Table S1.
Clinical protocols
| RR dog | On site observation of myoclonic seizures | Video documentation | Completed questionnaire | Pedigree available | Neuroimaging | CSF | Neurometabolic screening* | EEG | EEG with ILS |
| Case 1 | Yes | Yes | No | No | MRI | Yes | Yes | Yes | No |
| Case 2 | Yes | Yes | No | Yes | MRI | Yes | Yes | Yes† | No |
| Case 3 | Yes | Yes | No | No | CT | Yes | Yes | No | No |
| Case 4 | Yes | Yes | Yes | No | CT | Yes | Yes | Yes | No |
| Case 5 | Yes | No | Yes | No | CT, MRI | Yes | No | No | No |
| Case 6 | Yes | Yes | Yes | Yes | — | Yes | Yes | Yes | No |
| Case 7 | Yes | No | No | No | MRI | Yes | No | No | No |
| Case 8 | Yes | No | No | Yes | MRI | Yes | Yes | No | No |
| Case 9 | Yes | Yes | Yes | Yes | — | No | No | Yes | No |
| Case 10 | Yes | Yes | Yes | Yes | — | No | No | Yes | No |
| Case 11 | Yes | Yes | Yes | Yes | — | No | Yes | Yes | No |
| Case 12 | Yes | Yes | Yes | Yes | — | No | Yes | Yes | No |
| Case 13 | Yes | Yes | Yes | Yes | MRI | Yes | Yes | Yes‡ | Yes |
| Case 14 | No§ | No§ | Yes | Yes | CT | Yes | No | No | No |
| Case 15 | Yes | Yes | Yes | No | MRI | Yes | No | Yes‡ | No |
| Case 16 | Yes | Yes | Yes | Yes | CT | Yes | No | No | No |
| Case 17 | Yes | Yes | Yes | No | MRI | Yes | No | Yes‡ | No |
| Case 18 | Yes | Yes | Yes | No | MRI | Yes | Yes | No | No |
| Case 19 | Yes | Yes | Yes | Yes | MRI | Yes | No | Yes | No |
| Case 20 | Yes | Yes | Yes | Yes | — | No | No | Yes | Yes |
| Case 21 | Yes | Yes | No | Yes | — | No | No | Yes | Yes |
| Case 22 | No | Yes | No | Yes | — | No | No | Yes | Yes |
| Case 23 | Yes | Yes | Yes | Yes | CT, MRI | Yes | No | Yes | Yes |
| Case 24 | Yes | Yes | Yes | Yes | CT, MRI | Yes | No | Yes | Yes |
| Control 1 | — | — | — | No | — | — | No | Yes | No |
| Control 2 | — | — | — | No | — | — | Yes | Yes‡ | No |
| Control 3 | — | — | — | No | — | — | No | Yes | No |
| Control 4 | — | — | — | No | — | — | No | Yes | No |
| Control 5 | — | — | — | No | — | — | No | Yes | No |
| Control 6 | — | — | — | No | — | — | No | Yes | No |
| Control 7 | — | — | — | No | — | — | No | Yes | Yes |
| Control 8 | — | — | — | Yes | — | — | No | Yes | Yes |
| Control 9 | — | — | — | Yes | — | — | No | Yes | Yes |
| Control 10 | — | — | — | Yes | — | — | No | Yes | Yes |
| Control 11 | — | No | Yes | Yes | MRI | Yes | No | Yes† | No |
Summary of the used diagnostic investigation protocols. ILS, intermittent light stimulation.
*
Neurometabolic screening: urinary amino acids and urinary organic acids; cases 2, 6, and 13 also serum amino acids.
†
Recording upon awakening from general anesthesia (isoflurane, propofol).
‡
Sedation for electrode placement with 0.015 mg/kg dexmedetomidine, reversal with 0.15 mg/kg atipamezole.
§
This dog was included despite lack of on-site observation or video documentation of myoclonic twitches, as one sibling (dog 13) was affected as well and those two dogs were possessed by the same owner.