Diffusion-weighted magnetic resonance imaging and magnetic resonance spectroscopy in the evaluation of focal cerebral tubercular lesions

Role of Multiparametric Magnetic Resonance Imaging of the Brain in Differentiating Neurocysticercosis From Tuberculoma

INTRODUCTION

The two most common infectious causes of ring-enhancing lesions are neurocysticercosis (NCC) and tuberculoma. It is a challenge to differentiate NCC and tuberculomas radiologically since they show the same imaging findings on computed tomography (CT). Hence, this study was performed to assess the role of magnetic resonance imaging (MRI) as an additional advanced modality to aptly characterize the lesion. Conventional MRI with additional advanced imaging sequences like diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC), magnetic resonance spectroscopy (MRS), and post-contrast T1-weighted imaging (T1WI) aids in characterizing the lesion and helps in differentiating NCC and tuberculomas.

OBJECTIVES

To compare the findings of DWI, ADC cut-off values, spectroscopy, and contrast-enhanced MRI in differentiating NCC from tuberculoma.

MATERIALS AND METHODS

Individuals who matched the inclusion criterion underwent an MRI of the brain (plain and contrast) in a 1.5 Tesla, 18-channel, magnetic resonance scanner (Magnetom Avanto®, Siemens Healthineers, Erlangen, Germany). The following imaging sequences were included: T1WI (axial and sagittal), T2-weighted imaging (axial and coronal), fluid-attenuated inversion recovery, DWI at 0, 500, and 1000 mm²/s b-values with corresponding ADC values, and single-voxel MRS. Based on MRI features such as number, size, location, margins of lesions, scolex, surrounding edema, DWI features with corresponding ADC values, enhancement pattern of lesions, and spectroscopy findings, we evaluated and differentiated the lesions as NCC or tuberculoma. Radiological diagnoses were correlated in terms of clinical symptoms and response to treatment.

RESULTS

In our study, 42 subjects were included, of which the total number of NCC cases was 25 (59.52%) and tuberculoma was 17 (40.47%). The mean age of patients included was 42.85 ± 14.76 years (21 to 78 years). On post-contrast imaging, all 25 cases of NCC (100%) showed thin ring enhancement whereas the majority of tuberculomas (64.7%) showed thick irregular ring enhancement. On MRS, all 25 cases (100%) of NCC showed an amino acid peak and all 17 cases (100%) of tuberculoma showed a lipid lactate peak. On DWI, out of 25 NCC cases, restriction of diffusion was absent in the majority of cases (88%) and out of 17 cases of tuberculoma, restriction of diffusion was present in 12 cases (70.5%) (T2 hyperintense tuberculoma, indicative of caseating tuberculoma with central liquefaction) and was absent in the rest. In our study, the mean ADC value of NCC lesions (1.30 ± 0.137 x 10^-3 mm²/s) was found to be greater than that of tuberculoma (0.74 ± 0.090 x 10^-3 mm²/s). ADC value of 1.2 x 10^-3 was obtained as a cut-off to differentiate NCC and tuberculoma. The ADC cut-off value of 1.2 x 10^-3 mm²/s showed a sensitivity of 92% and specificity of 94.1% in differentiating NCC from tuberculoma.

CONCLUSIONS

Conventional MRI with additional advanced imaging sequences like DWI, ADC, MRS, and post-contrast T1WI aids in characterizing the lesion and thereby helps in differentiating NCC and tuberculomas. Hence, multiparametric MRI assessment is useful in making a prompt diagnosis and eliminating the need for a biopsy.

Magnetic Resonance Imaging Appearance of Giant Intracerebral Tuberculoma: A Retrospective Analysis

