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D J Mikulis

Publications and source records attributed to D J Mikulis.

18 recordsLinked to original sources
PubMed1997

A longitudinal magnetic resonance imaging study of brain changes in adolescents with anorexia nervosa.

OBJECTIVE: To assess whether the cerebral gray and white matter volume deficits described in patients with anorexia nervosa (AN) are fully reversible with weight rehabilitation. DESIGN: A prospective cohort study using magnetic resonance imaging to examine the brains of female adolescents after weight recovery from AN. SETTING: An adolescent eating disorder program located in a tertiary care children's hospital. PARTICIPANTS: Of 13 patients who underwent a previous magnetic resonance imaging study at a low weight, 6 patients were weight recovered and underwent rescanning. All brain measures were corrected for the effects of intracranial volume and age, based on a regression analysis of a group of 34 healthy female control subjects. Scans from the patients with AN were also compared with scans from an age-matched subset of 16 healthy female controls. MAIN OUTCOME MEASURES: White matter volumes, gray matter volumes, and cerebrospinal fluid volumes in the weight-recovered AN group. RESULTS: Quantitative analysis showed that white matter and ventricular cerebrospinal fluid volumes changed significantly (P = .03 for both) on weight recovery from AN. The weight-recovered patients had significant gray matter volume deficits (P = .01) and elevated cerebrospinal fluid volumes (P = .005) compared with those of the age-matched controls. They no longer had significant (P = .30) white matter volume deficits. CONCLUSION: The finding of persistent gray matter volume deficits in patients who have recovered their weight after AN suggests an irreversible component to the structural brain changes associated with AN, in addition to a component that resolves on weight recovery.

Adolescent↗
PubMed1997

Cerebral gray matter volume deficits after weight recovery from anorexia nervosa.

BACKGROUND: Structural changes have been observed in the brains of low-weight patients with anorexia nervosa (AN), including increased cerebrospinal fluid (CSF) volumes and decreased gray matter and white matter volumes. We hypothesized that subjects who are weight-recovered from AN would show elevated CSF volumes and reduced gray matter volumes compared with controls. METHODS: We used magnetic resonance imaging to compare the brains of 12 subjects who are weight-recovered from AN (time since weight recovery, 1-23 years) with those of 18 healthy control subjects and 13 low-weight patients with AN. Axial, dual-echo scans of the whole brain were segmented into gray matter, white matter, and CSF compartments by means of a computerized volumetric approach. Brain measures were corrected for the significant effects of intracranial volume and age, based on regression analysis of a larger group of 30 healthy female controls. RESULTS: Tests showed that the weight-recovered group had significantly greater CSF volumes and smaller gray matter volumes than the control group. By comparison with low-weight patients, the weight-recovered subjects had significantly smaller CSF volumes and significantly larger gray matter and white matter volumes. In the weight-recovered group, neither the CSF elevations nor gray matter deficits were correlated with the length of time since weight recovery. CONCLUSIONS: The persistent gray matter volume deficits in subjects who are weight-recovered from AN suggest that there may be an irreversible component to the brain changes associated with the illness. The neuropathological features of this irreversible component have yet to be characterized.

Adolescent↗
PubMed1997

Functional magnetic resonance imaging: a potential tool for the evaluation of spinal cord stimulation: technical case report.

OBJECTIVE AND IMPORTANCE: The management of chronic pain of spinal origin continues to represent a challenge for neurosurgeons. Spinal cord stimulation for chronic intractable pain is an effective therapy in approximately 50% of patients. The present study uses a novel imaging approach, functional magnetic resonance imaging (fMRI), to examine the central effects of spinal cord stimulation. CLINICAL PRESENTATION: Three patients, each with a chronic history of intractable pain, were treated at the Toronto Hospital with a trial of dorsal column stimulation (DCS). For all patients, significant improvement in pain symptoms was achieved with DCS. INTERVENTION: fMRI on a 1.5-T conventional magnetic resonance system was used to study the effects of DCS in these patients. Images were collected while the stimulator was activated and deactivated. CONCLUSION: This report is the first to describe the cerebral effects of exogenous spinal cord stimulation with fMRI. fMRI allows for the objective examination of the effects of DCS and may provide an objective means of evaluating the efficacy of DCS as a therapy for intractable pain of spinal origin.

