Evidence-based guideline update: treatment of essential tremor: report of the Quality Standards subcommittee of the American Academy of Neurology.

BACKGROUND: This evidence-based guideline is an update of the 2005 American Academy of Neurology practice parameter on the treatment of essential tremor (ET). METHODS: A literature review using MEDLINE, EMBASE, Science Citation Index, and CINAHL was performed to identify clinical trials in patients with ET published between 2004 and April 2010. RESULTS AND RECOMMENDATIONS: Conclusions and recommendations for the use of propranolol, primidone (Level A, established as effective); alprazolam, atenolol, gabapentin (monotherapy), sotalol, topiramate (Level B, probably effective); nadolol, nimodipine, clonazepam, botulinum toxin A, deep brain stimulation, thalamotomy (Level C, possibly effective); and gamma knife thalamotomy (Level U, insufficient evidence) are unchanged from the previous guideline. Changes to conclusions and recommendations from the previous guideline include the following: 1) levetiracetam and 3,4-diaminopyridine probably do not reduce limb tremor in ET and should not be considered (Level B); 2) flunarizine possibly has no effect in treating limb tremor in ET and may not be considered (Level C); and 3) there is insufficient evidence to support or refute the use of pregabalin, zonisamide, or clozapine as treatment for ET (Level U).

Gait and dementia: moving beyond the notion of gait apraxia.

Highest level gait disorders are produced by pathology in one or more structures in the cortical-basal ganglia-thalamocortical loop, which plays an important role in producing movements and postural synergies that meet personal desires and environmental constraints. Virtually all patients with dementia have pathology in one or more components of this loop, so highest level gait disorders are common in patients with dementia. The terminology surrounding these gait disorders is unnecessarily complex and too heavily influenced by the controversial concept of gait apraxia. Straightforward descriptive diagnostic criteria are needed. To this end, four core clinical features of highest level gait disorders are proposed: 1) inappropriate (counterproductive) or bizarre limb movement, postural synergies, and interaction with the environment, 2) qualitatively variable performance, influenced greatly by the environment and emotion, 3) hesitation and freezing, and 4) absent or inappropriate (counterproductive) rescue reactions. These core features follow logically from the physiology of the cortical-basal ganglia-thalamocortical loop and should be regarded as signs of pathology in this loop. A clinical rating scale based on these features should be developed to facilitate clinical diagnosis and clinicopathological correlation, while avoiding the ambiguities and controversies of gait apraxia.

Pentagon copying is more impaired in dementia with Lewy bodies than in Alzheimer's disease.

OBJECTIVES: In many cases the clinical differentiation of patients with dementia with Lewy bodies (DLB) from those with Alzheimer's disease (AD) has been difficult. Because many neuropsychological studies have reported greater visuospatial/constructional impairment in DLB than in AD, it was determined whether accuracy in copying the interlocking pentagons item on the mini mental state examination (MMSE) may be helpful in distinguishing patients with DLB from those with AD relatively early in the course of the dementia. METHODS: All cases of neuropathologically proved DLB and AD in the Center for Alzheimer Disease and Related Disorders brain bank were retrospectively reviewed, and the first available MMSE for each was retrieved. Only patients with MMSE scores > or = 13 were included, indicating mild to moderate dementia. The patients' copies of the interlocking pentagons were analyzed and graded as acceptable or unacceptable according to the original instructions for grading the MMSE. RESULTS: Seventeen patients with DLB and 27 patients with AD were identified for whom MMSE with copies of the interlocking pentagons were available. Two patients with DLB (MMSEs 22 and 27) drew the pentagons acceptably, by contrast with 16 of the patients with AD (MMSEs 13-28). An unacceptable copy was associated with DLB with a sensitivity of 88% and a specificity of 59% (p = 0.002). CONCLUSIONS: For patients with MMSE scores > or = 13, an inability to accurately copy the pentagons suggests that the diagnosis is more likely DLB than AD. The results confirm the work of others on visuospatial/constructional impairment in DLB and indicate that this feature may be helpful in its diagnosis.

Essential tremor frequency decreases with time.

