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

Previous surgery for lumbar spinal stenosis and association with amyloidosis and heart failure - A Danish nationwide study

INTRODUCTION

Cardiac Amyloidosis (CA) is characterised by amyloid fibril deposits causing heart failure (HF). Lumbar spinal stenosis (LSS) is recognised as a potential red flag for CA, but the association remains underexplored in large-scale studies.

METHODS

This nationwide registry-based cohort study in Denmark included subjects ≥60 years with a history of LSS surgery. LSS patients were matched 1:1 with controls by age, sex, ischaemic heart disease, chronic obstructive lung disease, chronic kidney disease, diabetes, and atrial fibrillation.

RESULTS

A total of 44,548 LSS surgery patients and matched controls were included (median age 71.5 years, 56.2% women). The cumulative incidence of amyloidosis after 10 years was higher in the LSS group (0.16% vs. 0.08%, HR 2.29 [95% CI 1.46-3.60]) after adjustment for malignancy, hypertension, and liver disease. The cumulative incidence of HF after 10 years was 10.1% in LSS patients compared with 7.5% in controls (HR 1.28 [95% CI 1.22-1.35], p < 0.0001).

CONCLUSIONS

In this nationwide cohort study, LSS surgery was associated with a significantly higher risk of amyloidosis and HF. Prospective studies are warranted to explore the association further.

Transthyretin amyloidosis in patients with spinal stenosis who underwent spinal surgery: a systematic review and meta-analysis

Background

Accumulation of transthyretin amyloids (ATTR) is detected in ligamentum flavum in about 1/3 of patients underwent surgery for spinal stenosis. However, the significance of this finding is not known. The aim of this systematic review and meta-analysis is to analyze the incidence and importance of ATTR in patients with spinal stenosis who underwent spinal surgery.

Methods

The primary outcome measure was incidence of ATTR in patients with spinal stenosis. English language observational studies published within 10 years period were searched in Pubmed and Taylor and Francis databases.

Results

Nine articles were included in the systematic review. The incidence of positive ATTR among patients who underwent lumbar spinal surgery was 48% (95%CI 38-58%). ATTR deposits were found in the lumbar region the most frequently. Seven studies showed that patients with positive ATTR were older than those with negative. Five studies investigated and found a significant relationship between the ligamentum flavum thickness and positive ATTR. Five studies investigated cardiac involvement among patients with positive ATTR.

Conclusion

ATTR deposits are frequently found in older patients with spinal stenosis, especially in the lumbar region. The presence of ATTR deposits is related to ligamentum flavum thickness.

Transthyretin amyloidosis in spinal canal stenosis: A systematic review

We systematically review literature regarding the contribution of transthyretin amyloidosis to spinal stenosis. Amyloidosis is a protein misfolding condition that causes systemic deposition of amyloid and commonly leads to heart failure and nephropathy. A growing body of literature suggests that amyloid deposits within the ligamentum flavum are frequently associated with spinal stenosis with subsequent myelopathy. Our search identified 67 publications from the PubMed database for literature review. After evaluating the inclusion and exclusion criteria, a total of 18 articles were included in the review. Each article was evaluated for country, study type, sample size, amyloidosis subtype, spinal level, systemic symptoms, treatment, patient outcome, and conclusions. Many studies concluded that lumbar ligamentum flavum hypertrophy is more severe in patients with amyloidosis due to associated amyloid deposition. Additionally, patients with systemic amyloidosis are more likely to have recurrence of spinal stenosis. Multiple studies encourage routine screening be performed on spinal stenosis patients to target those needing cardiac surveillance. Amyloid deposition is frequently associated with spinal stenosis, and its presence may provide an earlier opportunity to diagnose or predict systemic amyloidosis. Surgeons should consider obtaining intraoperative biopsy to identify amyloidosis and inform screening postoperatively. Finally, physicians should be aware of this association and counsel patients accordingly on the risks and treatment options available for amyloidosis.

