Spontaneously T1-hyperintense lesions of the brain on MRI: a pictorial review

Chronic calcified subdural hematoma masquerading as hemorrhagic extra-axial mass: A case report and brief review of the literature

Calcified chronic subdural hematoma (CCSDH) is a rare condition characterized by the accumulation of calcified blood between the dura mater and arachnoid membrane, typically following remote trauma. These lesions often present as space-occupying, extra-axial masses over the cerebral convexity and can mimic extra-axial tumors, such as calcified meningiomas. A 73-year-old male with a history of prostate cancer, hypertension, and hyperlipidemia presented with vision changes and mild papilledema. CT imaging revealed a hyperdense, heterogeneous mass with localized mass effect, while MRI suggested a calcified meningioma due to minimal enhancement and a Dural tail. Given the mass effect and neurological symptoms, surgical evacuation was performed, and intraoperative findings confirmed a chronic subdural hematoma. Postoperatively, the patient's symptoms improved, and imaging confirmed complete hematoma evacuation. This case highlights the challenges in diagnosing CCSDH, as it can closely resemble other conditions like meningiomas, emphasizing the need for careful radiological assessment and timely surgical intervention.

Primary Meningeal Melanocytic Tumors of the Central Nervous System: A Review from the Ultra-Rare Brain Tumors Task Force of the European Network for Rare Cancers (EURACAN)

BACKGROUND

Primary meningeal melanocytic tumors are ultra-rare entities with distinct histological and molecular features compared with other melanocytic or pigmented lesions, such as brain and leptomeningeal metastases from metastatic melanoma.

METHODS

The European Network for Rare Cancers (EURACAN) Task Force on Ultra-Rare Brain Tumors (domain 10, subdomain 10) performed a literature review from January 1985 to December 2023 regarding the epidemiologic and clinical characteristics, histological and molecular features, radiological findings, and efficacy of local treatments (surgery and radiotherapy) and systemic treatments for these entities.

RESULTS

Molecular analysis can detect specific mutations, including GNAQ, GNA11, SF3B1, EIF1AX, BAP1, that are typically found in circumscribed primary meningeal melanocytic tumors and not in other melanocytic lesions, whereas NRAS and BRAF mutations are typical for diffuse primary meningeal melanocytic tumors. The neuroimaging of the whole neuroaxis suggests a melanocytic nature of a lesion, depicts its circumscribed or diffuse nature, but cannot predict the tumor's aggressiveness. Gross-total resection is the first choice in the case of circumscribed meningeal melanocytoma and melanoma; conversely, meningeal biopsy may be reserved for patients with diffuse and multinodular leptomeningeal spread to achieve a definitive diagnosis. High-dose radiotherapy is rarely indicated in diffuse melanocytic tumors except as palliative treatment to alleviate symptoms. Last, a definitive advantage of a specific systemic treatment could not be concluded, as most of the data available derive from case reports or small cohorts.

CONCLUSIONS

As primary meningeal melanocytic tumors are extremely rare, the correlations between the clinical characteristics, molecular profile, radiological findings at diagnosis and progression are weak, and poor evidence on the best therapeutic approach is available. There is a need to develop shared platforms and registries to capture more knowledge regarding these ultra-rare entities.

Benign Intracranial Calcified Lesion or a So-Called Brain Stone: A Challenging Diagnosis

Brain stone is an umbrella term for benign intracerebral calcifications and may be associated with various diagnoses. The surgical decision should be made on a case-by-case basis. Sometimes, conservative management should be considered, irrespective of the underlying pathology. We present a critical case with a brain stone treated conservatively. A 17-year-old female patient was admitted to our department with a headache. The neurological examination revealed no abnormal findings. Cranial CT and MRI scans showed a contrast-enhanced, highly calcified lesion located deep in the white matter at the level of the left centrum semiovale. Surgery was found unnecessary. The patient presented no neurologic deficits or symptoms during the three-year follow-up period. In this case, the differential diagnosis included arteriovenous malformations (AVMs), cavernomas, calcifying pseudoneoplasms of the neuroaxis (CAPNON), etc. The localization of the lesion, expression of the symptoms, and potential outcomes of a possible surgery should be carefully estimated before making the final decision. In summary, conservative treatment should also be considered for critically located, benign calcified lesions, irrespective of pathology, unless they cause intense neurologic symptoms or deficits.

Diffusion-weighted imaging hyperintensities during the chronic stage of intracerebral hemorrhage with surgery: A new clinical situation or post-surgery artifact?

Background and objective

Diffusion-weighted imaging (DWI) hyperintensities were occasionally seen at previous hematoma in patients several months after intracerebral hemorrhage with surgery. Whether they are newly occurred clinical situations or post-surgery changes is unknown. This study aims to investigate the prevalence and possible mechanisms for this phenomenon.

Methods

We retrospectively reviewed the MRI database for intracerebral hemorrhage with surgery after 3 months of disease onset in our hospital. We also prospectively performed repeated multimodal MRI scans for two patients at the chronic stage after surgery for intracerebral hemorrhage.

