| Group | Subgroups | Number of studies | RR | 95%CI | I2 | P-interaction |
| RCTs (n = 4 studies) | ||||||
| Overall | NA | 4 | 1.06 | 0.62, 1.80 | 28% | NA |
| Cohort studies (n = 11 studies) | ||||||
| Overall | NA | 11 | 0.75 | 0.35, 0.16 | 71% | NA |
| Age | Children | 7 | 0.71 | 0.29, 1.76 | 78% | 0.45 |
| Adults | 2 | 0.82 | 0.24, 2.76 | 0% | ||
| Hydrocephalus type | Obstructive | 7 | 0.65 | 0.23, 1.84 | 71% | 0.51 |
| Both | 2 | 1.14 | 0.11, 11.45 | 59% | ||
| Country | Developed | 4 | 1.02 | 0.54, 1.94 | 0% | 0.65 |
| Developing | 5 | 0.6 | 0.17, 2.09 | 79% | ||