An Algorithmic Approach to MR Imaging of Hypomyelinating Leukodystrophies.

Hypomyelinating leukodystrophies (HLDs) are a heterogeneous group of white matter diseases characterized by permanent deficiency of myelin deposition in brain. MRI is instrumental in the diagnosis and recommending genetic analysis, and is especially useful as many patients have a considerable clinical overlap, with the primary presenting complains being global developmental delay with psychomotor regression. Hypomyelination is defined as deficient myelination on two successive MR scans, taken at least 6 months apart, one of which should have been obtained after 1 year of age. Due to subtle differences in MRI features, the need for a systematic imaging approach to diagnose and classify hypomyelinating disorders is reiterated. The presented article provides an explicit review of imaging features of a myriad of primary and secondary HLDs, using state of the art genetically proven MR cases. A systematic pattern-based approach using MR features and specific clinical clues is illustrated for a quick yet optimal diagnosis of common as well as rare hypomyelinating disorders. The major MR features helping to narrow the differential diagnosis include extent of involvement like diffuse or patchy hypomyelination with selective involvement or sparing of certain white matter structures like optic radiations, median lemniscus, posterior limb of internal capsule and periventricular white matter; cerebellar atrophy; brainstem, corpus callosal or basal ganglia involvement; T2 hypointense signal of the thalami; and presence of calcifications. The authors also discuss the genetic and pathophysiologic basis of HLDs and recent methods to quantify myelin in vivo using advanced neuroradiology tools. The proposed algorithmic approach provides an improved understanding of these rare yet important disorders, enhancing diagnostic precision and improving patient outcomes. EVIDENCE LEVEL: 4 TECHNICAL EFFICACY: Stage 5.

"Visualization matters" - stereoscopic visualization of 3D graphic neuroanatomic models through AnaVu enhances basic recall and radiologic anatomy learning when compared with monoscopy.

BACKGROUND: The authors had previously developed AnaVu, a low-resource 3D visualization tool for stereoscopic/monoscopic projection of 3D models generated from pre-segmented MRI neuroimaging data. However, its utility in neuroanatomical education compared to conventional methods (specifically whether the stereoscopic or monoscopic mode is more effective) is still unclear. METHODS: A three-limb randomized controlled trial was designed. A sample (n = 152) from the 2022 cohort of MBBS students at Government Medical College, Thiruvananthapuram (GMCT), was randomly selected from those who gave informed consent. After a one-hour introductory lecture on brainstem anatomy and a dissection session, students were randomized to three groups (S - Stereo; M - Mono and C - Control). S was given a 20-min demonstration on the brainstem lesson module in AnaVu in stereoscopic mode. M was given the same demonstration, but in monoscopic mode. The C group was taught using white-board drawn diagrams. Pre-intervention and post-intervention tests for four domains (basic recall, analytical, radiological anatomy and diagram-based questions) were conducted before and after the intervention. Cognitive loads were measured using a pre-validated tool. The groups were then swapped -S→ M, M →S and C→S, and they were asked to compare the modes. RESULTS: For basic recall questions, there was a statistically significant increase in the pre/post-intervention score difference of the S group when compared to the M group [p = 0.03; post hoc analysis, Bonferroni corrections applied] and the C group [p = 0.001; ANOVA test; post hoc analysis, Bonferroni corrections applied]. For radiological anatomy questions, the difference was significantly higher for S compared to C [p < 0.001; ANOVA test; post hoc analysis, Bonferroni corrections applied]. Cognitive load scores showed increased mean germane load for S (33.28 ± 5.35) and M (32.80 ± 7.91) compared with C (28.18 ± 8.17). Subjective feedbacks showed general advantage for S and M compared to C. Out of the S and M swap cohorts, 79/102 preferred S, 13/102 preferred M, and 6/102 preferred both. CONCLUSIONS: AnaVu tool seems to be effective for learning neuroanatomy. The specific advantage seen when taught with stereoscopy in basic recall and radiological anatomy learning shows the importance of how visualization mode influences neuroanatomy learning. Since both S and M are preferred in subjective feedbacks, these results have implications in choosing methods (stereoscopic - needs 3D projectors; monoscopic - needs web based or hand-held devices) to scale AnaVu for anatomy teaching in medical colleges in India. Since stereoscopic projection is technically novel and cost considerations are slightly higher compared to monoscopic projection, the specific advantages and disadvantages of each are relevant in the Indian medical education scenario.

