Association of all lesion characteristics with asymptomatic PML lesions
| Lesion characteristics | Times rated in PML lesions* n=105 | Times rated in MS lesions* n=110 | OR for PML† | 95% CI | p Value‡ |
|---|---|---|---|---|---|
| General characteristics | |||||
| Bilateral hemispheric involvement§ | 41 | 62 | 0.50 | 0.15 to 1.6 | 0.24 |
| Unilobar lesion dissemination¶ | 41 | 29 | 2.3 | 0.74 to 7.5 | 0.30 |
| Multilobar lesion dissemination¶ | 23 | 13 | 2.9 | 0.57 to 15.1 | 0.30 |
| Widespread lesion dissemination | 41 | 68 | reference | ||
| Mass effect | 1 | 0 | NA | NA | NA** |
| Signs of oedema | 1 | 2 | 0.5 | 0.041 to 6.6 | 0.62 |
| Lesion size >3 cm†† | 33 | 0 | NA | NA | <0.001‡‡ |
| Lesion location | |||||
| Frontal lobe | 49 | 40 | 1.5 | 0.54 to 4.3 | 0.42 |
| Parietal lobe | 13 | 21 | 0.60 | 0.20 to 1.8 | 0.35 |
| Occipital lobe | 10 | 3 | 3.8 | 0.78 to 18.1 | 0.099 |
| Temporal lobe | 6 | 10 | 0.61 | 0.17 to 2.1 | 0.44 |
| Corpus callosum | 0 | 5 | NA | NA | 0.060§§ |
| Thalamus | 5 | 0 | NA | NA | 0.026§§ |
| Basal ganglia | 4 | 10 | 0.40 | 0.077 to 2.0 | 0.27 |
| Brainstem | 12 | 15 | 0.82 | 0.21 to 3.3 | 0.77 |
| Cerebellum | 18 | 5 | 4.3 | 0.89 to 21.3 | 0.070 |
| Tissue involvement | |||||
| Juxtacortical WM | 63 | 32 | 3.6 | 1.2 to 11.1 | 0.023 |
| Deep WM | 47 | 53 | 0.82 | 0.36 to 1.9 | 0.64 |
| Periventricular WM | 1 | 27 | 0.028 | 0.0036 to 0.22 | 0.001 |
| Cortical GM | 23 | 2 | 14.8 | 3.6 to 61.1 | <0.001 |
| Deep GM | 13 | 8 | 1.8 | 0.38 to 8.1 | 0.47 |
| Lesion appearance | |||||
| Focal lesion appearance¶¶ | 47 | 107 | 0.026 | 0.0081 to 0.083 | <0.001 |
| Lesion borders | n=103 | n=108 | |||
| Ill-defined border towards WM*** | 45 | 13 | 9.1 | 4.0 to 20.5 | <0.001 |
| Mixed border towards WM*** | 26 | 11 | 6.2 | 1.9 to 20.5 | <0.001 |
| Sharp border towards WM | 32 | 84 | reference | ||
| n=98 | n=102 | ||||
| Ill-defined border towards GM*** | 20 | 10 | 3.7 | 1.6 to 8.8 | 0.001 |
| Mixed border towards GM*** | 36 | 14 | 4.8 | 1.6 to 14.5 | 0.001 |
| Sharp border towards GM | 42 | 78 | reference | ||
| Specific PML characteristics | |||||
| Presence of punctate T2 lesions††† | 56 | 1 | 135.6 | 18.9 to 974.7 | <0.001 |
| MRI sequences and contrast enhancement | |||||
| T1 hypointense‡‡‡ | 31 (n=74) | 47 (n=71) | 0.37 | 0.11 to 1.2 | 0.107 |
| T2 hyperintense‡‡‡ | 110 (n=110) | 92 (n=93) | NA | NA | NA |
| FLAIR hyperintense‡‡‡ | 105 (n=108) | 102 (n=103) | 2.9 | 0.25 to 34.5 | 0.397 |
| Presence of contrast enhancement | 23 (n=92) | 2 (n=59) | 9.5 | 1.1 to 82.2 | 0.041 |
Bold values are statistically significant.
*Rated by four readers in 41 patients (21 with PML lesion(s) and 20 with new MS lesion(s)).
†OR>1 is associated with PML lesions, OR<1 is associated with new MS lesions.
‡For test of model effects.
§Compared to ‘unilateral hemispheric involvement’.
¶Compared to ‘widespread lesion dissemination’.
**Mass effect was rated as present once, resulting in complete data separation.
††Compared to ‘lesion size <3 cm’.
‡‡Calculated by Pearson χ2.
§§Calculated by Fisher's exact test because of complete data separation (ie, in either the PML or the MS lesion group the characteristic is either present or absent for all cases), and thereby ignoring the repeated scorings within a patient.
¶¶Compared to ‘non-focal appearance’ (ie, rated as: diffuse, confluent irregular or infiltrative appearance).
***Compared to ‘sharp borders’.
†††Defined as punctiform T2/FLAIR hyperintense lesions in the vicinity of the main PML lesions recently described as ‘milky way appearance’ and/or punctiform T2/FLAIR hyperintense lesions with a perivascular spread (<5 mm in diameter).
‡‡‡Compared to isointense/not visible on this sequence.
FLAIR, fluid-attenuated inversion recovery; GM, grey matter; MS, multiple sclerosis; NA, not applicable; PML, progressive multifocal leukoencephalopathy; WM, white matter.