Badr al-Din al-Himsi better known as Ibn al-Isyani (circa 834 Hijri) was initially not intelligent. It so happened that he fell from a high place causing hima sever head injury. He received treatment and recovered and became a Hafiz and excelled in the rational sciences as well as others.
Inba al-Ghamar of Hafiz Ibn Hajar 3/468.