Adult↗
PubMed1997

Functional MRI of pain- and attention-related activations in the human cingulate cortex.

The aims of the study were to use functional magnetic resonance imaging (fMRI) to 1) locate pain-related regions in the anterior cingulate cortex (ACC) of normal human subjects and 2) determine whether each subject's pain-related activation is congruent with ACC regions involved in attention-demanding cognitive processes. Ten normal subjects underwent fMRI with a 1.5-T standard commercial MRI scanner. A conventional gradient echo technique was used to obtain data from a single 4-mm sagittal slice of the left ACC, approximately 3.5 mm from midline. For each subject, interleaved sets of 6 images were obtained during a pain task, an attention-demanding task, and at rest, for a total of 36 images per task. Pain of different intensities was evoked via electrical stimulation of the right median nerve. The attention-demanding task consisted of silent word generation (verbal fluency). Additional experiments obtained data from the right ACC. A pixel-by-pixel statistical analysis of task versus rest images was used to determine task-related activated regions. The pain task resulted in a 1.6-4.0% increase in mean signal intensity within a small region of the ACC. The exact location of this activation varied from subject to subject, but was typically in the posterior part of area 24. The signal intensity changes within this region correlated with pain intensity reported by the subject. The attention-demanding tasks increased the mean signal intensity by 1.3-3.3% in a region anterior and/or superior to the pain-related activation in each subject. The activated region was typically larger than the pain-related activation. In some cases this activation was at or superior to the ACC border, near the supplementary motor area. These regions did not show any pain-intensity-related activation. In one subject both right and left ACC were imaged, revealing bilateral ACC activation during the attention task but only contralateral pain-related activation. These findings shed light on pain- and attention-related cognitive processes. The results provide evidence for a region in the posterior part of the ACC that is involved in pain and a more anterior region involved in other attention-demanding cognitive tasks.

Adult↗
PubMed1996

Cerebral gray matter and white matter volume deficits in adolescent girls with anorexia nervosa.

OBJECTIVES: This study was undertaken to determine whether the increased cerebrospinal fluid (CSF) volumes found in anorexia nervosa (AN) are the result of differences in gray matter or white matter volumes or both. METHODS: Thirteen adolescent girls with AN who were receiving inpatient care at a tertiary-care university children's hospital and eight healthy female control subjects were studied by using magnetic resonance imaging. Images were processed by means of software developed to classify all pixels as either CSF, gray matter, or white matter. Pixels of each class were then summed across all sections. RESULTS: The AN group had larger total CSF volumes in association with deficits in both total gray matter and total white matter volumes. Lowest reported body mass index was inversely correlated with total CSF volume and positively correlated with total gray matter volume. Urinary free cortisol levels were positively correlated with total CSF volume and inversely correlated with central gray matter volume. CONCLUSIONS: These findings add support to the view that the brain abnormalities found in AN are in large part the result of the effects of the illness. The extent to which these differences in gray matter and white matter volumes are reversible with recovery remains to be established.

Adolescent↗
PubMed1996

Endurance-trained and untrained skeletal muscle bioenergetics observed with magnetic resonance spectroscopy.

Resting and submaximal isometric exercise 31P magnetic resonance spectroscopy (MRS) was carried out on 7 endurance-trained males (26.0 +/- 3 yrs) and 7 sedentary males (27.0 +/- 4 yrs). Spectral analysis provided peak areas of phosphocreatine (PCr), inorganic phosphate (Pi), adenosine triphosphate (ATP), and the chemical shift of Pi relative to PCr. The ratio of PCr/Pi was moderately lower during rest (preexercise p = .13, postexercise p = .18), and significantly higher during exercise (p < .05) in the trained subjects. Intracellular pH patterns were the same for both groups; a transient alkalosis was observed at the onset of exercise with a return to resting levels after 2 min. Differences suggest improved ATP resynthesis rate in the trained subjects during exercise. Intracellular pH changes can be attributed to the utilization of hydrogen ions that accompany PCr hydrolysis during work. The findings are congruent with previous reports indicating a superior oxidative capacity in trained skeletal muscle.

Adenosine Triphosphate↗
PubMed1995

fMRI of human somatosensory and cingulate cortex during painful electrical nerve stimulation.

