Dr. Lachman graduated from Antioch College with a BA in Philosophy in 1963. After attending the University of Pennsylvania, School of Medicine from 1963 to 1967, he interned at Pennsylvania Hospital. He was selected for the US Public Health Service and was stationed for two years on the Turtle Mountain Indian Reservation in North Dakota. He was a neurology resident at the Cleveland Metropolitan General Hospital from 1970 until 1973 and a fellow in clinical neurophysiology at the Mass General Hospital from 1973 until 1975.
In 1975, he joined a private practice in the Philadelphia area. He joined the neurology faculty at Hahnemann University from 1978 to 1982, when he returned to solo private practice at Lankenau Hospital. In December 2006 he became a full-time faculty member in the Department of Neurology at Temple University School of Medicine.