Buckling of the Ligamentum Flavum in Patients with Lumbar Spinal Canal Stenosis.

STUDY DESIGN: Experimental study. OBJECTIVE: We sought to elucidate the association between ligamentum flavum thickening and tissue buckling, and the clinical and imaging factors related to buckling by comparing the ligamentum flavum thickness on MRI images and within the actual tissue. SUMMARY OF BACKGROUND DATA: Ligamentum flavum thickening is a main contributor to lumbar spinal canal stenosis. Buckling of the tissue may contribute to ligamentum flavum thickening along with tissue hypertrophy; however, this association has not been established conclusively. MATERIALS AND METHODS: Ligamentum flavum samples (135 ligament samples) from 70 patients with lumbar spinal canal stenosis were evaluated. The ligamentum flavum thicknesses on magnetic resonance imaging (MRI) and in the tissue samples were compared to assess for the presence of buckling. The ligamentum flavum samples were divided into groups with or without buckling based on the difference between their thicknesses on MRI and in the tissues. The Pearson correlation coefficient test was used to assess the relationships between the LF thicknesses on MRI and in the tissues, MRI-tissue difference and LF thickness in the tissues, and MRI-tissue difference and LF thickness on MRI. Further, differences between the buckling+ and buckling- groups were compared using the unpaired t-test (LF thickness on MRI, LF thickness in the tissues, age, disc angle, and disc height) and χ2 (disc level, disc degeneration, and receival/nonreceival of dialysis) test. RESULTS: The ligamentum flavum thickness on MRI and in the tissues had a positive linear relationship, although the thickness was estimated to be significantly larger on MRI than in the tissues themselves. The ligamentum flavum with buckling had a larger thickness on MRI, less tissue hypertrophy, more severe disc degeneration, and was present in patients with a higher rate of dialysis. There were no differences in age and disc height, angle, or level between the two groups. CONCLUSIONS: Buckling of the ligamentum flavum coexists with tissue hypertrophy and contributes to perceived ligamentum thickening on imaging. Buckling of the ligamentum flavum tends to occur in less hypertrophied tissues and is associated with the grade of disc degeneration and the presence of other characteristics associated with spinal degeneration.

First incidence of extrarenal wilms tumor within the spinal canal in the adult population: a novel case report and literature review.

BACKGROUND: Wilms tumor (WT), also known as nephroblastoma, is rare in adults, accounting for merely 3% of all nephroblastomas or 0.2 cases per million individuals. Extrarenal Wilms tumor (ERWT) emerges outside the renal boundaries and comprises 0.5 to 1% of all WT cases, with even rarer incidences in adults. Oncogenic mutations associated with ectopic nephrogenic rests (NR) may contribute to ERWT development. Diagnosis involves surgical resection and pathology examination. Due to scarce cases, adults often rely on pediatric guidelines. We thoroughly searched PubMed, Scopus, and Web of Science databases to establish our case's uniqueness. To the best of our knowledge, this is the first documented incidence of extrarenal Wilms tumor within the spinal canal in the adult population. CASE PRESENTATION: A 22-year-old woman with a history of congenital lipo-myelomeningocele surgery as an infant presented with a 6-month history of back pain. This pain gradually resulted in limb weakness, paraparesis, and loss of bladder and bowel control. An MRI showed a 6 × 5 × 3 cm spinal canal mass at the L4-S1 level. Consequently, a laminectomy was performed at the L4-L5 level to remove the intramedullary tumor. Post-surgery histopathology and immunohistochemistry confirmed the tumor as ERWT with favorable histology without any teratomatous component. CONCLUSION: This report underscores the rarity of extrarenal Wilms tumor (ERWT) in adults, challenging conventional assumptions about its typical age of occurrence. It emphasizes the importance of clinical awareness regarding such uncommon cases. Moreover, the co-occurrence of spinal ERWTs and a history of spinal anomalies warrants further investigation.

Three-dimensional Spinal Canal Morphometric Analysis and Relevant Spinal Cord Occupational Ratios in Congenital Cervical Spinal Stenosis: A Classification Algorithm of the Stenosis Phenotypes and Data-driven Decompression Approach.

