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Biomedical subjects

T A Yousry

Publications and source records attributed to T A Yousry.

At least 37 records · Page 2Linked to original sources
PubMed2001

Identification and anatomic description of the anterior choroidal artery by use of 3D-TOF source and 3D-CISS MR imaging.

BACKGROUND AND PURPOSE: The importance of the anterior choroidal artery (AChA) is related to its supply of crucial anatomic structures, such as the internal capsule. Angiographically, the AChA can be detected in 71% to 98% of patients, but as yet, its visibility on MR images has not been evaluated. Our goal was to assess the sensitivity of MR imaging in the identification of the AChA and its anatomic characteristics. METHODS: Twenty volunteers underwent MR imaging with a 3D time-of-flight (3D-TOF) sequence, 10 of them additionally with a 3D Fourier transformation constructive interference in steady state (3D-CISS) sequence. The MR angiographic source images and the 3D-CISS images were analyzed independently by two neuroradiologists, who evaluated the ability to identify the different segments of the AChA and the posterior communicating artery (PComA) according to a previously defined scoring system (0 = not identified, 1 = most probably identified, 2 = identified with certainty). Additionally, three patients were examined who had an arteriovenous malformation (AVM) supplied by the AChA. RESULTS: In the volunteers, the PComA was identified with certainty in 87.5% on 3D-TOF sequences and in 95% on 3D-CISS sequences; the AChA was identified with certainty in 92.5% on 3D-TOF sequences and in 90% on 3D-CISS sequences. 3D-CISS images showed additional anatomic information in six of 20 vessels. In the three patients, the enlarged AChA was identified with certainty on both imaging sequences. CONCLUSION: The AChA can be reliably identified using both 3D-CISS sequences and the source images of the 3D-TOF sequence. MR imaging can be used to assess and follow-up AChA-related disorders, especially AVMs.

Adult↗
PubMed2001

The motor cortex: anatomic substrates of function.

This article provides a firm foundation in the gross and microscopic anatomy of the motor cortex. It reviews the sites, Brodmann regions, normal function, and deficits associated with the primary motor cortex, supplementary motor area, presupplementary motor area, and the cingulate motor area in preparation for understanding the functional MR imaging studies that are reviewed in the later articles.

Brain Mapping↗
PubMed2001

Functional magnetic resonance imaging: factors modulating the cortical activation pattern of the motor system.

The use of functional MR imaging (fMRI), especially in a clinical setting, requires knowledge and control of the physiologic factors that can affect the hemodynamic response of the brain. In this article, the authors review the influence of elementary parameters of the motor system such as hemispheric dominance, rate, and force of action, and complexity of a paradigm in determining the cortical fMRI signal change.

Animals↗
PubMed2001

Functional magnetic resonance imaging of human olfaction.

Olfaction is our basic sense phylogenetically and embryologically. Little is known, however, about how the human brain encodes the quality of odors, odor-associated memories, and emotions. Olfactory information is projected from the olfactory bulb to the primary olfactory cortex, which is composed of the anterior olfactory nucleus, the olfactory tubercle, the piriform cortex, the amygdala, the periamygdaloid region, and the entorhinal cortex. From there, the primary olfactory cortex projects to secondary olfactory regions including the hippocampus, ventral striatum and pallidum, hypothalamus, thalamus, orbitofrontal cortex, agranular insular cortex, and cingulate gyrus. Functional MR studies using olfactory stimuli as paradigms show activation of many of these areas and can advance our understanding of odor perception in humans.

Adult↗
PubMed2001

Anatomic substrates of language: emphasizing speech.

This article reviews in detail the gross anatomy of the auditory and language areas, the present concepts of unimodal and multimodal association cortices, the classic model of language, problems with the classic model, and newer approaches to conceptualizing the structural interconnections that subserve audition and language.

Adult↗
PubMed2001

Cervical MR imaging in postural headache: MR signs and pathophysiological implications.

