Table 2:
MR imaging characteristics and temporal evolution of new lesions in MELAS
| Sequence | Intensity | No. of Lesions: Deep | No. of Lesions: Cortical |
|---|---|---|---|
| Acute (first week) | Total: 5 | Total: 36 | |
| T1 (spin-echo) | ↓ | 0 | 24 |
| T2 (spin-echo) | ↑ | 5 | 36 |
| T2 sparing of superficial cortex | 23 | ||
| T2 FLAIR | ↑ | 5 | 36 |
| DWI (b = 1000) | ↑ | 0 | 34 |
| ADC | ↓ | 0 | 30 |
| SWI | ↓ | 0 | 0 |
| Subacute (second-to-fourth weeks) | |||
| Prior low ADC | 0 | 30 | |
| Follow-up imaging available | 0 | 29 | |
| T1 | ↑ | 12 | |
| T2: black toenail sign | ↓ | 21 | |
| SWI | ↓ | 7 | |
| Prior normal/high ADC | 5 | 6 | |
| Follow-up imaging available | 5 | 6 | |
| T1 | ↑ | 0 | 0 |
| T2: black toenail | ↓ | 0 | 0 |
| SWI | ↓ | 0 | 0 |
| Chronic (>3 mo) | |||
| Prior low ADC | 0 | 30 | |
| Follow-up imaging available | 0 | 19 | |
| Volume loss | 19 | ||
| Prior normal/high ADC | 5 | 6 | |
| Follow-up imaging available | 4 | 4 | |
| Volume loss | 2 | 0 | |
| 1H-MRS performed | Doublet at 1.3 ppm | 5 Patients | |
| Long TE (288 ms) | Elevated | 5 Patients | |
| Intermediate TE (144 ms) | Inverted | 5 Patients | |
| Affected white matter | 5 Patients | ||
| Nonaffected white matter | 3 Patients |
Note:—↓ indicates hypointense signal; ↑, hyperintense signal.