Do white matter hyperintensities cause short term memory loss its the only issue i have ms ruled out diagnosis ended up being adhd can spots alone cause the memory issues spots were on right parietal frontal lobe, memory issues make school difficult?

More long term and dementia. Rare at your age unless abusing drugs.

T2 intracranial white matter lesions are usually nonspecific and markers of prior smoking, head injuries, migraine, microvascular angiopathy, MS, and many other causes. In absence of a specific disease correlation, these "spots" would usually be essentially asymptomatic. Discuss with your doctor and radiologist how this relates to you.