Neurochemical correlates of behavioral treatment of pediatric trichotillomania.

BACKGROUND

Trichotillomania (TTM) is a chronic and impairing psychiatric disorder with suspected dysfunctional cortico-striato-thalamo-cortical (CSTC) circuit activity reflecting excitatory/inhibitory signaling imbalance. TTM neurochemistry is understudied, with no prior research using magnetic resonance spectroscopy (MRS). This pilot investigation examined associations between TTM diagnosis, symptom severity, and response to behavioral treatment with MRS neurometabolites glutamate (Glu) and γ-aminobutyric acid (GABA) in CSTC structures.

METHODS

Proton echo-planar spectroscopic imaging (PEPSI) MRS was acquired from bilateral pregenual anterior cingulate cortex (pACC), caudate, putamen, globus pallidus, thalamus, and proximal white matter in 10 unmedicated girls with TTM, ages 9-17 years, before and after treatment, and from 13 age- and sex-matched healthy controls.

RESULTS

Nine of 10 TTM patients were treatment responders. Pretreatment mean Glu and GABA did not differ significantly between participants and controls. Pretreatment TTM symptoms were correlated with Glu in (left + right) pACC (r = 0.88, p = 0.02) and thalamus (r = 0.82, p = 0.012), and were negatively correlated with pACC GABA (r = -0.84, p = 0.034). Mean GABA in putamen increased 69% (baseline to post-treatment) (p = 0.027). Higher pretreatment Glu in caudate, putamen, globus pallidus, and thalamus predicted greater symptom decreases with treatment (all r < -0.6, p < 0.05); higher caudate GABA predicted less treatment-related symptom decline (r = 0.86, p = 0.014).

LIMITATIONS: Small sample, GABA quantified with spectral fitting rather than editing.

CONCLUSION

Consistent with other neuroimaging, MRS reveals discrete CSTC chemical changes with effective behavior therapy, and possibly with TTM etiology. TTM symptoms relate to excess excitatory versus inhibitory signaling in pACC and thalamus; symptom improvement may reflect reduced excitatory drive of the CSTC direct-pathway activity.