Results

We found that 14 out of 23 patients (60.9%) had DWI hyperintensities at the site of previous hematoma 3 months after intracerebral hemorrhage with surgery. All the DWI lesions were hyperintense on T1- and T2-weighted imaging, most of which appeared long and narrow in shape. The DWI lesions were usually located adjacent to the thin wall of the previous hematoma cavity close to the lateral ventricle. They were more associated with the basal ganglia hemorrhage than with the lobar hemorrhage (P = 0.02) and were more frequently seen for those with intraventricular hemorrhage than without (P = 0.02). Prospectively repeated MRI exams of two patients revealed unchanged DWI hyperintensity during the 18- and 2-month follow-up, respectively.

Conclusion

The DWI lesions at previous hematoma were commonly seen in patients after surgery for intracerebral hemorrhage at the chronic stage which would persist for years. We hypothesized a possible mechanism by which extracellular methemoglobin “islands” are formed with delayed or no absorption by macrophages from adjacent thin residual brain tissue. Unnecessary further examinations and treatment would be avoided by realizing this imaging phenomenon.

Correlation of MRI signal characteristics of intracranial melanoma metastases with BRAF mutation status

BRAF V600 mutations (BRAFmut) are associated with more pigmentation in primary melanomas, but data on melanin content of metastases are limited. This study compares signal characteristics of BRAFmut and BRAF-wildtype (BRAFwt) intracranial melanoma metastases (IMM). MRI brain examinations at first diagnosis of IMM were identified, all performed at 3-Tesla including 1 mm volumetric pre- and postcontrast T1-weighted imaging and susceptibility-weighted imaging (SWI). Individual metastases were assessed by a neuroradiologist, stratified by size (≥10 mm, 'larger', vs. 2-9 mm, 'small'; up to 10 per group); presence of intrinsic T1-hyperintensity (T1H) and, if present, whether confidently attributable to melanin as opposed to haemorrhage; evidence of haemorrhage; presence of central necrosis. A total of 267 IMM in 73 patients were assessed (87 larger IMM, 180 small). The proportion of larger IMM was similar in both groups (31% BRAFmut and 36% BRAFwt). In small IMM, MRI evidence of melanin was more common in BRAFmut patients (42% vs. 26%; P = 0.038). Haemorrhage was more common in larger IMM (51%, vs. 20% of small IMM; P < 0.0001), but did not differ based on BRAF status. Central necrosis was more common in larger IMM (44% vs. 7%; P < 0.0001) and in BRAFmut IMM (23% vs. 11%; P = 0.011). In the BRAFmut cohort, central necrosis was more common in patients without previous anti-BRAF therapy (33% vs. 7%; P = 0.0001). T1H attributable to melanin is only slightly more common in BRAFmut IMM than BRAFwt. Higher rates of central necrosis in BRAFmut patients without previous anti-BRAF therapy suggest that anti-BRAF therapy may affect the patterns of IMM growth.

An interpretable radiomics model for the diagnosis of panic disorder with or without agoraphobia using magnetic resonance imaging

BACKGROUND

Early and accurate diagnosis of panic disorder with or without agoraphobia (PDA) is crucial to reducing disease burden and individual suffering. However, its diagnosis is challenging for lack of validated biomarkers. This study aimed to investigate whether radiomic features extracted from T1-weighted images (T1) of major fear-circuit structures (amygdala, insula, and anterior cingulate cortex [ACC]) could differentiate patients with PDA from healthy controls (HCs).

METHODS

The 213 participants (93 PDA, 120 HCs) were allocated to training (n = 149) and test (n = 64) sets after undergoing magnetic resonance imaging. Radiomic features (n = 1498) were extracted from T1 of the studied structures. Machine learning models were trained after feature selection and then validated in the test set. SHapley Additive exPlanations (SHAP) explored the model interpretability.

RESULTS

We identified 29 radiomic features to differentiate participants with PDA from HCs. The area under the curve, accuracy, sensitivity, and specificity of the best performing radiomics model in the test set were 0.84 (95% confidence interval: 0.74-0.95), 81.3%, 75.0%, and 86.1%, respectively. The SHAP model explanation suggested that the energy features extracted from the bilateral long insula gyrus and central sulcus of the insula and right ACC were highly associated with the risk of PDA.

LIMITATIONS

This was a cross-sectional study with a relatively small sample size, and the causality of changes in radiomic features and their biological and clinical meanings remained to be elucidated.

CONCLUSIONS

Our findings suggest that radiomic features from the fear-circuit structures could unveil hidden microstructural aberrations underlying the pathogenesis of PDA that could help identify PDA.

Pre-contrast T1-weighted imaging of the spinal cord may be unnecessary in patients with multiple sclerosis

Objectives

Multiple sclerosis (MS) is an inflammatory disease frequently involving the spinal cord, which can be assessed by magnetic resonance imaging (MRI). Here, we hypothesize that pre-contrast T1-w imaging does not add diagnostic value to routine spinal MRI for the follow-up of patients with MS.

Methods

3-T MRI scans including pre- and post-contrast T1-w as well as T2-w images of 265 consecutive patients (mean age: 40 ± 13 years, 169 women) with (suspected) MS were analyzed retrospectively. Images were assessed in two separate reading sessions, first excluding and second including pre-contrast T1-w images. Two independent neuroradiologists rated the number of contrast-enhancing (ce) lesions as well as diagnostic confidence (1 = unlikely to 5 = very high), overall image quality, and artifacts. Results were compared using Wilcoxon matched-pairs signed-rank tests and weighted Cohen’s kappa (κ).

