Visualization of vascular compression of the trigeminal nerve with high-resolution 3T MRI: a prospective study comparing preoperative imaging analysis to surgical findings in 40 consecutive patients who underwent microvascular decompression for trigeminal neuralgia.

BACKGROUND: High-resolution three-dimensional (3D) magnetic resonance imaging (MRI) has demonstrated its ability to predict fine trigeminal neurovascular anatomy. OBJECTIVE: To address the predictive value of 3-Tesla (3T) MRI in detecting and assessing features of neurovascular compression (NVC), particularly regarding the degree of compression exerted on the root, in patients who underwent microvascular decompression (MVD) for classic primary trigeminal neuralgia. METHODS: This prospective study includes 40 consecutive patients who underwent MVD for classic primary trigeminal neuralgia. All patients underwent a preoperative 3T MRI with 3D T2-weighted driven equilibrium (DRIVE), 3D time-of-flight (TOF) magnetic resonance angiography (MRA), and 3D T1-weighted gadolinium-enhanced sequences in combination. Evaluations were performed by 2 independent observers and compared with the operative findings. RESULTS: For prediction of NVC, image analysis corresponded with surgical findings in 39 cases. Of the 3 patients in whom image analysis did not show NVC, 2 did not have NVC at the time of intraoperative observation. MRI sensitivity was 97.4% (37/38), and specificity was 100% (2/2). The kappa coefficients (κ) for predicting the offending vessel, its location, and the site of compression were 0.882, 0.813, and 0.942, respectively. Image analysis correctly defined the severity of the compression in 31 of the 37 cases. The κ coefficients predicting the degree of compression were 0.813, 0.833, and 0.852, respectively, for Grades 1 (simple contact), 2 (distortion), and 3 (marked indentation). CONCLUSION: 3T MRI using 3D T2-weighted DRIVE in combination with 3D TOF-MRA and 3D T1-weighted gadolinium-enhanced sequences proved to be reliable in detecting NVC and in predicting the degree of root compression, the outcome being correlated with the latter.

Preoperative demonstration of the neurovascular compression characteristics with special emphasis on the degree of compression, using high-resolution magnetic resonance imaging: a prospective study, with comparison to surgical findings, in 100 consecutive patients who underwent microvascular decompression for trigeminal neuralgia.

PURPOSE: Surgical outcome after microvascular decompression (MVD) for primary trigeminal neuralgia (TN) has been demonstrated as being related to the characteristics of the neurovascular compression (NVC), especially to the degree of compression exerted on the root. Therefore, preoperative determination of the NVC features could be of great value to the neurosurgeon, for evaluation of conflicting nature, exact localization, direction and degree of compression. This study deals with the predictive value of MRI in detecting and assessing features of vascular compression in 100 consecutive patients who underwent MVD for TN. METHODS: The study included 100 consecutive patients with primary TN who were submitted to a preoperative 3D MRI 1.5 T with T2 high-resolution, TOF-MRA, and T1-Gadolinium. Image analysis was performed by an independent observer blinded to the operative findings and compared with surgical data. FINDINGS: In 88 cases, image analysis showed NVC features that coincided with surgical findings. There were no false-positive results. Among 12 patients that did not show NVC at image analysis, nine did not have NVC at intraoperative observation, resulting in three false-negative cases. MRI sensitivity was 96.7% (88/91) and specificity 100% (9/9). Image analysis correctly identified compressible vessel in 80 of the 91 cases and degree of compression in 77 of the 91 cases. Kappa-coefficient predicting degree of root compression was 0.746, 0.767, and 0.86, respectively, for Grades I (simple contact), II (distortion), and III (marked indentation; p < 0.01). CONCLUSION: 3D T2 high-resolution in combination with 3D TOF-MRA and 3D T1-Gadolinium proved to be reliable in detecting NVC and in predicting the degree of the root compression.

Inflammatory response after ischemic stroke: a USPIO-enhanced MRI study in patients.

