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Biomedical subjects

I A Awad

Publications and source records attributed to I A Awad.

At least 73 records · Page 4Linked to original sources
PubMed1994

Magnetic resonance diffusion-weighted imaging: sensitivity and apparent diffusion constant in stroke.

Magnetic resonance diffusion-weighted imaging (MR-DWI) is sensitive to the diffusibility of water and may offer characterization and anatomical localization of stroke leading to early tailored therapeutic intervention. We compared DWI, the apparent diffusion constant (ADC), and autoradiographic cerebral blood flow (CBF) in a model of focal cerebral ischemia in the rat. Sprague-Dawley rats were embolized with a single silicone cylinder injected into the internal carotid artery. Both common carotids were permanently ligated. The animals were anesthetized (isoflurane in O2), and paralyzed (gallamine). MR-DWI were obtained with a GE 4.7 T magnet (TE = 3 s, TR = 80 msec, b = 2393.10(-3) mm2/s, slice thickness 3 mm). DWI and CBF autoradiograms were compared visually. ADC was assessed in various regions, including ischemic cortex and a region homologous to ischemic cortex. Imaging times from stroke onset were 50 +/- 6 min (mean +/- SEM) for DWI, 185 +/- 17 min for a second DWI. CBF was determined at 258 +/- 15 min. The specificity was 100% at both 50 min and 185 min, indicating that there were no false positives; in 3 animals ischemia was not present. However, the sensitivity analysis indicated that early DWI yields some false negatives; at 50 min the sensitivity was 60%. We attribute our result of low early sensitivity to small infarcts in relation to the slice thickness. Later, at 185 min, sensitivity was 100%. The first ADCs were higher than the second ADC values in ischemic cortex. For infarcts larger than the slice thickness, early MR-DWI is highly sensitive for imaging evolving ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Functional anatomy of the human supplementary sensorimotor area: results of extraoperative electrical stimulation.

Electrical stimulation studies have demonstrated that a "supplementary motor area" (SMA) exists in humans. However, its precise functional organization has not been well defined. We reviewed the extraoperative electrical stimulation studies of 15 patients with intractable epilepsy who were evaluated with chronically implanted interhemispheric subdural electrodes. SMA-type positive motor responses were elicited not only from the mesial portion of the superior frontal gyrus but also from its dorsal convexity, and from the paracentral lobule, cingulate gyrus, and precuneus. Sensory symptoms, that could not be attributed to stimulation of the primary sensory area, were elicited from the superior frontal and cingulate gyri in addition to the precuneus. Therefore, human SMA, as defined by electrical stimulation, is not always confined to the mesial portion of the superior frontal gyrus as described previously. It is also not strictly "motor" but "sensorimotor" in representation. We propose referring to this region as the "supplementary sensorimotor area" (SSMA). We observed a somatotopic organization within the SSMA with an order of lower extremity, upper extremity, and head from posterior to anterior. Sensory representation in an individual was either anterior or posterior to the positive motor representation but never both. There was a supplementary eye field within the head representation. A supplementary negative motor area was noted at the anterior aspect of the SSMA. No language area was demonstrated within the SSMA. The physiologic significance of the SSMA and functional consequences of its resection must be addressed in further studies.

Adolescent↗
PubMed1994

Vascular malformations and epilepsy: clinical considerations and basic mechanisms.

Vascular malformations (VMs) are associated with epilepsy. The natural history of the various VMs, clinical presentation, and tendency to provoke epilepsy determine treatment strategies. Investigations have probed the mechanisms of epileptogenesis associated with these lesions. Electrophysiologic changes are associated with epileptogenic cortex adjacent to VMs. Putative pathophysiologic mechanisms of epileptogenesis include neuronal cell loss, glial proliferation and abnormal glial physiology, altered neurotransmitter levels, free radical formation, and aberrant second messenger physiology.

Brain Ischemia↗
PubMed1994

Occult intracranial aneurysms in polycystic kidney disease: screening with MR angiography.

