Diffusion-weighted images of intracranial cyst-like lesions

European society of Clinical Microbiology and Infectious Diseases guidelines on diagnosis and treatment of brain abscess in children and adults

SCOPE

These European Society of Clinical Microbiology and Infectious Diseases guidelines are intended for clinicians involved in diagnosis and treatment of brain abscess in children and adults.

METHODS

Key questions were developed, and a systematic review was carried out of all studies published since 1 January 1996, using the search terms 'brain abscess' OR 'cerebral abscess' as Mesh terms or text in electronic databases of PubMed, Embase, and the Cochrane registry. The search was updated on 29 September 2022. Exclusion criteria were a sample size <10 patients or publication in non-English language. Extracted data was summarized as narrative reviews and tables. Meta-analysis was carried out using a random effects model and heterogeneity was examined by I2 tests as well as funnel and Galbraith plots. Risk of bias was assessed using Risk Of Bias in Non-randomised Studies - of Interventions (ROBINS-I) (observational studies) and Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) (diagnostic studies). The Grading of Recommendations Assessment, Development and Evaluation approach was applied to classify strength of recommendations (strong or conditional) and quality of evidence (high, moderate, low, or very low).

QUESTIONS ADDRESSED BY THE GUIDELINES AND RECOMMENDATIONS

Magnetic resonance imaging is recommended for diagnosis of brain abscess (strong and high). Antimicrobials may be withheld until aspiration or excision of brain abscess in patients without severe disease if neurosurgery can be carried out within reasonable time, preferably within 24 hours (conditional and low). Molecular-based diagnostics are recommended, if available, in patients with negative cultures (conditional and moderate). Aspiration or excision of brain abscess is recommended whenever feasible, except for cases with toxoplasmosis (strong and low). Recommended empirical antimicrobial treatment for community-acquired brain abscess in immuno-competent individuals is a 3rd-generation cephalosporin and metronidazole (strong and moderate) with the addition of trimethoprim-sulfamethoxazole and voriconazole in patients with severe immuno-compromise (conditional and low). Recommended empirical treatment of post-neurosurgical brain abscess is a carbapenem combined with vancomycin or linezolid (conditional and low). The recommended duration of antimicrobial treatment is 6-8 weeks (conditional and low). No recommendation is offered for early transition to oral antimicrobials because of a lack of data, and oral consolidation treatment after ≥6 weeks of intravenous antimicrobials is not routinely recommended (conditional and very low). Adjunctive glucocorticoid treatment is recommended for treatment of severe symptoms because of perifocal oedema or impending herniation (strong and low). Primary prophylaxis with antiepileptics is not recommended (conditional and very low). Research needs are addressed.

Reducing Susceptibility Distortion Related Image Blurring in Diffusion MRI EPI Data

Diffusion magnetic resonance imaging (MRI) is an increasingly popular technique in basic and clinical neuroscience. One promising application is to combine diffusion MRI with myelin maps from complementary MRI techniques such as multi-parameter mapping (MPM) to produce g-ratio maps that represent the relative myelination of axons and predict their conduction velocity. Statistical Parametric Mapping (SPM) can process both diffusion data and MPMs, making SPM the only widely accessible software that contains all the processing steps required to perform group analyses of g-ratio data in a common space. However, limitations have been identified in its method for reducing susceptibility-related distortion in diffusion data. More generally, susceptibility-related image distortion is often corrected by combining reverse phase-encoded images (blip-up and blip-down) using the arithmetic mean (AM), however, this can lead to blurred images. In this study we sought to (1) improve the susceptibility-related distortion correction for diffusion MRI data in SPM; (2) deploy an alternative approach to the AM to reduce image blurring in diffusion MRI data when combining blip-up and blip-down EPI data after susceptibility-related distortion correction; and (3) assess the benefits of these changes for g-ratio mapping. We found that the new processing pipeline, called consecutive Hyperelastic Susceptibility Artefact Correction (HySCO) improved distortion correction when compared to the standard approach in the ACID toolbox for SPM. Moreover, using a weighted average (WA) method to combine the distortion corrected data from each phase-encoding polarity achieved greater overlap of diffusion and more anatomically faithful structural white matter probability maps derived from minimally distorted multi-parameter maps as compared to the AM. Third, we showed that the consecutive HySCO WA performed better than the AM method when combined with multi-parameter maps to perform g-ratio mapping. These improvements mean that researchers can conveniently access a wide range of diffusion-related analysis methods within one framework because they are now available within the open-source ACID toolbox as part of SPM, which can be easily combined with other SPM toolboxes, such as the hMRI toolbox, to facilitate computation of myelin biomarkers that are necessary for g-ratio mapping.

Diffusion MR Imaging in the Head and Neck: Principles and Applications

Diffusion imaging is a functional MR imaging tool that creates tissue contrast representative of the random, microscopic translational motion of water molecules within human body tissues. Long considered a cornerstone MR imaging sequence for brain imaging, diffusion-weighted imaging (DWI) increasingly is used for head and neck imaging. This review reports the current state of diffusion techniques for head and neck imaging, including conventional DWI, DWI trace with apparent diffusion coefficient map, diffusion tensor imaging, intravoxel incoherent motion, and diffusion kurtosis imaging. This article describes background physics, reports supportive evidence and potential pitfalls, highlights technical advances, and details practical clinical applications.