BACKGROUND AND PURPOSE: Postural headache most often occurs after lumbar puncture as post-lumbar puncture headache (PLPH) or, rarely, spontaneously as spontaneous intracranial hypotension headache (SIHH). In this prospective study, we used spinal MR imaging to determine the findings that would assist in the diagnosis of PLPH and SIHH and that would further our pathophysiological understanding of postural headache. METHODS: The study group consisted of 15 healthy volunteers and 20 patients with postural headache: nine with SIHH and 11 with PLPH. The craniocervical junction and the cervical spine were studied using T2-weighted fast spin-echo and T1-weighted spin-echo sequences in the axial and sagittal planes. Follow-up studies were performed in 13 patients. RESULTS: Dilatation of the anterior internal vertebral venous plexus was the most constant finding, present in 17 (85%) of 20 patients with postural headache. Spinal hygromas, whose location as subdural or epidural could not be exactly determined, were present in 14 patients (70%). A focal fluid collection was detected in the retrospinal region at the C1-C2 level in six patients with SIHH and in four patients with PLPH (50%). Tonsillar descent was detected in only one patient, and subtentorial hygroma in five patients. No abnormalities were found in the volunteers. CONCLUSION: The MR signs of dilatation of the venous plexus, presence of spinal hygromas, and presence of retrospinal fluid collections can help to establish the diagnosis of intracranial hypotension. They are probably the result of decreased CSF volume, with the retrospinal fluid collections being a transudate from the venous plexus rather than frank extravasation. Resolution of these signs parallels resolution of the headache.

Adult↗
PubMed2000

Hemifield visual motion stimulation: an example of interhemispheric crosstalk.

Coherent motion stimulation of the right or left visual hemifield was performed in nine healthy volunteers in order to investigate interhemispheric visuo-visual interaction by means of functional magnetic resonance imaging. The vertical edge of the motion pattern field was located 8 degrees distant from the fixation point to avoid stimulating the vertical meridian, which is represented retinotopically in both hemispheres. Bilateral activation was significant in the middle occipital gyrus (motion-sensitive middle temporal/middle superior temporal areas; BA 19/37). A negative signal change was found in the primary visual cortex including the lingual and fusiform gyri (BA 18/17) and the occipital white matter containing the optic radiation contralateral to the stimulated hemisphere. These data are most compatible with an interhemispheric transfer of visual motion information, most likely through the corpus callosum. Transcallosal transfer of visual motion information, evident as increases (BA 19/37) and decreases (BA 18/17) of the fMRI signals, may be functionally significant for the processing of motion perception.

Adult↗
PubMed2000

Assessment of posterior fossa damage in MS using MRI.

In multiple sclerosis (MS), brain stem and cerebellum are frequent sites of damage in clinically isolated syndromes at presentation and it is likely that lesions located in such structures can have an important impact on the development of disability in the definite forms of the disease. In patients presented with isolated brain stem syndromes, the symptomatic lesion was often not detected by magnetic resonance (MR) imaging. But patients with asymptomatic infratentorial lesions progressed to clinically definite MS in 65% of cases. Infratentorial lesions are included in various MR criteria designed to assist in the differential diagnosis of MS lesions from incidental lesions, to differentiate MS from subcortical encephalopathic arteriopathy. The preferred MR sequence to visualize infratentorial lesions is the fast spin echo sequence. It is preferred to conventional spin echo and fast fluid attenuated inversion recovery sequences because of its relatively short acquisition time and good sensitivity. The correlation between disability and infratentorial lesion load on T2 weighted sequences is controversial. However, it was recently shown that the correlations between clinical measures and T1 lesion load, histogram magnetization transfer ratio and peak positions, and infratentorial volume measurements are strong. These findings suggest that one of the major factors in the development of disability in patients with MS is the pathological damage in clinically eloquent sites such as the brain stem and cerebellum.

Brain Diseases↗
PubMed2000

[Gliomatosis cerebri: two case reports with atypical clinical and neuroradiologic findings].

The diagnosis of the rare disease Gliomatosis cerebri requires the correlation of clinical, radiological, and pathological findings. We report on two patients with intravitally diagnosed gliomatosis cerebri. Due to the unusually high malignancy of the tumor cells, diagnosis was complicated by atypical findings such as gadolinium enhancement in MRI and raised intracranial pressure. The clinical course, differential diagnosis, and literature are summarized briefly.