Results

Fifty-six ce lesions were found in 43 patients. There were no significant differences in diagnostic confidence between both readings for both readers (reader 1: p = 0.058; reader 2: p = 0.317). Inter-rater concordance was both moderate regarding artifacts (κ = 0.418) and overall image quality (κ = 0.504). Thirty-one black holes were found in 25 patients with high diagnostic confidence (reader 1: 4.04 ± 0.81; reader 2: 3.80 ± 0.92) and substantial inter-rater concordance (κ = 0.700).

Conclusions

Availability of pre-contrast T1-w images did not significantly increase diagnostic confidence or detection rate of ce lesions in the spinal cord in patients with MS. Thus, pre-contrast T1-w sequences might be omitted in routine spinal MRI for follow-up exams, however not in special unclear clinical situations in which certainty on contrast enhancement is required.

Key Points

Availability of pre-contrast T1-w images does not increase diagnostic confidence or detection rate of contrast-enhancing lesions in the spinal cord of MS patients.

Excluding pre-contrast T1-w sequences reduces scan time, thus providing more time for other sequences or increasing the patients’ compliance.

Intracranial solitary fibrous tumor/hemangiopericytoma mimicking cystic meningioma: A case report and literature review

Intracranial solitary fibrous tumor/hemangiopericytoma (SFT/HPC) is a relatively rare type of tumor that originates from meningeal mesenchyme. A 30-year-old man presented leaning his body to the left and with weakness of his left lower limb. Computed tomography revealed a heterogeneous mass with multiple cystic components and hyperostosis of the right cranial convexity. Magnetic resonance imaging showed the mass was broadly attached to the dura matter with dural tail sign. In addition, the lesion had extensive cystic degeneration and a solid compartment showing low apparent diffusion coefficient values. The patient underwent gross total resection of the intracranial lesion and presented no recurrence within a 12-month follow-up period. Histopathology confirmed SFT/HPC (World Health Organization grade Ⅱ). Although there have been several useful techniques reported to differentiate SFT/HPC from meningioma, in this case the atypical findings for SFT/HPC made it difficult. We report the imaging findings of this case and some literature reviews.

Imaging Ischemic and Hemorrhagic Disease of the Brain in Dogs

Strokes, both ischemic and hemorrhagic, are the most common underlying cause of acute, non-progressive encephalopathy in dogs. In effect, substantial information detailing the underlying causes and predisposing factors, affected vessels, imaging features, and outcomes based on location and extent of injury is available. The features of canine strokes on both computed tomography (CT) and magnetic resonance imaging (MRI) have been described in numerous studies. This summary article serves as a compilation of these various descriptions. Drawing from the established and emerging stroke evaluation sequences used in the investigation of strokes in humans, this summary describes all theoretically available sequences. Particular detail is given to logistics of image acquisition, description of imaging findings, and each sequence's advantages and disadvantages. As the imaging features of both forms of strokes are highly representative of the underlying pathophysiologic stages in the hours to months following stroke onset, the descriptions of strokes at various stages are also discussed. It is unlikely that canine strokes can be diagnosed within the same rapid time frame as human strokes, and therefore the opportunity for thrombolytic intervention in ischemic strokes is unattainable. However, a thorough understanding of the appearance of strokes at various stages can aid the clinician when presented with a patient that has developed a stroke in the days or weeks prior to evaluation. Additionally, investigation into new imaging techniques may increase the sensitivity and specificity of stroke diagnosis, as well as provide new ways to monitor strokes over time.

Assessment of lesions on magnetic resonance imaging in multiple sclerosis: practical guidelines

MRI has improved the diagnostic work-up of multiple sclerosis, but inappropriate image interpretation and application of MRI diagnostic criteria contribute to misdiagnosis. Some diseases, now recognized as conditions distinct from multiple sclerosis, may satisfy the MRI criteria for multiple sclerosis (e.g. neuromyelitis optica spectrum disorders, Susac syndrome), thus making the diagnosis of multiple sclerosis more challenging, especially if biomarker testing (such as serum anti-AQP4 antibodies) is not informative. Improvements in MRI technology contribute and promise to better define the typical features of multiple sclerosis lesions (e.g. juxtacortical and periventricular location, cortical involvement). Greater understanding of some key aspects of multiple sclerosis pathobiology has allowed the identification of characteristics more specific to multiple sclerosis (e.g. central vein sign, subpial demyelination and lesional rims), which are not included in the current multiple sclerosis diagnostic criteria. In this review, we provide the clinicians and researchers with a practical guide to enhance the proper recognition of multiple sclerosis lesions, including a thorough definition and illustration of typical MRI features, as well as a discussion of red flags suggestive of alternative diagnoses. We also discuss the possible place of emerging qualitative features of lesions which may become important in the near future.

A neonatal nonhuman primate model of gestational Zika virus infection with evidence of microencephaly, seizures and cardiomyopathy

Zika virus infection during pregnancy is associated with miscarriage and with a broad spectrum of fetal and neonatal developmental abnormalities collectively known as congenital Zika syndrome (CZS). Symptomology of CZS includes malformations of the brain and skull, neurodevelopmental delay, seizures, joint contractures, hearing loss and visual impairment. Previous studies of Zika virus in pregnant rhesus macaques (Macaca mulatta) have described injury to the developing fetus and pregnancy loss, but neonatal outcomes following fetal Zika virus exposure have yet to be characterized in nonhuman primates. Herein we describe the presentation of rhesus macaque neonates with a spectrum of clinical outcomes, including one infant with CZS-like symptoms including cardiomyopathy, motor delay and seizure activity following maternal infection with Zika virus during the first trimester of pregnancy. Further characterization of this neonatal nonhuman primate model of gestational Zika virus infection will provide opportunities to evaluate the efficacy of pre- and postnatal therapeutics for gestational Zika virus infection and CZS.

