Lamar Odom Returns to L.A. For Specialized Treatment

8:15 PM PT -- Lamar and Khloe left Vegas for L.A. at 5:30 PM via helicopter.

Lamar Odom is on his way back to L.A. for more specialized treatment ... TMZ has confirmed.

Odom is flying back to L.A., accompanied by Khloe Kardashian. As we reported, Khloe has vowed to be by Lamar's side throughout his rehab, which will take months.

Our sources say Lamar has numerous unresolved medical issues. We believe he will be admitted to an L.A. area medical facility for further treatment.

Odom is expected to survive, but doctors have cautioned his family there will be some permanent damage, though the extent is unclear.