Postural And Intention Tremors: A Detailed Clinical Study Of Essential Tremor Vs Parkinsons Disease
- 1Gertrude H. Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA
- 2Tufts University School of Medicine, Boston, MA, USA
- 3Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
- 4Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, Columbia University, New York, NY, USA
- 5Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA
Background: An estimated 30–50% of essential tremor diagnoses are incorrect, and the true diagnosis in those patients is often Parkinson’s disease or other tremor disorders. There are general statements about the tremor in these ET and PD, but published data on the more subtle characteristics of tremor are surprisingly limited. Postural tremor may occur in both disorders, adding to the difficulty. There are several anecdotal impressions regarding specific features of postural tremor in ET vs. PD, including joint distribution , tremor directionality , and presence of intention tremor. However, there is little data to support these impressions.
Methods: In this cross-sectional study, 100 patients underwent detailed videotaped neurological examinations. Arm tremor was rated by a movement disorder neurologist who assessed severity and directionality across multiple joints.
Tremors May Be Nothing To Worry About Or Something More Serious But Don’t Let Them Go Unchecked
Do you ever notice that you can’t seem to hold a coffee cup still? Or that your hands sometimes tremble so much it interferes with daily chores? Those involuntary hand movements are called tremors. “They’re common in middle and older age,” says Dr. Chizoba Umeh, a neurologist who specializes in movement disorders at Harvard-affiliated Brigham and Women’s hospital. “They’re not life-threatening, but people with severe tremors may have a hard time feeding themselves, dressing, or driving.”
Tremors In Parkinsons Disease: What They Are Types Of Tremors And More
Getting the trembling associated with Parkinson’s under control can be a challenge, but treatments can help.
Tremors are a defining characteristic of Parkinson’s disease, affecting about 8 out of 10 people with this movement disorder. Many people think the involuntary shaking motion is the main problem for patients. While it is certainly an irritating symptom that individuals want to get under control, other characteristics of the disease can be more debilitating.
What Is A Tremor And What Makes It Different With Parkinsons
Tremor is an uncontrollable, rhythmic muscle contraction that triggers quivering in one or more parts of the body. It often occurs in hands, arms, or legs but can also affect the head, neck, or torso. This shaking may appear in sporadic spells or continue constantly.
The National Institute of Neurological Disorders and Stroke says that age is a risk factor — middle-aged and older adults are more likely to experience tremors.
Misperception #3: The Tremor Of Et Is Bilateral & Symmetric
Action tremor in patients with ET is usually, though not always, bilateral, and it is typically asymmetric . In a community-based study of 54 patients with ET, the use of clinical rating scales revealed on average a 1.32-fold side–side difference, and quantitative computerized tremor analysis revealed on average a 1.71-fold side–side difference in arm tremor severity . Unilateral arm tremor is less common, reportedly occurring in 2, 4.4 and 10% of ET cases, with values varying depending on the criteria used . One study evaluated unilateral arm tremor in 412 ET cases from 133 kindreds with presumed autosomal dominant ET . Inclusion criteria required unilateral kinetic or postural tremor for at least 5 years, without dystonic posturing or bradykinesia/rigidity . Only subjects with a first-degree relative with definite ET were included . Eighteen patients were identified as having isolated unilateral arm tremor without tremor affecting other body segments . Out of the 18 patients, 13 had a combination of postural and kinetic tremor and 5/18 had only unilateral postural tremor . Isolated unilateral postural tremor should raise the suspicion of PD, and the patient should be followed closely for the development of additional signs suggestive of PD.
Clinical pearl #3: Action tremor in ET is often but not necessarily bilateral. Small to moderate side–side differences are the rule rather than the exception.
Differences Between Essential Tremor And Parkinsons Disease
- Leo Nguyen
- March 20, 2019
There are an estimated 10 million people with essential tremor in the United States. Essential tremor is a neurological condition characterized by involuntary, rhythmic shaking or “tremors”. These tremors interfere with important tasks like drinking, eating, or writing legibly. Tremors are also present in those with Parkinson’s disease, a disease affecting the nervous system that is also symptomized by muscle inflexibility and slowed movement. Because tremors are a symptom of both Parkinson’s disease and essential tremor, it’s often hard for people to tell the difference between the two conditions. Though Parkinson’s disease and essential tremor have a common symptom, they are not equal.
