Biomedical subjects
Publications and source records attributed to G T Liu.
Three children with acute lymphoblastic leukemia developed altered mental status, headaches, seizures, and visual changes associated with reversible posterior cerebral changes on MRI. These clinical and radiologic findings were consistent with the reversible posterior leukoencephalopathy syndrome, which has not been widely recognized in this setting.
We describe a case of an adult born in the United States who had subacute sclerosing panencephalitis (SSPE). We discuss the possibility that the patient contracted subclinical measles during the 1989-1991 measles epidemic in the United States.
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PURPOSE: Although it is known that the damage to anterior striate cortex results in temporal peripheral visual field loss of the contralateral eye in patients with cerebral visual disturbance, the monocularity of anterior striate cortex has not been demonstrated in normal living humans. The aim of this study was to investigate whether this could be shown noninvasively using functional magnetic resonance imaging of the human visual cortex. METHODS: Eleven normal volunteers were studied with functional magnetic resonance imaging during alternating monocular visual stimulation using a 1.5 Tesla scanner. The data were motion corrected and spatially normalized to the standard brain. The monocular activation of the visual cortex was compared with the activation by the other eye. RESULTS: In the individual data analysis, contralateral eye dominance was always observed in the anterior striate cortex. In the group analysis from 11 subjects, the area with contralateral eye dominance was found in the most anterior part of primary visual cortex where the calcarine fissure merged with the parieto-occipital sulcus. CONCLUSIONS: This study shows that the contralateral eye dominance of anterior striate cortex can be detected noninvasively with functional magnetic resonance imaging during monocular visual stimulation. The finding confirms that the anterior striate cortex, where the monocular temporal crescent is represented, is primarily monocular, but the fact that greatest density of retinal ganglion cells and photoreceptors is in the nasal hemiretina must also be taken into account when interpreting these results.
Functional MRI techniques were used to map the position of visual cortex in an awake and a sedated child with congenital anomalies of the posterior hemispheres. In one subject with cortical heterotopia, an activated cortex was found distinct from the structurally abnormal area detected on conventional MRI. In a sedated patient with holoprosencephaly, activated cortical areas in the posterior-medial portions of the hemispheres were identified. This study demonstrates the utility of functional MRI in such patients, both awake and sedated.
OBJECTIVE: To describe the neuro-ophthalmic findings in patients with orbital drainage from cerebral arteriovenous malformations (AVMs). METHODS: We reviewed the records of 100 consecutive adult patients with cerebral AVMs who presented to our institution during a 4-year period. All patients with orbital drainage were identified, and their neuro-ophthalmic evaluations were reviewed. RESULTS: Three patients (3%) were identified with orbital drainage from a cerebral AVM. The first patient presented with typical chiasmal syndrome (reduced visual acuity, bitemporal hemianopia, and optic atrophy). Magnetic resonance imaging demonstrated a large left temporal and parietal lobe AVM with compression of the chiasm between a large pituitary gland and a markedly enlarged carotid artery. The second patient presented with headaches and postural monocular transient visual obscurations. Examination revealed normal visual function with minimal orbital congestion and asymmetrical disc edema, which was worse in the left eye. Magnetic resonance imaging revealed a large right parietal and occipital lobe AVM without mass effect or hemorrhage and an enlarged left superior ophthalmic vein. The third patient had no visual symptoms and a normal neuro-ophthalmic examination; a right parietal lobe AVM was discovered during an examination for the cause of headaches. CONCLUSION: Orbital drainage from cerebral AVMs is rare. Manifestations may include anterior visual pathway compression, dilated conjunctival veins, orbital congestion, and asymmetrical disc swelling.