Surgical Management of Intracranial Giant Epidermoid Cysts in Adult: A Case-Based Update

Epidermoid cysts (ECs) are benign and slow-growing lesions that account for about 0.2%-2% of all intracranial tumors. Symptoms appear slowly and tumors may have already grown to giant proportions when patients receive their first diagnosis. The optimal treatment for ECs is surgical removal, which includes the total resection of the entire capsule of the lesion in order to minimize the risk of malignant transformation associated with partial removal. However, considering the giant size that the ECs can reach at the time of the diagnosis, and their adherence to the surrounding structures, the risks and benefits of total versus subtotal resections in the short- and long-term patients' outcome are still under debate. Here, we report a case of an extensive giant EC and offer a discussion of its characteristics, surgical management, and postoperative outcome, taking a cue to argue about the recent literature based in the latest case studies.

Intrinsic epidermoid of the brain stem: case report and review of the literature

PURPOSE

Purely cystic brain stem epidermoid is a rare diagnosis among all brainstem cystic lesions. Further, it is very rare in pediatric age group.

METHODS

Here, we are reporting a rare case of completely cystic brain stem epidermoid in a child. The patient presented with clinical features of brain stem involvement. MRI brain was suggestive of cystic brain stem lesion.

RESULTS

Patient went through surgical procedure. Final diagnosis of epidermoid cyst was confirmed on histopathological report.

CONCLUSION

With the help of various advanced sequences of MRI like diffusion and ADC, diagnosis of epidermoid cyst can be established at unusual intracranial site also. Surgical resection of epidermoid cyst at brain stem should be attempted judiciously utilizing all modern tools of neurosurgery.

Suprasellar keratinous cyst: A case report and review on its radiological features and treatment outcome

BACKGROUND

Keratinous or epidermoid cysts (ECs) are encapsulated lesions lined by squamous cell epithelium. They comprise approximately 1% of intracranial lesions. Contrary to dermoid cysts, they lack dermal elements such as sebaceous or apocrine glands and hair follicles. The sellar region is the second most common intracranial site following the cerebellopontine angle. Here, we report a case of EC in a patient who complained of endocrine disturbances. We also performed a systematic review on previously published cases to analyze clinical and radiological characteristics and report the treatment outcomes of suprasellar ECs.

CASE DESCRIPTION

A 42-year-old woman presented with a one-year history of amenorrhea, weight gain, severe headache, and visual disturbances for 6 months. Work-up identified an elevated prolactin level and a temporal field defect of the right eye. Magnetic resonance imaging (MRI) showed a cystic suprasellar lesion pushing on the optic chiasm. She underwent endoscopic trans-sphenoidal surgery, which confirmed a keratinous cyst on histology. Postoperatively, complete resection was confirmed on imaging. She did well although her hospital stay was prolonged due to diabetes insipidus and hypocortisolism.

CONCLUSION

Chronic endocrine disturbances can be the presenting complaints of a suprasellar EC, whose T1-weighted MRI appearance can be non-specific, mimicking other differential diagnoses, such as a Rathke's cleft cyst. However, the T2-weighted MRI appearances of ECs are generally hyper-intense and lesions show diffusion restriction. Treatment is surgical and yields good outcomes in most cases reported.

Brainstem epidermoid cyst: An update

The incidence of epidermoid tumors is between 1% and 2% of all intracranial tumors. The usual locations of epidermoid tumor are the parasellar region and cerebellopontine angle, and it is less commonly located in sylvian fissure, suprasellar region, cerebral and cerebellar hemispheres, and lateral and fourth ventricles. Epidermoid cysts located in the posterior fossa usually arise in the lateral subarachnoid cisterns, and those located in the brain stem are rare. These epidermoids contain cheesy and flaky white soft putty like contents. Epidermoid cysts are very slow growing tumors having a similar growth pattern of the epidermal cells of the skin and develop from remnants of epidermal elements during closure of the neural groove and disjunction of the surface ectoderm with neural ectoderm between the third and fifth weeks of embryonic life. We are presenting an interesting case of intrinsic brainstem epidermoid cyst containing milky white liquefied material with flakes in a 5-year-old girl. Diffusion-weighted imaging is definitive for the diagnosis. Ideal treatment of choice is removal of cystic components with complete resection of capsule. Although radical resection will prevent recurrence, in view of very thin firmly adherent capsule to brainstem, it is not always possible to do complete resection of capsule without any neurological deficits.

Intrathecal gadodiamide for identifying subarachnoid and ventricular neurocysticercosis

OBJECTIVE

Some neurocysticercosis cysts may remain hidden despite novel MRI sequences. This study evaluates the diagnostic value of gadodiamide (GDD)-contrasted MRI cisternography in selected cases of neurocysticercosis.

METHODS

We included patients aged 18-65 years with a probable diagnosis of subarachnoid cysticercosis in whom previous neuroimaging studies failed to demonstrate the presence of cysts. One millilitre of GDD was administered intrathecally as a contrast agent with subsequent performance of MRI.

RESULTS

Fourteen patients were included. Optimal contrast diffusion was achieved in nine patients, and partial diffusion was achieved in 4. Intracranial vesicles were identified in 10 patients, with the presence of more than 60 basal subarachnoid vesicles being revealed in all, with five cysts in the fourth ventricle in four patients and a floating cyst in the lateral ventricle in one. In one case, intrathecal GDD demonstrated spinal cysticercosis. No adverse events were reported after intrathecal GDD administration.

CONCLUSIONS

Intrathecal GDD administration is useful for the diagnosis of subarachnoid and intraventricular neurocysticercosis and can be used to improve diagnostic accuracy in selected cases.

Transpterygoid stent placement for management of a recurrent infratemporal fossa epidermoid cyst: a technical note

Epidermoid cysts (ECs) are benign congenital cysts that typically develop from misplaced stratified squamous epithelium during neural tube closure. They are most commonly encountered in the cerebellopontine angle, the fourth ventricle, and the region of the sella turcica. Recurrence of an EC or regrowth of residual components following surgery is known to occur, but the exact incidence is not defined. Repeat surgical removal is generally considered but may be complicated by significant morbidity. We present a novel endoscopic method by which to manage a recurrent EC of the infratemporal fossa using a silastic stent through a transpterygoid approach that permits periodic drainage of recurrent cyst material in the outpatient setting with minimal morbidity.

