Seizure Duration and Spread Dynamics in MRI-Defined Subtypes of Temporal Lobe Epilepsy.

BACKGROUND AND OBJECTIVES: MRI and PET imaging enables subgroups of temporal lobe epilepsy (TLE) to be defined on the basis of structural pathology. Few studies have examined the variation in electroclinical seizure spread patterns based on imaging findings. We performed a retrospective cohort study to investigate the electroclinical differences among 3 specific groups of TLE: MRI-negative PET-positive TLE (MRI-negative TLE), temporal lobe lesion TLE (lesional TLE), and unilateral hippocampal sclerosis TLE (HS-TLE). METHODS: Patients with an electroclinical diagnosis of TLE who had video-scalp EEG recordings of seizures were identified from the retrospective database of the Austin Comprehensive Epilepsy Program between 2005 and 2019. The cohort was further selected into the 3 defined groups based on imaging findings, using MRI and FDG-PET. Timings of clinical and electrographic seizure progression were measured, considering the onset, ipsilateral lobar spread, contralateral spread, and termination. Durations were compared between groups using linear mixed models with inclusion of demographic and clinical covariates. RESULTS: A total of 105 patients (137 seizures) were included, comprising 36 with MRI-negative TLE (54 seizures), 36 with lesional TLE (18 lateral vs 16 mesial lesions; 44 seizures), and 33 with HS-TLE (39 seizures). Seizure duration was similar between MRI-negative TLE and lesional TLE (mean 75.9 vs 71.7 seconds; p = 0.91). Further dividing lesional TLE into medial vs lateral temporal revealed no timing difference. However, the HS-TLE group had longer total seizure duration (114 seconds) compared with both MRI-negative TLE (p < 0.001) and lesional TLE (p < 0.001). Progression of electrographic spread also reflected this pattern, with involvement of extratemporal regions and then the contralateral hemisphere each taking significantly longer in HS-TLE. DISCUSSION: MRI-negative TLE appears electrographically similar to lesional TLE, whether mesial or lateral, in the duration of seizures and the timing of electrographic spread. Both appear electrographically different from HS-TLE, where propagation is slower, suggesting engagement of different epileptogenic networks or seizure suppression mechanisms. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that the electroclinical features of seizures in HS-TLE are different than MRI-negative TLE and lesional TLE.

Intraoperative definition of bottom-of-sulcus dysplasia using intraoperative ultrasound and single depth electrode recording - A technical note.

Bottom of sulcus dysplasias (BOSDs) are localized focal cortical dysplasias (FCDs) centred on the bottom of a sulcus that can be highly epileptogenic, but difficult to delineate intraoperatively. We report on a patient with refractory epilepsy due to a BOSD, successfully resected with the aid of a multimodal surgical approach using neuronavigation based on MRI and PET, intraoperative ultrasound (iUS) and electrocorticography (ECoG) using depth electrodes. The lesion could be visualized on iUS showing an increase in echogenicity at the grey-white matter junction. IUS demonstrated the position of the depth electrode in relation to the lesion. Depth electrode recording showed almost continuous spiking. Thus, intraoperative imaging and electrophysiology helped confirm the exact location of the lesion. Post-resection ultrasound demonstrated the extent of the resection and depth electrode recording did not show any epileptiform activity. Thus, both techniques helped assess completeness of resection. The patient has been seizure free since surgery. Using a multimodal approach including iUS and ECoG is a helpful adjunct in surgery for BOSD and may improve seizure outcome.

Noncontrast Hybrid Arterial Spin-Labeled Imaging of the Intracranial Arteries.

OBJECTIVE: The purpose of this study is to evaluate feasibility, image quality (IQ), and accuracy of noncontrast hybrid arterial spin labeling (NoHASL) magnetic resonance angiography (MRA) compared with time of flight (TOF) MRA and contrast-enhanced (CE) MRA in patients with known/suspected cerebrovascular ischemia. METHODS: Thirty inpatients were imaged at 1.5 T. Two neuroradiologists assessed 630 intracranial arterial segments for IQ (1, nondiagnostic; 3, satisfactory for diagnosis; and 5, excellent). Hemodynamically significant stenosis (>50%) was assessed against all combined techniques as reference. RESULTS: The NoHASL MRA IQ was diagnostic (3.32 ± 0.86) but affected by signal to noise ratio and spatial resolution limitations and significantly inferior to TOF (3.48 ± 0.68) and CE MRA (3.44 ± 0.78) (P < 0.0001 in both comparisons). Fourteen (2.2%) of 630 segments had hemodynamically significant stenoses at the reference standard. Sensitivity/specificity was not significantly different between techniques: NoHASL MRA, 67.9%/90.0%; TOF MRA, 67.9%/97.7%; and CE MRA, 50.0%/98.7%. CONCLUSIONS: The NoHASL MRA is feasible, with diagnostic quality imaging of proximal intracranial vessels. Low disease prevalence limited the assessment of technique accuracy.