Background: Giant intracerebral tuberculomas are rare lesions but should be considered in the differential diagnosis of intracranial space-occupying lesion in an endemic region.Objective: The purpose of this study is to analyze the clinical data and magnetic resonance imaging (MRI) findings of giant intracerebral tuberculomas to improve the diagnostic precision.Material and Methods: The clinical and MRI findings of 22 patients of giant intracerebral tuberculoma were analyzed retrospectively. For the statistical analysis independent sample Student t-test was used.Results: For 22 patients included in this sample the giant intracerebral tuberculoma was of size more than 2.5cm. The majority of the giant tuberculomas (19 patients (86.4%))was located in the supratentorial area.T2-weighted hypointense core of giant tuberculoma was observed in 12 patients (54.5%) and T1 hyperintensities were observed in peripheral (wall) of the giant tuberculoma in 14 patients (63.6%). The mean ADC value of the peripheral (wall) of the giant tuberculoma was 1.034± 0.466[SD] x 10-3mm2/s and the core was 0.994± 0.455[SD] x 10-3mm2/s with a statistically significant difference (p-value <0.0005) in between. MR spectroscopy showed raised lipid peak at 0.9 to 1.33 ppm in 10 patients (45.5%),raised lipid-lactate peak in 12 patients (54.5%),raised Choline/Cr ratio more than 1.2 in 14 patients(63.6%) and Choline/Cr ratio less than 1.2 in 5 patients (22.7%). Associated involvement of lung was observed in the 6patients (27.3%), cervical lymph node in 1 patient (4.5%) and spine in 1patient (4.5%).Conclusions: MRI plays a vital role in distinguishing giant intracerebral tuberculomas from other intracranial space-occupying lesions, thereby allows the early institution of anti-tubercular treatment (ATT), decreased patient morbidity, mortality, and prevents unnecessary neurosurgical excision.

Diagnostic and Neurological Overview of Brain Tuberculomas: A Review of Literature

Tuberculosis is a disease caused by a bacteria named Mycobacterium tuberculosis (M. tb). It is estimated by World Health Organization (WHO) that nearly a quarter of the world's population is infected. Tuberculoma of the brain is one of the most severe extrapulmonary forms that affects patients younger than 40 years of age. Brain parenchymal tuberculoma develops in nearly one of 300 non-treated cases of pulmonary tuberculosis cases. In endemic regions, tuberculomas account for as many as 50% of all intracranial masses. Tuberculoma results in a hematogenous spread of M. tb from an extracranial source. Tuberculomas can mimic a variety of diseases and can present themselves in a subacute or chronic course, from asymptomatic to severe intracranial hypertension. Diagnosis is based on computed tomography (CT) scan and magnetic resonance imaging (MRI) studies with a similar ring-enhancing lesion. Treatment is primarily medical, and the duration for brain tuberculoma can vary from six to 36 months. In certain cases, surgery is recommended.

Meningeal tuberculoma mimicking a brain tumor

Meningeal tuberculoma is one of the most serious sites of tuberculosis. Its incidence varies depending on the geographical area, rare in Western countries and frequent in developing countries where it represents 5% to 10% of intracranial masses. We report the case of a 21-year-old male patient with no particular medical history from Africa and living in Europe for more than a year, is hospitalized for an isolated inaugural, generalized, afebrile seizure in whom the scanner and cerebral magnetic resonance imaging (MRI) revealed a meningeal mass with significant glove finger edema suggesting a primary brain tumor. Surgical excision and anatomopathological analysis of the excisional piece allowed the diagnosis of tuberculoma. Meningeal tuberculoma is a source of diagnostic error because its clinical and radiological expression can mimic a brain tumor. This is an etiology that should not be ignored in the face of a meningeal mass in any subject coming from or living in a region with a high endemic tuberculosis.

Management of intracranial tuberculous mass lesions: how long should we treat for?

Tuberculous intracranial mass lesions are common in settings with high tuberculosis (TB) incidence and HIV prevalence. The diagnosis of such lesions, which include tuberculoma and tuberculous abscesses, is often presumptive and based on radiological features, supportive evidence of TB elsewhere and response to TB treatment. However, the treatment response is unpredictable, with lesions frequently enlarging paradoxically or persisting for many years despite appropriate TB treatment and corticosteroid therapy. Most international guidelines recommend a 9-12 month course of TB treatment for central nervous system TB when the infecting Mycobacterium tuberculosis ( M.tb) strain is sensitive to first-line drugs. However, there is variation in opinion and practice with respect to the duration of TB treatment in patients with tuberculomas or tuberculous abscesses. A major reason for this is the lack of prospective clinical trial evidence. Some experts suggest continuing treatment until radiological resolution of enhancing lesions has been achieved, but this may unnecessarily expose patients to prolonged periods of potentially toxic drugs. It is currently unknown whether persistent radiological enhancement of intracranial tuberculomas after 9-12 months of treatment represents active disease, inflammatory response in a sterilized lesion or merely revascularization. The consequences of stopping TB treatment prior to resolution of lesional enhancement have rarely been explored. These important issues were discussed at the 3 rd International Tuberculous Meningitis Consortium meeting. Most clinicians were of the opinion that continued enhancement does not necessarily represent treatment failure and that prolonged TB therapy was not warranted in patients presumably infected with M.tb strains susceptible to first-line drugs. In this manuscript we highlight current medical treatment practices, benefits and disadvantages of different TB treatment durations and the need for evidence-based guidelines regarding the treatment duration of patients with intracranial tuberculous mass lesions.

