Most dementias begin insidiously, developing slowly and generally occurring in the elderly age group. The so-called rapidly progressive dementias constitute a different, diverse collection of conditions, many of which are reversible or treatable. For this reason, accurate identification and assessment of acute and subacute forms of dementia are critical to effective treatment; neuroimaging aids greatly in narrowing the diagnosis of these conditions. This second installment of a 2-part review of rapidly progressive dementias examines the use of imaging in an assortment of other etiologies in the differential diagnosis, from prion disease and neoplastic-related conditions to rare metabolic and other conditions such as Wernicke encephalopathy. In these clinical conditions, MR imaging has the potential to narrow this broad differential diagnosis and, at times, can definitively aid in the diagnosis of certain conditions on the basis of typical imaging patterns.

ALS : amyotrophic lateral sclerosis UMN : upper motor neuron LMN : lower motor neuron fALS : familial amyotrophic lateral sclerosis sALS : sporadic amyotrophic lateral sclerosis Amyotrophic lateral sclerosis (ALS) reflects a heterogeneous group of neurodegenerative disorders unified by

In this issue of the American Journal of Neuroradiology , a novel approach by means of MR-guided, focused sonography surgery (MRgFUS) is used to treat essential tremor.[1][1] The results indicate that clinical improvement is significantly related to total lesion size. No relationship was found

Imaging patients with seizures presents a challenge to both clinician and radiologist, especially when symptoms or EEG features are atypical, not conforming to established epilepsy syndromes or EEG patterns. Appropriate, directed use of MRI enhances the detection of underlying epileptogenic foci and can evaluate both common and unusual etiologies. This review examines imaging evaluation of epilepsies due to uncommon presentations of common conditions, unusual conditions and atypical seizure presentations. Understanding these uncommon presentations of seizures ensures optimal clinical management and can guide appropriate intervention. Advances in newer imaging methods including diffusion tensor imaging, functional connectivity MRI, magnetic source imaging and magnetic resonance spectroscopic imaging can further increase sensitivity to detect subtle structural abnormalities causing epilepsy and can also be used to plan more successful epilepsy surgery.

Alzheimer disease prevails as a major cause of disability in the elderly population and ranks as the most common form of dementia that affects 1 of 8 individuals older than 65 years of age. Most AD cases are late in onset and are probably influenced by both genetic and environmental factors. Apart from age, the risk factors include family history; brain injury, both traumatic and vascular; and metabolic diseases, such as diabetes, hypercholesterolemia, and obesity. Based on twin studies, inheritance plays a role in approximately 80% of cases (familial and sporadic).

HD : Huntington disease CAG : cytosine-adenine-guanine Huntington disease (HD) is an autosomal dominant genetic condition that can affect movement and cognition and is progressive and fatal. It results from genetic mutations involving trinucleotide repeats of the huntingtin gene, which encodes

SCA : spinocerebellar ataxia Ataxia is a neurologic disorder in which there is loss of coordination of movement. It can result from dysfunction of the cerebellum and brain stem and their afferent or efferent pathways. The etiology of ataxia can be divided into 3 main categories: acquired,

As experts in the realm of applying brain imaging technology for meaningful information on an individual patient's medical care, neuroradiologists can provide a physiologic, pathophysiologic, and clinical context for the advances achieved from brain-mapping. Precise identification of the abnormalities involved in brain conditions resulting from a multidisciplinary effort including neuroradiology will help to further define the nature of the pathology, evaluate the results of therapy, and improve health care.

Neurofibromatosis types 1 and 2 are a group of neurocutaneous syndromes resulting from disorders in cell regulation. Despite sharing a common name, neurofibromatosis types 1 and 2 are quite distinct phakomatoses, both clinically and genetically.

CJD : Creutzfeldt-Jakob Disease PRNP : prion protein gene Protein infectious agent or “prion” is a concept developed by Stanley Prusiner in the 1980s of a form of infectious disease involving proteins rather than traditional pathogens.[1][1] More accurately, prion disease is a

SUMMARY: Advances in nanotechnology have the potential to dramatically enhance the detection of neurologic diseases with targeted contrast agents and to facilitate the delivery of focused therapies to the central nervous system. We present the physicochemical rationale for their use, applications in animal models, and ongoing clinical trials using these approaches. We highlight advances in the use of nanoparticles applied to brain tumor imaging, tumor angiogenesis, neurodegeneration, grafted stem cells, and neuroprogenitor cells.

SUMMARY: Most dementias begin insidiously, developing slowly and generally occurring in the elderly age group. The so-called rapidly progressive dementias constitute a different, diverse collection of conditions, many of which are reversible or treatable. For this reason, prompt identification and assessment of acute and subacute forms of dementia are critical to effective treatment. Numerous other entities within this category of presenile rapid-onset dementias are untreatable such as the prion-related diseases. Neuroimaging aids in the diagnosis and evaluation of many of these rapidly progressive dementias, which include myriad conditions ranging from variations of more common neurodegenerative dementias, such as Alzheimer disease, dementia with Lewy bodies, and frontotemporal dementia; infectious-related dementias such as acquired immune deficiency syndrome dementia; autoimmune and malignancy-related conditions; to toxic and metabolic forms of encephalopathy. This first of a 2-part review will specifically address the ability of MR imaging and ancillary neuroimaging strategies to support the diagnostic evaluation of rapidly progressive dementias due to neurodegenerative causes.

