The Neuroimaging Spectrum of Septum Posticum Derangement and Associated Thoracic Myelopathy

Description and clinical relevance of the variable conformation of canine spinal arachnoid diverticula

The conformation of spinal arachnoid diverticula (SAD) and their clinical implications are poorly characterized in dogs. This retrospective cross-sectional study describes different SAD conformations in dogs and aims to identify if there is an association between SAD conformation and clinical features, localization, syringomyelia (SM) presence, concurrent vertebral condition, treatment option, and short as well as long-term outcome. Sixty-two dogs were included (12 cervical and 50 thoracolumbar SAD). All dogs with a cervical SAD had a cranial tethered conformation and were not included in the statistical analysis. Half of the dogs with a thoracolumbar SAD were cranial tethered, and the other half were caudal tethered. SM associated with SAD had a moderate prevalence in the cervical region (58.3%) and a high prevalence in the thoracolumbar region (82%). All dogs with the presence of SM and caudal tethered SAD had a cranial positioned SM, and all dogs with SM and a cranial tethered SAD had a caudal positioned SM. The SM absolute length and SM length/L2 ratio were significantly higher (P = .018, respectively) in the caudal tethered SAD compared with the cranial tethered SAD. The short-term outcome was statistically different (P = .045) between caudal and cranial tethered thoracolumbar SAD, but not the long-term outcome (P = .062). Multivariable logistic regression identified thoracolumbar caudal tethered SAD conformation had a better short-term outcome (P = 0.017, OR: 0.043, CI: 0.003-0.563), independently of SM length measurements. SAD conformation in dogs can influence SM formation. A possible link between short-term outcome and SAD conformation was found, but further research is warranted.

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.

Early microsurgery on thoracolumbar spinal extradural arachnoid cysts: Analysis of a series of 41 patients

BACKGROUND

We designed this study to share our management experiences on spinal extradural arachnoid cysts (SEACs) to add more to the body of evidence for their treatment.

METHODS

We retrospectively reviewed 41 patients who underwent microsurgery for thoracolumbar SEACs at our hospital from June 2009 to June 2019. All clinical data, including medical history, clinical features, imaging manifestation, operative findings, and prognosis, were extracted from medical records and databases. Perioperative differences of the Visual Analogue Scale (VAS), the Oswestry disability index (ODI) score, and postoperative Odom's criteria were used to assess the surgical outcome.

RESULTS

The most common and very first clinical symptom in the 41 patients was pain (VAS = 2.82 ± 0.89), and the mean ODI value was 61.7 ± 8.9%. Imaging revealed that the cystic lesions in the thoracolumbar spine involved an average of 2.85 segments. Of the 41 patients, 39 underwent total cyst excisions, and 36 had their dural defect repaired by one of three methods. The mean postoperative follow-up time was 52.3 months. Postoperatively, one case developed kyphoscoliosis and two cases experienced a recurrence. The majority of patients showed excellent outcomes according to Odom's criteria, the postoperative VAS (0.80 ± 1.08), and the ODI (15.4 ± 9.3%).

CONCLUSIONS

Themost commonclinicalsymptoms of thoracolumbar SEACs included progressive discomfort and pain around the involved spinal segments. Early surgical intervention relieved the patients from their symptoms. Microsurgery was recommended to resect the complete cyst and to repair the dural defect, but resection of the complete cyst is more necessary than just repairment of the dural defect for providing promising outcomes.

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.

Clinical features and MRI characteristics of presumptive constrictive myelopathy in 27 pugs

Constrictive myelopathy has been described in pugs with paraparesis and is characterized by fibrous connective and granulation tissue within the dura mater causing spinal cord compression and focal gliosis. An association between constrictive myelopathy and caudal articular process (CAP) dysplasia is suspected; however, some studies have reported CAP dysplasia as an incidental finding. The imaging appearance of constrictive myelopathy is currently limited to a small number of cases. The aim of this multicenter, retrospective, descriptive study was to detail the magnetic resonance imaging (MRI) characteristics and to correlate these with clinical signs of presumptive constrictive myelopathy in pugs. Medical databases from five veterinary referral hospitals were reviewed to identify pugs with pelvic limb ataxia and paresis, that had a complete record of signalment, neurological examination, and MRI of the thoracolumbar spinal cord. The exclusion criteria were pugs with other conditions, such as unequivocal subarachnoid diverticula, hemivertebrae causing vertebral canal stenosis, intervertebral disc extrusions/protrusions, and multifocal/diffuse lesions. Twenty-seven pugs met the inclusion criteria. All cases were ambulatory with paraparesis and ataxia. Nearly 60% were incontinent. Magnetic resonance imaging revealed a focal myelopathy in all cases showing one or more of the following lesions: CAP dysplasia (25/27), focal subarachnoid space irregular margination (26/27) with circumferential or dorsal contrast enhancement (10/12), and a symmetric V-shaped ventral extradural lesion (23/27). This study describes specific MRI features of pugs with presumptive constrictive myelopathy, which authors hypothesize to be a consequence of chronic micro-motion. Our results may help in diagnosing and subsequently treating this condition, which may warrant vertebral stabilization.

