Weinshenker, Brian G.

Objective: To report progressive motor impairment from a critically located central nervous system (CNS) demyelinating lesion in patients with restricted magnetic resonance imaging (MRI)-lesion burden. Methods: We identified 38 patients with progressive upper motor-neuron impairment for >1 year, 2–5 MRI CNS-demyelinating lesions, with one seemingly anatomically responsible for progressive motor impairment. Patients with any alternative etiology for progressive motor impairment were excluded. A neuroradiologist blinded to clinical evaluation reviewed multiple brain and spinal-cord MRI, selecting a candidate critically located demyelinating lesion. Lesion characteristics were determined and subsequently compared with clinical course. Results: Median onset age was 47.5 years (24–64); 23 (61%) women. Median follow-up was 94 months (18–442); median Expanded Disability Status Scale Score (EDSS) at last follow-up was 4.5 (2–10). Clinical presentations were progressive: hemiparesis/monoparesis 31; quadriparesis 5; and paraparesis 2; 27 patients had progression from onset; 11 progression post-relapse. Total MRI lesions were 2 ( n = 8), 3 ( n = 12), 4 ( n = 12), and 5 ( n = 6). Critical lesions were located on corticospinal tracts, chronically atrophic in 26/38 (68%) and involved cervical spinal cord in 27, cervicomedullary/brainstem region in 6, thoracic spinal cord in 4, and subcortical white matter in 1. Conclusion: Progressive motor impairment may ascribe to a critically located CNS-demyelinating lesion in patients with highly restricted MRI burden. Motor progression from a specific demyelinating lesion has implications for understanding multiple sclerosis (MS) progression.

SummaryGermline mutations in patients with hemophilia B generally have arisen within the past 150 years. Evidence suggests that these germline mutations generally result from endogenous processes. However, a unique pattern would be expected if a population were exposed to a physiologically important germline mutagen since mutagens generally produce characteristic patterns, or “fingerprints”, of mutation. To determine the pattern of mutation in Mexican Hispanics, the regions of likely functional significance in the factor IX gene were screened by di-deoxy fingerprinting (ddF) in 31 families with hemophilia B. Mutations were found in 30 of these families. Haplotype analysis was performed on individuals with identical mutations to help distinguish independent, recurrent mutations from founder effects. Analysis of these 30 mutations, along with 7 mutations reported previously in Mexican Hispanic families, reveals a pattern of independent mutation that is similar to the pattern of mutation observed in 127 U. S. Caucasian families (p = 0.89). These results may reflect either an underlying pattern of germline mutation due to endogenous processes or the presence of an ubiquitous mutagen. Further analyses of the recurrent mutations revealed that two mutations, T296M and R248Q, accounted for 19% of the mutations found in the Mexicans. Haplotype data suggest that the multiple occurrences of T296M and R248Q are associated with founder effects and that screening for these mutations may allow rapid mutation detection and carrier diagnosis in a significant minority of Mexican families with hemophilia B. These two mutations also are associated with founder effects in the U. S. Caucasian population. However, the haplotypes are different in these two populations, indicating independent origins. The occurrence of identical founder mutations in distinct populations provides evidence for the previous hypothesis that the number of different mutations giving rise to mild or borderline mild/moderate hemophilia B is small compared to deleterious mutations causing more severe disease.