Prospective neuroimaging study in hereditary spastic paraplegia with thin corpus callosum

Our objective was to estimate the frequency as well as to establish the clinical and neuroimaging profile of hereditary spastic paraplegia with thin corpus callosum (HSP-TCC). HSP-TCC was recognized as a specific clinical subtype of HSP and mapped to chromosome (ch) 15q13-15 in Japanese families. It has been considered rare in western countries. We assessed 45 patients with autosomal recessive HSP from 20 different families in search of clinical and imaging criteria for the diagnosis of HSP-TCC. In addition, HSP-TCC patients underwent further neurological, imaging and genetic evaluation. MRI scans were performed in a 2T scanner and sagittal T1 weighted images used for semiautomated volumetric measurements of corpus callosum, cerebellum, and brain. In seven patients, a 2-year follow-up MRI scan was performed. We genotyped seven microsatellite markers flanking the 15q13-15 candidate region and calculated two-point and multipoint LOD scores (Z). We identified 13 patients from seven unrelated families with HSP-TCC. MRI showed significant corpus callosum, cerebral and cerebellar volumetric reductions (P<0.001, P=0.03, and P=0.01, respectively). In the prospective analysis, we found progressive corpus callosum atrophy (P=0.04). Two-point and multipoint LOD scores were significantly negative for markers genotyped on ch 15q. However, independent pedigree analysis did not yield significant results. HSP-TCC was found in 35% of families with autosomal recessive HSP. MRI volumetry showed cerebral and cerebellar atrophy in association with progressive corpus callosum thinning. Genetic studies did not show evidence for linkage to ch 15q.