Primary extracranial nasopharyngeal meningioma in a dog

An 8-year-old Labrador Retriever was presented for inspiratory efforts with stertor. A rhinoscopy and a magnetic resonance imaging scan were performed and revealed a naso-pharyngeal mass. The mass was identified in the nasopharynx without meningeal extension. This mass was both T1- and T2-hyperintense, compared to normal brain parenchyma without significant postcontrast enhancement. The mass was surgically removed and the histologic diagnosis was a mesenchymal tumor. Immunohistochemistry with antibodies was conducted and consistent with an extracranial meningioma. To the authors' knowledge, this is the first case report documenting a primary extracranial nasopharyngeal meningioma in a dog.

MAGNETIC RESONANCE IMAGING FEATURES OF INTRAVENTRICULAR EPENDYMOMAS IN Five CATS

Intraventricular ependymoma is a rare type of feline intracranial neoplasia and published information on magnetic resonance imaging (MRI) characteristics is currently lacking. The purpose of this retrospective case series study was to describe the clinical and MRI characteristics of histopathologically confirmed intraventricular ependymomas in a group of cats. Five cats met inclusion criteria. In relation to normal gray matter, ependymomas appeared hyperintense on T2W, T2W‐FLAIR, PD, and DW‐EPI images; isointense on ADC images; and had subtle to strong contrast enhancement. Some variability was seen on T2*GRE and on T1W images with masses being isointense to hyperintense. Four ependymomas were small and homogeneous, and one was centrally cavitated. All cats had obstructive hydrocephalus, transtentorial herniation, and foramen magnum herniation. Perilesional edema was identified in most cats but was questionable in one. Intraventricular ependymoma should be considered as a differential diagnosis for cats with this combination of MRI signs.

Simultaneous Quantitative Imaging of Electrical Properties and Proton Density From B1 Maps Using MRI

Electrical conductivity and permittivity of biological tissues are important diagnostic parameters and are useful for calculating subject-specific specific absorption rate distribution. On the other hand, water proton density also has clinical relevance for diagnosis purposes. These two kinds of tissue properties are inevitably associated in the technique of electrical properties tomography (EPT), which can be used to map in vivo electrical properties based on the measured B1 field distribution at Larmor frequency using magnetic resonance imaging (MRI). The signal magnitude in MR images is locally proportional to both the proton density of tissue and the receive B1 field; this is a source of artifact in receive B1-based EPT reconstruction because these two quantities cannot easily be disentangled. In this study, a new method was proposed for simultaneously extracting quantitative conductivity, permittivity and proton density from the measured magnitude of transmit B1 field, proton density-weighted receive B1 field, and transceiver phase, in a multi-channel radiofrequency (RF) coil using MRI, without specific assumptions to derive the proton density distribution. We evaluated the spatial resolution, sensitivity to contrast, and accuracy of the method using numerical simulations of B1 field in a phantom and in a realistic human head model. Using the proposed method, conductivity, permittivity and proton density were then experimentally obtained ex vivo in a pork tissue sample on a 7T MRI scanner equipped with a 16-channel microstrip transceiver RF coil.

Clinical, magnetic resonance imaging, and histopathologic findings in 6 dogs with surgically resected extraparenchymal spinal cord hematomas

BACKGROUND

Extraparenchymal spinal cord hematoma has been described in veterinary medicine in association with neoplasia, intervertebral disk disease, and snake envenomation. There are rare reports of spontaneous extraparenchymal spinal cord hematoma formation with no known cause in human medicine. Multiple cases of spontaneous extraparenchymal spinal cord hematoma have not been described previously in veterinary medicine.

OBJECTIVES

To describe the signalment, clinical findings, magnetic resonance imaging (MRI) features, and surgical outcomes in histopathologically confirmed extraparenchymal spinal cord hematomas in dogs with no identified underlying etiology.

ANIMALS

Six dogs had MRI of the spinal cord, decompressive spinal surgery, and histopathologic confirmation of extraparenchymal spinal cord hematoma not associated with an underlying cause.

METHODS

Multi-institutional retrospective study.

RESULTS

Six patients had spontaneous extraparenchymal spinal cord hematoma formation. MRI showed normal signal within the spinal cord parenchyma in all patients. All hematomas had T2-weighted hyperintensity and the majority (5/6) had no contrast enhancement. All dogs underwent surgical decompression and most patients (5/6) returned to normal or near normal neurologic function postoperatively. Follow-up of the patients (ranging between 921 and 1,446 days) showed no progression of neurologic clinical signs or any conditions associated with increased bleeding tendency.

CONCLUSIONS AND CLINICAL IMPORTANCE

Before surgery and histopathology confirming extraparenchymal hematoma, the primary differential in most cases was neoplasia, based on the MRI findings. This retrospective study reminds clinicians of the importance of the combination of advanced imaging combined with histopathologic diagnosis. The prognosis for spontaneous spinal cord extraparenchymal hematoma with surgical decompression appears to be favorable in most cases.

