Loss of motor neuron. The brain has areas where the nerves that issue working signals to the muscles are located. For these nerves to grow and mature after conception, they need nutrients (oxygen, protein, carbohydrates) all brought to them by the normal flow of blood to their location. This is assured when blood flow in the placenta & brain is normal. Nerves die if nutrients are cut off, and this causes motor problems.
Brain-based. Cerebral palsy means " weakness that comes from the brain, " a categorical diagnosis. It can be from the way the brain formed, beginning in the first month of pregnancy. Any time before or after birth areas of the brain may have had insufficient oxygen, a stroke, or a bleed for a variety of reasons. Pediatric neurologists may be consulted to help find the cause.
Loss of motor neuron. It is not clear why the motor neurons do not develop properly, or if they develop but are damaged or destroyed during the pregnancy, but the diagnosis of cerebral palsy is applied when it seems evident that the cerebrum, the part of the brain with the motor cortex, is missing nerve tissue or it is not working right. Then the muscles don't get the right nerve signal, are weak, often tight.