DWI findings in a iatrogenic lumbar epidermoid cyst. A case report

Epidermoid cysts comprise less than 1% of intraspinal tumors. They can be congenital, frequently associated with other spinal malformations, or iatrogenic, resulting from the implantation of epidermal cells within the spinal canal during the execution of a variety of procedures such as spinal puncture. At MR imaging epidermoid tumors can mimic cystic lesions with fluid content such as arachnoid cysts. DWI can help obtain a correct diagnosis. We describe a case of iatrogenic lumbar epidermoid cyst with DWI findings in a young woman who had undergone epidural anesthesia for Cesarean section three years before the onset of symptoms.

Epidemiology and management of cysticercosis and Taenia solium taeniasis in Europe, systematic review 1990-2011

BACKGROUND

Cysticercosis is caused by the invasion of human or pig tissues by the metacestode larval stage of Taenia solium. In Europe, the disease was endemic in the past but the autochthonous natural life cycle of the parasite is currently completed very rarely. Recently, imported cases have increased in parallel to the increased number of migrations and international travels. The lack of specific surveillance systems for cysticercosis leads to underestimation of the epidemiological and clinical impacts.

OBJECTIVES

To review the available data on epidemiology and management of cysticercosis in Europe.

METHODS

A review of literature on human cysticercosis and T. solium taeniasis in Europe published between 1990-2011 was conducted.

RESULTS

Out of 846 cysticercosis cases described in the literature, 522 cases were autochthonous and 324 cases were imported. The majority (70.1%) of the autochthonous cases were diagnosed in Portugal from 1983 and 1994. Imported cases of which 242 (74.7%) diagnosed in migrants and 57 (17.6%) in European travellers, showed an increasing trend. Most of imported cases were acquired in Latin America (69.8% of migrants and 44.0% of travellers). The majority of imported cases were diagnosed in Spain (47.5%), France (16.7%) and Italy (8.3%). One third of neurosurgical procedures were performed because the suspected diagnosis was cerebral neoplasm. Sixty eight autochthonous and 5 imported T. solium taeniasis cases were reported.

CONCLUSIONS

Cysticercosis remains a challenge for European care providers, since they are often poorly aware of this infection and have little familiarity in managing this disease. Cysticercosis should be included among mandatory reportable diseases, in order to improve the accuracy of epidemiological information. European health care providers might benefit from a transfer of knowledge from colleagues working in endemic areas and the development of shared diagnostic and therapeutic processes would have impact on the quality of the European health systems.

Reduced diffusion in neurocysticercosis: circumstances of appearance and possible natural history implications

BACKGROUND AND PURPOSE

Few studies discuss DWI findings in patients with NCC, and their conclusions are variable and contradictory. The aim of our study was to describe DWI findings of a cohort of patients with NCC, emphasizing the frequency of reduced diffusion.

MATERIALS AND METHODS

This retrospective study included 48 patients with NCC. Two neuroradiologists analyzed MR images regarding location, number, and stage of NCC lesions. On the basis of visual analysis, they defined, by consensus, the presence of high signal within NCC lesions on DWI and measured their ADC values when feasible.

RESULTS

The total number of lesions was 342: parenchymal (263), subarachnoid (65), and intraventricular (14); 83 were DWI hyperintense. The first pattern was a small eccentric hyperintense dot/curvilinear structure on DWI (representing the scolex) noted in intraparenchymal lesions in vesicular (41 lesions, 29%) and colloidal vesicular (18 lesions, 19%) stages, in 14 (22%) subarachnoid lesions, and 2 (14%) intraventricular lesions; rADC calculations were hampered by the intrinsic small dimensions of this finding. The second pattern was the presence of total/subtotal DWI hyperintensity in intraparenchymal lesions, 5 in the colloidal vesicular stage (5%) and 1 in the granular nodular phase (3%). Two subarachnoid lesions also showed the same presentation; in this second pattern, reduced diffusion was present in different degrees, measured by rADC calculations.

CONCLUSIONS

DWI may identify the scolex, increasing diagnostic confidence for NCC. Total/subtotal DWI hyperintensity, related to the stage of the lesion, though uncommon, allows including NCC as a consideration in the differential diagnosis of lesions with reduced diffusion and ring enhancement.

Endoscopic endonasal approach for resection of ventral skull base keratinaceous cysts

BACKGROUND

Epidermoid and dermoid cysts are uncommon entities that belong in the differential diagnosis of ventral skull base lesions. The endoscopic endonasal approach is an attractive option for management of these lesions with limited morbidity. The clinical characteristics and management course from our experience is reviewed along with the relevant literature.

METHODS

A prospective database of endoscopic endonasal skull base cases performed since 2003 at a tertiary referral center was reviewed for cases involving keratinaceous lesions. Data on the pathology, radiology and management of the disease was reviewed. A search of pertinent literature using Medline was performed to complement the discussion.

RESULTS

Three cases of intracranial keratinaceous cysts successfully managed with the endoscopic endonasal approach. All cases presented with headache, and 1 case presented with bitemporal hemianopsia. Characteristic appearance on magnetic resonance imaging was seen in each case. All lesions were intradural with variable involvement of the suprasellar, prepontine, and premedullary cisterns. Total resection was achieved in 2 cases and near total resection in 1 case. Postoperative cerebrospinal fluid leak occurred in one case, which was controlled after revision surgery using the "gasket-seal" technique. There were no cranial nerve palsies or vascular events.

