Abscess of the medulla oblongata following endotracheal intubation.
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Aged↗
Biomedical subjects
S J Hickman
Publications and source records attributed to S J Hickman.
Diffusion MRI in multiple sclerosis.
Diffusion imaging is a quantitative, MR-based technique potentially useful for the study of multiple sclerosis (MS), due to its increased pathologic specificity over conventional MRI and its ability to assess in vivo the presence of tissue damage occurring outside T2-visible lesions, i.e., in the so-called normal-appearing white and gray matter. The present review aims at critically summarizing the state-of-the-art and providing a background for the planning of future diffusion studies of MS. Several pieces of evidence suggest that diffusion-weighted and diffusion tensor MRI are sensitive to MS damage and able to detect its evolution over relatively short periods of time. Although a significant relationship between diffusion-weighted MRI findings and MS clinical disability was not found in the earliest studies, with improved diffusion imaging technology correlations between diffusion abnormalities and MS clinical aspects are now emerging. However, the best acquisition and postprocessing strategies for MS studies remain a matter of debate and the contribution of newer and more sophisticated techniques to diffusion tensor MRI investigations in MS needs to be further evaluated. Although changes in diffusion MRI indices reflect a net loss of structural organization, at present we can only speculate on their possible pathologic substrates in the MS brain. Postmortem studies correlating diffusion findings with histopathology of patients with MS are, therefore, also warranted.
Autopsy↗
The optic nerve sheath on MRI in acute optic neuritis.
Optic nerve sheath dilatation or gadolinium-enhancement on magnetic resonance imaging in acute optic neuritis have been previously reported but have been thought to be rare occurrences. This study recruited 33 patients with acute unilateral optic neuritis. All had their optic nerves imaged with fat-saturated fast spin-echo (FSE) imaging, and 28 had imaging before and after triple-dose gadolinium-enhanced fat-saturated T(1)-weighted imaging. Follow-up imaging was performed on 20 patients (15 following gadolinium). A dilated subarachnoid space at the anterior end of the symptomatic optic nerve on FSE imaging was seen in 15/33 cases. In three of these cases, dilatation was visible on short-term follow-up. Optic nerve sheath enhancement was seen in 21/28 cases acutely: seven at the anterior end of the lesion only, five at the posterior end only and nine at both ends. Optic sheath enhancement was seen in 13 patients on follow-up. This study suggests that optic nerve sheath dilatation on FSE images and optic nerve sheath enhancement on triple-dose gadolinium-enhanced images are common findings in acute optic neuritis. Optic nerve sheath dilatation may be due to inflammation of the optic nerve, with its associated swelling, interrupting the communication between the subarachnoid space of the diseased optic nerve and the chiasmal cistern. Optic nerve sheath enhancement suggests that meningeal inflammation occurs in optic neuritis, in agreement with pathological studies of both optic neuritis and multiple sclerosis.
Acute Disease↗
Imaging spinal cord damage in multiple sclerosis.
During the past 2 decades, the considerable improvement of magnetic resonance (MR) technology and the development of new MR strategies capable of providing an in vivo overall assessment of multiple sclerosis (MS) pathology have allowed us to obtain important novel pieces of information on disease evolution in the brain. However, despite this, the correlation between brain MR imaging metrics and clinical disability are still suboptimal. A reason for this discrepancy might be the involvement of clinically eloquent structures, such as the spinal cord, which owing to technical challenges have not been extensively studied using MR imaging until very recently. An objective and accurate estimate of the presence and extent of spinal cord damage might indeed contribute to increasing the strength of the correlations between clinical and MRI metrics. This review summarizes the main results obtained from the application of conventional and modern MR-based techniques for the evaluation of spinal cord damage in MS.
Diffusion Magnetic Resonance Imaging↗
Imaging the optic nerve in multiple sclerosis.
Although multiple sclerosis (MS) frequently involves the optic nerves, imaging this structure is not yet performed routinely in clinical practice. The recent improvement of magnetic resonance (MR) technology and the development of new MR strategies, capable of providing an, in vivo, overall assessment of MS pathology has allowed objective metrics to be obtained for monitoring disease evolution, essentially in the brain. However, despite this progress, the correlation between brain MR metrics of the disease and clinical disability are still disappointing. An objective and accurate estimate of the presence and extent of optic nerve involvement might help to overcome this clinical/MRI paradox. This review summarizes the main results obtained from the application of conventional and modern MR-based techniques for the evaluation of optic nerve damage in MS.
Atrophy↗
Serial magnetization transfer imaging in acute optic neuritis.
