Machine Learning in Differentiating Gliomas from Primary CNS Lymphomas: A Systematic Review, Reporting Quality, and Risk of Bias Assessment

BACKGROUND

Differentiating gliomas and primary CNS lymphoma represents a diagnostic challenge with important therapeutic ramifications. Biopsy is the preferred method of diagnosis, while MR imaging in conjunction with machine learning has shown promising results in differentiating these tumors.

PURPOSE

Our aim was to evaluate the quality of reporting and risk of bias, assess data bases with which the machine learning classification algorithms were developed, the algorithms themselves, and their performance.

DATA SOURCES

Ovid EMBASE, Ovid MEDLINE, Cochrane Central Register of Controlled Trials, and the Web of Science Core Collection were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

STUDY SELECTION

From 11,727 studies, 23 peer-reviewed studies used machine learning to differentiate primary CNS lymphoma from gliomas in 2276 patients.

DATA ANALYSIS

Characteristics of data sets and machine learning algorithms were extracted. A meta-analysis on a subset of studies was performed. Reporting quality and risk of bias were assessed using the Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis (TRIPOD) and Prediction Model Study Risk Of Bias Assessment Tool.

DATA SYNTHESIS

The highest area under the receiver operating characteristic curve (0.961) and accuracy (91.2%) in external validation were achieved by logistic regression and support vector machines models using conventional radiomic features. Meta-analysis of machine learning classifiers using these features yielded a mean area under the receiver operating characteristic curve of 0.944 (95% CI, 0.898-0.99). The median TRIPOD score was 51.7%. The risk of bias was high for 16 studies.

LIMITATIONS

Exclusion of abstracts decreased the sensitivity in evaluating all published studies. Meta-analysis had high heterogeneity.

CONCLUSIONS

Machine learning-based methods of differentiating primary CNS lymphoma from gliomas have shown great potential, but most studies lack large, balanced data sets and external validation. Assessment of the studies identified multiple deficiencies in reporting quality and risk of bias. These factors reduce the generalizability and reproducibility of the findings.

Imaging of Neuromodulation and Surgical Interventions for Epilepsy

About one-third of epilepsy cases are refractory to medical therapy. During the past decades, the availability of surgical epilepsy interventions has substantially increased as therapeutic options for this group of patients. A wide range of surgical interventions and electrophysiologic neuromodulation techniques are available, including lesional resection, lobar resection, thermoablation, disconnection, multiple subpial transections, vagus nerve stimulation, responsive neurostimulation, and deep brain stimulation. The indications and imaging features of potential complications of the newer surgical interventions may not be widely appreciated, particularly if practitioners are not associated with comprehensive epilepsy centers. In this article, we review a wide range of invasive epilepsy treatment modalities with a particular focus on their postoperative imaging findings and complications. A state-of-the-art treatment algorithm provides context for imaging findings by helping the reader understand how a particular invasive treatment decision is made.

Choroid plexus changes after temporal lobectomy

BACKGROUND AND PURPOSE

Postoperative contrast-enhanced MR imaging of the brain is routinely used when evaluating for residual or recurrent brain tumor. It is imperative to be aware of morphologic changes and imaging features that typically occur in response to surgical manipulation at the postoperative site to avoid misinterpretation of imaging findings. Our purpose was to determine normal postoperative changes and alterations in the choroid plexus among patients who had undergone temporal lobectomy in order to distinguish this appearance from pathologic changes that may be seen in the presence of infection or recurrent tumors.

METHODS

We reviewed 159 MR scans from 95 patients with hippocampal sclerosis or gliosis who underwent temporal lobectomy for treatment of intractable epilepsy. Choroid plexus location and size were assessed on contrast-enhanced T1-weighted images.

RESULTS

After temporal lobectomy, the choroid plexus enlarged and sagged into the resection site. Increase in the size of the choroid plexus occurred in 58% of cases overall. The degree of enhancement also increased after surgery, sometimes resulting in a nodular pattern of enhancement. The changes were most marked during the 1st week after temporal lobectomy, and showed an enlarged, markedly enhancing choroid plexus on 86% of the scans.

CONCLUSION

Postoperative changes of the choroid plexus after temporal lobectomy include sagging into the resection site, an increased size, and an increased degree of enhancement. Normal postoperative morphologic characteristics may mimic neoplastic enhancement pattern. Familiarity with this appearance is important to avoid a pitfall in diagnosis of recurrent postoperative temporal lobe neoplasms.

Effects of cell volume fraction changes on apparent diffusion in human cells

Diffusion-weighted imaging was used to study the relationship between apparent diffusion coefficient (ADC) and cell volume fraction in cell suspensions and packed arrays. Cell volume fraction was varied by changing extracellular fluid osmolarity (for human glial cells) and by changing cell density (for human glial and red blood cells). In packed arrays of glial cells, ADC increased 10% when cells shrank and decreased 13% when cells swelled. ADC decreased 34% as cell density increased from 0 to 72%. In erythrocyte suspensions, ADC decreased 90% as the cell density increased from 0 to 89%. These results agree with theoretical predictions.

Cerebrospinal fluid cleft with cortical dimple: MR imaging marker for focal cortical dysgenesis

PURPOSE

To determine whether the magnetic resonance (MR) imaging feature of a cerebrospinal fluid (CSF) cleft and cortical dimple can be used as a marker for cortical dysgenesis.

MATERIALS AND METHODS

MR images in 875 patients with epilepsy were evaluated for the following features of focal cortical dysgenesis: cortical thickening, indistinct junction between gray and white matter, macrogyria, and abnormal sulcal pattern. Images with these features were reevaluated to determine the relationship between the CSF cleft-cortical dimple complex and focal cortical dysgenesis and its contribution to diagnosis. The cleft-dimple complex was defined as a prominent CSF space associated with a region of cortical volume loss adjacent to the dysgenesis.

RESULTS

Seventy-one patients had cortical dysgenesis, including 27 with cellular proliferation abnormalities, 18 with migration abnormalities, 25 with cortical organization abnormalities, and one with miscellaneous anomalies. Histologic correlation was available in 20 patients. There was an associated cortical dimple in 29 (41%) patients. This association was strongest in patients with cortical organization abnormalities: It was present in 22 of the 25 (88%) patients. In 12 (48%) patients with abnormalities of cortical organization, the CSF cleft was easier to detect than other features of cortical dysgenesis or contributed directly to the MR imaging diagnosis.