Management of intracranial tuberculous mass lesions: how long should we treat for?

Tuberculous intracranial mass lesions are common in settings with high tuberculosis (TB) incidence and HIV prevalence. The diagnosis of such lesions, which include tuberculoma and tuberculous abscesses, is often presumptive and based on radiological features, supportive evidence of TB elsewhere and response to TB treatment. However, the treatment response is unpredictable, with lesions frequently enlarging paradoxically or persisting for many years despite appropriate TB treatment and corticosteroid therapy. Most international guidelines recommend a 9-12 month course of TB treatment for central nervous system TB when the infecting Mycobacterium tuberculosis ( M.tb) strain is sensitive to first-line drugs. However, there is variation in opinion and practice with respect to the duration of TB treatment in patients with tuberculomas or tuberculous abscesses. A major reason for this is the lack of prospective clinical trial evidence. Some experts suggest continuing treatment until radiological resolution of enhancing lesions has been achieved, but this may unnecessarily expose patients to prolonged periods of potentially toxic drugs. It is currently unknown whether persistent radiological enhancement of intracranial tuberculomas after 9-12 months of treatment represents active disease, inflammatory response in a sterilized lesion or merely revascularization. The consequences of stopping TB treatment prior to resolution of lesional enhancement have rarely been explored. These important issues were discussed at the 3 rd International Tuberculous Meningitis Consortium meeting. Most clinicians were of the opinion that continued enhancement does not necessarily represent treatment failure and that prolonged TB therapy was not warranted in patients presumably infected with M.tb strains susceptible to first-line drugs. In this manuscript we highlight current medical treatment practices, benefits and disadvantages of different TB treatment durations and the need for evidence-based guidelines regarding the treatment duration of patients with intracranial tuberculous mass lesions.

Evaluation of intracranial tuberculomas using diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS) and susceptibility weighted imaging (SWI)

OBJECTIVE:

The present study was aimed to evaluate patients of suspected intracranial tuberculomas with diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS) and susceptibility-weighted imaging (SWI).

METHODS:

The present study evaluated 116 patients known or suspected of having central nervous system tuberculosis with advanced MRI techniques comprising of DWI, MRS and SWI in addition to the conventional MRI.

RESULTS:

Apparent diffusion coefficient value of tuberculomas was not significantly different (p > 0.05) from apparent diffusion coefficient value of metastatic lesions and high-grade gliomas. MRS revealed that NAA/Cr and NAA/Cho ratios of tuberculomas were not significantly different (p > 0.05) from that of malignant brain lesions. However, Cho/Cr ratio of tuberculomas (1.36 ± 0.41) was significantly lower from that of malignant brain lesions (2.63 ± 0.99). SWI revealed a complete and regular hypointense peripheral ring in 42 cases of tuberculomas (58%) and in none of the malignant brain lesions.

CONCLUSION:

DWI offers no clear advantage in differentiating tuberculomas from metastasis and gliomas. Tuberculomas may be differentiated from metastases and gliomas by their unique metabolite pattern on MRS. Presence of a complete and regular peripheral hypointense ring in SWI favors the diagnosis of tuberculomas.

ADVANCES IN KNOWLEDGE:

The results from the present study suggest promising role of SWI in the discrimination of tuberculomas from metastatic brain lesions and gliomas with the presence of a complete and regular peripheral hypointense ring favoring the diagnosis of tuberculomas.

Cystic Meningiomas: Correlation between Radiologic and Histopathologic Features

Background

Tumors with cysts often correlate with gliomas, metastatic tumors, or hemangioblastomas, which require differentiation.

Methods

Thirty-eight cases of cyst associated-meningioma based on preoperative radiologic studies and histologic confirmations were reviewed from November 1998 to July 2017.

