Often the mid-thoracic area is slow to fill with contrast following cisternal puncture. The subarachnoid space is widest at the cisterna magna the cord widens slightly at the cervico- thoracic junction and the mid-lumbar area because of emerging nerve roots the cauda equina is outlined with a tapering 'fish-tail' appearance. Normally the spinal cord is outlined by smooth, regular columns of contrast medium. Sometimes it is necessary to perform both injections in order to outline a lesion fully. However, lumbar puncture may fail to yield an adequate amount of CSF for analysis. Lumbar myelography is usually preferred for suspected thoracolumbar disc disease, to outline the caudal extent of a lesion found with cisternal myelography and to demonstrate the caudal cord if contrast fails to pass a more cranial lesion. Lumbar myelography overcomes this since contrast medium is injected under pressure and has no 'escape route' so it will be forced around lesions. Thus, contrast may not reach the sites of lesions causing marked cord swelling or compression. However, if resistance is encountered in the subarachnoid space due to the presence of a significant lesion the contrast medium will instead pass cranially into the skull. The amount of CSF that can be collected from a lumbar puncture is very variable, although in cases of spinal disease lumbar CSF is more likely to be abnormal than CSF obtained from the neck.Īdvantages and disadvantages of the two techniquesĬisternal myelography is easier to perform, especially in fat animals, and yields a reliable amount of CSF. Lumbar myelography-injection is made between caudal lumbar vertebrae, ideally L5-6 in dogs and L6-7 in cats. Contrast medium warmed to body temperature to reduce viscosity is then injected slowly at a dose rate of up to 0.3ml/kg, depending on the expected site of the lesion.Ģ. Cerebrospinal fluid can be collected in ample amounts from this site, for analysis. Cisternal myelography-injection made between the back of the skull and the arch of C1 into the cisterna magna. Contrast is injected via either the cisternal or the lumbar route:ġ. Seizures occasionally occur on recovery, especially if contrast medium has entered the skull. General anaesthesia is essential and the technique should be performed under aseptic conditions. Opacification of the subarachnoid space using non-ionic, low osmolarity, water-soluble iodinated contrast media at about 300 mg iodine/ml (e.g., iopamidol, NIOPAM iohexol, OMNIPAQUE). Areas of cord swelling or compression can then be identified. In medium and large dogs where the thickness of the tissue to be radiographed exceeds 10cm a grid is needed to reduce the effects of scattered radiation.Ĭontrast techniques may be used to outline the spinal cord and cauda equina, which are not visible on plain radiographs. Good centring and collimation of the X-ray beam will ensure that geometric distortion is minimal and will reduce the amount of scattered radiation produced. However, in the traumatised patient in which vertebral instability may be present, the abolition of protective muscle spasm by anaesthesia may be dangerous and so survey lateral radiographs with the patient conscious should be taken first.ĭue to the divergence of the primary X-ray beam and the importance of imaging the intervertebral disc spaces, the spine should be radiographed in short segments, using radiolucent foam wedges to make sure that it is aligned parallel to the table top. Paraparesis, hemiparesis or tetraparesis/plegiaĬareful positioning is essential for most radiographic studies of the spine, and this necessitates the use of heavy sedation or general anaesthesia. Books & VINcyclopedia of Diseases (Formerly Associate).

VINcyclopedia of Diseases (Formerly Associate).

X ray cervical spine normal