Fourth ventricle (25) (66%) | Unilateral recess | *n* = 7 | Plus uni CPA | *n* = 1 | 2 |

| | | No | *n* = 6 | 1 |

| Bilateral recesses | *n* = 16 | Plus uni CPA | *n* = 4 | 1 |

| | | Plus bi CPA | *n* = 0 | 0 |

| | | No | *n* = 12 | 0 |

| No extension | *n* = 2 | | | 0 |

Cerebellar vermis (3) (8%) | Unilateral recess | *n* = 1 | | | 1 |

| Bilateral recesses | *n* = 1 | | | 0 |

| Fourth ventricle only | *n* = 1 | | | 0 |

| No extension | *n* = 0 | | | 0 |

CPA (5) (13%) | Unilateral recess | *n* = 4 | Plus fourth ventricle | *n* = 4 | 2 |

| Bilateral recesses | *n* = 0 | | | 2 |

| No extension | *n* = 1 | | | 2 |

Deep WM (3) (8%) | Unilateral recess | *n* = 1 | Plus uni CPA | *n* = 1 | 2 |

| Bilateral recesses | *n* = 0 | | | 2 |

| Fourth ventricle only | *n* = 1 | | | 2 |

| No extension | *n* = 1 | | | |

Cerebellar hemisphere (2) (5%) | Unilateral recess | *n* = 2 | Plus uni CPA | *n* = 1 | 2 |

| Bilateral recesses | *n* = 0 | | | 2 |

| Fourth ventricle only | *n* = 0 | | | 2 |

| No extension | *n* = 0 | | | 2 |