Q: Which condition is abbreviated as "SILENT"?

Answer:  "Syndrome of Irreversible Lithium-Effectuated Neurotoxicity" (SILENT)

Neurotoxicity from Lithium acute or chronic overdose is irreversible and causes  cerebellar dysfunction.


Reference:

Adityanjee; Munshi, Thampy (2005). "The syndrome of irreversible lithium-effectuated neurotoxicity.". Clinical Neuropharmacology 28 (1): 38–49.