Sangam Kanekar

MRI evaluation of asymmetry of nigrostriatal damage in the early stage of early-onset Parkinson's disease.

INTRODUCTION The motor symptoms and signs of early-onset idiopathic Parkinsons disease (PD) in Hoehn and Yahr (H&Y) stage-1 are generally unilateral. We hypothesized that there would be detectable differences in the quantitative MRI parameters in these PD patients between the hemispheres contralateral to the clinically symptomatic and non-symptomatic body side. METHODS We tested this hypothesis by comparing transverse relaxation rates and diffusion tensor imaging (DTI) parameters in the substantia nigra and putamen between the two hemispheres contralateral to the symptomatic and non-symptomatic side in H&Y stage-1 PD patients who had onset of symptoms between ages of 40-59 years. RESULTS There were quantifiable hemispheric asymmetries in transverse relaxation rates in the substantia nigra, as well as fractional anisotropy and mean diffusivity in the putamen in early PD, which correlated with the unilaterality of motor symptoms as evaluated using the motor portion of the Unified Parkinsons Disease Rating Scale. CONCLUSION Transverse relaxation mapping and DTI demonstrated significant differences between the symptomatic and non-symptomatic hemispheres at the early stage of early-onset PD. These findings support the hypothesis of asymmetric neurodegeneration in the bilateral nigrostriatal pathways in the early stage of the disease.

Ethylene Glycol Toxicity: Chemistry, Pathogenesis, and Imaging

The ingestion of ethylene glycol results in toxicity with characteristic chemical, pathological, and imaging findings. In the case presented, magnetic resonance imaging demonstrated bilateral symmetric hyperintensity within the basal ganglia, thalami, and brainstem. Ethylene glycol toxicity also resulted in restricted diffusion within the white matter tracts of the corona radiata, a finding not previously described in the literature. In the acute clinical setting, ethylene glycol toxicity is an important differential consideration of the pathologies involving the deep grey matter nuclei.

Characteristic MRI findings in neonatal nonketotic hyperglycinemia due to sequence changes in GLDC gene encoding the enzyme glycine decarboxylase.

Neonatal metabolic encephalopathy may be related to electrolyte imbalances, endocrine dysfunction, or inborn errors of metabolism. The metabolic encephalopathies are always a diagnostic challenge to the neonatologist and pediatricians. This is more so because the signs and symptoms of are nonspecific and are often similar to those with other neonatal emergencies. Clinical suspicion of neonatal encephalopathy should be considered in any infant exhibiting an abnormal level of consciousness, seizures, tone and reflex abnormalities, apnea, aspiration, and feeding difficulties. A definitive diagnosis is frequently not possible during the neonatal care unit or emergency department. But the proper initial management based on the probable diagnosis can be life-saving or reduce neurologic sequelae. In the case of inborn errors of metabolism, imaging may play a vital role either in limiting the differential diagnosis or yet times pointing towards the specific diagnosis or error of metabolism. We report DWI-ADC changes on MRI in the acute stages of neonatal nonketotic hyperglycinemia (NKH) due to sequence changes in GLDC gene.

Submandibular and Sublingual Spaces: Diagnostic Imaging and Evaluation

The mylohyoid muscle divides the lower part of the oral cavity into 2 spaces: the sublingual space, which is located superior to the muscle, and the submandibular space, inferior to the muscle but superior to the hyoid bone. Although the submandibular and sublingual spaces are small, a wide range of pathologic processes may involve these spaces. They include cystic lesions, inflammatory conditions with various causes, rare vascular lesions, and benign and malignant neoplasms. This article outlines the radiologic anatomy of the region, describes the various pathologic processes that may affect it, and discusses the use of imaging in their evaluation.

Optimization of patient dose and image quality with z-axis dose modulation for computed tomography (CT) head in acute head trauma and stroke

