Jack'sMom are you talking about IQ points or percentiles? A 50 percentile point spread is not as dramatic as a 50 IQ point spread. My DD has a 43 IQ point spread between WMI and VCI, which is an 83% gap!
I am guessing MelMichigan that you have to be talking about a WMI or PSI of 88 and a VCI or PRI of 148? That is, in my understanding, an uncommon degree of scatter and can be indicative of a potential learning delay. But it could also be perfectionism and/or motor skill issues at work. Comparison with the achievement testing will no doubt help enormously.
In my DDs case we have CAPD, and almost certainly dyslexia and inattentive ADHD at work.