Asystole associated with iohexol myelography in a dog

IV Versus Myelography Computed Tomography for Thoracolumbar Intervertebral Disc Extrusion Surgical Planning in French Bulldogs

Accurate diagnostic imaging is required for surgical planning of acute thoracolumbar intervertebral disc extrusion. However, data comparing the accuracy of conventional IV contrast-injected computed tomography (CT) and myelography CT for hemilaminectomy localization and size assessment are sparse. In this study, IV contrast-injected CT and myelography CT were performed in 48 French bulldogs presenting with acute disc herniation and compared with postsurgical CT. CT images were evaluated by three raters. IV contrast-injected CT erroneously identified the compressive lesion site significantly more often than myelography CT. The length of the compressive lesion was significantly higher using myelography CT compared with conventional CT, but this did not lead to relevant consequences on the surgical opening site length. Myelography CT should therefore be recommended when thoracolumbar disc disease is suspected and multiple compressive lesions are visualized on IV-injected CT in French bulldogs.

Comparison of Imaging Methods and Population Pattern in Dogs with Spinal Diseases in Three Periods between 2005 and 2022: A Retrospective Study

The aim of this study was the long-term comparison of the imaging methods used in dogs with neurologic diseases related to the spine and spinal cord. We also compared the occurrence of neurological diseases according to the localization, gender, age, and breed. As the availability of magnetic resonance imaging (MRI) has increased over the years, resulting in increased diagnostic and therapeutic success rates, the study was divided into three time periods (2005-2014, 2015-2018, and 2019-2022). Our results suggest changes in the population structure of the dogs studied and changes in the use of diagnostic methods that directly or indirectly influence the choice and success rate of therapy. Our results may be of interest to owners, breeders, practicing veterinarians, and insurance companies.

EXTRAVASATION OF CONTRAST MEDIA AFTER SUBCARAPACIAL VESSEL INJECTION IN THREE CHELONIAN SPECIES

The subcarapacial vessel is a popular site for venipuncture and intravenous medication administration in chelonians. Reports of adverse effects when using this site have increased, prompting evaluation of its safety. This study aimed to evaluate the anatomy of the subcarapacial vessel in 25 individual chelonians (2 box turtles, 3 red-eared sliders, and 20 red-footed tortoises) using computed tomography (CT). Individuals were sedated and administered contrast in the subcarapacial vessel. The vessel was visualized in 50% of the box turtles and red-footed tortoises, and 100% of the red-eared sliders. All species had contrast extravasation in the subarachnoid space, with red-footed tortoises having the largest percentage (70% compared to 50% and 33% of box turtles and red-eared sliders, respectively). Extravasation of contrast in the trachea or bronchi (70%) and lungs (80%) was seen in the red-footed tortoises only. Higher prevalence of contrast extravasation in the red-footed tortoises is likely because of anatomical differences, including a more cranially extending lung field and domed-shaped carapace compared to the other species. These findings highlight the risk associated with using the subcarapacial vessel for intravenous medication administration in certain species of chelonian.

Usefulness of spinal unenhanced computed tomography and CT-myelography in the age of multidetector CT technology and magnetic resonance imaging - Preliminary considerations

Over the last decade, magnetic resonance imaging (MRI) and multidetector computed tomography (MDCT) have revolutionized diagnostic potential in small animal practice, providing adequate assessment of spinal diseases at levels comparable to that achieved in human radiology. T2-weighted MRI images are extremely sensitive to intramedullary parenchymal disorders, while balanced steady-state free precession sequences provide high-quality myelographic images of the spine without the need of intrathecal contrast medium administration. Multidetector computed tomography, with its near-isotropic spatial resolution and multiplanar reformatting of the acquired datasets, provides sufficient stratigraphic details of the spinal cord and the epidural space, facilitating the detection of compressive pathologies without the need of subarachnoid opacification. Nowadays, MDCT and low-field (LF) MRI have become fairly standard and available in academic institutions and private veterinary facilities, appearing to be valuable, complementary, and non-invasive diagnostic tools for imaging the spine. In this scenario, this clinical communication provides a series of preliminary observations that may help to reconsider the usefulness of CT-myelography in the light of its invasiveness and actual diagnostic advantages compared to MRI and unenhanced MDCT for the assessment of compressive and non-compressive spinal diseases in small animals.