In serial studies of multiple sclerosis lesions, reductions in magnetization transfer ratio (MTR) are thought to be due to demyelination and axonal loss, with later rises due to remyelination. This study followed serial changes in MTR in acute optic neuritis in combination with clinical and electrophysiological measurements to determine if the MTR changes over time mirror the picture in multiple sclerosis lesions, further validating MTR as a marker of tissue integrity. Twenty-nine patients were recruited who had acute optic neuritis for a median of 13 days (range 7-24 days) since the onset of visual symptoms. A clinical examination and measurement of visual evoked potentials (VEP) was performed on each patient. Their optic nerves were imaged with a fat-saturated fast spin echo (FSE) sequence and a magnetization transfer sequence. Twenty-one had multiple subsequent examinations over the course of 1 year. In addition, 27 control subjects had their optic nerves imaged up to three times over 1 year. A blinded observer segmented the optic nerves from the MTR maps. Lesions were defined on the acute FSE images and, from the coordinates, the ratio of mean lesion MTR : healthy nerve MTR (lesion ratio) was calculated for each dataset. The time-averaged mean MTR in control optic nerves was 47.7 per cent units (pu). In diseased optic nerves, baseline mean MTR was 47.3 pu, with a mean lesion ratio of 0.98. The diseased optic nerve MTR and lesion ratio declined over time with a nadir at about 240 days at a mean MTR value of 44.2 pu and mean lesion ratio of 0.91. Subsequently, diseased optic nerve MTR appeared to rise; after 1 year the diseased optic nerve mean MTR was 45.1 pu (mean lesion ratio 0.93), although the difference was not significant compared with the nadir value. For each 0.01 increase in time-averaged lesion ratio logMAR visual acuity recovery improved by 0.03 (95% CI, 0.002, 0.08, P = 0.02). Time-averaged VEP central field latency was shorter by 6.1 ms (95% CI 1.5, 10.7, P = 0.012) per 1 pu rise in time-averaged diseased optic nerve MTR. The early fall in diseased optic nerve MTR is consistent with demyelination and Wallerian degeneration of transected axons. The late nadir compared with studies of multiple sclerosis lesions may have been due to slow clearance of myelin debris. Remyelination may have influenced subsequent MTR changes. The observations support using MTR to monitor symptomatic demyelinating lesions.
Acute Disease↗
Cervical spinal cord MTR histogram analysis in multiple sclerosis using a 3D acquisition and a B-spline active surface segmentation technique.
The application of a three-dimensional magnetization transfer (MT) sequence and B-spline active surface segmentation method to produce MT histograms of the cervical spinal cord in a pilot study of controls and multiple sclerosis (MS) patients is presented. Subjects' cervical spinal cords were imaged with (a) a volume-acquired inversion-prepared fast spoiled gradient echo sequence and (b) a volume-acquired noninversion-prepared fast spoiled gradient echo MT sequence. The images were segmented using the B spline active surface technique and MT histograms were produced from the MT images. The method was sensitive enough to detect differences between seven MS patients and 10 controls in mean MT ratio (42.4 pu versus 44.0 pu, p = 0.03) and peak location (45.2 versus 46.8, p = 0.03). The spinal cord volumes obtained from the two sequences were associated with each other (parameter estimate 0.972, 95% confidence intervals 0.742, 1.202, p < 0.001).
Adult↗
Corticosteroids do not prevent optic nerve atrophy following optic neuritis.
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Adult↗
Management of acute optic neuritis.
Optic neuritis is a common condition that causes reversible loss of vision. It can be clinically isolated or can arise as one of the manifestations of multiple sclerosis. Occasional cases are due to other causes, and in these instances management can differ radically. The treatment of optic neuritis has been investigated in several trials, the results of which have shown that corticosteroids speed up the recovery of vision without affecting the final visual outcome. Other aspects of management, however, are controversial, and there is uncertainty about when to investigate and when to treat the condition. Here we review the diagnostic features of optic neuritis, its differential diagnosis, and give practical guidance about management of patients. The condition's association with multiple sclerosis will be considered in the light of studies that define the risk for development of multiple sclerosis and with respect to results of trials of disease-modifying drugs in these individuals.
Adrenal Cortex Hormones↗
Quantification of spinal cord atrophy from magnetic resonance images via a B-spline active surface model.
A method is presented that aims at segmenting and measuring the surface of the spinal cord from MR images in order to detect and quantify atrophy. A semiautomatic segmentation with very little intervention from an operator is proposed. It is based on the optimization of a B-spline active surface. The method allows for the computation of orthogonal cross-sections at any level along the cord, from which measurements are derived, such as cross-sectional area or curvature. An evaluation of the accuracy and reproducibility of the method is presented.
Atrophy↗
Continuing optic nerve atrophy following optic neuritis: a serial MRI study.
To investigate optic neuritis as a model for atrophy in multiple sclerosis (MS) lesions we performed serial magnetic resonance imaging (MRI) on 10 patients with a history of optic neuritis using a fat saturated short-echo fast fluid-attenuated inversion recovery (sTE fFLAIR) sequence. The first study was performed a median of 19.5 months after the onset of optic neuritis and the second 1 year later. Using a computer-assisted contouring technique, a blinded observer calculated the mean area of the intro-orbital optic nerves. The mean area of affected optic nerves decreased over 1 year by 0.9 mm2 from 11.1 to 10.2 mm2 (p = 0.01). Poor visual acuity and decreased visual-evoked potential (VEP) amplitude were associated with atrophy. These findings suggest that atrophy is a feature of focal demyelinating lesions, it may evolve over several years, and may have functional significance. Optic neuritis provides a model to study the effect of inflammatory demyelination through the ability to accurately measure visual function and to visualize and measure the optic nerves using magnetic resonance imaging.
