Spinal arachnoid web-a review article

Arachnoid webs causing rostral syrinx due to ball-valve effect: an illustrative report of two cases

An arachnoid web is a pathological formation of the arachnoid membrane. It is a rare phenomenon but is known to lead to syrinx formation in the spinal cord along with pain and neurological deficits. On imaging, the 'scalpel sign' is pathognomonic for an arachnoid web. The etiology of syrinx formation from an arachnoid web is currently unknown. This report documents the only two cases of arachnoid webs with an extensive syrinx in which a likely pathophysiologic mechanism is identified. Both cases presented with motor deficits. The patients had no history of trauma or infection. After extensive workup in both patients and observation of the scalpel sign an arachnoid web was suspected. In both cases, the patients were treated surgically after an arachnoid web was suspected. Intra-operative ultrasound visualized in both cases demonstrates a fenestration in the web that allowed passage of cerebrospinal fluid in a rostral-caudal direction due to a ball-valve effect.

Dorsal arachnoid web of the thoracic spine associated with an arachnoid cyst and a presyrinx state as an unexplained cause of thoracic myelopathy: illustrative case

BACKGROUND

Dorsal thoracic arachnoid web is a rare diagnosis and is not commonly seen in neurosurgical practice. Patients can present with symptoms and signs of thoracic myelopathy in the setting of an arachnoid cyst and a presyrinx state.

OBSERVATIONS

A 57-year-old male with a 10-year history of worsening bilateral leg weakness and chronic back pain re-presented to the neurosurgery clinic after being seen by neurology and orthopedic spine surgery. Initial imaging was concerning for myelomalacia and syringomyelia, and repeat delayed computed tomography myelography findings were consistent with an evolving thoracic arachnoid web, now demonstrating spinal cord compression secondary to arachnoid cyst formation and consistent with the signs of thoracic myelopathy. Intraoperative ultrasound displayed the arachnoid web as the cause of the evolving arachnoid cyst, edematous spinal cord, and a presyrinx-like state. The patient underwent surgical decompression, which restored cerebrospinal fluid (CSF) dynamics, resulting in clinical improvement.

LESSONS

Dorsal thoracic arachnoid web is a dynamic condition that can occur in the setting of an arachnoid cyst. There appears to be a relationship between dorsal thoracic arachnoid web formation and the presence of an arachnoid cyst resulting from a ball-valve mechanism leading to the creation of a pressure gradient effect that alters CSF fluid dynamics. https://thejns.org/doi/10.3171/CASE24313.

Intraspinal Intradural Arachnoid Web at the Thoracic Level: A Case Report

Arachnoid web is a rare condition, which can cause significant neurological symptoms due to spinal cord compression. This case highlights the clinical presentation, surgical management, and pathology of an arachnoid web, contributing to the understanding of this rare condition. A 68-year-old female presented with diffuse pain syndrome, gait disturbance, and left leg pain. Clinical-neurological examination indicated myelopathy, confirmed by magnetic resonance imaging (MRI) revealing an intraspinal intradural mass at T4 with early signs of myelopathy. Surgical removal of the mass was performed via right-sided hemilaminectomy and microsurgical excision. Intraoperative findings included a cerebrospinal fluid (CSF)-filled pouch beneath an abnormal arachnoid membrane. Pathological analysis identified connective tissue fragments consistent with an arachnoid cyst, without atypia or inflammation. Postoperative recovery showed reduced leg pain and improved mobility.

Scalpellum occulta: A rare case of dorsal spinal arachnoid web without the scalpel sign

Spinal arachnoid web is a rare condition characterized by extramedullary bands of arachnoid tissue at the level of the dorsal thoracic spinal cord that may lead to progressive, permanent neurological deficits. To date, this condition has been radiographically characterized by a scalpel sign, which has been pathognomonic in all reported cases of spinal arachnoid webs. In this case, we report the first known patient with confirmed spinal arachnoid web without radiographic evidence of the scalpel sign. In reporting our finding, we encourage a higher clinical suspicion for spinal arachnoid web in patients presenting with progressive thoracic myelopathy following trauma, and radiographic evidence of ventrally displaced spinal cord and turbulent cerebrospinal fluid flow, even in the absence of a scalpel sign.

Dorsal arachnoid web adjacent to paraspinal retained bullet: Blunt post-traumatic etiology

Dorsal arachnoid webs are uncommon, and of uncertain etiology. We present a case in which imaging findings of a dorsal arachnoid web were identified at the level of a known prior gunshot injury where a retained bullet was lodged adjacent to the spine, without associated penetrating injury to the spine, suggesting blunt post-traumatic etiology.

Arachnoid webs with spinal cord compression: insights from three cases

Spinal arachnoid webs are intradural bands of abnormally formed arachnoid tissue, located within the subarachnoid space and causing compression of the dorsal aspect of the spinal cord. Arachnoid webs are uncommon and can be difficult to treat. We report 3 patients presenting with a spinal arachnoid web within a 6-month period. All of them exhibited signs of thoracic myelopathy and the MRI showed the pathognomonic 'scalpel sign'. Two of the patients underwent surgery for removal of their spinal arachnoid web, whereas the third patient case is currently being managed conservatively. We also present our 2D intraoperative video for arachnoid web removal and spinal cord decompression.

