2,537. A Punctured Membrane in the Skull

Hilchos Shechita 6:3

The brain has two membranes. If only the outer one, which is closer to the skull, is punctured, the animal remains permitted; if the inner membrane, which is closer to the brain, is punctured, the animal is a treifa. When it comes to the part where the brain reaches towards the spinal cord, i.e., under the glands where the neck starts, the rules are different: if the membranes are perforated past the glands, the animal remains permitted.

Hilchos Shechita 6:4

If the brain itself has been punctured or crushed, the animal is fit so long as the membrane is intact. However, if it pours like water or wax, then the animal is a treifa.