PURPOSE: To estimate the prevalence, location, and type of cerebral aneurysms in patients with adult polycystic kidney disease (PCKD) and identify associated risk factors. MATERIALS AND METHODS: Ninety-three patients with PCKD were screened for aneurysms with spin-echo parenchymal magnetic resonance (MR) imaging and three-dimensional time-of-flight MR angiography. Prevalence was estimated with the calculated proportions of patients who had aneurysms, adjusted for reported sensitivity and specificity of MR angiography. RESULTS: Thirteen aneurysms, found in 10 patients, were 7 mm or smaller in largest dimension; 11 of these aneurysms were saccular. Intra- and interobserver variabilities were 96%-98%. Conventional arteriograms, obtained in six patients, helped confirm the MR angiographic findings. The best estimates of prevalence of aneurysms were 11.7% in the study group (n = 93) and 25.8% in patients with a family history of aneurysms (n = 6). CONCLUSION: The prevalence of aneurysms in the study group was greater than in the general population. MR angiography is useful in screening for cerebral aneurysms.

Adult↗
PubMed1994

Intracranial hypertension after resection of cerebral arteriovenous malformations. Predisposing factors and management strategy.

BACKGROUND AND PURPOSE: Surgical excision of cerebral arteriovenous malformations (AVMs) may be complicated by postoperative breakthrough edema and hemorrhage and by intracranial hypertension. Embolization, staged resection, and meticulous surgical technique have decreased but not completely eliminated this complication. In this study we prospectively assess the prevalence of intracranial hypertension after excision of cerebral AVMs, examine factors predisposing to this complication, and document the outcome of aggressive monitoring and treatment of elevated intracranial pressure (ICP). METHODS: During a 4-year period at a single institution, 32 consecutive patients with cerebral AVMs underwent surgical excision after staged embolization. All patients underwent postoperative monitoring of ICP and a uniform management protocol of intracranial hypertension. RESULTS: Intractable intracranial hypertension was encountered after resection of 9 of 32 cerebral AVMs, including 3 of 20 (15%) AVMs 6 cm or less in maximum diameter and 6 of 12 (50%) AVMs greater than 6 cm in maximum diameter. This complication occurred in 5 of 10 (50%) lesions located in distal or border-zone locations, in 4 of 9 (44%) AVMs arising directly off proximal cerebral arteries, and in none of 13 AVMs in other locations. Preoperative single-photon emission-computed tomography perfusion scans were performed in 17 patients and demonstrated parenchymal hypoperfusion beyond the AVM nidus in 5 of 10 AVMs 6 cm or less in maximum diameter, none of which manifested postoperative intractable ICP. Hypoperfusion was observed on single-photon emission-computed tomography in 7 of 7 AVMs greater than 6 cm that were studied by this modality, and intractable ICP was observed postoperatively in 5 of these cases despite preoperative staged embolization in every case. Patients with symptomatic intractable ICP were treated with intravenous short-acting barbiturates under a strict critical care protocol. There was no instance of uncontrollable intracranial hypertension or break-through edema while on barbiturate therapy. There was no permanent morbidity related to this treatment and no mortality or new disability morbidity in this series. CONCLUSIONS: We conclude that intractable intracranial hypertension remains a common complication after resection of a subgroup of cerebral AVMs despite preoperative embolization, modern neuroanesthesia and critical care management, and microsurgical technique. A proactive management protocol aimed at ICP control is safe and effective in the management of this complication.

Barbiturates↗
PubMed1993

Comparison and spacial correlation of interictal HMPAO-SPECT and FDG-PET in intractable temporal lobe epilepsy.