CONCLUSION

The cleft-dimple complex is a marker for subtle cases of focal cortical dysgenesis and may be due to maldevelopment. In patients with seizures, the presence of a cleft-dimple complex should alert the physician to scrutinize adjacent regions for developmental anomalies.

MR imaging and histologic features of subinsular bright spots on T2-weighted MR images: Virchow-Robin spaces of the extreme capsule and insular cortex

PURPOSE

To determine the cause and frequency of high-signal-intensity foci detected in the insular cortex and extreme capsule on thin-section, high-spatial-resolution, coronal, T2-weighted magnetic resonance (MR) images.

MATERIALS AND METHODS

The authors assessed high-signal-intensity areas in the insular cortex and extreme capsule on coronal MR images obtained in 56 patients with seizure and five control subjects. Images were obtained with thin-section, high-spatial-resolution, T2-weighted, fast spin-echo; three-dimensional, spoiled gradient-recalled-echo; and fluid-attenuated inversion-recovery sequences. In two formalin-fixed brain specimens, MR imaging findings were correlated with gross anatomic and histologic findings.

RESULTS

Subinsular bright spots were found in 53 of the 56 (95%) patients (96 of 112 [86%] hemispheres) and all five control subjects. The spots were elliptical in 30 patients, round in 14 patients, linear in 22 patients, and dotlike in seven patients and often had a featherlike configuration. The spots were isointense to cerebrospinal fluid on T2-weighted, fast SE images and were located in the anterior extreme capsule white matter and insular cortex. MR imaging of brain specimens revealed bilateral elliptical areas of high signal intensity that corresponded to small multiple cavities at gross anatomic inspection. At microscopic examination, these cavities were perivascular spaces of mostly arteriolar origin.

CONCLUSION

High-signal-intensity subinsular foci at MR imaging are due to enlarged perivascular spaces. In most cases, these foci can be visualized on thin-section, high-spatial-resolution, coronal T2-weighted images; they should not be mistaken for pathologic conditions when they occur unilaterally.

MR imaging of implanted depth and subdural electrodes: is it safe?

This study evaluates the safety of imaging chronic epilepsy patients with intracranial depth and subdural electrodes by magnetic resonance (MR). To identify an epileptogenic focus, the precise location of the electrode contacts is necessary, and MR can provide this information. However, many neurosurgeons and neuroradiologists are hesitant to scan patients by MR with these implanted, metallic electrodes for fear of electrode displacement, current induction or heating secondary to the strong magnetic field. In the present study, the subdural electrodes were made of stainless steel with either stainless steel or platinum contacts. The depth electrodes were made of either platinum or a nickel-chromium alloy (nichrome). We reviewed 98 cases in which patients with implanted depth electrodes, subdural electrodes, or both underwent MR scanning. A total of 143 depth electrodes, 688 subdural strips, and 38 subdural grids were implanted in the 98 procedures. MR scanning was performed on a 1.5-T unit and consisted of T1, T2, and/or spoiled gradient echo pulse sequences. There were no documented complications related to the MR scans. Based on this study and a review of the literature, we feel that MR imaging can safely localize intracranial electrodes.

Surgical outcome in occipital lobe epilepsy: implications for pathophysiology

Medically refractory occipital lobe epilepsies are increasingly treated with surgery, but outcome and its relationship to etiology, pathological substrate, occipital lobe location, surgical approach, and electroclinical features have not been systematically investigated in a substantial group of patients. Thirty-five patients who underwent surgery for intractable occipital lobe seizures were retrospectively evaluated. Outcome and occipital lobe location were analyzed with respect to surgical procedure, pathology, clinical seizure characteristics, seizure onset and termination locations, and localization of interictal spikes. Most patients had developmental abnormalities (14) or tumors (13, all gliomas). Developmental abnormalities consisted of focal cortical dysplasia (5), heterotopia (2), hamartoma (3), cortical duplication (1), polymicrogyria (1), Sturge-Weber syndrome (1), and tuberous sclerosis (1). There was 1 patient with a vascular abnormality, 1 with chronic inflammatory changes, 4 with gliosis, 1 with cerebral ossification, and 1 with normal pathology. Developmental abnormalities had significantly worse outcome (45% excellent/good) than tumors (85% excellent/good). In the developmental group, low-grade focal cortical dysplasias had better outcome than heterotopia and hamartoma regardless of type of surgical procedure. Pathological groups did not significantly differ with respect to location within the occipital lobe (overall medial [50%] or lateral [38%]); clinical seizure characteristics referable to specific lobe (occipital [14%], temporal [34%], frontal [23%], more than one type [29%]); electroencephalographic localization (to occipital [17%], temporal [27%], or other/multifocal locations [56%]); or intracranial ictal onset or termination location. Electroclinical variables were also unrelated to the occipital lobe location of abnormality. Surgical outcome was not predicted by surgical approach (lesion excision with margins or lobectomy). The main pathological substrates of uncontrolled occipital lobe epilepsy are gliomas and developmental abnormalities. Whereas resection of occipital lobe tumors associated with chronic epilepsy produces nearly uniform seizure control, outcome after resection of occipital lobe developmental abnormalities is less uniform.

Topographic distribution of seizure onset and hippocampal atrophy: relationship between MRI and depth EEG

Medial temporal lobe epilepsy (MTLE) is associated with hippocampal cell loss and organization of the dentate gyrus. Some studies suggest a correlation between the topographic distribution of cell loss and site of epileptogenesis. We studied the relationship between the site of ictal onset with the presence of segmental atrophy in patients with non-lesional MTLE using magnetic resonance imaging (MRI) and depth EEG. Ictal recordings were obtained from 27 patients with longitudinal hippocampal depth electrodes and variable combinations of subdural strips sampling medial temporal structures. The location of the depth electrode contacts was correlated with anatomical landmarks. Seizures were analyzed for the distribution of onset along the long axis of the hippocampus. MRI analysis were performed to detect segmental atrophy. Outcome was assessed 1 year or more following anterior temporal lobectomy. Twenty-five patients had unilateral, and two had bilateral, hippocampal atrophy. One hundred and forty-seven seizures were reviewed: 21 showed focal onset and 126 showed regional onset. Ictal onset involved the amygdala and anterior half of the hippocampus in 80% of the seizures while only 40% of patients had atrophy of these segments. Most patients had excellent outcome. In patients with MTLE the primary area of epileptogenesis does not parallel the hippocampal segments with the greatest degree of volume loss.

