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 74 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. (J Am Vet Med Assoc 2011;238:1296-1300)