Neurological affection and serum neurofilament light chain in wild type transthyretin amyloidosis

In contrast to inherited transthyretin amyloidosis (A-ATTRv), neuropathy is not a classic leading symptom of wild type transthyretin amyloidosis (A-ATTRwt). However, neurological symptoms are increasingly relevant in A-ATTRwt as well. To better understand the role of neurological symptoms in A-ATTRwt, A-ATTRwt patients were prospectively characterized at Amyloidosis Center Charité Berlin (ACCB) between 2018 and 2023 using detailed neurological examination, quality of life questionnaires, and analysis of age- and BMI-adapted serum neurofilament light chain (NFL) levels. 16 out of 73 (21.9%) patients presented with a severe neuropathy which we defined by a Neuropathy Impairment Score (NIS) of 20 or more. In this group, quality of life was reduced, peripheral neuropathy was more severe, and spinal stenosis and joint replacements were frequent. Age- and BMI matched serum NFL levels were markedly elevated in patients with a NIS ≥ 20. We therefore conclude that highly abnormal values in neuropathy scores such as the NIS occur in A-ATTRwt, and have an important impact on quality of life. Both peripheral neuropathy and spinal canal stenosis are likely contributors. Serum NFL may serve as a biomarker for neurological affection in patients with A-ATTRwt. It will be important to consider neurological aspects of A-ATTRwt for diagnosis, clinical follow-up, and future treatment development.

Prevalence of amyloid in ligamentum flavum of patients with lumbar spinal stenosis

BACKGROUND

Transthyretin (ATTR) amyloidosis is often diagnosed in an advanced stage, when irreversible cardiac damage has occurred. Lumbar spinal stenosis (LSS) may precede cardiac ATTR amyloidosis by many years, offering the opportunity to detect ATTR already at the time of LSS surgery. We prospectively assessed the prevalence of ATTR in the ligamentum flavum by tissue biopsy in patients aged >50 years undergoing surgery for LSS.

METHODS

Ligamentum flavum thickness was assessed pre-operatively on axial T2 magnetic resonance imaging (MRI) slices. Tissue samples from ligamentum flavum were screened centrally by Congo red staining and immunohistochemistry (IHC).

RESULTS

Amyloid in the ligamentum flavum was detected in 74/94 patients (78.7%). IHC revealed ATTR in 61 (64.9%), whereas amyloid subtyping was inconclusive in 13 (13.8%). Mean thickness of ligamentum flavum was significantly higher at all levels in patients with amyloid (p < .05). Patients with amyloid deposits were older (73.1 ± 9.2 vs. 64.6 ± 10.1 years, p = .01). No differences in sex, comorbidities, previous surgery for carpal tunnel syndrome or LSS were observed.

CONCLUSIONS

Amyloid, mostly of the ATTR subtype, was found in four out of five patients with LSS and is associated with age and ligamentum flavum thickness. Histopathological work-up of ligamentum flavum might inform future decision making.

Transthyretin amyloid deposition in ligamentum flavum (LF) is significantly correlated with LF and epidural fat hypertrophy in patients with lumbar spinal stenosis

Lumbar spinal stenosis (LSS) is a degenerative disease characterized by intermittent claudication and numbness in the lower extremities. These symptoms are caused by the compression of nerve tissue in the lumbar spinal canal. Ligamentum flavum (LF) hypertrophy and spinal epidural lipomatosis in the spinal canal are known to contribute to stenosis of the spinal canal: however, detailed mechanisms underlying LSS are still not fully understood. Here, we show that surgically harvested LFs from LSS patients exhibited significantly increased thickness when transthyretin (TTR), the protein responsible for amyloidosis, was deposited in LFs, compared to those without TTR deposition. Multiple regression analysis, which considered age and BMI, revealed a significant association between LF hypertrophy and TTR deposition in LFs. Moreover, TTR deposition in LF was also significantly correlated with epidural fat (EF) thickness based on multiple regression analyses. Mesenchymal cell differentiation into adipocytes was significantly stimulated by TTR in vitro. These results suggest that TTR deposition in LFs is significantly associated with increased LF hypertrophy and EF thickness, and that TTR promotes adipogenesis of mesenchymal cells. Therapeutic agents to prevent TTR deposition in tissues are currently available or under development, and targeting TTR could be a potential therapeutic approach to inhibit LSS development and progression.

Musculoskeletal manifestations associated with transthyretin-mediated (ATTR) amyloidosis: a systematic review

BACKGROUND

Hereditary and wild-type transthyretin-mediated (ATTRv and ATTRwt) amyloidoses result from the misfolding of transthyretin and aggregation of amyloid plaques in multiple organ systems. Diagnosis of ATTR amyloidosis is often delayed due to its heterogenous and non-specific presentation. This review investigates the association of musculoskeletal (MSK) manifestations with ATTR amyloidosis and the delay from the onset of these manifestations to the diagnosis of ATTR amyloidosis.

