scholarly journals The Mechanism of Macular Sparing

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jonathan C. Horton ◽  
John R. Economides ◽  
Daniel L. Adams
Keyword(s):  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Posterior Cerebral Artery ◽  
Occipital Lobe ◽  
Collateral Flow ◽  
Dual Representation ◽  
Field Representation ◽  
Occipital Pole ◽  
The Impact ◽  
Macular Sparing

Patients with homonymous hemianopia sometimes show preservation of the central visual fields, ranging up to 10°. This phenomenon, known as macular sparing, has sparked perpetual controversy. Two main theories have been offered to explain it. The first theory proposes a dual representation of the macula in each hemisphere. After loss of one occipital lobe, the back-up representation in the remaining occipital lobe is postulated to sustain ipsilateral central vision in the blind hemifield. This theory is supported by studies showing that some midline retinal ganglion cells project to the wrong hemisphere, presumably driving neurons in striate cortex that have ipsilateral receptive fields. However, more recent electrophysiological recordings and neuroimaging studies have cast doubt on this theory by showing only a minuscule ipsilateral field representation in early visual cortical areas. The second theory holds that macular sparing arises because the occipital pole, where the macula is represented, remains perfused after occlusion of the posterior cerebral artery because it receives collateral flow from the middle cerebral artery. An objection to this theory is that it cannot account for reports of macular sparing in patients after loss of an entire occipital lobe. On close scrutiny, such reports turn out to be erroneous, arising from inadequate control of fixation during visual field testing. Patients seem able to detect test stimuli on their blind side within the macula or along the vertical meridian because they make surveillance saccades. A purported treatment for hemianopia, called vision restoration therapy, is based on this error. The dual perfusion theory is supported by anatomical studies showing that the middle cerebral artery perfuses the occipital pole in many individuals. In patients with hemianopia from stroke, neuroimaging shows preservation of the occipital pole when macular sparing is present. The frontier dividing the infarcted territory of the posterior cerebral artery and the preserved territory of the middle cerebral artery is variable, but always falls within the representation of the macula, because the macula is so highly magnified. For physicians, macular sparing was an important neurological sign in acute hemianopia because it signified a posterior cerebral artery occlusion. Modern neuroimaging has supplanted the importance of that clinical sign but at the same time confirmed its validity. For patients, macular sparing remains important because it mitigates the impact of hemianopia and preserves the ability to read fluently. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

ANTERIOR CEREBRAL ARTERY AMPUTATION AND SALVAGE REPAIR OF INTERNAL CAROTID ARTERY TEAR

Neurosurgery ◽  
2009 ◽  
Vol 65 (4) ◽  
pp. E820-E822 ◽  
Author(s):  
Scott D. Wait ◽  
Steven W. Chang ◽  
Brendan D. Killory ◽  
William L. White ◽  
Robert F. Spetzler
Keyword(s):  
Carotid Artery ◽  
Internal Carotid Artery ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Internal Carotid ◽  
Anterior Cerebral Artery ◽  
Primary Repair ◽  
Suture Repair ◽  
Collateral Flow ◽  
The Impact

Abstract OBJECTIVE We describe a novel technique used to repair an unanticipated tear of the internal carotid artery (ICA) requiring anterior cerebral artery (ACA) amputation to allow primary repair of the arteriotomy. CLINICAL PRESENTATION A 59-year-old woman underwent an orbitozygomatic craniotomy to treat a large, suprasellar, thyroid-stimulating hormone-secreting adenoma. During resection, an incidental ICA tear occurred opposite the exit of the middle cerebral artery. TECHNIQUE After an ICA tear on the wall opposite the middle cerebral artery occurred, clips were placed on the ICA, middle cerebral artery, and ACA. Primary closure was not feasible without critically stenosing the ICA. The ipsilateral ACA was clipped and amputated just distal to its origin. The relaxation afforded by amputating the ACA allowed primary suture repair of the arteriotomy. A clip was placed on the proximal ACA stump. The distal ACA stump revealed good backflow and was also clipped. CONCLUSION When an arteriotomy of a large intracranial artery cannot be repaired primarily, creative alternatives must be considered. Amputation of a branch artery with sufficient collateral flow is a method to afford adequate relaxation for primary repair of an arteriotomy. This novel method should be considered in the armamentarium of neurosurgeons to minimize the impact of potentially disastrous vascular complications.

