OBJECT This study was undertaken to evaluate the impact of postoperative MRI artifact on the assessment of ongoing spinal cord or nerve root compression after anterior cervical discectomy and fusion (ACDF) using a trabecular tantalum cage or bone autograft or allograft. METHODS The authors conducted a retrospective review of postoperative MRI studies of patients treated surgically for cervical disc degenerative disease or cervical instability secondary to trauma. Standard ACDF with either a trabecular tantalum cage or interbody bone graft had been performed. Postoperative MR images were shown twice in random order to each of 3 assessors (2 spine surgeons, 1 neuroradiologist) to determine whether the presence of a tantalum interbody cage and/or anterior cervical fixation plate or screws imparted MRI artifact significant enough to prevent reliable postoperative assessment of ongoing spinal cord or nerve root compression. RESULTS A total of 63 patients were identified. One group of 29 patients received a tantalum interbody cage, with 13 patients (45%) undergoing anterior plate fixation. A second group of 34 patients received bone auto- or allograft, with 23 (68%) undergoing anterior plate fixation. The paramagnetic implant construct artifact had minimal impact on visualization of postoperative surgical level spinal cord compression. In the cage group, 98% (171/174) of the cases were rated as assessable versus 99% in the bone graft group (201/204), with high intraobserver reliability. In contrast, for the assessment of ongoing surgical level nerve root compression, the presence of a tantalum cage significantly decreased visualization of nerve roots to 70% (121/174) in comparison with 85% (173/204) in the bone graft group (p < 0.001). When sequences using turbo spin echo (TSE), a T2-weighted axial sequence, were acquired, nerve roots were rated as assessable in 88% (69/78) of cases; when only axial T2-weighted sequences were available, the nerve roots were rated as assessable in 54% (52/96) of cases (p < 0.01). The presence of anterior plate fixation had minimal impact on visualization of the spinal cord (99% [213/216] for plated cases vs 98% [159/162] for nonplated cases; p = 1.0) or nerve roots (79% [170/216] for plated cases vs 77% [124/162] for nonplated cases; p = 0.62). CONCLUSIONS Interbody fusion with tantalum cage following anterior cervical discectomy imparts significant paramagnetic artifact, which significantly decreases visualization and assessment of ongoing surgical level nerve root, but not spinal cord, compression. Anterior plate constructs do not affect visualization of these structures. TSE T2-weighted sequences significantly improve nerve root visualization and should be performed as part of a standard postoperative protocol when imaging the cervical spine following interbody implantation of materials with potential for paramagnetic artifact.

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Although the common carotid artery is the second most common site for extracranial carotid artery stenosis, complete symptomatic occlusion in the absence of devastating stroke is rare. We present a case of complete common carotid artery occlusion failing medical management and requiring endovascular intervention. The clinical presentation, diagnostic investigations, and management of complete carotid artery occlusions are discussed.

Figure: Correlation plot provides visual representation for the correlation between BtO 2 and other hemodynamic/physiological parameters.Each cell represents the R 2 value for the correlation between BtO 2 and the clinical parameter in the column, for the individual patient in the row.If there is no ellipse, then the correlation coeffi cient is zero.The strength and direction of correlation are dually represented.The increasing strength is represented by the density of the colour as well as by narrowing radius of the ellipse.The direction of the correlation (positive or negative) is represented by the colour of the ellipse (blue = positive correlation; red = negative correlation), as well as its orientation (ellipses angled up and to the right represent positive correlations).The asterisk indicates signifi cant linear correlations (p <0.05).The grey rectangles for patients 1,2,4, and 8 indicate that insuffi cient values were available to calculate the correlation coeffi cient.

Acute ischemic stroke (AIS) remains a devastating and relatively common complication after pediatric ventricular assist device (VAD) placement, with a reported incidence of 29%. We describe an 8-year-old cardiomyopathy patient who had received a HeartWare device, complicated by AIS, and successful treatment with a Solitaire FR device with complete recanalization. This is the first report of the use of this device in a VAD patient and the first reported use in a pediatric patient with middle cerebral artery AIS. (C) 2013 by The Society of Thoracic Surgeons

ORIGINAL ARTICLES 411 A Case-Control Study of Tissue Plasminogen Activator for Acute Ischemic Stroke JM Reid, SJ Phillips, GJ Gubitz, J Jarrett, C Christian, D Dai 417 Myocardial Infarction Following t-PA for Acute Stroke M Mehdiratta, C Murphy, A Al-Harthi, PA Teal 421 A Novel GDAP1 Mutation P78L Responsible for CMT4A Disease in Three Moroccan Families Ahmed Bouhouche, Nazha Birouk, AH Benomar, Reda Ouazzani, Ta'ieb Chkili, Mohamed Yahyaoui 427 Neuromuscular Function in Survivors of the Acute Respiratory Distress Syndrome Michael J Angel, Vera Bril, Patrick Shannon, Margaret S Herridge 433 Reliability of Visual Temporal Thresholds LN Brown, M Eliasziw, LM Metz 438 Clinical Practice Regarding Dopamine-Agonist Use and Driving in Parkinson's Disease RMA de Bie, J Miyasaki, AE Lang, SH Fox 443 PLEDS: Clinical Correlates W Fitzpatrick, N Lowry 451-463 (see contents pages)

STUDY DESIGN:We report on a prospective selective case series of 17 patients with cervical fracture-dislocations treated with closed reduction under MRI guidance. OBJECTIVE:To demonstrate the safe and effective use of in-line axial traction in the reduction of cervical fracture-dislocations using MRI guidance. SUMMARY OF BACKGROUND DATA:Closed reduction of the cervical spine for acute fracture-dislocations has been a traditional technique used for restoring vertebral alignment and providing neural element decompression. The safety of this technique has been questioned, with concerns of disc migration and overdistraction causing neurologic worsening cited as reasons to choose operative reduction and decompression as a safer option in some circumstances. METHODS:Seventeen patients with fracture-dislocations of the subaxial cervical spine were given a trial of traction under MRI guidance between 1999 and 2003. The incidence of posteriorly herniated disc material was noted, and the diameter of the spinal canal at the injured level was recorded before and after traction. RESULTS:All patients tolerated traction without neurologic worsening. Pretraction disc disruption was found in 15 of 17 (88.2%) of patients, with posterior herniation in 4 of 17 (23.5\%). Traction caused a return of herniated disc material toward the disc space in all cases. Canal dimensions improved in 11 of 17 patients, with canal diameter increasing by a factor of 1.1 to 3.0, with a mean improvement of 1.73. The process of reduction was observed to be a gradual one, with progressive, significant improvement in canal dimensions occurring before anatomic realignment. As distracting force was increased, sequential MRIs showed that canal dimensions did not diminish at any time in any patient. CONCLUSIONS:MRI monitoring in closed cervical reduction is a useful research tool for this technique. Closed reduction appears to be safe as used in this preliminary study and is effective in achieving immediate spinal cord decompression.