Biopsy↗
PubMed2000

Intracranial dural arteriovenous fistula with spinal medullary venous drainage.

We report on a 46-year-old patient in whom an intracranial dural arteriovenous (AV) fistula, supplied by a branch of the ascending pharyngeal artery, drained into spinal veins and produced rapidly progressive symptoms of myelopathy and brainstem dysfunction including respiratory insufficiency. Magnetic resonance imaging studies demonstrated brainstem oedema and dilated veins of the brainstem and spinal cord. Endovascular embolization of the fistula led to good neurological recovery, although the patient had been paraplegic for 24 h prior to embolization. This case demonstrates the MRI characteristics of an intracranial dural AV fistula with spinal drainage and illustrates the importance of early diagnosis and treatment. Even paraplegia may be reversible, if angiography is performed and the fistula treated before ischaemic and gliotic changes become irreversible.

Central Nervous System Vascular Malformations↗
PubMed2000

Visualization of cranial nerves I-XII: value of 3D CISS and T2-weighted FSE sequences.

The aim of this study was to evaluate the sensitivity of the three-dimensional constructive interference of steady state (3D CISS) sequence (slice thickness 0.7 mm) and that of the T2-weighted fast spin echo (T2-weighted FSE) sequence (slice thickness 3 mm) for the visualization of all cranial nerves in their cisternal course. Twenty healthy volunteers were examined using the T2-weighted FSE and the 3D CISS sequences. Three observers evaluated independently the cranial nerves NI-NXII in their cisternal course. The rates for successful visualization of each nerve for 3D CISS (and for T2-weighted FSE in parentheses) were as follows: NI, NII, NV, NVII, NVIII 40 of 40 (40 of 40), NIII 40 of 40 (18 of 40), NIV 19 of 40 (3 of 40), NVI 39 of 40 (5 of 40), NIX, X, XI 40 of 40 (29 of 40), and NXII 40 of 40 (4 of 40). Most of the cranial nerves can be reliably assessed when using the 3D CISS and the T2-weighted FSE sequences. Increasing the spatial resolution when using the 3D CISS sequence increases the reliability of the identification of the cranial nerves NIII-NXII.

Adult↗
PubMed2000

A comparison of the sensitivity of MRI after double- and triple-dose Gd-DTPA for detecting enhancing lesions in multiple sclerosis.

We compared the number and volume of enhancing lesions detected in patients with multiple sclerosis (MS) seen on post-contrast T(1)-weighted scans obtained after the injection of different gadolinium-DTPA (Gd) doses. Enhanced magnetic resonance imaging (MRI) scans were obtained from 16 patients with relapsing remitting or secondary progressive MS on two different occasions separated by an interval of approximately 24 h. On the first occasion, enhanced scans were obtained 15 min after the injection of a double dose of Gd (0.2 mmol/Kg), on the second 15 min after the injection of a triple dose (0.3 mmol/Kg) of Gd. Scans were assessed by consensus in a random order by two observers unaware of the dose of Gd used. We counted the same 30 enhancing lesions on both double dose and triple dose scans from 9 patients. The mean (SD) volumes of enhancing lesions were 1.7 (2.7) mL on double dose and 1.9 (3.4) mL on triple-dose scans. This difference was not statistically significant. This study demonstrated that double dose of Gd has a sensitivity for detecting MS activity similar to that of a triple dose, with the advantage of a significant cost saving.

Adult↗
PubMed2000

Serial gadolinium-DTPA of spinal cord MRI in multiple sclerosis: triple vs. single dose.

We compared the sensitivity of single and triple dose Gd-DTPA magnetic resonance imaging (MRI) in detecting enhancing lesions in the spinal cord (SC) from 15 patients with multiple sclerosis (MS). The patients were examined monthly on four occasions. We detected two enhancing lesions in two of 15 (13%) patients when a single dose of Gd-DTPA was used. No additional lesions were detected when a triple dose of Gd-DTPA was used. These results 1) confirm that enhanced spinal cord imaging does not significantly increase the detection of active lesions in MS, 2) they do not support the general application of triple dose Gd-DTPA when examining the SC but 3) suggest that further studies taking into account SC symptoms are necessary.