Quantitative Susceptibility Mapping: Technical Considerations and Clinical Applications in Neuroimaging.

Quantitative susceptibility mapping (QSM) is a novel magnetic resonance imaging (MRI) technique for quantifying the spatial distribution of magnetic susceptibility within an object or tissue. Recently, QSM has been widely used to study various dominant magnetic susceptibility sources in the brain, including iron and calcium. In addition, the method enables mapping of the cerebral metabolic rate of oxygen, which could act as a new metabolic biomarker for diseases that involve disruption of the brain's oxygen supply. Thus, the clinical applications of QSM are wide-reaching and hold great promise as imaging biomarkers for studying several neurological diseases. This review aims to summarize the physical concepts and potential clinical applications of QSM in neuroimaging. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 2.

Quantitative susceptibility-weighted imaging in predicting disease activity in multiple sclerosis.

PURPOSE: Repeated use of Gadolinium (Gd) contrast for multiple sclerosis (MS) imaging leads to Gd deposition in brain. We aimed to study the utility of phase values by susceptibility weighted imaging (SWI) to assess the iron content in MS lesions to differentiate active and inactive lesions. METHODS: MS persons who underwent MRI were grouped into group 1 with active lesions and group 2 with inactive lesions based on the presence or absence of contrast enhancing lesions. Phase values of lesions (PL) and contralateral normal white matter (PN) were calculated using the SPIN software by drawing ROI. Subtracted phase values (PS = PL - PN) and iron content (PS/3) of the lesions were calculated in both groups. RESULTS: We analyzed 69 enhancing lesions from 22 patients (group 1) and 84 non-enhancing lesions from 29 patients (group 2). Mean-subtracted phase values and iron content corrected for voxels in ROI were significantly lower in enhancing lesions compared to non-enhancing lesions (p < 0.001). A cut-off value 2.8 µg/g for iron content showed area under the curve of 0.909 with good sensitivity. CONCLUSION: Quantification of iron content using SWI phase values holds promise as a biomarker to differentiate active from inactive lesions of MS.

Arterial spin labeling hyperperfusion in seizures associated with non-ketotic hyperglycaemia: is it merely a post-ictal phenomenon?

A 53-year-old chronic uncontrolled diabetic patient presented with one episode of generalized seizures followed by drowsiness and post-ictal confusion. MR imaging at admission revealed left temporal subcortical T2/FLAIR hypointensities with overlying cortical T2/FLAIR hyperintensities and increased perfusion on arterial spin labeling (ASL). Follow-up imaging at 4- and 8-week interval revealed persistent ASL hyperperfusion with significant resolution of conventional MR imaging findings. Delayed persistent ASL hyperperfusion suggests that hyperglycemia-induced increased blood-brain barrier permeability rather than a mere post-ictal phenomenon in non-ketotic hyperglycemia (NKH) and may result in long-term cognitive disturbances.

Identifying Resting-State Functional Connectivity Changes in the Motor Cortex Using fNIRS During Recovery from Stroke.

