Is Arnold-Chiari malformation life threatening

Answer 1

Yes though it is extremely rare it has been proven that it can cause a rare form of sudden death syndrome by forming a lethal brain stem compression.

Chiari malformation can become a progressive disorder and lead to serious complications:

Hydrocephalus: accumulation of excess fluid within the brain

Syringomyelia: a cavity or cyst (syrinx) forms within the spinal column

Paralysis, which may occur due to the crowding and pressure on the spinal cord, tends to be permanent, even after treatment with surgery

Sudden Death: Lethal brain stem compression may accompany even relatively minor trauma associated with chronic cerebellar tonsillar herniation in patients with Chiari I malformation.

http://jpma.org.pk/full_article_text.php?article_id=1450

http://www.ncbi.nlm.nih.gov/pubmed/15613193

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3994690/

http://www.ncbi.nlm.nih.gov/pubmed/4041288