Different Types:
Type 0: No herniation of cerebellum, but there is some obvious crowding into the foramen magnum.
Type I--AKA--Arnold Chiari Malformation: Most common of all types, signified as a 5mm protrusion of cerebellum into the spinal canal, may or may not experience symptoms.
Type II: Protrusion of brainstem (medulla oblongata) and ventrical into the spinal canal, commonly seen with spina bifida and meningocele.
Type III: Involves an area of the spinal canal that failed to close up, the cerebellum and brainstem protrude out through the opening. This type is rare, often resulting in death. The ones who do survive suffer with severe neurological deficits, usually other birth defects, and often hydrocephalus.
Type IV: Most rare of all types. The cerebellum does not fully develop and there is usually some other brain or medulla oblongata malformation that is present as well. Very rarely does person survive infancy.
Diagnosis: Basic neurological testing (sensation, walking, reflexes, coordination, etc.) is obtained in conjunction with an MRI (the only modality that provides a definitive diagnosis.)
Prognosis: It's difficult to determine how Chiari malformation will progress. Greater than 80% obtained improvement of symptoms and some were symptom free. In cases anatomical changes and brain damage, these effects were irreversible.
Symptoms: Symptoms range from no symptoms at all to mild or moderate.
Some common symptoms may include but not limited to: headache, migraines, "lump in throat" feeling, burning sensation in upper extremeties, memory loss, decrease in muscle tone, back pain, ataxia, fatigue, dizziness, and decreased sensation of touch and temperature differences--arms and legs in particular.
Symptoms specific to Type II: Change in breathing patterns, depressed gag reflex, nystagmus (rapid movement of the eyes), upper body strength diminishes. These symptoms occur in conjunction with above symptoms.
Symptoms that require immediate medical attention include nausea and vomitting, sleep apnea, and dyshpagia.
Treatment: Treatment of symptoms is beneficial for the most part depending on the type and severity of the symptoms. Surgical intervention is usually required at some point.
A Few Other Pathologies That May Be Involved:
Hydrocephalus: Abnormal accumulation of CSF in the brain.
Ehler's Danlos: A genetic disorder, affects the connective tissues throughout the entire body. The joints, skin, bones, vessels, organs, etc., have little or no strength structure to them.
Syringomyelia: A chronic condition where a pocket (AKA-syrinx) forms within the spinal cord itself. Over time the pocket grows and compresses on the spinal cord causing neurological symptoms such as pain in back, neck, and upper and/or lower extremeites, weakness, headaches, etc.
Tethered Spinal Cord Syndrome: The spinal cord is essentially tied to the inside of the spinal canal restricting movement. Eventually the spinal cord becomes stretched out causing neurological problems.
References:
Arnold chiari malformation and syringomyelia. (2011, January). Retrieved from http://www.chiariaustralia.com
Chiari malformation type 1.Retrieved from http://mtn.missouri.edu
Khouri, Chaouki. (2010, September). Chiari malformations. Retrieved from http://www.uptodate.com
Office of Communications and Public Liason, National Institute of Neurological Disorders and Stroke. (2011). Ninds chiari malformation information page Bethesda, MD: Retrieved from http://www.ninds.nih.gov/
Shinagare, A. B., & Patil, N. K. (2008). Imaging of congenital malformations of brain: a pictorial essay. The Internet Journal of Radiology, 9(1), Retrieved from http://www.ispub.com
Tew, John. M., & Nancy, McMahon. (2010, February). Chiari 1 malformation [Web log message]. Retrieved from http://www.mayfieldclinic.com
Infant with a meningocele.