Table 1.
Characteristics of descriptive studies are included along with the estimated risk of bias
| Author (year) | AITA | Sample size | Incidence | Lower CI | Upper CI | Weight | Status | Ethnicity | Mode of investigation | Risk of bias |
|---|---|---|---|---|---|---|---|---|---|---|
| Allen (1991) | 27 | 100 | 0.27 | 0.1922 | 0.3651 | 3.7374 | Healthy | North American | Cadaveric | Low |
| Belkovsky (2019) | 12 | 57 | 0.2105 | 0.1236 | 0.3352 | 3.2324 | Healthy | South American | Cadaveric | Moderate |
| Borghei (2020) | 42 | 402 | 0.1045 | 0.0781 | 0.1384 | 4.0136 | Healthy | North American | MRI | Low |
| Borghei (2021a) | 179 | 1410 | 0.127 | 0.1106 | 0.1454 | 4.278 | Healthy | North American | MRI | Low |
| Borghei (2021b) | 11 | 90 | 0.1222 | 0.069 | 0.2074 | 3.2483 | Healthy | North American | MRI | Low |
| Damle (2017) | 11 | 233 | 0.0472 | 0.0263 | 0.0832 | 3.3153 | Healthy | North American | MRI | Low |
| Davie & Baldwin (1967) | 44 | 111 | 0.3964 | 0.3099 | 0.49 | 3.8822 | Neuropsychiatric | European | Pneumoencephalogram | Low |
| Davie & Baldwin (1967) | 4 | 20 | 0.2 | 0.0771 | 0.4278 | 2.1405 | Healthy | European | Cadaveric | High |
| Lansdell (1972) | 28 | 74 | 0.3784 | 0.2756 | 0.4933 | 3.6672 | Neuropsychiatric | North American | Pneumoencephalogram | High |
| Macedo (1889)* | 43 | 215 | 0.2 | 0.1518 | 0.2588 | 3.9834 | Healthy | European | Cadaveric | Unclear |
| Malobabic (1987) | 11 | 50 | 0.22 | 0.1262 | 0.3551 | 3.1471 | Healthy | European | Cadaveric | Moderate |
| Miró-Padilla (2022) | 31 | 240 | 0.1292 | 0.0923 | 0.1778 | 3.8892 | Healthy | European | MRI | Low |
| Morel (1947) | 166 | 823 | 0.2017 | 0.1757 | 0.2305 | 4.262 | Neuropsychiatric | European | Cadaveric | Unclear |
| Morel & Weissfeilar (1931)* | 32 | 175 | 0.1829 | 0.1323 | 0.2472 | 3.8754 | Healthy | European | Cadaveric | Unclear |
| Park (1993) | 17 | 146 | 0.1164 | 0.0736 | 0.1793 | 3.576 | Healthy | Asian | Cadaveric | Low |
| Parra (2021) | 16 | 31 | 0.5161 | 0.3453 | 0.6833 | 3.0546 | Healthy | South American | Cadaveric | Moderate |
| Patra (2022) | 7 | 50 | 0.14 | 0.0682 | 0.2657 | 2.8126 | Healthy | Asian | Cadaveric | Moderate |
| Patra (2022) | 6 | 50 | 0.12 | 0.0549 | 0.2424 | 2.6788 | healthy | Asian | MRI | Moderate |
| Pavlovic (2020) | 8 | 41 | 0.1951 | 0.1007 | 0.3442 | 2.8793 | Healthy | European | Cadaveric | Low |
| Rabl (1958) | 292 | 921 | 0.317 | 0.2878 | 0.3478 | 4.2974 | Neuropsychiatric | European | Cadaveric | Moderate |
| Samra & Cooper (1968) | 5 | 32 | 0.1562 | 0.0666 | 0.3247 | 2.4412 | Healthy | European | Cadaveric | Moderate |
| Samra & Cooper (1968) | 146 | 860 | 0.1698 | 0.1461 | 0.1964 | 4.2523 | Healthy | European | Ventriculographic | Unclear |
| Sen (2005) | 14 | 161 | 0.087 | 0.0522 | 0.1415 | 3.4658 | Healthy | Asian | MRI | Low |
| Tenchini (1882)* | 20 | 100 | 0.2 | 0.1328 | 0.2898 | 3.6162 | Healthy | European | Cadaveric | Unclear |
| Tsuneda (1935) | 19 | 100 | 0.19 | 0.1246 | 0.2788 | 3.5916 | Neuropsychiatric | Asian | Cadaveric | Moderate |
| Tsutsumi (2021) | 20 | 205 | 0.0976 | 0.0638 | 0.1464 | 3.6883 | Healthy | Asian | MRI | Low |
| Viller (1887)* | 5 | 21 | 0.2381 | 0.1027 | 0.4603 | 2.3307 | Healthy | European | Cadaveric | Unclear |
| Wenzel (1812)* | 10 | 66 | 0.1515 | 0.0835 | 0.2592 | 3.1373 | Healthy | European | Cadaveric | Unclear |
| Yasaka (2018) | 15 | 153 | 0.098 | 0.06 | 0.1563 | 3.5058 | Healthy | Asian | MRI | Low |
| Random-effects model | 1241 | 6937 | 0.1759 | 0.1457 | 0.2108 | 100 |
*Data Collected from Samra and Cooper (1968); AITA: Absent interthalamic adhesion. CI: Confidence interval, MRI: Magnetic resonance imaging