Imaging Appearance of Ballistic Wounds Predicts Bullet Composition: Implications for MRI Safety.

OBJECTIVE. The purpose of this article was to determine whether the radiographic and CT appearance of ballistic projectiles predicts their composition and to characterize the translational, rotational, and temperature effects of a 1.5-T MRI magnetic field on representative bullets. MATERIALS AND METHODS. Commercially available handgun and shotgun ammunition representing projectiles commonly encountered in a clinical setting was fired into ballistic gelatin as a surrogate for human tissue, and radiographs and CT images of these gelatin blocks were obtained. MR images of unfired bullets suspended in gelatin blocks were also obtained using T1- and T2-weighted sequences. Magnetic attractive force, rotational torque, and heating effects of unfired bullets were assessed at 1.5 T. RESULTS. Fired bullets were separated into ferromagnetic and nonferromagnetic groups based on the presence of a debris trail and deformation of the primary projectile in the gelatin blocks. Whereas ferromagnetic bullets showed mild torque forces and marked imaging artifacts at 1.5 T, nonferromagnetic bullets did not have these effects. Heating above the Food and Drug Administration limit of 2°C was not observed in any of the projectiles tested. CONCLUSION. Patients with ballistic embedded fragments are frequently denied MRI because the bullet composition cannot be determined without shell casings. We found that radiography and CT can be used to identify nonferromagnetic projectiles that are safe for MRI. We also present an algorithm for determining the triage of patients with retained bullets.

Statistical learning of blunt cerebrovascular injury risk factors using the elastic net.

PURPOSE: To compare logistic regression to elastic net for identifying and ranking clinical risk factors for blunt cerebrovascular injury (BCVI). MATERIALS AND METHODS: Consecutive trauma patients undergoing screening CTA at a level 1 trauma center over a 2-year period. Each internal carotid artery (ICA) and vertebral artery (VA) was independently graded by 2 neuroradiologists using the Denver grading scale. Unadjusted odds ratios were calculated by univariate and adjusted odds ratios by multiple logistic regression with FDR correction. We applied logistic regression with the elastic net penalty and tenfold cross-validation. RESULTS: Total of 467 patients; 73 patients with BCVI. Maxillofacial fracture, basilar skull fracture, and GCS had significant unadjusted odds ratios (OR) for ICA injury and C-spine fracture, spinal ligamentous injury, and age for VA injury. Only transverse foramen fracture had significant adjusted OR for VA injury, with none for ICA injury, after FDR correction. Using elastic net, ICA injury variables included maxillofacial fracture, basilar skull fracture, GCS, and carotid canal fracture. For VA injury, these included cervical spine transverse foramen fracture, ligamentous injury, C1-C3 fractures, posterior element fracture, and vertebral body fracture. CONCLUSION: Elastic net statistical learning methods identified additional risk factors and outperformed multiple logistic regression for BCVI. Elastic net allows the study of a large number of variables, and is useful when covariates are correlated.

Magnetic resonance imaging of traumatic injury to the craniovertebral junction: a case-based review.

OBJECT: The craniovertebral junction (CVJ) is unique in the spinal column regarding the degree of multiplanar mobility allowed by its bony articulations. A network of ligamentous attachments provides stability to this junction. Although ligamentous injury can be inferred on CT scans through the utilization of craniometric measurements, the disruption of these ligaments can only be visualized directly with MRI. Here, the authors review the current literature on MRI evaluation of the CVJ following trauma and present several illustrative cases to highlight the utility and limitations of craniometric measures in the context of ligamentous injury at the CVJ. METHODS: A retrospective case review was conducted to identify patients with cervical spine trauma who underwent cervical MRI and subsequently required occipitocervical or atlantoaxial fusion. Craniometric measurements were performed on the CT images in these cases. An extensive PubMed/MEDLINE literature search was conducted to identify publications regarding the use of MRI in the evaluation of patients with CVJ trauma. RESULTS: The authors identified 8 cases in which cervical MRI was performed prior to operative stabilization of the CVJ. Craniometric measures did not reliably rule out ligamentous injury, and there was significant heterogeneity in the reliability of different craniometric measurements. A review of the literature revealed several case series and descriptive studies addressing MRI in CVJ trauma. Three papers reported the inadequacy of the historical Traynelis system for identifying atlantooccipital dislocation and presented 3 alternative classification schemes with emphasis on MRI findings. CONCLUSIONS: Recognition of ligamentous instability at the CVJ is critical in directing clinical decision making regarding surgical stabilization. Craniometric measures appear unreliable, and CT alone is unable to provide direct visualization of ligamentous injury. Therefore, while the decision to obtain MR images in CVJ trauma is largely based on clinical judgment with craniometric measures used as an adjunct, a high degree of suspicion is warranted in the care of these patients as a missed ligamentous injury can have devastating consequences.