The occult spinal arachnoid web with inimitable imaging: a case report with 5 years of follow-up

OBJECTIVES

The spinal arachnoid web (SAW) is intradural extramedullary thickened bands of the arachnoid tissue, causing a focal indentation of the spinal cord. In our study, we sought to provide a comprehensive description of the nonoperative progression of this condition, drawing from a 5-year follow-up based on our institutional experience.

CASE PRESENTATION

A 67-year-old male patient, presenting with chest and back pain, was admitted to our hospital. During a constructive interference in steady state (CISS) sequence examination, a typical dorsal indentation of the spinal cord at thoracic vertebrae referred to as the "scalpel sign", was noted. Subsequently, a diagnosis of SAW was confirmed. The patient refused surgical intervention and underwent a series of three MR imaging sessions over 5 years.

CONCLUSION

SAW is a rarely reported pathology with varying clinical presentation and whose etiology remains unknown. Secondary syrinx formation may be a consequence of chronically altered cerebrospinal fluid dynamics. The CISS sequence can visualize the SAW despite its comparatively thin width. The web is commonly curable, and treatment should be personalized and take into consideration the severity of symptoms, as well as clinical and radiological findings.

Pediatric intraspinal arachnoid cyst: successful endoscopic fenestration. Illustrative case

BACKGROUND

Intradural spinal arachnoid cysts (SACs) are a rare cause of spinal cord compression. Treatment is centered on decompression of the spinal cord via laminectomy or laminoplasty followed by resection or fenestration of the cyst. Although laminectomy or laminoplasty access may be needed to achieve the desired result, either procedure can be associated with more extensive surgical dissections and long-term spinal stability concerns, including postsurgical kyphosis.

OBSERVATIONS

The authors present a case of a cervical intradural SAC in a 4-month-old girl presenting with symptomatic compression. The patient was treated by laminotomy and endoscopic fenestration of the SAC with resolution of symptoms and no disease progression 10 months postoperatively, when the patient was 14 months old.

LESSONS

Microsurgical endoscopic fenestration of an intradural SAC can provide a less invasive means of treatment while avoiding the risks associated with more invasive approaches.

Surgical management of syringomyelia associated with spinal arachnoid web: strategies and outcomes

Spinal arachnoid web (SAW) is a rare disease entity characterized as band-like arachnoid tissue that can cause spinal cord compression and syringomyelia. This study aimed to analyze the surgical management of the spinal arachnoid web in patients with syringomyelia, focusing on surgical strategies and outcomes. A total of 135 patients with syringomyelia underwent surgery at our department between November 2003 and December 2022. All patients underwent magnetic resonance imaging (MRI), with a special syringomyelia protocol (including TrueFISP and CINE), and electrophysiology. Among these patients, we searched for patients with SAW with syringomyelia following careful analysis of neuroradiological data and surgical reports. The criteria for SAW were as follows: displacement of the spinal cord, disturbed but preserved CSF flow, and intraoperative arachnoid web. Patients were evaluated for initial symptoms, surgical strategies, and complications by reviewing surgical reports, patient documents, neuroradiological data, and follow-up data. Of the 135 patients, 3 (2.22%) fulfilled the SAW criteria. The mean patient age was 51.67 ± 8.33 years. Two patients were male, and one was female. The affected levels were T2/3, T6, and T8. Excision of the arachnoid web was performed in all cases. No significant change in intraoperative monitoring was noted. Postoperatively, none of the patients presented new neurological symptoms. The MRI 3 months after surgery revealed that the syringomyelia improved in all cases, and caliber variation of the spinal cord could not be detected anymore. All clinical symptoms improved. In summary, SAW can be safely treated by surgery. Even though syringomyelia usually improves on MRI and symptoms also improve, residual symptoms might be observed. We advocate for clear criteria for the diagnosis of SAW and a standardized diagnostic (MRI including TrueFISP and CINE).

A case of neurosurgical treatment of thoracic dorsal arachnoid web

Background

Dorsal arachnoid webs constitute abnormal formations of arachnoid that tend to occur in the upper thoracic spine and can lead to spinal cord displacement. Patients typically present with back pain, sensory disturbances, and weakness. It may also obstruct the cerebrospinal fluid (CSF) flow, leading to syringomyelia. In magnetic resonance (MR) studies, the "scalpel sign" is a classical finding, and it may also be accompanied by syringomyelia attributed to CSF flow. Definitive surgical resection is the mainstay of treatment.

Case Description

A 31-year-old male presented with mild weakness in the right leg and diffuse lower extremity sensory changes. The MR showed the typical "scalpel sign" at the T7 level consistent with diagnosing a spinal arachnoid web. He underwent a T6-T8 laminotomy for lysis of the web and decompression of the thoracic cord. Postoperatively, his symptoms improved markedly.