Correlation between pedicle size and the rate of pedicle screw misplacement in the treatment of thoracic fractures: Can we predict how difficult the task will be?

STUDY DESIGN: A retrospective study. OBJECTIVE: To correlate the incidence of pedicle-screw (PS) misplacement with the dimensions of the pedicles in the treatment of thoracic spine fractures. SUMMARY OF BACKGROUND DATA: The technical challenge of internal fixation with PS in the thoracic spine has been well documented in the literature. However, there are no publications that document the correlation between the pedicle dimensions of the thoracic vertebrae in the preoperative computed tomography scans (CT) and the rate of PS misplacement. METHODS: All patients who had PSs inserted between the T1 and T12 vertebrae during a 24-month period were included in this study. PS position was assessed on high quality CT scans by two independent observers and classified in 2 categories: correct or misplaced. The transverse diameter, craniocaudal diameter and cross-sectional area of the pedicles from T1 to T12 were measured in the pre-operative CT. RESULTS: During the period of this study 36 patients underwent internal fixation with 218 PS. Of the 218 screws, 184 (84.5%) were correct and 34 (15.5%) were misplaced. Misplacement rate was 33% for pedicles with a transverse diameter less than 5 mm, 10.7% for those with a transverse diameter between 5 and 7 mm and 0% for those with a transverse diameter larger than 7 mm. There was a statistically significant difference in the rate of PS misplacement in pedicles with transverse diameter smaller than 5 mm compared with the others. Also, those with transverse diameter between 5.1 and 7 mm compared with those bigger than 7 mm in diameter. The rate of PS misplacement was higher between T3 and T9 (p < 0.05), which in turn correlated with pedicle transverse diameter. CONCLUSION: The rate of PS misplacement in the mid thoracic spine (T4-T9) is high and correlates with pedicle transverse diameter.

The surgically remediable syndrome of epilepsy associated with bottom-of-sulcus dysplasia.

OBJECTIVE: To determine clinical and EEG features that might help identify patients with epilepsy harboring small, intrinsically epileptogenic, surgically treatable, bottom-of-sulcus dysplasias (BOSDs). METHODS: Retrospective review of clinical records, EEG, MRI, and histopathology in 32 patients with drug-resistant epilepsy and MRI-positive (72% 3.0 tesla), pathologically proven (type 2B cortical dysplasia) BOSDs operated at our centers during 2005-2013. RESULTS: Localization of BOSDs was frontal in 19, insula in 5, parietal in 5, and temporal in 3, on the convexity or interhemispheric surfaces. BOSDs were missed on initial MRI at our centers in 22% of patients. Patients presented with focal seizures during infancy in 9, preschool years in 15, and school years in 8 (median age 5 years). Seizures were stereotyped, predominantly nocturnal, and typically nonconvulsive, with semiology referable to the fronto-central or perisylvian regions. Seizures occurred at high frequency during active periods, but often went into prolonged remission with carbamazepine or phenytoin. Intellect was normal or borderline, except in patients with seizure onset during infancy. Scalp EEG frequently revealed localized interictal epileptiform discharges and ictal rhythms. Patients underwent lesionectomy (median age 14 years) guided by electrocorticography and MRI, with prior intracranial EEG monitoring in only one patient. Twenty-eight patients (88%) became seizure-free, and 20 discontinued antiepileptic medication (median follow-up 4.1 years). CONCLUSIONS: In patients with cryptogenic focal epilepsy, this clinical presentation and course should prompt review of or repeat MRI, looking for a BOSD in the frontal, parietal, or insula cortex. If a BOSD is identified, the patient might be considered for single-stage lesionectomy.

Lymphoma of the trigeminal nerve--the need for histological diagnosis.