Resting-state functional imaging has been used to study the functional reorganization of the brain. The application of functional near-infrared spectroscopy (fNIRS) to assess resting-state functional connectivity (rsFC) has already been demonstrated in recent years. The present study aimed to identify the difference in rsFC patterns during the recovery from the upper-limb deficit due to stroke. Twenty patients with mild stroke having an onset of four to eight weeks were recruited from the stroke clinic of our institute and an equal number of healthy volunteers were included in the study after ethical committee approval. The fNIRS signals were recorded bilaterally over the premotor area and supplementary motor area and over the primary motor cortex. Pearson Correlation is the method used to compute rsFC for the healthy group and patient group. For the healthy group, both intra-hemispheric and inter-hemispheric connections were stronger. RSFC analysis demonstrated changes from the healthy pattern for the patient group with an upper-limb deficit. The left hemisphere affected group showed disrupted ipsilesional and an increased contra-lesional connectivity. The longitudinal data analysis of rsFC showed improvement in the connections in the ipsilesional hemisphere between the primary motor area, somatosensory area, and premotor areas. In the future, the rsFC changes during the recovery could be used to predict the extent of recovery from stroke motor deficits.

Risk factors of white matter hyperintensities in South Asian patients with transient ischemic attack and minor stroke.

PURPOSE: Aging and increased burden of cardiovascular risk factors are associated with severity of white matter hyperintensity (WMH). We assessed the burden and risk factor profile of WMHs in South Asian patients with transient ischemic attack (TIA) and minor stroke. METHODS: Patients with acute ischemic stroke with the National Institute of Health stroke scale (NIHSS) score ≤ 5 who underwent MRI were included. The severity of WMHs was assessed based on age-related white matter change (ARWMC) scale (0-30). A score of > 8 or more was considered moderate-severe involvement. Logistic regression analysis was performed to assess the association with risk factors. RESULTS: A total of 424 patients with a mean ± SD age of 57.4 ± 14.5 years [females, 108 (25.5%)] were analyzed. Fifty-four (12.7%) patients had moderate or severe WMHs (ARWMC score > 8). Age (OR 1.03, 95% CI 1.01-1.06; p = 0.004), hypertension (OR 2.3, 95% CI 1.1-5.1; p = 0.03) and smoking tobacco (OR 2.8, 95% CI 1.4-5.6; p = 0.003) were independently associated with ARWMC score > 8. The median (IQR) regional score in patients with ARWMC score > 8 was maximum in frontal areas 4 (4-6, p < 0.0001) and parietooccipital areas 4.5(4-6, p < 0.0001). The presence of microbleeds (OR 6.3, 95% CI 3.1-12.7; p < 0.0001) was independently associated with ARWMC score > 8. CONCLUSION: South Asian patients with TIA and minor stroke are relatively young, and few patients have moderate and severe WMHs. Hypertension and tobacco smoking increases the risk of WMH. Targeting modifiable risk factors may reduce the burden of WMHs and vascular dementia.

Haemosiderin cap sign in cervical intramedullary schwannoma mimicking ependymoma: how to differentiate?

A 37-year-old female presented with gradually progressive asymmetric ascending paraesthesia and weakness involving bilateral upper and lower limbs. The MRI spine images revealed expansile intramedullary, solid cystic, peripherally enhancing lesion with a haemosiderin cap along the lower margin. The lesion extended into the left C5 and C6 nerve root exit zones, along with thickening and enhancement of the nerve roots. She underwent excision of the lesion, which revealed intramedullary schwannoma on histopathological examination. Presence of the cap, an extension of the lesion into the nerve root exit zone, with associated thickening and enhancement of the dorsal nerve roots should alert the radiologist to consider the possibility of intramedullary schwannoma rather than ependymoma. Schwannoma showing compact Antoni A area with Schwannian whorls and nuclear palisades (A,B) and loose Antoni B area with haemosiderin pigment (C). The tumour exhibits diffuse positivity for S-100 protein (D) and negativity for GFAP (E). [Stain: A-C: Haematoxylin and Eosin; D,E: Immunoperoxidase. Magnification = Scale Bar, A-E: 100µm].

Utility of intracranial high-resolution vessel wall magnetic resonance imaging in differentiating intracranial vasculopathic diseases causing ischemic stroke.

