why does contralateral hemiplegia occurs in EXTRADURAL HAEMORRHAGE?

Answer 1

It wouldn't if the hemorrhage occurred below the brainstem, because at that point the motor paths have already crossed over. But extradural hemorrhage from the pons and upward will accumulate and essentially produce a mass-lesion, placing pressure on the motor neurons, resulting in dysfunction and eventually paralysis of the upper motor neurons. The reason that it is contralateral hemiplegia is that they cross over to the other side of the body at the pyramidal decussation in the medulla, and thus the right cerebral hemisphere is able to control the left-sided appendages, and vice-versa.

Answer 2

Extradural hemorrhage means that there has been bleeding inside the skull but outside the membrane that surrounds the brain. This puts harmful pressure on the brain and causes it to malfunction.
The pathways of the brain to the body are reversed so that the right brain controls the left body and left controls the right. That is why the half body weakness (hemiplegia) is reversed (contra). Hence, contralateral hemiplegia.

Answer 3

The pressure on the brain...it doesn't matter that it's extradural. The fluid presses against the skull and the brain, and since the brain is softer...it's the one that has to compress to displace that pressure.

Answer 4

What???