OBJECTIVE: To quantify the extent to which tremor frequency changes with time in patients with essential tremor. BACKGROUND: Tremor frequency tends to be lower in older patients. The author's previous study of 18 patients with essential tremor produced evidence that tremor frequency decreases slowly over a period of 4 to 8 years. A decrement in frequency will increase tremor amplitude because there is less attenuation of lower-frequency tremor by the low-pass filtering properties of muscle and limb mechanics. METHODS: Nineteen women and 25 men with essential tremor and no other neurologic conditions were followed for 4 years. Accelerometry and surface electromyography (EMG) were used to measure hand tremor and motor unit entrainment in the extensor carpi radialis brevis every 2 years. Tremor frequency was computed from the spectral peak in the rectified filtered EMG spectrum under the condition of 300-gram loading. RESULTS: The patients' mean +/- SD age was 68.0+/-9.95 years. The mean tremor frequency at baseline was 5.79+/-1.32 Hz. The mean decrement in tremor frequency over 4 years was 0.332 Hz (95% CI = 0.141 to 0.523) and was 0.270 Hz (95% CI = 0.122 to 0.418) when a 61-year-old outlier patient was excluded. Tremor frequency and patient age were linearly related: frequency = -0.061(age) + 9. 94 (r = 0.459; p<0.002). CONCLUSIONS: The frequency of essential tremor decreases by approximately 0.06 to 0.08 Hz/year. This decrement in frequency is consistent with the linear relationship between age and tremor frequency.

Diagnostic criteria for essential tremor and differential diagnosis.

Classic essential tremor (ET) is a condition in which the upper limbs (approximately 95% of patients) and, less commonly, the head (approximately 34%), face (approximately 5%), voice (approximately 12%), trunk (approximately 5%), and lower limbs (approximately 20%) exhibit a mixed postural and kinetic tremor without other neurologic abnormalities. Most patients with ET probably inherit the disease through an autosomal dominant gene, but the true ratio of hereditary versus sporadic ET is unknown. Isolated focal, position-specific, and task-specific tremors are probably not ET in most patients and are often due to subtle dystonia. Unilateral tremor, gait disturbance, rigidity, bradykinesia, rest tremor, and rapid onset of symptoms are indications of other tremorogenic disorders.

The pathophysiology of essential tremor.

The pathophysiologic abnormalities that underlie essential tremor (ET) are difficult to decipher because autopsy studies reveal no gross or microscopic abnormalities. Electrophysiologic studies are consistent with a central source of tremorogenic oscillation. The inferior olive and cerebellum are implicated by PET studies. Harmaline tremor in animals shares many features with ET, and the inferior olive has been identified as the source of oscillation in this animal model. Therefore, a disturbance of olivocerebellar rhythmicity is at present the most popular hypothesis for the etiology of ET. Although electrophysiologic tests are available that are helpful in the diagnosis of ET, a gold-standard test or biologic marker for ET is still lacking.

Pushing and pulling with the upper extremities while standing: the effects of mild Alzheimer dementia and Parkinson's disease.

Eleven patients with mild dementia of Alzheimer type, 12 patients with mild to moderate Parkinson disease, and 27 control subjects of comparable age, education, and gender pushed or pulled on a rigid horizontal bar while maintaining stable erect stance. A target window (target force +/-10% maximum force) and a bar force cursor were displayed on a video screen, and subjects were asked to place the bar force cursor within the target window as quickly and as accurately as possible holding the target window for at least 1 sec. The target forces were 50% and 75% maximum force for each person, and three 4.0-sec push trials and three 4.0-sec pull trials were performed for each target force. Moments of force (torque), body motion, and extremity electromyography were measured with a computerized motion analysis system. The patients with Alzheimer's disease had only slightly lower Mini Mental State Examination (MMSE) scores (mean +/- standard deviation [SD] = 25.0 +/- 2.3) than the patients with Parkinson's disease (28.8 +/- 1.5) and control subjects (28.7 +/- 1.3). The patients with Alzheimer's disease had upper limb reaction times (0.827 +/- 0.399 sec) that were greater than those of the patients with Parkinson's disease (0.672 +/- 0.315 sec) and control subjects (0.606 +/- 0.263 sec). Furthermore, the patients with Alzheimer's disease achieved the designated target in only 46.2% of trials, which was comparable to the performance of the patients with Parkinson's disease (55.6%) but inferior to the control subjects (80.6%). Movement times did not differ significantly. The patients and control subjects initiated movement with comparable anticipatory postural activity in the lower limbs. The poor success rates of the patients with Alzheimer's disease and the patients with Parkinson's disease were attributable to inadequate visually guided adjustments in force after the initial movement began. This difficulty in making quick motor adjustments may be relevant to the tendency of patients with Alzheimer's disease to fall.

Estrogen for Alzheimer's disease in women: randomized, double-blind, placebo-controlled trial.