PURPOSE: High-resolution vessel wall imaging (HRVWI) by MRI is a novel noninvasive imaging tool which provides direct information regarding vessel wall pathologies. The utility of HRVWI in differentiating various intracranial vasculopathies among ischemic stroke is still evolving. METHODS: Consecutive ischemic stroke/TIA patients within 2 weeks of symptom onset between January 2016 to December 2017, with symptomatic vessel stenosis of 50% or more/occlusion on baseline luminal imaging studies were recruited into the study. Stroke subtypes were classified as per TOAST classification initially on the basis of luminal imaging findings alone and subsequently after incorporation of HRVWI findings as well. RESULTS: Forty-nine subjects were recruited into the study. The median age of the population was 42 years (range 11 to 75) with 69% being males. Incorporation of HRVWI findings classified 38.8% subjects into intracranial atherosclerotic disease (ICAD), 32.6% as stroke of other determined aetiology (ODE) (inflammatory vasculopathy [IVas] being the major subgroup [81.2%]) and 28.6% into stroke of undetermined aetiology (UE). HRVWI enabled a diagnostic reclassification in an additional 47.3% among the baseline UE category as against luminal imaging findings alone. ICAD was likelier to have eccentric vessel wall thickening, eccentric vessel wall enhancement and T2 juxtaluminal hyperintensity with surrounding hypointensity (P < 0.001), while IVas were more likely to exhibit concentric vessel wall thickening with homogenous enhancement (P < 0.001). CONCLUSION: HRVWI is a useful noninvasive adjunctive tool in the diagnostic evaluation of intracranial vasculopathies, with maximum benefit in ICAD and IVas subtypes.

Bipartite craniopharyngeal canal with a lipoma and cephalocele: a previously unreported entity.

A 13-year-old male child was evaluated for headache and visual deterioration; he underwent routine MRI imaging which revealed a large craniopharyngeal canal, divided by an abnormal bony septum giving a bipartite appearance of the canal, with a lipoma and cephalocele on either side of the septum. The child had undergone a previous surgery for cleft palate repair at the age of 7. The child had normal pituitary function inspite of nonvisualization of pituitary gland in MRI. To best our knowledge, this is the first case with such a variation. We have also discussed the possible embryological hypothesis for this previously unreported entity. Knowledge about this rare variant might have surgical relevance in selected cases.

Construction of Indian human brain atlas.

CONTEXT: A brain magnetic resonanace imaging (MRI) atlas plays an important role in many neuroimage analysis tasks as it provides an atlas with a standard coordinate system which is needed for spatial normalization of a brain MRI. Ideally, this atlas should be as near to the average brain of the population being studied as possible. AIMS: The aim of this study is to construct and validate the Indian brain MRI atlas of young Indian population and the corresponding structure probability maps. SETTINGS AND DESIGN: This was a population-specific atlas generation and validation process. MATERIALS AND METHODS: 100 young healthy adults (M/F = 50/50), aged 21-30 years, were recruited for the study. Three different 1.5-T scanners were used for image acquisition. The atlas and structure maps were created using nonrigid groupwise registration and label-transfer techniques. COMPARISON AND VALIDATION: The generated atlas was compared against other atlases to study the population-specific trends. RESULTS: The atlas-based comparison indicated a signifi cant difference between the global size of Indian and Caucasian brains. This difference was noteworthy for all three global measures, namely, length, width, and height. Such a comparison with the Chinese and Korean brain templates indicate all 3 to be comparable in length but signifi cantly different (smaller) in terms of height and width. CONCLUSIONS: The findings confirm that there is significant difference in brain morphology between Indian, Chinese, and Caucasian populations.

High-resolution magnetic resonance vessel wall imaging in cerebrovascular diseases.

