Forceps Minor Region Signal Abnormality “Ears of the Lynx”: An Early MRI Finding in Spastic Paraparesis with Thin Corpus Callosum and Mutations in the Spatacsin Gene (SPG11) on Chromosome 15

Abstract

A thin corpus callosum on magnetic resonance imaging (MRI) characterizes a type of autosomal recessive disorder with progressive spastic paraparesis and cognitive impairment. Known as Hereditary Spastic Paraparesis with Thin Corpus Callosum (HSP-TCC), it has been associated with mutations of the SPG11 gene. No other specific MRI findings have been reported. We studied with MRI four patients from three families with HSP-TCC who had identified causal mutations in the SPG11 gene. In all individuals studied the region of the forceps minor of the corpus callosum, corresponding to the genu fibers, appeared bright on T2-weighted and dark on T1-weighted images. On axial sections, the frontal horn region bore a remarkable resemblance to the ears of a lynx, with the areas of abnormal signal reminiscent of the tufts of hair crowning the tips of the ears of this animal. Less specific findings included a box-shape appearance of the calloso-caudate angle and diffusely increased signal in the hemispheric white matter. Abnormal MRI signal in the region of the forceps minor of the corpus callosum is a characteristic early imaging finding of HSP-TCC with SPG11 mutations.