Common causes
Alcoholic liver disease (ALD, or alcoholic cirrhosis) develops for 10–20% of individuals who drink heavily for a decade or more. Alcohol seems to injure the liver by blocking the normal metabolism of protein, fats, and carbohydrates. This injury happens through the formation of acetaldehyde from alcohol. Acetaldehyde is reactive and leads to the accumulation of other reactive products in the liver. People with ALD may also have concurrent alcoholic hepatitis. Associated symptoms are fever, hepatomegaly, jaundice, and anorexia. AST and ALT blood levels are both elevated, but at less than 300 IU/liter, with an AST:ALT ratio > 2.0, a value rarely seen in other liver diseases. In the United States, 40% of cirrhosis-related deaths are due to alcohol. In non-alcoholic fatty liver disease (NAFLD), fat builds up in the liver and eventually causes scar tissue. This type of disorder can be caused by obesity, diabetes, malnutrition, coronary artery disease, and steroids. Though similar in signs to alcoholic liver disease, no history of notable alcohol use is found. Blood tests and medical imaging are used to diagnose NAFLD and NASH, and sometimes a liver biopsy is needed. Chronic hepatitis C, an infection with the hepatitis C virus, causes inflammation of the liver and a variable grade of damage to the organ. Over several decades, this inflammation and damage can lead to cirrhosis. Among patients with chronic hepatitis C, 20–30% develop cirrhosis. Cirrhosis caused by hepatitis C and alcoholic liver disease are the most common reasons for liver transplant.
In this type, the hypoplasia of the cerebellar vermis does not reach past the horizontal midline of the fourth ventricle, and the posterior fossa is also not as large. The authors noted that this form would previously have been classified as simply mega–cisterna magna. In 1999, Calabró et al. first used the phrase Dandy–Walker continuum when referring to proposals that a condition known as Blakes pouch cyst falls under the umbrella of the Dandy–Walker complex proposed by Barkovich. Later authors would put these terms and systems under intense scrutiny and state that they added considerable confusion to the diagnosis of DWM. However, they remain commonly used.In 2011, Spennato et al. came up with a set of criteria based on Klein et al. (2003) that they considered necessary for diagnosis of DWM:
The lower portion of the cerebellar vermis is absent to varying degrees (three quarters, one half or one quarter missing). The posterior fossa (the space behind the cerebellum) is enlarged, and its cerebrospinal fluid flow is continuous with that of the fourth ventricle. The rest of the cerebellar vermis is hypoplastic and is pushed upwards and rotated forwards due to the enlarged posterior fossa. The cerebellar hemispheres are pushed forwards and to the side by the enlarged posterior fossa. The angle at the centre of the cerebellar vermis (representing the location of the fastigial nucleus) is large, giving a flattened appearance to the bottom of the vermis, or the fastigial nucleus is absent entirely.