Economic impact of replacing CT with MR imaging for refractory epilepsy

PURPOSE

To evaluate the economic costs of using computed tomography (CT) vs. magnetic resonance (MR) imaging in the preoperative evaluation of refractory epilepsy patients.

METHODS

Preoperative CT and MR imaging findings from 117 patients who underwent surgery for medically refractory epilepsy during a 3.5-year period were reviewed. Cost savings were based on the paradigm that intracranial electroencephalogram monitoring (costing about $50,000) would have been necessary for preoperative localization of the epileptogenic zone in those patients without positive imaging findings. Savings attributed to replacing CT with MR were based on patients with positive MR and normal CT. A similar paradigm was used to calculate savings for replacing MR with CT. National savings were based solely on patients with neoplasms or vascular lesions because paradigms for other lesions vary considerable depending on institutional philosophy.

RESULTS

Replacing CT with MR imaging would have eliminated preoperative intracranial electrode procedures in 29 of 117 patients, with potential savings of $1,450,000 at our institution. In the 37 patients with neoplastic or vascular substrates, MR would have eliminated 10 invasive electrode procedures with estimated savings of $0.5 million institutionally and $3 to $4 million per year nationally. There were no cases to support replacing MR with CT.

CONCLUSION

Replacing CT with MR decreases health costs associated with preoperative evaluation of intractable epilepsy requiring surgical amelioration.

Postoperative changes in the brain: MR imaging findings in patients without neoplasms

PURPOSE

To determine the time course of postoperative changes in the brain by using magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Contrast material-enhanced MR images (32 preoperative, 161 postoperative) in 95 patients who underwent temporal lobectomy for treatment of nonneoplastic epilepsy were evaluated for enhancement pattern at the surgical margin and for the presence of dural enhancement, fluid, and air. Images were obtained 9 hours to 5.6 years after surgery.

RESULTS

Surgical margin contrast enhancement was present and increased from 20 hours to 29 days after surgery. The predominant early (days 0-5) pattern was thin linear enhancement (16 of 18 [89%] images). The later (days 6-29) pattern was thick linear or nodular (tumorlike appearance) (11 of 18 [61%] images). Surgical margin enhancement was absent after day 30, although few data were collected 1-5 months after surgery. Dural enhancement was seen on 96 of 97 (99%) postoperative MR images. Extraaxial fluid was seen on all 46 images obtained during the first 30 days and was absent by day 51. Intracranial air was present on 31 of 35 (89%) images obtained during the first 4 days but was absent after day 5.

CONCLUSION

Knowledge of the evolution of contrast enhancement patterns on postoperative MR images of the brain can help in differentiating benign from neoplastic changes.

Qualitative MR imaging of refractory temporal lobe epilepsy requiring surgery: correlation with pathology and seizure outcome after surgery

OBJECTIVE

The purpose of this study was to compare MR imaging findings with histologic findings of either hippocampal sclerosis or gliosis in patients with intractable temporal lobe epilepsy requiring surgery and to correlate MR imaging findings with seizure outcome after surgery and with clinical parameters such as febrile seizure history.

MATERIALS AND METHODS

A retrospective study of MR scans of 66 patients with medically refractory temporal lobe epilepsy requiring surgery was performed. Qualitative diagnosis was done by visual inspection of MR images. MR imaging findings of hippocampal atrophy, signal intensity changes, and segmental findings were correlated with histopathology and with neuronal density. The final MR imaging diagnosis was also correlated with seizure outcome after surgery and with febrile seizure history.

RESULTS

Histologic findings consisted of hippocampal sclerosis in 55 patients and nonspecific gliosis in 11 patients. Two variables, MR imaging findings of hippocampal sclerosis (hippocampal atrophy or signal intensity change) and a febrile seizure history, were significantly associated with hippocampal sclerosis. MR images of nonspecific gliosis usually showed normal findings, although some cases showed mild hippocampal atrophy. When comparing MR imaging findings with histology, our observers achieved sensitivities of 87-98% and specificities of 45-100%. In patients with successful outcomes after surgery, sensitivity ranged from 85% to 98% for MR imaging findings suggesting hippocampal sclerosis, specificity ranged from 17% to 85%, and positive predictive values ranged from 82% to 90%.

CONCLUSION

Qualitative visual analysis of MR images correlates well with histologic findings, febrile seizure history, and seizure outcome after surgery. MR imaging findings and febrile seizure history help differentiate between hippocampal sclerosis and nonspecific gliosis, two similar clinical conditions associated with temporal lobe epilepsy that often have different outcomes after surgery.

A systematic approach for interpreting MR images of the seizure patient

A systematic approach needs to be used to review MR scans in epilepsy patients to avoid the common pitfalls engendered by the subtle nature of many epileptogenic lesions. One should always evaluate the hippocampus regardless of other MR findings to avoid missing dual abnormalities. False-positive and false-negative diagnosis of hippocampal sclerosis can be avoided by evaluating the hippocampus after correcting for head rotation [by assessing the internal auditory canals and atria). Periventricular heterotopia can be successfully diagnosed by systematically studying the periventricular regions, especially those adjacent to the atria of the lateral ventricles. Gray matter lateral to the ventricles (excluding the caudate nucleus) is always an abnormal finding. Sulcal and cortical morphologic abnormalities are particularly difficult to diagnose unless a high index of suspicion is maintained. Cortical thickening is indicative of a developmental anomaly and should be screened in an organized manner. Because epilepsy is generally a cortical process, one must search for subtle cortical abnormalities, including focal atrophic abnormalities and lesions without mass effect. Diligence will offer its own rewards.

