Magnetization transfer imaging diagnosis of intracranial tuberculomas

Magnetic resonance imaging findings in central nervous system tuberculosis: A pictorial review

Central nervous system (CNS) tuberculosis is a post-primary form of tuberculosis. It has high mortality and morbidity rates despite early diagnosis and treatment. CNS tuberculosis can manifest as subacute/chronic meningitis, parenchymal tuberculous lesions, and spinal tuberculosis. Hematogenous spread of tuberculous bacilli to the brain results in the development of so called "rich foci" on the pial surface, ependyma, and grey-white matter junction. Rupture of these "rich foci" into the subarachnoid space triggers an intense granulomatous inflammatory reaction. Tuberculous meningitis can manifest as leptomeningitis or pachymeningitis. Intracranial parenchymal tuberculous lesions may present as tuberculoma, tuberculous abscess, cerebritis, rhombencephalitis, and encephalopathy, with atypical presentations not uncommon. Complications of CNS tuberculosis encompass hydrocephalus, syrinx formation, vasculitis, infarcts, neuritis, and enduring neurological deficits. Post-contrast 3D fluid-attenuated inversion recovery (FLAIR) and post-contrast T1 spin-echo sequences excel in detecting tuberculous meningitis compared to other conventional magnetic resonance imaging (MRI) sequences. In proton magnetic resonance spectroscopy (PMRS), the presence of a lipid peak at 1.3 ppm is indicative of tuberculous lesions. Magnetization transfer (MT) imaging enhances the detection of tuberculous lesions, as the magnetization transfer ratio (MTR) of tuberculous pathologies, owing to their high lipid content, is lower than that in bacterial or fungal pathologies and higher than that in viral pathologies. This review article delves into the various typical and atypical imaging presentations of CNS tuberculosis in MRI, along with recent advances in imaging techniques.

Follow-up study of neuropsychological scores of infant patients with cobalamin C defects and influencing factors of cerebral magnetic resonance imaging characteristics

Purpose

The purpose of this study was to investigate whether baseline cerebral magnetic resonance imaging (MRI) characteristics could predict therapeutic responsiveness in patients with cobalamin C (cblC) defects.

Materials and methods

The cerebral MRI results of 40 patients with cblC defects were evaluated by a neuroradiologist. Neuropsychological scores and imaging data were collected. Neuropsychological tests were performed before and after standardized treatment.

Results

Thirty-eight patients initially underwent neuropsychological testing [developmental quotient (DQ)]. CblC defects with cerebellar atrophy, corpus callosum thinning and ventricular dilation had significantly lower DQs than those without (P < 0.05). Through a multivariate linear stepwise regression equation after univariate analysis, ventricular dilation was the most valuable predictor of lower DQs. Thirty-six patients (94.7%) underwent follow-up neuropsychological testing. The pre- and post-treatment DQ values were not significantly different (Z = -1.611, P = 0.107). The post-treatment DQ classification (normal, moderately low, or extremely low) showed nearly no change compared to the pretreatment DQ classification (k = 0.790, P < 0.001).

Conclusion

Ventricular dilation, cerebral atrophy and corpus callosum thinning are the main MRI abnormalities of cblC defects, and these manifestations are significantly correlated with delayed development in children. MRI findings can be considered an important tool for determining the severity of cblC defects.

Brain MRI features of methylmalonic acidemia in children: the relationship between neuropsychological scores and MRI findings

Methylmalonic acidemia (MMA) is a severe, heterogeneous disorder of methylmalonate and cobalamin (cbl; vitamin B12) metabolism with a poor prognosis that can cause brain damage. Identifying the magnetic resonance imaging (MRI) findings of MMA might help to make accurate diagnoses earlier in the disease course and exploring the relationship between neuropsychological scores and MRI findings, when therapy is more effective and to improve therapeutic efficacy. Cerebral MRI studies from 37 children with MMA were evaluated by a neuroradiologist. Clinical and imaging data were collected from each patient. All tests were performed during routine investigations and in accordance with the ethical principles of the Declaration of Helsinki. Informed consent was obtained from the guardians of all patients for inclusion in the study. The most common and significant findings were periventricular white matter changes (78.4%), ventricular dilation (29.7%) and cerebral atrophy (40.5%). According to the developmental quotient, the 37 patients were divided into the normal intelligence subgroup (NI, developmental quotient ≥ 85) and the low intelligence subgroup (LI, developmental quotient < 85). The incidence of corpus callosal thinning, cortical atrophy, subcortical white matter changes, and ventricular dilation (grades 0-3) was significantly higher in the LI subgroup than in the NI subgroup (P < 0.05). The incidence of no-mild and moderate-severe ventricular dilation was significantly higher in the LI subgroup than in the NI subgroup (P < 0.05). Ventricular dilatation, cerebral atrophy, white matter changes, and corpus callosal thinning are the main MRI abnormalities in MMA patients, and these manifestations are significantly correlated with delayed development in children.