CONCLUSION

The endoscopic endonasal approach allows the rhinologic surgeon to access the ventral midline skull base for the successful management of keratinaceous cysts without major complications.

Role of magnetic resonance imaging in cholesteatoma: the Indian experience

The objectives are to evaluate role of magnetic resonance imaging (MRI) in diagnosis of cholesteatoma and correlate imaging findings with intraoperative findings, and to emphasize of role of imaging in the follow-up of postoperative patients for differentiating residual/recurrent cholesteatoma from granulation/inflammatory tissue. In this prospective study, 31 patients were evaluated with a specific MRI protocol and high resolution computed tomography of the temporal bones. These included patients with a strong suspicion of having a cholesteatoma on clinical examination and postoperative cases on clinical follow up. Based on specific MRI findings, presence of cholesteatoma was reported in 17 out of 31 patients. All 31 patients underwent surgery and 19 patients had confirmed intraoperative cholesteatoma. This study shows high sensitivity of a specific sequence based MRI examination in detection of cholesteatoma and in differentiating cholesteatoma from postoperative inflammatory/granulation tissue. To the best of the author's knowledge, this is the first such study performed in the Indian Asian population.

[Imaging of lateral ventricle tumors]

Lateral ventricular neoplasms are rare, and account for 50% of all intraventricular tumors in adults and 25% in children. Although these neoplasms are easily detected with computed tomography (CT) and magnetic resonance imaging (MRI), both techniques are relatively unspecific in identifying the type of tumor. However, few imaging patterns are specific for a particular pathological process and useful conclusions can be made from the morphological appearance of the lesion, its location and enhancement pattern. The aim of this article was to review and illustrate the CT and MRI findings of a wide spectrum of tumors of the lateral ventricle. We reviewed choroid plexus tumors, meningioma, subependymal giant cell astrocytoma, central neurocytoma, and less frequent lesion such as lymphoma and metastases.

Clinical characteristics and diagnostic imaging of epidermoid tumors

Epidermoid tumors are rare, benign congenital lesions which typically present between the third and fifth decades of life. They are thought to originate from ectodermal cells misplaced during neural tube formation and separation. While epidermoids may present anywhere in the cranial vault, they are characteristically located intradurally and in a paramedian position within the cerebellopontine angle and parasellar regions. Although imaging results may vary depending upon cystic content, CT scanning generally reveals a well-circumscribed, nonenhancing, lobulated, hypodense mass. They are hypointense on T1-weighted MRI, and hyperintense on T2-weighted MRI, diffusion-weighted imaging and fluid-attenuated inversion recovery sequences. The use of appropriate neuroimaging should be utilized to differentiate epidermoids from other intracranial lesions. While gross total resection of these tumors is the definitive treatment to prevent recurrence and aseptic meningitis, a subtotal resection may be necessary to preserve neurological function.

[Diffusion-weighted imaging in neuroradiology]

Diffusion-weighted imaging is becoming increasingly more important in neuroradiology. Formerly this technique was mainly used in stroke diagnostics but the spectrum of applications is becoming increasingly larger. Diffusion-weighted imaging is a useful tool for differentiation between metastases and abscesses, for assessment of the depth of invasiveness of tumors and to differentiate inflammation from astrocytomas. It has now become a standard technique in multiple sclerosis imaging. A further advantage in addition to the diagnostic capabilities is the speed of the sequence which makes it insensitive to movement artefacts.

Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts

PURPOSE

To explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in characterizing the structural pathology of epidermoid cysts. DTI gives information about the tissue structure; a high fractional anisotropy (FA) indicates a highly structured orientation of the tissue, fibers, or white matter tracts. Based on the tensor rank, a set of three metrics has been described that can be used to measure the directional dependence of diffusion: linear anisotropy (CL), planar anisotropy (CP), and spherical anisotropy (CS). DTM takes into account the shape of diffusion anisotropy and hence may provide better insight into the orientation of structures than FA.

MATERIALS AND METHODS

DTI was performed in three patients with epidermoid cysts. FA, directionally-averaged mean diffusivity (Dav), exponential apparent diffusion coefficient (eADC), and DTM, such as CL, CP, and CS, were measured from the tumor core as well as from the normal-appearing white matter. Histopathological correlation was obtained.

RESULTS

Epidermoid cysts showed high FA with Dav values similar to that of normal white matter. eADC maps did not show any restriction of diffusion. FA values were high, but not as high as that for the white matter. CP values were higher and CL values were lower than those obtained for the white matter in various regions.

CONCLUSION

High CP values suggest preferential diffusion of water molecules along a two-dimensional geometry, which could be attributed to the well-structured orientation of keratin filaments and flakes within the tumor as demonstrated by histopathology. Advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts.

3T MR imaging of postoperative recurrent middle ear cholesteatomas: value of periodically rotated overlapping parallel lines with enhanced reconstruction diffusion-weighted MR imaging

BACKGROUND AND PURPOSE

MR diagnostic of postoperative recurrent cholesteatomas is difficult. Our purpose was to compare multishot fast spin-echo periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted MR imaging (DWI) with array spatial sensitivity encoding technique (ASSET) single-shot echo-planar DWI and late postgadolinium T1-weighted MR imaging for the detection of postoperative recurrent middle ear cholesteatomas with a 3T imaging unit.

MATERIALS AND METHODS

Thirty-five patients with suggested postoperative recurrent middle ear cholesteatoma underwent 3T MR imaging with PROPELLER DWI, ASSET echo-planar DWI, and late postgadolinium T1-weighted MR imaging. Three radiologists (2 seniors, 1 fellow) analyzed unlabeled images for visualization of recurrence. Interobserver and intraobserver agreement was assessed by using the Cohen kappa statistic test. Sensitivity, specificity, and predictive value were assessed for the 3 observers.

