In some rabbits,

Head Tilt

In some rabbits, they contract parasites called Encephalitozoon Cuniculi, or also called E. Cuniculi for short,  IF your rabbit has a hard time eating, drinking, sitting, etc. visit your rabbit savvy veterinarians IMMEDIATELY! Unfortunately, this has a permanent effect on the rabbits and even after the antibiotics and the medicine, most likely, they will be having a slight head tilt. 

Once a rabbit has the disease it passes infectious spores in its urine. Transmission to another rabbit occurs by eating these spores in urine contaminated food and water. The unborn kits may also be infected across the placenta during pregnancy. Inhalation of spores has been shown to cause infection, although these last two routes are thought to occur less frequently (Cox and others, 1979). Once the parasite has entered the rabbit's body it is carried in the blood circulation to target organs such as the liver, kidney and central nervous system (brain and spinal cord). It then infects the cells of these organs by ejecting the polar filament, which injects the spore into the cell. Once inside the host cell the parasite multiples causing the cell to enlarge and eventually rupture, which releases spores. These in turn infect nearby cells and pass into the blood to other organs. The life cycle lasts three to five weeks. Rupture of the host cell causes inflammation, primarily in the liver, kidney, brain and spinal cord and results in clinical signs in the rabbit.