GABA serves as a major neurotransmitter of the brain and functions mainly to inhibit neural excitatory activity. Disruption of the GABAergic processes appears to occur in various neurologic and psychiatric conditions, including epilepsy, mood disorders, motor disorders such as focal dystonia and stiff-person syndrome, sleep disorders, neuroplasticity, and drug and alcohol dependence. These concentration differences may be ascertained by using MR spectroscopy to provide information on the concentration of different metabolites. This review briefly discusses advances in MR spectroscopy methods and explores the application of this technique to detect changes in GABA due to disease processes and medication-induced effects.

Papilledema, defined as swelling of the optic disc, frequently occurs in the setting of increased ICP and in a variety of medical conditions, including pseudotumor cerebri, sinus thrombosis, intracerebral hemorrhage, frontal lobe neoplasms, and Chiari malformation. Noninvasive imaging of the ON is possible by using MR imaging, with a variety of findings occurring in the setting of papilledema, including flattening of the posterior sclera, protrusion of the optic disc, widening of the ONS, and tortuosity of the ON. Early recognition of papilledema and elevated ICP is of paramount importance for ensuring restoration of vision. Newer advanced MR imaging techniques such as fMRI and DTI may prove useful in the future to assess the potential effects of papilledema on retinal and visual pathway integrity.

PTC is a clinical entity of uncertain etiology characterized by intracranial hypertension. The syndrome classically manifests with headaches and visual changes in women with obesity. Traditionally, imaging ruled out secondary causes of elevated CSF pressure but now may reveal findings frequently seen in patients with PTC, including the following: flattening of the globe, an empty sella, an enlarged ONS, protrusion and enhancement of the optic nerve head, and increased tortuosity of the optic nerve. Novel imaging methods, including MR venography, have additionally identified sinovenous stenosis as a potential indicator of PTC.

Background: Patients with stiff-person syndrome (SPS) have circulating antibodies against glutamic acid decarboxylase, the rate-limiting enzyme responsible for the synthesis of γ-aminobutyric acid (GABA). Although the patients' symptoms of stiffness and unexpected spasms can be explained on the basis of reduced or impaired inhibitory neuro transmitters, such as GABA, it is unclear whether the level of GABA in the brains of these patients is reduced and, if so, whether the reduction is due to anti-glutamic acid decarboxylase antibodies.Objective: To measure GABA levels in the brains of patients with SPS.Design: Prospective case-control study.Setting: National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Md.Patients: Eight patients with SPS with high titers of circulating anti-glutamic acid decarboxylase antibodies and typical clinical symptoms of SPS and 16 control subjects.Main Outcome Measures: Results of brain magnetic resonance imaging and magnetic resonance spectroscopy, which measures GABA levels in specific brain regions.Results: No abnormalities were noted on brain magnetic resonance images. A prominent and significant decrease in GABA level was, however, observed in the sensorimotor cortex and a smaller decrease in the posterior occipital cortex but not in the cingulate cortex or pons.Conclusions: The reduction of brain GABA in patients with SPS supports the clinical symptoms and indicates that the inhibitory GABAergic pathways are involved in the disease. Regardless of the responsible autoantigens, in SPS autoantibodies block the function of GABAergic neurons and interfere with the synthesis of GABA but do not cause structural changes in the brain.

Patients with task-specific dystonia (writer's cramp) have impaired cortical inhibition likely arising from striatal dysfunction. However, the levels of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the brains of these patients are not known. In this study, we evaluated 7 patients with right-sided focal, task-specific dystonia and 17 normal control subjects. A novel method using two-dimensional J-resolved magnetic resonance spectroscopy revealed that brain GABA levels are decreased in specific brain regions of the focal dystonia patients compared to normal controls. A significant decrease in GABA level was observed in the sensorimotor cortex and lentiform nuclei contralateral to the affected hand, while there was only a small nonsignificant decrease in the ipsilateral sensorimotor cortex and lentiform nuclei. GABA changes in the posterior occipital region of patients were not significant. The impaired cortical GABA level correlates with prior physiologic studies showing reduced intracortical inhibition. Reduced GABA in the striatum is consistent with striatal dysfunction since GABA is a principal neurotransmitter in that region. The reduction of brain GABA in dystonia patients may explain the clinical symptomatology of focal dystonia. Magnetic resonance spectroscopy may be a useful noninvasive tool in the evaluation of regional brain GABA changes and in monitoring the effects of various therapies.

Proton MRS was performed in a patient with developmental acalculia. The results indicated a focal, wedge-shaped defect in the left temporoparietal brain region near the angular gyrus, with differential decreases in N-acetyl-aspartate, creatine, and choline, These results support the hypothesis that developmental acalculia, like acquired acalculia, is associated with left posterior hemisphere lesions.