For those with Parkinson’s disease, tremors typically occur during rest and are known as “resting tremors.” People with essential tremor mostly have tremors during times of activity. Because these tremors occur during activity or “action,” they are known as “action tremors.”
In addition to type, the tremors of Parkinson’s disease and essential tremor also differ in frequency and magnitude. Tremors related to Parkinson’s disease usually occur more frequently over time and are more forceful than those related to essential tremor. Individuals with essential tremor may see a fluctuation in the frequency of their tremors throughout the day, ranging from high to low.
Parkinsonian Tremor: The Most Common Form Of Resting Tremor
Some patients have a predominant postural tremor in addition to their rest tremor. This form is uncommon and has been considered to be a combination of an ET with PD although the relation between postural tremor that is phenomenologically similar to ET and PD has not been well defined. Further studies are needed to define the relation between ET and other tremors, including PD and other task specific tremors.
Box 3 Clinical Features Suggestive Of Psychogenic Tremor73
Tremor increases with attention, and lessens with distractibility
Responsive to placebo
Absence of other neurological signs
Spontaneous remissions or cures of symptoms
No evidence of disease by laboratory or radiological investigations
Employed in allied health professionals
Litigation or compensation pending
Presence of psychiatric disease
Reported functional disturbances in the past
Commonly, patients with psychogenic tremor often undergo a large number of diagnosis and therapeutic procedures before the final diagnosis is established. A review of medical history in these patients usually shows multiple functional somatic or psychosomatic illnesses. Once the diagnosis is made, most patients continue to have a fluctuating or constant course, followed by improving and progressive periods suggesting the prognosis is far from benign. The therapeutic success is also variable, but the treatment approach should include various combinations of psychotherapy as well as drugs, such as mild anxiolytics and antidepressants. While pharmacological treatment in organic tremor may reduce amplitude, but does not change the tremor frequency, the effect of treatment in psychogenic tremor usually varies from total suppression of tremor, especially when associated with the suggestion of a “cure” to no benefit.26 Interestingly, most of successfully treated patients were young.63
Clinical Impression 1: Proximal Vs Distal Postural Tremor
On arm extension, a higher proportion of ET than PD patients had isolated proximal tremor whereas a higher proportion of PD than ET patients had isolated distal tremor . There were similar differences when isolated proximal and distal tremors were defined liberally . Even when tremor was present in multiple joints, it was more prominent in the proximal joints in ET patients compared to PD patients . Furthermore, relative to PD, tremor in ET involved the wrist more than distal hand joints . When we excluded 28 PD patients who had taken carbidopa/levodopa within 4 h of the clinical examination, the results were similar. Even when we excluded 39 PD patients who had taken carbidopa/levodopa within 12 h of the examination, the results were similar . We did not perform similar analyses that excluded ET patients who had taken their medications on the day of testing, as there is less of a clear acute timed effect of these medications on motor state.
Table 3. ET vs. PD – Main measures with patients removed who took carbidopa/levodopa within 12 h of exam.
Misperception #4: Head Tremor Occurs In Et But Not In Pd
Head tremor is observed in patients with ET, with the reported prevalence being dependent on the ascertainment of the cases. One study noted head tremor in 12% of patients in the community, 37% in a tertiary referral center and 54% in a brain repository . Two studies evaluating factors associated with head tremor found that women with ET were four to six times more likely to have head tremor than men with ET . The head tremor of ET is typically a postural tremor that resolves at rest . Yet head tremor is not unique to ET. Head tremor has also been described in PD patients; one study reported head tremor in 17% of clinically diagnosed PD cases . Head tremor was described in detail in five clinically diagnosed PD cases . The head tremor was present at rest , had a frequency similar to the 4–6-Hz rest tremor of the limbs and responded to levodopa . None of the cases had voice tremor.
Clinical pearl #4: Head tremor often occurs in patients with ET but can on occasion also be seen in patients with PD. The head tremor of ET is typically one that resolves at rest , in contrast to what has been reported in PD.
What Are The Different Categories Or Types Of Tremor
Tremor is most commonly classified by its appearance and cause or origin. There are more than 20 types of tremor. Some of the most common forms of tremor include:
Essential tremor is one of the most common movement disorders. The exact cause of essential tremor is unknown. For some people this tremor is mild and remains stable for many years. The tremor usually appears on both sides of the body, but is often noticed more in the dominant hand because it is an action tremor.
