Where Neurosurgery Meets Heart Failure: A Case Report of a Patient with Amyloid Transthyretin Wild Type in the Ligamentum Flavum and Cardiac Tissue with Bilateral Carpal Tunnel Syndrome

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.

Comparative proteome analysis of the ligamentum flavum of patients with lumbar spinal canal stenosis

Background

Thickening of the ligamentum flavum is considered to be the main factor for lumbar spinal canal stenosis (LSCS). Although some mechanisms have been speculated in the thickening of the ligamentum flavum, there are only a few comprehensive approaches to investigate its pathology. The objective of this study was to investigate the pathology of thickened ligamentum flavum in patients with LSCS based on protein expression levels using shotgun proteome analysis.

Methods

Ligamentum flavum samples were collected from four patients with LSCS (LSCS group) and four patients with lumbar disc herniation (LDH) as controls (LDH group). Protein mixtures were digested and analyzed by liquid chromatography/mass spectrometry analysis. To compare protein expression levels between the LSCS and LDH groups, the mean Mascot score was compared. Biological processes were assessed using Gene Ontology analysis.

Results

A total of 1151 proteins were identified in some samples of ligamentum flavum. Among these, 145 proteins were detected only in the LSCS group, 315 in the LDH group, and 691 in both groups. The demonstrated biological processes occurring in the LSCS group included: extracellular matrix organization, regulation of peptidase activity, extracellular matrix disassembly, and negative regulation of cell growth. Proteins related to fibrosis, chondrometaplasia, and amyloid deposition were found highly expressed in the LSCS group compared with those in the LDH group.

Conclusions

Tissue repair via fibrosis, chondrometaplasia, and amyloid deposits may be important pathologies that occur in the thickened ligamentum flavum of patients with LSCS.

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.

[Cardiac amyloidosis and aortic valve stenosis]

Aortic valve stenosis in old age has become a topic of interest for cardiology and cardiac surgery after the development of transvascular and transluminal minimally invasive techniques for aortic valve implantation. The observation of amyloid deposits in surgically excised valvular material led to the diagnostics of amyloidosis of the myocardium, which was discovered in up to 20% of the patients who underwent valve implantation. Clinical signs of cardiac amyloidosis, such as carpal tunnel syndrome and ruptured distal biceps tendon should be taken into account. In addition to the electrocardiogram (ECG), echocardiogram and magnetic resonance imaging, ^99mtechnetium bone scintigraphy plays a key diagnostic role. The simultaneous occurrence of severe aortic valve stenosis and amyloidosis explains the special hemodynamic situation of a low gradient with low blood flow in high-grade valve stenosis. The interventional or surgical valve implantation improves the prognosis for these patients, similarly to aortic valve stenosis alone, followed by a specific pharmaceutical treatment depending on the type of amyloidosis.

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.

Orthopaedic Manifestations of Amyloidosis

Amyloidosis is a disorder of misfolded proteins in human tissues, which can result in morbid cardiac and neurological disease. Historically, the utility of tissue biopsy during orthopaedic procedures to detect amyloidosis has been limited because no disease-modifying therapies were available; however, new drug therapies have recently emerged for the treatment of amyloidosis. Although these novel pharmaceuticals show promise for slowing disease progression, they are primarily effective in the early stages of amyloidosis, underscoring the importance of early diagnosis. Common orthopaedic manifestations of amyloidosis include carpal tunnel syndrome, trigger finger, spontaneous distal biceps tendon rupture, rotator cuff disease, and lumbar spinal stenosis. Carpal tunnel syndrome is frequently the earliest manifestation of amyloidosis, on average preceding a formal diagnosis of amyloidosis by over four years. By recognizing the constellation of musculoskeletal symptoms in the patient with amyloidosis, orthopaedic surgeons can play an active role in patient referral, early detection of systemic disease, and prompt initiation of disease-modifying treatment. There may be a role for selective biopsy for amyloid deposition in at-risk patients during routine orthopaedic procedures.

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.

Wild-Type Transthyretin Amyloidosis Occurring in the Ligamentum Flavum of the Cervicothoracic Spine

BACKGROUND

Wild-type transthyretin amyloid (ATTRwt) has been noted to deposit in the ligamentum flavum of the spine. Prior studies have focused on ATTRwt in the lumbar region, but studies discussing its presence in other levels of the spine are lacking. We report on the presentation of patients with confirmed amyloid in the cervicothoracic regions and discuss the literature to date.

METHODS

We retrospectively identified patients at a single institution who underwent surgery for spinal stenosis and had pathologic specimens sent for amyloidosis testing with Congo red staining. ATTRwt was confirmed by the presence of transthyretin amyloid by typing and the absence of mutations in the TTR gene sequence. A final study group of patients with ATTRwt and spinal involvement was established (n = 27).

RESULTS

Of 27 patients with amyloid in the spine, 24 (89%) had amyloid present in the lumbar region, 2 (7%) had amyloid in the cervical region, and 1 (4%) had amyloid in the thoracic region. The median age at which patients in the study underwent surgery was 71 years (interquartile range: 9). Spinal stenosis was the indication for surgery in 26 of 27 (96%) patients. Surgery involved 1 or 2 spinal levels in 24 of 27 (89%) patients.

CONCLUSIONS

ATTRwt amyloid predominantly deposits in the lumbar region, but it can also be present in the cervical and thoracic regions. While the lumbar regions should remain a focus for evaluation of ATTRwt amyloidosis, the cervicothoracic region should not be ignored.