TRAUMATIC SUBARACHNOID-PLEURAL FISTULA IN A DOG

Subarachnoid-pleural fistula is a rare occurrence in humans as a result of trauma or spinal surgery. Such fistulas commonly remain undiagnosed until sufficient cerebrospinal fluid accumulates in the pleural space to cause respiratory distress. We describe a subarachnoid-pleural fistula in a dog that occurred subsequent to blunt trauma sustained during a fall, with concurrent acute, traumatic intervertebral disc rupture. The extruded disc material penetrated the dura mater, allowing communication between the subarachnoid space and the extrapleural thoracic cavity. Radiographic, myelographic, and computed tomographic (CT) findings are reviewed. Abnormalities noted during myelography included an intradural-extramedullary lesion at T11-T12, with epidural leakage of contrast medium from the region of T12 extending cranially. In images from myelography and CT there was extravasation of contrast medium extending from the subarachnoid and epidural space into the extrapleural thoracic cavity.     

Rupture of the dura mater in two dogs caused by the peracute extrusion of a cervical disc

A rupture of the dura mater caused by the peracute extrusion of a cervical disc was diagnosed by myelography in two dogs. In both cases traction on the cervical spine resulted in contrast medium entering the ruptured intervertebral disc from the subarachnoid space. Both dogs became suddenly tetraparetic and unable to ambulate during vigorous exercise, but regained the ability to walk without surgical treatment.     

Intraventricular tension pneumocephalus and cervical subarachnoid pneumorrhachis in a bull mastiff dog after craniotomy

An eight-year-old bull mastiff dog underwent a craniotomy for surgical excision of an olfactory lobe meningioma. Rapidly progressive neurological deficits with cervical pain developed within the early postoperative period. Intraventricular and cervical subarachnoid space air accumulation (pneumorrhachis) was identified through magnetic resonance imaging and computed tomography. Repair of a dural defect using synthetic dura substitute resulted in gradual resolution of neurological signs attributable to the tension pneumocephalus and subarachnoid space pneumorrhachis. Regrowth of the meningioma was not observed. Postoperative intraventricular tension pneumocephalus and air accumulation within subarachnoid space are uncommon but life-threatening complications of intracranial surgery. Early diagnosis and treatment can result in a satisfactory outcome.     

Ultrasound-Guided Atlanto-Occipital Puncture for Myelography in the Horse

Complications of cervical myelography arising from the puncture of the subarachnoid space to collect the cerebrospinal fluid and to inject the contrast medium have been described in humans and animals. In this study, 2 ultrasound-guided procedures were developed for puncture of the atlanto-occipital subarachnoid space, collection of cerebrospinal fluid, and injection of contrast medium. Myelography was performed on 6 ataxic horses using these procedures. The first attempt to puncture the subarachnoid space was successful in 5 horses and in one horse, a second attempt was necessary. Collection of cerebrospinal fluid and injection of contrast medium were achieved without difficulty. Ultrasound-guided myelography allowed reduction of potential complications associated with blind percutaneous puncture of the subarachnoid space. Methods described in this study should be tried-at least initially in an experimental setting--to collect cerebrospinal fluid from the atlanto-occipital site in standing horses where it may represent an alternative method when lumbosacral cerebrospinal fluid collection has been unsuccessful or contaminated with blood.     

IOHEXOL MYELOGRAPHY IN THE DOG

Myelography with iohexol (180 mg iodine/ml, 0.25 ml/kg), a new nonionic radiologic contrast medium, was performed in 100 dogs of 33 different breeds. In 96 of the dogs the iohexol mixed evenly with the cerebrospinal fluid, providing an homogeneous, continuous column of contrast medium within the subarachnoid space, and a radiologic diagnosis of a normal myelogram or disease involving the spinal cord was made. Pooling of iohexol in the dorsal part of the subarachnoid space occurred in four dogs; whether this was related to poor mixing of contrast medium with cerebrospinal fluid or disease of the spinal cord and meninges requires further study. Postmyelographic signs of central nervous system irritation (fasciculations of the temporal muscles and three episodes of seizure activity) were observed in only one dog and were controlled with diazepam. The presenting neurologic signs were aggravated after myelography in four other dogs, two of which were eventually killed. This study provided further evidence of the increased safety of iohexol compared with metrizamide, the first of the nonionic media, as a contrast medium for myelography in the dog.     