BACKGROUND: AD, the most prevalent cause of dementia, affects twice as many women as men. Therapeutic options are limited, but results of prior studies support the hypothesis that estrogen treatment may improve symptoms of women with this disorder. METHODS: Forty-two women with mild-to-moderate dementia due to AD were enrolled into a randomized, double-blind, placebo-controlled, parallel-group trial of unopposed conjugated equine estrogens (1.25 mg/day) for 16 weeks. RESULTS: Outcome data were available for 40 women at 4 weeks and 36 women at 16 weeks. At both 4 and 16 weeks, there were no significant differences or statistical trends between treatment groups on the primary outcome measure (the cognitive subscale of the Alzheimer's Disease Assessment Scale), clinician-rated global impression of change, or caregiver-rated functional status. Exploratory analyses of mood and specific aspects of cognitive performance also failed to demonstrate substantial group differences. CONCLUSION: Although conclusions are limited by small sample size and the possibility of a type II error, results suggest that short-term estrogen therapy does not improve symptoms of most women with AD. These findings do not address possible long-term effects of estrogen in AD, possible interactions between estrogen and other treatment modalities, or putative effects of estrogen in preventing or delaying onset of this disorder.

Animal models of action tremor.

This article is devoted to animal models of tremors that emerge from lesions in the Guillain-Mollaret triangle. Cerebellar intention tremor is caused by lesions in the brachium conjunctivum or in the interpositus nucleus, possibly in combination with damage to the dentate nucleus. Impaired feed-forward motor control delays the braking of rapid movements, resulting in target overshoot and subsequent oscillation. Transcortical and transcerebellar sensorimotor loops undergo oscillation at a frequency that depends on the mechanical properties of the limb and the length of the sensorimotor loop (mechanical reflex oscillation). The crescendo quality of intention tremor may be a result of amplification of tremor in reverberating brain stem-cerebellar or thalamocortical loops. So-called rubral or midbrain tremor is caused by a combination of damage to the brachium conjunctivum and nigrostriatal pathways in the vicinity of the red nucleus. Secondary compensatory changes in the motor system are probably involved because midbrain tremor in people usually begins weeks or months after a midbrain stroke or trauma. Harmaline causes enhanced neuronal synchrony and rhythmicity in the inferior olive; this animal model, although as yet unproven, is the most popular one for essential tremor (ET). Additional studies in laboratory animals are needed to define the seemingly universal involvement of the cerebellum and ventrolateral thalamus (ventralis intermedius [Vim]) in virtually all human tremor disorders.

Hemianopsia in dementia with Lewy bodies.

OBJECTIVE: To describe the pathologic changes that caused a left homonymous hemianopsia in a patient with dementia with Lewy bodies. DESIGN: Report of a case and postmortem studies. MAIN OUTCOME AND RESULTS: A 66-year-old woman experienced parkinsonism and left homonymous hemianopsia early in the course of a rapidly progressive dementia that culminated in death only 21 months after the onset of her symptoms. Postmortem examination revealed pathologic features consistent with the diagnosis of dementia with Lewy bodies. The only apparent explanation for her visual field deficit was a disproportionately large number of neurofibrillary tangles in the right striate, peristriate, and inferotemporal cortices. CONCLUSION: A clinically obvious homonymous hemianopsia can result from the occipital and inferotemporal cortical degeneration in dementia with Lewy bodies.

Tremor in ostensibly normal elderly people.

Tremor in ostensibly normal people, aged 70-91, was assessed clinically and electrophysiologically with the goal of estimating the prevalence of abnormal tremor. Fifty men and 50 women, mean age 76.0 +/- 4.7 yrs, were recruited through advertisements for healthy volunteers (n = 50 "biased" control subjects) and from the spouses of patients referred to us for dementia or Parkinson's disease (n = 50 "unbiased" control subjects). All participants were interviewed and examined by the author. Tremor was assessed quantitatively with rating scales, triaxial accelerometry, electromyography, a digitizing tablet, and spectral analysis. Twenty-three people (23%) were judged clinically to have mildly abnormal tremor resembling mild essential tremor. Twelve people with abnormal tremor belonged to the biased group and 11 were in the unbiased group. The clinical diagnosis of abnormal hand tremor correlated well with the presence of motor unit entrainment in the forearm EMG and with writing or drawing tremor that was measurable with a digitizing tablet. Only 10 of 23 people with abnormal tremor were aware of their tremor, and none had been diagnosed previously by a physician. Nine of 77 people (11.7%) with normal tremor had a parent or sibling with possible essential tremor, and five of the 23 people (21.7%) with abnormal tremor had this family history. Mild undiagnosed tremor, resembling essential tremor, is common in this age group.

The distribution of amyloid beta protein deposition in the corpus striatum of patients with Alzheimer's disease.