RESULTS

Nineteen recurrent cholesteatomas were diagnosed. PROPELLER interobserver agreement was very good (1, 0.89, 0.89) among the 3 observers. Intraobserver agreement between PROPELLER and T1-weighted imaging was very good to moderate (0.88, 0.57, 0.58). PROPELLER DWI provided less interobserver variability than other sequences, and the best sensitivity, specificity, and predictive value.

CONCLUSIONS

On a 3T imaging unit, multishot fast spin-echo PROPELLER DWI allows an easier detection of postoperative recurrent middle ear cholesteatoma than T1-weighted imaging by reducing artifacts and by its better contrast. DWI with PROPELLER is diagnostically robust and accurate.

The role of diffusion-weighted magnetic resonance imaging in intracranial cystic lesions

We aimed to define the diffusion-weighted magnetic resonance (MR) imaging features of intracranial cystic lesions and to investigate possible special features for the differential diagnosis. One hundred and twenty patients with intracranial cystic lesions were included in the study. There were 29 arachnoid cysts, eight epidermoid cysts, 34 primary tumors, 18 abscesses, 29 metastases and two hydatid cysts. Echo-planar diffusion-weighted MR imaging was obtained in addition to conventional cranial MR scans. The morphologic features of the cystic portion and the wall of the cyst and signal intensities on diffusion-weighted images were evaluated. All abscesses and epidermoid cysts were hyperintense on diffusion-weighted images. Arachnoid cysts, hydatid cysts, primary tumors, and metastases were hypointense except five cystic tumors. These five primary or metastatic necrotic tumors showed high signal intensity on diffusion-weighted images due to hemorrhage or superinfection. The walls of the cystic tumors were usually hyperintense on diffusion-weighted images in contrast to the wall of the abscesses, which were iso-hypointense. This was a statistically significant finding for the differentiation between tumors and abscesses (p<0.05). Diffusion-weighted MR imaging is a useful technique for the evaluation of the intracranial cystic lesions and provides additional beneficial information to conventional MR imaging. However, the presence of hemorrhage and superinfection of the tumors may cause a signal increase that results in misinterpretetations. In these cases, the appearance of tumor wall may be useful for differentiating abscesses from tumors.

Diffusion tensor mode in imaging of intracranial epidermoid cysts: one step ahead of fractional anisotropy

INTRODUCTION

The signal characteristics of an epidermoid on T2-weighted imaging have been attributed to the presence of increased water content within the tumor. In this study, we explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in knowing the microstructural anatomy of epidermoid cysts.

MATERIALS AND METHODS

DTI was performed in ten patients with epidermoid cysts. Directionally averaged mean diffusivity (D(av)), exponential diffusion, and DTM-like fractional anisotropy (FA), diffusion tensor mode (mode), linear (CL), planar (CP), and spherical (CS) anisotropy were measured from the tumor as well as from the normal-looking white matter.

RESULTS

Epidermoid cysts showed high FA. However, D(av) and exponential diffusion values did not show any restriction of diffusion. Diffusion tensor mode values were near -1, and CP values were high within the tumor. This suggested preferential diffusion of water molecules along a two-dimensional geometry (plane) in epidermoid cysts, which could be attributed to the parallel-layered arrangement of keratin filaments and flakes within these tumors.

CONCLUSION

Thus, advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts.

Proton magnetic resonance spectroscopy and diffusion-weighted imaging in intracranial cystic mass lesions

BACKGROUND

The differential diagnosis of various intracranial cystic lesions is sometimes difficult on the basis of CT or MRI findings. Our objective was to evaluate (1)H MRS and DWI in the differential diagnosis of these lesions and in comparison with conventional MRI.

METHODS

Fifty patients with intracranial cystic lesions (21 pyogenic abscesses, 23 tumor cysts, 3 epidermoid cysts, and 3 arachnoid cysts) were evaluated with conventional MRI, DWI, and in vivo (1)H MRS. Preoperative diagnosis of the lesions was based on the results of DWI and in vivo MRS. All DWI and (1)H MRS studies were performed with a clinical 1.5-T system. The DWI was performed using single-shot spin-echo echo-planar pulse sequence with b = 1000 s/mm(2). The ADC value was measured. Diagnostic accuracy of conventional MRI, DWI, and in vivo (1)H MRS was calculated with respect to a final diagnosis of brain abscess vs nonabscess cystic tumor.

RESULTS

Lactate and cytosolic amino acids with/without succinate, acetate, and alanine were observed in 18 of 21 cases of abscesses on MRS. In 3 cases of epidermoid cysts, lactate was observed and could be differentiated from 3 cases of arachnoid cysts, which showed only minimal lactate. Only lactate was seen in 14 of 23 patients with tumor cysts, whereas both lipid/lactate and choline were visible in 9 patients with tumor cysts. Increased signal was seen in 20 of 21 patients with abscesses and 3 patients with epidermoid cysts on DWI. Decreased signal was observed in 22 of 23 patients with tumor cysts and 3 patients with arachnoid cyst on DWI. Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of conventional MRI for the differentiation of brain abscess from nonabscess cystic tumor were 61.4%, 61.9%, 60.9%, 59.1%, and 63.6%, respectively, whereas they were 93.2%, 85.7%, 100%, 100%, and 88.5% with MRS; 95.5%, 95.2%, 95.7%, 95.2%, and 95.7% with DWI; and 97.7%, 95.2%, 100%, 100%, and 95.8% with MRS and DWI. Magnetic resonance imaging, when combined with in vivo MRS and DWI, accurately predicted the diagnosis in 47 (94%) of 50 and 48 (96%) of 50 of the cases, respectively.