Perianesthetic morbidity and mortality in dogs undergoing cervical and thoracolumbar spinal surgery

OBJECTIVE

To evaluate and compare perioperative morbidity and mortality in dogs undergoing cervical and thoracolumbar spinal surgery.

STUDY DESIGN

Prospective case series.

ANIMALS

157 dogs undergoing cervical or thoracolumbar spinal surgery.

METHODS

Data were collected sequentially on canine cases presented from the Neurology Section of the North Carolina State University Veterinary Teaching Hospital for anesthesia and surgery for cervical spinal cord disease. Simultaneously, data were collected on all thoracolumbar spinal surgery cases during the same time period. Data included signalment, drugs administered, surgical approach, disease process, cardiac arrhythmias during anesthesia, and outcome.

RESULTS

Data were collected from 164 surgical events in 157 dogs. There were 52 cervical approaches; four dorsal and 48 ventral. All thoracolumbar surgeries were approached dorsolaterally. Four dogs 4/52 (7.6%) undergoing a cervical approach did not survive to discharge. Two dogs (2/8; 25%) underwent atlanto-axial (AA) stabilization and suffered cardiovascular arrest and two dogs (2/38; 5.2%) undergoing cervical ventral slot procedures were euthanized following anesthesia and surgery due to signs of aspiration pneumonia. All dogs undergoing thoracolumbar surgery survived until discharge (112/112). Mortality in dogs undergoing cervical spinal surgery was greater compared with dogs undergoing thoracolumbar spinal surgery (p = 0.009), however, in dogs undergoing decompressive disc surgery, intraoperative death rates were not different between dogs undergoing a cervical compared with thoracolumbar approaches (p = 0.32) nor was there a significant difference in overall mortality (p = 0.07).

CONCLUSION AND CLINICAL RELEVANCE

Overall, dogs undergoing cervical spinal surgery were less likely to survive until discharge compared with dogs undergoing thoracolumbar spinal surgery. Mortality in dogs undergoing cervical intervertebral disc decompression surgery was no different than for dogs undergoing thoracolumbar intervertebral disc decompression surgery. However, dogs undergoing cervical intervertebral disc decompression surgery should be considered at risk for aspiration pneumonia.

A Prospective Evaluation of CT in Acutely Paraparetic Chondrodystrophic Dogs

The clinical usefulness of computed tomography (CT) as a sole diagnostic modality in identifying disc lesion(s) in chondrodystrophic breeds presenting with acute signs of intervertebral disc disease (IVDD) is incompletely characterized. CT was used prospectively to determine the validity of this tool. Neurologic examinations and CT scans were performed on all dogs at presentation. Surgical decompression was based on those findings. Clinical follow-up examinations were performed on days 1 and 14 postsurgically. CT detected a lesion consistent with clinical findings in 63 of 69 cases (91%). All 63 dogs with Hansen type I IVDD lesions were identified on CT alone. The surgeon and radiologist agreed on lesion level in 72 of 78 lesions (92%) and lateralization in 71 of 78 lesions (91%). Improvement in neurologic grade was documented in 60 of 69 dogs (87%) by 14 days. CT imaging can be used as a single imaging modality in chondrodystrophic dogs presenting with acute paresis. CT used in this manner is a reliable and noninvasive tool for detecting spinal compression secondary to IVDD in chondrodystrophic dogs.

Computed tomographic and histological findings of Hansen type I intervertebral disc herniation in dogs

OBJECTIVE

To evaluate whether non-contrast-enhanced computed tomography (CT) as a stand-alone imaging modality can be used to define the Hansen type I intervertebral disc herniation (IVDH) lesion and also whether the Hounsfield unit (HU) value of herniated disc is relevant to clinical duration and to histopathological chronicity of extruded disc material.

METHODS

Information from a series of CT studies performed on 45 dogs with a presumptive diagnosis of Hansen type I IVDH was used. Clinical duration of IVDH was estimated based on time from onset of signs per owner communication to time of surgical intervention. Hansen type I IVDH was confirmed at surgery. Retrieved herniated disc was histologically examined. The HU values were analyzed to correlate the clinical duration and histopathological chronicity of the disc lesion.

