Symptoms arise from dysfunction of brainstem and lower cranial nerves. Chiari type III and IV malformations are exceedingly rare and generally incompatible with life and are, therefore, of scant clinical significance.

What are the risks? No surgery is without risks. General complications of any surgery include bleeding, infection, blood clots, stroke, reactions to anesthesia, and death (rare).

The hospital stay following a Chiari decompression is generally 3 to 4 days. An experienced pediatric ICU and pediatrics team will ensure that the common postoperative symptoms of headache, neck stiffness, nausea and vomiting are well-controlled.

Chiari malformation (kee-AH-ree mal-for-MAY-shun) is a condition in which brain tissue extends into your spinal canal. It occurs when part of your skull is abnormally small or misshapen, pressing on your brain and forcing it downward. Chiari malformation type I develops as the skull and brain are growing.

Chiari I malformations that are asymptomatic should be left alone (this involves the majority of Chiari malformations). There is no indication for “prophylactic” surgery on these. If the malformation is defined as symptomatic, or is causing a syrinx, treatment is usually recommended.

The term “Arnold-Chiari” was latter applied to the Chiari type II malformation. These malformations, along with syringomyelia and hydromyelia, two closely associated conditions, are described below. The cerebellum controls the coordination of motion and is normally located inside the base of the skull, in what is referred to as the posterior fossa.

Chiari III involves herniation of the hindbrain (cerebellum with or without the brainstem) into a low occipital or high cervical meningoencephalocele. Chiari IV is now considered obsolete.