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The Predictive Value of CT Myelography, MR Myelography, or both in Infant Brachial Plexus Palsy
Raymond Tse, MD1, Jason Nixon, MD2, Ramesh Iyer, MD2, Kate Kuhlman-Wood, MD3 and Gisele Ishak, MD2
1Division of Plastic Surgery, Seattle Children's Hospital, Seattle, WA, 2Radiology, Seattle Children's Hospital, Seattle, WA, 3Plastic Surgery, University of Washington, Seattle, WA
INTRODUCTION: Pre-operative detection of spinal root avulsions in infant brachial plexus palsies is helpful for surgical planning and decision-making for reconstruction. While CT myelogram is the current standard imaging modality, it requires a lumber puncture, injection of contrast dye, and exposure to radiation. Advances in MRI technology have allowed this modality to be applied for myelography without the need for contrast or radiation. The purpose of this study is to determine the predictive value of CT myelography, MR myelography, and both for detection of nerve root avulsions at our institution. METHODS: Nineteen consecutive patients who underwent pre-operative CT and MR myelogram and reconstructive surgery were included in the study. Each study was de-identified, randomized, and analyzed post hoc by two radiologists who came up with consensus findings. The radiologists were blinded to the surgical findings. At surgical exploration nerve roots were considered avulsed if the dorsal root ganglion was identified outside of the intervertebral foramen, if there was an empty intervertebral foramen, or if the nerve root had a normal appearance in the absence of a response to electrical stimulation and there was no pre-operative clinical function. The findings of surgical exploration and pre-operative imaging were compared at each root level. RESULTS: A total of 95 root levels were examined. When pseudomeningoceles were used as signs of root avulsion, the findings on CT were similar to those on MR. The respective predictive values for CT and MR were: sensitivity of 0.68 and 0.68, specificity of 0.94 and 0.97, positive predictive value of 0.79 and 0.88, and negative predictive value of 0.91 and 0.90. There was no benefit of both CT and MR. CONCLUSIONS: Although CT myelography had better fine spatial resolution and confidence ratings by the radiologists, findings with CT and MR myelography were almost identical. Given the advantages of MR myelography, it has replaced CT myelography for pre-operative assessment for root avulsions at our institution.
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