Lesions of the ovary with T1-hypersignal

Pelvic magnetic resonance imaging (MRI) has been used successfully to diagnose ovarian masses that cannot be adequately evaluated using pelvic ultrasound. T1 hyperintensity is a common finding in an ovarian mass and has important diagnostic implications. The aims of this review are to list the substances that may produce high signal intensity on T1-weighted MRI, to explain the physical basis for causes of the high T1 signal intensity, and to describe common and uncommon T1 hyperintense ovarian lesions. The morphological findings, the imaging features of the additional sequences, and clinical variables can help in the differential diagnosis, and in some cases, enable a specific diagnosis, leading to appropriate management of the patient.

Inherited manganism: the "cock-walk" gait and typical neuroimaging features

Manganese (Mn) toxicity causes an extrapyramidal, parkinsonian-type movement disorder with characteristic magnetic resonance images of Mn accumulation in the basal ganglia. This letter highlights the neurological manifestations and neuroimaging features of inherited manganism (IMn), an unusual and treatable inborn error of Mn homeostasis. Early-onset dystonia with "cock-walk" gait and hyperintense signal in basal ganglia, associated to polycythemia, chronic liver disease and hypermanganesemia, promptly suggest IMn, and a genetic evaluation should be performed.

Analysis of proton-density bias corrections based on T1 measurement for robust quantification of water content in the brain at 3 Tesla

PURPOSE

Estimating tissue water content using high field MRI, such as 3 Tesla (T), is challenging due to the difficulty in dissociating the radio frequency inhomogeneity pattern from the signal arising from tissue intrinsic proton density (PD) variations. To overcome this problem the longitudinal relaxation time T1 can be combined with an initial guess of the PD to yield the desired PD bias correction. However, it is necessary to know whether T1 effects, i.e., any effect contributing to T1 while being independent of tissue hydration, influence the estimated correction.

METHODS

Twenty-five healthy subjects underwent a quantitative 3T MRI protocol enabling acquisition of 64 slices with 1 mm in-plane resolution and 2 mm slice thickness in 14 min. Influence of T1 effects on the estimated water content map is evaluated using a dedicated method including T1 and T2 * information and region of interest-based water content values are compared with the literature.

RESULTS

Our analysis indicates that the PD bias correction based on T1 is largely insensitive to T1 effects. Besides, water content results are in good agreement with literature values obtained at 1.5T.

CONCLUSION

This study demonstrates the applicability of a PD bias correction based on T1 to yield tissue water content at 3T.

Intracranial lesions with high signal intensity on T1-weighted MR images - review of pathologies

In the article we present pathological intracranial substances and lesions, which produce high signal intensity on T1-weighted MR images. Six groups of substances are discussed: 1. Gadolinium – based contrast agents, 2.hemoglobin degradation products (intra- and extra-cellular methemoglobin), 3. lipid-containing lesions (lipoma, dermoid cyst, implanted fatty materials, laminar cortical necrosis), 4. substances with high concentration of proteins (colloid cyst, craniopharyngioma, Rathke’s cleft cyst, ectopic posterior pituitary gland), 5. melanin (metastatic melanoma), 6. lesions containing mineral substances such as: calcium (calcifications, Fahr’s disease), copper (Wilson’s disease) and manganese (hepatic encephalopathy, manganese intoxication in intravenous drug abusers). Appropriate interpretation of signal intensity as well as analysis of location of lesions and clinical symptoms enables planning of further diagnostics and, in many cases, establishing the final diagnosis based on MR examination.

Multimodal imaging enables early detection and characterization of changes in tumor permeability of brain metastases

Our goal was to develop strategies to quantify the accumulation of model therapeutics in small brain metastases using multimodal imaging, in order to enhance the potential for successful treatment. Human melanoma cells were injected into the left cardiac ventricle of immunodeficient mice. Bioluminescent, MR and PET imaging were applied to evaluate the limits of detection and potential for contrast agent extravasation in small brain metastases. A pharmacokinetic model was applied to estimate vascular permeability. Bioluminescent imaging after injecting d-luciferin (molecular weight (MW) 320 D) suggested that tumor cell extravasation had already occurred at week 1, which was confirmed by histology. 7T T1w MRI at week 4 was able to detect non-leaky 100 μm sized lesions and leaky tumors with diameters down to 200 μm after contrast injection at week 5. PET imaging showed that (18)F-FLT (MW 244 Da) accumulated in the brain at week 4. Gadolinium-based MRI tracers (MW 559 Da and 2.066 kDa) extravasated after 5 weeks (tumor diameter 600 μm), and the lower MW agent cleared more rapidly from the tumor (mean apparent permeabilities 2.27 × 10(-5)cm/s versus 1.12 × 10(-5)cm/s). PET imaging further demonstrated tumor permeability to (64)Cu-BSA (MW 65.55 kDa) at week 6 (tumor diameter 700 μm). In conclusion, high field T1w MRI without contrast may improve the detection limit of small brain metastases, allowing for earlier diagnosis of patients, although the smallest lesions detected with T1w MRI were permeable only to d-luciferin and the amphipathic small molecule (18)F-FLT. Different-sized MR and PET contrast agents demonstrated the gradual increase in leakiness of the blood tumor barrier during metastatic progression, which could guide clinicians in choosing tailored treatment strategies.

