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

BACKGROUND AND PURPOSE: 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. METHODS: We studied with MRI four patients from three families with HSP-TCC who had identified causal mutations in the SPG11 gene. RESULTS: 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. CONCLUSION: 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.