The authors studied six patients with brainstem ocular motility deficits with 4.0 Tesla (T) magnetic resonance imaging to investigate whether a higher field strength would produce superior images compared with 1.5T. In four patients whose lesions were evident on 1.5T, the increased signal-to-noise achieved with 4.0T allowed for better resolution at 1-mm slice thickness than was achieved at the standard 5-mm slice thickness with 1.5T. In the two patients with unremarkable 1.5T scan results, 4.0T also failed to demonstrate a lesion. Therefore, 4.0T imaging has superior resolution to 1.5T imaging and can provide more detailed images of lesions identified by 1.5T.
AIM: This study was designed to test the ability of a portable computer driven, head mounted visual field testing system to perform automated perimetry on patients at their bedside and to compare these results with the "gold standard" for bedside examinations, confrontation visual fields. METHODS: The Kasha visual field system is a portable automated perimeter which utilises a virtual reality headset. 37 neurosurgery patients were examined at their bedside with a central 24 degree suprathreshold testing strategy after confrontation visual field testing. The patterns of visual field defects were categorised and compared with the results of confrontation testing. RESULTS: A total of 42 field examinations were completed on 37 patients, and the average testing time for both eyes was 4.8 minutes with the perimetry system. Each of the 11 fields (100%) classified with defects on confrontation testing was similarly categorised on head mounted perimetry. 26 out of 31 (84%) visual fields were normal on both confrontation and perimetry testing, while five out of the 31 fields (16%) which were full on confrontation had visual field defects identified by head mounted perimetry. CONCLUSION: The head mounted, automated perimetry system proved easily portable and convenient for examining neurosurgical patients at their bedside in the perioperative period. The device demonstrated equal sensitivity to confrontation visual field testing methods in detecting field defects and offers the advantage of standardised, quantifiable testing with graphic results for follow up examinations.
BACKGROUND AND PURPOSE: Functional MR imaging studies of the brain should be interpreted in the context of their reproducibility. We assessed the reproducibility of visual activation measured by functional MR imaging and analyzed the effect of image transformation to standard space. METHODS: Seven healthy volunteers were studied twice with echo-planner functional MR imaging at 1.5 T during visual stimulation. The studies were separated by an interval of 2 to 7 days. Functional images were analyzed after spatial normalization to the space described by Talairach and Tournoux and/or after coregistration of the images of the second study with the images of the first study. The number of active voxels for each study was determined at three thresholds. In addition, the change in the center of the mass of activation, the mean change in signal intensity, and the mean t value within the activated area were measured. These reproducibility indexes were calculated for the spatially normalized and nonnormalized data for each subject. RESULTS: Variations in visual activation were observed between the two studies in the same individual as well as across subjects. There was no evidence of an effect from image transformation on reproducibility on any of the measures. CONCLUSION: Our findings show that the reproducibility of activation in functional MR imaging may be much more variable across subjects than suggested in previous studies. The use of different types of image transformation (coregistration, spatial normalization) does not significantly affect the reproducibility of visual activation.
Although activation of the lateral geniculate nucleus has been detected by functional magnetic resonance imaging with magnetic field strengths higher than 2.0 Tesla, there have been no reports of functional magnetic resonance imaging of the lateral geniculate nucleus with the more widely available 1.5 Tesla scanner. The authors used functional magnetic resonance imaging techniques at 1.5 Tesla to detect lateral geniculate nucleus activation in five of seven healthy subjects. This study shows that visual activation of the lateral geniculate nucleus can be obtained with functional magnetic resonance imaging using conventional 1.5 Tesla scanners.
The authors describe five patients with trochlear nerve palsy and MS to characterize this rare association. In two patients, trochlear nerve palsy was the initial clinical manifestation of MS. In the other three patients, this sign occurred after previous neurologic events. MRI did not identify a lesion of the fourth nerve nucleus or fascicle. Ophthalmoplegia resolved within 2 months in four of the five patients. A reason this association is rare is that the fascicular course of the trochlear nerve is exposed to little myelin.