RESULTS

Non-contrast-enhanced CT provided sufficient diagnostic information to plan surgery in 42 of 45 dogs (93%). The value of the HU was significantly higher in clinically chronic cases (n = 12) compared to peracute cases (n = 11) (p <0.05). The HU values were significantly correlated with clinical duration (r = 0.482, p = 0.0008) and histopathological chronicity of the herniated disc (r = 0.408, p = 0.0056).

CONCLUSION

Consistent with the previous reports, the use of non-contrast-enhanced CT alone was sufficient for the diagnosis and surgical planning in most patients with Hansen type I IVDH in the thoracolumbar spine. In addition, the present study suggested that HU values on CT images may be useful in the evaluation of disease chronicity of IVDH.

Mechanisms of injury and emergency care of acute spinal cord injury in dogs and cats

OBJECTIVES

To review the literature in regards to the pathophysiology of acute spinal cord injury, and to describe current concepts in regards to patient assessment, diagnostic, and therapeutic measures with a special emphasis on emergency and critical care considerations.

ETIOLOGY

Acute spinal cord injury occurs in 2 phases. The primary injury occurs at the time of initial injury and may include intervertebral disk herniation, vertebral fracture or luxation, penetrating injury, and vascular anomalies such as fibrocartilaginous embolic myelopathy. Secondary injury occurs following primary injury and is multifactorial encompassing numerous biochemical and vascular events that result in progression of injury.

DIAGNOSIS

The diagnosis is based on history and physical examination findings. A neurologic examination should be performed following initial patient assessment and stabilization. Further diagnostics to characterize acute spinal injury include radiographs and advanced imaging modalities such as myelography, computed tomography, or magnetic resonance imaging.

THERAPY

Initial treatment should focus on addressing the patient's cardiovascular and respiratory system. Supportive measures to support systemic perfusion are vital to minimizing secondary injury. Specific therapy toward minimizing secondary injury in veterinary medicine remains controversial, especially in regards to the utilization of methylprednisolone. Other therapies are either in need of additional research or have failed to document clinical difference.

PROGNOSIS

The prognosis for acute spinal injury is varied and is dependent upon the presence of concurrent trauma, location, and type of primary injury sustained, and extent of neurologic impairment at the time of initial presentation. The etiology of the underlying trauma is of great importance in determining prognosis and outcome. Loss of deep pain is generally accepted as a poor prognostic indicator; however, even these patients can recover depending on their response to treatment.

Permanent monoparesis in a dog after intramedullary injection of iohexol into the lumbar spinal cord

Abstract

CASE HISTORY

An 8-year-old, spayed, Doberman Pinscher bitch presented for assessment of acute hindlimb paresis.

CLINICAL FINDINGS

During a lumbar myelographic contrast study a small volume of iohexol contrast agent was inadvertently injected into the cord parenchyma. After surgical hemilaminectomy for an intervertebral disc extrusion at L1-2 the dog recovered use of one hindlimb, but had ongoing extensor weakness of the left hindlimb. Left femoral nerve function had not returned after 14 months.

DIAGNOSIS

EMG findings 14 months after the incident indicated persistent femoral neuropathy consistent with the intramedullary contrast injection at L3-4.

CLINICAL RELEVANCE

Inadvertent deposition of iohexol into spinal cord parenchyma may be rare, but if it occurs it can have long-lasting consequences.

Incidence of and risk factors for seizures after myelography performed with iohexol in dogs: 503 cases (2002-2004)

OBJECTIVE

To establish the incidence of and risk factors for seizures following myelography performed with iohexol in dogs.

DESIGN

Retrospective case series.

ANIMALS

503 dogs.

PROCEDURES

Medical records were searched for dogs that underwent myelography between April 2002 and December 2004. Data extracted included body weight, breed, age, sex, volume and dose of iohexol, site of injections, location of lesion, duration of anesthesia, surgical procedures immediately after myelography, use of acepromazine, and presence or absence of seizures.

