Figure 1
Polymyographic (PMG) recordings. A: Installation of the patient for PMG recordings. Recording was performed in the following muscles; flexor and extensor of the carpus, biceps, and first interosseous muscle of the hand. Black lines show the active electrode, red lines the reference electrode associated to the same muscle. Accelerometer and ground electrode (common for all pairs of electrodes) are pointed with a yellow line. B, C: PMG recordings of tremor. Trace 1: biceps; Trace 2: extensor carpi radialis (ECR); Trace 3: flexor carpi radialis (FCR); Trace 4: first dorsal interosseous (FDI); Trace 5: accelerometer. B: 6.2 Hz regular tremor in a 13 years-old male patient visible on the accelerometer and on the FCR and ECR; arms in the mirror position. C: 6.8 Hz tremor in a 16 years-old female patient visible on the accelerometer and on the FCR ; carpus extended. D-G: PMG recordings of myoclonus (we selected samples of myoclonus in patients exhibiting tremor (not shown)). D, E: myoclonus recordings in a 17 years-old male patient visible at rest (D) and while maintaining the mirror position (E). F, G: myoclonus recordings in a 13 years-old male patient (same patient as B tremor recording), at rest (F) and while extending the carpus (G) (note the 7.5 Hz tremor visible on the accelerometer).
Black arrows indicate myoclonus on the PMG; #: myoclonus visible on the accelerometer; *: synchronous myoclonus on all muscle tested; $: tremor burst on the PMG correlates with the accelerometer.
Table 1
Main characteristics of the patients, according to sex.
| MALE | FEMALE | TOTAL | |
|---|---|---|---|
| NUMBER OF PATIENTS | 9 | 9 | 18 |
| Age at inclusion1 (years) | 14.6 ± 5 [8–24] | 3.2 ± 4.1 [8–20] | 13.9 ± 4.7 [8–24] |
| Age at onset2 (years) | 7.1 ± 4.43 [2–13] | 5.9 ± 2.30 [2–10] | 6.5 ± 3.5 [2–13] |
| Age at diagnosis (years) | 11.5 ± 4.3 [3.8–15.4] | 9.2 ± 3.5 [3.6–14.7] | 10.3 ± 4 [3.56–15.4] |
| Disease duration at inclusion (years) | 7.6 ± 6.3 [2.84–19.6] | 7.2 ± 3.8 [2.3–14.6] | 7.4 ± 5.1 [2.3–19.6] |
| Hand lateralization3: right | 88% (7) | 100% (8) | 94% (15) |
| Normal perinatal history | 100% (9) | 100% (9)4 | 100% (18) |
| Sleep disturbances | 22% (2) | 14% (1) | 23% (3) |
| Attention difficulties according to the family | 22% (2) | 0% (0) | 13% (2) |
| Other problem5 | 11% (1) | 0% (0) | 6% (1) |
| Family history of ET5 | 56% (5) | 67 (6) | 61% (11) |
| Parent affected: mother | (1) | (2) | (3) |
| father | (3) | (1) | (4) |
| sibling | (0) | (1) | (1) |
| second degree relative6 | (2) | (2) | (4) |
| Personal assistance: | 86% (6) | 33% (3) | 56% (9) |
| Psychomotor therapist | (2) | (1) | (3) |
| Computer alone | (1) | (2) | (3) |
| Occupational therapist + computer | (2) | (0) | (2) |
| Extra time for tasks | (1) | (0) | (1) |
| Psychological distress | 71% (5) | 44% (4) | 56% (9) |
| Psychological follow-up | 37% (3) | 25% (2) | 31% (5) |
| Personal assistance and/or psychological follow-up | 78% (7) | 50% (4) | 65% (11) |
| Course of the disease from beginning according to the patient and parents: | |||
| worsened | 63% (5) | 50% (4) | 56% (9) |
| stable | 25% (2) | 38% (3) | 31% (5) |
| improved | 13% (1)7 | 13% (1) | 13% (2) |
| PedsQL global score (patient) | 86.3 ± 6 [77.2–91.3] | 73.8 ± 13.1 [52.1– 88] | 79 ± 12.2 [52.2–91.3] |
| PedsQL global score (parent) | 79.8 ± 12.6 [54.3–91.3] | 75.6 ± 21.3 [33.7–91.3] | 77.7 ± 17 [33.7–91.3] |
[i] Qualitative data are presented as percentage (number of patients); quantitative data are presented as mean ± standard deviation [range].
1: For prospective inclusions, age at inclusion ranged from 8 to 17; 2: unknown for one girl; 3: one boy was left handed, no patient was ambidextrous 4: one twin pregnancy with delivery at 37 weeks; 5: dysorthographia; 6: one patient had a father and a grandfather, one had a grandfather and an uncle, the other two had an uncle affected; 7: this patient was treated by propranolol; PedsQL: Pediatric Quality of Life inventory.
Figure 2
Flow chart.
n = number of patients.