BACKGROUND AND PURPOSE: The intensity of the inflammatory response may be related to the volume of acute infarction. Ultra-small superparamagnetic particles of iron oxide (USPIO) may enable assessment of neuroinflammation. We aimed to assess whether the intensity of the inflammatory response might be related to the subacute ischemic lesion volume. METHODS: We enrolled patients who presented with acute anterior circulation stroke. MRI was performed at day 0, day 6, and day 9. The MRI protocol included T1-weighted imaging, gradient-echo T2*-weighted imaging, diffusion-weighted imaging, perfusion-weighted imaging and MR angiography. Blood-brain barrier disruption was defined as post-gadolinium enhancement on T1-weighted images. USPIO was administered after day 6 MRI. USPIO enhancement ratios were defined as the ratio between USPIO-related signal volume on day 9 T1-weighted imaging (respectively T2*-weighted imaging) and day 6 diffusion-weighted imaging infarct volume. The relationship between day 6 infarct volume and the enhancement ratio was assessed using Pearson and Spearman correlation tests. RESULTS: The protocol was completed in 10 patients. Signal alterations after USPIO injection was observed in 9/10 patients on day 9 T1-weighted imaging and in 5/10 patients on day 9 T2*-weighted imaging. USPIO-related MRI enhancement was heterogeneous. Lesion volume on day 6 diffusion-weighted imaging had no impact on USPIO enhancement at day 9 according to the Pearson correlation test (P=0.39) or Spearman test (P=0.25). There was no relationship between blood-brain barrier disruption and USPIO enhancement. CONCLUSIONS: USPIO MRI enhancement is heterogeneous and not clearly related to subacute lesion volume.

Evolution of lesion volume in acute stroke treated by intravenous t-PA.

PURPOSE: To determine the evolution of the ischemic lesion volumes in a population treated with tissue plasminogen activator (t-PA), MRIs were performed before treatment and 24 hours later; final infarct size was evaluated 60 days later. MATERIALS AND METHODS: A total of 42 patients with hemispheric stroke were recruited for a thrombolytic study. Intravenous t-PA was given after MRI within the first seven hours after stroke onset. Volumes were evaluated on day 0 and day 1 with diffusion-weighted imaging (DWI), on day 60 with T2-weighted imaging (T2WI), and recanalization was assessed based on day 1 MR angiography (MRA). RESULTS: Lesion volume increased between day 0 and day 1, and decreased between day 1 and day 60. It was lower in the group of patients with recanalization on day 1 MRA. CONCLUSION: Volume analysis emphasizes the effectiveness of recanalization as a predictive factor for better outcome, based on final infarct size. The decrease in lesion volumes between day 1 and day 60 suggests that other factors leads to overestimation of day 1 abnormal diffusion volume. This could explain the delayed partial reversibility of the DWI abnormality.

Cranial sutures and craniometric points detected on MRI.

The main goal of the study was to determine on MRI the cranial sutures, the craniometric points and craniometric measurements, and to correlate these results with classical anthropometric measurements. For this purpose, we reviewed 150 cerebral MRI examinations considered as normal (Caucasian population aged 20-49 years). For each examination we individualized 11 craniometric landmarks (Glabella, Bregma, Lambda, Opisthocranion, Opisthion, Basion, Inion, Porion, Infra-orbital, Eurion) and three measurements. Measurements were also calculated independently on 498 dry crania (Microscribe 3-DX digitizer). To validate the MRI procedure, we measured four dry crania by MRI and with compass or digital caliper gauges. Cranial sutures always appeared without signal (black), whatever the MRI sequence used, and they are better visualized with a 5 mm slice thickness (compact bone overlapping). Slice dynamic analysis and multiplanar reformatting allowed the detection of all craniometric points, some of these being more difficult to detect than others (Porion, Infra-orbital). The measurements determined by these points were as follows: Vertex-Basion height=135.66+/-6.56 mm; Eurion-Eurion width=141.17+/-5.19 mm; Glabella-Opisthocranion length=181.94+/-6.40 mm. On the midline T1-weighted sagittal image, all median craniometric landmarks can be individualized and the Glabella-Opisthocranion length, Vertex-Basion height and parenchyma indices can be calculated. Craniometric points and measurements between these points can be estimated with a standard cerebral MRI examination, with results that are similar to anthropometric data.