OBJECTIVES: No standardized magnetic resonance imaging (MRI) parameters have defined the 3-dimensional morphoanatomy and relevant spinal cord occupation ratios (occupation of spinal cord dimensions/similar dimensions within the spinal canal) in congenital cervical stenosis (CCS). METHODS: A retrospective, comparative analysis was conducted on 200 patients >18 years of age with myelopathy and CCS (mean age, 52.4 years) and 200 age-matched controls with no myelopathy or radiculopathy. The variables assessed from high resolution MRI included sagittal and axial spinal canal dimensions (MRI Torg-Pavlov ratios) from C3 to C7. Morphometric dimensions from the sagittal retrodiscal and retrovertebral regions as well as axial MRI dimensions were compared. Sagittal and axial spinal cord occupation ratios were defined and correlated with spinal canal dimensions. RESULTS: Multivariate analyses indicated reduced sagittal and axial anteroposterior (AP) spinal canal dimensions and a large reduction in transverse spinal canal dimensions at all spinal levels. There was a small significant correlation between AP sagittal spinal canal dimensions and axial transverse spinal canal dimensions at C3-C5, but not at C5-C6. Small correlations were noted between AP sagittal spinal canal dimensions and AP axial spinal cord and axial cross-sectional area occupation ratios at C3-C6, but there was no correlation with axial mediolateral spinal cord occupation ratios. CONCLUSIONS: The stenosis effect can involve any dimension, including the transverse spinal canal dimension, independent of other dimensions. Owing to the varied observed morphoanatomies, a classification algorithm that defines CCS specific phenotypes was formulated. Objectivizing the stenosis morphoanatomy may allow for data-driven patient-focused decompression approaches in the future.

Deep learning-based spinal canal segmentation of computed tomography image for disease diagnosis: A proposed system for spinal stenosis diagnosis.

BACKGROUND: Lumbar disc herniation was regarded as an age-related degenerative disease. Nevertheless, emerging reports highlight a discernible shift, illustrating the prevalence of these conditions among younger individuals. METHODS: This study introduces a novel deep learning methodology tailored for spinal canal segmentation and disease diagnosis, emphasizing image processing techniques that delve into essential image attributes such as gray levels, texture, and statistical structures to refine segmentation accuracy. RESULTS: Analysis reveals a progressive increase in the size of vertebrae and intervertebral discs from the cervical to lumbar regions. Vertebrae, bearing weight and safeguarding the spinal cord and nerves, are interconnected by intervertebral discs, resilient structures that counteract spinal pressure. Experimental findings demonstrate a lack of pronounced anteroposterior bending during flexion and extension, maintaining displacement and rotation angles consistently approximating zero. This consistency maintains uniform anterior and posterior vertebrae heights, coupled with parallel intervertebral disc heights, aligning with theoretical expectations. CONCLUSIONS: Accuracy assessment employs 2 methods: IoU and Dice, and the average accuracy of IoU is 88% and that of Dice is 96.4%. The proposed deep learning-based system showcases promising results in spinal canal segmentation, laying a foundation for precise stenosis diagnosis in computed tomography images. This contributes significantly to advancements in spinal pathology understanding and treatment.

Dural Sac Cross-sectional area change from preoperatively and up to 2 years after decompressive surgery for central lumbar spinal stenosis: investigation of operated levels, data from the NORDSTEN study.

PURPOSE: The aim of the present study was to investigate how canal area size changed from before surgery and up to 2 years after decompressive lumbar surgery lumbar spinal stenosis. Further, to investigate if an area change postoperatively (between 3 months to 2 years) was associated with any preoperative demographic, clinical or MRI variables or surgical method used. METHODS: The present study is analysis of data from the NORDSTEN- SST trial where 437 patients were randomized to one of three mini-invasive surgical methods for lumbar spinal stenosis. The patients underwent MRI examination of the lumbar spine before surgery, and 3 and 24 months after surgery. For all operated segments the dural sac cross-sectional area (DSCA) was measured in mm2. Baseline factors collected included age, gender, BMI and smoking habits. Furthermore, surgical method, index level, number of levels operated, all levels operated on and baseline Schizas grade were also included in the analysis. RESULTS: 437 patients were enrolled in the NORDSTEN-SST trial, whereof 310 (71%) had MRI at 3 months and 2 years. Mean DSCA at index level was 52.0 mm2 (SD 21.2) at baseline, at 3 months it increased to 117.2 mm2 (SD 43.0) and after 2 years the area was 127.7 mm2 (SD 52.5). Surgical method, level operated on or Schizas did not influence change in DSCA from 3 to 24 months follow-up. CONCLUSION: The spinal canal area after lumbar decompressive surgery for lumbar spinal stenosis increased from baseline to 3 months after surgery and remained thereafter unchanged 2 years postoperatively.