CONCLUSIONS

Proton MRS and DWI are useful as additional diagnostic modalities in differentiating intracranial cystic lesions. Combination of DWI with calculated ADC values and metabolite spectrum acquired by MRS add more information to MRI in the differentiation of intracranial cystic mass lesions.

Benign mass lesions deep inside the temporal bone: imaging diagnosis for proper management

CONCLUSION

Among mass lesions inside the temporal bone, benign tumors and cholesteatomas can be differentiated by contrast enhancement in T1-weighted images (T1WI) and by diffusion-weighted images (DWI). Moreover, DWI will also facilitate discrimination between cholesteatomas accompanied by granulation and other non-neoplastic lesions such as mucoceles and cholesterol granulomas.

OBJECTIVES

To review the imaging characteristics of mass lesions inside the temporal bone and to investigate pertinent imaging modalities for differential diagnosis, which is crucial for appropriate treatment planning.

PATIENTS AND METHODS

This was a retrospective case series study of six patients seen between 2002 and 2005 with mass lesions deep inside the temporal bone.

RESULTS

One patient had facial schwannoma, two had glomus jugulare tumor, and three had cholesteatoma. Plain high resolution CT gave few clues to the nature of the mass lesions. MRI study provided us with better clues: contrast enhancement on T1WI was observed only in benign tumors and only cholesteatomas showed high intensity on DWI. With the assistance of neurosurgeons, surgery was successfully performed in all cases.

Epidermoid cysts of the cerebellopontine angle with extension into the middle and anterior cranial fossae: surgical strategy and review of the literature

Epidermoid cysts are tumours, which contain keratin, cellular debris and cholesterol, and lined with stratified squamous epithelium. Clinically, epidermoid cysts behave like benign, slow-growing lesions. We present a 63 year-old man with a 6-month history of right periorbital pain and hypaesthesia in the area of the first and second branch of the trigeminal nerve. MRI revealed an epidermoid cyst of the cerebellopontine angle extending into the middle and anterior cranial fossae. Radical surgical removal of epidermoid cysts should be attempted, but a less aggressive surgical strategy should be considered if there is strong adherence to the surrounding brain tissue, particularly in eloquent areas. In this case, complete tumour removal was achieved via a suboccipital retrosigmoid approach.

Advanced neuroimaging of pediatric brain tumors: MR diffusion, MR perfusion, and MR spectroscopy

This article highlights the MR imaging techniques of MR perfusion, MR diffusion, and MR spectroscopy in the evaluation of the child with a pediatric brain tumor. These techniques are complementary to conventional MR imaging in providing tumor physiologic information useful for diagnosis and therapy.

Diffusion Tensor Magnetic Resonance Imaging of Brain Tumors

DTI seems to offer the possibility of adding important information to presurgical planning. Although experience is limited, DTI seems to provide useful local information about the structures near the tumor, and this seems to be useful in planning. In the future, DTI may provide an improved way to monitor intraoperative surgical procedures as well as their complications. Furthermore, evaluation of the response to treatment with chemotherapy and radiation therapy might also be possible. Although DTI has some limitations, its active investigation and further study are clearly warranted.

Intrinsic brainstem epidermoid cyst. Case report and review of the literature

Brainstem epidermoid cysts are rare lesions, with only 18 reported cases in the literature and only five purely intrinsic epidermoid cysts within this group. The authors present the case of a 3-year-old girl with a history of chronic headaches, progressive diplopia, and relapsing and remitting mild right hemiparesis who was found to harbor an intrinsic brainstem epidermoid cyst at the pontomedullary junction. Initial working diagnoses included intrinsic brainstem astrocytoma and cavernoma. After tumor enlargement and progressive symptoms, a diffusion-weighted (DW) magnetic resonance (MR) imaging sequence was performed and a definitive diagnosis of an intrinsic brainstem epidermoid cyst was made in the patient. The patient underwent a suboccipital craniotomy and complete resection of the cyst with the aid of intraoperative neurophysiological monitoring. Three years after the operation, the patient is neurologically intact and no evidence of tumor recurrence has been found. The rarity of brainstem epidermoid cysts can make their diagnosis difficult; thus a DW MR imaging sequence of the brain is a useful diagnostic modality. Intrinsic brainstem epidermoid cysts can be removed safely, in a manner similar to that used for the surgical treatment of focal tumors.

Endonasal transsphenoidal transclival removal of prepontine epidermoid tumors: technical note

OBJECTIVE

Prepontine retroclival tumors have typically been removed through a variety of anterolateral, lateral, and posterolateral cranial base approaches. Here, we describe an endonasal transclival cranial base approach for removal of prepontine epidermoid tumors.

METHODS

Two men, 40 and 52 years old, each presented with a history of headaches and cranial nerve deficits. In each patient, magnetic resonance imaging showed a large T1 hypointense/T2 hyperintense mass occupying the posterior suprasellar, premesencephalic, and prepontine cisterns, with significant mass effect on the brainstem. Both patients underwent an endonasal transsphenoidal transclival cranial base tumor removal with the operating microscope and endoscopic assistance. The dural and bony defects were repaired with abdominal fat grafts, collagen sponge, titanium mesh, and cerebrospinal fluid diversion. One patient developed a postoperative cerebrospinal fluid leak and meningitis requiring two reoperations to repair, ultimately with fat and fascia lata grafts.

RESULTS

At 1 year after surgery, both patients have improved compared with their preoperative neurological state, and volume analysis of preoperative and 1-year postoperative magnetic resonance imaging scans confirm a marked reduction in mass effect on the brainstem, with a 78% tumor removal in one patient and 76% removal in the other. Both patients have normal endocrine function.