Conclusion

Surgical resection is the treatment of choice when an arachnoid web is documented on an MR and correlates with the patient's clinical symptoms/signs.

Long-term outcome of surgical treatment for idiopathic spinal arachnoid web: A case series

OBJECTIVE

Spinal arachnoid web (SAW) is a rare condition of the spine with limited long-term follow-up data in the literature. The longest reported follow-up period was an average 3.2 years. The objective of this study is to report our long-term results of patients who underwent surgical treatment for symptomatic idiopathic SAW.

METHODS

We conducted a retrospective review of cases of idiopathic SAW that were operated between 2005-2020. We collected preoperative and last follow-up (LFU) data on motor force, sensory loss, pain, upper motor neuron (UMN) sign, gait disorder, sphincter dysfunction, syringomyelia, hyperintensity on T2-MRI, appearance of newer symptoms and number of reoperations.

RESULTS

Our study included 9 patients with a mean follow-up period of 3.6years (range 2-9.1years). The surgical intervention involved a standard centered laminectomy, durotomy and arachnoid lysis. At presentation, motor weakness was present in 77.8% of patients, sensory loss in 66.7%, pain in 88.9%, sphincter dysfunction in 33.3%, UMN sign in 22%, gait disorder 55.6%, syringomyelia in 55.6% and MRI T2 hyperintensity in 55.6% of patients. At LFU, there was an improvement in all symptoms and signs to varying degrees. No new neurological symptoms appeared postoperatively, and there was no recurrence during the follow-up period.

CONCLUSION

Our results demonstrate that the reported immediate and short-term favorable outcomes following arachnoid lysis for symptomatic SAW persist over a long-term period and the risk of readhesion-correlated neurological deterioration following conventional surgical intervention is low.

Spinal arachnoid webs in adults: Clinical and imaging features in a multicenter study

BACKGROUND AND PURPOSE

Spinal arachnoid webs (SAWs) are rare and can present with myelopathic symptoms. This study aims to add 85 more cases of SAWs to the literature so we can continue to analyze clinical and imaging trends of SAWs to better understand this entity and its natural history.

METHODS

An institutional review board-approved retrospective review of SAW cases between 2016 and 2022 within a metropolitan, multihospital network was performed, searching for MR and CT reports that included "arachnoid web." Of 108 identified reports, 85 patients had imaging and/or pathologically proven arachnoid webs. Demographic and clinical data were collected. Images were analyzed for SAW level, point of maximum kyphosis, presence of cord expansion, and signal intensity. The electronic medical record (EMR) was reviewed for age, sex, symptom presentation and duration, management, and outcomes.

RESULTS

Of 85 cases, the most common presenting chief complaint was back pain and weakness. All (100%) SAWs were in the dorsal thoracic subarachnoid space, with 87% (74/85) located from thoracic (T) 2 to T6. Spinal cord expansion and signal abnormality were present in 54.1% and 23.5%, respectively. Twenty-six underwent surgical resection with 20 showing improvement of at least one symptom.

CONCLUSION

We present 85 additional cases of SAWs to the existing literature. Our cases all occurred in the dorsal thoracic subarachnoid space, predominantly from T2 to T6. Patients present with symptoms like other causes of cord compression, and spinal MR studies should be evaluated routinely for the findings of SAWs. Further research could focus on understanding SAW prevalence, risk factors, and pathophysiology.

Dorsal arachnoid web: the ‘scalpel’ sign—a case report and differential diagnosis

Background

Arachnoid web of the spine is a not so common lesion of the spinal cord. It is a band-like arachnoid tissue in the intradural extramedullary compartment that extends to the surface of the spinal cord, with a tendency to occur in the upper dorsal spine causing focal dorsal indentation of the cord that has been coined the ‘scalpel sign’. Patients usually present with progressive weakening and numbing of bilateral lower limb.

Case presentation

A 58-year-old man presented with difficulty in walking and weakness of right leg for 1 year, aggravated over the previous 2 months. There was no history of trauma or fever. Magnetic resonance imaging (MRI) of the dorsal spine was done which revealed a small syrinx within the cord at D4 vertebral level on right side. There was sharp dorsal indentation of the spinal cord and widening of the arachnoid space below this level. This appearance was similar to a surgical scalpel. The anterior subarachnoid space was preserved. On post-contrast images, no parenchymal or meningeal enhancement was detected. The patient was taken up for surgery as the symptoms further progressed. Laminectomy was done from D3 to D7 under general anesthesia, with release of arachnoid web and adhesions. Histology of the resected specimen revealed epithelial cells and fibrous tissue. No inflammatory or neoplastic cells were observed.

Conclusions

Thoracic arachnoid web is a rare entity, which if not treated can have devastating effects on a patient’s neurological function. Careful evaluation of radiological findings is important to avoid delay in diagnosis. Surgery is the only curative treatment and is known to have a favorable outcome.