Predicting reading performance from neuroimaging profiles: the cerebral basis of phonological effects in printed word identification

This study linked 2 experimental paradigms for the analytic study of reading that heretofore have been used separately. Measures on a lexical decision task designed to isolate phonological effects in the identification of printed words were examined in young adults. The results were related to previously obtained measures of brain activation patterns for these participants derived from functional magnetic resonance imaging (fMRI). The fMRI measures were taken as the participants performed tasks that were designed to isolate orthographic, phonological, and lexical-semantic processes in reading. Individual differences in the magnitude of phonological effects in word recognition, as indicated by spelling-to-sound regularity effects on lexical decision latencies and by sensitivity to stimulus length effects, were strongly related to differences in the degree of hemispheric lateralization in 2 cortical regions.

Positron emission tomography measurement of cerebral metabolic correlates of tryptophan depletion-induced depressive relapse

BACKGROUND

Short-term depletion of plasma tryptophan has been shown to result in depressive relapse in patients with remission of major depression. Positron emission tomography and single photon emission computed tomography studies implicated the dorsolateral prefrontal cortex, orbitofrontal cortex, thalamus, and caudate nucleus in the pathogenesis of depression. The purpose of this study was to measure cerebral metabolic correlates of tryptophan depletion-induced depressive relapse.

METHODS

Patients diagnosed as having major depression (N = 21) who clinically improved with serotonin reuptake inhibitors underwent 2 test days involving tryptophan depletion or placebo, followed 6 hours later by positron emission tomography scanning with fludeoxy-glucose F18. Brain metabolism was compared in patients with (n = 7) and without (n = 14) a tryptophan depletion-induced depressive relapse.

RESULTS

Tryptophan depletion resulted in a decrease in brain metabolism in the middle frontal gyrus (dorsolateral prefrontal cortex), thalamus, and orbitofrontal cortex in patients with a depletion-induced depressive relapse (but not in patients without depletion-induced relapse). Decreased brain metabolism in these regions correlated with increased depressive symptoms. Baseline metabolism was increased in prefrontal and limbic regions in relapse-prone patients.

CONCLUSION

Specific brain regions, including the middle frontal gyrus, thalamus, and orbitofrontal cortex, may mediate the symptoms of patients with major depression.

Predicting reading performance from neuroimaging profiles: the cerebral basis of phonological effects in printed word identification

This study linked 2 experimental paradigms for the analytic study of reading that heretofore have been used separately. Measures on a lexical decision task designed to isolate phonological effects in the identification of printed words were examined in young adults. The results were related to previously obtained measures of brain activation patterns for these participants derived from functional magnetic resonance imaging (fMRI). The fMRI measures were taken as the participants performed tasks that were designed to isolate orthographic, phonological, and lexical-semantic processes in reading. Individual differences in the magnitude of phonological effects in word recognition, as indicated by spelling-to-sound regularity effects on lexical decision latencies and by sensitivity to stimulus length effects, were strongly related to differences in the degree of hemispheric lateralization in 2 cortical regions.

Positron emission tomography measurement of cerebral metabolic correlates of yohimbine administration in combat-related posttraumatic stress disorder

BACKGROUND

We have previously reported an increase in symptoms of anxiety in patients with posttraumatic stress disorder (PTSD) following administration of the beta 2-antagonist yohimbine, which stimulates brain norepinephrine release. Preclinical studies show decreased metabolism in the neocortex and the caudate nucleus with high-dose yohimbine-induced norepinephrine release, but low levels of norepinephrine release result in an increase in metabolism in these areas.

METHODS

We used positron emission tomography and fludeoxyglucose F 18 to measure brain metabolism in Vietnam combat veterans with PTSD (n = 10) and healthy age-matched control subjects (n = 10), following administration of yohimbine (0.4 mg/kg) or placebo in a randomized, double-blind fashion.

RESULTS

Yohimbine resulted in a significant increase in anxiety in the patients with PTSD, but not in healthy subjects. There was a significant difference in brain metabolic response to yohimbine in patients with PTSD compared with healthy subjects in prefrontal, temporal, parietal, and orbitofrontal cortexes. Metabolism tended to decrease in patients with PTSD and increase in healthy subjects following administration of yohimbine.

CONCLUSION

These findings are consistent with our previous hypothesis of enhanced norepinephrine release in the brain with yohimbine in patients with PTSD.

Embryology of the human fetal hippocampus: MR imaging, anatomy, and histology

PURPOSE

To identify changes in the embryology of the hippocampus responsible for its adult anatomy.

METHODS

Ten human fetal specimens ranging from 13 to 24 weeks' gestational age were examined with MR imaging. Dissections and histologic sections of 10 different specimens of similar ages were compared with MR imaging findings.

RESULTS

At 13 to 14 weeks' gestation, the unfolded hippocampus, on the medial surface of the temporal lobe, surrounds a widely open hippocampal sulcus (hippocampal fissure). At 15 to 16 weeks, the dentate gyrus and cornu ammonis have started to infold. The hippocampal sulcus remains open. The parahippocampal gyrus is larger and more medially positioned. The CA1, CA2, and CA3 fields of the cornu ammonis are arranged linearly. The dentate gyrus has a narrow U shape. By 18 to 20 weeks, the hippocampus begins to resemble the adult hippocampus. The dentate gyrus and cornu ammonis have folded into the temporal lobe. The hippocampus and subiculum approximate each other across a narrow hippocampal sulcus. The CA1-3 fields form an arc and the CA4 field has increased in size within the widened arch of the dentate gyrus.

CONCLUSION

MR imaging of fetuses provides a developmental basis for understanding hippocampal anatomy.

Focal cortical dysplasia of Taylor, balloon cell subtype: MR differentiation from low-grade tumors

PURPOSE

To test the hypothesis that focal cortical dysplasia of Taylor (FCDT) can be distinguished from low-grade tumors by means of clinical and MR findings.

METHODS

We examined 10 clinical and 19 MR imaging variables in patients who underwent surgery for intractable epilepsy over an 8-year period. The 54 patients with low-grade glial neoplasms were compared with the eight patients who had balloon cell FCDT.

