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W W Orrison

Publications and source records attributed to W W Orrison.

At least 19 recordsLinked to original sources
PubMed1999

Integration of preoperative and intraoperative functional brain mapping in a frameless stereotactic environment for lesions near eloquent cortex. Technical note.

The authors present a method of incorporating preoperative noninvasive functional brain mapping data into the frameless stereotactic magnetic resonance (MR) imaging dataset used for image-guided resection of brain lesions located near eloquent cortex. They report the use of functional (f)MR imaging and magnetic source (MS) imaging for preoperative mapping of eloquent cortex in difficult cases of brain tumor resection such as those in which there are large expansive masses or in which reoperations are required and the anatomy is distorted from prior treatments. To correlate methods of preoperative and intraoperative mapping localization directly, the authors have developed techniques of importing preoperative MS and fMR imaging data into an image-guided frameless stereotactic computer workstation. The data appear as a seamless overlay on the same preoperative volumetric MR imaging dataset used for stereotactic guidance during the operation. Intraoperatively identified functional locations mapped by cortical stimulation are recorded as digitally registered points. This approach should prove useful in assessing the accuracy and reliability of various preoperative functional brain mapping techniques.

Adult↗
PubMed1998

MR of extraocular muscles in chronic progressive external ophthalmoplegia.

PURPOSE: Our goal was to determine whether the extraocular muscles in patients with chronic progressive external ophthalmoplegia (CPEO) could be distinguished from those of age-matched control subjects by MR imaging. METHODS: Nine patients with CPEO and eight age-matched healthy control subjects were studied. The extraocular muscles of eight of the patients (16 eyes) and all the control subjects (16 eyes) were measured digitally. Images consisted of 1.5-mm contiguous sections acquired using a volume (three-dimensional) gradient-echo acquisition. In all, measurements were performed on 11 interpolated 1.0-mm coronal sections, five on each side of the muscle center. Only the medial, inferior, and lateral rectus muscles were evaluated. The superior rectus was omitted to avoid averaging problems with the superior ophthalmic vein and levator palpebrae muscle. The 11 sections were summed to obtain a volume measurement of the central portion of each muscle. RESULTS: The digitally measured extraocular muscles in the patients with CPEO had statistically significantly smaller volumes than those of the control subjects. The average muscle volumes for the patients with CPEO were 215 mm3 for the medial rectus, 202 mm3 for the inferior rectus, and 269 mm3 for the lateral rectus. The average extraocular muscle volumes for the control subjects were 366 mm3 for the medial rectus, 365 mm3 for the inferior rectus, and 425 mm3 for the lateral rectus. CONCLUSION: MR imaging can show small extraocular muscles in patients with CPEO, which may help to distinguish this disorder from other entities. Since denervated extraocular muscles do not readily atrophy, this MR sign would support a myogenic pathologic substrate for CPEO. Variation in the degree of extraocular muscle atrophy may simply reflect the length of time the mitochondrial defect and ophthalmoplegia have been present.

Adolescent↗
PubMed1997

Granulomatous amebic encephalitis caused by acanthamoeba.

Infections arising from free-living amebae are rare. They generally cause recognizable disease only in chronically ill, debilitated patients who are immune suppressed. Only about 70 cases of granulomatous amebic encephalitis have been reported. We present an unusual case of granulomatous encephalitis in a 35-year-old man. Neurologic examination and laboratory tests were inconclusive. CT demonstrated bilateral low-density areas with mild mass effect in the cortex and subcortical white matter, which showed increased signal on T2-weighted MRI. Craniotomy and brain biopsy revealed granulomatous encephalitis with acanthamoeba organisms. Though non-specific, imaging can support the diagnosis of amebic encephalitis and direct biopsy.

Acanthamoeba↗
PubMed1996

3M Mayneord Memorial Lecture: functional brain imaging--an overview.

