Dorsolateral Cervical Cord T2 Hyperintensity in KIF1C-Related Disease (Spastic Paraplegia 58): Two Long-Duration Cases.

Pathogenic variants in KIF1C cause Spastic Paraplegia 58 (SPG58), typically presenting with cerebellar ataxia and spastic paraparesis. We report two unrelated patients with spastic paraparesis, cerebellar ataxia, and tremor. Whole-exome sequence analysis identified novel homozygous variants in the motor domain of KIF1C (NM_006612.6): c.921G>A (p.Trp307Ter) and c.607C>T (p.Arg203Trp). In addition to the canonical brain MRI showing leukoencephalopathy with posterior dominance and hyperintensity along the corticospinal tracts, both patients showed symmetric T2 hyperintensity confined to the lateral and dorsal columns of the cervical cord. Given the long disease durations (22 and 51 years), these findings may represent late-emerging or previously overlooked spinal cord involvement and broaden the neuroradiological spectrum of SPG58.