CNS lymphoma involving the trigeminal nerve is a rare condition which presents as a cavernous sinus lesion. It may mimic the radiological appearance of other lesions, and biopsy is essential before considering empirical radiotherapy for lesions in this region. We report the radiological, histopathological and operative findings of a primary non Hodgkin B cell lymphoma involving the trigeminal nerve.

Etiology of hippocampal sclerosis: evidence for a predisposing familial morphologic anomaly.

OBJECTIVE: We sought evidence of a hereditary component for hippocampal sclerosis (HS) by determining whether close relatives of probands with temporal lobe epilepsy (TLE) with HS also had asymptomatic HS or subtle variation in hippocampal morphology. METHODS: First-degree relatives from 15 families in which probands had TLE with HS and 32 age- and sex-matched controls were included in the study. Left and right hippocampal volumes and T2 relaxometry were measured using 3-tesla MRI. RESULTS: Thirty-two asymptomatic first-degree relatives and 3 relatives with a history of seizures or epilepsy were studied. None of the first-degree relatives had HS on visual analysis and T2 relaxation times were normal, excluding the presence of HS. Mean hippocampal volume was smaller (6.4%) in asymptomatic relatives (2.94 ± 0.27 cm(3), 95% confidence interval = 2.87-3.01) than in controls (3.14 ± 0.22 cm(3), 95% confidence interval = 3.09-3.19, p < 0.005); the effect was greater in relatives of probands with a positive family history of epilepsy. The relatives also had more asymmetric hippocampi (asymmetric index 0.92 ± 0.05) than controls (0.96 ± 0.03, p = 0.001). CONCLUSIONS: Small asymmetric hippocampi in healthy relatives are likely to represent a familial developmental variant that may predispose to the formation of TLE with HS. The underlying histopathology of these small hippocampi is unknown. This observation may provide an imaging marker for future studies seeking susceptibility genes for HS.

Outcomes at 12 months after early magnetic resonance imaging in acute trauma patients with persistent midline cervical tenderness and negative computed tomography.

STUDY DESIGN: A prospective observational cohort study of alert, neurologically intact trauma patients presenting to the emergency department with midline cervical tenderness. Screening cervical magnetic resonance imaging (MRI) had been conducted after negative computed tomography (CT) when tenderness was persistent. OBJECTIVE: To determine the association of acute findings and demographic characteristics with any long-term neck disability, and with time to return to work in such patients. SUMMARY OF BACKGROUND DATA: The relationship between acute findings and outcomes in these patients is unknown, and we hypothesized that outcomes at 12 months would correlate with acute clinical signs and symptoms, MRI findings, and mechanisms of injury. METHODS: Patients at a Level 1 trauma center with persistent midline cervical tenderness in the absence of evidence of intoxication, painful distracting injury, persistently abnormal neurology, or acute CT findings, who underwent early cervical MRI under the institutional protocol, were reviewed in the outpatient spine clinic after discharge. In addition, the factors associated with neck disability and time to return to work were examined at follow-up at 12 months after presentation. RESULTS: There were 162 of 178 patients available for follow-up at 12 months (91%). Of these, 46% had MRI-identified cervical spine injury at their initial examination, and 22% had required clinical management, including 2.5% with operative stabilization. Neck disability was present in 43% of patients and was associated with depressive symptoms, workers' compensation, and low annual income. Delay in return to work was associated with the presence of minor limb/other fractures and depressive symptoms, whereas patients on high annual incomes were found to return to work more quickly. CONCLUSION: Surprisingly in these acute trauma patients, MRI-detected injury, clinical factors, and injury mechanism were not found to be associated with long-term patient outcomes. As a result, a trial of a more targeted, individual return to work plan, including strategies aimed at improving physical and psychological function, may now be justified to optimize long-term recovery, reduce health resource costs, and maximize economic productivity through early return to work.

Health resource utilisation costs in acute patients with persistent midline cervical tenderness following road trauma.

