Ari M. Blitz

Reproducibility of Quantitative Tractography Methods Applied to Cerebral White Matter

Tractography based on diffusion tensor imaging (DTI) allows visualization of white matter tracts. In this study, protocols to reconstruct eleven major white matter tracts are described. The protocols were refined by several iterations of intra- and inter-rater measurements and identification of sources of variability. Reproducibility of the established protocols was then tested by raters who did not have previous experience in tractography. The protocols were applied to a DTI database of adult normal subjects to study size, fractional anisotropy (FA), and T2 of individual white matter tracts. Distinctive features in FA and T2 were found for the corticospinal tract and callosal fibers. Hemispheric asymmetry was observed for the size of white matter tracts projecting to the temporal lobe. This protocol provides guidelines for reproducible DTI-based tract-specific quantification.

Quantitative video-oculography to help diagnose stroke in acute vertigo and dizziness: Toward an ECG for the eyes

Background and Purpose— Strokes can be distinguished from benign peripheral causes of acute vestibular syndrome using bedside oculomotor tests (head impulse test, nystagmus, test-of-skew). Using head impulse test, nystagmus, test-of-skew is more sensitive and less costly than early magnetic resonance imaging for stroke diagnosis in acute vestibular syndrome but requires expertise not routinely available in emergency departments. We sought to begin standardizing the head impulse test, nystagmus, test-of-skew diagnostic approach for eventual emergency department use through the novel application of a portable video-oculography device measuring vestibular physiology in real time. This approach is conceptually similar to ECG to diagnose acute cardiac ischemia. Methods— Proof-of-concept study (August 2011 to June 2012). We recruited adult emergency department patients with acute vestibular syndrome defined as new, persistent vertigo/dizziness, nystagmus, and (1) nausea/vomiting, (2) head motion intolerance, or (3) new gait unsteadiness. We recorded eye movements, including quantitative horizontal head impulse testing of vestibulo-ocular-reflex function. Two masked vestibular experts rated vestibular findings, which were compared with final radiographic gold-standard diagnoses. Masked neuroimaging raters determined stroke or no stroke using magnetic resonance imaging of the brain with diffusion-weighted imaging obtained 48 hours to 7 days after symptom onset. Results— We enrolled 12 consecutive patients who underwent confirmatory magnetic resonance imaging. Mean age was 61 years (range 30–73), and 10 were men. Expert-rated video-oculography–based head impulse test, nystagmus, test-of-skew examination was 100% accurate (6 strokes, 6 peripheral vestibular). Conclusions— Device-based physiological diagnosis of vertebrobasilar stroke in acute vestibular syndrome should soon be possible. If confirmed in a larger sample, this bedside eye ECG approach could eventually help fulfill a critical need for timely, accurate, efficient diagnosis in emergency department patients with vertigo or dizziness who are at high risk for stroke.

Small strokes causing severe vertigo Frequency of false-negative MRIs and nonlacunar mechanisms

Objective: Describe characteristics of small strokes causing acute vestibular syndrome (AVS). Methods: Ambispective cross-sectional study of patients with AVS (acute vertigo or dizziness, nystagmus, nausea/vomiting, head-motion intolerance, unsteady gait) with at least one stroke risk factor from 1999 to 2011 at a single stroke referral center. Patients underwent nonquantitative HINTS “plus” examination (head impulse, nystagmus, test-of-skew plus hearing), neuroimaging to confirm diagnoses (97% by MRI), and repeat MRI in those with initially normal imaging but clinical signs of a central lesion. We identified patients with diffusion-weighted imaging (DWI) strokes ≤10 mm in axial diameter. Results: Of 190 high-risk AVS presentations (105 strokes), we found small strokes in 15 patients (median age 64 years, range 41–85). The most common vestibular structure infarcted was the inferior cerebellar peduncle (73%); the most common stroke location was the lateral medulla (60%). Focal neurologic signs were present in only 27%. The HINTS “plus” battery identified small strokes with greater sensitivity than early MRI-DWI (100% vs 47%, p < 0.001). False-negative initial MRIs (6–48 hours) were more common with small strokes than large strokes (53% [n = 8/15] vs 7.8% [n = 7/90], p < 0.001). Nonlacunar stroke mechanisms were responsible in 47%, including 6 vertebral artery occlusions or dissections. Conclusions: Small strokes affecting central vestibular projections can present with isolated AVS. The HINTS “plus” hearing battery identifies these patients with greater accuracy than early MRI-DWI, which is falsely negative in half, up to 48 hours after onset. We found nonlacunar mechanisms in half, suggesting greater risk than might otherwise be assumed for patients with such small infarctions.

Visual and neurological outcomes following endovascular stenting for pseudotumor cerebri associated with transverse sinus stenosis