Dorsal arachnoid web: A rare cause of syringomyelia and myelopathy

Dorsal arachnoidal webs are condensations of arachnoidal tissue densely adherent to the pial surface of the posterior aspect of the dorsal spinal cord. Infrequently described in literature they disrupt the flow of CSF in the spinal subarachnoid space leading to syringomyelia and myelopathy. While there are several theories on their origin, the "scalpel sign" on magnetic resonance imaging is considered to be pathognomonic of this condition. An illustrative case of a 58 year old man with syringomyelia and dorsal cord indentation who presented with spastic paraparesis, gait instability, parasthesias and bilateral non radicular upper limb pain that resolved following excision of the web is described to highlight the importance of considering this diagnosis when cases of so called "idiopathic" syringomyelia are encountered.

Scalpel sign: Dorsal thoracic arachnoid web, thoracic arachnoid cyst and ventral cord herniation

The “Scalpel sign” is a radiological sign which can be identified on magnetic resonance imaging and indicates dorsal compression of the spinal cord [1]. Prior descriptions of a “Scalpel sign” have been reported in the literature and the awareness and identification of this pathognomonic sign may aid in the rapid diagnosis and treatment of patients with dorsal arachnoid web, dorsal arachnoid cyst or ventral cord herniation. We describe 3 cases which highlight these rare conditions for which this sign is pathognomonic and summarize the pertinent literature related to these disorders [1,2].

Thoracic spinal arachnoid web and syringomyelia with rostral expansion to the first cervical spinal cord level: Case report

INTRODUCTION AND IMPORTANCE

A spinal arachnoid web is a rare pathology that has been associated with the development of syringomyelia. Syrinx expansion can occur, which can result in the development of new symptoms. In the current literature, the farthest rostral expansion of the associated syrinx has been to the C3 spinal level.

CASE PRESENTATION

We present a 49-year-old Hispanic male with a thoracic spinal arachnoid web and an associated syrinx spanning from C1 to T7 spinal level. The patient developed upper extremities radicular symptoms that worsened over time. He underwent surgical management with T6-8 laminectomy and excision of the web. Postoperative follow-up evaluations demonstrated progressive clinical improvement with eventual resolution of symptoms and syringomyelia.

CLINICAL DISCUSSION

Syringomyelia secondary to a thoracic spinal arachnoid web is a progressive disease that can expand rostrally to the C1 spinal level. The clinical presentation usually involves the lower extremities. However, if the upper thoracic or cervical spinal cord is involved, patients can also present symptoms in the upper extremities. Management usually involves surgical excision of the web in order to decompress the subarachnoid space and restore the normal cerebrospinal fluid (CSF) flow.

CONCLUSION

Our case suggests that syringomyelia secondary to a spinal arachnoid web may continuously expand with concomitant worsening of symptoms. However, surgical resection is curative with possible remission of symptoms and normalization of spinal anatomy.

Atypical radiographic case of arachnoid web without scalpel sign

Background:

Spinal arachnoid webs (SAW) occur when abnormally thickened bands of arachnoid membranes commonly located dorsal to the thoracic spine cause blockage of normal cerebrospinal fluid (CSF) flow, resulting in focal cord compression and myelopathy. The pathognomonic MR finding for SAW is the “positive scalpel sign” comprised of an enlarged dorsal CSF space with a normal ventral subarachnoid space. The main differential diagnostic consideration for SAW is idiopathic spinal cord herniation (ISCH); however, for ISCH, MR studies classically demonstrate ventral displacement of the spinal cord through an anterior dural defect. Here, we describe a 60-year-old female with an atypical SAW at the T3-T4 level (i.e., the preoperative MR failed to demonstrate the “positive scalpel sign”). Nevertheless, at surgery, intraoperative ultrasonography confirmed that SAW was present and was decompressed/marsupialized/removed.

Case Description:

A 60-year-old female presented with sensory impairment to both lower extremities. The thoracic MR images showed an enlarged dorsal CSF space at the T3-T4 level but without the “scalpel sign” suggesting “interruption” of CSF flow by thickened bands of focal dorsal arachnoidal tissues. Although the initial preoperative diagnosis was ISCH, intraoperative ultrasound (IOUS) confirmed the presence of a thickened arachnoid band, confirming the diagnosis of a SAW that was appropriately decompressed/resected.

Conclusion:

Correctly, establishing the preoperative diagnosis of a SAW based on MR imaging may sometimes be difficult as the typical “scalpel sign” may not be present in all patients. Notably, in cases like this one, IOUS may critically confirm the diagnosis of SAW thus leading to appropriate SAW decompression/removal.

Review/Perspective On the Diagnosis and Surgical Management of Spinal Arachnoid Cysts

Background:

Spinal arachnoid cysts (SAC) are typically congenital, spontaneous, traumatic (i.e., including iatrogenic/surgical), or inflammatory in origin. In descending order, they occur in the thoracic, lumbar, and cervical spine, and originate from focal entrapment of the arachnoid membrane. Arachnoid cysts represent 1–2% of all cystic spinal masses/tumors. The majority are extradural arachnoid cysts (EDAC) while 10% of all arachnoid cysts are intradural (IDAC) including subarachnoid, or extra-arachnoidal/subdural. Only rarely are they intramedullary in location. The clinical symptoms/signs of IDAC/EDAC include; intracranial hypotension (i.e., due to continued cerebrospinal fluid drainage), radiculopathy, and/or myelopathy.

