• Francesco Marchi, Chiara Kessler, Daniela Distefano, Lodovico Terzi di Bergamo, Luca Fumagalli, Manuela Averaimo, Emanuele Crupi, Fabio Bergamini, Giorgia Melli, Georg Stussi, Davide Rossi, Claudio Gobbi, Paolo Ripellino, Emanuele Pravatà, Dominique E Kuhlen, Christoph Röcken, Pietro Scarone, Bernhard Gerber, and Adalgisa Condoluci.
• Neurosurgical Service, Neurocenter of Southern Switzerland, Ente Ospedaliero Cantonale, Lugano, Switzerland.
• Amyloid. 2023 Dec 1; 30 (4): 416423416-423.

BackgroundTransthyretin (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.MethodsLigamentum 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).ResultsAmyloid 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.ConclusionsAmyloid, 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.

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