RESULTS

Statistically significant differences were seen with respect to eight of the MR variables and none of the clinical variables. MR findings suggesting dysplasia rather than tumor included the presence of gray matter thickening associated with a homogeneous hyperintense signal in the subcortical white matter that tapers as it extends to the lateral ventricle. A frontal lobe location favors dysplasia, while a temporal lobe (especially medial temporal lobe) location is more suggestive of a neoplasm.

CONCLUSION

Several MR features help distinguish balloon cell FCDT from neoplasms, especially cortical thickening and a tapered signal to the ventricle. This distinction is important for surgical planning, as the decision to operate and the extent of surgical resection often depend on the presence or absence of neoplastic tissue.

Magnetic resonance imaging-based measurement of hippocampal volume in posttraumatic stress disorder related to childhood physical and sexual abuse--a preliminary report

We have previously reported smaller hippocampal volume and deficits in short-term memory in patients with combat-related posttraumatic stress disorder (PTSD) relative to comparison subjects. The purpose of this study was to compare hippocampal volume in adult survivors of childhood abuse to matched controls. Magnetic resonance imaging was used to measure volume of the hippocampus in adult survivors of childhood abuse (n = 17) and healthy subjects (n = 17) matched on a case-by-case basis for age, sex, race, handedness, years of education, body size, and years of alcohol abuse. All patients met criteria for PTSD secondary to childhood abuse. PTSD patients had a 12% smaller left hippocampal volume relative to the matched controls (p < .05), without smaller volumes of comparison regions (amygdala, caudate, and temporal lobe). The findings were significant after controlling for alcohol, age, and education, with multiple linear regression. These findings suggest that a decrease in left hippocampal volume is associated with abuse-related PTSD.

Three cases of symptom change in Tourette's syndrome and obsessive-compulsive disorder associated with paediatric cerebral malignancies

OBJECTIVE

To correlate behaviour manifestations with tumour location in three children who had Gilles de la Tourette's syndrome (GTS), obsessive-compulsive disorder (OCD), and primary cerebral malignancies.

METHOD

Cases were ascertained from a chart review in a GTS and OCD specialty clinic. For each case the temporal progression of change in neuropsychiatric symptoms was qualitatively correlated with radiographic documentation of tumour progression.

RESULTS

The change in symptom severities during tumour progression and treatment, together with prior neurobiological studies of GTS, suggest that the ventral striatum, corpus callosum, thalamus, and midbrain are potentially important neural substrates in the formation or modulation of tic symptoms. The limbic system, including the hypothalamus and cingulate, and the caudate nucleus, seem to be important in the neurobiology of OCD. All structures are neuroanatomically and functionally related to the corticostriato-thalamocortical circuitry that is thought to subserve symptom generation in both GTS and OCD.

CONCLUSION

Although the malignancies were not likely to have caused the tic and OCD symptoms in these children, the locations of these intracranial lesions provide important clues in identifying brain regions that may contribute to the determination of tic and OCD severities.

Comparison of technetium-99m-HMPAO and technetium-99m-ECD cerebral SPECT images in Alzheimer's disease

SPECT has shown increasing promise as a diagnostic tool in Alzheimer's disease (AD). Recently, a new SPECT brain perfusion agent, 99mTc-ethyl cysteinate dimer (99mTc-ECD) has emerged with purported advantages in image quality over the established tracer, 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO). This research aimed to compare cerebral images for 99mTc-HMPAO and 99mTc-ECD in discriminating patients with AD from control subjects.

METHODS

Twenty-four AD patients (mean age +/- s.d. = 68.9 +/- 8.2 yr) and 13 healthy subjects (68.4 +/- 8.0 yr) were scanned sequentially with 20 mCi of each tracer using the CERASPECT system within 1 mo. Scanning began on average 11.5 +/- 2.8 min after 99mTc-HMPAO injection and 41.8 +/- 10.1 min after 99mTc-ECD. A ratio, R, was derived of count densities in "typically affected" brain structures (parietal and temporal association cortices) to "unaffected" structures (cerebellum, basal ganglia, thalamus, occipital cortex, and sensorimotor cortex).

RESULTS

Analysis of variance revealed significant interaction between diagnostic group and radiopharmaceutical (F = 4.71; df = 1.35; p = 0.04), with 99mTc-ECD demonstrating better separation of R values between AD patients and control subjects than 99mTc-HMPAO. Receiver operating characteristic (ROC) analysis, revealed no significant difference in the ability of the two tracers to correctly classify AD patients and control subjects. Both tracers showed high diagnostic accuracy (99mTc-ECD: sensitivity = 100%, specificity = 92%; 99mTc-HMPAO: sensitivity = 100%, specificity = 85%).

CONCLUSION

Technetium-99m-ECD shows greater contrast than 99mTc-HMPAO between affected and unaffected brain structures in AD when patients are compared to age-matched control subjects. Both tracers perform equally well in correctly classifying patients and control subjects.

Refractory epilepsy: comparison of MR imaging, CT, and histopathologic findings in 117 patients

PURPOSE

We compared computed tomography (CT) and magnetic resonance (MR) imaging for the detection of abnormalities underlying epilepsy.

MATERIALS AND METHODS

CT and MR imaging findings in 117 patients (56 female, 61 male patients; age at surgery, 12-56 years) who underwent surgery for medically refractory epilepsy were compared with histopathologic findings by using the McNemar and chi 2 statistics.

RESULTS

Sensitivities for detecting abnormalities were 95% (104 of 109) for MR imaging and 32% (35 of 109) for CT; specificities were 87% (13 of 15) for MR imaging and 93% (14 of 15) for CT (P < .001 for MR versus histopathologic findings). In the subgroup of 113 patients with solitary findings, MR imaging depicted an abnormality at the surgical site in 86% (n = 97) of 113 patients compared to 28% (n = 32) for CT (P < .001). In this same subgroup, histopathologic findings were predicted by using MR imaging in 88% (n = 99) of 113 patients versus 35% (n = 40) with CT (P < .001). Multiple findings were observed in 3% of CT (three of 117) and 17% of MR (20 of 117) images.

CONCLUSION

CT has no role in the diagnostic evaluation of medically refractory epilepsy. Even in patients with medically controlled epilepsy, use of less costly CT instead of MR imaging seems imprudent.