Influence of pretreatment MRI parameters on clinical outcome, recanalization and infarct size in 49 stroke patients treated by intravenous tissue plasminogen activator.

We hypothesized that pretreatment magnetic resonance imaging (MRI) parameters might predict clinical outcome, recanalization and final infarct size in acute ischemic stroke patients treated by intravenous recombinant tissue plasminogen activator (rt-PA). MRI was performed prior to thrombolysis and at day 1 with the following sequences: magnetic resonance angiography (MRA), T2*-gradient echo (GE) imaging, diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). Final infarct size was assessed at day 60 by T2-weighted imaging (T2-WI). The National Institutes of Health Stroke Scale (NIHSS) score was assessed prior to rt-PA therapy and the modified Rankin Scale (m-RS) score was assessed at day 60. A poor outcome was defined as a day 60 m-RS score >2. Univariate and multivariate logistic regression analyses were used to identify the predictors of clinical outcome, recanalization and infarct size. Forty-nine patients fulfilled the inclusion criteria. Baseline NIHSS score was the best independent indicator of clinical outcome (p=0.002). A worse clinical outcome was observed in patients with tandem internal carotid artery (ICA)+middle cerebral artery (MCA) occlusion versus other sites of arterial occlusion (p=0.009), and in patients with larger pretreatment PWI (p=0.001) and DWI (p=0.01) lesion volumes. Two factors predict a low rate of recanalization: a proximal site of arterial occlusion (p=0.02) and a delayed time to peak (TTP) on pretreatment PWI (p=0.05). The final infarct size was correlated with pretreatment DWI lesion volume (p=0.025). Recanalization was associated with a lower final infarct size (p=0.003). In conclusion, a severe baseline NIHSS score, a critical level of pretreatment DWI/PWI parameters and a proximal site of occlusion are predictive of a worse outcome after IV rt-PA for acute ischemic stroke.

Magnetic resonance imaging: significance of early ischemic changes on computed tomography.

UNLABELLED: The significance of early ischemic changes (EICs) on CT remains controversial. MRI may provide relevant information in patients with EICs. METHODS: EICs were assessed in patients with acute ischemic stroke. MRI was promptly performed at presentation after CT and repeated on day 1. The relationship between EICs and MRI parameters was assessed with one-way ANOVA for analysis of continuous variables and by the chi2 test for the analysis of variables with a binary outcome. RESULTS: Fourty-eight patients underwent CT and MR imaging before treatment with recombinant tissue plasminogen activator (age: 63 +/- 14 years). EICs were graded as absent in 28 patients, <33% in 15 patients, and >33% of the middle cerebral artery (MCA) territory in 5 patients. NIHSS score was higher in patients with EICs that covered more than one third of the MCA territory (19 +/- 3) compared to those without EICs (12 +/- 5; p = 0.04). Patients who had major EICs had a larger acute lesion volume in diffusion-weighted imaging (DWI; 140 +/- 78 cm3) compared to those without EICs (33 +/- 51 cm3, p < 0.0001). Regional cerebral blood flow, regional cerebral blood volume, time to peak and mean transit time values were not significantly different in the study groups. CONCLUSION: EICs reflect mainly a larger DWI lesion.

Thrombolysis for ischemic stroke in patients with old microbleeds on pretreatment MRI.