The key feature of essential tremor is a tremor in both hands and arms, which is present during action and when standing still. Additional symptoms may include head tremor without abnormal posturing of the head and a shaking or quivering sound to the voice if the tremor affects the voice box. The action tremor in both hands in essential tremor can lead to problems with writing, drawing, drinking from a cup, or using tools or a computer.
Tremor frequency may decrease as the person ages, but the severity may increase, affecting the person’s ability to perform certain tasks or activities of daily living. Heightened emotion, stress, fever, physical exhaustion, or low blood sugar may trigger tremor and/or increase its severity. Though the tremor can start at any age, it most often appears for the first time during adolescence or in middle age . Small amounts of alcohol may help decrease essential tremor, but the mechanism behind this is unknown.
Ancillary Tests For Tremor Differential Diagnoses
The overlap among tremor disorders is wide and complex. ET patients may present postural tremor coexisting with resting tremor, while postural tremor may coexist with resting tremor in PD and tremor in dystonia is often mixed including a rest tremor component. For the most complicated tremor patients, Dopamine transporter imaging can provide objective evidence to demonstrate presynaptic nigrostriatal dopaminergic deficit in PD, whereas, it is normal in essential, dystonic and psychogenic tremor.
Table 2 Potential neurophysiological tests for tremor differential diagnosisFull size table
Bedside Examination: Distinguishing Et From Pd
Although the aforementioned diagnostic criteria attempt to clearly delineate ET from PD, it is not uncommon for patients with ET to exhibit ‘PD signs’ and, conversely, for patients with PD to exhibit ‘ET signs’. This overlapping of neurological signs is a source of diagnostic uncertainty. Clinicians should both be aware of this potential for overlap and look for the specific features that point to the correct diagnosis of ET or PD. Below, we address a number of common clinical misperceptions about these two diseases; these misperceptions fuel the diagnostic confusion. In doing so, we will review the neurological findings classically associated with PD and ET, as well as the subtle findings on examination that help to further distinguish the two disorders.
Tremors Not Associated With Parkinsons Disease
There are different types of tremors, of which not all are associated with Parkinson’s disease, and they vary slightly in terms of how, when and where they manifest in the body. They include essential tremor and dystonic tremor and may be associated with other conditions and genetic mutations, although a specific gene has not been identified.
A patient with a Parkinson’s tremor typically will find that their symptoms worsen and spread to other parts of the body over time. Generally, the tremor starts in one hand and can progress to the arm and foot on the same side of the body, and then eventually to the other side of the body. In severe cases, tremors also can affect the jaw or lips.
Misperception #2: Action Tremor = Et & Not Pd
Action tremor is the hallmark feature of ET and can be further subdivided into postural, kinetic and intention tremors. Yet just as rest tremor may occur in patients with ET, conversely, action tremor may be found in patients with PD. Indeed, it is not uncommon to encounter patients with PD who have various forms of action tremor. Below, we discuss postural, kinetic and intention tremors separately.
Clinical pearl #2: Although action tremor is the hallmark feature of ET, it is commonly found in patients with PD as well. When evaluating kinetic tremor in a particular patient, comparing it to other tremor types within that patient may help distinguish PD from ET. Thus, kinetic tremor is generally of greater amplitude than postural tremor in ET whereas the converse has been reported in PD. Intention tremor with limb dysmetria is more suggestive of ET than PD. Some of the clinical features of action tremor may similarly suggest one disorder or another. Thus, a postural tremor whose frequency is similar to the 4- to 6-Hz rest tremor of PD is suggestive of PD. A postural tremor with a significant latency is also more characteristic of PD.
Which Body Parts Do Parkinsons Tremors Affect
There are five main places you’ll have Parkinson’s tremors:
1. Hands. Parkinson’s disease tremors often start in the fingers or hands with what’s called a pill-rolling motion. Imagine holding a pill between your thumb and index finger and rolling it back and forth.
2. Foot. A Parkinson’s foot tremor is more likely to happen while you’re sitting or lying down with your feet at rest. If the tremor moves into your thigh muscles. It could look like your whole leg is shaking.
Foot tremors disappear when you stand or walk because those are active movements. A foot or leg tremor while you’re standing may be another condition.
