Figure 1
The four phenotypes of FTSDma are summarized in Figure 1a and 1b. Within each group (I through IV), we assigned patterns to specific combinations of movement, using a letter (a–i), attempting to use letters earlier in the alphabet for more commonly seen phenotypes. In Figure 1a, group I (precision grip involving the second and/or third finger) occurs in seven phenotypes, Ia–g, involving various combinations of flexion and extension. Group II refers to the power hand, involving combinations of the third, fourth and fifth finger (nine phenotypes, IIa–i). Group III (precision grip involving the thumb and/or the second finger) occurs in five phenotypes (IIIa–e). Group IV involves various proximal parts of the arm (ten phenotypes). We subdivided the complex phenotype of proximal dystonia of Group IV into ten phenotypes (IV—iv, v(a–e), vi(a), vii and ea). Still photographs from videos of examples of representative phenotypes appear in Figure 1b.
Table 5
Summary demographic features (hand affected, age at onset and evaluation, gender, trigger, spread of dystonia to other tasks or anatomic regions) are compared between the five major instrument classes, writer’s cramp, and other limb dystonia. Hand affected, age of onset and gender are compared to patients with FTSDma in the literature; age of onset, gender and spread to other tasks for WC reported in the literature; and age at onset for other dystonias reported in the literature. The right hand of keyboard and plucked string players is preferentially affected; percussion and woodwind are split evenly between the hands; and string players in the left hand more often than right. Keyboard, plucked string, drum, WC and OD experienced significant spread to other hand tasks, and overall anatomic spread was rare. Male predominance was present universally, with the except of lower occurrence in our series of WC.
| TASK | HAND | AGE ONSET | AGE EVALUTION | GENDER | TRIGGER | TASK SPREAD | ANATOMIC SPREAD |
|---|---|---|---|---|---|---|---|
| Keyboard | 65% R | 41.3 y | 48.3 y | 88% M | 15% | 40% | 10% |
| 25% L | |||||||
| 10% B | |||||||
| Plucked strings | 69.5% R | 38.7 yr | 47.6 yr | 87.5% M | 2.50% | 35% | 2.50% |
| 27.5% L | |||||||
| 5% | |||||||
| Percussion | 40% R | 43.8 yr | 47.3 yr | 93%M | 20% | 33% | 0% |
| 60% L | |||||||
| Woodwind | 42.5% R | 36.9 yr | 42.8 yr | 62.55% M | 10% | 15% | 10% |
| 47.5% L | |||||||
| 10% B | |||||||
| String | 27% R | 33.7 yr | 40.8 yr | 50% M | 13% | 13% | 0% |
| 73%L | |||||||
| Literature FTSDma | 74% R | 32.9 yr | 69% M | ||||
| 22% L | |||||||
| 4% B | |||||||
| WC | 82% R | 37.3 yr | 48.5 yr | 40% M | 6% | 42% | 4$ |
| 18% L | |||||||
| Literature WC | 32.3 yr | 71% M | 30% | ||||
| OD | 56% R | 36.8 yr | 43.5 yr | 69% M | 6% | 62.50% | 6% |
| 25% L | |||||||
| 19% B | |||||||
| Literature OD | 82% R | 42.4 yr | |||||
| 12% L |
Figure 2
Heat maps of the most common dystonic phenotypes are presented allowing easier visual comparison between instruments and also patients reported in the literature. The group identifier appears in the top row, and individual patients are represented by a filled in rectangle in each row. Patient numbers appearing in the far-left column of each figure refer to the number assigned in the corresponding demographics table. Yellow indicates left arm involvement; salmon indicates right arm involvement; orange indicates bilateral involvement. Group I appears red, group II green, group III blue, and group IV purple. Figure 2a summarizes keyboard phenomenology, involving groups I, II and III in both the study population and the literature. Figure 2b summarizes plucked string phenomenology, with the same pattern as keyboard in Figure 1 (absent reports of group III in the literature). Figure 2c summarizes drum phenomenology, involving groups I, II and IV in our patients and the literature. Figure 2d summarizes woodwind phenomenology, involving group II. Figure 2e summarizes string phenomenology, involving group II in the left arm and group IV in the right arm in our patients (no detailed phenomenology was available in patients reported in the literature).
Figure 3
Writer’s cramp Phenomenology. Heat maps of the most common dystonic phenotypes in our series and in the literature are presented for patients with writer’s cramp. Within our series, patients displayed group IV (entire arm involvement), isolated group III, or combinations of group II and III, III and IV, or all four group phenotypes. In patients reported in the literature, patients presented with combinations of groups I, II and III, with and without additional the phenotype of group IV.
Figure 4
Other dystonia Phenomenology. Heat maps of the most common dystonic phenotypes in our series and in the literature are presented for patients with Other dystonia. Within our series, patients displayed group IV alone, group IV in combination with group III and group II, and group III in combination with group I phenotypes. Most patients presented in the literature were classified as group IV.
Figure 5
Figure 5a summarizes patterns of activation of the hand and arm during awake motor cortex stimulation in man [69]. Three main patterns of activation were observed: involvement of the precision hand (digits 1, 2, 3) +/– wrist; involvement of the power hand (4, 5 (+/– 3)), often with wrist involvement; and proximal arm involvement (elbow or entire arm). Figure 5b illustrates the striking similarity in phenotypes between Woolsey’s M1 cortical stimulation patterns (diagram of hand and arm, with precision hand in blue (flexion) or red (extension); power hand in green; and wrist to proximal arm in purple. Eight examples of patterns from the dystonic repertoire are displayed in still photos from videos, with the corresponding Woolsey picture to the left.
Figure 6
Schematics of a proposed connectivity/anatomic model of FTSDma are summarized in Figure 6. Four critical cortical areas involved in motor planning and control of the arm are outlined in Figure 6a: inferior parietal lobule (IPL) in light purple; M1 motor (blue) and S1 sensory (red) primary homuncular cortices; and area F5 (light green). Figure 6b outlines a highly simplified connectivity diagram linking these areas. Peripheral sensory input from the arm and hand (from roots C5-T1) flows to S1 and to the IPL. The IPL connects sensory input with area F5, forming a bidirectional sensory-motor planning module. Outflow from this module leaves F5 and targets the homuncular motor cortex, which sends motor control commands to motor neurons in spinal cord regions C5-T1 (after modulation by basal ganglia and cerebellar circuitry (not shown)). Figure 6c illustrates the normal flow of sensory-motor integration, with a well-ordered set of commands from F5 to M1, and from M1 to the anterior horn cells of C5-T1, leading to efficient and arm movement with unconstrained degrees of freedom. In a dystonic musician (Figure 6d), sensory input and integration of IPL with F5 is disordered. As a result, there is a loss of degrees of freedom of motor control output from F5 to M1, a predominance of one output command from M1 to the motor endplates, and a predominant dystonic phenotype that overrides the normal diversity of hand movements. Figure 6e illustrates the impact of treatment (e.g. geste maneuvers, glove effect, lidocaine injection, hand fatigue with exertion, or BoNT injection) on the disordered network. The effect of treatment is to partially restore the balance of sensory-motor integration, improving (to at least some extent) the degrees of freedom of commands to M1. This results in improved diversity of outputs from the M1 cortex to the anterior horn cells of C5-T1, ameliorating the monolithic dystonic phenotype and partially restoring the degrees of freedom of motor control.