Arachnoid web presenting with acute myelopathy after minor trauma and subtle imaging findings - illustrative case

Sep 29, 2026

Arachnoid web (AW) is a rare cause of compressive myelopathy, and imaging findings can be subtle, making diagnosis difficult. A 29-year-old man developed paraparesis with bladder and rectal dysfunction after a minor traffic accident. CT showed no fractures, and MRI demonstrated no intramedullary signal change, with only mild cord indentation and anterior deviation at T7–8. Microsurgical resection revealed thickened arachnoid tissue compressing and tethering the spinal cord. Postoperatively, cord pulsation restored and motor function improved, and histopathology confirmed AW.

LanguageEnglish

CategoryHealthcare

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Pages5

Reading Time13 min

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Case Lessons

Background

Observations

Lessons

Illustrative Case

Clinical Findings

Imaging

Management

Pathology

Outcome

JOURNAL OF NEUROSURGERY: Case Lessons J Neurosurg Case Lessons 11(1): CASE25734, 2026 DOI: 10.3171/CASE25734 Arachnoid web presenting with acute myelopathy after minor trauma and subtle imaging findings: illustrative case *Shinichiro Tsukamoto, MD,1,2 Gaku Hidaka, MD,1 Masashi Uchida, MD,1 Yuichiro Kushiro, MD,1 Sora Yazaki, MD,1 Risa Sakuyama, MD,1,2 Hiroshi Takasuna, MD, PhD,1 Hidemichi Itoh, MD, PhD,1 Takashi Matsumori, MD, PhD,1 Ichiro Takumi, MD, PhD,1 Toshihiro Ueda, MD, PhD,1 and Hidetoshi Murata, MD, PhD1 1Department of Neurosurgery, St. Marianna University School of Medicine, Kawasaki; and 2Department of Neurosurgery, Graduate School of Medicine, Yokohama City University, Yokohama, Japan BACKGROUND Arachnoid web (AW) is a rare entity characterized by a thickened band of arachnoid membrane on the dorsal surface of the spinal cord, often producing compressive myelopathy. The diagnosis is sometimes challenging, as imaging findings may be subtle. OBSERVATIONS The authors report the case of a 29-year-old man who developed paraparesis with bladder and rectal dysfunction following a minor traffic accident. Imaging showed no fractures or intramedullary signal changes, with only subtle spinal cord anterior deviation at T7–8 . Surgical exploration revealed a thickened arachnoid band compressing and tethering the spinal cord. Resection of the AW restored cord pulsation, and motor function improved postoperatively. Histopathology confirmed arachnoid tissue with collagen fibers, consistent with AW. LESSONS Even with subtle imaging findings, AW should be suspected in trauma-related myelopathy, and timely surgical intervention can provide recovery. [https://thejns.org/doi/abs/10.3171/CASE25734](https://thejns.org/doi/abs/10.3171/CASE25734) KEYWORDS arachnoid web; spinal cord compression; thoracic spine; minor trauma; myelopathy; microsurgical resection Arachnoid web (AW) is a band-like thickening of the arachnoid membrane located on the dorsal spinal cord, most frequently in the thoracic region.1 Although rare, AW can cause myelopathy through cord compression, tethering, or CSF flow obstruction.2 The “scalpel sign” on MRI is considered characteristic,3,4 but it is not always present, and some cases show only subtle radiological changes.2,5 Reports of AW have been increasing in recent years, yet much remains unknown regarding its etiology and natural history.6 Proposed causes include congenital anomalies,7 arachnoiditis,8 trauma,6,9 prior surgery,6 or subarachnoid hemorrhage.6 Although most cases present with insidious onset, trauma may act as a trigger for symptom manifestation, making early recognition crucial. We present an instructive case of a young man in whom AW became symptomatic after minor trauma, highlighting the diagnostic challenges, intraoperative findings, and histopathological confirmation, and discuss the clinical significance in the context of previously reported trauma-related cases. Illustrative Case A 29-year-old man was involved in a traffic accident and developed bilateral lower limb weakness and bladder-rectal dysfunction. He had no preexisting neurological symptoms. Clinical Findings Neurological examination revealed paraparesis (manual muscle testing [MMT]: iliopsoas grade 4/5 bilaterally, quadriceps grade 4/5, tibialis anterior grade 3/5) and sensory loss distal to the ankles. He ABBREVIATIONS AW = arachnoid web; MMT = manual muscle testing. INCLUDE WHEN CITING Published January 5, 2026; DOI: 10.3171/CASE25734 . SUBMITTED September 19, 2025. ACCEPTED November 20, 2025. * S.T. and G. H. contributed equally to this work. © 2026 The authors, CC BY-NC-ND 4.0 ([http://creativecommons.org/l](http://creativecommons.org/l)icenses/by-nc-nd/4 .0/) J Neurosurg Case Lessons | Vol 11 | Issue 1 | January 5, 2026 | 1 also reported numbness in both feet and impaired bladder-rectal sensation, although spontaneous voiding was preserved. Imaging Thoracic CT showed no fract

FAQs

Why was the diagnosis challenging in this case?

Imaging showed no fractures or intramedullary signal changes, with only subtle anterior deviation and indentation at T7–8, which can make AW difficult to recognize.

What intraoperative finding confirmed the presence of arachnoid web?

Surgery revealed thickened arachnoid tissue compressing and tethering the spinal cord, and complete resection restored spinal cord pulsation.

What was the patient’s postoperative outcome?

Motor function recovered to MMT grade 5/5 in all lower-extremity muscle groups, sensory disturbance improved, and follow-up MRI showed resolution of cord indentation and deviation at T7–8.

Sep 29, 2026

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