Maternal-fetal lead poisoning from a 15-year-old bullet.

Blood lead was mildly elevated (31 microg/dl, where 25 microg/dl is the upper limit of the normal range) in a woman with lumbar bullet fragments who was evaluated for anemia in the 23rd week of pregnancy. She required Cesarean section at term for pre-eclampsia and fetal distress. The infant had multiple congenital abnormalities. Postpartum maternal blood lead level was 75-85 microg/dl. The infant's blood lead level was also elevated. Chelation lowered the infant's blood lead level, but not the mother's. Surgical debulking of the lumbar lead deposits was followed by a fall in blood lead level from 65 to 52 microg/dl. This case demonstrates a remarkable gestational rise in maternal blood lead level. The infant's congenital abnormalities could be causally related to lead.

Fenestration of the extracranial vertebral artery: review of the literature.

STUDY DESIGN: A case report on fenestration of the extracranial vertebral artery found at forensic autopsy. OBJECTIVE: To describe an extracranial vertebral artery fenestration involving the subaxial cervical region, assessed radiographically and angiographically at forensic autopsy, in a young man. SUMMARY OF BACKGROUND DATA: Duplications or fenestrations of the extracranial course of the vertebral artery are rare and seen almost exclusively as a coincidental finding in angiographic studies. The terms "fenestration" and "duplication" are often incorrectly used synonymously. The former describes the passage of the duplicated vessel within the vertebral foramen transversarium, whereas the latter refers to the duplicated vessel coursing additionally through the spinal canal. The reported cases describing duplication are more common. Only three cases of vertebral extracranial fenestrations, involving only the upper cervical spinal segments, have been described in the literature. RESULTS: Angiography showed a fenestration of the vertebral artery localized between the intervertebral spaces of C2-C3 and C3-C4. At dissection, the vertebral artery appeared as a single vessel in the area of the fenestration. Histologically, a distinct difference in the thickness and composition of the vessel walls was found between the two vessel trunks. At autopsy, no further anomalies were observed in the vessels supplying the brain, which is contrary to the commonly held belief that fenestration is frequently associated with vascular malformations. CONCLUSION: Fenestration of the extracranial course of the vertebral artery is a developmental or congenital anomaly. A review of the literature demonstrated that this is apparently only a coincidental finding and has no pathologic significance.

Modification of C1-C2 transarticular screw fixation by image-guided surgery.

STUDY DESIGN: This is a feasibility study of image-guided surgery for C1-C2 transarticular screw fixation comparing postoperative screw position in a nonrandomized prospective cohort with a historic control group in which fluoroscopic guidance was used alone. OBJECTIVES: To evaluate the potential benefits and disadvantages of image-guided surgery for C1-C2 screw placement. SUMMARY OF BACKGROUND DATA: C1-C2 transarticular screw fixation is biomechanically superior to other current surgical stabilization procedures. The original technique for C1-C2 screw placement relies on anatomic landmarks and intraoperative fluoroscopy. Screw misplacement or anatomic variations can result in vertebral artery injury. Image-guided surgery involves using computed tomography (CT) data to plan the optimal screw trajectory before surgery and then use this data to guide screw placement during the actual surgery. Promising results of this technique are reported in the literature, but no direct comparison between image-guided surgery and conventional surgical techniques has been previously reported. METHODS: The image-guided surgery group consisted of 37 prospective patients. The historic control group included 78 patients who had similar surgeries performed using only fluoroscopic guidance. For the image-guided surgery group, subluxation was reduced by positioning at the time of CT examination. The CT data were transferred to a StealthStation (Sofamor-Danek, Memphis, TN) surgical planning and guidance computer system, and an optimal screw trajectory was determined for the right and left transarticular screws. After matching the surgical field to the virtual computer field, C2 was drilled according to the planned screw trajectory, and screws were placed. Plain radiographs and CT were used for postoperative evaluation of the image-guided surgery group. RESULTS: Image-guided surgery reduced but did not eliminate the risk of screw misplacement. Surgical time was not increased overall. CONCLUSIONS: Image-guided surgery is an effective tool for the achievement of correct screw placement in C1-C2 transarticular screw fixation procedures. The procedure remains technically demanding.

A multicenter study to improve emergency medicine residents' recognition of intracranial emergencies on computed tomography.

