Severe Apathy Due to Injury of Prefronto-caudate Tract

The caudate nucleus, which is vulnerable to hypoxic-ischemic brain injury (HI-BI), is important to cognitive function because it is connected to the prefrontal cortex. Using diffusion tensor tractography (DTT), no study on injury of the prefronto-caudate tract in a patient with HI-BI has been reported so far. Here, we report a patient with severe apathy who showed injury of the prefronto-caudate tract following HI-BI, which was demonstrated by DTT. A 38-year-old female patient suffered HI-BI induced by carbon monoxide poisoning following attempted suicide for a period of approximately four hours. From the onset, the patient showed severe apathy (7 months after onset-the Apathy Scale score was 24 [full score: 42]). Brain MR images taken at seven months after onset showed no abnormality. On 7-month DTT, the neural connectivity of the caudate nucleus to the medial prefrontal cortex (Brodmann area: 10 and 12) and orbitofrontal cortex (Brodmann area: 11 and 13) was decreased in both hemispheres. Using DTT, injury of the prefronto-caudate tract was demonstrated in a patient who showed severe apathy following HI-BI. We believe that injury of the prefronto-caudate tract might be a pathogenetic mechanism of apathy in patients with HI-BI.