Is the hadith of Ya'la ibn Murra al-Thaqafi concerning the epileptic boy authentic, and what is its explanation?

The hadith of Ya'la ibn Murrah al-Thaqafi regarding the possessed child is authentic due to its various chains of narration, and it was authenticated by Al-Albani. Al-Hakim narrated that a woman came to the Prophet, peace and blessings be upon him, with her son who had been afflicted with "lamam" (a touch from Satan) for seven years. The Prophet, peace and blessings be upon him, spat into his mouth and said, "Come out, enemy of Allah, I am the Messenger of Allah." The Prophet, peace and blessings be upon him, spat hoping for the blessing of his saliva, as was established in his ruqyah for the sick. The hadith indicates the reality of epilepsy and that it is from Satan, and the permissibility of seeking ruqyah.