A 21-year-old male presented with slowly progressive gait and balance disorders since he was 17 years of age. His younger brother presented with similar symptoms. The neurologic examination revealed spastic paraparesis, generalized hyperreflexia, bilateral plantar extensor reflex and a moderate cognitive disorder. The test for HTLV was non-reactive. He had sensitive motor axonal polyneuropathy. Next generation sequencing performed on the patient and his brother found mutations in the SPG11 gene. Brain MRI showed the lynx ears sign and corpus callosum atrophy. This sign correlates with axonal degeneration of the corpus callosum and it is highly specific for hereditary type 11 and 15 spastic paraparesis. The sign (yellow arrows) is hypointense in T1 (1a) and hyperintense in FLAIR (1b). Image 2 shows atrophy of the corpus callosum (green arrow) from the rostrum, knee and medial segment whic...