Table 1.
Associated Disorders in Essential Tremor Patients
| Subtle Neurological Deficits |
| Bradykinesia (mild) |
| Cerebellar dysfunction |
| abnormal eyeblink reflex conditioning |
| deficits in paced finger typing |
| dysfunction in hand–eye coordination and ocular movements |
| mirror movements |
| mild dysarthria |
| tandem gait ataxia |
| Olfactory and hearing deficits |
| Non-motor deficits |
| Mild cognitive deficits (Table 4) |
| Neuropsychiatric symptoms |
| anxiety |
| depression |
| specific personality traits |
| Sleep disorders |
| Decreased body mass index |
| Nervous system pathology |
| Pathology of the cerebellum and its brainstem connections |
| Association with neurological or neurodegenerative disorders |
| Parkinson's disease |
| Dystonia |
| Myoclonus |
| Possibly associated with migraine, restless legs syndrome, Lewy body dementia and Alzheimer's disease |
Table 2.
ET Patient Series with Cognitive Evaluation (selection)1
| n Cases | n Cases | ||
| Gasparini et al.16 | 27 | Yes, 15 | Thalamic DBS |
| Lombardi et al.17 | 18 | No2 and 18 PD | Thalamic DBS |
| Duane & Vermilion19 | 55 | No2,3 | Thalamic DBS |
| Lacritz et al.20 | 13 | No2 and 13 PD | Thalamic DBS |
| Tröster et al.21 | 101 | No2 | Thalamic DBS |
| Benito-León et al.25 | 232 | Yes, 696 | Population based |
| Sahin et al.23 | 16 | Yes, 16 | Specialized clinic |
| Higginson et al.22 | 24 | Yes, 21 and 24 PD | Thalamic DBS |
| Kim et al.24 | 34 | Yes, 33 | Specialized clinic |
1 Passamonti et al. series61 not included (see text)
Table 3.
Main Cognitive Deficits in ET patients1
| Lombardi17 | Gasparini16 | Duane19 | Lacritz20 | Troster21 | Sahin23 | Higginson22 | Kim24 | Benito-León25 | |
| Psychological functions | |||||||||
| Global cognitive function | = | ND | ND | ND | ND | ND | ND | ++ | ++ |
| Attention–concentration | ++ | ++ | = | ND | ND | = | ++ | ++ | ++ |
| Working memory | ++ | ++ | ND | ++ | ++ | = | ++ | ++ | ND |
| Motor performance | ND | ND | ND | ND | ++ | ND | ND | ND | ND |
| Spatial fluency | ND | ND | ND | ++ | ND | ND | ND | ND | ND |
| Concept formation | ++ | ++ | + | ++ | = | ++ | ND | ND | ND |
| Reasoning | = | ND | ND | ND | ND | ND | + | ND | ND |
| Memory | |||||||||
| Verbal memory | ++ | ND | + | = | ++ | + | ND | –/++2 | ND |
| Logical memory | ND | ND | ND | ND | = | ND | ++ | ND | ND |
| Visual memory | ND | ND | + | + | ND | = | ++/ = 2 | = | ND |
| Verbal fluency | ++ | ++ | ++ | + | ++ | ++ | + | ++ | ++/–2 |
| Naming | + | ND | ND | = | ++ | = | ++ | ++ | + |
| Visuoperception | = | ND | ND | ND | ++/ = 2 | ++ | ND | ND | + |
| Visuoconstruction | = | = | = | = | ND | = | ++ | ND | ND |
| Mood (depression) | + | ND | + | + | ND | ND | ++ | ND | ++3 |
3 See Lois et al.42
Reviewer's test selection and test gradation: = , similar or superior to controls or standard measures; +, mild alteration (statistically significant); ++, clear alteration (p<0.01); ND, not done
Attention–concentration: Digit forward Span (WAIS); TMT; Picture Completion (WAIS); Brief test of attention; Symbol digit and others
Table 4.
Essential Tremor and Cognitive Deficits (population-based series)1
| 2322 | 6963 | ||
| Global cognitive function | |||
| MMSE-37 (range 0–37) | 27.0 (6.7) | 28.9 (5.9) | 0.001 |
| Attention/frontal executive function | |||
| Trail Making Test A (errors) | 8.7 (11.0) | 3.8 (7.6) | 0.001 |
| Trail Making Test A (time to complete) | |||
| >5 minutes | 91 (39.2%) | 148 (21.3%) | 0.001 |
| 0 or <5 minutes | 141 (60.8%) | 548 (78.7%) | |
| Verbal fluency | |||
| Verbal fluency (fruits) | 8.9 (3.9) | 10.0 (3.5) | 0.001 |
| Memory | |||
| Naming test (score 0–6) | 5.4 (1.5) | 5.7 (6) | 0.019 |
| Immediate free recall (score 0–6) | 3.9 (1.6) | 4.2 (1.4) | 0.012 |
| Delayed free recall (score 0–6) | 3.5 (1.9) | 3.9 (1.8) | 0.009 |
| Immediate logical memory (score 0–6) | 3.9 (1.7) | 4.3 (1.6) | 0.003 |
| Delayed logical memory (score 0–6) | 3.1 (2.2) | 3.6 (2.1) | 0.008 |
| (B) Cognitive functions; no statistically significant difference | |||
| Verbal fluency | |||
| (animals) | 12.6 (5.0) | 12.9 (4.7) | 0.42 |
| Premorbid intelligence | |||
| Word accentuation test (score 0–30) | 10.2 (10.3) | 11.4 (10.3) | 0.10 |
1 Modified from Benito-León et al.25
Table 5.
Cognitive Deficits in ET: Summary
| General conclusion |
| Cognitive deficits are mild (subclinical) and multiple. |
| Consistent deficits |
| (A) Attention–concentration and working memory |
| Digit Span, forward and backwards (WAIS) |
| Trail Making Test Part A, Symbol Search |
| Selective auditory attention (Brief Test of Attention) |
| Visual reaction time |
| Working memory |
| (Visual Span, WMS; Letter–Number Sequencing, WAIS; Stroop test) |
| (B) Executive functions |
| Set-shifting (Wisconsin Card Sorting Test, Stroop test, Trail Making Test Part B) |
| Verbal fluency (Letter-Cued Word Fluency; animals and others) |
| FAB battery |
| Other tests (Ruff Figural Fluency test; Matrix Reasoning –WAIS) |
| (C) Explicit verbal memory (immediate or short-term and delayed) |
| Short-term verbal memory (CVLT and other tests) |
| Delayed verbal memory (CVLT and other tests) |
| Wechsler Memory Scale (WMS-R), logical memory not clearly affected |
| Visual memory (ROF test) without alterations |
| (D) Language |
| Verbal fluency (letter-cued word fluency, listing fruit or animals during 1 minute) |
| Vocabulary (Benton Naming test) |
| Possible deficits |
| Mental processing speed (several tests) |
| Visuospatial functions (facial recognition) |
| General cognitive capacity (elderly ET) |
| No deficit (or very dubious) |
| Reasoning, abstract thinking, calculation |
| Not evaluated |
| Implicit memory (exception: eyeblink conditioning) |