MECHANICAL ASPECTS OF SUBARACHNOID SPACE PUNCTURE IN THE DOG

Lumbar subarachnoid space puncture using two different techniques was performed repeatedly on a dog following injection of metrizamide into the subarachnoid space at the cervical cistern. The lumbar needle punctures were observed fluoroscopically and recorded on 100-mm spot films at a rate of 2/sec. The needle tip indented the dura, depressing it several millimeters before penetration. A hemilaminectomy was performed on a cadaver, to expose the cord and intact meninges for confirmation of this compression. Cord compression and penetration during subarachnoid space puncture may contribute to the exacerbation or aggravation of neurologic signs that sometimes follows myelography.     

SPINAL SUBARACHNOID CYST IN A CAT

A 7-year-old neutered female domestic short hair cat was presented with hind limb ataxia. A subarachnoid cyst in the T10-T11 spinal cord region was identified by myelography as a collection of contrast medium in the subarachnoid space.     

STANDING MYELOGRAPHY IN THE HORSE USING A NONIONIC CONTRAST AGENT

Standing myelography in the horse has been previously described. In that study, metrizamide was used and significant complications were reported. In recent years, the introduction of less-toxic nonionic contrast media has reduced the incidence of complications. This study was undertaken to determine whether standing myelography using a nonionic contrast medium could provide a diagnostic study and be performed safely in the equine patient. Standing myelography was performed in eight horses. The contrast medium used was iohexol. In five horses a myelogram of diagnostic quality was achieved; in one horse contrast flowed only to the level of C6 and in two horses contrast medium did not reach the cervical subarachnoid space. Owing to the difficulty in achieving good flow of the contrast medium in some horses, this procedure may be of limited utility. However, if puncture of the lumbosacral subarachnoid space can be achieved easily and quickly, standing myelography may be a clinically useful procedure. It may be attempted in cases in which the economic value of the patient makes myelography under general anesthesia impractical. In patients presenting for evaluation of ataxia it may be possible to perform a standing myelogram at the time of CSF sample collection from the lumbosacral space.     

Thoraco-Lumbar Myelography with Water-Soluble Contrast Medium in Dogs I. Technique of Myelography; Side-effects and Complications

Abstract— A technique previously devised by the author for filling the greater part of the spinal subarachnoid space with water-soluble contrast medium (Kontrast U^R) has been tested for myelographic localization, of thoracic and lumbar compression of the spinal cord in the dog. The principle for the myelographic examination has been to inject the medium in the lumbar region in a sufficient dose for it to be forced beyond the compressed part of the subarachnoid space, to permit demonstration of both the posterior and anterior limit of the compression. A single injection of 20 per cent Kontrast U into the subarachnoid space in the dose generally used (0·3 ml/kg of body weight) does not seem to have any detrimental effect on the spinal cord. On the other hand, morphologic lesions of the spinal cord, presumably to be ascribed to the preparation in question, have been observed after repeated injections of contrast medium at the same examination.     

Pressure-volume index-based volume calculation of contrast medium for atlanto-occipital myelography in dogs

Subarachnoid pressure recordings were made during atlanto-occipital myelography in 45 dogs with clinical signs of spinal disease. Iohexol was injected at a dosage of 0.3 ml/kg body weight and simultaneous pressure values were recorded in the cerebellomedullary cistern. The mean subarachnoid pressure was 9 ± 3 mmHg before and 70 ± 32 mmHg at the end of administration. From the pressure change induced by the volume load, the pressure-volume index (PVI) of the subarachnoid space was calculated and found to be in close correlation with body weight and the crown-rump length (r = 0.94 and 0.87). Using the estimated PVI values, the appropriate volume of contrast medium can be calculated for an animal according to body weight. Dogs of a large body size require relatively less contrast medium than small-sized dogs (range 0.17-0.35 ml/kg). This calculated volume is unlikely to increase the subarachnoid pressure above 40 mmHg as a specific pressure limit. Using these data, simplified recommendations for the choice of contrast medium volumes have been generated.     