Anatomy of the human spinal cord arachnoid cisterns: applications for spinal cord surgery

OBJECTIVE

The goal in this study was to describe the overall organization of the spinal arachnoid mater and spinal subarachnoid space (SSAS) as well as its relationship with surrounding structures, in order to highlight spinal cord arachnoid cisterns.

METHODS

Fifteen spinal cords were extracted from embalmed adult cadavers. The organization of the spinal cord arachnoid and SSAS was described via macroscopic observations, optical microscopic views, and scanning electron microscope (SEM) studies. Gelatin injections were also performed to study separated dorsal subarachnoid compartments.

RESULTS

Compartmentalization of SSAS was studied on 3 levels of axial sections. On an axial section passing through the tips of the denticulate ligament anchored to the dura, 3 subarachnoid cisterns were observed: 2 dorsolateral and 1 ventral. On an axial section passing through dural exit/entrance of rootlets, 5 subarachnoid cisterns were observed: 2 dorsolateral, 2 lateral formed by dorsal and ventral rootlets, and 1 ventral. On an axial section passing between the two previous ones, only 1 subarachnoid cistern was observed around the spinal cord. This compartmentalization resulted in the anatomical description of 3 elements: the median dorsal septum, the arachnoid anchorage to the tip of the denticulate ligament, and the arachnoid anchorage to the dural exit/entrance of rootlets. The median dorsal septum already separated dorsal left and right subarachnoid spaces and was described from C1 level to 3 cm above the conus medullaris. This septum was anchored to the dorsal septal vein. No discontinuation was observed in the median dorsal arachnoid septum. At the entrance point of dorsal rootlets in the spinal cord, arachnoid trabeculations were described. Using the SEM, numerous arachnoid adhesions between the ventral surface of the dorsal rootlets and the pia mater over the spinal cord were observed. At the ventral part of the SSAS, no septum was found, but some arachnoid trabeculations between the arachnoid and the pia mater were present and more frequent than in the dorsal part. Laterally, arachnoid was firmly anchored to the denticulate ligaments' fixation at dural points, and dural exit/entrance of rootlets made a fibrous ring of arachnoidodural adhesions. At the level of the cauda equina, the arachnoid mater surrounded all rootlets together-as a sac and not individually.

CONCLUSIONS

Arachnoid cisterns are organized on each side of a median dorsal septum and compartmentalized in relation with the attachments of denticulate ligament and exit/entrance of rootlets.

Symptomatic extradural spinal arachnoid cyst: More than a simple herniated sac

Introduction and Study Design:

Spinal arachnoid cyst is an uncommon entity, presenting with radiculopathy or paraparesis. These cysts are usually found in intradural extramedullary region; and the extradural region is a rare location. The exact pathogenesis in the existence of these cysts in the extradural region is still debated. In this article, we have retrospectively analyzed the clinical profile of the rare extradural arachnoid cyst (EDAC).

Methodology:

In this study, 19 patients of EDAC operated at our institute between January 2006 to June 2016 are analyzed. All patients with the Oswestry disability index score of >20 were managed surgically (open laminectomy and cyst excision). The clinical outcome was assessed at using 5-point satisfaction scale and McCormick grading.

Results:

All 13 operated patients had EDACs with communication with the intradural compartment. In 11 (84.6%) patients, cyst wall was excised completely, in 2 (15.3%) patients underwent partial excision of cyst wall; dural communication was closed in all patients (n = 13). None of the patients had clinical deterioration or radiological recurrence till the last follow-up. Mean follow-up was 52.2 months (range 1–160); all patients were satisfied after surgery (median score was 3).

Discussion:

Symptomatic EDACs account <2% of all spinal tumors. The EDACs have communication with the intradural compartment. In our article, we have discussed the approach and management of EDAC, including minimally invasive percutaneous procedures.

Conclusion:

One should aim for preoperative or intraoperative localization of dural communication and try to disconnect the extradural cyst from the intradural connection to prevent recurrence. Surgical treatment is complete excision of the cyst.

Clinical Outcomes of Surgical Treatment for Arachnoid Web: A Case Series

Introduction

We describe 5 patients who underwent operative treatment for arachnoid web (AW) and discuss the postoperative clinical outcome in each case. AW is an extremely rare disease that causes cord compression and syringomyelia in the thoracic spine. To date, 14 cases only of AW have been reported, and the effect of surgical intervention on clinical and radiologic outcomes is unknown.

Methods

Five patients who underwent surgical treatment for AW were retrospectively reviewed. The clinical outcomes were evaluated using the thoracic Japanese Orthopaedic Association (T-JOA) score. Preoperative and postoperative images were reviewed.