Most intracranial vascular disorders like atherosclerosis, vasculitis, and reversible cerebral vasoconstriction syndrome (RCVS) share similar lumenographic findings in traditional imaging modalities like computed tomography (CT), magnetic resonance imaging (MRI) and digital subtraction angiographic studies. Hence, there is a need for an advanced imaging modality like vessel wall imaging (VWI) to confirm the diagnosis so that appropriate clinical management could be done. Now, currently vessel wall imaging could be done in a high resolution manner with three dimensional (3D) imaging sequences. The aim of this article is to deal with the protocol as well as the current imaging applications of the high resolution VWI.

Arterial spin labeling hyperperfusion in Rasmussen's encephalitis: Is it due to focal brain inflammation or a postictal phenomenon?

BACKGROUND AND PURPOSE: The study evaluated the utility of arterial spin labeling (ASL) perfusion imaging in Rasmussen's encephalitis (RE). MATERIAL AND METHODS: The hospital electronic database was searched using the search words "encephalitis," "autoimmune encephalitis" and "Rasmussen's encephalitis" for the period of 1 Jan 2015 to 31 Jan 2017. Clinically diagnosed cases of RE for which epilepsy protocol magnetic resonance imaging (MRI) with perfusion imaging (ASL) performed on a 3T scanner were retrieved. The diagnosis of RE was based on Bien's criteria (Bien et al., 2005). We obtained patient's demographic details, clinical features, electrophysiological studies, and follow-up data from electronic hospital records. RESULTS: We included nine patients with RE of whom seven patients showed increased perfusion, and two patients decreased perfusion. Among these patients, MRI changes of gyral hyperintensity without volume loss corresponded to regional ASL hyperperfusion in six patients and ASL hypoperfusion in one patient. Two patients who showed ASL hypoperfusion had corresponding atrophy on MRI. Eight patients of RE had epilepsia partialis continua (EPC) or daily seizures, and one patient was seizure-free post-surgery. Five patients showed a concordance of ASL hyperperfusion with clinical ictal onset zone. Among the seven patients with ASL hyperperfusion, the finding was concordant (complete or partial) with the electroencephalogram (EEG) ictal onset zone in six patients and with interictal epileptiform discharges (IED) in seven patients. CONCLUSION: Increased perfusion in ASL of the involved brain parenchyma in RE is a common MRI finding and may be due to either active inflammation of the brain involved or a seizure-related finding.

Noncontrast Computed Tomography versus Computed Tomography Angiography Source Images for Predicting Final Infarct Size in Anterior Circulation Acute Ischemic Stroke: a Prospective Cohort Study.

BACKGROUND: There has been a recent debate regarding the superiority of computed tomography angiography source images (CTASIs) over noncontrast computed tomography (NCCT) to predict the final infarct size in acute ischemic stroke (AIS). We hypothesized that the parenchymal abnormality on CTASI in faster scanners would overestimate ischemic core. METHODS: This prospective study assessed the correlation of Alberta Stroke Program Early CT Score (ASPECTS) on NCCT, CTASI, and computed tomography perfusion (CTP) with final infarct size in patients within 8 hours of AIS. Follow-up with NCCT or diffusion-weighted magnetic resonance imaging (MRI) was performed at 24 hours. Correlations of NCCT and CTASI with final infarct size and with CTP parameters were assessed. Subgroup analysis was performed in patients who underwent intravenous thrombolysis or mechanical thrombectomy. Inter-rater reliability was tested using Spearman's rank correlation. A P value less than .05 was considered statistically significant. RESULTS: A total of 105 patients were included in the final analysis. NCCT had a stronger correlation with the final infarct size than did CTASI (Spearman's ρ = .85 versus .78, P = .13). We found an overestimation of the final infarct size by CTASI in 47.6% of the cases, whereas NCCT underestimated infarct size in 60% of the patients. NCCT correlated most strongly with CBV (ρ = .93), whereas CTASI correlated most strongly with CBF (ρ = .87). Subgroup analysis showed less correlation of CTASI with final infarct size in the group that received thrombolysis versus the group that did not (ρ = .70 versus .88, P = .01). CONCLUSION: In a 256-slice scanner, the CTASI parenchymal abnormality includes ischemic penumbra and thus overestimates final infarct size-this could result in inappropriate exclusion of patients from thrombolysis or thrombectomy.

