Structural neuroimaging in patients with panic disorder: findings and limitations of recent studies

Panic disorder, a relatively common anxiety disorder, is often associated to agoraphobia and may be disabling. Its neurobiological underpinnings are unknown, despite the proliferation of models and hypotheses concerning it; investigating its correlates could provide the means for better understanding its pathophysiology. Recent structural neuroimaging techniques may contribute to the identification of possible brain morphological alterations that could be possibly related to the clinical expression of panic disorder.

Through careful major database searches, using terms keen to panic, agoraphobia, structural magnetic neuroimaging and the like, we identified papers published in peer-review journals and reporting data on the brain structure of patients with panic disorder. Included papers were used comparatively to speculate about the nature of reported brain structural alterations.

Anxiety, which is the core feature of the disorder, correlates with the function of the amygdala, which showed a smaller volume in patients, as compared to healthy subjects. Data also showed a volumetric decrease of the anterior cingulate along with increased fractional anisotropy, and increase of some brainstem nuclei, particularly of the rostral pons. Other structures with reported volumetric correlates of panic disorder are the hippocampus and the parahippocampal cortices, the insula, the putamen, and the pituitary gland. Volumetric changes in the anterior cingulate, frontal, orbitofrontal, insular, and temporal cortices have also been described in structural neuroimaging studies. Major methodological limitations are considered in context.

Several data point to the existence of structural neuroanatomical alterations in panic disorder, consisting in significant volumetric reductions or increases in different brain areas. White matter alterations were shown also in the only diffusion tensor imaging study performed to date. Available data do not allow us to conclude about the possible progression of these alterations.