scholarly journals A Protocol for Characterizing the Impact of Collateral Flow after Distal Middle Cerebral Artery Occlusion

2010 ◽  
Vol 2 (1) ◽  
pp. 112-127 ◽  
Author(s):  
Richard Anthony DeFazio ◽  
Sean Levy ◽  
Carmen L. Morales ◽  
Rebecca V. Levy ◽  
Hung W. Lin ◽  
...  
Keyword(s):  
Middle Cerebral Artery ◽  
Middle Cerebral Artery Occlusion ◽  
Cerebral Artery ◽  
Artery Occlusion ◽  
Collateral Flow ◽  
Cerebral Artery Occlusion ◽  
The Impact ◽  
Distal Middle Cerebral Artery

scholarly journals The impact of betamethasone on fetal pulmonary, umbilical and middle cerebral artery Doppler velocimetry and its relationship with neonatal respiratory distress syndrome

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Homeira Vafaei ◽  
Fahimeh Kaveh Baghbahadorani ◽  
Nasrin Asadi ◽  
Maryam Kasraeian ◽  
Azam Faraji ◽  
...  
Keyword(s):  
Pulmonary Artery ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Distress Syndrome ◽  
Exposed Group ◽  
Doppler Velocity ◽  
Corticosteroid Administration ◽  
The Impact

Abstract Background Prenatal corticosteroid administration is known to be an effective strategy in improving fetal pulmonary maturity. This study aimed to evaluate the impact of maternal betamethasone administration on fetal pulmonary and other arteries Doppler velocity and the correlation between RDS development and Doppler indices results. Methods Fifty one singleton pregnancies between 26 and 34 gestational weeks with a diagnosis of preterm labor were included in the exposed group and received betamethasone. Fifty one uncomplicated pregnancies were included in the non-exposed group. Fetal pulmonary, umbilical and middle cerebral arteries Doppler parameters were evaluated before and 24 to 48 h after steroid administration in the exposed group and two times at same intervals in the non-exposed group. Maternal records were matched to neonatal charts if delivery happened, and demographic and outcome data were abstracted. Results When compared with the nonexposed group, fetuses treated with corticosteroids demonstrated significantly decreased umbilical artery Pulsatility index (PI) and significantly increased the middle cerebral artery PI, pulmonary artery Acceleration time (AT) and pulmonary artery AT/ET (Ejection time), while all other indices remained similar. We found significantly decreased pulmonary artery AT in the fetuses with respiratory distress syndrome (RDS) compared to those that did not. Conclusions The results of our study showed that maternal antenatal betamethasone administration caused significant changes in the fetus blood velocity waveforms and also affected the blood flow in the pulmonary artery which led to an increase in the pulmonary artery AT and AT/ET. Among those fetuses with RDS, we found a significant decrease in the pulmonary artery AT, but we did not observe any pulmonary artery AT/ET differences.

Association of Infarct Volume Before Hemicraniectomy and Outcome After Malignant Infarction

Neurology ◽  
2021 ◽  
pp. 10.1212/WNL.0000000000011987
Author(s):  
Dominik Lehrieder ◽  
Katharina Layer ◽  
Hans-Peter Müller ◽  
Viktoria Rücker ◽  
Jan Kassubek ◽  
...  
Keyword(s):  
Infarct Size ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Randomized Trials ◽  
Infarct Volume ◽  
Unfavorable Outcome ◽  
Inclusion Criteria ◽  
Younger Patients ◽  
Malignant Infarction ◽  
The Impact