Amide Proton Transfer-Weighted (APTw) Imaging of Intracranial Infection in Children: Initial Experience and Comparison with Gadolinium-Enhanced T1-Weighted Imaging

Purpose

To evaluate the performance of amide proton transfer-weighted (APTw) imaging against the reference standard of gadolinium-enhanced T1-weighted imaging (Gd-T1w) in children with intracranial infection.

Materials and Methods

Twenty-eight pediatric patients (15 males and 13 females; age range 1-163 months) with intracranial infection were recruited in this study. 2D APTw imaging and conventional MR sequences were conducted using a 3 T MRI scanner. Kappa (κ) statistics and the McNemar test were performed to determine whether the hyperintensity on APTw was related to the enhancement on Gd-T1w. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of APTw imaging to predict lesion enhancement were calculated.

Result

In twelve patients with brain abscesses, the enhancing rim of the abscesses on the Gd-T1w images was consistently hyperintense on the APTw images. In eight patients with viral encephalitis, three showed slight spotted gadolinium enhancement, while the APTw image also showed a slight spotted high signal. Five of these patients showed no enhancement on Gd-T1w and isointensity on the APTw image. In eleven patients with meningitis, increased APTw signal intensities were clearly visible in gadolinium-enhancing meninges. Sixty infectious lesions (71%) showed enhancement on Gd-T1w images. The sensitivity and specificity of APTw were 93.3% (56/60) and 91.7% (22/24). APTw demonstrated excellent agreement (κ = 0.83) with Gd-T1w, with no significant difference (P = 0.69) in detection of infectious lesions.

Conclusions

These initial data show that APTw MRI is a noninvasive technique for the detection and characterization of intracranial infectious lesions. APTw MRI enabled similar detection of infectious lesions to Gd-T1w and may provide an injection-free means of evaluation of intracranial infection.

CT Perfusion Dynamics of Intracranial Tuberculomas

AIMS

To study perfusion characteristics of intracranial tuberculomas and analyze changes with anti tubercular treatment.

MATERIALS AND METHODS

Nineteen patients of histologically proven intracranial tuberculomas were included in the study of which 9 were not on antitubercular treatment and ten were on antitubercular treatment (6 patients on treatment for less than 2 months and 4 were more than 6 months). All patients underwent CT perfusion (CTP) and CTP parameters like rCBV and rCBF were obtained from entire lesion, center and capsule of lesions and compared.

RESULTS

CTP parameters like rCBF and rCBV were significantly low in all the three ROIs in the group not on treatment compared to that of on treatment ; rCBF and rCBV of entire lesion (p=0.018 and p=0.005 respectively), capsule (p=0.045 and p=0.010 respectively) and center of the lesion (p=0.020 and p=0.009) respectively). Tuberculomas on antitubercular treatment of more than six months showed reduced rCBF and rCBV in entire lesion (p=0.01 & p=0.01 respectively), capsule (p=0.04 & p=0.03 respectively) and center (p=0.08 & p=0.05 respectively) compared to those on treatment for less than two months. Similarly tuberculomas on treatment for six months did not show significant difference in rCBF and rCBV compared to tuberculomas who were not on treatment. Tuberculomas on treatment for less than two months showed statistically increased rCBF and rCBV in entire lesion (p=0.01 & p=0.04 respectively), capsule (p=0.03 & p=0.01 respectively) and center (p= 0.03 &=0.01) compared to those not on treatment.

CONCLUSION

Intracranial tuberculomas not on treatment and those on treatment for around six months show low perfusion and tuberculomas on treatment for less than two months show high perfusion. These findings suggest that serial perfusion profiles of tuberculomas on treatment could possibly be seen as surrogate markers of response to treatment.

Tuberculosis

Tuberculosis remains a serious health problem worldwide, particularly affecting the poorest in both high-income and developing countries. It was declared a global emergency by the World Health Organization in 1993. Central nervous system (CNS) tuberculosis is caused by mycobacteria belonging to the Mycobacterium tuberculosis complex, and is acquired through inhalation of aerosolized droplet nuclei. Meningitis represents the most frequent and severe form of CNS tuberculosis. Parenchymal CNS involvement can occur in the form of tuberculoma or, more rarely, abscess. Also, damage of the spinal cord, roots, and spine can occur in the form of spinal meningitis, radiculomyelitis, spondylitis, or spinal cord infarction. Diagnosis remains a challenge due to the slow growth of the organisms and the low yield of cerebrospinal fluid cultures, as well as the frequent absence of evidence of infection elsewhere. This results in frequent empirical therapy, based on a combination of four drugs (isoniazid, rifampicin, pyrazinamide and ethambutol) for 2 months, followed by 10 additional months with two drugs (isoniazid and rifampicin) to a total duration of 12 months. Shorter regimens have also been successful, but there have been few controlled trials in patients with extrapulmonary disease. Corticoid therapy seems to be associated with a reduced risk of death, and is usually indicated. Evidence of multidrug resistance requires variable combinations of first- and second-line drugs; fortunately, resistance does not seem to represent a serious threat for CNS tuberculosis at present, but still requires the utmost vigilance.