Adult↗
PubMed2000

Reduction of benzodiazepine receptor binding is related to the seizure onset zone in extratemporal focal cortical dysplasia.

PURPOSE: Comparison of regional reduction of GABA receptor binding and seizure onset zone in patients with extratemporal epilepsy due to focal cortical dysplasia. METHODS: Two patients with frontal lobe epilepsy who remained seizure free after partial frontal lobe resection were investigated with magnetic resonance imaging, positron emission tomography (PET) with 18F-fluoro-deoxy-glucose (FDG) and 11C-flumazenil, subdural EEG-video recordings, and postoperative benzodiazepine (BDZ)-receptor autoradiography. RESULTS: The area of reduced BDZ-receptor binding as documented by preoperative flumazenil-PET and postoperative BDZ-receptor autoradiography corresponded to the seizure onset zone and was smaller than the interictal hypometabolism documented by FDG-PET. CONCLUSION: Flumazenil-PET is a useful tool for localization of the epileptogenic zone in patients with extratemporal epilepsy caused by focal cortical dysplasia. Neuronal distribution of BDZ-receptor density confirms in vivo flumazenil-PET findings. The regional reduction of BDZ-receptor binding in focal cortical dysplasia seems to be confined to the seizure onset zone and not to the extent of dysplastic cortex.

Adolescent↗
PubMed2000

Primary diffuse leptomeningeal gliomatosis: unusual MRI with non-enhancing nodular lesions on the cerebellar surface and spinal leptomeningeal enhancement.

A 28 year old man presented with a 1 month history of symptoms of intracranial hypertension. Examination showed bilateral papilloedema and meningeal signs. Magnetic resonance imaging showed nodular lesions on the cerebellar and pontine surface and thickening of the thoracic spinal leptomeninges. Throughout the course of the disease, contrast enhancement was detected in the spinal leptomeninges but not intracranially. Primary diffuse leptomeningeal gliomatosis (PDLG) was diagnosed by biopsy and later confirmed on necropsy. The present case is remarkable for the nodular superficial cerebellar lesions and the absence of intracranial contrast enhancement of the leptomeninges.

Adult↗
PubMed2000

Late onset postpartum eclampsia without pre-eclamptic prodromi: clinical and neuroradiological presentation in two patients.

In two patients eclampsia started 9 days postpartum. Headache and visual disturbances preceded seizures but none of the classic pre-eclamptic signs oedema, proteinuria, and hypertension were present until shortly before seizure onset. Brain herniation (patient 1) and status epilepticus (patient 2) necessitated neurointensive care management. Brain MRI initially showed only frontal sulcal effacement in one patient but later showed white matter hyperintensities on T2 weighted images and a previously undescribed pattern of cortical-subcortical postgadolinium enhancement on T1 weighted images in both. Neurological deficits and MRI findings were reversed with therapy in both patients. It is concluded that late postpartum eclampsia can manifest without classic prodromi and that characteristic MRI findings may lag behind clinical manifestation.

Adult↗
PubMed2000

Ictal SPECT hyperperfusion reflects the activation of the symptomatogenic cortex in spontaneous and electrically-induced non-habitual focal epileptic seizures: correlation with subdural EEG recordings.

We report a patient with left temporal lobe epilepsy and a left parietal angioma, in whom ictal SPECT showed hyperperfusion in a spontaneous and an electrically-induced, non-habitual focal seizure. A SPECT investigation during an habitual seizure originating in the left temporal lobe showed a left temporal hyperperfusion. Electrical stimulation of the parietal cortex adjacent to the location of a previously resected angioma using subdural electrodes resulted in a non-habitual seizure beginning with a unilateral somatosensory aura. Ictal SPECT of this seizure demonstrated contralateral central hyperperfusion. We conclude from our findings that ictal SPECT hyperperfusion reflects the activation of symptomatogenic cortex, which can be induced by both epileptic discharge and electrical stimulation.

Adult↗