White matter alterations in anorexia nervosa: A systematic review of diffusion tensor imaging studies

Table 3 Main diffusion tensor imaging outcomes and author interpretation

Ref.	AN subtype	Outcomes: DTI measures and areas in AN	Author interpretation
Kazlouski et al[13]	Current AN restricting and purging subtype	FA: Lower in the bilateral fimbria-fornix, fronto-occipital and cingulum fiber tracts	Anxiety is predicted by the fimbria-fornix FA value. Thus, reduced WM integrity could provide a mechanism for heightened anxiety
Frank et al[49]	Current AN restricting and purging subtype	FA: Lower in fornix, cingulum and corpus callosum (corona radiata and forceps mayor)	Abnormal fornix integrity could lead to altered feedback between limbic and higher-order brain structures. The corpus callosum could be implicated in taste processing
Nagahara et al[7]	Current AN, NS subtype	FA: Lower value in the left cerebellum	WM abnormalities in the fornix and the cerebellum may be neural substrates of the pathophysiology of AN. The fornix is one of the important components of the Papez circuit, which links the limbic system with other brain structures. The correlation of WM alteration with physical severity, including BMI and duration of illness may indicate that WM alteration is more relevant with regard to physical severity rather than psychological severity
		MD: Higher value in the fornix
Via et al[53]	Current AN restricting subtype	FA: Lower in the parietal part of the left SLF and the fornix.	The left SLF seem relevant to body image distortion as well as other cognitive processes like the called weak central coherence. The fornix is a key structure involved in the regulation of body-energy balance and processing of reward responses
		MD: Higher in the SLF and the fornix. They also reported significantly increased MD in the fornix, accompanied by decreased FA and increased RD and AD
Frieling et al[5]	Current AN with NS subtype and recovered women from AN	FA (AN and recAN): Lower in the posterior thalamic radiation bilaterally (which includes the of optic radiation) and the left mediodorsal thalamus	The posterior thalamic radiation fibres project to areas involved in the processing of the body image, whose alteration could explain the AN body image distortion. The left mediodorsal thalamic nucleus is connected to regions contributing to impairments in cognitive domains, especially set/shifting ability, executive control, habit learning and reward processing
Yau et al[39]	Recovered women from restricting type AN	FA (recAN): Insignificant alteration	Lower MD was associated with harm avoidance, suggesting a possible underlying trait associated with AN. Localization of disturbances in frontal-parietal and cingulum WM suggests that these pathways, which are important for cognitive control, may be susceptible to core AN pathology. Malnutrition seems to have potentially lasting effects on WM integrity and degree of recovery
		MD: Lower in frontal, parietal and cingulum

AD: Axial diffusivity; AN: Anorexia nervosa patients; HC: Healthy controls; FA: Fractional anisotropy; MD: Mean diffusivity; recAN: Recovered from AN; SLF: Superior longitudinal fasciculus; WM: White matter; RD: Radial diffusivity.