METHODS

This systematic review utilized Medline and EMBASE databases. Search criteria were outlined using a pre-specified patient, intervention, comparator, outcome, time, study (PICOTS) criteria and included: amyloidosis, ATTR, and MSK manifestations. Publication quality was assessed utilizing Joanna Briggs Institute (JBI) critical appraisal checklists. The search initially identified 7,139 publications, 164 of which were included. PICOTS criteria led to the inclusion of epidemiology, clinical burden and practice, pathophysiology, and temporality of MSK manifestations associated with ATTR amyloidosis. 163 publications reported on ATTR amyloidosis and MSK manifestations, and 13 publications reported on the delay in ATTR amyloidosis diagnosis following the onset of MSK manifestations.

RESULTS

The MSK manifestation most frequently associated with ATTR amyloidosis was carpal tunnel syndrome (CTS); spinal stenosis (SS) and osteoarthritis (OA), among others, were also identified. The exact prevalence of different MSK manifestations in patients with ATTR amyloidosis remains unclear, as a broad range of prevalence estimates were reported. Moreover, the reported prevalence of MSK manifestations showed no clear trend or distinction in association between ATTRv and ATTRwt amyloidosis. MSK manifestations precede the diagnosis of ATTR amyloidosis by years, and there was substantial variation in the reported delay to ATTR amyloidosis diagnosis. Reports do suggest a longer diagnostic delay in patients with ATTRv amyloidosis, with 2 to 12 years delay in ATTRv versus 1.3 to 1.9 years delay in ATTRwt amyloidosis.

CONCLUSION

These findings suggest that orthopedic surgeons may play a role in the early diagnosis of and treatment referrals for ATTR amyloidosis. Detection of MSK manifestations may enable earlier diagnosis and administration of effective treatments before disease progression occurs.

Transthyretin Cardiac Amyloidosis: A Cardio-Orthopedic Disease

Orthopaedic manifestations of wild-type transthyretin amyloidosis are frequent and characteristic, including idiopathic bilateral carpal tunnel syndrome, idiopathic lumbar canal stenosis, atraumatic rupture of the brachial biceps tendon, and, more rarely, finger disease and rotator cuff. These manifestations often coexisting in the same patient, frequently male and aged, steadily precede cardiac involvement inducing a rapidly progressive heart failure with preserved ejection fraction. Although transthyretin cardiac amyloidosis remains a cardiac relevant disease, these extracardiac localisation may increase diagnostic suspicion and allow for early diagnosis assuming the role of useful diagnostic red flags, especially in light of new therapeutic opportunities that can slow or stop the progression of the disease. For the cardiologist, the recognition of these extracardiac red flags is of considerable importance to reinforce an otherwise less emerging diagnostic suspicion. For orthopedists and rheumatologists, the presence in an old patient with or without clinical manifestations of cardiovascular disease, of an unexpected and inexplicable constellation of musculoskeletal symptoms, can represent a fundamental moment for an early diagnosis and treatment is improving a patient's outcome.

Analysis of lumbar spine stenosis specimens for identification of amyloid

BACKGROUND

Lumbar spinal stenosis (LSS) is a common reason for spine surgery in which ligamentum flavum is resected. Transthyretin (TTR) amyloid is an often unrecognized and potentially modifiable mechanism for LSS that can also cause TTR cardiac amyloidosis. Accordingly, older adult patients undergoing lumbar spine (LS) surgery were evaluated for amyloid and if present, the precursor protein, as well as comprehensive characterization of the clinical phenotype.

METHODS

A prospective, cohort study in 2 academic medical centers enrolled 47 subjects (age 69 ± 7 years, 53% male) undergoing clinically indicated LS decompression. The presence of amyloid was evaluated by Congo Red staining and in those with amyloid, precursor protein was determined by laser capture microdissection coupled to mass spectrometry (LCM-MS). The phenotype was assessed by disease-specific questionnaires (Swiss Spinal Stenosis Questionnaire and Kansas City Cardiomyopathy Questionnaire) and the 36-question short-form health survey, as well as biochemical measures (TTR, retinol-binding protein, and TTR stability). Cardiac testing included technetium-99m-pyrophosphate scintigraphy, electrocardiograms, echocardiograms, and cardiac biomarkers as well as measures of functional capacity.

