From: Rabbi Moshe Sofer
To: Rabbi Shmuel
A husband who concealed his epilepsy before marriage cannot be compelled to give a get, because the halachic authorities dispute whether epilepsy is grounds for compulsion, and coercion in a disputed case would render the get certainly invalid. However, since the husband deceived his wife, the wife's father need not return any of the husband's money until he agrees to divorce voluntarily, providing financial leverage to obtain a willing get without risking an invalid coerced one.
Source: Shu"t Chasam Sofer EH I §116