Methods:

Magnetic Resonance Images (MR) and Myelo-Computed Tomography (Myelo-CT) studies classically document the predominant dorsal location of IDAC/EDAC. They also show their extent and severity contributing to root, cord, and/or cauda equina compression. In the cervical/thoracic spine, MR/Myelo-CT studies classically show the “double cord” or “windsock” signs, while the “fake arachnoiditis sign” may be seen in the lumbar spine. The latter sign signals the presence of a circumferential extra-arachnoidal-subdural cyst that centrally “traps” the cauda equina. Note, that this resembles and is often misinterpreted as adhesive archnoiditis.

Results:

Patients with significant SAC-related neurological deficits typically warrant early surgery. That surgery includes; partial/total resection/fenestration of cyst walls, and occlusion of communicating fistulas with or without accompanying shunts.

Conclusion:

It is critical to recognize the clinical (i.e., intracranial hypotension, radiculopathy, and/or myelopathy) and radiographic MR/Myelo-CT signs (i.e., “double cord,” “windsock signs”, or “fake arachnoiditis sign”) of IDAC, EDAC, or intramedullary spinal arachnoid cysts to appropriately offer treatment. For those with significant neurological deficits, early surgery (i.e. optimally 0-< 24 hours after the onset of symptoms/signs consisting of laminectomies, partial/total cyst resection/fenestration, and ligation/occlusion of the subarachnoid-cyst fistula with or without shunt placement), is essential to avoid significant permanent neurological sequelae.

Clinical Characteristics, Outcomes, and Pathology Analysis in Patients With Dorsal Arachnoid Web

BACKGROUND

Dorsal arachnoid webs (DAWs) are rare pathological abnormalities of the arachnoid layer of the spinal cord that can result in pain and myelopathy.

OBJECTIVE

To present clinical, imaging, and pathological characteristics of patients diagnosed with DAW, case illustrations, and a review of the literature.

METHODS

Seventeen cases of DAW between 2015 and 2019 at a tertiary medical center were retrospectively identified through a case log search. Patient characteristics, preoperative imaging, operative notes, and pathology reports were collected. Our main outcome assessed was postoperative resolution of symptoms. Odds ratios were used to determine associations between preoperative signs and symptoms with postoperative symptom resolution.

RESULTS

The mean age of the cohort was 50.5 years (IQR = 16) and presented primarily with back pain (64.7%). On imaging, all patients were found to have the "scalpel sign," and nearly half had a syrinx present (41.2%). All DAWs were located in the thoracic spine, with the most common location being the midthoracic (70.6%). The mean follow-up length for all patients was 4.3 months. There were no preoperative symptoms significantly associated with postoperative symptom resolution; however, a trend was noted with the presence of a preoperative syrinx. Pathology samples consistently demonstrated fibroconnective or collagenous tissue with no evidence of inflammation or neoplasm.

CONCLUSION

DAW is a rare pathology that can result in myelopathy or inappropriate interventions if misdiagnosed. Surgical intervention using laminectomy with intradural exploration should be considered in symptomatic patients with DAW because it is curative with a strong chance of preoperative symptom resolution with relatively low complication rates.

Dorsal arachnoid web: A rare clinical entity

A dorsal arachnoid web is a rare entity involving abnormal formation of arachnoid mater into a dense web which may result in ventral herniation of the spinal cord and significant neurologic symptoms. Back pain or a compressive myelopathy are two of the most common presenting symptoms. CT myelogram or MRI can aid in the diagnosis of arachnoid web, and management of includes surgical and conservative approaches. Herein, we describe two interesting cases of arachnoid webs highlighting the diagnostic approach and differences in the approach to management of each case.

Spinal arachnoid web-a distinct entity of focal arachnopathy with favorable long-term outcome after surgical resection: analysis of a multicenter patient population

BACKGROUND CONTEXT

Spinal arachnoid web (SAW) is a rare condition characterized by focal thickening of the arachnoid membrane causing displacement and compression of the spinal cord with progressive symptoms and neurological deficits. Recent reports and clinical experience suggest that SAW is a distinct entity with specific radiological findings and treatment strategies distinguishable from other arachnopathies and potential differential diagnoses.

PURPOSE

To better define the diagnostic and clinical features, treatment options and outcomes of surgically treated SAW.

STUDY DESIGN

Multicentric retrospective cohort study.

PATIENT SAMPLE

Twelve cases of SAW surgically treated at three different centers.

OUTCOME MEASURES

Self-reported and neurological outcome measurements (pain, sensory-motor deficits, vegetative dysfunctions) were assessed at follow-up timepoints.

METHODS

Retrospective review of prospectively collected data on all patients surgically treated for SAW from three participating neurosurgical centers between 2014 and 2020. Clinicopathological data, including neurological presentation, radiological and histological findings and outcome data were analyzed.