Functional MRI (fMRI) can detect changes from resting levels of blood flow and oxygenation during task performance (i.e. activation). We used a simple electrical nerve stimulation technique together with fMRI to study pain process in the human cortex. Images of the primary somatosensory (SI) and cingulate cortex (Cg) were obtained from subjects during stimulation at painful and non-painful intensities. Stimuli that evoked non-painful tingling sensations activated the contralateral SI but not Cg. Stimuli that evoked painful sensations activated both the contralateral SI and Cg. These data indicate that fMRI can detect pain-related changes in SI and Cg evoked by electrical stimulation of peripheral nerves. These findings add to the evidence for a role of SI and Cg in human pain processes and provide a simple method of stimulus delivery for its study.

Adult↗
PubMed1995

Quantitation of articular cartilage using magnetic resonance imaging and three-dimensional reconstruction.

A quadrature knee coil was used in conjunction with a magnetic resonance imaging scanner for quantitation of test phantom volumes, ex vivo bovine cartilage thickness, and in vivo human articular cartilage volumes. Optimal magnetic resonance parameters were obtained by testing a series of spin-echo and gradient-echo pulse sequences to determine the sequence that provided the highest resolution of articular cartilage and best defined the cartilage interfaces with synovial fluid and subchondral bone. Extensive testing revealed that two sequences were required to define articular cartilage accurately: a spoiled gradient-echo sequence and a steady state free-precession sequence. Three-dimensional reconstruction and statistical analyses of test phantoms and of bovine and human cartilage images were performed. Differences between actual phantom volumes and three-dimensional measurements demonstrated that, as magnetic resonance slice thickness was increased, the measurement variability also increased (coefficient of variation ranging from 1.7 +/- 1.3% for 1.0 mm slice thickness to 22.7 +/- 1.9% for 3.0 mm slice thickness). When the phantom volume was greater than 1,800 mm3, the intraobserver, interobserver and interscan accuracies were greater than 97, 98, and 96%, respectively. This high degree of reproducibility pertained for the data on in vivo human cartilage data also. For experienced observers, the intraobserver and interobserver reproducibility were greater than 98 and 97%, respectively. The interscan reproducibility was greater than 98%. These data demonstrate that improved magnetic resonance pulse sequencing, in conjunction with three-dimensional reconstruction and measurement techniques, can accurately and reproducibly measure the volume of articular cartilage. Clinical application of this approach offers the potential for early diagnosis of osteoarthritis and for serial, noninvasive assessment of changes in articular cartilage volume in response to therapeutic modalities.

Adult↗
PubMed1994

Oscillatory motion of the normal cervical spinal cord.

PURPOSE: To determine the normal pattern of cervical spinal cord motion with measurement of cervical spinal cord velocity by means of phase-contrast magnetic resonance (MR) imaging. MATERIALS AND METHODS: Spinal cord velocity was measured in 11 healthy subjects with a modified gradient-echo pulse sequence on a conventional 1.5-T MR imaging system that generated phase images sensitive to slow motion. Prospective electrocardiogram gating was used to assess velocity as a function of the cardiac cycle. The accuracy of velocity measurements was estimated with images of a phantom moving at constant velocity. RESULTS: The cervical spinal cord moves with an oscillatory pattern in the craniocaudal direction. The maximum velocity (7.0 mm/sec +/- 1.4 [standard deviation]) in the caudal direction occurred approximately 109 msec +/- 20 after electrical cardiac systole. The maximum velocities in subsequent oscillations decreased toward zero before the next cardiac systole. CONCLUSION: The cervical spinal cord oscillates in a craniocaudal direction after each cardiac systole.

Adult↗
PubMed1992

Variance of the position of the cerebellar tonsils with age: preliminary report.

The position of the cerebellar tonsils relative to the foramen magnum was measured with sagittal magnetic resonance (MR) images in 221 patients aged 5 months to 89 years who were considered not to have disorders that would affect tonsillar position. All patients were grouped according to age. All measurements of the tonsils were obtained directly from the video console. Statistically significant (P less than .05) differences in tonsillar position were found between the 1st and 9th decades (P less than .001) and the 3rd and 9th decades (P less than .003) of life. An obvious trend existed: tonsillar ascent with increasing age. Therefore, the authors believe that a single reference standard that indicates the normal distance of the cerebellar tonsils from the foramen magnum is inappropriate unless age is considered. They suggest that the following distances below the foramen magnum (more than 2 standard deviations out of the normal range) be used as criteria for ectopia of the cerebellar tonsils: 1st decade of life, 6 mm; 2nd and 3rd decades, 5 mm; 4th to 8th decades, 4 mm; and 9th decade, 3 mm.