Cerebral organization of component processes in reading

The cerebral organization of word identification processes in reading was examined using functional magnetic resonance imaging (fMRI). Changes in fMRI signal intensities were measured in 38 subjects (19 males and 19 females) during visual (line judgement), orthographic (letter case judgement), phonological (nonword rhyme judgement) and semantic (semantic category judgement) tasks. A strategy of multiple subtractions was employed in order to validate relationships between structure and function. Orthographic processing made maximum demands on extrastriate sites, phonological processing on a number of frontal and temporal sites, and lexical-semantic processing was most strongly associated with middle and superior temporal sites. Significant sex differences in the cerebral organization of reading-related processes were also observed.

Limbic lobe embryology and anatomy: dissection and MR of the medial surface of the fetal cerebral hemisphere

PURPOSE

To facilitate understanding of limbic lobe anatomy by showing embryologic transformations of the medial surface of the cerebral hemisphere.

METHODS

Brains from fetal specimens ranging from 13 to 24 weeks of gestational age were dissected. Photographs were made of the medial surface of the cerebral hemisphere. MR images of different fetal specimens of similar age were made for comparison of MR anatomy with dissected material.

RESULTS

At 13 weeks, the entire inner limbic arch of the hippocampal formation is visible on the medial surface of the cerebral hemisphere. The hippocampal sulcus extends from frontal lobe to temporal lobe. At 16 weeks, the outer neocortical limbic arch of the subcallosal area, cingulate gyrus, and parahippocampus gyrus is present. Growth of the corpus callosum is associated with reduction in size of the hippocampal formation in the frontal lobe. The sulcus of the corpus callosum is the remnant of the anterior part of the hippocampal sulcus. At 18 weeks, growth of the parahippocampal gyrus begins to conceal the hippocampal formation. The supracallosal gyrus (indusium griseum), hidden from view by the corpus callosum, and the paraterminal gyrus are remnants of the previously larger hippocampal formation.

CONCLUSIONS

Analysis of fetal specimens in different developmental stages with dissection and MR provides insight into embryologic transformations responsible for the complex anatomy of the limbic lobe.

MRI-based measurement of hippocampal volume in patients with combat-related posttraumatic stress disorder

OBJECTIVE

Studies in nonhuman primates suggest that high levels of cortisol associated with stress have neurotoxic effects on the hippocampus, a brain structure involved in memory. The authors previously showed that patients with combat-related posttraumatic stress disorder (PTSD) had deficits in short-term memory. The purpose of this study was to compare the hippocampal volume of patients with PTSD to that of subjects without psychiatric disorder.

METHOD

Magnetic resonance imaging was used to measure the volume of the hippocampus in 26 Vietnam combat veterans with PTSD and 22 comparison subjects selected to be similar to the patients in age, sex, race, years of education, socioeconomic status, body size, and years of alcohol abuse.

RESULTS

The PTSD patients had a statistically significant 8% smaller right hippocampal volume relative to that of the comparison subjects, but there was no difference in the volume of other brain regions (caudate and temporal lobe). Deficits in short-term verbal memory as measured with the Wechsler Memory Scale were associated with smaller right hippocampal volume in the PTSD patients only.

CONCLUSIONS

These findings are consistent with a smaller right hippocampal volume in PTSD that is associated with functional deficits in verbal memory.

Sex differences in the functional organization of the brain for language

A much debated question is whether sex differences exist in the functional organization of the brain for language. A long-held hypothesis posits that language functions are more likely to be highly lateralized in males and to be represented in both cerebral hemispheres in females, but attempts to demonstrate this have been inconclusive. Here we use echo-planar functional magnetic resonance imaging to study 38 right-handed subjects (19 males and 19 females) during orthographic (letter recognition), phonological (rhyme) and semantic (semantic category) tasks. During phonological tasks, brain activation in males is lateralized to the left inferior frontal gyrus regions; in females the pattern of activation is very different, engaging more diffuse neural systems that involve both the left and right inferior frontal gyrus. Our data provide clear evidence for a sex difference in the functional organization of the brain for language and indicate that these variations exist at the level of phonological processing.

Regional distribution of MR findings in hippocampal sclerosis

PURPOSE

To investigate the distribution of MR findings in the hippocampus and amygdala in patients with hippocampal sclerosis.

METHODS

We blindly evaluated MR scans for atrophy and signal changes occurring in the amygdala, hippocampal head, hippocampal body, and hippocampal tail in 57 consecutive patients with hippocampal sclerosis proved by pathologic analysis.

RESULTS

Regional atrophy or signal change was present in limbic structures. Atrophy was detected in 52 patients, occurring in the amygdala in 7 (12%), hippocampal head in 29 (51%), hippocampal body in 50 (88%), and hippocampal tail in 35 (61%). Hyperintense signal on long-repetition-time images was observed in 49 patients and involved the amygdala in 2 (4%), hippocampal head in 22 (39%), hippocampal body in 46 (81%), and hippocampal tail in 28 (49%). Thirty patients (53%) had abnormal MR findings distributed through the entire ipsilateral hippocampus, 25 (44%) had regional rather than widespread involvement of limbic structures, and 2 (3%) had no MR abnormalities.

CONCLUSION

Signal and volume changes associated with hippocampal sclerosis affect the entire hippocampus in most patients. However, a substantial number of patients have MR abnormalities that are regional, involving only portions of the hippocampus and amygdala. The most frequently affected region was the hippocampal body. These findings can have important implications for surgery and quantitative image analysis, if the seizure generator is related to MR changes.

MR characteristics of neoplasms and vascular malformations associated with epilepsy

We assessed the magnetic resonance (MR) imaging characteristics of two categories of epileptogenic substrates, neoplasms, and vascular malformations, to determine MR sensitivity and typical imaging features. A blinded retrospective analysis was performed on MR scans from 41 patients who had a neoplasm or vascular malformation surgically resected as treatment for medically refractory epilepsy. Abnormalities were assessed for sensitivity of MR detection, prediction of pathologic category, location, calvarial remodelling, signal intensity, and effect on adjacent tissue. Pathologic findings consisted of 33 tumors and 8 vascular malformations. We correctly localized 100% of the 41 lesions and predicted the correct pathologic category for 95% of these lesions. Neoplastic and vascular lesions (NVLs) associated with epilepsy had certain characteristic features. The temporal lobe was the most common site for NVL, involved in 68%. NVL were located in the brain periphery in 85% and remodelled the calvarium in 32%. NVL were associated with mass effect in 61%, volume loss in 1%, and no effect on adjacent tissue in 37%. NVL associated with epilepsy can be detected with high sensitivity using MR imaging. The temporal lobe location, cortical involvement, and calvarial remodelling are findings typical of NVL. MR characteristics can successfully predict the pathologic substrate of these lesions.