BACKGROUND: Old asymptomatic microbleeds (MBs) visualized on T2-weighted MRI are indicative of microangiopathy. They may be a marker of increased risk of intracerebral hemorrhage (ICH) following thrombolysis. However, data regarding this potential risk are limited. METHODS: A retrospective analysis of pretreatment T2-weighted MRI was performed in consecutive stroke patients who received intravenous tissue plasminogen activator (tPA). We aimed to assess the impact of MBs on the risk of cerebral bleeding. The frequency and location of MBs were assessed and compared with the location of ICH after thrombolysis. RESULTS: Forty-four patients were studied. MBs were present on pretreatment MRI in 8 cases (18.2%). At day 1, symptomatic ICH occurred in none of 8 patients with MBs versus 1 of 36 patients without (NS). At day 1, ICH occurred in 3 of 8 patients with MBs versus 10 of 36 patients without (NS). At day 7, symptomatic ICH occurred in 1 of 8 patients with MBs versus 2 of 36 patients without (NS). At day 7, ICH occurred in 5 of 8 patients with MBs versus 12 of 36 patients without (NS). No ICH occurred at the site of an MB. ICH occurred within the ischemic area in all patients who bled. CONCLUSIONS: Our study suggests that stroke patients with a small number of MBs on pretreatment MRI could be treated safely with thrombolysis. Larger prospective studies are needed to address the predictive value of detection of MBs with regard to the risk of tPA-induced ICH.

Hypointense transcerebral veins at T2*-weighted MRI: a marker of hemorrhagic transformation risk in patients treated with intravenous tissue plasminogen activator.

Prediction of hemorrhagic transformation (HT) in patients treated by intravenous recombinant tissue-type plasminogen activator (rt-PA) is a challenging issue in acute stroke management. HT may be correlated with severe hypoperfusion. Signal changes may be observed at susceptibility-weighted magnetic resonance imaging (MRI) within large perfusion defects. A signal drop within cerebral veins at T2*-weighted gradient-echo MRI may be expected in severe ischemia, and may indicate subsequent risk of HT. The authors prospectively searched for an abnormal visibility of transcerebral veins (AVV) within the ischemic area in patients with hemispheric ischemic stroke, before they were treated with intravenous rt-PA therapy. Any correlation between AVV and baseline clinical or MRI findings, or further HT, was noted. An AVV was present in 23 of 49 patients (obvious, n = 8; moderate, n = 15), and was supported by severe hemodynamic changes at baseline MRI. The AVV was correlated with the occurrence of parenchymal hematoma type 2 at computed tomography during the first week (r = 0.44, P = 0.002). Five of six type 2 parenchymal hematomas occurred in association with obvious AVV. At multiple regression analysis, two baseline MRI factors had an independent predictive value for HT risk during the first week: the AVV and the cerebral blood volume ratio (Nagelkerke R2 = 0.48).

Early magnetic resonance imaging prediction of arterial recanalization and late infarct volume in acute carotid artery stroke.

In patients with acute ischemic stroke, early recanalization may save tissue at risk for ischemic infarction, thus resulting in smaller infarcts and better clinical outcome. The hypothesis that clinical and diffusion- and perfusion-weighted imaging (DWI, PWI) parameters may have a predictive value for early recanalization and final infarct size was assessed. Twenty-nine patients were prospectively enrolled and underwent sequential magnetic resonance imaging (1) within 6 hours from hemispheric stroke onset, before thrombolytic therapy; (2) at day 1; and (3) at day 60. Late infarct volume was assessed by T2 -weighted imaging. At each time, clinical status was assessed by the National Institutes of Health Stroke Scale (NIHSS). Twenty-eight patients had arterial occlusion at day 0 magnetic resonance angiography (MRA). They were classified into two groups according to day 1 MRA: recanalization (n = 18) versus persistent occlusion (n = 10). Any significant differences between these groups were assessed regarding (1) PWI and DWI abnormality volumes, (2) relative and absolute time-to-peak (TTP) and apparent diffusion coefficient within the lesion on DWI; and (3) day 60 lesion volume on T2 -weighted imaging. Univariate and multivariate logistic regression analysis showed that the most powerful predictive factors for recanalization were lower baseline NIHSS score and lower baseline absolute TTP within the lesion on DWI. The best predictors of late infarct size were day 0 lesion volume on DWI and day 1 recanalization. Early PWI and DWI studies and day 1 MRA provide relevant predictive information on stroke outcome.