CNS small vessel vasculitis: Distinct MRI features and histopathological correlation.

BACKGROUND: Central nervous system (CNS) vasculitis is an uncommon disease, which is a diagnostic and therapeutic challenge for physicians. Large and medium vessel vasculitis is relatively easy to diagnose by angiogram compared to small vessel vasculitis, where angiograms are often normal; imaging features described till date are sensitive but not specific. PURPOSE: Here, we describe distinct magnetic resonance (MR) imaging features of CNS small vessel vasculitis. MATERIALS AND METHODS: Five histologically proven small vessel vasculitis cases were retrospectively reviewed from medical records between January 2008 to July 2012. Angiogram (magnetic resonance angiography in all and digital subtraction angiography in three patients) were normal, ruling out associated large and medium vessel vasculitis. The MR imaging findings were analyzed for T2/fluid-attenuated inversion recovery (FLAIR) hyperintensities and blooming on susceptibility weighted imaging (SWI). RESULTS: Five patients (3 males) with a mean age of 34.2 years (range: 18 to 62 years) were included for analysis. Three patients with lymphocytic vasculitis had 43 discrete T2/FLAIR hyperintense lesions in brain parenchyma. All the brain lesions revealed central areas of SWI blooming in linear and/or lace-like pattern, surrounded by FLAIR hyperintensity. Corresponding T1-weighted contrast-enhanced images revealed subtle linear and lace-like enhancement. Coarse granular pattern of SWI blooming was seen in the patient with tuberculous vasculitis and no parenchymal abnormalities were seen in the patient with hypertrophic pachymeningitis. CONCLUSIONS: The linear SWI blooming along the course of small cerebral vessels and lace-like enhancement pattern in spin echo post-contrast T1-weighted sequences are suggestive MR imaging features for lymphocytic CNS small vessel vasculitis.

Microglioma in a child - a further case in support of the microglioma entity and distinction from histiocytic sarcoma.

Microglia are not generally known to cause brain tumors but one bona fide case of adult microglioma has been published [9]. This tumor was highly malignant. We now report on a second, juvenile case, which showed a less aggressive course. Microglioma is a primary central nervous system (CNS) neoplasm distinct from glioma and other known brain tumor entities, based on its strong immunoreactivity for the macrophage marker CD163, the microglia marker Iba1, and the complete absence of neural as well as lymphocyte antigens. Furthermore, we have analyzed the literature and identified a number of cases that qualify as primary parenchymal histiocytic sarcomas of the CNS, which lack microglial morphology. Considering the non-hematopoietic developmental origin of the vast majority of microglia and the distinct morphological as well as immunophenotypic similarity of their neoplastic counterparts, we suggest using the term microglioma. More cases will be required along with appropriately-collected tissue to establish the molecular genetic profile of this extremely rare entity.

Arcuate fasciculus laterality by diffusion tensor imaging correlates with language laterality by functional MRI in preadolescent children.