Results

A total of 395 cases of meningioma were observed in the 20 years, and surgical treatment of intracranial meningioma was performed in 120 cases. Thirty-eight (9.6%) cases of cyst associated meningiomas were analyzed. Nauta type I was the most common type of cyst (39.5%) and the most frequent histopathological subtype was meningothelial type (36.8%).

Conclusion

Statistically there were no significant associations between meningioma histopathological type and associated cysts; however, the rate of World Health Organization grade II was higher in cyst associated meningiomas than in unrelated meningiomas. This correlation was weak, in accordance with the meningioma grade.

MR spectroscopy of intracranial tuberculomas: A singlet peak at 3.8 ppm as potential marker to differentiate them from malignant tumors

PURPOSE

The diagnosis of intracranial tuberculomas is often challenging. Our purpose is to describe the most common metabolic patterns of tuberculomas by MR spectroscopy (MRS) with emphasis on potential specific markers.

METHODS

Single-voxel MRS short echo time was performed in 13 cases of tuberculomas proven by histology and/or response to anti-mycobacterial therapy. For comparison MRS was also performed in 19 biopsy-proven malignant tumors (13 high-grade gliomas and six metastasis). Presence of metabolic peaks was assessed visually and categorical variables between groups were compared using chi-square. Metabolite ratios were compared using Mann-Whitney test and diagnostic accuracy of the metabolite ratios was compared using receiver-operating characteristic (ROC) curves analysis.

RESULTS

Spectroscopic peaks representing lipids and glutamate/glutamine (Glx) as well as a peak at ∼3.8 ppm were well defined in 77% (10/13), 77% (10/13) and 69% (nine of 13) of tuberculomas, respectively. Lipid and Glx peaks were also present in most of the malignant lesions, 79% (15/19) and 74% (14/19) respectively. However, a peak at ∼3.8 ppm was present in only 10% (two of 19) of the tumor cases (p < 0.001). Higher Cho/Cr and mI/Cr ratios helped discriminate malignant lesions with an area under the ROC curve of 0.86 (SE: 0.078, p < 0.002, CI: 0.7-1) and 0.8 (SE: 0.1, p < 0.009, CI: 0.6-1), respectively. Threshold values between 1.7-1.9 for Cho/Cr and 0.8-0.9 for mI/Cr provided high specificity (91% for both metabolites) and adequate sensitivity (75% and 80%, respectively) for discrimination of malignant lesions.

CONCLUSION

A singlet peak at ∼3.8 ppm is present in the majority of tuberculomas and absent in most malignant tumors, potentially a marker to differentiate these lesions. The assignment of the peak is difficult from our analysis; however, guanidinoacetate (Gua) is a possibility. Higher Cho/Cr and mI/Cr ratios should favor malignant lesions over tuberculomas. The presence of lipids and Glx is non-specific.

Magnetic resonance features of pyogenic brain abscesses and differential diagnosis using morphological and functional imaging studies: a pictorial essay

The aim of this paper is to illustrate the potential of magnetic resonance imaging (MRI) in diagnosis, differential diagnosis, treatment planning and evaluation of therapy effectiveness of pyogenic brain abscesses, through the use of morphological (or conventional) and functional (or advanced) sequences. Conventional MRI study is useful for the identification of lesions, to determine the location and morphology and allows a correct hypothesis of nature in the most typical cases. However, the differential diagnosis from other brain lesions, such as non-pyogenic abscesses or necrotic tumors (high-grade gliomas and metastases) is often only possible through the use of functional sequences, as the measurement of diffusion with apparent diffusion coefficient (DWI-ADC), proton magnetic resonance spectroscopy ((1)H-MRS) and perfusion weighted imaging (PWI), which complement the morphological sequences and provide essential information on structural, metabolic and hemodynamic characteristics allowing greater neuroradiological confidence. Modern diagnostic MRI of pyogenic brain abscesses cannot be separated from knowledge, integration and proper use of the morphological and functional sequences.

Neuroparacoccidioidomycosis (NPCM): magnetic resonance imaging (MRI) findings

OBJECTIVE

To describe the magnetic resonance imaging (MRI) patterns of the central nervous system (CNS) involvement by neuroparacoccidioidomycosis (NPCM).

METHODS

Between January 1999 and March 2011, a review of MRI data analysis from 8 cases of NPCM was performed. The following MRI characteristics were examined by an experienced neuroradiologist: topography of lesions, aspects on T1- and T2-weighted images (WI), contrast enhancement, diffusion and spectroscopy.