Miliary brain metastases from papillary adenocarcinoma of the lung - unusual MRI pattern with histopathologic correlation

Miliary brain metastases are very rarely described in the literature but if they are, they are quite obvious on magnetic resonance imaging (MRI) and enhance after intravenous administration of the contrast medium. The authors presented a case of miliary metastatic spread to the brain which was invisible on computed tomography and hardly visible on MRI, i.e. as countless, tiny, slightly T1-hyperintense foci that did not enhance. The authors discussed a few T1-hyperintense brain lesions which did not include metastases (except for metastatic melanoma which was a radiological suggestion after brain MRI). Autopsy revealed papillary adenocarcinoma of the lung with numerous metastatic lesions in both cerebral and cerebellar hemispheres and the meninges.

Miliary brain metastases from papillary adenocarcinoma of the lung - unusual MRI pattern with histopathologic correlation

Miliary brain metastases are very rarely described in the literature but if they are, they are quite obvious on magnetic resonance imaging (MRI) and enhance after intravenous administration of the contrast medium. The authors presented a case of miliary metastatic spread to the brain which was invisible on computed tomography and hardly visible on MRI, i.e. as countless, tiny, slightly T1-hyperintense foci that did not enhance. The authors discussed a few T1-hyperintense brain lesions which did not include metastases (except for metastatic melanoma which was a radiological suggestion after brain MRI). Autopsy revealed papillary adenocarcinoma of the lung with numerous metastatic lesions in both cerebral and cerebellar hemispheres and the meninges.

Brain stones revisited-between a rock and a hard place

OBJECTIVES AND METHODS

Large intracranial calcifications are occasionally encountered in routine computed tomography (CT) scans of the brain. These calcifications, also known as "brain stones", can be classified according to location and aetiology. Combining imaging findings with relevant clinical history and physical examination can help narrow down the differential diagnosis and may allow confident diagnosis in certain situations.

RESULTS

This article provides a pictorial review illustrating various clinical entities resulting in brain stones.

DISCUSSION

Based on location, brain stones can be classified as extra- or intra-axial. Extra-axial brain stones comprise tumours and exaggerated physiological calcifications. Intra-axial brain stones can further be classified according to aetiology, namely neoplastic, vascular, infectious, congenital and endocrine/metabolic. Imaging findings combined with essential clinical information can help in narrowing the differential diagnosis, determining disease state and evaluating effect of therapy.

TEACHING POINTS

• Based on location, brain stones can be either extra- or intra-axial. • Extra-axial brain stones comprise tumours and exaggerated physiological calcifications. • Intra-axial aetiologies include neoplastic, vascular, infectious, congenital and endocrine/metabolic. • CT scan is the mainstay in identifying and characterising brain stones. • Certain MRI sequences (gradient echo T2* and susceptibility-weighted imaging) are considered adjunctive.

Full scope of options

OBJECTIVE

The purpose of Clinical Problem Solving articles is to present management challenges to give practicing neurosurgeons insight into how field leaders address these dilemmas. This illustration is accompanied by a brief review of the literature on the topic.

PRESENTATION

The case of a 16-year-old boy presenting with headaches is presented. The patient is found to have a typical colloid cyst at the foramen of Monro. Bilateral ventriculoperitoneal shunt placement had been performed as an initial treatment of the patient before presentation.

RESULTS

Surgeons experienced in open and endoscopic surgery discuss their individual approaches to colloid cysts, in the context of previous shunting, providing a varied perspective on the clinical challenges posed by these lesions.

CONCLUSION

Both open and endoscopic options remain viable for excision of a colloid cyst. Each has associated potential complications, as illustrated by the current case.

Brain damages in ketamine addicts as revealed by magnetic resonance imaging

Ketamine, a known antagonist of N-methyl-D-aspartic (NMDA) glutamate receptors, had been used as an anesthetic particularly for pediatric or for cardiac patients. Unfortunately, ketamine has become an abusive drug in many parts of the world while chronic and prolonged usage led to damages of many organs including the brain. However, no studies on possible damages in the brains induced by chronic ketamine abuse have been documented in the human via neuroimaging. This paper described for the first time via employing magnetic resonance imaging (MRI) the changes in ketamine addicts of 0.5–12 years and illustrated the possible brain regions susceptible to ketamine abuse. Twenty-one ketamine addicts were recruited and the results showed that the lesions in the brains of ketamine addicts were located in many regions which appeared 2–4 years after ketamine addiction. Cortical atrophy was usually evident in the frontal, parietal or occipital cortices of addicts. Such study confirmed that many brain regions in the human were susceptible to chronic ketamine injury and presented a diffuse effect of ketamine on the brain which might differ from other central nervous system (CNS) drugs, such as cocaine, heroin, and methamphetamine.

