Core Criteria for Identifying ET
1. Bilateral action tremor of the hands and forearms (but not rest tremor)
2. Absence of other neurologic signs, with the exception of the cogwheel phenomenon
3. May have isolated head tremor with no abnormal posture
General guidelines for identifying ET are presented in the next three slides. These core criteria, secondary criteria, and so-called “red flags” assist clinicians in making a correct diagnosis.
Basic core criteria include...
Bilateral action tremor of the upper limbs—but not rest tremor
Absence of other neurologic signs, with the exception of cogwheel phenomenon*
Possible presence of isolated head tremor with no abnormal posturing
*In patients with ET, although muscle tone is typically normal, there may be a brief, rhythmic increase in muscle resistance during passive movements of a limb about a joint.

3. Secondary Criteria for Identifying ET
1. Long duration (>3 years)
2. Family history
3. Beneficial response to ethanol
Although not required, helpful secondary criteria for identifying ET may include symptom duration longer than 3 years, positive family history, and suppression of tremor in response to ingestion of ethanol.
Symptom duration
Symptom duration longer than 3 years is an inclusion criterion for probable ET; however, a shorter duration should not be exclusionary. ET may be present soon after symptom onset, such as in some middle-aged patients and relatively young members of affected kindreds.
Family history
It is widely reported that approximately 50% or more of ET patients have a positive family history for tremor. The disparity of statistically significant epidemiologic mean values for ET varies greatly from about 17% to 100% as in community-based versus retrospective studies. Familial and sporadic cases of ET usually present clinically identical.
Investigators suggest that some cases may be inappropriately designated as sporadic due to lack of recognition of a positive family history. Although some researchers refer to family history within classification schema for ET, investigators within the TRIG and MDS avoid including a positive family history as core diagnostic criteria.
Ethanol consumption
Consuming even a small quantity of alcohol leads to transient improvement in about 70% of ET patients. This therapeutic effect is considered characteristic of ET. However, in rare cases, patients with other tremor types may experience similar effects.

4. Red Flags
1. Unilateral tremor, focal tremor, leg tremor, gait disturbance, rigidity, bradykinesia, rest tremor
2. Sudden or rapid onset
3. Current drug treatment that may cause or exacerbate tremor
4. Isolated head tremor with abnormal posture (head tilt or turning)
A number of so-called “red flags” often assist clinicians in excluding a diagnosis of ET. These include confirmation of unilateral tremor; focal tremor, such as tremulous cervical dystonia; leg tremor; gait disturbances; rest tremor; rigidity; or extrapyramidal signs, such as bradykinesia. The presence of rigidity, bradykinesia, or resting tremor is suggestive of PD.
Additional red flags include a sudden or rapid onset, current or recent therapy with tremorogenic agents, or the presence of isolated head tremor with abnormal posturing, such as head turning or chin tilting.

5. Epidemiology: Case Ascertainment
Patients may not seek medical evaluation if…
Tremor is mild; associated with no functional disability; accepted as a part of life
Improperly attributed to “old age”
Associated social disability from tremor is not taken seriously
Patients are unaware that effective treatment options are available
ET is one of the most common neurologic movement disorders. In addition, the frequency of ET appears to be independent of race or gender and increases with age. Although the disorder may become apparent during childhood or adolescence, onset typically occurs during adulthood, at a mean of about age 45 years.
Approximately 5 million Americans are diagnosed with ET. However, in spite of causing significant functional disability leading to possible handicap, the disorder frequently goes undetected. Some patients fail to seek medical attention if the tremor is mild. Patients may also be unaware of the availability of effective treatments; improperly attribute tremor to advancing age; or fear that the impact of tremor on their quality of life will not be taken seriously.

