Dysmetria
This is a condition I suffer from and was aware of it's existence, except that until I was researching an associated condition I had no idea that it had a name. I referred to it as a lack of spatial awareness. Sometimes described as the inability to judge distance and scale, a description I find misleading as such a description implies ocular problems rather than positional judgement.
The word dysmetria is Greek in origin and means 'difficult to measure'.
How often when you see your GP, neurologist or MS nurse do they raise a finger in front of you and ask you to touch it with your forefinger and then touch your nose, several times. They are testing for dysmetria, your ability to sense both the position of your target and your forefinger. As far as I can ascertain, the full name of the condition is saccadic dysmetria.
In dysmetria, damage to the proprioceptive nerves prevents your brain receiving positional feedback so that you cannot accurately judge the position of your forefinger. The cerebellum is the area of the brain responsible for this hand-eye coordination. While there may be damage in the cerebellum it is more likely lesions in the peripheral sensory nerves are depriving the brain of the necessary feedback.
This lack of positional precision is often referred to as overshooting or undershooting the target. I have many times knocked over coffee cups when I attempt to pick them up as they are not where I thought they were. Fortunately, I have yet to scald myself.
- hypometria - undershooting the target
- hypermetria - overshooting the target
Treatments
- Isoniazid
- Clonazepam
- Cannabis