Imaging of Adult Malignant Soft Tissue Tumors of the Spinal Canal: A Guide for Spine Surgeons.

BACKGROUND: Malignant soft tissue spinal canal tumors compromise 20% of all spinal neoplasms. They may be primary or metastatic lesions, originating from a diverse range of tissues within and surrounding the spinal canal. These masses can present as diverse emergencies such as secondary cauda equina syndrome, vascular compromise, or syringomyelia. Interpretation of malignant soft tissue spinal canal tumors imaging is an essential for non-radiologists in the setting of emergencies. This task is intricate due to a great radiologic pattern overlap among entities. METHODS: We present a step-by-step strategy that can guide nonradiologists identify a likely malignant soft tissue lesion in the spinal canal based on imaging features, as well as a review of the radiologic features of malignant soft tissue spinal canal tumors. RESULTS: Diagnosis of soft tissue spinal canal malignancies starts with the identification of the lesion's spinal level and its relationship to the dura and medulla. The second step consists of characterizing it as likely-malignant based on radiological signs like a larger size, ill-defined margins, central necrosis, and/or increased vascularity. The third step is to identify additional imaging features such as intratumoral hemorrhage or cyst formation that can suggest specific malignancies. The physician can then formulate a differential diagnosis. The most encountered malignant soft tissue tumors of the spinal canal are anaplastic ependymomas, anaplastic astrocytomas, metastatic tumors, lymphoma, peripheral nerve sheath tumors, and central nervous system melanomas. A review of the imaging features of every type/subtype of lesion is presented in this work. Although magnetic resonance imaging remains the modality of choice for spinal tumor assessment, other techniques such as dynamic contrast agent-enhanced perfusion magnetic resonance imaging or diffusion-weighted imaging could guide diagnosis in specific situations. CONCLUSIONS: In this review, diagnostic strategies for several spinal cord tumors were presented, including anaplastic ependymoma, metastatic spinal cord tumors, anaplastic and malignant astrocytoma, lymphoma, malignant peripheral nerve sheath tumors , and primary central nervous system melanoma. Although the characterization of spinal cord tumors can be challenging, comprehensive knowledge of imaging features can help overcome these challenges and ensure optimal management of spinal canal lesions.

Radiological Analysis of Cerebrospinal Fluid Dynamics at the Craniovertebral Junction Using Time-Spatial Labeling Inversion Pulse Magnetic Resonance Imaging in Patients with Cervical Spinal Canal Stenosis.

OBJECTIVE: Spondylotic changes in the cervical spine cause degeneration, leading to cervical spinal canal stenosis. This stenotic change can affect cerebrospinal fluid (CSF) dynamics by compressing the dural sac and reducing space in the subarachnoid space. We examined CSF dynamics at the craniovertebral junction (CVJ) using time-spatial labeling inversion pulse magnetic resonance imaging (Time-SLIP MRI) in patients with cervical spinal canal stenosis. METHODS: The maximum longitudinal movement of the CSF at the CVJ was measured as length of motion (LOM) in the Time-SLIP MRI of 56 patients. The sum of ventral and dorsal LOM was defined as the total LOM. Patients were classified into 3 groups depending on their spinal sagittal magnetic resonance imaging findings: control (n = 27, Kang classification grades 0 and 1), stenosis (n = 14, Kang classification grade 2), and severe stenosis (n = 15, Kang classification grade 3). RESULTS: Time-SLIP MRI revealed pulsatile movement of the CSF at the CVJ. The mean total, ventral, and dorsal LOM was 14.2 ± 9, 8.1 ± 5.7, and 3.8 ± 2.9 mm, respectively. The ventral LOM was significantly larger than the dorsal LOM. The total LOM was significantly smaller in the severe stenosis group (6.1 ± 3.4 mm) than in the control (16.0 ± 8.4 mm) or stenosis (11 ± 5.4 mm) groups (P < 0.001, Kruskal-Wallis H-test). In 5 patients, postoperative total LOM was improved after adequate decompression surgery. CONCLUSIONS: This study demonstrates that CSF dynamics at the CVJ are influenced by cervical spinal canal stenosis. Time-SLIP MRI is useful for evaluating CSF dynamics at the CVJ in patients with spinal canal stenosis.

Is there a risk of further displacement of the fractured fragment into the spinal canal in osteoporotic vertebral burst fractures after unilateral PKP? A prospective study.