Results

All the patients presented with spastic gait and numbness in the lower extremities. Two patients also presented with bladder-bowel dysfunction (BBD). AW, or the so-called “scalpel” sign, was seen dorsally in the thoracic spine on magnetic resonance imaging in all the patients. Syringomyelia adjacent to the web was observed in 4 patients. Fenestration and web resection without instrumentation was performed in all the cases. Overall, significant improvement was seen in locomotion and the total T-JOA score postoperatively. However, numbness in the lower extremities improved in 2 patients but was unchanged in 3 cases. BBD was ameliorated in 1 patient but remained unchanged in the other patient.

Conclusions

Our experience suggests that surgical treatment, including the another patient and resection of the web, can correct the flow dynamics of cerebrospinal fluid and allow neurologic recovery, in particular locomotion, in patients with AW.

Pathophysiology and Grading of the Ventral Displacement of Dorsal Spinal Cord Spectrum

Study Design

A retrospective study of the ventral displacement of dorsal spinal cord (VDDSC) spectrum pathophysiology and grading.

Purpose

This study aimed at examining the pathophysiology of VDDSC between D3 and D7, using magnetic resonance imaging (MRI) correlation and severity grading.

Overview of Literature

The pathologies that lead to VDDSC were previously discussed in various articles. We attempted to group these pathological conditions under a single spectrum, and grade them according to their severity.

Methods

We reviewed the MRI images of the dorsal spines of 1,350 patients over a period of 4 years (February 2013–February 2017); all MRI images were analyzed by two experienced radiologists.

Results

Of the 1,350 patients, 28 exhibited VDDSC between D3 and D7. Additional findings included ventral transdural herniation of the spinal cord (n=10), anterior spinal cord adhesion (n=7), arachnoid web (n=6), and arachnoid cyst (n=5).

Conclusions

We grouped the pathologies that lead to VDDSC at the thoracic level into a single spectrum of varying severity and graded VDDSC, from mild to severe.

Spinal dura mater: biophysical characteristics relevant to medical device development

Understanding the relevant biophysical properties of the spinal dura mater is essential to the design of medical devices that will directly interact with this membrane or influence the contents of the intradural space. We searched the literature and reviewed the pertinent characteristics for the design, construction, testing, and imaging of novel devices intended to perforate, integrate, adhere or reside within or outside of the spinal dura mater. The spinal dura mater is a thin tubular membrane composed of collagen and elastin fibres that varies in circumference along its length. Its mechanical properties have been well-described, with the longitudinal tensile strength exceeding the transverse strength. Data on the bioelectric, biomagnetic, optical and thermal characteristics of the spinal dura are limited and sometimes taken to be similar to those of water. While various modalities are available to visualise the spinal dura, magnetic resonance remains the best modality to segment its structure. The reaction of the spinal dura to imposition of a foreign body or other manipulations of it may compromise its biomechanical and immune-protective benefits. Therefore, dural sealants and replacements are of particular clinical, research and commercial interest. In conclusion, existing devices that are in clinical use for spinal cord stimulation, intrathecal access or intradural implantation largely adhere to traditional designs and their attendant limitations. However, if future devices are built with an understanding of the dura's properties incorporated more fully into the designs, there is potential for improved performance.

Differentiation of idiopathic spinal cord herniation from dorsal arachnoid webs on MRI and CT myelography

OBJECTIVE

Dorsal arachnoid webs (DAWs) and spinal cord herniation (SCH) are uncommon abnormalities affecting the thoracic spinal cord that can result in syringomyelia and significant neurological morbidity if left untreated. Differentiating these 2 entities on the basis of clinical presentation and radiological findings remains challenging but is of vital importance in planning a surgical approach. The authors examined the differences between DAWs and idiopathic SCH on MRI and CT myelography to improve diagnostic confidence prior to surgery.

METHODS

Review of the picture archiving and communication system (PACS) database between 2005 and 2015 identified 6 patients with DAW and 5 with SCH. Clinical data including demographic information, presenting symptoms and neurological signs, and surgical reports were collected from the electronic medical records. Ten of the 11 patients underwent MRI. CT myelography was performed in 3 patients with DAW and in 1 patient with SCH. Imaging studies were analyzed by 2 board-certified neuroradiologists for the following features: 1) location of the deformity; 2) presence or absence of cord signal abnormality or syringomyelia; 3) visible arachnoid web; 4) presence of a dural defect; 5) nature of dorsal cord indentation (abrupt “scalpel sign” vs “C”-shaped); 6) focal ventral cord kink; 7) presence of the nuclear trail sign (endplate irregularity, sclerosis, and/or disc-space calcification that could suggest a migratory path of a herniated disc); and 8) visualization of a complete plane of CSF ventral to the deformity.

RESULTS

The scalpel sign was positive in all patients with DAW. The dorsal indentation was C-shaped in 5 of 6 patients with SCH. The ventral subarachnoid space was preserved in all patients with DAW and interrupted in cases of SCH. In no patient was a web or a dural defect identified.

CONCLUSIONS

DAW and SCH can be reliably distinguished on imaging by scrutinizing the nature of the dorsal indentation and the integrity of the ventral subarachnoid space at the level of the cord deformity.