Post-treatment T1 shortening in primary CNS lymphoma

The incidence of primary central nervous system lymphoma (PCNSL) has increased over the past two decades. The MR imaging appearance of PCNSL plays a central role in the initial diagnosis, management and follow-up of patients. The purpose of this study was to describe the presence and frequency of the pre-contrast T1 hyperintensity (T1h) that is sometimes identified in the region of enhancing neoplastic disease following treatment of PCNSL. We also explored possible causes for this phenomenon that, to the best of our knowledge, has not been previously described. The MR imaging and relevant medical records of 221 patients with pathologically confirmed PCNSL were retrospectively reviewed. Only patients with both treatment and follow-up imaging at our institution were eligible for inclusion in the study. Patients with evidence of post-procedural blood products (pre-contrast bright T1 lesions) prior to the initiation of therapy were excluded. Out of 221 patients, 119 met the eligibility criteria and were included in this investigation. Following treatment, 75 patients (63 %) developed pre-contrast T1h not attributable to blood products. All patients with this finding had been treated with methotrexate chemotherapy. The development of pre-contrast T1h following treatment for PCNSL is common. The hyperintense T1 signal in these patients may be caused by the biochemical response of tumor cells to treatment. To assess the prognostic significance of this novel finding, additional studies focusing on disease recurrence and patient survival are warranted.

The use of neuroimaging to guide the histologic diagnosis of central nervous system lesions

Recent advances in neuroimaging techniques, particularly in magnetic resonance imaging, have led to substantially improved spatial anatomic resolution such that subtle or small central nervous system lesions, which could go undetected on gross examination of brain sections, are now readily identified on imaging. Although neuroimaging is generally considered the surrogate of gross neuropathology, it is still not a substitute for tissue diagnosis. Rather, it can be a valuable tool for the surgical pathologist in the process of formulating a differential diagnosis based on location and imaging features, as well as in identifying radiologic/pathologic discordance, such as the possible undersampling of a heterogenous glioma, which could lead to underestimation of the tumor grade. The following review focuses on the application of neuroimaging techniques, mainly magnetic resonance imaging, to the histologic diagnosis of central nervous system lesions, and the correlation of imaging features of infiltrative gliomas with histologic findings pertinent to tumor grading. The use of advanced functional magnetic resonance methods, specifically diffusion-weighted imaging, perfusion-weighted imaging, and magnetic resonance spectroscopy is also discussed, as well as the common pitfalls in imaging interpretation.

Unusual CT hyperattenuating dermoid cyst of cerebellum: a new case report and literature review

Almost all intracranial dermoid cysts typically display low-density lesions on plain computerized tomography (CT) scans due to abundant lipids content. CT hyperattenuating dermoid cyst (CHADC) is very uncommon with only nine case reports in the literature update, which occurs exclusively in the posterior fossa. Moreover, CHADC with mural nodule is exceptionally rare, and only one such case was documented previously. Here, we report a new case of cerebellar CHADC with mural nodule in a 14-year-old male patient who presented with a 4-week history of dull headache and 5-day history of gait disturbance. With an average attenuation value of 89.9 Hounsfield units on CT scans, the lesion mainly displayed T1 hyperintensity, T2 hypointensity, and FLAIR hypointensity on magnetic resonance imaging. The patient underwent lesion gross total resection and symptomatic improvement, and final pathology was consistent with dermoid cyst. For further clarifying the mechanism of unusual CT hyperdensity, we sampled the cystic content and quantified its protein, calcium, and cholesterol, and our result suggested the high protein, high calcium, and low lipids in contents was the main mechanism of increased CT attenuation for CHADC.

Imaging tumors of the pediatric central nervous system

Primary tumors of the central nervous system (CNS) are the second most common neoplasms in children and the leading cause of death in this patient population. The primary objective of this article is to describe the most common pediatric brain tumors and to offer an overview of their respective imaging features, primarily on magnetic resonance imaging. Precise anatomic characterization is essential for developing an appropriate differential diagnosis. Once equipped with this critical information, physicians should be better able to make firm diagnoses, leading to improved disease management and patient outcomes in the setting of CNS tumors of childhood.

MRI of the female pelvis: a possible pitfall in the differentiation of haemorrhagic vs. fatty lesions using fat saturated sequences with inversion recovery

The use of fat-saturated techniques should be an integral part of the work-up of any T1-hyperintense structure in the female pelvis for tissue characterization and for differentiation of a fat-containing ovarian mature teratoma from a haemorrhagic lesion. Two cases with haematocolpos and haematometra are presented, respectively. The haemorrhagic content showed high signal both on T1- and T2-weighted images, whereas an unexpected signal decrease in the fat-saturated T2-weighted inversion-recovery sequence was encountered. This unspecific suppression of signal in tissues with similar T1 relaxation times as fat can lead to a diagnostic pitfall both in T1- and T2-weighted STIR pulse sequences. Furthermore, a loss of signal on T2-weighting may also be due to the phenomenon of "T2-shading" in T1-bright ovarian endometrioma. Therefore, the fat-specific spectral fat-saturation of T1-weighted images is strongly recommended for tissue characterization in gynaecological disease.

Multiple sclerosis: hyperintense dentate nucleus on unenhanced T1-weighted MR images is associated with the secondary progressive subtype

PURPOSE

To describe the occurrence of abnormal hyperintensity in the dentate nucleus on T1-weighted magnetic resonance (MR) images in patients with multiple sclerosis (MS) as a neuroradiologic sign of gray matter involvement. Presence of the finding was evaluated for association with disability, clinical MS subtype, total lesion volume on T1- and T2-weighted MR images (lesion load), and brain atrophy.

MATERIALS AND METHODS

Written informed consent was waived by the Ethics Committee because of the retrospective nature of this single-center Institutional Review Board-approved study. MR examinations of 185 patients with MS were reviewed, and 119 patients were included for analysis. Two neuroimagers, who were blinded to clinical data, assessed the presence of a hyperintense dentate nucleus on T1-weighted MR images. The presence of this radiologic alteration was then evaluated in relation to MS subtype, clinical disability, T1 and T2 lesion load, and whole-brain atrophy measurements. Fisher exact, chi(2), and Mann-Whitney U tests were used to evaluate differences in clinical and imaging features between patients with and those without a T1 hyperintense dentate nucleus.