RESULTS

Amyloid was detected in 16 samples (34% of participants) and was more common in those aged ≥ 75 years of age (66.7%) compared with those <75 years (22.3%, p < 0.05). LCM-MS demonstrated TTR as the precursor protein in 62.5% of participants with amyloid while 37.5% had an indeterminant type of amyloid. Demographic, clinical, quality-of-life measures, electrocardiographic, echocardiographic, and biochemical measures did not differ between those with and without amyloid. Among those with TTR amyloid (n = 10), one subject had cardiac involvement by scintigraphy.

CONCLUSIONS

Amyloid is detected in more than a third of older adults undergoing LSS. Amyloid is more common with advancing age and is particularly common in those >75 years old. No demographic, clinical, biochemical, or cardiac parameter distinguished those with and without amyloid. In more than half of subjects with LS amyloid, the precursor protein was TTR indicating the importance of pathological assessment.

Lumbar stenosis due to wild-type transthyretin amyloid-induced thickening of the ligamentum flavum: a separate etiology from degeneration of intervertebral discs?

OBJECTIVE

Wild-type transthyretin amyloid (ATTRwt) is deposited in the ligamentum flavum (LF) of a subset of patients with spinal stenosis who undergo decompressive surgery, although its role in the pathophysiology of spinal stenosis is unknown. It has been theorized that degeneration of intervertebral discs causes increased mechanical stress and inflammatory/degenerative cascades and ultimately leads to LF fibrosis. If ATTRwt deposits contribute to LF thickening and spinal stenosis through a different pathway, then patients with ATTRwt may have less severe disc degeneration than those without it. In this study, the authors compared the severity of disc degeneration between patients with lumbar stenosis with and without amyloid in their LF to test whether ATTRwt is a unique contributor to LF thickening and spinal stenosis.

METHODS

Of 324 consecutive patients between 2018 and 2019 who underwent decompression surgery for spinal stenosis and had LF samples sent for pathological analysis, 31 harboring ATTRwt were compared with 88 controls. Patient medical records were retrospectively reviewed for demographic and surgical information. Disc degeneration was assessed on preoperative T2-weighted MR images with the modified Pfirrmann grading system at every lumbar disc level.

RESULTS

Baseline characteristics were similar between the groups, except for a statistically significant increase in age in the ATTRwt group. The crude unadjusted comparisons between the groups trended toward a less severe disc degeneration in the ATTRwt group, although this difference was not statistically significant. A multivariable linear mixed-effects model was created to adjust for the effects of age and to isolate the influence of ATTRwt, the presence of an operation at the level, and the specific disc level (between L1 and S1). This model revealed that ATTRwt, the presence of an operation, and the specific level each had significant effects on modified Pfirrmann scores.

CONCLUSIONS

Less severe disc degeneration was noted in patients with degenerative spinal stenosis harboring ATTRwt compared with those without amyloid. This finding suggests that ATTRwt deposition may play a separate role in LF thickening from that played by disc degeneration. Future studies should aim to elucidate this potentially novel pathophysiological pathway, which may uncover an exciting potential for the development of amyloid-targeted therapies that may help slow the development of spinal stenosis.

The Relationship Between Wild-Type Transthyretin Amyloid Load and Ligamentum Flavum Thickness in Lumbar Stenosis Patients

BACKGROUND

One key contributor to lumbar stenosis is thickening of the ligamentum flavum (LF), a process still poorly understood. Wild-type transthyretin amyloid (ATTRwt) has been found in the LF of patients undergoing decompression surgery, suggesting that amyloid may play a role. However, it is unclear whether within patients harboring ATTRwt, the amount of amyloid is associated with LF thickness.

METHODS

From an initial cohort of 324 consecutive lumbar stenosis patients whose LF specimens from decompression surgery were sent for analysis (2018-2019), 33 patients met the following criteria: 1) Congo red-positive amyloid in the LF, 2) ATTRwt by mass spectrometry-based proteomics, and 3) an available preoperative magnetic resonance imaging. Histological specimens were digitized, and amyloid load was quantified through Trainable Weka Segmentation machine learning. LF thicknesses were manually measured on axial T2-weighted preoperative magnetic resonance imaging scans at each lumbar level, L1-S1. The sum of thicknesses at every lumbar LF level (L1-S1) equals "lumbar LF burden".

RESULTS

Patients had a mean age of 72.7 years (range = 59-87), were mostly male (61%) and white (82%), and predominantly had surgery at L4-L5 levels (73%). Amyloid load was positively correlated with LF thickness (R = 0.345, P = 0.0492) at the levels of surgical decompression. Furthermore, amyloid load was positively correlated with lumbar LF burden (R = 0.383, P = 0.0279).