Adolescent↗
PubMed1991

The radiology of headache.

The patient who presents with a severe and acute headache should be evaluated radiographically with CT. The key diagnosis to make in this situation is hemorrhage, either subarachnoid or intraparenchymal. Computed tomography is more sensitive to acute hemorrhage than is MRI. When the patient is stable, MRI frequently contributes information to narrow the diagnostic possibilities, because vascular malformations and certain parenchymal lesions have a characteristic appearance on MRI. Hydrocephalus may also present acutely and is easily seen on CT or MRI. In a patient may show WMF and atrophy. The patient with trigeminal neuropathy may demonstrate central or peripheral lesions. In temporomandibular joint dysfunction, conventional tomography and MRI are frequently used. Magnetic resonance imaging shows excellent detail of the disk and surrounding soft tissues, whereas tomography better demonstrates bony changes. When a history of trauma is present, MRI may show a subacute subdural hematoma. These collections are easily seen on MRI, even when isodense on CT. Evidence of old shear injury is also well seen on MRI. Finally, neoplastic, inflammatory, congenital, and idiopathic sources of headache may be demonstrated by either MRI or CT, depending on presentation. MRI will generally show superior characterization.

Adult↗
PubMed1989

Wallerian degeneration after cerebral infarction: evaluation with sequential MR imaging.

The dynamic signal intensity changes at magnetic resonance (MR) imaging in active and chronic wallerian degeneration in the corticospinal tract were evaluated. Forty-three patients with wallerian degeneration seen on MR images after cerebral infarction were studied. When possible, patients with acute stroke were examined with MR imaging prospectively at the onset of symptoms and then at weekly intervals for several months. Focal infarction without distal axonal degeneration is demonstrated for the 1st month following onset of clinical symptoms. At 4 weeks, a well-defined band of hypointense signal appears on T2-weighted images in the topographic distribution of the corticospinal tract. After 10-14 weeks, the signal becomes permanently hyperintense. Over several years, accompanying ipsilateral brain stem shrinkage occurs. The dark signal intensity observed on T2-weighted images between 4 and 14 weeks is believed to result primarily from transitory increased lipid-protein ratio.

Adult↗
PubMed1986

Common carotid artery occlusion. Role of non-invasive and angiographic analysis.

Doppler and B-scan imaging, periorbital directional Doppler, and occuloplethysmography correctly identified common carotid occlusion in three of four consecutive patients with atherosclerosis. High-grade common carotid stenosis in the fourth patient could not be distinguished from occlusion on the non-invasive tests. Occlusion of the internal carotid artery in one patient and patency of that artery in the other three were evident non-invasively. Modified angiography agreed with non-invasive tests in each of three patients studied. Intra-arterial digital subtraction angiography in the fourth patient suggested but could not confirm patency of the internal carotid artery indicated by non-invasive criteria.

Carotid Arteries↗
PubMedDate not supplied

Phase-contrast imaging of the parotid region.

Standard T1- and T2-weighted spin-echo acquisitions were compared with T1- and T2-weighted phase-contrast techniques in a series of 10 consecutive patients with parotid masses to assess the role of phase-contrast methods in the evaluation of lesions in the parotid fossa. Greater tissue-lesion contrast was obtained with phase-contrast methods in nine of 10 cases, allowing improved lesion visualization; however, an increase in lesion detectability was not observed in this series. Standard MR imaging methods are sufficient for imaging the parotid region in most cases, but can be quite time-consuming. Recommended screening of the parotid fossa that optimizes tissue-lesion contrast, lesion detectability, and imaging time is performed by combining a standard T1-weighted acquisition with a T1- or T2-weighted phase-contrast acquisition. Selection of a T1- or T2-weighted phase-contrast acquisition is determined by the T1 characteristics of the lesion.

Humans↗