CONCLUSION

The endonasal approach offers a minimally invasive, anatomically direct route for removing prepontine epidermoid tumors that obviates brain retraction. The use of angled endoscopes is essential for gaining lateral, cephalad, and caudal visualization to augment the limited microscope view. Inadequate repair of clival dural defects remains the greatest potential pitfall in attempting transsphenoidal transclival tumor removal.

Diffusion-weighted MR imaging sequence in the detection of postoperative recurrent cholesteatoma

PURPOSE

To prospectively evaluate a fast spin-echo (SE) diffusion-weighted sequence for magnetic resonance (MR) imaging of recurrent cholesteatoma in patients who have undergone middle ear surgery.

MATERIALS AND METHODS

The study was approved by the institutional review board, and informed consent was obtained from all patients. Twenty-four patients (10 female and 14 male patients; mean age, 44 years) who had undergone resection of cholesteatoma were referred for MR imaging. MR imaging was performed with a 1.5-T unit by using unenhanced diffusion-weighted fast SE imaging at b factors of 0 and 800 sec/mm(2), unenhanced T2-weighted fast SE imaging, unenhanced T1-weighted SE imaging, and delayed contrast material-enhanced T1-weighted imaging. Two radiologists evaluated the diffusion-weighted fast SE images for the presence of a high-signal-intensity cholesteatoma. Results from MR imaging were compared with reports from second- or third-look surgery. Interobserver agreement was assessed with the kappa statistic.

RESULTS

A recurrent cholesteatoma was correctly identified in 13 of 14 patients with diffusion-weighted fast SE images obtained with a b factor of 800 sec/mm(2), for a positive predictive value of 93%. In patients without recurrent cholesteatoma, all diffusion-weighted fast SE MR images obtained with a b factor of 800 sec/mm(2) were correctly interpreted as showing no high signal intensity. Thus, the negative predictive value was 100%. Sensitivity and specificity were 100% (13 of 13 patients) and 91% (10 of 11 patients), respectively. Interobserver agreement was excellent (kappa = 0.92). The smallest recurrent cholesteatoma was 5 mm in diameter, and this was correctly detected with the diffusion-weighted fast SE sequence.

CONCLUSION

Diffusion-weighted fast SE imaging enables the depiction of recurrent cholesteatoma in patients who have undergone middle ear surgery.

Imaging of posterior fossa epidermoid tumors

OBJECTIVE

Epidermoid tumors have similar radiologic characteristics with arachnoid cysts on routine imaging techniques. Since they warrant different therapeutic interventions, it is essential to differentiate the two pathologies and to assess operative results.

PURPOSE

The purpose of this study is to define the MR characteristics of epidermoid tumors in posterior fossa particularly on fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI).

PATIENTS AND METHODS

During a 10-year period, we operated 19 cases with epidermoid tumor of posterior fossa. The localization of the epidermoids was cerebellopontine angle in 16 patients, within the fourth ventricle in 2 patients and pineal region in 1 patient. Neuroimaging included CT in all patients, conventional MR in 14 patients and FLAIR and DWI in the last 6 patients.

RESULTS

In the first 13 cases, diagnosis of epidermoid tumor was difficult on CT and conventional MR. Epidermoids appeared as heterogeneous hyperintense lesions on FLAIR and homogenous hyperintense lesions on DWI in the last 6 patients. While total resection of the tumor was achieved in 17 patients, subtotal resection was performed in 2 patients. Histopathological examinations of the specimens revealed epidermoid tumor in all cases.

CONCLUSION

Advances in neuroradiology provide us advantages for planning the treatment modalities in epidermoid tumors of the posterior fossa. The difficulties in preoperative differential diagnosis and judgment for reoperation in the postoperative course have been decreased particularly via FLAIR and DWI.

Diffusion tensor magnetic resonance imaging of brain tumors

DTI seems to offer the possibility of adding important information to presurgical planning. Although experience is limited, DTI seems to provide useful local information about the structures near the tumor, and this seems to be useful in planning. In the future, DTI may provide an improved way to monitor intraoperative surgical procedures as well as their complications. Furthermore, evaluation of the response to treatment with chemotherapy and radiation therapy might also be possible. Although DTI has some limitations, its active investigation and further study are clearly warranted.

Cerebral Fractional Anisotropy Score in Trauma Patients:A New Indicator of White Matter Injury After Trauma

OBJECTIVE

Previous studies evaluating quantitative cerebral white matter diffusion anisotropy indexes have shown alteration in patients after trauma. To date, no clinically applicable scale exists by which to gauge and test the relevance of these findings. We propose the cerebral fractional anisotropy score in trauma (C-FAST) as an index of white matter injury, and we correlate C-FAST with several predictor and outcome variables.

MATERIALS AND METHODS

Fifteen patients were randomly selected from the trauma surgery service. Thirty control patients were randomly selected from the emergency department. All patients were subjected to MRI evaluation, including a diffusion-weighted sequence. Data extracted from the record of each subject included Glasgow Coma Scale, revised trauma score, Abbreviated Injury Scale, initial head CT results, patient disposition, length of hospital stay, and length of stay in intensive care unit. Region of interest measurements were made in fractional anisotropy maps in each of 12 white matter regions. Univariate statistics and a two-tailed t test were performed on the raw fractional anisotropy data. Data were then dichotomized using thresholds from univariate statistics. A C-FAST score was devised from the dichotomized data. Logistic regression analyses were performed among the C-FAST, outcome, and predictor data.

RESULTS

Good correlation was noted between the C-FAST and death, hospital stay greater than 10 days, and intensive care unit stay greater than 5 days. Correlation with discharge to rehabilitation facility was good when adjusted for age and sex. Glasgow Coma Scale, revised trauma score, and Abbreviated Injury Scale show good correlation as predictors of a critical C-FAST.