BACKGROUND CONTEXT: The optimal treatment for osteoporotic vertebral burst fracture (OVBF) without neurological symptoms is still a matter of debate. PURPOSE: To evaluate the safety and efficacy of percutaneous kyphoplasty (PKP) for OVBF. STUDY DESIGN: The study is a prospective study and is registered in the China Clinical Trials Registry with the registration number ChiCTR-OOC-17013227. PATIENT SAMPLE: The study involved 119 patients with 137 fractured vertebrae who underwent unilateral PKP for OVBF. OUTCOME MEASURES: The measurements were carried out independently by two physicians and measured with picture archiving and communication system (PACS) and ImageJ software (National Institutes of Health, Bethesda, MD, USA). METHODS: The change in the spinal canal area and posterior wall protrusions (PWP) were measured before and after surgery via three-dimensional computed tomographic imaging (CT). Preoperative, postoperative, and final follow-up standing X-rays were used to measure the height of the anterior wall (HAW), height of the posterior wall (HPW), and local kyphotic angle (LKA). Additionally, visual analogue scale (VAS) and the Oswestry Disability Index (ODI) were also determined. RESULTS: Among the 137 vertebrae assessed, 79 exhibited an increased postoperative canal area, while 57 showed a decrease, with mean values of 8.28±6.871 mm² and -9.04±5.991 mm², respectively. Notably, no significant change in postoperative canal area was identified on the entire dataset (p>.01). There was a significant decrease between median preoperative (3.9 [IQ1-IQ3=3.3-4.8] mm) and postoperative (3.7 [IQ1-IQ3=3.0-4.4] mm) PWP (p<.01). Preoperative and postoperative HAW measurements were 19.4±6.1 mm and 23.2±5.2 mm, respectively (p<.01). However, at the final follow-up, the HAW was lower than the postoperative value. The HPW was also significantly improved after surgery (p<.01), but at the final follow-up, it was significantly decreased compared with the postoperative measurement. Following surgery, KA was significantly corrected (p<.01); however, at the final follow-up, relapse was detected (average KA: 18.4±10.3°). At the final follow-up, both VAS and ODI were significantly improved compared with the preoperative period (p<.01). As for complications, 50 patients experienced cement leakage, and 16 patients experienced vertebral refracture. All patients did not develop neurological symptoms during the follow-up. CONCLUSIONS: OVBF without neurological deficits showed significant improvement in symptoms during the postoperative period after PKP. There was no notable alteration in the spinal canal area, but a significant decrease in PWP was observed. Consequently, we posit that PKP stands as a secure and efficacious surgical intervention for treating OVBF cases devoid of neurological symptoms.

Parameters of nuclear magnetic resonance in patients with congenital narrowing of the lumbar spinal canal / Parâmetros de ressonância magnética em pacientes com estreitamento congênito do canal vertebral lombar / Parámetros de resonancia magnética en pacientes con estrechamiento congénito del conducto lumbar

ABSTRACT Objective: To compare the morphological parameters of magnetic resonance in patients with congenital narrowing of the lumbar spinal canal with patients with low back pain. Methods: A descriptive, retrospective, observational study was conducted with measurements in the axial and sagittal magnetic resonance sections of the vertebral body and canal of the lumbar spine of 64 patients with diagnosis of low back pain, which were compared with resonance images taken from 31 Mexican patients with congenital narrowing of the lumbar spinal canal. Results: The results show that patients with congenital narrowing of the lumbar spinal canal in the axial sections have a difference in diameters, being L2<13.9 mm, L3<13.3 mm, L4<12.9 mm, L5<13.1 mm, compared with controls L2<20.5 mm, L3<20.5 mm, L4<19.3 mm, L5<18.1 mm with p = 0.000. Conclusions: We found different measurements in the Mexican population compared to those found by similar studies. With the parameters obtained, it would be possible to make the proper diagnosis, surgical planning, and treatment.

RESUMO Objetivo: Comparar os parâmetros morfológicos de ressonância magnética de pacientes com estreitamento congênito do canal lombar com os pacientes com lombalgia. Métodos: Foi realizado um estudo descritivo, retrospectivo, observacional, com medições nos cortes axiais e sagitais de ressonância magnética do corpo e do canal vertebral da coluna lombar de 64 pacientes com diagnóstico de lombalgia, os quais foram comparados com ressonâncias feitas em 31 pacientes com diagnóstico de estreitamento congênito de canal vertebral lombar na população mexicana. Resultados: Os resultados obtidos mostram que os pacientes com estreitamento congênito do canal vertebral lombar apresentam, nos cortes axiais, uma diferença com relação aos diâmetros, sendo em L2 < 13,9 mm, L3 < 13,3 mm, L4 < 12,9 mm, L5 < 13,1 mm, em comparação com os controles L2 < 20,5 mm, L3 < 20,5 mm, L4 < 19,3 mm, L5 < 18,1 mm com p = 0,000. Conclusões: Foram encontradas distintas medições na população mexicana em comparação com outros estudos similares. Com os parâmetros obtidos será possível realizar o diagnóstico adequado, planejamento cirúrgico e tratamento.