Cervical vertebral canal endoscopy in the horse: intra- and post operative observations

Reasons for performing study: Despite modern medical diagnostic imaging, it is not possible to identify reliably the exact location of spinal cord compression in horses with cervical vertebral stenotic myelopathy (CVSM). Vertebral canal endoscopy has been successfully used in man and a technique for cervical vertebral canal endoscopy (CVCE) has been described in equine cadavers. Objective: To determine the feasibility and safety of CVCE in healthy mature horses. Methods: Six healthy mature horses were anaesthetised. A flexible videoendoscope was subsequently introduced via the atlanto‐occipital space into the epidural space (epiduroscopy, Horses 1–3) or the subarachnoid space (myeloscopy, Horses 4–6) and advanced to the 8th cervical nerve. Neurological examinations were performed after surgery and lumbosacral cerebrospinal fluid (CSF) analysed in horses that had undergone myeloscopy. Results: All procedures were completed successfully and all horses recovered from anaesthesia. Anatomical structures in the epidural space (including the dura mater, nerve roots, fat and blood vessels) and subarachnoid space (including the spinal cord, blood vessels, arachnoid trabeculations, nerve roots and the external branch of the accessory nerve) were identified. During epiduroscopy, a significant increase in mean arterial pressure was recognised, when repeated injections of electrolyte solution into the epidural space were performed. In one horse of the myeloscopy group, subarachnoid haemorrhage and air occurred, resulting in transient post operative ataxia and muscle fasciculations. No complications during or after myeloscopy were observed in the other horses. CSF analysis indicated mild inflammation on Day 7 with values approaching normal 21 days after surgery. Conclusions: Endoscopic examination of the epidural and subarachnoid space from the atlanto‐occipital space to the 8th cervical nerve is possible and can be safely performed in healthy horses. Potential relevance: Cervical vertebral canal endoscopy might allow accurate identification of the compression site in horses with CVSM and aid diagnosis of other lesions within the cervical vertebral canal.     

Endoscopic anatomy of the cervical vertebral canal in the horse: a cadaver study

Reason for performing study: Localisation of spinal cord compression in horses with cervical vertebral stenotic myelopathy is inexact. Vertebral canal endoscopy has been used in man to localise spinal cord lesions and has the potential to become a useful diagnostic technique in horses. Objective: To establish a surgical approach via the atlanto‐occipital space to the cervical vertebral canal in equine cadavers and describe the endoscopic anatomy of the cervical epidural and subarachnoid spaces. Methods: The cadavers of 25 mature horses were used to assess 3 surgical methods to approach the cervical vertebral canal, including 2 minimally invasive and one open technique. Once the approach had been made, a flexible videoendoscope was inserted into the epidural space (epiduroscopy) or the subarachnoid space (myeloscopy) and advanced caudally until the intervertebral space between C7 and T1 was reached. Results: The epidural and subarachnoid spaces could not be accessed reliably using the minimally invasive techniques. Furthermore, damage to the nervous tissues was a frequent complication with these procedures. The open approach allowed successful insertion of the videoendoscope into the epidural and subarachnoid spaces in all horses and no inadvertent damage was observed. Anatomical structures that could be seen in the epidural space included the dura mater, nerve roots, fat and the ventral internal vertebral venous plexus. In the subarachnoid space, the spinal cord, nerve roots, blood vessels, denticulate ligaments and external branch of the accessory nerve were seen. Conclusions: Using the open approach, epiduroscopy and myeloscopy over the entire length of the cervical vertebral canal are possible in the mature horse. Potential relevance: Cervical vertebral canal endoscopy may become a valuable tool to localise the site of spinal cord injury in horses with cervical vertebral stenotic myelopathy and could aid in the diagnosis of other diseases of the cervical spinal cord.     