Occult spinal dysraphism and urolithiasis: are patients at higher risk of stone disease?

BACKGROUND AND PURPOSE: Spinal dysraphism is associated with urinary-tract dysfunction in severe cases such as meningomyelocele, in part because of incomplete innervation of the lower urinary tract. Patients with meningomyelocele are at higher risk for stone formation, possibly secondary to stasis of urine from aberrant storage and emptying. However, minimal data exist on the risk of stone formation in patients with milder forms of spinal dysraphism. The purpose of this study was to examine whether an association exists between urolithiasis and occult spinal dysraphism (OSD). PATIENTS AND METHODS: All patients who underwent a non-contrast CT scan of the abdomen and pelvis during a 4-month period were included. The final dataset consisted of 374 consecutive patients (195 men, 179 women) with a mean age of 54.2 years (range 18-95 years). Scans were reviewed for evidence of urolithiasis and, independently, for skeletal abnormalities. Patients with urolithiasis included those with a kidney, ureteral, or bladder stone(s). Patients with OSD included those with bifid lumbosacral bony elements, posterior arch defects, or incomplete fusion or non-fusion of S1, S2, or S3. The association between urolithiasis and OSD was examined by calculating series of crude and adjusted odds ratios (ORs) with corresponding 95% confidence intervals (CIs). RESULTS: Of the 374 patients, 135 (36.1%) had urinary calculi, and 83 (22.2%) had OSD. No relation was found between the prevalence of OSD and stone disease (OR 1.22; 95% CI 0.72, 2.08), even after adjusting for potential confounders. CONCLUSION: Unlike severe spinal dysraphism, OSD does not appear to confer an increased risk of stone disease.

The Monro-Kellie Doctrine in Action: Posterior Reversible Leukoencephalopathy Syndrome Caused by Intracranial Hypotension from Lumboperitoneal Shunt Placement.

BACKGROUND: Posterior reversible leukoencephalopathy syndrome (PRES) is linked to various etiologies, including most importantly systemic hypertension. Its association with intracranial hypotension (IH), a potential sequela of various neurosurgical procedures, is underrecognized. We report a case of lumboperitoneal shunt-induced IH resulting in PRES with the goal to increase awareness and elaborate on the potential biologic mechanism, based on the Monro-Kellie hypothesis. CASE DESCRIPTION: A 26-year-old woman with acquired immunodeficiency syndrome and epilepsy was admitted for recurrent cryptococcal meningitis and breakthrough seizures. There was radiologic evidence of ventricular enlargement, and opening pressure on serial lumbar punctures was constantly elevated. Owing to persistently elevated, symptomatic intracranial pressure and transient relief with serial lumbar punctures, a lumboperitoneal shunt was placed. The patient subsequently had a breakthrough seizure and became encephalopathic. Repeat head imaging showed reduced ventricular size, engorged venous sinuses, and tonsillar herniation in keeping with IH, coupled with extensive white matter abnormalities in bilateral parieto-occipital lobes indicative of PRES. The patient had an emergent programmable valve placed in the lumboperitoneal shunt to prevent excessive cerebrospinal fluid drainage, leading to clinical and radiologic improvement. Subsequent cerebrospinal fluid leak resulted in recurrent presentation. CONCLUSIONS: IH appears to be a distinct cause of PRES not previously reported in the neurosurgical literature. It occurs in susceptible patients, on average 1-5 days after the IH trigger, and seems clinically and radiologically similar to more common hypertensive cases in terms of initial presentation and prognosis. Increased vigilance is required for prompt recognition and management.

An astroblastoma mimicking a cavernous malformation: case report.

OBJECTIVE: Astroblastomas are rare glial neoplasms that usually occur in young adults and have a predilection for the cerebral hemispheres. Patients typically present with signs of increased intracranial pressure and seizures. Imaging studies reveal circumscribed, contrast-enhancing tumors that contain both cystic and solid components with variable peritumoral edema. Hemorrhage, which suggested the presence of a vascular lesion in this patient, has not been previously described as a feature of this neoplasm. CLINICAL PRESENTATION: The authors report the case of a 33-year-old woman who presented with spontaneous intraparenchymal hemorrhage. The collective radiographic data suggested the presence of a cavernous malformation. INTERVENTION: A right frontotemporal craniotomy was performed under frameless stereotactic image guidance. An astroblastoma was diagnosed after resection and neuropathological examination. CONCLUSION: A rare radiological to pathological correlation of astroblastoma is presented in which the evolving hematoma, as observed on magnetic resonance imaging scans, complicated the radiographic diagnosis of this lesion. The clinical, radiographic, and pathological features of astroblastomas, as well as the natural history of these rare glial neoplasms, are reviewed. This case illustrates the capacity of astroblastomas to hemorrhage, disguising the classic radiographic findings typical of this glial neoplasm.