RESUMEN Objetivo: Comparar parámetros morfológicos en resonancia magnética nuclear de pacientes con estrechamiento congénito del conducto lumbar con pacientes con lumbalgia. Métodos: Se realizó un estudio descriptivo, retrospectivo, observacional, con mediciones en cortes axiales y sagitales del cuerpo y conducto vertebral en resonancias magnéticas de columna lumbar de 64 pacientes con diagnóstico de lumbalgia y se comparó con resonancias magnéticas de 31 pacientes diagnosticados con estrechamiento congénito del conducto lumbar en población mexicana. Resultados: Los resultados obtenidos demuestran que los pacientes con estenosis lumbar congénita presentan, en cortes axiales, una diferencia en cuanto a los diámetros, siendo en L2 < 13,9 mm, L3 < 13,3 mm, L4 < 12,9 mm, L5 < 13,1 mm en comparación a los controles L2 < 20,5 mm, L3 < 20,5 mm, L4 < 19,3 mm, L5 < 18,1 mm con una p = 0,000. Conclusiones: Encontramos distintas mediciones en población mexicana comparado a otros estudios similares. Con estos parámetros obtenidos se podrá realizar un adecuado diagnóstico, planeación quirúrgica y tratamiento.

Evaluation of the diameter of the lumbar vertebral canal using computed tomography in mexican population / Avaliação do diâmetro do canal vertebral lombar por tomografia computadorizada na população mexicana / Evaluación del diámetro del conducto lumbar por tomografía computarizada en población mexicana

ABSTRACT Objective: To conduct a descriptive study to find measures of central tendency in the vertebral bodies L3, L4, and L5 in the Mexican population. Methods: Fifty patients were considered, 33 male and 17 female, aged between 30 and 55 years. Measurements were performed at the levels L3, L4 and L5 taking the interpedicular distance (A), mid-sagittal diameter (B), anteroposterior distance (AP) and the depth of lateral recess (R) in axial 2-mm sections of CT scans (Somaton Emotion, SIEMENS, 2 sections) in a Mexican population with healthy vertebral bodies, with no history of lumbar pathology. Results: Overall, the measures obtained were mean interpedicular distance of 22.80 in L3, range of 16.34/28.72. In L4, mean of 23.83, range of 17.62/27.92. In L5, mean of 25.28, range of 21.88/31.29. Conclusions: This study managed to make a database that did not exist in Mexico, using measures of central tendency. Therefore, it opens the way for it to be possible, in future studies, to identify predictive factors or even developing implants.

RESUMO Objetivo: Realizar um estudo descritivo para encontrar medidas de tendência central nos corpos vertebrais L3, L4 e L5 na população mexicana. Métodos: Foram considerados 50 pacientes, 33 homens e 17 mulheres, com idades entre 30 e 55 anos. Foram realizadas medidas no nível de L3, L4 e L5, tomando-se a distância interpedicular (A), o diâmetro mediossagital (B), a distância anteroposterior (AP) e a profundidade do recesso lateral (R) em cortes axiais de tomografia computadorizada (tomógrafo Somaton Emotion, SIEMENS, 2 cortes) em uma população mexicana com corpos vertebrais saudáveis, sem história prévia de patologia lombar. Resultados: Obteve-se, no geral, distância interpedicular média de 22,80 em L3, com faixa de 16,34/28,72. Em L4, média de 23,83, faixa de 17,62/27,92. Em L5, média de 25,28, faixa de 21,88/31,29. Conclusões: O presente estudo conseguiu fazer um banco de dados que não existia no país usando medidas de tendência central. Desse modo, abre-se o caminho para que, em estudos posteriores, seja possível identificar fatores preditivos ou até mesmo o desenvolvimento de implantes.