Background: Pseudotumor cerebri (PTC) is characterized by raised intracranial pressure (ICP) without an identifiable mass, evidence of hydrocephalus, or abnormal cerebrospinal fluid content. In the past, most cases of PTC appeared to have no identifiable etiology, and thus, they were classified as “idiopathic intracranial hypertension” (IIH). Recently, however, a subset of patients with presumed IIH has been found to have evidence of cerebral dural sinus stenoses, particularly involving one or both transverse sinuses (TS). The belief that the stenoses are the cause, rather than an effect of the increased ICP, has led investigators to recommend stenting of the stenosed sinus for the treatment of the condition. We describe detailed visual and neurological outcomes after stenting for PTC associated with hemodynamically significant dural sinus stenosis. Methods: All patients with PTC had initial neurological, neuro-ophthalmological, and imaging assessments. Regardless of the findings, all were treated with medical therapy. If medical therapy failed and TS stenosis was detected on contrast-enhanced magnetic resonance or computed tomographic venography, catheter cerebral angiography with venous manometry was performed. If a mean pressure gradient (MPG) of 4 mm Hg or greater was present, unilateral transverse sinus stenting was performed. Results: Twelve patients with PTC and TS stenosis associated with an MPG of >4 mm Hg who failed medical therapy were identified. TS stenting significantly decreased the pressure gradient in all cases. Unilateral stenting was sufficient to reduce pressure gradients even when the stenosis was bilateral. At a mean follow-up of 16 months (range, 9–36 months), tinnitus had improved in all patients, and 10 of 12 patients had improvement in visual function. Seven patients had significant improvement in headaches. Conclusion: In this small series of patients with PTC associated with TS stenosis, endovascular stent placement was generally effective in treating visual dysfunction and tinnitus, although not headaches. The optimum gradient and vascular characteristics amenable for selection of patients for stenting needs further research.

Radiologic Evaluation of Larynx Cancer

The authors present the value of imaging for preoperative evaluation of structures that are not assessed or incompletely assessed on physical and endoscopic examination. Discussed are CT, MRI, and positron emission tomography-CT and the appropriate selection of each method to provide information, including the presence or absence of extent of disease to the pre-epiglottic and paraglottic spaces and the subglottis, cartilage invasion, extralaryngeal spread of disease, nodal metastasis, and tumor volume.

High-Resolution CISS MR Imaging With and Without Contrast for Evaluation of the Upper Cranial Nerves: Segmental Anatomy and Selected Pathologic Conditions of the Cisternal Through Extraforaminal Segments

The authors review the course and appearance of the major segments of the upper cranial nerves from their apparent origin at the brainstem through the proximal extraforaminal region, focusing on the imaging and anatomic features of particular relevance to high-resolution magnetic resonance imaging evaluation. Selected pathologic entities are included in the discussion of the corresponding cranial nerve segments for illustrative purposes.

Anatomic Considerations, Nomenclature, and Advanced Cross-sectional Imaging Techniques for Visualization of the Cranial Nerve Segments by MR Imaging

Various methods of cross-sectional imaging are used for visualization of the cranial nerves, relying heavily on MR imaging. The success of the MR imaging sequences for visualization of cranial nerves depends on their anatomic context at the point of evaluation. The heterogeneity of opinion regarding optimal evaluation of the cranial nerves is partly a function of the complexity of cranial nerve anatomy. A variety of approaches are advocated and variations in equipment and terminology cloud the field. This article proposes a segmental classification and corresponding nomenclature for imaging evaluation of the cranial nerves and reviews technical considerations and applicable literature.

Diffusion Tensor Imaging of Cerebral White Matter: Technique, Anatomy, and Pathologic Patterns

Diffusion tensor imaging is a magnetic resonance imaging technique that provides insight into the anatomy and integrity of white matter pathways in the brain. Further processing of these data can help map individual tracts, which can aid in surgical planning. Understanding the basics of this technique can improve characterization of white matter development and disorders.

Imaging of the Paranasal Sinuses

Imaging of sinonasal disease has progressed over the past 30 years, with each new imaging modality providing new functionality, while also encroaching on the domain of previous techniques. Although radiographs were once the most requested imaging study for paranasal sinus evaluation, this has largely been supplanted by computed tomography (CT). CT is readily accessible and fast and provides superior anatomic and osseous detail. Magnetic resonance imaging (MRI) provides improved soft-tissue contrast resolution, allowing for improved depiction and characterization of extrasinus soft-tissue inflammatory involvement, fungal elements, and sinonasal masses. In this article, we discuss the anatomy and anatomical variants of the paranasal sinuses and anterior skull base, as well as pertinent disease processes.

A Novel Frame Shift Mutation in the GHRH Receptor Gene in Familial Isolated GH Deficiency: Early Occurrence of Anterior Pituitary Hypoplasia

BACKGROUND Mutations in the genes encoding for GHRH receptor (GHRHR) and GH (GH1) are the most common cause of familial isolated GH deficiency (IGHD). GHRHR mutations are often associated with anterior pituitary hypoplasia (APH), but this has been reported almost exclusively in children older than 8 yr. We analyzed the GHRHR and measured pituitary size in a consanguineous family with the father and three of the five siblings with IGHD. OBJECTIVE The aim of the study was to find the mutated gene in a family with severe IGHD. METHODS We sequenced the whole GHRHR coding regions and the intron-exon boundaries from peripheral DNA of the index patient. After identifying the novel mutation, we sequenced the region of interest in the other members of the family. We measured the anterior pituitary volume from magnetic resonance imaging (MRI). RESULTS The father and the three affected children were homozygous for a new frame-shift mutation in the coding sequence of exon 4 (corresponding to the extracellular domain of the receptor) (c.340delG) that places the downstream sequence out of frame [corrected]. The mother and two unaffected siblings were heterozygous for the mutation. Two of the affected children had MRI evidence of APH before reaching 6 yr of age. CONCLUSIONS We describe a new mutation in the GHRHR in a family with IGHD. The presence of frank APH before age 6 yr shows that MRI-evident reduced pituitary size can be present in GHRHR mutations even in children younger than 8 yr of age.