RESULTS

Twelve radiologically and surgically confirmed cases of SAW were analyzed. Mean patient age was 54.7 [±12.7], 67% were male. All SAWs were located in the posterior thoracic dural sac. On magnetic resonance imaging (MRI), the "scalpel sign" - a characteristic focal dorsal indentation of the spinal cord resembling a scalpel blade - was identified in all patients. A focal intramedullary syrinx was present in 83%. Preoperative clinical symptoms included signs of myelopathy, pain, weakness and sensory loss, most commonly affecting the trunk/upper back or lower extremities. Laminectomy or laminoplasty with intradural excision of the SAW was the surgical treatment of choice in all cases. Intraoperative ultrasound was valuable to visualize the cerebrospinal fluid (CSF) flow obstruction, confirm the SAW location before dura incision and to control adequacy of resection. After surgery, sensory loss and weakness in particular showed significant improvement.

CONCLUSIONS

The present study comprises the largest series of surgically treated SAW, underscoring the unique clinical, radiographic, histopathological, and surgical findings. We want to emphasize SAW being a distinct entity of spinal arachnopathy with a favorable long-term outcome if diagnosed correctly and treated surgically. Intraoperative ultrasound aids visualizing the SAW before dural incision, as well as verifying restored CSF flow after resection.

Dorsal Arachnoid Web: A Rare Cause of Myelopathy

Teaching point: The scalpel sign is pathognomonic for a dorsal arachnoid web, a rare clinical-radiologic entity that can cause myelopathy.

Spinal Arachnoid Webs: Presentation, Natural History, and Outcomes in 38 Patients

BACKGROUND

Spinal arachnoid webs are rarely described bands of thickened arachnoid tissue in the dorsal thoracic spine. Much is unknown regarding their origins, risk factors, natural history, and outcomes.

OBJECTIVE

To present the single largest case series, detailing presenting symptoms and outcomes amongst operative and nonoperative patients, to better understand the role of intervention.

METHODS

This retrospective chart review identified 38 patients with arachnoid webs. Patient demographics, radiologic signs, symptoms, and surgical history data were extracted from the electronic medical record. Symptoms were divided by location and character. 28 patients were successfully contacted for follow up outcome surveys.

RESULTS

26 patients (68%) underwent surgical intervention, 12 (32%) were managed non-operatively. 15 (39%) patients had undergone a previous unsuccessful surgery at a different site for their symptoms prior to arachnoid web diagnosis. Commonly presenting symptoms included myelopathy (68%), focal thoracic back pain (68%), lower extremity weakness (45%), numbness and sensory changes (58%), and lower extremity radicular pain (42%), upper extremity weakness (24%), and radicular pain (37%). Focal thoracic pain was associated with thoracic level (P < .02). Myelopathic symptoms were less common in postoperative patients. Postoperative patients described significantly more upper extremity (P < .01) and thoracic (P < .01) numbness and paresthesias. Surveyed nonoperative patients universally described their symptoms as either stable or worsening.

CONCLUSION

Spinal arachnoid webs present with thoracic myelopathy and back pain but can also present with upper extremity symptoms. Surgical intervention stabilizes or improves symptoms and is well received. Nonoperative patients do not spontaneously improve.

Syringomyelia: diagnosis and management

In the pre-MR era syringomyelia often presented late, as a crippling neurological disorder. Today, most cases are diagnosed earlier, with less pronounced deficits. We are therefore presented with new challenges, including understanding the significance of various presenting symptoms, knowing when surgery might help and being aware of other treatments that could benefit someone living with the effects of syringomyelia, or its underlying cause.

Spinal Arachnoid Web: A didactic report of two cases with clinical, radiological, surgical and pathological correlations

BACKGROUND

Arachnoid web (AW) is a rare but probably underestimated cause of spinal cord injury that is complex to diagnose due to subtle MRI findings and similarities to other better-known diseases such as arachnoid cyst (AC) or transdural spinal cord herniation (TSCH). Increased recognition of AW is mandatory since delay in diagnosis can lead to potentially serious neurological sequelae.

CASE PRESENTATIONS

We report two additional cases of AW for didactic purposes, with special emphasis on the distinctive MRI and intraoperative findings. Both patients presented with progressively worsening neurological symptoms, including proprioceptive ataxia, motor weakness, numbness and neuropathic pain. The diagnosis of AW was suspected on the basis of specific MRI criteria, especially the so-called "scalpel sign". Formal confirmation of the diagnosis was obtained in two patients that were managed surgically. Postoperative follow-up demonstrated significant functional recovery.

DISCUSSION

There is a need for better recognition of AW by the medical community. Careful analysis of MRI semiology is crucial for the distinction between AW, AC and TSCH. Prompt and accurate diagnosis is mandatory to conserve functional prognosis, since appropriate surgical treatment with AW resection is curative, halting or even resolving the neurological symptoms.

