Sparganosis of the Cauda Equina: A Rare Case of Lower Thoracic Cord Edema and Diagnostic Challenges

Abstract

Sparganosis is a rare parasitic infection caused by the larvae of Spirometra species, with spinal involvement being exceedingly uncommon. We present the case of a 46-year-old woman with progressive lower limb weakness, sensory deficits, and bowel and bladder dysfunction over a 3-month period. Initial magnetic resonance imaging revealed an abnormal intradural lesion from L2 to S2, along with thoracic spinal cord edema, raising suspicion for a spinal dural arteriovenous fistula (DAVF). After referral to our institution, further imaging ruled out DAVF, and findings suggested arachnoiditis and radiculitis of the lumbosacral nerve roots. The patient underwent a laminectomy, revealing inflamed arachnoid membranes and diffuse yellowish-whitish granulation tissue adherent to the cauda equina, which histopathological analysis confirmed as sparganosis. Postoperatively, the patient showed improved motor strength, although bowel and bladder dysfunction persisted. This case highlights the diagnostic challenges of spinal sparganosis, the need for early surgical intervention, and the importance of considering parasitic infections in endemic regions.

 

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Keywords

sparganosis - cauda equina syndrome - thoracic spinal cord edema - parasitic infection - lumbosacral arachnoiditis

Introduction

Sparganosis is a rare parasitic infection caused by the plerocercoid larvae of the Spirometra species, primarily affecting subcutaneous tissues and muscles but occasionally involving the central nervous system (CNS). Humans can become accidental hosts through various routes, including ingestion of contaminated water or undercooked meat, particularly amphibians and reptiles, or through the application of raw animal flesh as poultices.[1] [2] [3] This parasitic infection is most seen in East and Southeast Asia, including China, Japan, Korea, and Thailand, where consumption of frogs and snakes is prevalent.[3] [4]

While sparganosis typically presents as migratory subcutaneous nodules, spinal involvement, particularly in the cauda equina, is exceedingly rare.[5] [6] Cauda equina sparganosis often presents with nonspecific symptoms such as progressive lower limb weakness, sensory disturbances, and bowel or bladder dysfunction, which can mimic other spinal pathologies like tumors or inflammatory conditions.[7] [8] These overlapping clinical and imaging findings make preoperative diagnosis challenging, with definitive identification typically requiring surgical excision and histopathological confirmation.[9]

In the present study, we report a rare instance of cauda equina sparganosis initially misdiagnosed as spinal dural arteriovenous fistula (DAVF).

 

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Case Report

A 46-year-old woman initially presented to a local hospital with progressive lower limb weakness, sensory impairment, and bowel and bladder dysfunction. These symptoms had developed over 3 months, beginning with mild lower back pain that gradually progressed to significant difficulty walking, urinary retention, and fecal incontinence. There was no history of trauma, recent infections, or ingestion of undercooked food such as frogs or snakes. Her past medical history was unremarkable.

Magnetic resonance imaging (MRI) of the spine performed at the local hospital revealed an abnormal intradural, heterogeneously enhancing lesion extending from L2 to S2. Additionally, significant edema was noted in the lower thoracic spine. Based on these findings, clinicians at the local hospital suspected a spinal DAVF and referred the patient to our institute for further evaluation, including spinal angiography and possible embolization. Upon admission to our institute, neurological examination revealed motor weakness in both lower extremities, graded ⅗ on the Medical Research Council (MRC) scale, diminished sensation below the L2 dermatome, and hypoactive deep tendon reflexes. The patient also exhibited reduced anal sphincter tone, consistent with cauda equina syndrome.