INTRODUCTION: The costs associated with patients discharged with isolated clinician-elicited persistent midline tenderness and negative computed tomography (CT) findings have not been reported. Our aim was to determine the association of acute and post-acute patient and injury characteristics with health resource costs in such patients following road trauma. METHODS: In a prospective cohort study, road trauma patients presenting with isolated persistent midline cervical tenderness and negative CT, who underwent additional acute imaging with MRI, were recruited. Patients were reviewed in the outpatient spine clinic following discharge, and were followed up at 6 and 12 months post-trauma. Multivariate linear regression was used to assess the association of injury mechanism, clinical assessment, socioeconomic factors and outcome findings with health resource costs generated in the acute hospital and post-acute periods. RESULTS: There were 64 patients recruited, of whom 24 (38%) had cervical spine injury detected on MRI. Of these, 2 patients were managed operatively, 6 were treated in cervical collars and 16 had the cervical spine cleared and were discharged. At 12 months, there were 25 patients (44%) with residual neck pain, and 22 (39%) with neck-related disability. The mean total cost was AUD $10,153 (SD=10,791) and the median was $4015 (IQR: 3044-6709). Transient neurologic deficit, which fully resolved early in the emergency department, was independently associated with higher marginal mean acute costs (represented in the analysis by the ß coefficient) by $3521 (95% CI: 50-6880). Low education standard (ß coefficient: $5988, 95% CI: 822-13,317), neck pain at 6 months (ß coefficient: $4017, 95% CI: 426-9254) and history of transient neurologic deficit (ß coefficient: $8471, 95% CI: 1766-18,334) were associated with increased post-acute costs. CONCLUSION: In a homogeneous group of road trauma patients with non fracture-related persistent midline cervical tenderness, health resource costs varied considerably. As long term morbidity is common in this population, a history of resolved neurologic deficit may require greater intervention to mitigate costs. Additionally, adequate communication between acute and community care providers is essential in order to expedite the recovery process through early return to normal daily activities.

Cervical spine magnetic resonance imaging in alert, neurologically intact trauma patients with persistent midline tenderness and negative computed tomography results.

STUDY OBJECTIVE: We aim to determine the prevalence and factors associated with cervical discoligamentous injuries detected on magnetic resonance imaging (MRI) in acute, alert, neurologically intact trauma patients with computed tomography (CT) imaging negative for acute injury and persistent midline cervical spine tenderness. We present the cross-sectional analysis of baseline information collected as a component of a prospective observational study. METHODS: Alert, neurologically intact trauma patients presenting to a Level I trauma center with CT negative for acute injury, who underwent MRI for investigation of persistent midline cervical tenderness, were prospectively recruited. Deidentified images were assessed, and injuries were identified and graded. Outcome measures included the presence and extent of MRI-detected injury of the cervical ligaments, intervertebral discs, spinal cord and associated soft tissues. RESULTS: There were 178 patients recruited during a 2-year period to January 2009. Of these, 78 patients (44%) had acute cervical injury detected on MRI. There were 48 single-column injuries, 15 two-column injuries, and 5 three-column injuries. Of the remaining 10 patients, 6 had isolated posterior muscle edema, 2 had alar ligamentous edema, 1 had epidural hematoma, and 1 had atlanto-occipital edema. The injuries to 38 patients (21%) were managed clinically; 33 patients were treated in cervical collars for 2 to 12 weeks, and 5 patients (2.8%) underwent operative management, 1 of whom had delayed instability. Ordinal logistic regression revealed that factors associated with a higher number of spinal columns injured included advanced CT-detected cervical spondylosis (odds ratio [OR] 11.6; 95% confidence interval [CI] 3.9 to 34.3), minor isolated thoracolumbar fractures (OR 5.4; 95% CI 1.5 to 19.7), and multidirectional cervical spine forces (OR 2.5; 95% CI 1.2 to 5.2). CONCLUSION: In patients with cervical midline tenderness and negative acute CT findings, we found that a subset of patients had MRI-detected cervical discoligamentous injuries and that advanced cervical spine degeneration evident on CT, minor thoracolumbar fracture, and multidirectional cervical spine forces were associated with increased injury extent. However, a larger study is required to validate which variables may reliably predict clinically important injury in such patients, thereby indicating the need for further radiographic assessment.

Bottom-of-sulcus dysplasia: imaging features.