6. Challenge to determine true frequency of ET in general population due to...
Variation in the clinical criteria
Lack of consensus on the definition of ET
Difficulty in differentiating between mild forms of ET and exaggerated physiologic tremor (EPT)
Difficulties in classifying tremor when it is associated with other conditions (e.g., dystonia and parkinsonism)
Additional difficulties in epidemiologic studies of ET include variations in clinical criteria used in such investigations, use of different definitions of ET and different screening instruments, difficulties in differentiating between mild ET and enhanced physiologic tremor, as well as difficulties in categorizing tremor when it is coexistent with other neurologic conditions or comorbidities.
Prevalence estimates have varied widely among previous epidemiologic studies. To ascertain the frequency and range of expression of ET in the general population, additional prospective, community-based investigations are required, utilizing uniform diagnostic criteria. However, validating the accuracy of diagnostic criteria for ET will only be possible upon identification of the precise genetic marker.

7. Rajput: Incidence of ET
Despite the wide variability of prevalence estimates among past epidemiologic studies, all illustrate that ET is a common movement disorder that increases in frequency with advancing age.
For example, Rajput and colleagues reported on the second epidemiologic study of ET in the United States. Rajput’s retrospective study was based on review of original medical records of residents from Rochester, Minnesota over a 45-year period. Based on these data, the estimated prevalence of ET in the total population was 0.31%, with an increased rate of diagnosis after age 49.
Brin M, Koller W. Epidemiology and genetics of essential tremor.
Mov Disord 1998;13 (Suppl 3):55-63.

8. Rajput: ET in Rochester, MN, USA
1935 to 1979 (45-year study)
Age at Dx: mean of 58 (2 to 96 years)
Incidence: 23.7/100,000 (M=F)
Prevalence: 305.6/100,000
Cervical dystonia in 3%
Subsequent PD diagnosis in 2%
Family history of tremor in 39%
Mean age at diagnosis for ET was 58, with a range from 2 to 96 years. For the US Caucasian population, incidence rate—gender and age adjusted for 1964 to 1979—was 23.7 per 100,000. The prevalence rate— gender and age adjusted for 1970—was an estimated per 100,000. In fact, there was no significant difference in the annual incidence rate among females and males, with a frequency of 17.1 females per 100,000 and 18.3 males per 100,000.
Thirty-nine percent of patients had a family history of tremor. Data also revealed that coexistent cervical dystonia was diagnosed in 3% of patients. Although PD was subsequently diagnosed in 2%, these findings were considered incidental.
Rajput AH, Offord KP, Beard CM, Kurland LT. Essential tremor in Rochester, Minnesota: a 45-year study. J Neurol Neurosurg Psychiatry. 1984;47:

9. Salemi: Prevalence of ET
Salemi and colleagues conducted a door-to-door neuroepidemiologic survey, during which they investigated the prevalence of ET in individuals residing in Terrasini, Sicily. The survey included screening of 7,653 residents for tremor, followed by clinical evaluation by neurologists for those patients who screened positively for tremor. Based upon fulfillment of specific clinical criteria, a diagnosis of ET was made in 31 subjects, including 17 men and 14 women. Of these patients, 35.5% or 11 subjects reported a family history of tremor.
Based upon these data, the prevalence of ET was per 100,000 or 0.4% for the total population. Prevalence increased to 1,074.9 per 100,000 or 1.1% for individuals aged 40 or older, demonstrating a significant age-related effect. Although prevalence increased with age for men and women, this increase was slightly higher for men.
Salemi G, Savettieri G, Rocca WA, et al. Prevalence of essential tremor: a door-to-door survey in Terrasini, Sicily. Neurology. 1994;44:61-64.

10. Age Onset Essential Tremor: New York
The age at onset in a sample of 470 ET patients evaluated in routine clinical practice is illustrated in this slide. The age of onset was determined during office consultation interviews.
The frequency of ET increases with advancing age, with onset typically occurring at a mean of about age 45. However, as demonstrated here, ET may become apparent at any age from infancy through late adulthood. In addition, for individuals of both genders, there appears to be a bimodality of age at onset.
Brin MF, Koller W. Epidemiology and genetics of essential tremor. Mov Disord ;13(Suppl 3):55-63.
Brin MF, Koller W. Epidemiology and genetics of essential tremor. Mov Disord ;13(Suppl 3):55-63.