RESULTS

All patients had evidence of paracoccidioidomycosis infection outside the nervous system. Regarding CNS involvement, five patients had only supratentorial lesions; three had infra- and supratentorial ones. Meningeal extension occurred in three patients. The lesions were predominantly hyperintense on T1WI. At T2WI, a hypointense component was present in five cases as well as a perilesional abnormal white matter. A ring-enhancement pattern was seen in five cases. Spectroscopy was performed in three patients and showed an increased lipid peak in all of them. In one case, there was also an increased choline peak.

CONCLUSION

NPCM is rare, and MRI may help its differentiation from other inflammatory lesions. However, the presence of active infection outside CNS and some imaging characteristics should point to this diagnosis.

Imaging of cerebellopontine angle lesions: an update. Part 1: enhancing extra-axial lesions

Computed tomography (CT) and magnetic resonance (MR) imaging reliably demonstrate typical features of vestibular schwannomas or meningiomas in the vast majority of mass lesions in the cerebellopontine angle (CPA). However, a large variety of unusual lesions can also be encountered in the CPA. Covering the entire spectrum of lesions potentially found in the CPA, these articles explain the pertinent neuroimaging features that radiologists need to know to make clinically relevant diagnoses in these cases, including data from diffusion and perfusion-weighted imaging or MR spectroscopy, when available. A diagnostic algorithm based on the lesion's site of origin, shape and margins, density, signal intensity and contrast material uptake is also proposed. Part 1 describes the different enhancing extra-axial CPA masses primarily arising from the cerebellopontine cistern and its contents, including vestibular and non-vestibular schwannomas, meningioma, metastasis, aneurysm, tuberculosis and other miscellaneous meningeal lesions.

Serial diffusion-weighted MRI correlates with clinical course and treatment response in children with intracranial pus collections

BACKGROUND

Accurate assessment of treatment response in children with intracranial pus collections is vital to guide appropriate therapy and reduce morbidity and mortality.

OBJECTIVE

To correlate serial MR-measurable changes in diffusion-weighted imaging (DWI) with clinical response to treatment.

MATERIALS AND METHODS

We retrospectively reviewed clinical notes, conventional MR sequences and DWI in eight children with intracranial pus collections. Trace DWI signal intensity and apparent diffusion coefficient (ADC) values were compared at three time points: at initial diagnosis (eight children, 13 collections), at follow-up during continued clinical infection (three children, sp collections), and at follow-up when clinical infection had resolved (seven children, 12 collections).

RESULTS

At initial diagnosis all patients were septic and collections showed restricted diffusion (mean ADC 0.61+/-0.15 x 10(-3) mm(2)/s). Patients with persistent clinical sepsis at follow-up DWI had collections with persistent low ADC values (0.66+/-0.21 x 10(-3) mm(2)/s), significantly (P<0.001) below normal cortical gray matter values. Successful resolution of the infection was associated with a significant rise in ADC values (1.57+/-0.57 x 10(-3) mm(2)/s, P<0.01) compared both to patients with signs of continued sepsis and to normal gray matter values.

CONCLUSION

Persistent restricted diffusion in pus collections correlates with continued sepsis. Treatment response is associated with clinical resolution of sepsis and ADC value elevation significantly above normal gray matter values.

Diffusion-weighted and conventional magnetic resonance imaging in cerebral cryptococcoma

A case of cryptococcoma involving the right cerebral hemisphere is reported. The diffusion-weighted image shows hypointensity in the central cavity of the cryptococcoma, while apparent diffusion coefficient maps show hyperintensity. The imaging features of an intracerebral cryptococcoma mimic that of a central necrotic brain tumor, rather than a pyogenic brain abscess.

Granulomatous diseases of the central nervous system

Infectious diseases of the central nervous system (CNS), particularly those accompanied by the formation of granulomas, are a constant diagnostic challenge in some specific regions of the world, above all in developing countries. The pattern of image seen on CT or MR scan is the result of the inter-relations between the individual characteristics of the infectious agent and the capacity of each host to mount an appropriate inflammatory response to that specific type of aggression, inside one particular compartment of the CNS. Taking these parameters into account we will discuss the several patterns of image found in parasitic, bacterial, and fungal granulomatous infections.