CONCLUSIONS

Amyloid load is positively correlated with LF thickness and lumbar LF burden across all lumbar levels, in a dose-dependent manner. Further studies are needed to validate these findings, uncover the underlying pathophysiology, and pave the way toward using therapies that slow LF thickening.

Machine Learning Quantification of Amyloid Deposits in Histological Images of Ligamentum Flavum

Wild-type transthyretin amyloidosis (ATTRwt) is an underdiagnosed and potentially fatal disease. Interestingly, ATTRwt deposits have been found to deposit in the ligamentum flavum (LF) of patients with lumbar spinal stenosis before the development of systemic and cardiac amyloidosis. In order to study this phenomenon and its possible relationship with LF thickening and systemic amyloidosis, a precise method of quantifying amyloid deposits in histological slides of LF is critical. However, such a method is currently unavailable. Here, we present a machine learning quantification method with Trainable Weka Segmentation (TWS) to assess amyloid deposition in histological slides of LF. Images of ligamentum flavum specimens stained with Congo red are obtained from spinal stenosis patients undergoing laminectomies and confirmed to be positive for ATTRwt. Amyloid deposits in these specimens are classified and quantified by TWS through training the algorithm via user-directed annotations on images of LF. TWS can also be automated through exposure to a set of training images with user-directed annotations, and then applied] to a set of new images without additional annotations. Additional methods of color thresholding and manual segmentation are also used on these images for comparison to TWS. We develop the use of TWS in images of LF and demonstrate its potential for automated quantification. TWS is strongly correlated with manual segmentation in the training set of images with user-directed annotations (R = 0.98; p = 0.0033) as well as in the application set of images where TWS was automated (R = 0.94; p = 0.016). Color thresholding was weakly correlated with manual segmentation in the training set of images (R = 0.78; p = 0.12) and in the application set of images (R = 0.65; p = 0.23). TWS machine learning closely correlates with the gold-standard comparator of manual segmentation and outperforms the color thresholding method. This novel machine learning method to quantify amyloid deposition in histological slides of ligamentum flavum is a precise, objective, accessible, high throughput, and powerful tool that will hopefully pave the way towards future research and clinical applications.

Unraveling a rare cause of spinal stenosis: Coexistent AL and ATTR amyloidosis involving the ligamentum flavum

Background:

Amyloidosis is a protein misfolding disorder that leads to the deposition of beta-pleated sheets of a fibrillar derivative of various protein precursors. Identification of the type of precursor protein is integral in treatment decision-making. The presence of two different types of amyloid in the same patient is unusually rare, and there are no previous reports of two different types of amyloid deposition in the ligamentum flavum (LF) in the same patient.

Case Description:

Here, we describe two patients with spinal stenosis who underwent laminectomies and were found to have AL and ATTR amyloid deposits in the LF.

Conclusion:

As the spine is becoming recognized as a site for ATTRwt amyloid deposition, patients undergoing spinal decompression surgery may potentially benefit from evaluation for amyloidosis in the LF.

Association between spinal stenosis and wild-type ATTR amyloidosis

Age-related cardiac amyloidosis results from deposits of wild-type tranthyretin amyloid (ATTRwt) in cardiac tissue. ATTR may play a role in carpal tunnel syndrome (CTS) and in spinal stenosis (SS), indicating or presaging systemic amyloidosis. We investigated consecutive patients undergoing surgery for SS for ATTR deposition in the resected ligamentum flavum (LF) and concomitant risk of cardiac amyloidosis. Each surgical specimen (LF) was stained with Congo red, and if positive, the amyloid deposits were typed by mass spectrometry. Patients with positive specimens underwent standard of care evaluation with fat pad aspirates, serum and urine protein electrophoresis with immunofixation, free light-chain assay, TTR gene sequencing and technetium 99 m-pyrophosphate-scintigraphy. In 2018-2019, 324 patients underwent surgery for SS and 43 patients (13%) had ATTR in the LF with wild-type TTR gene sequences. Two cases of ATTRwt cardiac amyloidosis were diagnosed and received treatment. In this large series, ATTRwt was identified in 13% of the patients undergoing laminectomy for SS. Patients with amyloid in the ligamentum flavum were older and had a higher prevalence of CTS, suggesting a systemic form of ATTR amyloidosis involving connective tissue. Further prospective study of patients with SS at risk for systemic amyloidosis is warranted.

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.