RESULTS

15 (3%) dogs had postmyelographic seizures. Risk factors significantly associated with seizures were size of dogs (large dogs were 35.35 times as likely to have seizures as were small dogs), location of contrast medium injection (dogs in which iohexol was injected into the cerebellomedullary cistern were 7.4 times as likely to have seizures as were dogs in which iohexol was injected into the lumbar cistern), location of lesion (dogs with lesions at the level of the cervical portion of the vertebral column were 4.65 times as likely to develop seizures as were dogs with lesions in other regions), and total volume of iohexol. Mean ± SD total volume of iohexol was 11.73 ± 5.52 mL (median, 10.5 mL [range, 3.0 to 21.0 mL]) for dogs that had seizures and 4.57 ± 4.13 mL (median, 3.5 mL [range, 0.75 to 45.0 mL]) for those that did not.

CONCLUSIONS AND CLINICAL RELEVANCE

Large-breed dogs with cervical lesions and large volumes of iohexol injected into the cerebellomedullary cistern had the highest risk of seizures. The use of contrast medium volumes > 8 mL in large dogs should be avoided, with preference given to injections into the lumbar cistern.

Does choice of imaging modality affect outcome in dogs with thoracolumbar spinal conditions?

OBJECTIVES

A retrospective cross-sectional study was done to look for differences in outcome in canine spinal patients that had myelography compared to those that had magnetic resonance imaging.

METHODS

Medical records of dogs with spinal conditions in the period January 2004 to December 2007 were reviewed. Data on patient age, gender, breed, size, neurolocalisation, rate of onset, imaging modality, time taken to image, type of treatment, neurological grade at admission and discharge, length and cost of hospitalisation and status at discharge were collected. Only dogs with neurological grade 3 to 6 with signs referable to the thoracolumbar spine were included.

RESULTS

Of 107 dogs that met the inclusion criteria, 66 (62%) had myelography and 41 (38%) had magnetic resonance imaging. Using multivariable analyses, non-chondrodystrophoid breed, increasing age and higher neurological grade at admission were found to be associated negatively with survival. Neurological grade 5 at admission was found to be associated positively with likelihood of neurological improvement. Male gender, higher neurological grade at admission and medical treatment were associated negatively with length of hospitalisation. magnetic resonance imaging, surgical treatment and period of hospitalisation were associated positively with total cost of hospitalisation.

CLINICAL SIGNIFICANCE

No significant association was found between type of imaging and any patient outcome variables except cost of hospitalisation, which was higher for dogs having magnetic resonance imaging. Although magnetic resonance imaging may be considered advantageous compared to myelography because it is non-invasive and provides superior anatomical detail for surgical guidance, no beneficial effect on outcome of dogs with non-ambulatory thoracolumbar spinal disease was found.

Risk factors associated with development of seizures after use of iohexol for myelography in dogs: 182 cases (1998)

OBJECTIVE

To determine prevalence of seizures after use of iohexol for myelography and identify associated risk factors in dogs.

DESIGN

Retrospective study.

ANIMALS

182 dogs that received iohexol for myelography in 1998.

PROCEDURE

Medical records were reviewed for age, breed, sex, weight, dose and total volume of iohexol, injection site, number of injections, lesion type and location, total duration of anesthesia, duration from time of iohexol injection to recovery, presence and number of seizures, and whether surgery followed the myelogram.

RESULTS

39 (21.4%) dogs had at least 1 generalized seizure during or after myelography. Injection site was strongly associated with prevalence of seizures, and risk of seizure was significantly higher after cerebellomedullary injections, compared with lumbar injections. Mean total volume of iohexol administered to dogs that had seizures was significantly higher, compared with that administered to dogs that did not have seizures, although dosage did not differ between groups. Weight was significantly correlated with risk of seizure, and dogs that weighed > 20 kg (44 lb) had higher prevalence of seizures than dogs that weighed < 20 kg.

CONCLUSIONS AND CLINICAL RELEVANCE

It is preferential to administer iohexol via the L5-6 intervertebral space to minimize the risk of seizures. Higher prevalence of seizures in large dogs, compared with smaller dogs, may be caused by administration of larger total volumes of contrast agent per volume of CSF.