Table 1.
Characteristics of included studies
| Type of study | Type of population | Measurement place | No. of participant | Mean age or range | Included in analysisa | |
|---|---|---|---|---|---|---|
| Albeck [33] | Prospective, observational | Healthy | Lumbar | 8 | 22–28 | Yes |
| Albeck [34] | Prospective, observational | Healthy | Lumbar | 52 | 60 | Yes |
| Andresen [46] | Prospective, observational | Pseudo-healthy | Parenchymal | 4 | 67 | Yes |
| Avery [63] | Prospective, observational | Pseudo-healthy | Lumbar | 197 | 1–18 | Yes |
| Avery [70] | Case report, literature review | Pseudo-healthy | Lumbar | 1 | 12 | Yes |
| Beck [66] | Prospective, observational | Pseudo-healthy | Lumbar | 17 | – | Yes |
| Blomquist [73] | Prospective, observational | Pseudo-healthy | Lumbar | 18 | 0–15 | Yes |
| Bono [67] | Prospective, observational | Pseudo-healthy | Lumbar | 111 | 40 | Yes |
| Bø [69] | Prospective, observational | Pseudo-healthy | Lumbar | 348 | 47 | Yes |
| Chiari [76] | Retrospective, observational | Pseudo-healthy | Parenchymal | 41 | 43 | Yes |
| Chapman [21] | Prospective, observational | Pseudo-healthy | Ventricular | 5 | 28 | Yes |
| Corbett [25] | Prospective, observational | Healthy | Lumbar | 15 | – | Yes |
| Eklund [32] | Prospective, observational | Healthy | Lumbar | 11 | 46 | Yes |
| Ekstedt [9] | Prospective, observational | Pseudo-healthy | Lumbar | 100 | – | Yes |
| Ellis [24] | Prospective, observational | Pseudo-healthy | Lumbar | 33 | 8 | Yes |
| Fleischman [68] | Retrospective, observational | Pseudo-healthy | Lumbar | 12,118 | 54 | Yes |
| Friden [72] | Retrospective, observational | Pseudo-healthy | Lumbar | 150 | – | Yes |
| Gilland [8] | Retrospective, observational | Healthy | Lumbar | 15 | 25 | Yes |
| Gilland [7] | Prospective, observational | Healthy | Lumbar | 31 | 23 | Yes |
| Gonzalez [62] | Prospective, case–control | Pseudo-healthy | Lumbar | 28 | 41 | No |
| Hannerz [35] | Prospective, observational | Healthy | Lumbar | 19 | 52 | Yes |
| Kaiser [60] | Prospective, observational | Pseudo-healthy | Lumbar | 49 | 30 (24–41) weeks | Yes |
| Kawasaki [61] | Retrospective, case–control | Pseudo-healthy | Lumbar | 1 | 51 | Yes |
| Lakke [36] | Prospective, observational | Healthy | Lumbar | 34 | – | No |
| Langvatn [77] | Retrospective, observational | Pseudo-healthy | Parenchymal | 12 | 3 | Yes |
| Lawley [56] | Prospective, observational | Pseudo-healthy | Ventricular | 8 | 35 | Yes |
| Lee [59] | Retrospective, observational | Pseudo-healthy | Lumbar | 44 | 9 | Yes |
| Lundberg [57] | Prospective, case–control | Pseudo-healthy | Ventricular | 1 | 45 | No |
| Magneli [54] | Prospective, case–control | Pseudo-healthy | Parenchymal | 1 | 8 | Yes |
| Mahr [78] | Prospective, observational | Pseudo-healthy | Parenchymal | 35 | 73 | No |
| Malm [5] | Prospective, observational | Healthy | Lumbar | 40 | 70 | Yes |
| Martin [79] | Prospective, case–control | Pseudo-healthy | Intracranial | 1 | 19 | No |
| Pedersen [41] | Retrospective, observational | Pseudo-healthy | Parenchymal | 35 | 4–85 | Yes |
| Petersen [55] | Prospective, observational | Pseudo-healthy | Parenchymal and ventricular | 11 | 44 | Yes |
| Puhringer [37] | Prospective, observational | Healthy | Lumbar | 5 | 25–38 | Yes |
| Purvin [52] | Retrospecitve, case–control | Pseudo-healthy | Lumbar | – | – | No |
| Riedel [42] | Prospective, observational | Pseudo-healthy | Parenchymal | 44 | 60 | Yes |
| Schwartz [58] | Prospective, observational | Pseudo-healthy | Lumbar | 55 | 56 | Yes |
| Shapiro [29] | Prospective, observational | Healthy | Lumbar | 23 | 0–55 | Yes |
| Skau [30] | Prospective, case–control | Healthy | Lumbar | 20 | – | Yes |
| Skipper [31] | Retrospective, case–control | Healthy | Lumbar | 24 | 33 | No |
| Sugita [64] | Prospective, case–control | Pseudo-healthy | Lumbar | 3 | 38 | No |
| Whiteley [11] | Retrospective, observational | Pseudo-healthy | Lumbar | 242 | – | Yes |
| Wibroe [65] | Prospective, observational | Pseudo-healthy | Lumbar | 28 | 37 | Yes |
a Studies were not included in the analysis, if they provided insufficient stastical data to calculate a mean and standard deviation