CT-guided percutaneous insertion of interstitial radiotherapy catheters in head and neck tumors

We describe a new method of placing interstitial radiation therapy catheters in patients with head and neck tumors. In three patients with recurrent inoperable head and neck tumors CT guidance was utilized to insert interstitial radiation therapy catheters percutaneously. This method enabled palliative radiation therapy to be administered without the need for surgical placement of seeds or catheters. The detailed anatomical localization of tumor and vascular structures provided by CT enabled precise percutaneous placement of afterloading catheters while ensuring safety. Pain was reduced and tumor size was decreased in all three patients. The CT-guided percutaneous insertion of afterloading catheters is a simple yet effective method of providing interstitial radiation therapy for head and neck tumors.

MR findings after depth electrode implantation for medically refractory epilepsy

PURPOSE

To evaluate using MR imaging chronic changes in the brain parenchyma after electroencephalography depth electrode placement in patients with medically refractory epilepsy.

METHODS

A retrospective review of MR scans in 57 patients who underwent stereotactic placement of 210 depth electrodes was performed. Scans were evaluated for evidence of gliosis, hemorrhage, or infection along the probe tracts.

RESULTS

Signal abnormalities along the probe tracts were seen in 38 patients (67%). Of the 210 probe tracts evaluated on long-repetition-time images, 85 (41%) were associated with punctate hyperintensity and four (2%) with punctate hypointensity; 120 (57%) showed no MR changes to suggest prior electrode placement. One probe placement was complicated by a significant intraparenchymal hemorrhage.

CONCLUSIONS

Depth electrode implantation for electroencephalography monitoring results in imperceptible or minimal chronic changes as detected by MR in almost all patients. The punctate hypersensitivity on long-repetition-time images is though to be caused by gliosis along the probe tracts. These signal changes should not be confused with the seizure focus. Significant hemorrhage or infection is a rare complication of probe placement. Incorporation of MR angiographic data with conventional spin-echo images at the time of stereotactic probe placement may further reduce the low incidence of probe-related hemorrhage.

Epilepsy: the role of MR imaging

MR is the imaging technique of choice when examining a patient who is having seizures. Detection, localization, and differentiation of structural epileptogenic abnormalities are much better with MR imaging than with CT. MR imaging has a high success rate in identifying hippocampal sclerosis, a common cause of surgically treatable temporal lobe epilepsy. The affected hippocampus is atrophic and hyperintense on long TR images. Functional imaging with single-photon emission computed tomography and positron emission tomography is complementary to MR imaging but is not as widely available. In summary, MR imaging has dramatically changed the workup of epilepsy, especially for the patient with medically uncontrollable seizures. As surgical treatment of epilepsy becomes more available, the need for preoperative evaluation with MR imaging will increase.

Efficacy of gadoteridol for magnetic resonance imaging of the brain and spine

RATIONALE AND OBJECTIVES

The efficacy of gadoteridol for contrast enhancement of central nervous system pathology was assessed in a multicenter clinical trial involving 411 patients suspected of having intracranial or spinal pathology.

METHODS

Magnetic resonance imaging was performed before and after intravenous administration of 0.10 mmol/kg gadoteridol. Two groups of images were interpreted by one of two neuroradiologists blinded to patient history. The results were analyzed separately.

RESULTS

Patients with radiologic evidence of disease demonstrated enhancement of intracranial pathologic lesions in 44 of 63 (70%) and in 91 of 111 (82%) cases, respectively, whereas enhancement of spinal lesions was observed in 36 of 58 (62%) and in 65 of 78 (83%) cases, respectively. Subjectively, postcontrast scans provided more information than precontrast images in 37 of 63 (59%) and 84 of 111 (76%) intracranial cases, respectively, and in 25 of 58 (43%) and 55 of 78 (71%) spinal cases, respectively. Additional information included the subjective sense that there was improved visualization of pathology and definition of lesion borders.

CONCLUSIONS

Subjective assessment of magnetic resonance scans suggest gadoteridol is an effective intravenous contrast agent for magnetic resonance imaging.

Quantitative magnetic resonance imaging in temporal lobe epilepsy: relationship to neuropathology and neuropsychological function

Magnetic resonance images (MRIs) were obtained from 25 patients with medically refractory epilepsy of temporal lobe origin (12 on the left, 13 on the right) and 14 right-handed control subjects. The hippocampi and temporal lobes were traced by computer on successive coronal images and the resulting measurements of area were summed for each region. The left and right hippocampi were symmetrical in the control subjects; however, for patients the hippocampus was smaller on the side of the seizure focus. Moreover, the left-right hippocampal ratio significantly differentiated the control subjects from each patient group. The left temporal lobe was significantly smaller than the right in control subjects. The epileptics' temporal lobes were smaller on the side of the seizure focus, compared to the temporal lobes in the control subjects. MRI hippocampal measurements were compared to hippocampal neuronal densities obtained postoperatively. Significant correlations were obtained between the ratio (side ipsilateral to focus/side contralateral to focus) of MRI hippocampal measurements and neuronal densities in all hippocampal subfields except CA2. Prior to surgery, patients were administered the Wechsler Memory Scale and the verbal Selective Reminding Test. Significant correlations existed between MRI measurements of the left hippocampus and the Wechsler logical memory percent retention scores and between the left temporal lobe measurements and the verbal Selective Reminding Test scores for patients with seizure foci in the left temporal lobe.