Table 2
Main characteristics of tremor and its course: clinical and electrophysiological evaluation.
| CLINICAL ASSESSMENT: | |
|---|---|
| Upper limb | 100% (18) |
| Lower limb | 22% (4) |
| Voice | 6% (1) |
| Neck | 0% (0) |
| Head | 0% (0) |
| More than one localization | 28% (5) |
| Bilateral Asymmetry | 94%1 (17) (9) |
| Postural or action | 100% (18) |
| Postural | 94% (17) |
| Postural alone | 0% (0) |
| Postural + action | 7% (1) |
| Action | 94% (17) |
| Action alone | (1) |
| Only during a specific task2 | (1) |
| Rest tremor | 17% (3) |
| Isolated (number of patients) | (0) |
| Rest tremor + action tremor | (0) |
| Rest tremor + action tremor + postural tremor | (3) |
| Associated with myoclonus | 25% (4) |
| Electrophysiological assessment: | |
| Postural or action tremor | 88%3 (15) |
| Rest tremor | 6% (1) |
| Associated with myoclonus | 41% (7) |
| Mean frequency of tremor (Hz) | 7.6 ± 1.4 [5–10] |
| Mean duration of bursts (ms) | 82.7 ± 16.0 [65–130] |
| Weight (500g) persistence3 | 93% (13) |
| Mean frequency for tremor persisting with 500 g weight (Hz) | 8.18 ± 1.47 [4–10] |
[i] Qualitative data are presented as percentage (number of patients); quantitative data are presented as mean ±standard deviation [range].
1: for one boy, only left upper limb (UL) tremor was observed during the evaluation, although he reported having intermittent tremor of the right UL; 2 : while pouring water; 3: tremor was very subtle during EMG assessment in 2 patients and could not be recorded.
Table 3
Main characteristics of tremor and its course: course of disease according to patients and/or parents/caregivers.
| AT ONSET | AT INCLUSION | |
|---|---|---|
| Topography (body distribution) | ||
| Upper limb | 100% (18) | 100% (17) |
| Lower limb | 0% (0) | 35% (6) |
| Voice | 6% (1) | 23% (4) |
| Neck | 0% (0) | 6% (1) |
| Head | 0% (0) | 23% (4) |
| More than one localization | 6% (1) | 47% (8) |
| Bilateral | 100% (18) | 100% (17) |
[i] Qualitative data are presented as percentage (number of patients).
Table 4
Results of the studies of childhood-onset essential tremor.
| PRESENT STUDY | GHOSH ET AL. (13) | FUSCO ET AL. (14) | LOUIS ET AL. (12) | TAN ET AL. (7) | JANKOVIC ET AL. (8) | LOUIS ET AL. (16) | |
|---|---|---|---|---|---|---|---|
| STUDY TYPE (YEARS OF STUDY) | CROSS-SECTIONAL (2018–2021) | RETROSPECTIVE (2004–2011, PUBLISHED IN 2016) | CROSS-SECTIONAL (PUBLISHED IN 2003) | RETROSPECTIVE (PUBLISHED IN 2001) | PROSPECTIVE, CROSS-SECTIONAL (PUBLISHED IN 2006) | RETROSPECTIVE (PUBLISHED IN 2004) | RETROSPECTIVE (PUBLISHED IN 2005) |
| Number of patients | 19 | 211 | 9 | 19 | 19 | 39 | 95 |
| Age at onset1 | 7.1 [2–13] | 9.71 ± 5.622 | [2–5] | 6.8 [1–14] | 10.8 ± 4.1 [6–16] | 8.8 ± 5.0 [1–16] | 5.9 ± 4.7 [1–16] |
| Age at assessment1 | 13.9 | 14.09 ± 5.003 | [7.5–16.8] | 11.3 | 25.7 ± 15.0 [16–73] | 20.3 ± 14.4 [3.3– 64.4] | 11.7 ± 4.6 [2–18] |
| Mean age at diagnosis1 | 10.3 (±4) | NK | NK | NK | NK | NK | NK |
| Sex distribution (% of males) | 50 | 61 | 66 | 68 | 73.5 | 74 | 74 |
| Presence of a family history of tremor (%) | 61 | 35 | 44 | NK | 56.2 | 79.5 | 624 |
| Course5: | |||||||
| Progressive | 56 (9) | 40 (88) | NK | NK | NK | NK | NK |
| static | 31 (5) | 45 (95) | |||||
| improvement | 12 (2) | 1 (4) | |||||
| NK | 1 (3) | 11 (25) | |||||
| Distribution at onset: bilateral upper limb (%) | 100 | 94 | NK | NK | NK | NK | NK |
| Distribution at last assessment: bilateral (%) | 100 | 100 | NK | 100 | 100 | NK | NK |
| Other regions involved5 | (5) | Yes6 | 11 (1) | 5 (1) | 10.5 (2) | Yes6 | NK |
| Head tremor5 | 0 | 12 | 0 | 11 (1) | 10.5 | 17 | 3.2 |
| Type of tremor7: | |||||||
| Postural | 16 | Postural and kinetic6 | 9 | 15 | 19 | 34 | NK |
| Kinetic | 17 | 9 | 18 | 16 | 27 | ||
| Rest | 3 | 0 | 0 | 0 | 3 | ||
| Treatment (%) | 26 | 29 | 11 | 26.3 | 63.1 | 61 | 24.2 |
| Impairement (%) | 100 | 55 | NK | Yes6 | Yes6 | NK | NK |
[i] Qualitative data are presented as percentage (number of patients) and quantitative data as mean ±standard deviation [range] when available except for the type of tremor, where only number of patient is shown.
NK: not known; 1: onset was at birth in 7 children; 2: 2 years was the youngest presentation; 3: first degree parents only were reported ; 4: unknown percentage.