A review of the spinal MRI by our neuroradiologists revealed large intradural mass-like lesions occupying the entire thecal sac from L2 to S2. These lesions displayed isointense T1 signals and heterogeneous hyperintense T2 signals. Heterogeneous enhancement was observed within the thecal sac, along with multiple small filling defects that could not be distinguished from the cauda equina nerve roots. The abnormalities extended through bilateral lumbosacral lateral neural foramina, involving the exiting nerve roots. These findings suggested arachnoiditis and radiculitis of the lumbosacral nerve roots ([Fig. 1]). Additionally, MRI of the thoracic spine revealed abnormal T2-hyperintense signal changes in the lower thoracic spinal cord ([Fig. 2]), along with abnormal pial enhancement extending from T11 down to the conus medullaris. Further diagnostic tests, including contrast-enhanced spinal MR angiography (MRA), were performed and showed no evidence of abnormal vascular malformations. Laboratory tests showed mild eosinophilia, but other laboratory results were within normal limits. A parasitic infection, such as sparganosis, was considered a probable diagnosis.

Fig. 1 Magnetic resonance imaging of the lumbosacral spine. Sagittal T1-weighted (A), gadolinium-enhanced T1-weighted (B), T2-weighted (C), and axial gadolinium-enhanced T1-weighted images at the L2–3 (D), L3–4 (E), and L4–5 (F) levels reveal large intradural mass-like lesions occupying the entire thecal sac from L2 to S2. These lesions show isointense T1 signals, heterogeneous hyperintense T2 signals, and diffuse heterogeneous enhancement. No distinct spinal nerve roots are identified, likely due to clumping of the cauda equina.

Fig. 2 Magnetic resonance imaging of the lower thoracic spine. Sagittal T2-weighted image (A) and axial T2-weighted images at the T7 (B), T9 (C), and T12 (D) levels demonstrate abnormal T2-hyperintense parenchymal signal changes in the lower thoracic spinal cord.

The patient underwent a laminectomy from lower L2 to L5. After opening the dura, a thickened arachnoid membrane, diffuse yellowish-whitish granulation tissue, and severe adhesions of the nerve roots were observed ([Fig. 3A]). Under intraoperative neuromonitoring, subtotal removal of the granulation tissue and lysis of adhesions were performed. Tissue samples were sent for histopathological examination. The histopathological analysis of the excised tissue revealed parasitic structures with three distinct layers: an outer cuticular layer, a middle granular layer, and an inner fibrillary layer. Degenerated cuticles and calcareous bodies were observed within the parasite ([Fig. 3B, C]), confirming the diagnosis of spinal sparganosis.

Fig. 3 (A) Intraoperative photograph following durotomy in the prone position, showing diffuse yellowish-whitish granulation tissue and severe adhesions of the nerve roots. Hematoxylin and eosin staining; original magnification, ×200 (B) and ×600 (C). Histological examination of a surgical specimen from the lumbar area reveals parasitic tissue with three distinct layers: an outer cuticular layer, a middle granular layer, and an inner fibrillary layer. Degenerated cuticle (arrow) and calcareous bodies (arrowheads) within the parasite are visible. (D) Magnetic resonance imaging of the thoracolumbar spine obtained 1 year after surgery. The sagittal T2-weighted image reveals resolution of thoracic cord edema and decreased clumping of the cauda equina.

One week following surgery, a high dose of praziquantel (75 mg/kg/day) combined with cimetidine was prescribed for 7 days. Postoperatively, the patient showed significant improvement in lower limb motor strength, increasing to ⅘ on the MRC scale. However, despite the improvement in motor function, bowel and bladder dysfunction persisted. At the 1-year follow-up, her lower limb strength had further improved, though residual bowel and bladder dysfunction remained. MRI of the thoracolumbar spine demonstrated resolution of thoracic cord edema and reduced clumping of the cauda equina ([Fig. 3D]).

 

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Discussion

Sparganosis of the cauda equina presents unique diagnostic challenges due to its rarity and nonspecific clinical presentation. Clinical manifestations often include progressive weakness, sensory disturbances, and bowel–bladder dysfunction, mimicking other spinal pathologies such as tumors or vascular malformations.[1] [4] [5] [10] The involvement of the cauda equina complicates diagnosis, as imaging findings such as mass-like lesions and nerve root clumping are nonspecific and can be mistaken for other pathologies.[2] [6] Preoperative diagnosis based on clinical presentation and imaging alone is difficult, and histopathological confirmation remains the gold standard for diagnosis.[5] [11]

In the present study, the patient presented with progressive neurological deficits, and MRI revealed signs of lumbosacral arachnoiditis, radiculitis, and edema of the lower thoracic spine. This case highlights the diagnostic challenges posed by spinal sparganosis and underscores the importance of considering parasitic infections in the differential diagnosis of spinal lesions, especially in endemic regions.

