High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Positional alcohol nystagmus (PAN) is nystagmus (visible jerkiness in eye movement) produced when the head is placed in a sideways position. PAN occurs when the specific gravity of the membrane space of the semicircular canals in the ear differs from the specific gravity of the fluid in the canals because of the presence of alcohol. When a person consumes alcohol, the alcohol is carried by the bloodstream and diffused into the water compartments of the body. Normally, the specific gravity of a canal membrane is the same as the the specific gravity of the surrounding fluid. Because of this, even though the Earth's gravity is a constant force of acceleration, the semicircular canals do not respond to it. Alcohol has a lighter specific gravity than water.