OBJECTIVE: Dysplasia at the bottom of a sulcus is a subtle but distinct malformation of cortical development relevant to epilepsy. The purpose of this study was to review the imaging features important to the clinical diagnosis of this lesion. MATERIALS AND METHODS: All cases recognized as typical bottom-of-sulcus dysplasia in our comprehensive epilepsy program over the period 2002-2007 were included in the study. RESULTS: In the 20 cases recognized, three major features were identified: cortical thickening at the bottom of a sulcus; a funnel-shaped extension of the lesion toward the ventricular surface, commonly with abnormal signal intensity; and an abnormal gyral pattern related to the bottom-of-sulcus dysplasia, sometimes with a puckered appearance. The pathologic features of the resected lesions were typical of focal cortical dysplasia. CONCLUSION: Bottom-of-sulcus dysplasia is a distinctive malformation of cortical development that can be diagnosed on the basis of imaging characteristics. Reliable identification of this type of malformation of cortical development is difficult but clinically important because the lesion appears to be highly epileptogenic and because the prognosis for seizure control is excellent after focal resection.

Hippocampal sclerosis and a second focal lesion--how often is it ipsilateral?

PURPOSE: Hippocampal sclerosis (HS) is the most common pathologic finding in intractable temporal lobe epilepsy (TLE). In many patients, HS is accompanied by an extrahippocampal lesion (EHL). We sought to assess the lobar distribution and side of EHLs in relation to HS in a large consecutive series of patients presenting to our epilepsy surgery program. METHODS: The inclusion criterion was the presence of both definite HS and an unequivocal EHL on magnetic resonance imaging (MRI) studies in patients evaluated for potential epilepsy surgery at our tertiary epilepsy center. KEY FINDINGS: Fifty-eight patients were identified over a 7-year period. This represented about one-third of all patients with HS. The mean age was 32 years (SD 18.4), and the mean age of seizure onset 13 years (SD 16.4). Fifty-four percent of the EHLs could be classified as acquired and 36% as developmental. In 98% of patients HS was found on the same side as EHL. SIGNIFICANCE: Our findings support the hypothesis that HS may be a secondary event from seizures generated initially by another focal lesion. However, HS and EHL may also originate from the same insult to the brain.

The learning curve of pedicle screw placement: how many screws are enough?

STUDY DESIGN: A retrospective study. OBJECTIVE: Assess the learning curve of pedicle screw (PS) placement of a Spinal Surgery Fellow (SSF) with no previous experience with the technique. SUMMARY OF BACKGROUND DATA: Recent studies have attempted to identify the learning curve for different surgical procedures to define training requirements. Several authors have described a learning curve for PS placement. However, no one has defined the number of PS necessary to be competent in this skill. METHODS: All patients who had PS inserted by the SSF under the supervision of an Attending Spinal Consultant (ASC) and had adequate postoperative radiographs and computed tomography scans available, were included in this study. PS position was assessed by 2 blinded independent observers using a grading scale. PS placement by the SSF was evaluated by examining the assessed position in chronological groups of 40 screws. RESULTS.: Ninety-four patients underwent internal fixation of the spine with 582 PS. Eight cases (40 screws) were excluded because of lack of imaging studies. Of the 542 screws under evaluation, 320 (59%) were performed by the SSF, 187 (34.5%) by the ASC, and 35 (6.5%) by advanced orthopedic or neurosurgical trainees.The rate of misplaced PS performed by the SSF for the first 80 PS was 12.5% and dropped to 3.4% for the remaining 240 screws, which is a statistically significant difference (P < 0.01). Evaluation of computed tomography of vertebrae with PS placed by the SSF on one side and by the ASC on the other showed that the ASC achieved better placement during the first 80 PS (P < 0.01). However, this difference disappeared in the last 240 (P = 1.00). CONCLUSION: The findings demonstrate a learning curve for PS placement. In this series, the asymptote for this technique for an inexperienced SSF, started after about 80 screws (approximately 25 cases).

Parahippocampal epilepsy with subtle dysplasia: A cause of "imaging negative" partial epilepsy.