Immunohistochemical and antibody tests can be valuable tools for diagnosing sparganosis, particularly in cases where histopathological findings alone may be inconclusive. Serological tests, such as enzyme-linked immunosorbent assay, are used to detect specific antibodies against Spirometra larvae in blood or cerebrospinal fluid, offering high sensitivity and specificity, especially in endemic areas.[2] [14] Molecular testing, including polymerase chain reaction, can also aid in confirming the diagnosis by detecting Spirometra deoxyribonucleic acid directly from tissue samples. However, despite their potential diagnostic utility, serological and molecular methods are not universally available, and limitations in resources can affect their accessibility at many institutions.[3] In our case, due to the lack of serological and molecular testing facilities, the diagnosis relied solely on histopathological findings, which provided definitive confirmation through the identification of characteristic parasitic structures.

Sparganosis, while rare, can coexist with spinal arteriovenous fistula (AVF), although such instances are exceedingly uncommon. To the best of our knowledge, there is only one documented case of spinal sparganosis associated with an acquired AVF of the filum terminale, reported by Iampreechakul et al in 2020.[12] In that case, the patient presented with progressive myelopathy and imaging revealed both an intradural mass and tortuous flow voids consistent with AVF, which were confirmed via spinal angiography. The authors hypothesized that the formation of the AVF might have been induced by chronic inflammation, fibrosis, and severe adhesion of the nerve roots, caused by the longstanding spinal canal stenosis from sparganosis. In our case, there was no evidence of an accompanying AVF, as confirmed by spinal MRA, but this underscores the need for heightened clinical suspicion of dual pathologies in patients with similar presentations. Given the documented coexistence in at least one case, it remains a plausible but rare differential diagnosis that should be considered in the workup of intraspinal lesions, particularly in endemic regions.

In the present study, surgical excision was required to obtain a definitive diagnosis, and histopathological examination revealed the presence of Sparganum larvae, consistent with previous reports of spinal sparganosis.[5] [13] The primary treatment for spinal sparganosis is surgical removal of the parasite, which is critical for preventing further neurological deterioration.[4] [6] Although antiparasitic agents such as praziquantel have been used, they are typically considered adjunctive therapy and have limited efficacy once the parasite invades the CNS.[11] [14]

Our case underscores the importance of considering parasitic infections, particularly in endemic regions, in the differential diagnosis of unexplained spinal lesions. Early surgical intervention is crucial for improving patient outcomes, although residual neurological deficits, such as persistent bowel and bladder dysfunction, may remain despite successful removal of the parasite.[6] [14] In endemic areas, a high index of suspicion and preoperative serological testing may aid in early diagnosis and reduce the risk of misdiagnosis.[2] [13]

 

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Conclusion

Spinal sparganosis is a rare but important cause of neurological deficits, often mimicking more common spinal pathologies such as tumors or vascular malformations. Early diagnosis is challenging due to the nonspecific clinical and imaging findings. In this case, the suspicion of a spinal DAVF was ruled out through advanced imaging, and the true diagnosis of sparganosis was confirmed through surgical excision and histopathological analysis. While surgical removal of the parasite can lead to significant improvement in motor function, long-term complications such as bowel and bladder dysfunction may persist. This case emphasizes the need for heightened clinical suspicion of parasitic infections in patients with unexplained spinal lesions, particularly in regions where sparganosis is endemic. Early surgical intervention remains critical for preventing further neurological deterioration and optimizing patient outcomes.

 

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Conflict of Interest

None declared.

Note

This study was reviewed and approved by the institutional review board.

Authors' Contributions

P.I. contributed to conceptualization, methodology, original draft preparation, and reviewing and editing the manuscript. C.A. handled data curation and validation. S.H. contributed through investigation, while S.T. managed data curation, visualization, and validation. A.T. provided resources essential to the study.

• References

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Publication History

Article published online:
30 December 2024