Adult↗
Infratentorial hypointense lesion volume on T1-weighted magnetic resonance imaging correlates with disability in patients with chronic cerebellar ataxia due to multiple sclerosis.
In multiple sclerosis (MS), hypointense lesions on T1-weighted magnetic resonance imaging are thought to represent areas of tissue disruption and axonal loss. In previous studies of MS patients, infratentorial T1 hypointense lesions were found to be rare. In MS patients selected to have chronic cerebellar ataxia, we have determined the extent of infratentorial T1 hypointense lesions and their relationship with disability. We recruited nine patients with chronic cerebellar ataxia due to MS. An expanded disability status scale (EDSS) assessment was performed on each. The patients' brains were then imaged with axial-oblique dual-echo fast spin-echo and contrast-enhanced T1-weighted conventional spin-echo sequences. The number and total volume of infratentorial high-signal lesions on T2-weighted images and infratentorial hypointense lesions on T1-weighted images were calculated by a blinded observer using a computer-assisted contouring technique. A total of 96 infratentorial high-signal lesions were present, of which 62 (64.6%) appeared isointense and 34 (35.4%) hypointense with respect to the surrounding brain substance on the T1-weighted images. There was a median of 3 (range 0-10) and median volume of 0.43 ml (range 0-0.85 ml) infratentorial T1 hypointense lesions per patient. The EDSS score correlated with both the number (r=0.68, p=0.043) and the volume per patient (r=0.89, p=0.001) of infratentorial T1 hypointense but not T2 high-signal lesions. Infratentorial T1 hypointense lesions are often seen in patients with MS and chronic cerebellar ataxia. They may play a significant role in the disability suffered by these patients.
Adolescent↗
Detection of optic nerve atrophy following a single episode of unilateral optic neuritis by MRI using a fat-saturated short-echo fast FLAIR sequence.
We describe an MRI technique for quantifying optic nerve atrophy resulting from a single episode of unilateral optic neuritis. We imaged 17 patients, with a median time since onset of optic neuritis of 21 months (range 3-81 months), using a coronal-oblique fat-saturated short-echo fast fluid-attenuated inversion-recovery (sTE fFLAIR) sequence. The mean cross-sectional area of the intraorbital portion of the optic nerves was calculated by a blinded observer from five consecutive 3 mm slices from the orbital apex forwards using a semiautomated contouring technique and compared with data from 16 controls. The mean optic nerve area was 11.2 mm2 in the affected eye of the patients, 12.9 mm2 in the contralateral eye (P = 0.006 compared to the affected eye) and 12.8 mm2 in controls (P = 0.03 compared to the affected eyes). There was a significant negative correlation between disease duration and the size of the affected optic nerve (r = -0.59, P = 0.012). The measurement coefficient of variation was 4.8%. The sTE fFLAIR sequence enables measurement of optic nerve area with sufficient reproducibility to show optic nerve atrophy following a single episode of unilateral optic neuritis. The correlation of increasing optic nerve atrophy with disease duration would be consistent with ongoing axonal loss in a persistently demyelinated lesion, or Wallerian degeneration following axonal damage during the acute inflammatory phase.
Adult↗
How broad is the phenotype of Hallervorden-Spatz disease?
Magnetic resonance imaging (MRI) has enabled ante mortem diagnosis of Hallervorden Spatz disease (HSD). Childhood-onset cases are the most common type and usually present with progressive dystonia and dementia. The duration of illness is 15 to 20 years, leading to death. Presentation in adulthood and infancy have also been reported, however again the progression is usually inexorable. We present a 30-year-old woman who developed cognitive and motor developmental delay from the age of 8 months. There was further cognitive decline in her late teenage years with seizures and then more recent motor decline with dystonia. The imaging appearance was of iron deposition in the globus pallidus and substantia nigra leading to a diagnosis of HSD. The increased availability of MRI has allowed more cases of HSD to be diagnosed in life but as our case illustrates classification of the disease may need to be further examined.
Adult↗
Imaging of the spine in multiple sclerosis.
The spinal cord is a common site of involvement in multiple sclerosis (MS), and a major cause of the disability suffered by MS patients. High quality MR imaging of the spinal cord is therefore important for diagnosis and research. Imaging of the spine, however, presents many technical difficulties because of the small size of the spinal cord and the potential for artifacts. This article discusses technical difficulties such as pulse sequences, the use of newer imaging techniques, and the application of spinal MR imaging in clinical settings. Major studies are underway involving spinal cord imaging, and clinical trials of disease-modifying agents are beginning to include spinal cord imaging, especially measurements of atrophy, as part of their protocols. In clinical practice, spinal cord imaging is essential for ruling out other causes of myelopathies, particularly spinal cord compression, and can help in the diagnosis of MS when brain imaging is normal, or in older individuals in whom findings in the brain are less specific.
Artifacts↗
Posstreptococcal neuropathy.
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Adolescent↗
Syncope, the head ruling the heart.
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Craniopharyngioma↗