Question  Is translocator protein distribution volume, a marker of the microglial component of neuroinflammation, elevated in the cortico-striato-thalamo-cortical (CSTC) circuit of obsessive-compulsive disorder (OCD)?

Findings  In this case-control study, translocator protein distribution volume was significantly elevated in the CSTC of participants with OCD compared with healthy control individuals. The Yale-Brown Obsessive Compulsive Scale measure of distress associated with preventing compulsive behaviors was positively correlated with translocator protein distribution volume in the orbitofrontal cortex.

Meaning  The presence of neuroinflammation in the CSTC of OCD argues for extending investigations of serum autoantibodies to the entire CSTC and that immunomodulatory therapies should be investigated in adult OCD.

Importance  For a small percentage of obsessive-compulsive disorder (OCD) cases exhibiting additional neuropsychiatric symptoms, it was proposed that neuroinflammation occurs in the basal ganglia as an autoimmune response to infections. However, it is possible that elevated neuroinflammation, inducible by a diverse range of mechanisms, is important throughout the cortico-striato-thalamo-cortical circuit of OCD. Identifying brain inflammation is possible with the recent advance in positron emission tomography (PET) radioligands that bind to the translocator protein (TSPO). Translocator protein density increases when microglia are activated during neuroinflammation and the TSPO distribution volume (V_T) is an index of TSPO density.

Objective  To determine whether TSPO V_T is elevated in the dorsal caudate, orbitofrontal cortex, thalamus, ventral striatum, dorsal putamen, and anterior cingulate cortex in OCD.

Design, Setting, and Participants  This case-control study was conducted at a tertiary care psychiatric hospital from May 1, 2010, to November 30, 2016. Participants with OCD (n = 20) and age-matched healthy control individuals (n = 20) underwent a fluorine F 18–labeled N-(2-(2-fluoroethoxy)benzyl)-N-(4-phenoxypyridin-3-yl)acetamide PET scan. It is a high-quality second-generation TSPO-binding PET radiotracer. All participants were drug and medication free, nonsmoking, and otherwise healthy.

Main Outcomes and Measures  The TSPO V_T was measured in the dorsal caudate, orbitofrontal cortex, thalamus, ventral striatum, dorsal putamen, and anterior cingulate cortex. Compulsions were assessed with the Yale-Brown Obsessive Compulsive Scale.

Results  In the OCD and healthy groups, the mean (SD) ages were 27.4 (7.1) years and 27.6 (6.6) years, respectively, and 11 (55%) and 8 (40%) were women, respectively. In OCD, TSPO V_T was significantly elevated in these brain regions (mean, 32%; range, 31%-36% except anterior cingulate cortex, 24%; analysis of variance, effect of diagnosis: P < .001 to P = .004). Slightly lower elevations in TSPO V_T (22%-29%) were present in other gray matter regions. The Yale-Brown Obsessive Compulsive Scale measure of distress associated with preventing compulsive behaviors significantly correlated with TSPO V_Tin the orbitofrontal cortex (uncorrected Pearson correlation r = 0.62; P = .005).

Conclusions and Relevance  To our knowledge, this is the first study demonstrating inflammation within the neurocircuitry of OCD. The regional distribution of elevated TSPO V_T argues that the autoimmune/neuroinflammatory theories of OCD should extend beyond the basal ganglia to include the cortico-striato-thalamo-cortical circuit. Immunomodulatory therapies should be investigated in adult OCD, rather than solely childhood OCD, particularly in cases with prominent distress when preventing compulsions.

ACCESO AL FULL TEXT: jamapsychiatry_Attwells_2017_oi_170038