The respective contribution of interictal HMPAO-SPECT and FDG-PET to the imaging of the epileptogenic zone in intractable temporal lobe epilepsy is not known. Ten consecutive patients with drug resistant focal epilepsy of temporal lobe origin were studied with prolonged noninvasive video-EEG monitoring, magnetic resonance imaging, interictal FDG-PET and HMPAO-SPECT. Five patients demonstrated unitemporal and 5 patients bitemporal interictal and/or ictal EEG epileptiform abnormalities. We developed a 3-dimensional semiquantitative method for interpretation and comparison of FDG-PET and HMPAO-SPECT using a 15-compartment model of the temporal lobe. In all 5 patients with unilateral epileptogenicity, interictal hypometabolism and hypoperfusion were recorded on the side of the EEG abnormalities without discrepancy between PET and SPECT. The severity and the extent of focal abnormalities were consistently greater on PET than on SPECT, in agreement with previously well documented better 'sensitivity' of PET. Among the 5 patients with bitemporal epileptogenicity, results of SPECT and PET were convergent in only 2 cases. In this group, SPECT abnormalities appeared more profound but either SPECT or PET were not constantly correlated with the side of predominant EEG epileptogenicity. Abnormalities on PET and SPECT were more frequently limited to mesiobasal structures among cases with unilateral epileptogenicity and tended to involve neocortical structures in bitemporal cases. We conclude that interictal FDG-PET and HMPAO-SPECT provide the same type of information on the side of the epileptogenic zone in cases with clearly unilateral epileptogenicity, with abnormalities more intense and more extensive on PET.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Pathogenesis of subcortical hyperintense lesions on magnetic resonance imaging of the brain. Observations in patients undergoing controlled therapeutic internal carotid artery occlusion.

BACKGROUND AND PURPOSE: Factors associated with the pathogenesis of subcortical hyperintense lesions on magnetic resonance imaging of the brain are not known. We describe four cases of de novo genesis of subcortical hyperintense lesions in patients undergoing controlled therapeutic internal carotid artery occlusion, and we speculate on associated pathophysiological mechanisms. METHODS: Twelve consecutive patients underwent controlled therapeutic internal carotid artery occlusion for symptomatic giant cerebral aneurysm using the detachable balloon technique under full anticoagulation. Preocclusion (within 2 weeks) and postocclusion (within 6 weeks) magnetic resonance imaging of the brain was performed in eight cases and evaluated for preexisting and new appearance of subcortical hyperintense lesions. RESULTS: There were four instances of de novo genesis of subcortical hyperintense lesions after carotid occlusion. New subcortical hyperintense lesions were ipsilateral to carotid occlusion in every instance and in two cases were associated with ipsilateral hemispheric ischemic symptoms despite anticoagulant therapy. In one instance, there were transient hemispheric symptoms without the appearance of new subcortical hyperintense lesions. Age, vascular risk factors, and preexisting subcortical hyperintense lesions did not appear to predispose patients to de novo genesis of new hyperintensities. CONCLUSIONS: This is the first documentation of de novo genesis of subcortical hyperintense lesions in a controlled setting of hemodynamic ischemic insult. Symptomatic and asymptomatic lesions can be detected in this setting. Anticoagulation does not appear to provide protection from this phenomenon. Careful prospective studies are required to further evaluate risk factors and possible clinical consequences associated with the genesis of new subcortical hyperintense lesions.

Aged↗
PubMed1993

Factors predisposing to clinical disability in patients with cavernous malformations of the brain.

The factors predisposing to an aggressive clinical course in cavernous malformations of the brain are not known. Disabilities from neurological deficits and from seizures were assessed and graded in 84 patients harboring 100 cavernous malformations and were correlated with patient sex and age, lesion size, lesion location, lesion multiplicity, and previous overt hemorrhage. Univariate analysis showed that female sex, infratentorial lesion location, and previous gross hemorrhage were significantly associated with subsequent neurological disability. Logistic regression analysis showed that infratentorial lesion location and previous gross hemorrhage were independent factors simultaneously and significantly associated with neurological disability. Age less than 40 was the only significant factor predisposing to seizure disability (in both univariate and multivariate analyses). Lesion size, multiplicity, and other factors did not influence clinical disability. This information should assist in management decisions regarding cavernous malformations.

Adolescent↗
PubMed1993

Giant aneurysms of the proximal anterior cerebral artery: report of three cases.

