Definition
Scales and terms to classify the levels of consciousness differ, but in general, reduction in response to stimuli indicates an altered level of consciousness:

Altered level of consciousness is sometimes described as altered sensorium. Glasgow Coma Scale
The most commonly used tool for measuring LOC objectively is the Glasgow Coma Scale (GCS). It has come into almost universal use for assessing people with brain injury, or an altered level of consciousness. Verbal, motor, and eye-opening responses to stimuli are measured, scored, and added into a final score on a scale of 3–15, with a lower score being a more decreased level of consciousness. Others
The AVPU scale is another means of measuring LOC: people are assessed to determine whether they are alert, responsive to verbal stimuli, responsive to painful stimuli, or unresponsive. To determine responsiveness to voice, a caregiver speaks to, or, failing that, yells at the person. Responsiveness to pain is determined with a mild painful stimulus such as a pinch; moaning or withdrawal from the stimulus is considered a response to pain. The ACDU scale, like AVPU, is easier to use than the GCS and produces similarly accurate results. Using ACDU, a patient is assessed for alertness, confusion, drowsiness, and unresponsiveness.The Grady Coma Scale classes people on a scale of I to V along a scale of confusion, stupor, deep stupor, abnormal posturing, and coma. Pathophysiology
Although the neural science behind alertness, wakefulness, and arousal are not fully known, the reticular formation is known to play a role in these.
Necrolytic migratory erythema is a red, blistering rash that spreads across the skin. It particularly affects the skin around the mouth and distal extremities; but may also be found on the lower abdomen, buttocks, perineum, and groin. It is strongly associated with glucagonoma, a glucagon-producing tumor of the pancreas, but is also seen in a number of other conditions including liver disease and intestinal malabsorption. Signs and symptoms
Clinical features
NME features a characteristic skin eruption of red patches with irregular borders, intact and ruptured vesicles, and crust formation. It commonly affects the limbs and skin surrounding the lips, although less commonly the abdomen, perineum, thighs, buttocks, and groin may be affected. Frequently these areas may be left dry or fissured as a result. All stages of lesion development may be observed synchronously. The initial eruption may be exacerbated by pressure or trauma to the affected areas. Associated conditions
William Becker first described an association between NME and glucagonoma in 1942 and since then, NME has been described in as many as 70% of persons with a glucagonoma. NME is considered part of the glucagonoma syndrome, which is associated with hyperglucagonemia, diabetes mellitus, and hypoaminoacidemia. When NME is identified in the absence of a glucagonoma, it may be considered "pseudoglucagonoma syndrome". Less common than NME with glucagonoma, pseudoglucagonoma syndrome may occur in a number of systemic disorders:
Celiac disease
Ulcerative colitis
Crohns disease
Hepatic cirrhosis
Hepatocellular carcinoma
Lung cancer, including small cell lung cancer
Tumors that secrete insulin- or insulin-like growth factor 2
Duodenal cancer

Cause
The cause of NME is unknown, although various mechanisms have been suggested.