PURPOSE: Lesion-negative refractory partial epilepsy is a major challenge in the assessment of patients for potential surgery. Finding a potential epileptogenic lesion simplifies assessment and is associated with good outcome. Here we describe imaging features of subtle parahippocampal dysplasia in five cases that were initially assessed as having imaging-negative frontal or temporal lobe epilepsy. METHODS: We analyzed the clinical and imaging features of five patients with seizures from the parahippocampal region. RESULTS: Five patients had subtle but distinctive magnetic resonance imaging (MRI) abnormalities in the parahippocampal gyrus. This was a unilateral signal abnormality in the parahippocampal white matter extending into gray matter on heavily T(1)- and T(2)-weighted images with relative preservation of the gray-white matter boundary on T(1)-weighted volume sequences. Only one of these patients had typical electroclinical unilateral temporal lobe epilepsy (TLE); one mimicked frontal lobe epilepsy, two showed bitemporal seizures, and one had unlocalized partial seizures. All have had surgery; four are seizure-free (one has occasional auras only, follow-up 6 months to 10 years), and one has a >50% seizure reduction. Histopathologic evaluation suggested dysplastic features in the surgical specimens in all. DISCUSSION: In patients with lesion-negative partial epilepsy with frontal or temporal semiology, or in cases with apparent bitemporal seizures, subtle parahippocampal abnormalities should be carefully excluded. Recognizing the MRI findings of an abnormal parahippocampal gyrus can lead to successful surgery without invasive monitoring, despite apparently incongruent electroclinical features.

Multifocal epilepsy: the role of palliative resection - intractable frontal and occipital lobe epilepsy secondary to radiotherapy for acute lymphoblastic leukaemia.

Patients with multifocal epilepsy are often considered unsuitable for epilepsy surgery. We report an adolescent with intractable frontal and occipital lobe seizures, secondary to complications of treatment for acute lymphoblastic leukaemia as a young child. Chemotherapy and radiotherapy were complicated by bilateral, posterior leukoencephalopathy and later an acquired frontal cerebral cavernous malformation (CCM). Detailed electro-clinical and imaging studies showed multiple, frontal lobe seizures per day with less frequent and non-debilitating, simple, occipital lobe seizures. Focal resection of the frontal CCM abolished the socially-disabling seizures with resultant marked improvement in the patient's quality of life at 12 months. Careful analysis of the type and impact of focal seizures in the setting of multifocal epilepsy may demonstrate that one seizure type is more deleterious to quality of life and may be amenable to surgery. In this situation, the patient may benefit significantly from surgery to resect the more active epileptic focus.

Infected (mycotic) aneurysms: spectrum of imaging appearances and management.

Infected aneurysms are uncommon. The aorta, peripheral arteries, cerebral arteries, and visceral arteries are involved in descending order of frequency. Staphylococcus and Streptococcus species are the most common causative pathogens. Early clinical diagnosis of infected aneurysms is challenging owing to their protean manifestations. Clinically apparent infected aneurysms are often at an advanced stage of development or are associated with complications, such as rupture. Nontreatment or delayed treatment of infected aneurysms often has a poor outcome, with high morbidity and mortality from fulminant sepsis or hemorrhage. Current state-of-the-art imaging modalities, such as multidetector computed tomography and magnetic resonance imaging, have replaced conventional angiography as minimally invasive techniques for detection of infected aneurysms in clinically suspected cases, as well as characterization of infected aneurysms and vascular mapping for treatment planning in confirmed cases. Doppler ultrasonography allows noninvasive assessment for infected aneurysms in the peripheral arteries. Imaging features of infected aneurysms include a lobulated vascular mass, an indistinct irregular arterial wall, perianeurysmal edema, and a perianeurysmal soft-tissue mass. Perianeurysmal gas, aneurysmal thrombosis, aneurysmal wall calcification, and disrupted arterial calcification at the site of the infected aneurysm are uncommon findings. Imaging-guided endovascular stent-graft repair and embolotherapy can be performed in select cases instead of open surgery. Familiarity with the imaging appearances of infected aneurysms should alert the radiologist to the diagnosis and permit timely treatment, which may include endovascular techniques.

Assessment of suitability of thrombolysis in middle cerebral artery infarction: a proof of concept study of a stereologically-based technique.

