TREM2 and Parkinson disease: In the CNS, TREM2 expression is increased in the context of traumatic brain injury [98, 99], stroke [160, 193], spinal nerve transection [194], ALS [64], PD [66], prion disease [155, 195], models of demyelination [151, 159, 196–198] and following beta-amyloid (Aβ) vaccination [199].