The distribution of amyloid beta peptide (A beta) was quantified in the corpus striatum and pallidum of 10 patients with Alzheimer's disease (AD) and three patients with both Alzheimer's disease and Parkinson's disease (AD-PD). A beta occurred almost exclusively in plaques that did not have neurites or amyloid cores. Caudate, accumbens nuclei and rostral putamen contained more of the diffuse plaques than did caudal putamen. No diffuse plaques were found in the neighbouring globus pallidus. This distribution of A beta deposition may reflect the distribution of diseased synaptic cortical afferents rather than a putative vascular source of A beta.

Gait initiation by patients with lower-half parkinsonism.

Patients with multiple deep cerebral infarcts and white matter degeneration commonly exhibit a hesitant, shuffling gait, with preserved arm swing. This pattern of walking is called lower-half or lower-body parkinsonism. Gait initiation and turning consist of one or more short, hesitant steps in which the feet shuffle across the floor. This abnormality of gait initiation was studied with quantitative motion analysis in five patients, ages 74-87 years. Five men and five women with normal mobility and comparable ages exhibited three key events of gait initiation: (i) activation of tibialis anterior and inactivation of triceps surae produced bilateral ankle dorsiflexion and a sagittal moment of force that propelled the body anteriorly; (ii) abduction of the swing hip occurred simultaneously with event (i); and (iii) abrupt 3-10 degrees flexion of the support hip and knee occurred nearly simultaneously with events (i) and (ii) and produced a transient reduction in vertical force beneath the support foot. Events (ii) and (iii) produced a coronal moment of force about the ankles that propelled the body toward the support foot. Thus, in normal gait initiation, a smooth sequence of postural shifts propels the body anterolaterally toward the support limb, culminating in a forward step. The patients, by comparison, exhibited errant deviations in their postural shifts of gait initiation, and one or more aborted steps frequently preceded the first complete step. Nevertheless, all patients employed the usual three key events in their initial attempt at stepping, consistent with a normal motor strategy of gait initiation. These results and previous clinical observations suggest that the principal locomotor deficit is an impaired generation of postural shifts that mediate changes from one steady-state posture or movement to another.

Central mechanisms of tremor.

Physiologic and pathologic tremors are mechanistically classified into two broad groups: (1) those produced by oscillation in sensorimotor loops, so-called mechanical-reflex tremors, and (2) those produced by the oscillatory properties of central neuronal networks. This review provides a contemporary perspective of tremor pathophysiology while acknowledging that no form of tremor is understood completely. Indeed, the origin of oscillation in most forms of tremor is undefined, and in many instances the underlying pathology is unknown.

Quantification of essential tremor in writing and drawing.

Eighty-seven patients, aged 15-84 years (mean, 61.8 +/- 16.2 SD), with essential tremor wrote two series of cursive e's and cursive l's on a standard sheet of ruled paper that was mounted on a commercially available digitizing tablet. Forty patients also drew an Archimedes spiral. Postural wrist tremor was measured with a triaxial accelerometer on the dorsum of the horizontally extended hand. The digitizing tablet was sufficiently sensitive to measure sustained visible tremor. Very severe tremor could not be recorded when it prevented a patient from keeping the ballpoint pen on the tablet. The intertrial variability of the handwriting data was such that a 36.0% change in mean acceleration amplitude (cm/s2) and an 8.3% change in mean tremor frequency (Hz) could be detected in the hypothetical population of 30 patients (paired-sample t test, p = 0.01, power = 90%). The intertrial changes detectable with accelerometry were 35.9% (amplitude) and 7.8% (frequency). The correlations between wrist tremor and writing tremor were < 0.60 for amplitude and < 0.25 for frequency. Significant correlations between patient age and tremor frequency and between tremor amplitude and frequency existed for postural tremor but not for writing or drawing tremor. Standard digitizing tablets for personal computers are useful in the quantitative assessment of writing tremor. The amplitude and frequency characteristics of tremor in posture, writing, and drawing may differ significantly.

The role of aging in the clinical expression of essential tremor.

Essential tremor is the most common form of abnormal tremor. It is a monosymptomatic disorder characterized by action tremor but no other sign of motor dysfunction. More than half of all cases are inherited through a Mendelian dominant gene. Mild essential tremor is probably the cause of tremulousness that is frequently attributed to aging. The prevalence of essential tremor increases with age, and aging appears to have an independent effect on the clinical characteristics of essential tremor. Autopsies have revealed no discernible pathology. Essential tremor probably emerges from subtle pathologic transformation of a physiologic neuronal oscillator, possibly the inferior olive. A more complete characterization of the effects of aging on motor pathways may be necessary to fully understand the natural history and pathogenesis of this disorder.