Relationship of hippocampus and amygdala to coronal MRI landmarks

Magnetic resonance imaging is playing an increasingly important role in the evaluation of the hippocampus, particularly in epilepsy, schizophrenia, and Alzheimer's dementia. Because of the complex configuration of the hippocampus, it is difficult to compare from patient to patient. We developed a system to allow comparison of the hippocampus on coronal images. We performed 34 magnetic resonance studies on 29 normal subjects. Ten anatomic landmarks were identified. These landmarks have a consistent 5-mm periodicity regardless of usual head flexion. In the second phase of our investigation, we showed that the amygdala, hippocampal head, hippocampal body, and hippocampal tail have a consistent relationship to the coronal magnetic resonance imaging landmarks.

MRI of the temporal lobe: normal variations, with special reference toward epilepsy

Recent investigations of epilepsy, Alzheimer's disease, amnesia, and schizophrenia have used magnetic resonance imaging (MRI) to evaluate changes in temporal lobe structures. Normal variations in these structures need to be defined before one can use these structures to describe abnormal conditions. Twenty-nine normal volunteers were studied by coronal MRI. Frequent findings include notching of the uncus by the tentorium or adjacent vessels (22/29) and asymmetry of the temporal horns (20/29). This finding of uncal notching strengthens the evidence against "incisural sclerosis" as the basis for hippocampal sclerosis. Temporal horn dilatation occurred in four. However, mild asymmetry of the temporal horn was seen frequently at its anterior tip (16/29) and may be related to head rotation. Asymmetry of the choroidal fissure was never marked. Mild asymmetry was common at the hippocampal head (pes). Mild enlargement of the right temporal lobe by visual inspection is not uncommon. Subtle asymmetry of the white matter between the hippocampus and the collateral sulcus occurred in six. The collateral sulcus does not always point to the temporal horn. The occipitotemporal sulcus may point to the temporal horn. Asymmetric uncal protrusion (0/29) and Sylvian fissure dilatation (4/29) occur rarely.

MRI of the normal hippocampus

Before it is possible to use MR imaging to investigate changes in the hippocampus in disease processes such as epilepsy and memory disorders, it is imperative that normal variations are defined. Using specific anatomic locations, we evaluated the hippocampi of 29 normal volunteers with coronal MR studies. Mild variations occur with regard to hippocampal size and shape, and hippocampal fissure visualization. Hippocampal signal intensity is isointense to cortical gray matter. Recognition of normally occurring variations should help prevent over-interpretation of hippocampal changes in pathologic disorders.

Imaging findings in hippocampal sclerosis: correlation with pathology

We evaluated the ability of preoperative radiologic imaging to detect hippocampal sclerosis in 31 patients who underwent surgery for intractable epilepsy. Hippocampal sclerosis is commonly associated with surgically treatable temporal lobe epilepsy. It is pathologically described as neuronal cell loss with associated gliosis in the hippocampus. While previous reports have correlated imaging results with clinical or qualitative histologic findings, this study used quantitative pathologic criteria (neuronal cell density) to diagnosis hippocampal sclerosis. We focused our study on the 11 patients with cryptogenic temporal lobe epilepsy. Of these, nine had hippocampal sclerosis by pathologic criteria. MR findings included unilateral hippocampal atrophy, an increased signal in the hippocampus on long TR scans, and atrophy in the adjacent white matter and temporal lobe. Hippocampal atrophy was most frequently seen in the red nucleus plane on coronal scans, corresponding to the body of the hippocampus. We also compared hippocampal size on MR with neuronal density in surgical specimens of the 11 patients with cryptogenic temporal lobe epilepsy. A statistically significant correlation was found between MR size and neuronal density in CA3 and CA4 of the cornu ammonis and the granular cell layer of the hippocampus. Since temporal lobectomy eliminated seizures in seven of nine patients with hippocampal sclerosis, preoperative diagnosis by MR has important therapeutic consequences.

Magnetic resonance imaging contrast agents: theory and application to the central nervous system

The theoretical aspects of magnetic resonance (MR) imaging contrast agents are reviewed, and their current applications to the central nervous system (CNS) and their future applications are discussed. Profound differences exist between contrast agents used for MR imaging and computerized tomography (CT). In MR imaging, the contrast agents are not imaged directly but rather act on adjacent protons to shorten T1 and T2 relaxation times. This in turn results in signal intensity changes. The lanthanide metal, gadolinium, in the form of gadopentetate dimeglumine, has been found to be both safe and efficacious as the only currently approved contrast agent for MR imaging. Magnetic resonance imaging revolutionized the detection and treatment of disease affecting the brain and spine. Initially, it was thought that signal characteristics on MR imaging would allow differentiation of specific pathology. It was soon found that MR studies were able to detect more abnormalities but were less able to characterize them. The recent development of contrast agents for MR imaging has allowed this modality to surpass CT for the evaluation of most CNS lesions. At present, contrast-enhanced MR imaging is generally accepted as the study of choice for evaluating acoustic neurinomas, pituitary lesions, meningeal disease, primary and secondary brain tumors, active multiple sclerosis, intradural spinal neoplasms, intramedullary spinal disease, and postoperative states in both the spine and brain. Even when contrast-enhanced CT can detect the same abnormalities, evaluation of the lesions in multiple planes on MR imaging can sometimes yield invaluable information, especially prior to surgery. Future developments of contrast material for MR imaging include non-gadolinium compounds, intrathecal contrast media, cerebral blood flow and volume evaluation, and, possibly, antibody-labeled contrast agents.

Meckel's diverticulum: axial volvulus mimicking emphysematous cholecystitis

A 48-year-old man presented with symptoms of acute cholecystitis. Abdominal roentgenograms suggested emphysematous cholecystitis. Axial volvulus of a Meckel's diverticulum was discovered at surgery. We discuss this unusual complication of Meckel's diverticula as well as the roentgenographic differential diagnosis of air in the gallbladder.

Diffuse lymphoid follicles of the colon associated with colonic carcinoma

In four patients aged 59-75 years, colonic carcinoma was associated with diffuse lymphoid follicles in the colon. In one case, the prominence and distribution of the lymphoid follicles corresponded to the progression and regression of the tumor bulk. It is extremely unusual to demonstrate lymphoid follicles, particularly diffuse, on barium enema in patients in this age range. The colonic carcinomas and lymphoid follicles are directly related, possibly representing an immune response.