BACKGROUND: The extent of cerebral ischemia, assessed by the Alberta Stroke Program Early CT Score (ASPECTS) method and unaided visual determination of the CT Summit Criterion, correlates with increased risk of intracerebral hemorrhage following rt-PA administration. Concerns about the accuracy of the unaided visual assessment in the estimation of infarct size and the conservative nature of the ASPECTS method led us to develop a new method (MCAGrid) based on stereological grid counting and a digital atlas of the middle cerebral artery (MCA) infarct territory. METHODS: We tested the hypotheses that the stereological method increases the accuracy of infarct estimation and that the number of patients deemed eligible for thrombolysis is greater with this method than with existing methods. Four experienced radiologists with extensive neuroradiological experience examined the CT images of 19 patients with MCA territory stroke and determined patient eligibility for thrombolysis by: unaided visual determination of the CT Summit Criterion, MCAGrid, and the ASPECTS score. The chi(2) test was used to compare the differences in the number of patients deemed 'eligible' for thrombolysis by the 3 imaging methods. Further, the unaided visual assessment and MCAGrid were compared with volumes calculated following manual segmentation of infarct, and the sensitivity, specificity and positive and negative likelihood ratios for these techniques were calculated. RESULTS: In general, MCAGrid was better than unaided visual assessment in the prediction of >1/3 involvement of the MCA territory by infarct. The number of patients considered as 'eligible' for thrombolysis based on imaging criteria was significantly lower when ASPECTS criteria (15/76) were used than when unaided visual determination of the CT Summit Criterion (32/76; p < 0.01) or MCAGrid (59/76; p < 0.001) criteria were used. CONCLUSION: The choice of methods for rating infarct extent affects the number of patients 'eligible' for thrombolysis significantly. Furthermore, MCAGrid increased the accuracy with which infarct extent was estimated. These results provide justification for a prospective study of this technique in the setting of acute stroke.

Ischemic thresholds for gray and white matter: a diffusion and perfusion magnetic resonance study.

BACKGROUND AND PURPOSE: Although gray matter (GM) and white matter (WM) have differing neurochemical responses to ischemia in animal models, it is unclear whether this translates into differing thresholds for infarction. We studied this issue in ischemic stroke patients using magnetic resonance (MR) techniques. METHODS: MR studies were performed in patients with acute hemispheric ischemic stroke occurring within 24 hours and at 3 months. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and apparent diffusion coefficient (ADC) were calculated. After segmentation based on a probabilistic map of GM and WM, tissue-specific diffusion and perfusion thresholds for infarction were established. RESULTS: Twenty-one patients were studied. Infarction thresholds for CBF were significantly higher in GM (median 34.6 mL/100 g per minute, interquartile range 26.0 to 38.8) than in WM (20.8 mL/100 g per minute; interquartile range 18.0 to 25.9; P<0.0001). Thresholds were also significantly higher in GM than WM for CBV (GM: 1.67 mL/100 g; interquartile range 1.39 to 2.17; WM: 1.19 mL/100 g; interquartile range 0.94 to 1.53; P<0.0001), ADC (GM: 918x10(-6) mm2/s; 868 to 975x10(-6); WM: 805x10(-6); 747 to 870x10(-6); P<0.001), and there was a trend toward a shorter MTT in GM (GM 4.94 s, 4.44 to 5.38; WM 5.15, 4.11 to 5.68; P=0.11). CONCLUSIONS: GM has a higher infarction threshold for CBF, CBV, and ADC than WM in patients within 24 hours of ischemic stroke onset. Hence, when assessing patients for potential therapies, tissue-specific rather than whole-brain thresholds may be a more precise measure of predicting the likelihood of infarction.

The ASPECTS template is weighted in favor of the striatocapsular region.

The extent of cerebral infarction correlates with increased risk of intracerebral hemorrhage (ICH) following recombinant tissue plasminogen activator (rt-PA) administration. The Alberta Stroke Program Early CT Score (ASPECTS) is a widely used, validated method which assesses involvement of 10 selected regions of the MCA territory. An ASPECTS score >7 is associated with a higher risk of ICH following thrombolysis than lower scores. To understand the internal structure of the ASPECTS template better, we estimated the infarct volume corresponding to each region. We hypothesized that, in the ASPECTS scoring system, the striatocapsular region is weighted disproportionally. Four experienced radiologists rated individual ASPECTS regions on subacute CT images (day 5-day 10) of 19 patients with MCA territory stroke. Infarct volume was determined from manual segmentation of infarcts on CT images. Linear regression was used to estimate the regional volume associated with each ASPECTS region. The ASPECTS regions are weighted unequally with the striatocapsular region accounting for 21% of the MCA territory infarct volume. Together, the 10 ASPECTS regions account for approximately 51% of the maximum MCA infarct territory volume. These findings should provide impetus for research to develop a scoring system explicitly based on regional hemorrhage risk as an aid to selecting patients for thrombolysis.