From the YWN archives:
In one of his shiurim, HaGaon HaRav Yitzchak Zilberstein explained that his father-in-law, Maran HaGaon Rav Yosef Sholom Elyashiv Shlita would on erev Shavuos visit the sick, remembering that we learn that prior to giving Bnei Yisrael the Torah on Shavuos, Hashem healed all the sick, including the blind, deaf and mute – all were healed.
Rav Elyashiv explained to a sick man that every year, on Shavuos, this power is renewed. This is a time when one may call upon Hashem and asked to be healed; even for such illnesses that we generally feel there is no cure.
It was asked at what time on yomtov may one ask for a refuah. Rav Elyashiv pondered for a moment and stated the time is when we read the Aseres HaDibros in the torah reading.
(Yechiel Spira – YWN Israel)