INTRODUCTION: Language lateralization is unique to humans. Functional MRI (fMRI) and diffusion tensor imaging (DTI) enable the study of language areas and white matter fibers involved in language, respectively. The objective of this study was to correlate arcuate fasciculus (AF) laterality by diffusion tensor imaging with that by fMRI in preadolescent children which has not yet been reported. METHODS: Ten children between 8 and 12 years were subjected to fMRI and DTI imaging using Siemens 1.5 T MRI. Two language fMRI paradigms--visual verb generation and word pair task--were used. Analysis was done using SPM8 software. In DTI, the fiber volume of the arcuate fasciculus (AFV) and fractional anisotropy (FA) was measured. The fMRI Laterality Index (fMRI-LI) and DTI Laterality Index (DTI-LI) were calculated and their correlation assessed using the Pearson Correlation Index. RESULTS: Of ten children, mean age 10.6 years, eight showed left lateralization while bilateral language lateralization was seen in two. AFV by DTI was more on the left side in seven of the eight children who had left lateralization by fMRI. DTI could not trace the AF in one child. Of the two with bilateral language lateralization on fMRI, one showed larger AFV on the right side while the other did not show any asymmetry. There was a significant correlation (p < 0.02) between fMRI-LI and DTI-LI. Group mean of AFV by DTI was higher on the left side (2659.89 ± 654.75 mm(3)) as compared to the right (1824.11 ± 582.81 mm(3)) (p < 0.01). CONCLUSION: Like fMRI, DTI also reveals language laterality in children with a high degree of correlation between the two imaging modalities.

Analyzing functional, structural, and anatomical correlation of hemispheric language lateralization in healthy subjects using functional MRI, diffusion tensor imaging, and voxel-based morphometry.

CONTEXT: To evaluate the efficacy of diffusion fiber tractography (DFT) and voxel-based morphometry (VBM) for lateralizing language in comparison with functional magnetic resonance imaging (fMRI) to noninvasively assess hemispheric language lateralization in normal healthy volunteers. AIMS: The aim of the present study is to evaluate the concordance of language lateralization obtained by diffusion tensor imaging (DTI) and VBM to fMRI, and thus to see whether there exists an anatomical correlate for language lateralization result obtained using fMRI. SETTINGS AND DESIGN: This is an advanced neuroimaging study conducted in normal healthy volunteers. SUBJECTS AND METHODS: Fifty-seven normal healthy subjects (39 males and 18 females; age range: 15-40 years) underwent language fMRI and 30 underwent direction DTI. fMRI language laterality index (LI), fiber tract asymmetry index (AI), and tract-based statistics of dorsal and ventral language pathways were calculated. The combined results were correlated with VBM-based volumetry of Heschl's gyrus (HG), planum temporale (PT), and insula for lateralization of language function. STATISTICAL ANALYSIS USED: A linear regression analysis was done to study the correlation between fMRI, DTI, and VBM measurements. RESULTS: A good agreement was found between language fMRI LI and fiber tract AI, more specifically for arcuate fasciculus (ArcF) and inferior longitudinal fasciculus (ILF). The study demonstrated significant correlations (P < 0.05) between blood-oxygen-level dependent (BOLD) fMRI activations, tract-based statistics, and PT and HG volumetry for determining language lateralization. CONCLUSIONS: A strong one-to-one correlation between fMRI, laterality index, DTI tractography measures, and VBM-based volumetry measures for determining language lateralization exists.

Diffusion tensor imaging and tractography of the human language pathways: moving into the clinical realm.

The functional correlates of anatomical derangements are of interest to the neurological clinician. Diffusion tensor tractography (DTT) is a relatively new tool in the arsenal of functional neuroimaging, by which to assess white matter tracts in the brain. While much import has been given to tracking corticospinal tracts in neurological disease, studying language pathway interconnections using DTT has largely remained in the research realm. Hardware and software advances have allowed this tool to ease into clinical practice, with several radiologists, neurologists, and neurosurgeons now familiar with its applications. DTT images, although visually appealing, are founded in mathematical equations and assumptions, and require a more than basic understanding of principles and limitations before they can be integrated into routine clinical practice. Cognitive pathways like that of language, that are normally hard to assess and especially more so when pathologically affected, have been at the receiving end of several opposing and often controversial hypotheses, and the past decade has seen the clarification, validation or rejection of several of these by the in vivo charting of functional connectivity using DTT. The focus of this review is to illustrate DTT of the language pathways with emphasis on practical considerations, clinical applications, and limitations.