"Ears of the Lynx" Sign on Brain MRI in Siblings With Spastic Paraplegia: A Case Report.

Background: Hereditary spastic paraplegia (HSP) is a rare, clinically and genetically heterogenous condition that selectively affects the terminal segment of the descending corticospinal tract of the lumbar spine area, causing lower extremity spastic weakness with or without associated complex neurological symptoms. HSP type 11 is the most common form of autosomal recessive HSP and has unique clinical and neuroimaging features. Methods: We describe the clinical manifestations and imaging features of siblings with childhood-onset autosomal recessive HSP. Genetic testing confirmed compound heterozygous spastic paraplegia gene (SPG) 11 mutations. Results: The older brother developed poor balance and progressive difficulty with walking starting in childhood. He also experienced poor memory and urinary incontinence. He was born preterm at 30 weeks and was developmentally delayed and cognitivly impaired. His examination revealed length-dependent corticospinal tract signs. Magnetic resonance imaging (MRI) showed thinning of the corpus callosum and periventricular signal changes. His earlier cerebral palsy (CP) diagnosis was based on the history and imaging findings, but rcognition of the "ears of the lynx" MRI sign led to the correct diagnosis of HSP 11 with the Invitae HSP gene panel. The younger sister has similar but milder manifestations and, has the same mutation as her brother. Interpretation: Although the manifestations of HSP in children often mimic those of CP, the management and progression of HSP differ substantially.