Several methods can detect or infer the disruption of basic brain physiology; these methods include the techniques of computerized axial tomography, magnetic resonance imaging, positron emission tomography, single photon emission computed tomography, electroencephalography, magnetoencephalography, and magnetic resonance spectroscopy. Until recently any information on the actual function of the brain has been restricted to that deduced from the clinical examination, as most imaging methods have been limited to providing only anatomical references. In the past 10 years magnetic resonance has become a standard part of many neuroradiological practices. Tremendous advances in computed tomography have resulted in dramatic improvement in both image resolution and imaging times. During the 1990s, as interest shifts toward the analysis of brain function or dysfunction, the focus on the brain's electrical activity has resurged. Functional evaluation techniques, such as magnetoencephalography, began in the 1960s and early 1970s; sophistication in the technology has led to much shorter examination and analysis times, leading to further clinical utility. Magnetoencephalography, when combined with magnetic resonance images, forms a functional image of the brain, or magnetic source image. The advent of such methods for evaluating actual functional activity of the brain has resulted in new clinical applications for previous methods of brain imaging and the arrival of new clinical imaging modalities.

Brain↗
PubMed1996

Magnetic resonance imaging for the evaluation of patients with occult cervical spine injury.

Because it is often difficult to diagnose accurately the structurally intact cervical spine after acute trauma, a series of patients was evaluated with magnetic resonance (MR) imaging to assess its efficacy for the evaluation and clearance of the cervical spine in a trauma victim in the early posttrauma period. Ultralow-field MR imaging was used to evaluate 174 posttraumatic patients in whom physical findings indicated the potential for spine injury or minor radiographic findings indicated injury. This series includes only those patients who did not appear to harbor disruption of spinal integrity on the basis of a routine x-ray film. None had clinically obvious injury. Of the 174 patients, 62 (36%) had soft-tissue abnormalities identified by MR imaging, including disc interspace disruption in 27 patients (four with ventral and dorsal ligamentous injury, three with ventral ligamentous injury alone, 18 with dorsal ligamentous injury alone, and two without ventral or dorsal ligamentous injury). Isolated ligamentous injury was observed in 35 patients (eight with ventral and dorsal ligamentous injury, five with ventral ligamentous injury alone, and 22 with dorsal ligamentous injury alone). One patient underwent a surgical fusion procedure, 35 patients (including the one treated surgically) were placed in a cervical collar for at least 1 month, and 27 patients were placed in a thermoplastic Minerva jacket for at least 2 months. All had a satisfactory outcome without evidence of instability. The T2-weighted sagittal images were most useful in defining acute soft-tissue injury; axial images were of minimal assistance. Posttraumatic soft-tissue cervical spine injuries and disc herniations (most likely proexisting the trauma) are more common than expected. A negative MR image should be considered as confirmation of a negative or "cleared" subaxial cervical spine. Diagnostic and patient management algorithms may be appropriately tailored by this information. Thus, MR imaging is useful for early acute posttrauma assessment in a very select group of patients.

Adolescent↗
PubMed1996

Magnetoencephalographic assessment of spontaneous brain activity in schizophrenia.

Magnetoencephalography (MEG) offers an attractive alternative to electroencephalography (EEG) in the assessment of psychiatric patients. In this study, a whole-head biomagnetometer equipped with 122 super-cooled sensors was used to assess spontaneous neuromagnetic activity in 11 unmedicated schizophrenic patients and 8 schizophrenic patients medicated for more than 8 weeks with novel antipsychotics (5 of whom were initially studied as part of the unmedicated group). Ten normal (nonpsychiatric) controls were also examined. For each subject, 5 minutes of data were collected in an eyes-closed state. Data were visually inspected for gross MEG abnormalities, and average power spectra were calculated for the data at each sensor. No gross abnormalities were identified for control subjects. One unmedicated schizophrenic patient showed epileptiform sharp waves, and 4 showed abnormal slow waves. No gross MEG abnormalities were found for the medicated schizophrenic group (which included 3 patients who had previously shown slow waves in the unmedicated state). Spectral analyses showed that the schizophrenia patients demonstrated lower alpha power and peak frequency than controls. The data are interpreted within the context of previously reported magnetic resonance abnormalities of the thalamus.

Adult↗
PubMed1995

Comparison of functional magnetic resonance imaging with positron emission tomography and magnetoencephalography to identify the motor cortex in a patient with an arteriovenous malformation.