ObjectiveTo determine the impact of infarct volume before hemicraniectomy in malignant middle cerebral artery infarction (MMI) as an independent predictor for patient selection and outcome prediction, we retrospectively analyzed data of 140 patients from a prospective multi-center study.MethodsPatients from the DESTINY-Registry that underwent hemicraniectomy after ischemic infarction of >50% of the middle cerebral artery territory were included. Functional outcome according to the modified Rankin Scale (mRS) was assessed at 12 months. Unfavorable outcome was defined as mRS 4-6. Infarct size was quantified semi-automatically from computed tomography or magnetic resonance imaging before hemicraniectomy. Subgroup analyses in patients fulfilling inclusion criteria of randomized trials in younger patients (age≤60y) were predefined.ResultsAmong 140 patients with complete datasets (34% female, mean (SD) age 54 (11) years), 105 (75%) had an unfavorable outcome (mRS > 3). Mean (SD) infarct volume was 238 (63) ml. Multivariable logistic regression identified age (OR 1.08 per 1 year increase; 95%-CI 1.02-1.13; p=0.004), infarct size (OR 1.27 per 10ml increase; 95%-CI 1.12-1.44; p<0.001) and NIHSS (OR 1.10; 95%-CI 1.01-1.20; p=0.030) before hemicraniectomy as independent predictors for unfavorable outcome. Findings were reproduced in patients fulfilling inclusion criteria of randomized trials in younger patients. Infarct volume thresholds for prediction of unfavorable outcome with high specificity (94% in overall cohort and 92% in younger patients) were more than 258 ml before hemicraniectomy.ConclusionOutcome in MMI strongly depends on age and infarct size before hemicraniectomy. Standardized volumetry may be helpful in the process of decision making concerning hemicraniectomy.

Studies of collateral perfusion to canine middle cerebral artery territory

1990 ◽  
Vol 259 (2) ◽  
pp. H560-H566 ◽  
Author(s):  
C. M. Loftus ◽  
G. M. Greene ◽  
K. N. Detwiler ◽  
G. L. Baumbach ◽  
D. D. Heistad
Keyword(s):  
At Risk ◽  
Blood Flow ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Autologous Blood ◽  
Base Line ◽  
Collateral Flow ◽  
Area At Risk ◽  
Risk Area ◽  
Anatomical Basis

Previous studies of intracranial collateral circulation have not distinguished between true "collateral" blood flow (flow to a region that occurs only when a primary artery is occluded) and "overlap" flow (flow to a region that is present under both normal and demand conditions). These experiments had three purposes: 1) to identify tissues that were truly collateral dependent, 2) to determine potential for true collateral flow in the absence of overlap flow, and 3) to determine whether an anatomical basis for overlap flow could be demonstrated. Branches (700-900 microns) of the dog middle cerebral artery (MCA) were perfused with autologous blood. The perfused region, which was the area at risk, was identified by intravenous injection of neutral red dye. Microspheres were used to measure regional cerebral blood flow (rCBF). Overlap flow was determined by perfusion of the artery with microsphere-free blood. True collateral flow (total rCBF minus overlap flow) was determined by analysis of rCBF to the risk area after cessation of vessel perfusion. Most of the risk area had substantial levels of overlap flow (about one-third of base line). In the center of the area at risk, the true collateral-dependent area was identified [mean overlap flow 4 +/- 1 (mean +/- SE) ml.min-1.100 g-1], which had high levels of perfusion from collateral vessels (102 +/- 14) within 30 s of vascular occlusion. Microfil injection into two adjacent MCA branches showed discrete borders between vascular territories, with no overlapping vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Modeling of the Human Cerebral Collateral Circulation: Evaluation of the Impact on the Cerebral Perfusion in Case of Ischemic Stroke

2019 ◽  
Vol 5 (1) ◽  
pp. 533-536
Author(s):  
Lorena Krames ◽  
Rosa Daschner ◽  
Yannick Lutz ◽  
Axel Loewe ◽  
Olaf Dössel ◽  
...  
Keyword(s):  
Blood Flow ◽  
Ischemic Stroke ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Collateral Circulation ◽  
Treatment Method ◽  
Developed Countries ◽  
Extended Model ◽  
Flow Through ◽  
The Impact