Aneurysms of any size involving the A1 segment of the anterior cerebral artery are unusual, but giant aneurysms in this location are exceedingly rare, with only five cases previously reported in the literature. We report three cases of A1 segment giant aneurysms presenting with mass effect that were successfully treated. A discussion of the salient features of diagnosis and treatment are presented, along with a brief review of the literature describing these aneurysms. The role of newer imaging modalities, including magnetic resonance imaging, magnetic resonance angiography, and intraoperative angiography, is discussed. The three patients were treated by direct exploration, trapping, and endaneurysmal decompression. Giant A1 segment aneurysms present a unique opportunity to safely trap and decompress the aneurysm with definitive cure.

Adult↗
PubMed1993

Mixed vascular malformations of the brain: clinical and pathogenetic considerations.

The clinical relevance of any scheme for classification of vascular malformations of the brain remains controversial. Widely accepted pathologic classifications include discrete venous, arteriovenous, capillary, and cavernous malformations. Of 280 cases of possible vascular malformations evaluated by a single cerebrovascular service during a 5-year period, 14 were instances of mixed vascular malformations including definite features of more than one pathologically discrete type of malformation within the same lesion. There were six instances of mixed cavernous and venous malformations in the same lesion; in all instances, the cavernous malformation accounted for the clinical presentation. There were three cases of mixed venous and arteriovenous malformations (arterialized venous malformations), presenting with the typical histoarchitectural appearance of a venous malformation, but with arteriovenous shunting; all cases were symptomatic, two with hemorrhage and one with focal neurological symptoms. There were five cases of predominantly cavernous malformations with features of arteriovenous malformation or capillary telangiectasia in the same lesion. These five cases presented clinically as angiographically occult lesions indistinguishable from a cavernous malformation. Lesions including a venous malformation were recognizable preoperatively because of characteristic imaging features of the venous malformation. Other mixed vascular malformations were indistinguishable on diagnostic studies from pure cavernous malformations. Of the 14 mixed vascular malformations, 11 included a cavernous malformation that was usually responsible for the symptomatic presentation. In the other three cases, manifestations of clinical lesions were due to arteriovenous shunting within a venous malformation. We conclude that mixed vascular malformations of the brain are rare entities with distinct clinical, radiological, and pathological profiles. Their identification generates several hypotheses about common pathogenesis or causation-evolution among different types of lesions.

Adolescent↗
PubMed1993

Pathological heterogeneity of angiographically occult vascular malformations of the brain.

There is considerable confusion in the literature regarding the pathological substrates of angiographically occult vascular malformations (AOVMs) of the brain and their clinical significance. We retrospectively reviewed the cases of 34 consecutive patients with AOVMs undergoing surgical excision at a single institution during a 10-year period. Pathological specimens were reexamined, and the lesions were classified according to strict histopathological criteria. There were 21 cavernous malformations, 3 arteriovenous malformations, 3 venous malformations, 2 capillary malformations, and 5 mixed (pathologically heterogeneous) lesions. The initial pathological diagnostic report had been imprecise or had misidentified the lesion type in 18 of the 34 cases (53%), most commonly labeling a cavernous malformation as an arteriovenous malformation or not recognizing mixed features within the same lesion. Clinical presentation (including hemorrhage) and outcome were not significantly different among the various lesion types. Preoperative diagnostic imaging included a variety of modalities that were introduced or evolved during the period of the study and generally suggested a suspected vascular malformation but did not predict pathological subtypes. Acute hematomas in this surgical series made the identification of underlying vascular malformations highly speculative. We conclude that the majority of AOVMs requiring surgical intervention are cavernous malformations, although there was a notable pathological heterogeneity of the remaining lesions. Histopathological subtypes of AOVMs are not associated with unique clinical or radiographic features.

Adolescent↗
PubMed1993

Detection of changes in material-specific memory following temporal lobectomy using the Wechsler Memory Scale-Revised.

