The fornix, a part of the Papez circuit, transfers information of episodic memory between the medial temporal lobe and the medial diencephalon. It is difficult to precisely assess the fornix due to its long, thin appearance and its location within the brain. In addition, discrimination of the whole fornix from adjacent neural structure using conventional brain CT or MRI is impossible.
By contrast, diffusion tensor tractography (DTT) has enabled three-dimensional visualization of the fornix, and many studies have reported on fornix injury using DTT. Dr. Sung Ho Jang and co-workers from College of Medicine, Yeungnam University, Republic of Korea using DTT, report on a male patient, 33 years old, who showed selective verbal memory impairment due to left fornical crus injury following intraventricular hemorrhage (IVH). The patient showed impairment in both visual and verbal memory at 1 month after onset; in contrast, at 4 months after onset, the patient showed selective verbal memory impairment with marked improvement of visual memory. One-month DTT for the fornix showed a discontinuation of the left fornical crus, and the discontinued left fornical crus was degenerated toward the fornical body as shown on 4-month DTT. By contrast, the left fornical column was extended to the left medial temporal lobe on both 1- and 4-month DTTs.
These findings indicate that selective verbal memory impairment is mainly due to left fornical crus injury. Therefore, clinicians should focus on how to improve fornix neuroplasticity in these patients and thereby to improve their verbal memory function. The relevant study has been published in the Neural Regeneration Research (Vol. 9, No. 13, 2014).