Thoracic dorsal arachnoid web with rapid onset of symptoms: A report of two cases and brief review of the literature

Background:

Thoracic arachnoid webs are a rare entity and can be challenging to diagnose with sometimes subtle radiographic findings. Arachnoid webs can cause severe cord compression with associated syrinx and resulting myelopathy, weakness, sensory loss, and bowel/bladder dysfunction. There have been a little over 60 cases total reported in the literature with only one systematic review. The cases presented here have unique features including rapid onset of symptoms, symptomatic syrinx extending into the cervical spine, and intraoperative syrinx drainage, all of which are quite rare in the current published literature for arachnoid webs.

Case Description:

Here, we present two patients, a 73-year-old man and 58-year-old man presenting with different symptoms and timing of symptom progression but both with “scalpel sign” and associated syrinx present on their MRIs. Each patient underwent a laminectomy with resection of arachnoid web with complete resolution of symptoms in the first case and significant improvement in the second case. Postoperative imaging in both cases showed almost complete resolution of the syrinx.

Conclusion:

Early clinical evaluation and workup followed by early surgical treatment can lead to dramatic improvement in outcomes after surgery. For patients that are symptomatic from an associated syrinx, a midline myelotomy to facilitate drainage can be considered to be done concomitantly with the arachnoid web resection.

Neuroimaging findings and pathophysiology of dorsal spinal arachnoid webs: illustrative case

BACKGROUND

Spinal arachnoid webs are uncommon and difficult to diagnose, especially because causative intradural transverse bands of arachnoid tissue are radiographically occult. Left untreated, arachnoid webs may cause progressive, debilitating, and permanent neurological dysfunction. Conversely, more than 90% of patients may experience rapid neurological recovery after resection, even with a prolonged duration of presenting symptoms. Indirect imaging signs such as spinal cord indentation and compression with cerebrospinal fluid (CSF) flow alteration provide crucial diagnostic clues that are critical in guiding appropriate management of such patients.

OBSERVATIONS

The authors reported a patient with no significant medical history who presented with back pain, progressive lower extremity weakness, gait ataxia, and bowel and bladder incontinence. They discussed multimodality imaging for determining the presence of arachnoid webs, including magnetic resonance imaging, phase-contrast CSF flow study, computed tomography myelography, and intraoperative ultrasound. They also discussed the detailed anatomy of the spinal subarachnoid space and a plausible pathophysiological mechanism for dorsal arachnoid webs.

LESSONS

The authors report on a patient who underwent comprehensive imaging evaluation detailing the arachnoid web and whose subsequent anatomical localization and surgical treatment resulted in a full neurological recovery.

Multi-modality imaging evaluation of the dorsal arachnoid web

PURPOSE

Dorsal arachnoid web (DAW) is a rare intradural abnormality which is associated with progressive myelopathy. Our objective was to review multi-modality imaging techniques demonstrating the scalpel sign appearance in evaluation of DAW.

METHODS

We retrospectively reviewed various imaging modalities of patients found to have DAW at our institution during January 2015 to February 2020. Five patients underwent surgical decompression with pathological correlation. The remaining patients were presumptively diagnosed based on the characteristic finding of scalpel sign. Clinical data were evaluated and correlated to imaging findings. All imaging modalities demonstrated the characteristic scalpel sign.

RESULTS

Sixteen patients (10 females, and six males) with multi-imaging modalities were evaluated. Their mean age was 52 year (range 23-74 years). Fifteen patients underwent conventional spine MRI. Further high-resolution MR imaging techniques, e.g. 3D T2 myelographic sequence, were utilized with two patients. MRI spine CSF flow study was performed to evaluate the flow dynamic across the arachnoid web in one patient. Eight patients were evaluated with CT myelogram. Syrinx formation was discovered in seven (44%) patients; five (71%) of them underwent surgical resection and decompression. Two patients underwent successful catheter-directed fenestration of the web with clinical improvement. We found a statically significant positive correlation between the degree of cord displacement and compression with syrinx formation (r = 0.55 and 0.65 with p-value of 0.03 and 0.009, respectively).

CONCLUSION

DAW has characteristic scalpel sign independent of imaging modality. Multi-modality imaging evaluation of DAW is helpful for evaluation and surgical planning.

Spinal subarachnoid diverticula in dogs: A review

Spinal subarachnoid diverticula are fluid dilations of the subarachnoid space that can cause a compressive myelopathy in dogs. These diverticula are usually associated with high motion areas in the cervical and caudal thoracic spine. The definitive etiopathogenesis has not been determined but likely involves congenital or acquired causes. Pugs, French bulldogs, and Rottweilers are overrepresented breeds. Clinical signs typically include ataxia, paresis, and upper motor neuron urinary and/or fecal incontinence; pain is a less common feature. Diagnosis is based on advanced imaging, with magnetic resonance imaging now being favored given the additional detail of the spinal cord parenchyma that can be obtained. Outcomes are better with surgical intervention than with medical therapies, though there is a lack of long-term data. No superior surgical technique has been identified, and questions remain on the significance of addressing leptomeningeal adhesions at the time of surgery. Clinical signs can recur, though not always due to recurrence of diverticulum formation, and pugs may be less likely to have a successful long-term outcome.

