What is the difference between "misapprehension" and "apprehension"?

Apprehension is not usually used as the opposite of misapprehension.

Misapprehension is another word for misunderstanding - "A mistaken belief about or interpretation of something".

Apprehension can mean "understanding", but is usually used to refer to a feeling of fear or misgiving about a future event.

"Misapprehension" only negates one meaning of "apprehension":

misapprehension — a mistaken belief about or interpretation of something

apprehension — understanding; grasp

The other meanings of apprehension are generally not relevant to the meaning of misapprehension.

Usage examples from the same dictionary I grabbed the definitions:

the pure apprehension of the work of art

she must have been laboring under the misapprehension that you are nice