INTRACRANIAL SUBARACHNOID HEMORRHAGE FOLLOWING LUMBAR MYELOGRAPHY IN TWO DOGS

Intracranial subarachnoid hemorrhage is a rare but serious complication of lumbar puncture in humans. Possible sequelae include increased intracranial pressure, cerebral vasospasm, or mass effect, which can result in dysfunction or brain herniation. We describe two dogs that developed intracranial subarachnoid hemorrhage following lumbar myelography. In both dogs, myelography was performed by lumbar injection of iohexol (Omnipaque). Both the dogs underwent uneventful ventral decompressive surgery for disk herniation; however, the dogs failed to recover consciousness or spontaneous respiration following anesthesia. Neurologic assessment in both dogs postoperatively suggested loss of brain stem function, and the dogs were euthanized. There was diffuse subarachnoid hemorrhage and leptomeningeal hemorrhage throughout the entire length of the spinal cord, brain stem, and ventrum of brain. No evidence of infectious or inflammatory etiology was identified. The diagnosis for cause of brain death was acute subarachnoid hemorrhage. Our findings suggest that fatal subarachnoid hemorrhage is a potential complication of lumbar myelography in dogs. The cause of subarachnoid hemorrhage is not known, but may be due to traumatic lumbar tap or idiosyncratic response to contrast medium. Subsequent brain death may be a result of mass effect and increased intracranial pressure, cerebral vasospasm, or interaction between subarachnoid hemorrhage and contrast medium.     

Observations on myelography with meglumine iocarmate in the dog

Tne use of the contrast agent meglumine iocannate+ + Dimer X. May & Baker Ltd., Dagenham, Essex, England. 60% for myelography in 31 dogs (25 clinical cases and 6 experimental dogs)is described.

In the experimental dogs, there was a transient rise in both blood pressure and cerebrospinal fluid pressure after injection of Dimer X into the lumbar subarachnoid space, but dilution of the medium, or the addition of lignocaine, were not considered necessary. In 24 of the 25 clinical cases, the lumbar transpinal technique for myelography was used. A 5ml, or 3 ml (for dogs under15 kg), dose of Dimer X was administered and the contrast column moved to the expected site of the lesion by inclining the dog. Ten of the 25 clinical cases showed adverse side-effects after myelography and diazepam (Valium 10 — Roche) was administered to control them. In 7 of the 10 dogs that showed side-effects, the contrast medium had reached the upper cervical, or cranial, subarachnoid space.

Dimer X provided excellent radiographic contrast and diagnostic myelograms in all clinical cases. It was concluded that it was a suitable contrast agent for thoracolumbar myelography. In the absence of a suitable alternative for cervical myelography, it can be used, but side-effects must be expected and control measures taken.     

IMAGING DIAGNOSIS—CT MYELOGRAPHY IN A DOG WITH INTRAMEDULLARY INTERVERTEBRAL DISC HERNIATION

A 5‐year‐old Chihuahua was examined for peracute pain and paraparesis. Neuroanatomic localization was consistent with a symmetric T3‐L3 myelopathy. Computed tomography (CT) of the T9‐L5 vertebrae was normal. Myelography disclosed attenuation of the subarachnoid space from T11 to L1, consistent with spinal cord swelling. CT following the myelogram disclosed a focal area of intramedullary iodinated contrast medium at T13‐L1. At surgery, intervertebral disc material was removed from the spinal cord. Based on the findings in this patient, intramedullary disc herniation should be considered a cause for focal intramedullary contrast medium accumulation.     