3. Jaw. This is common in people with Parkinson’s. It may look like you’re shivering. It can become bothersome if the tremor makes your teeth chatter. If you wear dentures, it could make them shift or fall out.
Chewing eases the tremor, so gum might help.
4. Tongue. It’s rare, but a tongue tremor can cause your entire head to shake.
5. Internal. Some people with Parkinson’s say they can feel a shaking sensation in their chest or abdomen. But can’t be seen from the outside.
Box 1 Clinical Criteria For Essential Tremor2
Definite essential tremor
Postural tremor of moderate amplitude is present in at least one arm
Tremor of moderate amplitude is present in at least one arm during at least four tasks, such as pouring water, using a spoon to drink water drinking water, finger-to-nose manoeuvre, and drawing a spiral.
Tremor must interfere with at least one activity of daily living.
Medications, hypothyroidism, alcohol, and other neurological conditions are not the cause of tremor.
Probable essential tremor
Tremor of moderate amplitude is present in at least one arm during at least four tasks, or head tremor is present.
Medications, hyperthyroidism, alcohol, and other neurological conditions are not the cause of tremor.
Monoamine oxidase inhibitors
ET is believed to be of a central nervous system origin, but a reproducible neuropathology has not been described. A central aetiology was partly supported by the beneficial effect of thalamotomy, thalamic deep brain stimulation , and drugs that act centrally. Numerous experimental physiological and functional imaging studies have also implicated dysfunction in brain stem structures, including the inferior olive, locus coeruleus, red nucleus, thalamus, but cerebellum seems to be a prime candidate for the site of dysfunction in ET.23–25 It is probable that ET occur as a result of an abnormal oscillator of a CNS “pacemaker” in a currently unknown exact location that can be increased or suppressed by reflex pathways.
Clinical Impression 2: Postural Wrist Flexion
Ratings of wrist pronation-supination tremor were similar in ET and PD patients in the straight-arm extension position and the winged arm extension position . However, wrist flexion/extension tremor – wrist pronation/supination tremor was 0.73 ± 0.93 in ET patients and 0.07 ± 0.44 in PD patients . Even when we excluded 39 PD patients who had taken carbidopa/levodopa within 12 h of the examination, the results were similar .
Misperception #1: Rest Tremor = Pd & Not Et
Rest tremor is a cardinal feature of PD, and resolves upon initiation of movement. When it is accompanied by bradykinesia and rigidity, PD is high in the differential diagnosis. The proportion of PD patients with rest tremor has been reported to be 90% in clinical series and 76–100% in postmortem series . Patients with PD may also have tremor-predominant PD, in which rest tremor occurs in the relative absence of other signs of akinesia and rigidity.
Clinical pearl #1: While rest tremor may be seen in 20–30% of patients with ET, it tends to occur in patients with more severe disease and disease of longer duration. In addition, it may differ qualitatively from the type of rest tremor that occurs in patients with PD.
Essential Tremor Is Not Parkinsons Disease
Essential tremor and Parkinson’s disease are different conditions. Essential tremor is characterised by shaking when movement starts, which can continue or worsen during movement. The symptoms of Parkinson’s disease include:
- involuntary tremor when you are not moving
- muscle stiffness
- slowness of movement
Parkinson’s disease is caused by a lack of supply of the brain chemical dopamine, which is necessary for smooth and controlled muscular movement.
Consider Tremor Along With Other Symptoms
“Parkinson’s reputation is that it is a tremor disease, and that’s how you can identify it across a crowded room,” says Rebecca Gilbert, MD, PhD, chief scientific officer for the American Parkinson Disease Association in New York City.
Although tremors bring people to diagnosis in many cases, defining the condition as a tremor disease may have done patients a disservice over the years because there are more severe symptoms that people struggle with. Tremor is just the one that people can see, according to Dr. Gilbert.
“Many think if you don’t have a tremor everything is fine,” she says. “That isn’t true.”
Over time, other disease features, such as cognitive problems, psychosis, blood pressure irregularities, depression, and lack of desire to do things, can be more devastating.
James Beck, PhD, chief scientific officer with the Parkinson’s Foundation, also cautions that tremor may not be the first distinguishing feature.
“A person may notice a slowness of movement called bradykinesia,” he says. “Or someone may be walking down the street and one arm doesn’t swing. These symptoms may appear before tremor.”