AbstractStroke is the third-most cause of death in developed countries. A new promising treatment method in case of an ischemic stroke is selective intracarotid blood cooling combined with mechanical artery recanalization. However, the control of the treatment requires invasive or MRI-assisted measurement of cerebral temperature. An auspicious alternative is the use of computational modeling. In this work, we extended an existing 1D hemodynamics model including the characteristics of the anterior, middle and posterior cerebral artery. Furthermore, seven ipsilateral anastomoses were additionally integrated for each hemisphere. A potential stenosis was placed into the M1 segment of the middle cerebral artery, due to the highest risk of occlusion there. The extended model was evaluated for various degrees of collateralization (“poor”, “partial” and “good”) and degrees of stenosis (0%, 50%, 75% and 99.9%). Moreover, cerebral autoregulation was considered in the model. The higher the degree of collateralization and the degree of stenosis, the higher was the blood flow through the collaterals. Hence, a patient with a good collateralization could compensate a higher degree of occlusion and potentially has a better outcome after an ischemic stroke. For a 99.9% stenosis, an increased summed mean blood flow through the collaterals of +97.7% was predicted in case of good collateralization. Consequently, the blood supply via the terminal branches of the middle cerebral artery could be compensated up to 44.4% to the physiological blood flow. In combination with a temperature model, our model of the cerebral collateral circulation can be used for tailored temperature prediction for patients to be treated with selective therapeutic hypothermia.

THE IMPACT OF BALLOON ANGIOPLASTY ON THE EVOLUTION OF VASOSPASM-RELATED INFARCTION AFTER ANEURYSMAL SUBARACHNOID HEMORRHAGE

Neurosurgery ◽  
2008 ◽  
Vol 62 (3) ◽  
pp. 610-617 ◽  
Author(s):  
Leonie Jestaedt ◽  
Mirko Pham ◽  
Andreas J. Bartsch ◽  
Ekkehard Kunze ◽  
Klaus Roosen ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Balloon Angioplasty ◽  
Anterior Cerebral Artery ◽  
Aneurysmal Subarachnoid Hemorrhage ◽  
Fisher Exact Test ◽  
Computed Tomographic ◽  
Fisher Grade ◽  
The Impact

Abstract OBJECTIVE Vasospasm of the cerebral vessels remains a major source for morbidity and mortality after aneurysmal subarachnoid hemorrhage. The purpose of this study was to evaluate the frequency of infarction after transluminal balloon angioplasty (TBA) in patients with severe subarachnoid hemorrhage-related vasospasm. METHODS We studied 38 patients (median Hunt and Hess Grade II and median Fisher Grade 4) with angiographically confirmed severe vasospasm (&gt;70% vessel narrowing). A total of 118 vessels with severe vasospasm in the anterior circulation were analyzed. Only the middle cerebral artery, including the terminal internal carotid artery, was treated with TBA (n = 57 vessel segments), whereas the anterior cerebral artery was not treated (n = 61 vessel segments). For both the treated and the untreated vessel territories, infarction on unenhanced computed tomographic scan was assessed as a marker for adverse outcome. RESULTS Infarction after TBA occurred in four middle cerebral artery territories (four out of 57 [7%]), whereas the infarction rate was 23 out of 61 (38%) in the anterior cerebral artery territories not subjected to TBA (P &lt; 0.001, Fisher exact test). Three procedure-related complications occurred during TBA (dissection, n = 1; temporary vessel occlusions, n = 2). One of these remained asymptomatic, whereas this may have contributed to the development of infarction on follow-up computed tomographic scans in two cases. CONCLUSION In a population of patients with a high risk of infarction resulting from vasospasm after subarachnoid hemorrhage, the frequency of infarction in the distribution of vessels undergoing TBA amounts to 7% and is significantly lower than in vessels not undergoing TBA despite some risk inherent to the procedure.

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