Activated brain microglia are thought to play a major role in cortical gray matter demyelination in multiple sclerosis. PK11195, a positron emission tomography (PET) ligand, can be used to quantify microglial activation in vivo. Using PK11195 binding and PET, this study evaluated microglial activation in the cortical grey matter of patients with relapsing-remitting multiple sclerosis and secondary progressive multiple sclerosis versus healthy controls. Disability was assessed with the Expanded Disability Status Scale and Multiple Sclerosis Impact Scale.

Patients with multiple sclerosis showed increased cortical grey matter PK11195 binding relative to controls, which was multifocal and highest in the postcentral, middle frontal, anterior orbital, fusiform, and parahippocampal gyri. Total cortical grey matter PK11195 binding correlated with Expanded Disability Status Scale scores, with a stronger correlation for the subgroup of patients with secondary progressive multiple sclerosis. Higher Expanded Disability Status Scale scores correlated with higher levels of grey matter PK11195 binding in the postcentral gyrus for patients with relapsing-remitting multiple sclerosis and in precentral gyrus for those with secondary progressive multiple sclerosis.

The authors concluded that microglial activation in cortical grey matter of patients with multiple sclerosis can be assessed in vivo using PET. There appears to be a relationship between microglial activation (as measured by PK11195) and clinical disability in this disorder.

Politis M, Giannetti P, Su P, Turkheimer F, Keihaninejad S, Wu K, Waldman A, Malik O, Matthews PM, Reynolds R, Nicholas R, Piccini P: Increased PK11195 PET binding in the cortex of patients with MS correlates with disability. Neurology [July 3, 2012; Epub ahead of print].


Study of brain microglial activation using PK11195 binding and positron emission tomography is an increasingly popular technique and has been used in other disorders such as Alzheimers. See: Schuitemaker A, Kropholler MA, Boellaard R, van der Flier WM, Kloet RW, van der Doef TF, Knol DL, Windhorst AD, Luurtsema G, Barkhof F, Jonker C, Lammertsma AA, Scheltens P, van Berckel BN: Microglial activation in Alzheimer’s disease: an (R)-[(11)C]PK11195 positron emission tomography study. Neurobiol Aging [July 25, 2012, Epub ahead of print].

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