Cranial CT with 64-, 16-, 4- and single-slice CT systems-comparison of image quality and posterior fossa artifacts in routine brain imaging with standard protocols. Eur Radiol. 2008;18:1720-1726. [PMID: 18389247 DOI: 10.1007/s00330-008-0937-6]

A Case of Cobra Bite Complicated with Basilar Artery Occlusion

Snakebite is one of the most common complaints related to wilderness medicine. Venomous snakebite manifestation is divided into local and systemic envenomation. For the Elapidae group, the most feared complication is respiratory muscle paralysis due to neurotransmitter malfunction at the neuromuscular junction level which leads to respiratory insufficiency. However, there is a lack of evidence or case report incidence to suggest that it can potentially associate with the development of stroke disorder. We present a rare case of massive posterior circulation infarct in a middle-aged gentleman following a cobra bite. He was brought to our center few hours later following the bite and antivenom was administered. He improved shortly after receiving it. However, he had an abrupt drop in his conscious level several hours later. Noncontrast-enhanced computed tomography (NCCT) brain was performed immediately, but stroke disorder was excluded prematurely. Repeated NCCT imaging which was done 12 h apart showed massive posterior circulation infarction with hydrocephalus. He succumbed to death 3 days later. Given its rarity, the evolution of his clinical condition warrants clinician's early suspicion of potential stroke-related complications that can occur following a cobra bite.

Cerebellum and neurodegenerative diseases: Beyond conventional magnetic resonance imaging

The cerebellum plays a key role in movement control and in cognition and cerebellar involvement is described in several neurodegenerative diseases. While conventional magnetic resonance imaging (MRI) is widely used for brain and cerebellar morphologic evaluation, advanced MRI techniques allow the investigation of cerebellar microstructural and functional characteristics. Volumetry, voxel-based morphometry, diffusion MRI based fiber tractography, resting state and task related functional MRI, perfusion, and proton MR spectroscopy are among the most common techniques applied to the study of cerebellum. In the present review, after providing a brief description of each technique’s advantages and limitations, we focus on their application to the study of cerebellar injury in major neurodegenerative diseases, such as multiple sclerosis, Parkinson’s and Alzheimer’s disease and hereditary ataxia. A brief introduction to the pathological substrate of cerebellar involvement is provided for each disease, followed by the review of MRI studies exploring structural and functional cerebellar abnormalities and by a discussion of the clinical relevance of MRI measures of cerebellar damage in terms of both clinical status and cognitive performance.

Conjugate eye deviation as predictor of acute cortical and subcortical ischemic brain lesions

OBJECTIVES

Non-enhanced computed tomography (NECT) of the brain is used to exclude intracranial hemorrhage in patients who are considered for treatment with tissue plasminogen activator due to stroke symptoms. However, early infarct signs on NECT have low sensitivity for ischemic stroke. It was hypothesized that horizontal conjugate eye deviation (average ocular gaze deviation-OGD >14°) on NECT predicts ischemic brain injury on a second detailed examination.

PATIENTS AND METHODS

Patients who underwent brain NECT within three hours after the onset of stroke symptoms and subsequently had brain CT scan with intravenous contrast or MRI were potential participants. OGD was measured from the cross-sectional image including both globes at their maximum diameter.

RESULTS

73 subjects were studied (mean age 64.2±20.8 years) with a median interval (interquartile range) of 56 h (22-109.3 h) between NECT and the second examination. On NECT, 24 of 73 (32.9%) subjects had OGD >14°. Of 32 individuals with acute ischemic injury on the second examination, 19 (59.4%) had OGD >14° on NECT. OGD >14° was associated with increased risk of ischemic injury: OR=10.5 (95% confidence interval 3.33-33.9); P=0.002. OGD >14° had significantly higher sensitivity and negative predictive value than early infarct signs on NECT (59.4% vs. 21.9% and 73.5% vs. 59.7%, respectively; P<0.05), and similar specificity and positive predictive value (87.8% vs. 90.2% and 79.2% vs. 63.6%; P>0.05).

CONCLUSION

In the presence of stroke symptoms, average OGD >14° on the initial brain NECT is early predictor of ischemic brain injury.

Improved delineation of arteries in the posterior fossa of the brain by model-based iterative reconstruction in volume-rendered 3D CT angiography

BACKGROUND AND PURPOSE

Improved CTA delineation of arteries and unruptured aneurysms is clinically desired in the posterior fossa. We present a novel model-based iterative reconstruction that models system statistics and optics to improve CT image quality. We investigated the utility of MBIR for improving delineation of arteries in the posterior fossa on 3D brain CTA.

MATERIALS AND METHODS

Using filtered back-projection with a standard kernel and MBIR, we reconstructed axial images of 0.625-mm thickness of 28 consecutive patients (14 men; mean age, 58.6 ± 14.6 years) who underwent 64-detector brain CTA. We placed regions of interest on the axial images, measured the mean CT value in the basilar artery and the value and SD in the pons and bilateral cerebellar hemispheres, and calculated the contrast-to-noise ratio of the brain arteries in the posterior fossa. Using volume-rendered CTA and a 4-point scale, 2 radiologists independently graded delineation of the BA, bilateral vertebral artery, superior cerebellar artery, and anterior and posterior inferior cerebellar arteries. We compared the results between FBP and MBIR by using paired t and Wilcoxon signed-rank tests.

RESULTS

Compared with FBP, MBIR significantly improved the contrast-to-noise ratio (P < .0001) and subjective delineation of all arteries in the posterior fossa except the BA (VA, SCA, AICA, and PICA; P < .05 for all). The mean visual score by MBIR was 3.0 or higher for all those arteries except the AICA assessed by reader 1 (2.6 ± 0.7).

CONCLUSIONS

With 3D brain CTA, contrast-to-noise ratio and arterial delineation of the VA, SCA, AICA, and PICA in the posterior fossa are better with MBIR than FBP.

Alternative oblique head CT scanning technique reduces bone artifact and improves interpretability of brainstem anatomy

Brainstem pathology due to infections, infarcts and tumors are common in developing countries, but neuroimaging technology in these resource-poor settings is often limited to single slice, and occasionally spiral, CT. Unlike multislice CT and MRI, single slice and spiral CT are compromised by bone artifacts in the posterior fossa due to the dense petrous bones, often making imaging of the brainstem non-diagnostic. With appropriate head positioning, the petrous ridges can be avoided with 40° sagittal oblique scans parallel to either petrous ridge. We describe an alternative sagittal oblique scanning technique that significantly reduces brainstem CT artifacts thereby improving clarity of anatomy. With Institutional Ethical approval, 13 adult patients were enrolled (5 males; 39%). All patients had routine axial brain CT and sagittal oblique scans with no lesions found. Images were read by 2 readers who gave a score for amount of artefact and clarity of structures in the posterior fossa. The mean artifact score was higher for routine axial images compared to sagittal oblique (2.92 vs. 1.23; P<0.0001). The mean anatomical certainty scores for the brainstem were significantly better in the sagittal oblique views compared to routine axial (1.23 vs. 2.77; P<0.0001). No difference was found between the two techniques with respect to the fourth ventricle or the cerebellum (axial vs. sag oblique: 1.15 vs. 1.27; P=0.37). When using single slice CT, the sagittal oblique scanning technique is valuable in improving clarity of anatomy in the brainstem if axial images are non-diagnostic due to bone artifacts.