The purpose of this study is to retrospectively analyze the effect of z-axis modulation for CT head protocols on patient dose and image quality in patients with acute head trauma and stroke. The study was approved by the Institutional Review Board. We retrospectively evaluated the effect of dose modulation on unenhanced CT head examinations in patients with acute head trauma and stroke. Two series of 100 consecutive studies were reviewed: 100 studies performed without dose modulation, 100 studies performed with z-axis dose modulation. Multidetector 16-section CT was performed sequentially and axial 5-mm-thick slices were obtained from base of skull to vertex. With z-axis dose modulation, the same tube current range was maintained, but a computer algorithm altered the tube current applied to each CT section. For each examination, the weighted volume CT dose index (CTDI (vol)) and dose-length product (DLP) were recorded and noise was measured. Each study was also reviewed for image quality by two independent, blinded readers. The variables (CTDI (vol) and DLP, image quality, and noise) in the two groups were compared by using student t test and Wilcoxon rank-sum test. For unenhanced CT head examinations, the CTDI (vol) and DLP, respectively, were reduced by 35.8% and 35.2%, respectively, by using z-axis dose modulation. Image quality and noise were unaffected by the use of this dose modulation technique (P < 0.004). Utilization of z-axis modulation technique for CT head examination in patients with acute head trauma and stroke offers significant radiation dose reduction while image quality is optimally maintained.

Imaging Approach to the Cord T2 Hyperintensity (Myelopathy)

In clinically suspected cases of myelopathy, magnetic resonance imaging without and with gadolinium remains the modality of choice. The first and best imaging approach in the evaluation of myelopathy is to identify whether the cause of myelopathy is compressive or noncompressive. The commonest imaging finding in myelopathy is either focal or diffuse cord hyperintensity on the T2-weighted magnetic resonance images. Detailed clinical history, acuity of symptoms (acute vs insidious onset), distribution of the signal abnormalities, including length of cord involvement, specific tract involvement, and the region of the spinal cord that is affected, are very useful in making the diagnosis.

A Pattern Approach to Focal White Matter Hyperintensities on Magnetic Resonance Imaging

Evaluation of focal white matter hyperintensities on magnetic resonance imaging in any age group is always challenging because the cause of these hyperintensities varies extensively. Understanding the clinical presentation, pathophysiology, and associated imaging findings can allow the radiologist to limit the differential diagnosis. A specific imaging approach including age, pattern of distribution, signal characteristics on various sequences, enhancement pattern, and other ancillary findings helps to identify a correct cause for these hyperintensities. This article provides a pattern approach to differentiate various common and a few uncommon diseases presenting as focal white matter hyperintensities.

Malformations of cortical development.

The advent of high resolution MRI techniques has revolutionized the imaging of cortical malformations. Today, specific gene defects have been identified to be responsible for several of the developmental cortical malformations. In this article we have discussed the developmental cortical malformations under stages of proliferation, migration and organization. The relevant molecular genetics and its relationship to the cortical defects are also outlined. Neuroimaging features and relevant etio-pathogenesis of various cortical malformations are discussed in detail.

Imaging Anatomy of Deep Neck Spaces

This article presents a comprehensive analysis of the neck fascia and neck spaces that are formed by the interplay of the different fascial layers. Because a solid and thorough understanding of the anatomy and relationship of the various neck spaces is so valuable in diagnosing and treating diseases of the neck, this information organizes the anatomic areas of the neck beginning with and overview, followed by extent, anatomic relationship, and contents. Detailed enhanced computed tomography images display the anatomic areas of the neck.

Malformations of Ventral Induction

t o s t p o T f a Ventral induction occurs during 5-10 weeks of gestation. During this phase 3 primary vesicles (prosencephalon, esencephalon, and rhombencephalon) are differentiated to orm forebrain, midbrain, and hindbrain, respectively.1 Norally, early forebrain vesicles, prosencephalon, develop in he rostral end of the neural tube between 22 and 24 days of estation. The prosencephalon forms 2 laterally directed dierticula by 5-6 weeks and is divided into telencephalon future cerebrum) and diencephalon (future thalamus and ypothalamus). Diencephalon and telencephalon differentition occurs from the provesicle before the neural tube loses. Any insult during this phase affects the development f brain vesicles and the formation of the facial skeleton. cular and nasal anomalies are frequently associated with orebrain malformation because the optic placode and forerain develop at the same time, with subsequent formation of he olfactory vesicle 1 week later. The rhombencephalon diides into metencephalon (future pons and cerebellum) and yelencephalon (future medulla). Malformation of the hombencephalon is discussed in detail in this issue under Posterior Fossa Malformations.” The commonly seen forebrain ventral induction malforations are (1) holoprosencephaly, (2) atelencephaly, (3) lfactory aplasia, (4) agenesis of the corpus callosum, (5) genesis of the septum pellucidum (septo-optic dysplasia and avum vergae and pellucidum).