Alterations in gyral contour made it difficult to identify the motor cortex thought to be near an arteriovenous malformation (AVM) in a 24-year-old man considered for stereotactic radiosurgery. Functional imaging in three modalities was performed preoperatively to compare the reliability of localization using functional magnetic resonance imaging (fMRI) on a conventional scanner with positron emission tomography (PET) and magnetoencephalography (MEG). Similar tasks were used for each imaging modality in an attempt to activate and identify the sensory and motor cortex. Data from all three modalities converged for the sensory task, and fMRI and PET data converged for the motor task. The right hemisphere motor strip was localized adjacent and anterior to the AVM. These data were used in planning the radiosurgery isodose configuration to the AVM in order to reduce the irradiation of motor cortex parenchyma. A postoperative fMRI study was also performed using newer techniques to reduce head motion artifact and to improve signal-to-noise ratio. The data confirmed the conclusions derived from the preoperative evaluations. This study demonstrates how conventional MRI scanners can be used for functional studies of use in surgical planning.

Adult↗
PubMed1995

Angiographic pattern change in fibromuscular dysplasia. A case report.

Fibromuscular dysplasia (FMD) is an angiopathy that commonly affects the renal arteries but may affect other medium to large arteries, including the carotid artery. It has a variety of angiography appearances, the most common of which is a string-of-beads pattern consisting of a segment of alternating stenoses and dilatations. This case documents that these patterns are not necessarily fixed. An initial angiogram in a patient with neurologic symptoms shows a string-of-beads pattern in the carotid artery. Later, this pattern is seen to convert to a smooth tubular form on follow-up arteriography. FMD may present angiographically as a dynamic process.

Carotid Artery, Internal↗
PubMed1995

Pediatric magnetic source imaging.

Magnetic source imaging has changed the perspective of managing pediatric patients with epilepsy since its introduction into clinical imaging in the pediatric population. Magnetic source imaging can be important in understanding pediatric functional neuroanatomy and for epileptic surgery in children with intractable seizures. The use and efficacy of magnetic source imaging for surgical planning and patient management is demonstrated by case reports presented in this article.

Brain Mapping↗
PubMed1995

Spike and slow wave localization by magnetoencephalography.

At institutions where MEG is available, it is now considered a standard part of the diagnostic workup of most patients with epilepsy. Available data indicate that interictal MEG can be an effective tool for localization of the epileptic irritative zone, and in some cases it can even indicate the seizure onset site. Both spike and ALFMA examinations are clinically viable because of the availability of large-array systems. The current cost of acquiring MEG technology is high (greater than 2 million dollars), but recent technical developments should soon yield more cost-effective systems. It is anticipated that the increasing applicability of this technology to conditions beyond epilepsy (e.g., head trauma, ischemic disease, dementia, and psychiatric dysfunction) will soon render MEG a critical element in the general armamentarium of diagnostic procedures available to epileptologists, radiologists, neurologists, neurosurgeons, and psychiatrists.

Brain↗
PubMed1994

Methylmercury poisoning: long-term clinical, radiological, toxicological, and pathological studies of an affected family.

For 3 months in 1969 a family in the United States that included a pregnant mother consumed pork containing methylmercury. Children, aged 20, 13, and 8 years and a neonate, developed severe neurological signs. Twenty-two years later, the 2 oldest had cortical blindness or constricted visual fields, diminished hand proprioception, choreoathetosis, and attentional deficits. Magnetic resonance images showed tissue loss in the calcarine and parietal cortices and cerebellar folia. The youngest had quadriplegia, blindness, and severe mental retardation until their deaths. The brain of the 8-year-old who died at age 30 showed cortical atrophy, neuronal loss, and gliosis, most pronounced in the paracentral and parietooccipital regions. The total mercury level in formalin-fixed, left occipital cortex was 1,974 ng/gm as measured by atomic absorption. Regional brain mercury levels correlated with extent of brain damage. A control patient had 38.5 ng of mercury/gm in the occipital cortex. Systemic organs in the patient and a control subject had comparable mercury levels. In mercury-intoxicated rats, we found that only 5 to 10% of total brain mercury was lost by formalin fixation. Brain inorganic mercury in the patient ranged from 82 to 100%. Since inorganic mercury crosses the blood-brain barrier poorly, biotransformation of methyl to inorganic mercury may have occurred after methylmercury crossed the blood-brain barrier, accounting for its persistence in brain and causing part of the brain damage.

Adolescent↗