Diagnosis and Surgical Treatment of Thoracic Dorsal Arachnoid Web: A Report of Two Cases

Introduction

An arachnoid web (AW) is a relatively rare disease and shows clinical symptoms and radiological findings similar to those of an arachnoid cyst (AC) or spinal cord herniation (SCH). Since the operative procedures for an AW are generally different from those intrathecal disorders, correct preoperative differential diagnosis is important. The purposes of this study were to report the usefulness of magnetic resonance imaging (MRI) and computed tomography (CT) myelography for diagnosing AW and to show the histological findings and clinical results. Case Description. Two patients, a 79-year-old man and a 43-year-old woman, are presented. The primary diagnoses were AC with ossification of the ligamentum flavum and epidural hematoma, respectively, in previous hospitals. They were finally diagnosed by the characteristic MRI and CT myelogram finding called the “scalpel sign.” Histological findings showed epithelial cells and fibrous tissue derived from arachnoid tissues and microcalcifications. After surgery, the scalpel sign has vanished, and aggravation of their symptoms was prevented.

Conclusion

An AW is refractory, but early detection by MRI and CT myelography and early treatment improve outcomes after surgery.

Percutaneous Fenestration of a Spinal Arachnoid Web Using an Intrathecal Catheter: Effect on Cerebrospinal Fluid Flow and Clinical Status

Background

Spinal arachnoid webs are a rare anatomic entity manifesting as neuropathic back pain, compressive myelopathy, radiculopathy, and hydrocephalus. Typical treatments include hemilaminectomy or full laminectomy with durotomy and microsurgical resection, which can result in secondary scarring and recurrent blockage of cerebrospinal fluid (CSF) flow perpetuating the cycle.

Case Description

A 66-year-old woman presented with progressively worsening gait and memory. Magnetic resonance imaging demonstrated an arachnoid web in the high thoracic region, causing CSF flow obstruction and hydrocephalus. A standard lumbar drainage catheter was introduced percutaneously into the lumbar thecal sac and advanced in a cephalad direction, across the arachnoid web, to the high thoracic region. The patient underwent continuous CSF drainage through this catheter for a total of 3 days, displaying measurable clinical improvement that persisted at the 3-month follow-up visit. Phase-contrast magnetic resonance imaging demonstrated interval reconstitution of dorsal synchronous CSF flow at the second thoracic vertebral level, both on day 3 and at the 3-month control imaging study.

Conclusions

This minimally invasive approach seems useful in achieving restoration of spinal fluid flow at the thoracic region when the underlying blockage results from an arachnoid web and leads to quantifiable clinical improvement.

Arachnoid web of the spine: a systematic literature review

OBJECTIVE

An arachnoid web of the spine (AWS) is a rare and oftentimes challenging lesion to diagnose, given its subtle radiographic findings. However, when left untreated, this lesion can have devastating effects on a patient's neurological function. To date, only limited case reports and series have been published on this topic. In this study, the authors sought to better describe this lesion, performing a systematic literature review and including 2 cases from their institution's experience.

METHODS

A systematic literature search was performed in September 2018 that queried Ovid MEDLINE (1946-2018), PubMed (1946-2018), Wiley Cochrane Library: Central Register of Controlled Trials (1898-2018), and Thompson Reuters Web of Science: Citation Index (1900-2018), per PRISMA guidelines. Inclusion criteria specified all studies and case reports of patients with an AWS in which any relevant surgery types were considered and applied. Studies on arachnoid cysts and nonhuman populations, and those that did not report patient treatments or outcomes were excluded from the focus review.

RESULTS

A total of 19 records and 2 patients treated by the senior authors were included in the systematic review, providing a total of 43 patients with AWS. The mean age was 52 years (range 28-77 years), and the majority of patients were male (72%, 31/43). A syrinx was present in 67% (29/43) of the cases. All AWSs were located in the thoracic spine, and all but 2 (95%) were located dorsally (1 ventrally and 1 circumferentially). Weakness was the most frequently reported symptom (67%, 29/43), followed by numbness and/or sensory loss (65%, 28/43). Symptoms predominated in the lower extremities (81%, 35/43). It was found that nearly half (47%, 20/43) of patients had been experiencing symptoms for 1 year or longer before surgical intervention was performed, and 35% (15/43) of reports stated that symptoms were progressive in nature. The most commonly used surgical technique was a laminectomy with intradural excision of the arachnoid web (86%, 36/42). Following surgery, 91% (39/43) of patients had reported improvement in their neurological symptoms. The mean follow-up was 9.2 months (range 0-51 months).

CONCLUSIONS

AWS of the spine can be a debilitating disease of the spine with no more than an indentation of the spinal cord found on advanced imaging studies. The authors found this lesion to be reported in twice as many males than females, to be associated with a syrinx more than two-thirds of the time, and to only have been reported in the thoracic spine; over 90% of patients experienced improvement in their neurological function following surgery.