STUDY OBJECTIVE: Cranial computed tomography (CT) has assumed a critical role in the practice of emergency medicine for the evaluation of intracranial emergencies. Several recent studies have documented a deficiency in the emergency physician's ability to interpret these studies. The purpose of this study was to quantify the baseline ability of emergency medicine residents to interpret cranial CTs, and to test a novel method of cranial CT interpretation designed for the emergency physician in training. METHODS: A standardized pretest was administered to assess baseline ability to interpret CT scans. A standardized posttest was given 3 months after the course. Each test consisted of 12 CT scans with a short accompanying history. All scans were validated by 3 expert reviewers for difficulty and diagnosis. A 2-hour course based on the mnemonic "Blood Can Be Very Bad" was then administered. "Blood" reminds the examiner to search for blood, "Can" prompts the examiner to identify 4 key cisterns, "Be" denotes the need to examine the brain, "Very" prompts a review of the 4 ventricles, and finally "Bad" reminds the examiner to evaluate the bones of the cranium. RESULTS: Eighty-three residents at 5 institutions were initially examined. The mean percentage correct before the course was 60% (95% confidence interval [CI] 58%-64%) on the standardized pretest. At retesting 3 months after the course, the accuracy rate increased to 78% (n=61, 95% CI 75%-81%, P<.001 paired t test). CONCLUSION: Emergency medicine residents are deficient in their ability to interpret cranial CT scans. A novel educational course was demonstrated to significantly improve this ability.

Presurgical finite element analysis from routine computed tomography studies for craniofacial distraction: II. An engineering prediction model for gradual correction of asymmetric skull deformities.

Finite element analysis from routine computed tomography studies (CT/FEA) allows clinicians to predict the mechanical and anatomic consequences of specific distraction systems before human application. A realistic three-dimensional CT/FEA engineering model of an actual plagiocephalic infant with unicoronal synostosis was developed using 4215 parabolic triangular shell elements and intracranial pressure conditions ranging from 10 to 20 mmHg. The completed finite element analysis model was used to predict the anatomic outcome of multiaxial distraction delivered by hypothetical patterns of rod and node distraction units. The predictions for the various patterns of distraction units were also compared quantitatively with respect to force, stress, strain, and intracranial volume. Best anatomic corrections were achieved with bilateral patterns of distraction units that simultaneously elongated the ipsilateral cranium and shortened the contralateral cranium. Greatest strain levels were experienced within the osteotomy callus, greatest stress levels at the appliance anchorage sites, and the greatest rod force at the ipsilateral lower coronal position.

Pre-surgical CT/FEA for craniofacial distraction: I. Methodology, development, and validation of the cranial finite element model.

Recently, surgeons have begun to treat serious congenital craniofacial deformities including craniosynostoses with mechanical devices that gradually distract the skull. As a prospective means of treatment planning for such complex deformities, FE models derived from routine preoperative CT scans (CT/FEA) would provide ideal patient specific engineering analyses. The purpose of this study was to assess the dimensional and predictive accuracy of the CT/FEA process through the development of a 3D model of a dry human calvarium subjected to two-point distraction ex vivo. Comparative skull measurements revealed that CT/FEA construction error did not exceed 1% for transcranial dimensions, and the thickness error did not exceed 8.66% or 0.31 mm. CT/FEA strain predictions for the central region of the skull, between the distraction posts, were not statistically different from homologous gage values at P < 0.05. Peripherally, however, the strain fields were less well behaved and the FE predictions showed only general qualitative agreement with gage recordings.

Computed tomography in degenerative spinal stenosis.

To assess the value of computed tomography in degenerative lumbar spinal stenosis, postoperative computed tomography was compared to preoperative studies and other radiographic modalities in 20 patients, ten with an excellent surgical result and ten with a poor result. A close correlation was found between moderate to severe residual stenosis on postoperative CT and surgical failure. The most common cause of failure was inadequate unroofing of the lateral gutters. Computed tomography with multiplanar reconstructions detected stenosis not only in the central canal and lateral recesses, but in the neuroforaminal as well. Central canal stenosis corresponded to a marked deformity of complete block on myelography. Lateral recess stenosis was shown more often by computed tomography than by blunting of the nerve root sheaths on the myelograms. Neuroforaminal encroachment seen on computed tomography sagittal reconstructions was not demonstrable by myelography. Degenerative spondylolisthesis, a special stenotic condition, produced a characteristic "double margin" sign on computed tomography and the critical stenosis of the lateral recesses was demonstrated. This study suggests that the superior definition of the sites of degenerative spinal stenosis provided by computed tomography should lead to higher surgical success rates.

CT of facet distraction in flexion injuries of the thoracolumbar spine: the "naked" facet.

Vertical distraction of the articular processes is an important sign of ligamentous disruption due to flexion injuries of the thoracolumbar spine. In addition to illustrating this finding in cross section (the "naked" facet), computed tomography in the transaxial plane allows assessment of the presence and position of fracture fragments that may encroach on the spinal canal. Image reconstruction in sagittal and coronal planes provides a clear demonstration of the degree of bony compression, facet distraction, and kyphosis associated with flexion injuries without additional patient manipulation or radiation exposure.

Quantitative assessment of the lumbar spinal canal by computed tomography.

An experimentally validated simple standardized method for making precise measurements of the spinal canal directly from the video display of a CT scanner is described. Using this method, normal values for anteroposterior diameter, interpediculate distance, and cross-sectional area of the lumbar spinal canal have been determined in a series of 60 adults. A careful study of canal configuration combined with the prudent use of the normal values should allow the CT diagnosis of lumbar spinal stenosis to be made with a high level of confidence.