What exactly is cerebellar tonsillar ectopia?

Tonsillar ectopia: The cerebellum is at the lower back of your brain, and is mainly responsible for motor coordination. The tonsils are at the midline of your cerebellum and sometimes they can extend a bit lower than normal. That's called tonsillar ectopia. They may be asymptomatic, or they could cause symptoms like headache, pain, and other neurologic symptoms.