Hepatic encephalopathy, or HE, is a decline in brain function that occurs as a result of severe liver disease. When the liver is compromised, toxins it normally filters from the blood can accumulate. These circulating substances, particularly ammonia, can then travel to the brain and disrupt normal neurological processes. HE exists on a spectrum, and its effects can range from subtle cognitive changes that are difficult to detect to a severe loss of brain function.
Initial Clinical Assessment
A diagnosis of hepatic encephalopathy begins with a thorough clinical evaluation, which includes a detailed medical history and a physical examination. The process is often initiated when a person with known liver disease begins to show changes in their mental state. Doctors will inquire about the onset of symptoms, recent illnesses like infections, medication use, and any history of related health issues to identify potential triggers.
Input from family members or caregivers is frequently sought, as these individuals are often the first to notice subtle shifts in a patient’s personality, mood, or behavior that the patient may not recognize. Changes in sleep patterns, such as sleeping during the day and being awake at night, are also common early indicators.
A part of the physical exam involves testing for a specific tremor called asterixis, often referred to as the “liver flap.” To elicit this sign, the doctor asks the patient to extend their arms and bend their wrists backward as if stopping traffic. A person with overt HE will be unable to hold this position steadily, resulting in a characteristic jerky, flapping motion of the hands.
Evaluating Mental and Neurological Function
To quantify the degree of cognitive and neurological impairment, clinicians use structured assessment tools. The most common system for grading the severity of overt HE is the West Haven Criteria. This scale classifies the condition into five grades:
- Grade 0: No detectable changes.
- Grade 1: Mild changes like a shortened attention span or altered mood.
- Grade 2: Disorientation and lethargy.
- Grade 3: Significant confusion and drowsiness, though the person can still be roused.
- Grade 4: A comatose state.
Doctors may use simple bedside tests to gauge a patient’s cognitive function. One common example is the Number Connection Test, where the patient is asked to draw lines connecting numbered circles in sequential order. Another test involves asking the patient to name as many animals as they can in one minute, which assesses verbal fluency and processing speed.
For a more detailed analysis of brain function, an electroencephalogram (EEG) may be ordered. An EEG measures the electrical activity in the brain through electrodes placed on the scalp. In the context of HE, the test does not show a specific diagnostic pattern but often reveals a general slowing of brain waves, which can support the diagnosis.
Laboratory and Imaging Tests
While a diagnosis is primarily based on clinical findings, laboratory tests are performed to support the assessment and to rule out other conditions. Blood tests are ordered to check liver function, electrolyte levels, and blood glucose, as imbalances can cause symptoms similar to HE. A test also measures the level of ammonia in the blood.
Blood ammonia levels do not always align with the severity of the symptoms. A person can have very high ammonia levels with mild symptoms, or more severe symptoms with only moderately elevated levels. Because of this poor correlation, an ammonia test is not used by itself to diagnose or grade the condition but is one piece of the overall diagnostic puzzle. A normal ammonia level might prompt doctors to reconsider the diagnosis.
Brain imaging, such as a computed tomography (CT) scan or magnetic resonance imaging (MRI), is another part of the diagnostic process. These scans are not used to visualize HE itself, as the condition does not cause visible structural changes. Instead, their main purpose is to exclude other potential causes for the neurological symptoms, such as a stroke, brain tumor, or bleeding within the skull.
Diagnosing Minimal Hepatic Encephalopathy
The mildest form of the condition is known as minimal hepatic encephalopathy (MHE). In MHE, a person shows no recognizable symptoms during a standard clinical examination and may not notice any issues themselves. Despite the lack of overt signs, individuals with MHE have measurable cognitive deficits that can affect their ability to perform complex tasks, such as driving or managing finances. The prevalence of MHE among people with cirrhosis is high.
Because the changes are so subtle, diagnosing MHE requires more specialized and sensitive tests than those used for overt HE. Standard bedside exams and the West Haven Criteria are not sufficient to detect these minor deficits.
Diagnosis relies on a battery of detailed psychometric tests that assess functions like attention, processing speed, and fine motor skills. The primary tool for diagnosing MHE is a collection of paper-and-pencil tests known as the Psychometric Hepatic Encephalopathy Score (PHES), which includes tasks like the Digit Symbol Test and the Number Connection Test.