The Great Masquerader: Acanthamoeba-Associated Myelopathy Mimicking Tropical Spastic Paraparesis

The great masquerader: Acanthamoeba myelopathy mimicking tropical spastic paraparesis–a case series | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The great masquerader: Acanthamoeba myelopathy mimicking tropical spastic paraparesis–a case series Remya Prakash, Aravind Reghukumar, Rammohan K, Jaichand Johnson, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8299041/v3 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Feb, 2026 Read the published version in Neurological Sciences → Version 3 posted You are reading this latest preprint version Show more versions Abstract Acanthamoeba spp. typically causes granulomatous amoebic encephalitis in immunocompromised hosts. ¹ We describe three apparently immunocompetent patients who presented with progressive spastic quadriparesis to our hospital in Kerala, India. Neuroimaging showed parenchymal changes in the spinal cord in two patients. After extensive evaluation for common causes of noncompressive myelopathy proved unrevealing, Free-Living Amoeba-associated Parainfectious Neuroinflammation (FLA-PIN) was considered. Amoeba-specific PCR of cerebrospinal fluid (CSF) confirmed Acanthamoeba species in all cases. Patients responded to anti-acanthamoeba therapy with significant clinical and CSF improvement. Probable exposure routes included skin breach and nasal ablution. This series demonstrates that Acanthamoeba infection warrants inclusion in the differential diagnosis of noncompressive myelopathy. CSF wet mount and molecular testing should be performed in inflammatory myelopathies to prevent misdiagnosis as incurable neurodegenerative diseases. Neurology Infectious Diseases free-living amoeba Acanthamoeba FLA-PIN parainfectious neuroinflammation tropical spastic paraparesis noncompressive myelopathy GAE. Figures Figure 1 Figure 2 Figure 3 Full Text Additional Declarations The authors declare no competing interests. Supplementary Files supplementaryfile.docx Table 1: COMPREHENSIVE PATIENT TIMELINE (All Three Cases) supplementarytable2.docx Supplementary Table 2: Cerebrospinal Fluid (CSF) Analysis Chart Cite Share Download PDF Status: Published Journal Publication published 27 Feb, 2026 Read the published version in Neurological Sciences → Version 3 posted You are reading this latest preprint version Show more versions Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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architecture.\u003c/p\u003e\n\u003cp\u003e(b) T2-weighted image demonstrating hyperintense intramedullary signal changes (blue arrow) involving the mid-to-lower cervical cord segments\u003c/p\u003e\n\u003cp\u003e(c) Short tau inversion recovery (STIR) sequence confirming the hyperintense signal abnormalities with enhanced lesion conspicuity\u003c/p\u003e\n\u003cp\u003e(d) T1-weighted post-contrast image showing patchy enhancement (blue arrows) within the affected cord segments, indicating active inflammation and blood-spinal cord barrier disruption.\u003c/p\u003e","description":"","filename":"H1Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8299041/v3/d3f6f6849db995ca30c1c337.png"},{"id":99791554,"identity":"ff7f4db8-9272-40aa-adf9-3333ce8f0784","added_by":"auto","created_at":"2026-01-08 13:02:39","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":16378,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAcanthamoeba spp. detected in CSF DNA by PCR for Case 2 (41-year-old female).\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLane details: NC (Negative Control), FLA82 (Acanthamoeba spp. from Case 2), FLA81 (Acanthamoeba spp. from a separate patient isolate), PC (Positive Control), and LADDER (DNA Ladder).\u003c/p\u003e","description":"","filename":"PCR.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8299041/v3/c813603f3e9094467f0cf292.jpg"},{"id":99791394,"identity":"8cc92e88-f1e6-470c-be41-6eb3c6bc9f36","added_by":"auto","created_at":"2026-01-08 12:59:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":757641,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMagnetic resonance imaging of cervical and thoracic spinal cord\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e(a-d) Sagittal sections of the cervical spine showing intramedullary signal abnormalities spanning multiple vertebral segments.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e(a) T1-weighted image demonstrating cord expansion with isointense to mildly hypointense signal changes\u003c/p\u003e\n\u003cp\u003e(b) T2-weighted image revealing diffuse hyperintense intramedullary signal abnormalities\u003c/p\u003e\n\u003cp\u003e(c) Short tau inversion recovery (STIR) sequence confirming longitudinal hyperintense signal changes (blue arrows) with fat suppression, highlighting the inflammatory nature of the lesions.\u003c/p\u003e\n\u003cp\u003e(d) T1- weighted post-contrast image showing patchy enhancement throughout the affected segments\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e(e-f) Sagittal sections of the thoracic spine.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e(e) T1-weighted image showing continuation of the lesion into the upper thoracic segments.\u003c/p\u003e\n\u003cp\u003e(f) T2-weighted image demonstrating persistent hyperintense intramedullary signal abnormalities in the thoracic cord (blue arrow)\u003c/p\u003e","description":"","filename":"I1Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-8299041/v3/a22c7cecb93c9b5d167d34d3.png"},{"id":103775379,"identity":"d9ac0b23-8fcb-4c31-8994-a5883d84e514","added_by":"auto","created_at":"2026-03-02 18:32:43","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":590503,"visible":true,"origin":"","legend":"","description":"","filename":"manuscriptpreprint.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8299041/v3_covered_b395cb67-4cb6-4250-8eca-39e3a0c171c3.pdf"},{"id":99792956,"identity":"23e10156-da64-4b5d-8f46-d5b25977826c","added_by":"auto","created_at":"2026-01-08 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authors declare no competing interests.","formattedTitle":"The great masquerader: Acanthamoeba myelopathy mimicking tropical spastic paraparesis–a case series","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"Government Medical College","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"free-living amoeba; Acanthamoeba; FLA-PIN; parainfectious neuroinflammation; tropical spastic paraparesis; noncompressive myelopathy; GAE.","lastPublishedDoi":"10.21203/rs.3.rs-8299041/v3","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8299041/v3","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003eAcanthamoeba\u003c/em\u003e spp. typically causes granulomatous amoebic encephalitis in immunocompromised hosts. ¹ We describe three apparently immunocompetent patients who presented with progressive spastic quadriparesis to our hospital in Kerala, India. Neuroimaging showed parenchymal changes in the spinal cord in two patients. After extensive evaluation for common causes of noncompressive myelopathy proved unrevealing, Free-Living Amoeba-associated Parainfectious Neuroinflammation (FLA-PIN) was considered. Amoeba-specific PCR of cerebrospinal fluid (CSF) confirmed \u003cem\u003eAcanthamoeba\u003c/em\u003e species in all cases. Patients responded to anti-acanthamoeba therapy with significant clinical and CSF improvement. Probable exposure routes included skin breach and nasal ablution. This series demonstrates that \u003cem\u003eAcanthamoeba \u003c/em\u003einfection warrants inclusion in the differential diagnosis of noncompressive myelopathy. 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