To determine the utility of the Wechsler Memory Scale-Revised (WMS-R) in measuring material-specific memory changes, within-subject comparisons of the Verbal-Visual Memory Index discrepancy and discrepancy scores using short-term and delayed Logical Memory and Visual Reproduction subtests from the WMS-R were studied prior to and following temporal lobectomy among 30 patients with left temporal lobectomy, 30 with right temporal lobectomy, and 50 epileptic, non-surgical controls. The groups were matched on age, sex, handedness, age at seizure onset, duration of epilepsy, and presurgical Verbal and Performance IQ; the right temporal group had a higher mean educational level (p <.05). All surgical patients were left hemisphere dominant for speech; those who had persistent postoperative seizures were excluded from study. On retesting, left temporal lobectomy was associated with a marked change in short-term and delayed memory discrepancy scores primarily due to a drop in verbal memory. Right temporal lobectomy was not associated with a drop in visual memory, suggesting that the WMS-R appears to reflect decrements in material-specific memory following left but not right temporal lobectomy. The nonsurgical controls showed increases in both short-term and delayed memory discrepancy scores due to increases in short-term and delayed verbal memory. Relative to these controls, the absence of comparable increases in verbal memory among the right temporal patients suggests that right temporal lobectomy may be associated with risk to verbal memory.

Journal Article↗
PubMed1992

Further observations on the pathology of subcortical lesions identified on magnetic resonance imaging.

We performed postmortem magnetic resonance imaging and pathologic examinations on the brains of seven consecutive patients older than 50 years of age who died of non-neurologic causes. Multiple hyperintense subcortical lesions were identified in each patient, and a total of 29 lesions were examined histologically (eight rims, six caps, six punctate lesions, and nine patches). Rims were characterized by subependymal gliosis and loss of the ependymal lining; caps were associated with myelin pallor, gliosis, and arteriosclerosis; punctate lesions were characterized by dilated perivascular spaces and perivascular gliosis; and patches were associated with myelin pallor and dilated perivascular spaces. The pattern of myelin pallor defined the size and shape of caps and patches. Arteriosclerosis was identified in six of six caps, three of six punctate lesions, and in three of nine patches. These data indicate that (1) each type of hyperintense subcortical lesion has a distinct pathologic correlate; (2) arteriosclerosis is not invariably associated with all types of hyperintense subcortical lesions on magnetic resonance imaging; and (3) myelin pallor appears to contribute to the magnetic resonance imaging signal at 1.5 tesla.

Aged↗
PubMed1992

Application of magnetic resonance angiography to neurosurgical practice: a critical review of 150 cases.

The potential role of magnetic resonance angiography (MRA) in clinical neurosurgical practice was evaluated in 150 consecutive patients in an attempt to define clinical situations in which it aided in diagnosis, helped guide treatment options, and/or possibly eliminated the need for conventional catheter angiography. Among patients with nonvascular pathology (n = 42), MRA provided useful clinical information in 55% of cases, and could have effectively replaced catheter angiography in 76% of cases. In this group of patients, MRA provided excellent depiction of tumour and vessel relationships, and in conjunction with conventional imaging modalities reliably ruled out the question of tumour versus aneurysm whenever that question was raised. Among patients with vascular lesions (n = 108), MRA visualized the lesion in 18 of 20 (90%) aneurysms, 11 of 11 (100%) vascular malformations, 31 or 31 (100%) cases with known occlusive vascular disease, and reliably excluded occlusive vascular disease in 19 of 30 (63%) cases. The MRA potentially could have replaced conventional catheter angiography in less than 8% of cases with vascular pathology treated surgically, and in 76% of cases with vascular pathology treated medically or expectantly. Imaging time was relatively short, 10 to 20 minutes for intracranial vessels and 6.5 to 13 minutes for extracranial vessels. Shortcomings included the lack of spacial resolution required for surgical planning and the possible misleading information in the settings of low flow and partial thrombosis. It is concluded that currently available MRA modalities contribute useful information in a wide spectrum of neurosurgical clinical situations including screening and serial follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1992

Multiple vertebral hemangiomas with neurological signs. Case report.

A case of multiple vertebral hemangiomas with progressive neurological deficit is presented. Successful treatment was accomplished using preoperative embolization, palliative surgical decompression, and postoperative radiation therapy. The patient has remained asymptomatic for 6 years. The authors review the role of current imaging modalities and options for therapeutic intervention. Preoperative embolization, palliative surgical decompression, and postoperative radiotherapy appear to provide a satisfactory outcome in patients with multiple hemangiomas and may represent an effective alternative to more aggressive surgical intervention.

Adult↗