Developing outcome measures of disease activity in pediatric myasthenia.

INTRODUCTION: Pediatric myasthenia encompasses juvenile myasthenia gravis (JMG) and congenital myasthenic syndrome (CMS), which are chronic disorders with fluctuating symptoms amenable to medical therapy. Disease activity and treatment response may be difficult to assess, but, unlike adults, outcome measures have not been developed in children. METHODS: The study was performed in children (0-18 years of age) at the neuromuscular center of a pediatric hospital over a 3-year period. Patients were recruited prospectively as part of their routine clinical care. Demographic data, diagnosis (JMG/CMS), and the following scales were recorded at each visit: Myasthenia Gravis Foundation of America (MGFA) class, Myasthenia Gravis Composite (MGC), and Pediatric Myasthenia-Quality of Life 15 (PM-QOL15). RESULTS: Thirty-three patients (24 JMG, 9 CMS) were included in the study, 22 had two or more visits. We established known-groups validity of the MGC and PM-QOL15 scores as compared with the MGFA class. To establish concurrent validity, we constructed a receiver-operating characteristic curve and calculated threshold values of MGC and PM-QOL15 with optimal sensitivity and specificity for identifying a patient with more severe (MGFA III or higher) disease. Finally, we demonstrated the concordance between the MGC and PM-QOL15 by their statistically significant positive Pearson and Spearman correlations. DISCUSSION: Our study suggests that MGC and PM-QOL15 are important disease outcome measures in pediatric myasthenia that are easy to administer and provide reliable assessment of disease activity in the clinic setting. Further studies are needed to validate their use for pediatric clinical research trials.

Lumbar ligamentum flavum burden: Evaluating the role of ATTRwt amyloid deposition in ligamentum flavum thickness at all lumbar levels.

BACKGROUND: Wild-type transthyretin (ATTRwt) amyloid deposition has been found in the ligamentum flavum (LF) of patients undergoing spinal stenosis surgery. Our group previously reported that ATTRwt amyloid is associated with an increased lumbar ligamentum flavum thickness at symptomatic levels that required surgery. A comprehensive evaluation of LF thickness at asymptomatic levels in addition to symptomatic, treated levels has never been performed in ATTRwt patients. In this study, we compare the total LF thickness of all lumbar levels (lumbar LF burden) in ATTRwt and non-ATTRwt patients. METHODS: We retrospectively identified 177 patients who underwent lumbar spine surgery. Ligamentum flavum thickness of 885 lumbar levels was measured on T2-weighted axial MRI. Amyloid presence was confirmed through Congo red staining of specimens, and subtype of ATTRwt was confirmed using mass-spectrometry and gene sequencing. RESULTS: Of the 177 patients, 30 (16.9%) were found to have ATTRwt in the ligamentum flavum. One hundred and fifty ATTRwt levels and 735 non-ATTRwt levels were measured by four different reviewers, with an intraclass coefficient (ICC) of 0.79. Mean ligamentum flavum thickness was 4.64 (±1.31) mm in the ATTRwt group and 3.99 (±1.45) mm in the non-ATTRwt group (p < 0.001). The lumbar LF burden (sum of ligamentum flavum thickness at all lumbar levels) for ATTRwt patients was 23.22 (±4.48) mm, and for non-ATTRwt patients was 19.96 (±5.49) mm (p = 0.003) CONCLUSION: The lumbar LF burden is greater in patients with ATTRwt amyloid compared to non-ATTRwt patients. This supports prior evidence that ATTRwt amyloid deposition might be associated with increased LF thickness and lumbar stenosis. This potential association requires more research and could be an important finding, as medications have recently become available that can treat patients with ATTRwt amyloid deposition.

Increased thickness of lumbar spine ligamentum flavum in wild-type transthyretin amyloidosis.

BACKGROUND: Wild-type transthyretin (ATTRwt) amyloid deposits have been found in the ligamentum flavum of patients undergoing surgery for spinal stenosis. The relationship between ATTRwt and ligamentum flavum thickness is unclear. We used pre-operative magnetic resonance imaging (MRI) to analyze ligamentum flavum thickness in lumbar spinal stenosis patients with and without ATTRwt amyloid. METHODS: We retrospectively identified 178 patients who underwent lumbar spine surgery. Ligamentum flavum thickness of 253 specimens was measured on T2-weighted axial MRI. Amyloid presence was confirmed through Congo red staining of specimens, and ATTRwt was confirmed using mass-spectrometry and gene sequencing. RESULTS: Twenty four of the 178 patients (13.5%) were found to have ATTRwt in the ligamentum flavum. Forty ATTRwt specimens and 213 non-ATTRwt specimens were measured. Mean ligamentum flavum thickness was 4.92 (±1.27) mm in the ATTRwt group and 4.00 (±1.21) mm in the non-ATTRwt group (p < 0.01). The ligamentum flavum was thickest at L4-L5, with a thickness of 5.15 (±1.27) mm and 4.23 (±1.29) mm in the ATTRwt and non-ATTRwt group, respectively (p = 0.007). There was a significant difference in ligamentum flavum thickness between ATTRwt and non-ATTRwt case for both patients younger than 70 years (p = 0.016) and those older than 70 years (p = 0.004). ATTRwt patients had greater ligamentum flavum thickness by 0.83 mm (95% confidence interval (CI): 0.41-1.25 mm, p < 0.001) when controlled for age and lumbar level. CONCLUSION: Patients with ATTRwt had thicker ligamentum flavum compared to patients without ATTRwt. Further studies are needed to investigate the pathophysiology of ATTRwt in ligamentum flavum thickening.