Magnetization transfer ratio in neuro-Beh�et disease

The aim of this study was to determine the contribution of magnetization transfer ratios (MTRs) in detecting disease in normal-appearing brain regions of patients with neuro-Behçet (NB) disease. Thirty-two patients with NB disease were assessed. Fifteen healthy volunteers were examined as the control group. Magnetic resonance (MR) imaging of the head was performed without and with magnetization transfer (MT) contrast. Signal intensity measurements were obtained from ten anatomical regions (centrum semiovale, corona radiata, internal capsule, forceps major, forceps minor, thalamus, substantia nigra pars compacta, substantia nigra pars grisea, inferior pons and middle cerebellar peduncle) in both groups. Also measured in the NB group were parenchymal lesions in the brain stem, basal ganglia and cerebral deep white matter. MTR was calculated for each measurement. Statistical analysis was performed with Mann-Whitney U and independent t-tests with computer-based SPSS 11.0 for Windows software. A P value below 0.05 was considered statistically significant. The mean MTR of the parenchymal lesions in the NB group was lower than the mean MTR of the normal-appearing parenchyma in both the NB patients and the normal group. For the normal-appearing parenchyma the mean MTR in the NB group was higher than that for the controls for all regions except the corona radiata; however, the difference was statistically significant only for the thalamus. The MRI-visible parenchymal involvement of Behçet's disease causes a decrease in MTR. For the normal-appearing brain, although lacking statistical significance for the most regions studied, the tendency for higher MTR in NB patients compared with controls may offer an insight into the pathophysiology of Behçet's disease.

Magnetization transfer, HASTE, and FLAIR imaging

Continuous technologic developments and research have increased the clinical applications of MT, HASTE, and FLAIR imaging in neuroradiology. HASTE has become the MR imaging sequence of choice for fetal neuroimaging. Other promising uses, such as for diffusion-weighted imaging, have not been fully exploited. FLAIR has been firmly established as one of the cornerstones of brain imaging; however, post-contrast FLAIR images have not offered a clear advantage over standard T1-weighted images as suggested by early studies. FLAIR imaging with echoplanar acquisition is not considered advantageous, because the decreased imaging times are obtained at the expense of lower sensitivity. For a number of applications, diffusion-weighted imaging has surpassed FLAIR. Nevertheless, FLAIR images may be more sensitive for the detection of acute brain infarction. Recently described methods for the elimination of CSF flow artifacts may lead to improved quality and reliability of FLAIR images for subarachnoid space disease. MT preparation is now routinely incorporated in time-of-flight MR angiography and gradient-echo T2*-weighted spine imaging sequences and provides increased sensitivity for postcontrast MR imaging. These applications may not be advantageous in all clinical settings. MTR analysis offers valuable information for an increasing number of pathologic processes but has not yet gained wide clinical acceptance owing to sophisticated postprocessing and significant intercenter variations. Different modifications of these techniques are being evaluated, and further developments are expected.

Perfusion magnetic resonance imaging in intracerebral parenchymal tuberculosis: preliminary findings

OBJECTIVES

To study the vascular perfusion patterns of focal intracerebral tubercular lesions using echoplanar magnetic resonance (MR) imaging-derived relative cerebral blood volume (rCBV) maps.

METHODS

Seventeen focal tubercular lesions were evaluated with conventional and perfusion-weighted MR imaging on a 1.5-T MR system. The rCBVs of the center, peripheral wall, and perilesional white matter were calculated from the perfusion MR-derived data. Perfusion MR imaging findings as depicted on the rCBV maps were qualitatively compared with those of conventional MR findings.

RESULTS

Eleven of the 17 lesions demonstrated vascularity greater than that of the contralateral white matter on rCBV maps. The mean of the measured rCBV values of the peripheral wall and center of the lesions was 2.5 +/- 1.42 and 0.33 +/- 0.3 (mean +/- SD), respectively. Most of the hypervascular lesions (8) revealed a concentric peripheral wall having alternating hypointense and hyperintense signal intensity rims surrounding a variable intensity center on T2-weighted images. All the lesions having a nodular enhancing pattern (4) were hypervascular.

CONCLUSIONS

Focal cerebral tubercular lesions can have variable vascularity as shown on perfusion MR-derived rCBV maps. It may be difficult to differentiate hypervascular lesions from cerebral tumors in some patients based on perfusion MR imaging alone.

Functional analysis of human parotid gland in vivo using the (1)H MRS MT effect

Magnetization transfer (MT) was measured in the parotid gland in vivo by (1)H MR spectroscopy in 10 adult volunteers. A comparison was made of stimulated (excess saliva) and resting parotid gland (SPG and RPG, respectively). Following irradiation at an MT pulse of 150 Hz downfield from the water proton signal, signal reductions in SPG and RPG were 83.8 +/- 4.7 and 91.4 +/- 5.7%, respectively. The larger reduction for SPG indicates that an increase in the amount of water in gland cells for the production of more parotid saliva may lead to greater affinity between the protons adjacent to macromolecules and free water which contributes to the MT effect. Activity in the parotid gland correlates with the effect. This method is useful for diagnosing disorders of parotid gland secretion.