While focusing only on tremor may not be advisable, understanding this abnormal movement and treatment options may help patients improve their quality of life.
Tremor Associated With Multiple Sclerosis
Multiple sclerosis is frequently associated with severe intention tremor, most likely because the demyelinating lesions of MS frequently affect the cerebellar outflow tracts. Thalamic DBS has proven to be partially effective, especially in young patients with little comorbidity . As discussed above for ET, the caudal zona incerta target appears to be beneficial for the treatment of tremor associated with MS .
A meta-analysis of 75 published cases of DBS in MS came to the conclusion that the majority of patients benefited from DBS, although complete cessation of tremor was rare . Coexisting ataxia may significantly limit the benefits of the procedure . Consequently, the long-term outlook for MS patient treated with DBS for tremor is relatively poor .
John Andrew, inContemporary Neurology, 1984
Demographic And Clinical Characteristics
Essential tremor and PD patients were similar in age, gender, education, handedness, caffeine intake, and use of medications with potential tremor-inducing properties . As expected, ET patients had longer tremor duration and were less likely to have undergone deep brain stimulation surgery than PD patients . ET patients also exhibited more severe tremor than PD patients in their Archimedes spiral drawings .
What Are The Causes Of Parkinsons Tremor
The exact cause of tremors in Parkinson’s isn’t fully understood. It may be tied to the degradation of cells that produce dopamine in the brain. And the causes may vary for different tremors.
Symptoms of Parkinson’s can also differ among people. About 75 percent of people with Parkinson’s disease report the presence of some kind of tremor, but not everyone who has the condition experiences tremors.
Rest tremors are frequently an early sign of the condition and are often used to make a Parkinson’s diagnosis. But studies have shown that several types of tremors can affect people with Parkinson’s.
For example, in a 2018 study involving nearly 400 people with Parkinson’s:
- 20 percent of the participants had no rest tremor at the start of the study
- almost 90 percent had some sort of tremor
- about 70 percent reported rest tremors
- 50 percent reported both postural and kinetic tremors
Many people have also reported changes in the type, severity, and location of tremors throughout the course of their experience with Parkinson’s disease.
Tremors in the hands are most common, but some people may also have Parkinson’s tremors in the:
In the early stages of the disease, tremors usually only appear on one side of the body, but tremors can spread to both sides of the body as the condition progresses.
Clinical Situation #1: Et+pd Or Just Pd
A 60-year-old man develops a mild, right-greater-than-left postural arm tremor and an even milder right arm kinetic tremor. The postural tremor involves a pronation-supination movement of the forearm and also involves the fingers. Five years later, the patient develops right-sided rest tremor, rigidity and bradykinesia.
This patient eventually meets the criteria for a clinical diagnosis of PD. The initial action tremor was postural greater than kinetic and involved pronation-supination at the wrist, which is more characteristic of the postural tremor in PD than ET. That tremor was likely an early manifestation of PD rather than ET. Hence, the diagnosis all along was likely to have been just PD.
Differentiation And Diagnosis Of Tremor
PAUL CRAWFORD, MD, and ETHAN E. ZIMMERMAN, MD, Nellis Family Medicine Residency, Nellis Air Force Base, Nevada
Am Fam Physician. 2011 Mar 15;83:697-702.
Patient information: See related handout on tremor, written by the authors of this article.
Tremor is an involuntary, rhythmic, oscillatory movement of a body part. It is the most common movement disorder encountered in clinical practice.1–3 There is no diagnostic standard to distinguish among common types of tremor, which can make the evaluation challenging. However, establishing the underlying cause is important because prognosis and specific treatment plans vary considerably. History and physical examination can provide a great deal of certainty in diagnosis. The most common tremor in patients presenting to primary care physicians is enhanced physiologic tremor, followed by essential tremor and parkinsonian tremor.1,3–6 All tremors are more common in older age.7
SORT: KEY RECOMMENDATIONS FOR PRACTICE
A comprehensive review of medications , with specific attention to medications started proximal to the onset of tremor, is important in patients with new-onset tremor.
A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.xml.
SORT: KEY RECOMMENDATIONS FOR PRACTICE
Parkinsons Tremors Vs Essential Tremors
Because they can be similar to Parkinson’s tremors, essential tremors are often confused as symptoms of the disease. Just as with Parkinson’s, essential tremor can cause uncontrollable rhythmic shaking in different parts of the body.