RESUMEN Objetivo: Realizar un estudio descriptivo para buscar medidas de tendencia central en los cuerpos vertebrales L3, L4 y L5 en población mexicana Métodos: Fueron considerados 50 pacientes, 33 hombres y 17 mujeres, con edades entre 30 y 55 años. Se realizaron mediciones a nivel de L3, L4, L5, tomando la distancia interpedicular (A), el diámetro mediosagital (B), la distancia anteroposterior (AP) y profundidad de receso lateral (R) en cortes axiales de tomografía axial computarizada de 2 mm (tomógrafo Somaton Emotion, SIEMENS, 2 cortes) en una población mexicana con cuerpos vertebrales sanos, sin antecedente previo de patología lumbar. Resultados: Se obtuvo en general una distancia interpedicular media de 22,80 en L3, con un rango de 16,34/28,72. En L4, media de 23,83, rango de 17,62/27,92. En L5, media de 25,28, rango de 21,88/31,29. Conclusiones: El presente estudio logró realizar una base de datos no existente en el país utilizando medidas de tendencia central. De este modo, se abre camino para que en estudios posteriores se logre determinar factores predictivos o inclusive el desarrollo de implantes.

Estudio Ultrasonográfico de las Estructuras Nerviosas del Canal Vertebral a Nivel de la Articulación Atlantooccipital en Caninos Adultos / Ultrasonographic Study of the Nervous Structures of the Vertebral Canal at the Atlantooccipital Joint Level in Adult Dogs

Los objetivos de este estudio fueron describir y comparar, mediante el ultrasonido, las estructuras nerviosas que se encuentran en el canal vertebral a nivel de la articulación atlanto-occipital en caninos adultos de talla corporal pequeña y grande. Se utilizaron 20 caninos adultos clínicamente sanos: 10 caninos de talla corporal pequeña (peso < a 10 kg) y 10 a caninos de talla corporal grande (peso > a 20 kg). Se realizó el examen ultrasonográfico con un transductor de 7,5 MHz, utilizando para ello el espacio atlantooccipital como ventana ecográfica. Se midieron diámetros verticales y horizontales del saco dural y médula espinal, y áreas del saco dural, médula espinal y espacio subaracnoídeo. Se calcularon razones entre algunas mediciones. Las estructuras estudiadas se observaron ecográficamente de modo similar en los caninos de ambos grupos. La duramadre se observó como una línea hiperecoica continua, adherida al borde óseo del canal vertebral. La médula espinal se observó como una estructura ovalada hipoecoica, con un parénquima homogéneo. Los diámetros verticales y horizontales del saco dural, médula espinal y las áreas del saco dural, médula espinal y espacio subaracnoídeo fueron significativamente menores (p<0,05) en los caninos de talla corporal pequeña. Las diferencias entre las áreas de médula espinal entre los grupos fue menor a 0,1 cm² y entre las áreas de saco dural y espacio subaracnoídeo fue de aproximadamente 1 cm². Se concluye que el ultrasonido permite visualizar adecuadamente la médula espinal y estructuras asociadas en la región de la articulación atlanto-occipital en caninos adultos. Finalmente, existieron diferencias mínimas en los valores de áreas de médula espinal y notoriamente mayores en los valores de áreas del saco dural y espacio subaracnoídeo entre ambos grupos de animales.

The goals of this study were to describe and compare by ultrasound the nervous structures in the vertebral canal at the atlanto-occipital joint region in small and large size adult dogs. A total of 20 healthy adult dogs were selected for the study. They were 10 small dogs (< 10 kg) and 10 large dogs (> 20 kg). Ultrasonographic examination was performed with a 7,5 MHz transducer and using the atlanto-occipital space as an echographic window. In transverse images, vertical and horizontal diameters of the dural sac and spinal cord and areas of the dural sac, spinal cord and subarachnoid space were measured. Some ratios between measurements were also calculated. Analysed structures were observed in a similar way in both groups of dogs. The dura mater was observed as an echogenic continuous line and attached to the bony border. The subarachnoid space has an anechoic appearance. The pia mater was observed as a thin echogenic line covering the spinal cord surface. The spinal cord was observed as an oval hypoechogenic structure inside the vertebral canal and with a homogeneous parenchyma without differentiation between gray and white matter. Vertical and horizontal diameters of the dural sac and spinal cord and areas of the dural sac, spinal cord and subarachnoid space were significantly different (P<0,05) in both group of dogs. Differences of spinal cord areas between small and large dogs were minimal (<0,1 cm²), compared with differences between dural sac and subarachnoid space areas (around 1 cm x). In conclusion, ultrasound allows an adequate examination of spinal cord and associated structures at the atlanto-occipital joint region in adult dogs. Differences between groups are minor in areas of spinal cord and larger in areas of dural sac and subarachnoid space.