Freezing (sometimes called motor block) is a sudden, brief inability
to start movement or to continue rhythmic, repeated movements, such as
finger-tapping, writing, or walking. Freezing most often affects walking, but
it also can affect speech, writing, and the person's ability to open and close
his or her eyes. It tends to develop later in the course of the disease.
Freezing can be very disabling when it affects the way a person
walks, causing the person to stop as though his or her feet suddenly have
become glued to the floor. It can result in falls that cause significant
injury, such as hip fracture. Freezing may occur at an open doorway (most
common), at a line on the floor, or in crowds; it may be more likely to occur
if the person is anxious or under stress.
Different strategies for breaking the motor block and getting the
person moving again include having the person look at a target on the floor;
step in a deliberate, precise way (like a marching step); or step over an
object placed on the floor (such as a cane). Specially trained dogs, special
canes, and, more recently, laser pointers also have been used with
success.
Apomorphine (Apokyn) is a fast-acting dopamine agonist that seems to
be helpful in treating freezing associated with Parkinson's disease.
Apomorphine can be injected under the skin when muscles become "frozen." Apokyn
can be taken with an antinausea drug to prevent side effects of severe nausea
and vomiting.
Changing a person's levodopa dosage may improve freezing, but this
does not work in all cases.