CONCLUSION

The C-FAST is a promising index derived from MRI diffusion fractional anisotropy measurements that shows successful correlation with outcome and predictor variables. A larger investigation is needed to verify the validity and stability of the correlations.

Imaging of brain tumors with diffusion-weighted and diffusion tensor MR imaging

The advent of diffusion-weighted MR imaging and diffusion tensor MR imaging has had little impact on brain tumor detection. Diffusion-weighted imaging has been effective in characterizing specific types of masses, particularly in distinguishing epidermoids from arachnoid cysts, and cystic tumors from intracerebral abscesses. Presurgical planning using tractography with diffusion tensor MR imaging, and perhaps the evaluation of tumor response to chemotherapy and radiation therapy with diffusion-weighted imaging, may become important applications in the near future.

Diffusion-weighted MR imaging of cholesteatoma in pediatric and adult patients who have undergone middle ear surgery

OBJECTIVE

The aim of this prospective study was to determine the role of diffusion-weighted MR imaging combined with conventional MR imaging for the detection of residual or recurrent cholesteatoma in patients who have undergone middle ear surgery.

SUBJECTS AND METHODS

Twenty-two patients who had undergone resection of cholesteatoma were referred for MR imaging. MR imaging (1.5 T) was performed using a diffusion-weighted single-shot spin-echo echoplanar sequence, a proton density and T2-weighted double-echo turbo spin-echo sequence, and T1-weighted spin-echo sequences before and after IV injection of gadopentetate dimeglumine (0.1 mmol/kg of body weight). An experienced reviewer evaluated the diffusion-weighted MR images for the presence of a high-signal-intensity cholesteatoma. Imaging findings were correlated with findings from surgery in 17 patients and with findings from clinical follow-up examination in five patients.

RESULTS

Diffusion-weighted MR imaging combined with conventional MR imaging depicted 10 of 13 cholesteatomas (sensitivity, 77%). The three lesions that were missed were smaller than 5 mm. All the MR images of patients without cholesteatoma were correctly interpreted as showing negative findings for cholesteatoma (specificity, 100%). The positive predictive value and negative predictive value were 100% and 75%, respectively.

CONCLUSION

Diffusion-weighted MR imaging combined with conventional MR imaging can confirm residual or recurrent cholesteatoma in patients who have undergone middle ear surgery by showing a high-signal-intensity lesion. Because tumors smaller than 5 mm may be missed, a diffusion-weighted MR imaging study with negative findings does not exclude small residual or recurrent cholesteatoma.

MR Imaging of Epidermoids at the Cerebellopontine Angle

The most common location of intracranial epidermoid is the cerebellopontine angle (CPA). The present study compared the visibility of epidermoid at the CPA in various pulse sequences. Seven patients with epidermoid at the CPA underwent conventional MR imaging (T(1)-, T(2)- and proton density-weighted imaging) as well as diffusion-weighted echo-planar imaging. Fast fluid-attenuated inversion recovery (FLAIR) sequences, magnetization transfer contrast (MTC) sequences, and MR cisternography were employed for selected patients. The signal intensity of the lesions relative to cerebrospinal fluid (CSF), the degree of lesion demarcation and the displacement of surrounding structures were evaluated. Proton density-weighted imaging depicted the lesions as hyper-intense to CSF with clearer delineation than T(1)- and T(2)-weighted imaging. Diffusion-weighted imaging depicted all lesions as strongly hyper-intense relative to CSF and brain tissue. FLAIR sequences depicted the lesions with mixed signal intensities but with poor-to-medium demarcation. MTC imaging increased delineation of the lesions to some degree. MR cisternography depicted the lesions as hypo-intense to CSF and clearly showed the anatomical relation to neighboring nerves and vessels. We concluded that diffusion-weighted imaging could specifically reveal an epidermoid at the CPA as a strongly hyper-intense lesion, and that MR cisternography is mandatory for preoperative planning.

Use of diffusion-weighted magnetic resonance imaging in differentiating purulent brain processes from cystic brain tumors

OBJECT

Brain abscesses and other purulent brain processes represent potentially life-threatening conditions for which immediate correct diagnosis is necessary to administer treatment. Distinguishing between cystic brain tumors and abscesses is often difficult using conventional imaging methods. The authors' goal was to study the ability of diffusion-weighted (DW) magnetic resonance (MR) imaging to differentiate between these two pathologies in patients within the clinical setting.

METHODS

Diffusion-weighted MR imaging studies and calculation of the apparent diffusion coefficient (ADC) values were completed in a consecutive series of 16 patients harboring surgically verified purulent brain processes. This study group included 11 patients with brain abscess (one patient had an additional subdural hematoma and another also had ventriculitis), two with subdural empyema, two with septic embolic disease, and one patient with ventriculitis. Data from these patients were compared with similar data obtained in 16 patients matched for age and sex, who harbored surgically verified neoplastic cystic brain tumors. In patients with brain abscess, subdural empyema, septic emboli, and ventriculitis, these lesions appeared hyperintense on DW MR images, whereas in patients with tumor, the lesion was visualized as a hypointense area. The ADC values calculated in patients with brain infections (mean 0.68 x 10(3) mm2/sec) were significantly lower than those measured in patients with neoplastic lesions (mean 1.63 x 10(3) mm2/sec; p < 0.05).

CONCLUSIONS

Diffusion-weighted MR imaging can be used to identify infectious brain lesions and can help to differentiate between brain abscess and cystic brain tumor, thus making it a strong additional imaging modality in the early diagnosis of central nervous system purulent brain processes.