Electrodiagnostic results from 20 patients with inclusion body myositis
| Patient No | Referring diagnosis | EMG diagnosis | MNC | SNC | Muscle | MUPs (n) | Polys (%) | Duration (ms) (% normal) | Duration of simple MUPs (% of normal) | Amplitude (μV) | Spontaneous activity | Recruitment |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | IBM | Myopathy | N | N | Tib ant | 20 | 15 | 10 (68) | 9.9 (67) | 330 | 1+fibs | 4, 6 |
| 2 | ALS | Myopathy | ↓a (p) | N | Ttib ant | 20 | 30 | 9.5 (62) | 8.8 (57) | 496 | 1-3+fibs/1+fascics | 2, 5, 6 |
| 3 | MND | Myopathy | N | N | Vas lat | 28 | 21 | 11.3 (73) | 10.6 (69) | 329 | 1+fibs | 1, 4 |
| Biceps | 24 | 0 | 10.2 (84) | 10.2 (84) | 147 | |||||||
| Deltoid | 25 | 8 | 11.9 (96) | 11.4 (93) | 215 | |||||||
| 4 | ALS vN | Myopathy | N | N | Vas lat | 17 | 12 | 17.6 (114) | 17.7 (115) | 910 | 2+fibs/1+fascics | 1, 3, 4, 5 |
| Tib ant | 15 | 15 | 7.8 (52) | 6.4 (43) | 641 | |||||||
| 5 | PM | Myopathy | N | N | Biceps | 20 | 10 | 7.7 (60) | 7.9 (62) | 419 | 2+fibs | 4 |
| 6 | Myopathy | Myopathy | N | N | Biceps | 20 | 10 | 8.4 (74) | 8.5 (75) | 1-2+fibs/fascics/myo- kymia/CRDS | 5 | |
| 7 | Myopathy | Myopathy | N | N | Biceps | 20 | 50 | 8.4 (68) | 8.4 (68) | 227 | 1-2+fibs | 4, 6 |
| 8 | PM | Myopathy | N | N | Biceps | 20 | 25 | 8.1 (65) | 7.4 (60) | 514 | fibs | 4 |
| 9 | Myopathy | Myopathy | <a (t) | N | Vas lat | 18 | 44 | 9.6 (62) | 9.4 (60) | 749 | 1+fibs/2+fascics/C RDS | 1, 2, 4, 6 |
| 10 | SMAv myopathy | MND | ↓a(u, p, t) ↓cv(t) | ↓CV(m, u, s) | P | Long | 1-2+fibs/1-2+fascics/CRDS | 2, 3 | ||||
| SMA | Myopathy | Not done | Not done | Biceps | 21 | 24 | 8.4 (68) | 6.7 (54) | 193 | rare fibs/CRDS | 2, 4 | |
| Vas lat | 18 | 39 | 11.3 (72) | 11.6 (74) | 374 | |||||||
| 11 | Myopathy | Myopathy | ↓a(p) | N | Tib ant | 20 | 30 | 20 (136) | 8 (54) | 455 | 2+fibs | 1, 2, 5 |
| 12 | Myopathy | Myopathy | N | N | Vas lat | 28 | 29 | 14.9 (102) | 13.9 (95) | 729 | 1+fibs | 1, 2 |
| Tib ant | 22 | 50 | 12.7 (89) | 9.4 (66) | 358 | |||||||
| 13 | ALS | Myopathy | N | N | Biceps | 20 | 60 | 11.3 (98) | 6.9 (60) | 589 | 1-2+fibs/fascics/CR DS | 5 |
| 14 | ALS | MND | N | N | — | P | Long | I | 1-2+fibs/1-3+fascics | 2, 3 | ||
| 15 | ALS | SMN | ↓a(u, p) | ↓CV(m, u, s), <a(m, u) | — | P | I | 1-2+fibs/fascics | 2, 3 | |||
| After bx | ALS v N | SMN | ↓CV(m, p), <a(p) | ↓cv,a(m,u), ab (s) | — | P | I | 1-2+fibs/1+fascics | 2, 3 | |||
| Myopathy | Myo/SMN | ↓a(p, t) | ↓CV, a(m), ab(s) | — | P | R | R,I | 1-2+fibs | 2, 4 | |||
| Myopathy | Myo/SMN | ↓CV(p, t), ↓a(p, t) | ↓CV, a(m, u), ab(s) | — | ||||||||
| 16 | IBM vMND | Myopathy | N | N | N | R | R | 1+fibs | 2, 4 | |||
| 17 | PM vPN | Non-diag | N | N | — | P | N | N | None | 2 | ||
| 18 | MND | MND | N | ab(s) | — | P | I | 1-2+fibs | 1, 2, 4, 6 | |||
| 19 | Myopathy | Normal | N | N | — | N | N | N | None | 1 | ||
| 20 | Myositis | Normal | N | Ab(s) | — | N | N | N | None | 1, 6 |
a=amplitude; ab=absent; ALS=amyotrophic lateral sclerosis; CRDS=complex repetitive discharges; fascics=fasciculations; fibs=fibrillations and positive sharp waves; CV=conduction velocity; I=increased; IBM=inclusion body myositis; m=median nerve; MND=motor neuron disease; N=normal; np=neuropathy; p=peroneal; PM=polymyositis; R=reduced; s=sural; SMA=spinal muscular atrophy; SMN=sensorimotor neuropathy; t=tibial nerve; u=ulnar nerve; 1=full recruitment on maximal effort; 2=reduced recruitment on maximal effort; 3=discrete recruitment on maximal effort; 4=full recruitment on submaximal effort; 5=full recruitment on maximal effort in a weak muscle; 6=reduced recruitment on submaximal effort.