RESULTS

Twenty-three (19.3%) of the 119 patients had a hyperintense dentate nucleus on unenhanced T1-weighted MR images. This finding was related to the secondary progressive subtype of the disease, a higher score on the Expanded Disability Status Scale, a higher brain lesion load, and tissue loss. None of the patients with primary progressive MS had a hypterintense dentate nucleus.

CONCLUSION

Hyperintensity of the dentate nucleus may be present on unenhanced T1-weighted MR images of patients with MS and is associated with the secondary progressive disease subtype and with increased clinical disability, lesion load, and brain atrophy.

Putaminal hyperintensity on T1-weighted MR imaging in patients with the Parkinson variant of multiple system atrophy

BACKGROUND AND PURPOSE

A hyperintense putaminal rim, putaminal hypointensity, and putaminal atrophy on T2-weighted MR images are findings suggestive of parkinsonian-dominant multiple system atrophy (MSA-P). However, putaminal hyperintensity on T1-weighted images, which has not been discussed in previous reports, is also frequently observed in patients with MSA-P. Here, we investigated whether putaminal hyperintensity on T1-weighted images is helpful to diagnose MSA-P.

MATERIALS AND METHODS

Patients with MSA-P (n = 17), Parkinson disease (PD; n = 37) and progressive supranuclear palsy (PSP; n = 11), and healthy control subjects (n = 16) were enrolled in this study. Two examiners, who were blind to the diagnoses, independently rated the putaminal hyperintensity on T1-weighted images (T1H), hyperintense putaminal rim on T2-weighted images (T2H), putaminal hypointensity on T2-weighted images (T2 L), and putaminal atrophy by using a visual analog scale, and performed a receiver operating characteristic (ROC) analysis. The area under the curve (AUC; minimum, 0.5; maximum, 1.0) was automatically calculated as a positive parameter, indicating its usefulness to differentiate between diseases.

RESULTS

For differentiating patients with MSA-P from healthy control subjects, AUC values were 0.983 for T1H, 0.923 for T2H, 0.726 for T2 L, and 0.967 for putaminal atrophy. Between MSA-P and PD, the respective AUC values were 0.990, 0.921, 0.739, and 0.923; and between MSA-P and PSP, the respective AUC values were 0.984, 0.923, 0.727, and 0.967.

CONCLUSIONS

All putaminal findings except T2 L were useful for the diagnosis of MSA-P. T1H was superior to T2H to differentiate MSA-P from other diseases.

Intracranial metastasis masquerading as acute subdural haematoma

We discuss a case of subdural metastasis in which the clinical features and associated images mimic acute subdural haematoma.

Lipomatous meningioma

We present a case of intracranial lipomatous meningioma in the parietal convexity in a 64-year-old woman. The mass showed low density on computed tomography, was hyper-intense on T1-weighted magnetic resonance images, and had decreased intensity upon imaging with fat-suppressed sequences. Gross total removal of the tumor was performed. Histopathologically, the tumor was a meningioma with mixed transitional and lipomatous patterns. Immunohistochemically, the meningothelial foci were positive for epithelial membrane antigen (EMA) and vimentin, and negative for S-100 protein. The lipomatous foci were positive for EMA, vimentin, and S-100 protein. The Ki-67 index values of the meningothelial and lipomatous foci were 1.0% and 1.8%, respectively. We review previous reports of lipomatous meningioma and discuss its clinical presentations and pathology.

Foramen of Monro meningioma with atypical appearance: CT and conventional MR findings

Intraventricular meningiomas have often been reported; however, literature reveals very few cases localized within foramen of Monro. Herein we report a 57-year-old woman admitted with obstructive hydrocephalus-related symptoms. Strikingly, the lesion was completely calcified in CT and had no marked solid component on MRI. The lesion was completely removed by surgical resection with a transfrontal intraventricular approach. The resected mass was histopathologically diagnosed as meningioma. The patient's symptoms resolved immediately after the operation.

Lipomatous meningioma: report of 2 cases and review of the literature

BACKGROUND

Lipomatous meningioma is a rare but, most of the time, benign tumor. Its pathogenesis is still debated: it is usually considered to be part of the metaplastic meningioma, but several authors recently suggested that fat accumulation inside the tumor was related to metabolic disorders of the meningothelial cells.

CASES DESCRIPTION

We report 2 cases of lipomatous meningioma. Both patients were women older than 60 years. One patient suffered from headache and seizures, the other one presented with behavioral disturbance. Radiological features depended on the amount of fat accumulation within the tumor. Surgical treatment allowed complete resection in both cases without any complications. Both meningiomas were of transitional-type and were apparently composed of 2 populations of cells: meningothelial cells and lipid-laden cells resembling mature adipocytes. Immunohistochemical study showed that lipid-laden cells expressed EMA, CD99, and progesteron receptor, favoring a meningothelial differentiation rather than an adipocytic lineage.

CONCLUSION

Our study strongly suggests that lipomatous meningioma results from an accumulation of lipid inside meningothelial cells rather than a true metaplasia.