such as magnetic resonance imaging (MRI), are not currently regarded as useful, although they may show abnormalities. Electroencephalography shows no clear abnormalities in stage 0, even if minimal HE is present; in stages I, II and III there are triphasic waves over the frontal lobes that oscillate at 5 Hz, and in stage IV there is slow delta wave activity. However, the changes in EEG are not typical enough to be useful in distinguishing hepatic encephalopathy from other conditions. Once the diagnosis of encephalopathy has been made, efforts are made to exclude underlying causes (such as listed above in "causes"). This requires blood tests (urea and electrolytes, full blood count, liver function tests), usually a chest X-ray, and urinalysis. If there is ascites, a diagnostic paracentesis (removal of a fluid sample with a needle) may be required to identify spontaneous bacterial peritonitis (SBP). Classification West Haven criteria The severity of hepatic encephalopathy is graded with the West Haven Criteria; this is based on the level of impairment of autonomy, changes in consciousness, intellectual function, behavior, and dependence on therapy. Grade 0 - No obvious changes other than a potentially mild decrease in intellectual ability and coordination Grade 1 - Trivial lack of awareness; euphoria or anxiety; shortened attention span; impaired performance of addition or subtraction Grade 2 - Lethargy or apathy; minimal disorientation for time or place; subtle personality change; inappropriate behaviour Grade 3 - Somnolence to semistupor, but responsive to verbal stimuli; confusion; gross disorientation Grade 4 - Coma Types A classification of hepatic encephalopathy was introduced at the World Congress of Gastroenterology 1998 in Vienna. According to this classification, hepatic encephalopathy is subdivided in type A, B and C depending on the underlying cause. Type A (=acute) describes hepatic encephalopathy associated with acute liver failure, typically associated with cerebral oedema Type B (=bypass) is caused by portal-systemic shunting without associated intrinsic liver disease Type C (=cirrhosis) occurs in people with cirrhosis - this type is subdivided in episodic, persistent and minimal encephalopathy The term minimal encephalopathy (MHE) is defined as encephalopathy that does not lead to clinically overt cognitive dysfunction, but can be demonstrated with neuropsychological studies. This is still an important finding, as minimal encephalopathy has been demonstrated to impair quality of life and increase the risk of involvement in road traffic accidents. Minimal HE The diagnosis of minimal hepatic encephalopathy requires neuropsychological testing by definition. Older