what is the likely diagnosis in this case scenario ,a real one in my practice in my close family friend?

A Microbiologist working in a teaching hospital who is a family friend ,sought advice for repeated spells of giddiness since one year without ear symptoms.Symptoms were severe enough to suspend the theory class and walk out to her chamber and recover.Physical findings when symptomatic not known.OGTT results 0 hr 98,30min.176,60min.188,90min 163,120min 138,180min 79,240min 51. what is this condition?

What is its significance?How is it treated?