Marsden Ball: The typical Marsden ball looks like a plastic baseball with smallish numbers and/or letters printed over it’s surface. It has an attachment point for a string, and a good length of string is attached to it, perhaps 20 feet. The string is passed through an eyelet screw which is screwed into the ceiling at least 6 feet from the nearest wall – this allows the ball to swing freely in any direction and to vary the height of the ball from the floor.
Marsden balls are useful in training VSA, and to some extent VSP (such as figure ground and spatial awareness). The typical activity involves the patient standing, sitting, or lying down and, with head steady, maintaining fixation on the ball as it swings about. There are many variations on this theme, and the Marsden Ball will be used frequently for VSA and VSP exercises.
Make Your Own Marsden Ball: You can begin with either a tennis ball, or a similarly sized plastic ball, or even an actual baseball. The ball itself should be relatively featureless. Find a couple of small eyelet screws (1/2″ – 3/4″ long or so). Screw one into the ball (you might have to ‘start’ the hole with a sharp nail, screwdriver, or drill). Screw the other into a spot in the ceiling in a room where it would be appropriate to do therapy: The space should be relatively uncluttered with a fair bit of free space on the floor below the screw in the ceiling. Tie one end of the string to the ball, and pass the other end through the eyelet screw in the ceiling. It is sometimes practical to screw a third eyelet screw into the nearest wall, and to use that screw as an attachment point for the slack end of the string; this allows you to lower the ball to just the right height and then tie it down at that level.
Targets can be drawn on the ball using a marker. Ideally, you should use a washable marker and a ball that is smooth and allows for the ink to be washed off (like a fake white plastic baseball). You can also use a computer and printer to print off letters in the alphabet and numbers. Start with targets that are around 24 points in size. Begin with larger and fewer targets; as skill advances, targets can become smaller and more numerous (depending on the activity.) Cut the targets out and affix them randomly (right side up) across the ball’s surface. Some exercises will only require a few targets. Frequently, simple fat dots will work.
You can also ask your clinic about purchasing a ready-made Marsden Ball, or see get one online at the www.oepf.org store.