The relation between obesity and age in children with idiopathic intracranial hypertension (pseudotumor cerebri) has remained uncertain. The authors reviewed the records of 45 consecutive children with newly diagnosed idiopathic intracranial hypertension seen at two medical centers. Forty-three percent of patients aged 3 to 11 years were obese, whereas 81% of those in the 12- to 14-year age group and 91% of those in the 15- to 17-year age group met criteria for obesity (p = 0.01). Younger children with idiopathic intracranial hypertension are less likely to be obese than are older children or adults.
PURPOSE: To report the occurrence of acquired Brown syndrome and associated magnetic resonance imaging findings in a patient with psoriasis. METHODS: A 42-year-old woman with a history of psoriasis developed pain, double vision, and limited elevation of her left eye in adduction. An orbital magnetic resonance image with gadolinium enhancement was obtained. RESULTS: Orbital magnetic resonance image disclosed abnormal enhancement of the left trochlea/tendon complex. The patient's symptoms resolved with corticosteroid therapy. CONCLUSIONS: Acquired Brown syndrome may be associated with psoriasis. The inflammation of the trochlea/tendon complex that can cause acquired Brown syndrome can be demonstrated on magnetic resonance image.
The causes of sixth nerve palsies in 75 children, all of whom had undergone modern neuroimaging, were reviewed. Neoplasms or their neurosurgical removal was the most common cause (n = 34 [45%]); elevated intracranial pressure (nontumor) (15%), traumatic (12%), congenital (11%), inflammatory (7%), miscellaneous (5%), and idiopathic (5%) causes represented other categories but were less commonly present. Isolated sixth nerve palsies were relatively uncommon (9%). On the basis of the relatively high risk of neoplasm, the authors suggest neuroimaging early in the clinical course of children with sixth nerve palsies, even if the palsy is isolated.
Patients with Ollier's disease (multiple skeletal enchondromas) and Maffucci's syndrome (multiple enchondromas associated with subcutaneous hemangiomas) may develop skull base chondrosarcomas or low-grade astrocytomas as a delayed consequence of these disorders. We report three patients with Ollier's disease and Maffucci's syndrome who had diplopia as the initial manifestation of intracranial tumors. Since patients with Maffucci's syndrome and Ollier's disease are at risk for the delayed development of brain and systemic neoplasms, neuroophthalmologists must be aware of the need for long-term surveillance in patients affected by these conditions.
Comatose patients are unresponsive to all external stimuli, noxious or otherwise. Neuro-ophthalmic techniques are paramount in the neurologic assessment of comatose patients, especially with regard to brain stem localization and diagnosis. Examination of the pupils, fundi, and corneal reflexes are all helpful; however, the ocular motility examination is especially important because the pathways governing ocular motility traverse the entire brain stem, so pathology in this region often produces recognizable eye movement abnormalities. Conversely, if the eye movements are all normal, it is likely that the entire brain stem is normal. This article details the pupillary, eye movement, and funduscopic abnormalities in coma.
The herbicide-resistant EPSPs (5-enolpyruvylshikimate-3-phosphate synthase) gene was transformed into about 1,000 young spikes and 800 young embryos of wheat variety, Jinghua 1, with gene gun. Thirty-eight and four regenerated plants were obtained respectively screened with glyphosate. All regenerated plants were analysed by PCR and/or Southern blotting. The results indicated that EPSPs gene was integrated stably into the genome of Jinghua 1, and some of the transformants showed fertile. So herbicide-resistant EPSPs gene could be used as selective marker in the transformation of monocotyledon cereal crops, such as wheat.
In 1904 and 1905, respectively, William Campbell Posey and William Spiller both described the case of a patient with progressive ophthalmoparesis and imbalance that has come to be regarded as the earliest report of progressive supranuclear palsy. No autopsy was thought to have been performed on this patient. In this report, we review the clinical history provided by Posey and Spiller. We also report on the subsequent autopsy of their patient, which was performed by Spiller in 1906. The chief finding was a tumor involving the right cerebral peduncle and periaqueductal area. The autopsy findings prove conclusively that the patient described by Spiller and Posey had a midbrain neoplasm and not progressive supranuclear palsy.