Syringobulbia is a medical condition when syrinxes

Syrinx (medicine)

In medicine, a syrinx is a rare, fluid-filled neuroglial cavity within the spinal cord , in the brain stem , or in the nerves of the elbow, usually in a young age.-Etymology:...

, or fluid filled cavities, affect the brainstem. This defect normally results from congenital abnormality, trauma

Physical trauma

Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...

 or tumor

Tumor

A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

growth.

Mostly occurs within the lower brainstem as a slit-like gap. This may affect one of more cranial nerves, resulting in various kinds of facial palsies. Sensory and motor nerve pathways may be affected by interruption and/or compression of nerves. This disorder is associated with syringomyelia, a syrinx limited to the spinal cord. (http://www.webmd.com/brain/syringobulbia)