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Biomedical subjects

W W Orrison

Publications and source records attributed to W W Orrison.

At least 19 recordsLinked to original sources
PubMed1999

Magnetic source imaging in stereotactic and functional neurosurgery.

Magnetic source imaging (MSI) combines the unique spatial and temporal functional accuracy of magnetoencephalography (MEG) with the anatomic and pathologic detail of magnetic resonance (MR). This relatively new method of evaluating brain function provides a preoperative mapping of brain function and brain structure by integrating the functional information of MEG with the structural information of MR. This results in data on actual neuronal interactions in clinical patients. The temporal and spatial accuracy of the MEG data, combined with the anatomic and pathologic specificity of MRI, results in the magnetic source image, which offers accurate knowledge of cortical functional organization, and is important in the surgical treatment of brain neoplasms, vascular malformations, and epilepsy. MSI allows the tracking of neuronal activity on the scale of milliseconds with millimeter accuracy, and continues to lead to new understanding of many functional brain disorders.

Action Potentials↗
PubMed1999

Magnetoencephalographic patterns of epileptiform activity in children with regressive autism spectrum disorders.

BACKGROUND: One-third of children diagnosed with autism spectrum disorders (ASDs) are reported to have had normal early development followed by an autistic regression between the ages of 2 and 3 years. This clinical profile partly parallels that seen in Landau-Kleffner syndrome (LKS), an acquired language disorder (aphasia) believed to be caused by epileptiform activity. Given the additional observation that one-third of autistic children experience one or more seizures by adolescence, epileptiform activity may play a causal role in some cases of autism. OBJECTIVE: To compare and contrast patterns of epileptiform activity in children with autistic regressions versus classic LKS to determine if there is neurobiological overlap between these conditions. It was hypothesized that many children with regressive ASDs would show epileptiform activity in a multifocal pattern that includes the same brain regions implicated in LKS. DESIGN: Magnetoencephalography (MEG), a noninvasive method for identifying zones of abnormal brain electrophysiology, was used to evaluate patterns of epileptiform activity during stage III sleep in 6 children with classic LKS and 50 children with regressive ASDs with onset between 20 and 36 months of age (16 with autism and 34 with pervasive developmental disorder-not otherwise specified). Whereas 5 of the 6 children with LKS had been previously diagnosed with complex-partial seizures, a clinical seizure disorder had been diagnosed for only 15 of the 50 ASD children. However, all the children in this study had been reported to occasionally demonstrate unusual behaviors (eg, rapid blinking, holding of the hands to the ears, unprovoked crying episodes, and/or brief staring spells) which, if exhibited by a normal child, might be interpreted as indicative of a subclinical epileptiform condition. MEG data were compared with simultaneously recorded electroencephalography (EEG) data, and with data from previous 1-hour and/or 24-hour clinical EEG, when available. Multiple-dipole, spatiotemporal modeling was used to identify sites of origin and propagation for epileptiform transients. RESULTS: The MEG of all children with LKS showed primary or secondary epileptiform involvement of the left intra/perisylvian region, with all but 1 child showing additional involvement of the right sylvian region. In all cases of LKS, independent epileptiform activity beyond the sylvian region was absent, although propagation of activity to frontal or parietal regions was seen occasionally. MEG identified epileptiform activity in 41 of the 50 (82%) children with ASDs. In contrast, simultaneous EEG revealed epileptiform activity in only 68%. When epileptiform activity was present in the ASDs, the same intra/perisylvian regions seen to be epileptiform in LKS were active in 85% of the cases. Whereas primary activity outside of the sylvian regions was not seen for any of the children with LKS, 75% of the ASD children with epileptiform activity demonstrated additional nonsylvian zones of independent epileptiform activity. Despite the multifocal nature of the epileptiform activity in the ASDs, neurosurgical intervention aimed at control has lead to a reduction of autistic features and improvement in language skills in 12 of 18 cases. CONCLUSIONS: This study demonstrates that there is a subset of children with ASDs who demonstrate clinically relevant epileptiform activity during slow-wave sleep, and that this activity may be present even in the absence of a clinical seizure disorder. MEG showed significantly greater sensitivity to this epileptiform activity than simultaneous EEG, 1-hour clinical EEG, and 24-hour clinical EEG. The multifocal epileptiform pattern identified by MEG in the ASDs typically includes the same perisylvian brain regions identified as abnormal in LKS. When epileptiform activity is present in the ASDs, therapeutic strategies (antiepileptic drugs, steroids, and even neurosurgery) aimed at its control can lead to a significa

Autistic Disorder↗
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↗
PubMed1999

Neuromagnetic assessment of pathophysiologic brain activity induced by minor head trauma.

BACKGROUND AND PURPOSE: Patients with mild traumatic brain injury (TBI) often show significant neuropsychological dysfunction despite the absence of abnormalities on traditional neuroradiologic examinations or EEG. Our objective was to determine if magnetic source imaging (MSI), using a combination of MR imaging and magnetoencephalography (MEG), is more sensitive than EEG and MR imaging in providing objective evidence of minor brain injury. METHODS: Four subject groups were evaluated with MR, MSI, and EEG. Group A consisted of 20 neurologically normal control subjects without histories of head trauma. Group B consisted of 10 subjects with histories of mild head trauma but complete recovery. Group C consisted of 20 subjects with histories of mild head injury and persistent postconcussive symptoms. The 15 subjects included in group D underwent repeat examinations at an interval of 2 to 4 months. RESULTS: No MR abnormalities were seen in the normal control group or the asymptomatic group, but five (20%) of the patients with persistent postconcussive symptoms had abnormal MR findings. EEG was abnormal for one subject (5%) from the normal control group, one (10%) from the asymptomatic group, and five (20%) from the group with persistent postconcussive symptoms. MSI was abnormal for one subject (5%) from the normal control group, one (10%) from the asymptomatic group, and 13 (65%) from the group with persistent postconcussive symptoms. There was a direct correlation between symptom resolution and MSI findings for the symptomatic head trauma group. CONCLUSION: MSI indicated brain dysfunction in significantly more patients with postconcussive symptoms than either EEG or MR imaging (P < .01). The presence of excessive abnormal low-frequency magnetic activity provides objective evidence of brain injury in patients with postconcussive syndromes and correlates well with the degree of symptomatic recovery.

Adolescent↗
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↗