Up to 10 million people are affected by this common nervous system disorder. While genetics and environment likely play a role in essential tremor, the cause is unknown, according to the U.S. National Library of Medicine.
Essential tremors in the hands or arms can be distinct from Parkinson’s because they typically happen when the hands are in use.
“The essential tremor can get really bad when you’re using your limb — when drinking or eating soup, for example,” says Gilbert. “The Parkinson’s tremor is usually not as disabling whereas the essential tremor can be life-altering.”
The shaking from an essential tremor typically improves when using both hands to bring a cup to the mouth but the same action can amplify the tremor in Parkinson’s, according to Gilbert.
Dr. Beck points out that an essential tremor may be faster than a Parkinson’s tremor, which tends to be milder. A difference can often be seen in a person’s handwriting. Those with essential tremor tend to have more unsteady and wavy writing, whereas Parkinson’s patients are more apt to display micrographia, or abnormally small handwriting.
“They have low amplitude movement so their writing gets smaller and smaller to a point where it can be barely legible,” he says.
Pathophysiology Of Parkinsonian And Non
It is assumed that tremor networks within the brain are responsible for the different tremors. These circuits are not yet precisely known. Some nodes seem to play an important role. Ventral intermediate nucleus of the thalamus is the relay site in cerebellar outflow pathway where deep brain stimulation can improve almost all tremors indicating that cerebellum and its outflow pathway may involve in tremor genesis .
Emerging neuroimaging evidence showed that both the basal ganglia and the cerebellum are involved in Parkinsonian tremor . It was reported that PD with rest tremor had more grey matter volume decrease in the right quadrangular lobe and declive of the cerebellum and more iron accumulation in dentate nucleus, relative to those with akinetic-rigid type . Data from functional neuroimaging indicates that dopaminergic dysfunction in pallidum triggers the onset of tremor, whereas, the tremor amplitude is regulated within the cerebello-thalamo-cortical circuit .
What Treatments Are There For Tremors
Parkinson’s tremors cannot be cured. However, there are several options to manage them.
Many of the typical Parkinson’s drug treatments are associated with a reduction in tremors, including levodopa and dopamine agonists. A surgical procedure called deep brain stimulation also may be offered to control unmanageable tremors.
Physical therapy can help some patients control their tremors better, as can reducing the intake of substances such as caffeine, which can induce tremors. Many patients experience an increase in the severity of their tremors when they are stressed. Therefore, trying to reduce sources of anxiety and engaging in complementary therapies may help some patients.
Note: Parkinson’s News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
Types Of Tremor & Tremor Terminology
Before proceeding further, it is important to briefly delve into tremor nosology. There is a variety of tremor types that clinicians must consider when evaluating patients . Rest tremor occurs when voluntary muscle activity is absent. Action tremor can be subdivided into postural, kinetic and intention tremors. Postural tremor occurs when holding a body part motionless against gravity. Re-emergent tremor is a particular type of postural tremor; when the patient holds their arms extended, the tremor commences after a variable latency of one to several seconds. Kinetic tremor occurs with voluntary movement . Intention tremor occurs with goal-directed movement and worsens as the body part approaches the target. Familiarity with the terms defined above is necessary in order to understand the diagnostic criteria, which have been proposed for both ET and PD.
Misperception #6: Bradykinesia = Pd
Bradykinesia is a cardinal sign of PD. Although bradykinesia is not traditionally associated with ET, there have been several studies that report the contrary. One study quantified rapid alternating pronation-supination movements in 10 ET cases, 20 mild to moderate PD cases and 10 controls . Post hoc analysis demonstrated that rapid alternating movement cycle duration was statistically longer in ET cases compared with controls, and similar to PD cases . Another study, involving 61 ET cases and 122 controls, evaluated performance in four timed tests involving hand movements, as well as walking and visual reaction time . ET cases compared with controls had longer mean finger tapping times and mean visual reaction times . Another study reported reduced arm swing in 18/136 clinically diagnosed ET cases . While a small proportion of ET cases may exhibit slower movement times than controls, a reduction in amplitude and cessation of movement during rapid successive movements has not been demonstrated in ET.
Clinical pearl #6: Slower movement times may be observed in some patients with ET, yet other features of bradykinesia have not been demonstrated in ET.