Deficits in the left inferior longitudinal fasciculus results in impairments in object naming.

The functional characteristics of the left inferior longitudinal fasciculus (ILF) remain unclear. The present study describes a case of a right-handed 74-year-old woman with a brain tumor who showed marked deterioration in object naming ability after invasion of the tumor into the medial region of the left posterior (middle and inferior) temporal lobe just beside the atrium of the lateral ventricle. Diffusion tensor imaging showed possible interruption of the left ILF after invasion of tumor at this site. By contrast, the left superior longitudinal fasciculus (SLF) remained intact after invasion of tumor, and the inferior fronto-occipital fasciculus (IFOF) was already disrupted prior to tumor invasion. These observations indicate that intact ILF function may be required for object naming ability.