Comparative study of continuous lumbar segmental epidural and subarachnoid analgesia in Holstein cows

Eight adult Holstein cows were used to compare the effects of lumbar segmental epidural analgesia (SEA) and lumbar segmental subarachnoid analgesia (SSA). A modified 17-gauge Huber point (Tuohy) needle was used to place a catheter with stylet into either the epidural space at the thoracolumbar (T13-L1) intervertebral space or the subarachnoid space at the lumbosacral intervertebral junction. The catheters were advanced so that their tips lay at the anterior lumbar (L1-L2) epidural space or at the thoracolumbar (T13-L1) subarachnoid space. The position of the catheter was confirmed radiographically. A 5% solution of procaine HCl was used at mean doses of 300 mg (6 ml) to induce SEA and 84.4 +/- 12.9 mg (1.7 +/- 0.3 ml) to induce SSA. Onset of analgesia to superficial and deep muscular pinprick stimulation was significantly (P less than 0.05) faster in cows with SSA than in those with SEA (10.4 +/- 2.3 minutes vs 15.9 +/- 3.8 minutes). Maximal thoracolumbar analgesia extended from spinal cord segments T12 to L4 on one or both sides of the vertebral column during SEA and from T10 to L3 on one or both sides during SSA. Duration of analgesia lasted significantly (P less than 0.05) longer in cows with SEA than in those with SSA (76.2 +/- 16.2 minutes vs 53.7 +/- 14.3 minutes). The advantages and disadvantages of the SEA catheter technique are discussed.     

INTRAOPERATIVE SPINAL ULTRASONOGRAPHY IN DOGS: NORMAL FINDINGS AND CASE-HISTORY REPORTS

Intraoperative spinal ultrasonography was performed in cervical and lumbar spine of 2 and 5 normal dogs, respectively, following ventral slot technique or dorsal or hemilamenectomy. The dura was hyperechoic, while the parenchyma was hypoechoic. The subarachnoid space was anechoic. An echogenic line was present in the center of the spinal cord, as seen in human. Pulsation of the spinal cord was noted during M-mode imaging. Clinical findings of one dog with thoracolumbar disk herniation and one with thoracic vertebral fracture/subluxation confirmed the usefulness of intraoperative spinal ultrasonography for real time evaluation of spinal canal spatial abnormalities (mass lesion and degree of spinal cord compression on scanning planes) and spinal cord motion. Follow-up ultrasound examinations were possible from 6 days postoperatively.     

犬正常脑脊液及脊髓造影时压力波的动态变化研究

用生理多导仪分别记录麻醉状态下正常犬脑脊液压力(CSFP)和麻醉状态下蛛网膜下腔注射造影剂时CSFP、呼吸和心跳的动态变化。发现CSFP受呼吸影响较大，一呼一吸为CSFP波的1个周期。其次，心跳也对波形产生影响。比较2种条件下的CSFP波，发现蛛网膜下腔注射造影剂可引起CSFP显著升高，且变化幅度显著增大。     

Ultrasound Measurements of the Dorsal Subarachnoid Space Depth in Healthy Trotter Foals during the First Week of Life

The aim of this study was to determine ultrasonographic measurements of the depth of the dorsal subarachnoid space in healthy foals so as to obtain reference values. The depth of the dorsal subarachnoid space was recorded in 50 trotter foals at day 1 (D1), 4 (D4), and 7 (D7) after birth, measuring the distance between the dura mater and the dorsal portion of the pia mater at the level of the cisterna magna, both in cross-sectional and longitudinal scans. Average, standard deviation, minimum and maximum values were calculated. Wilcoxon signed rank test was applied to verify data distribution. Analysis of variance (ANOVA) for repeated measurements and Bonferroni test as post hoc were applied to verify differences among D1, D4, and D7, both for cross-sectional and longitudinal scans. Student’s t-test for unpaired data was performed between fillies and colts to verify differences related to gender. Significance level was set at P < .05. Cross-sectional measurements were 7.2 ± 0.7 mm at D1, 7.4 ± 0.7 mm at D4, and 7.5 ± 0.6 mm at D7, whereas longitudinal measurements were 7.3 ± 0.6 mm at D1, 7.6 ± 0.6 mm at D4, and 7.6 ± 0.5 mm at D7. Differences in dorsal subarachnoid space depth were observed at D1 versus D7, both for cross-sectional and longitudinal scans, whereas no differences were found between fillies and colts. In this study, a reference range for the depth of the dorsal subarachnoid space has been reported in foals.