Human consciousness is considered a result of the synchronous “humming” of multiple dynamic netwo... more Human consciousness is considered a result of the synchronous “humming” of multiple dynamic networks. We performed a dynamic functional connectivity analysis using resting state functional magnetic resonance imaging (rsfMRI) in 14 patients before and during a propofol infusion to characterize the sedation-induced alterations in consciousness. A sliding 36-second window was used to derive 59 time points of whole brain integrated local connectivity measurements. Significant changes in the connectivity strength (Z Corr) at various time points were used to measure the connectivity fluctuations during awake and sedated states. Compared with the awake state, sedation was associated with reduced cortical connectivity fluctuations in several areas connected to the default mode network and around the perirolandic cortex with a significantly decreased correlation of connectivity between their anatomical homologues. In addition, sedation was associated with increased connectivity fluctuations ...
Journal of Neuroanaesthesiology and Critical Care, 2015
Recent advances in functional imaging of the brain have enabled a better understanding of the bra... more Recent advances in functional imaging of the brain have enabled a better understanding of the brain functions in health and disease. Amongst various functional imaging techniques, functional magnetic resonance imaging (fMRI) has been more rigorously employed in both clinical practice and in the research arena. This review will discuss the principles and techniques of fMRI, its role in understanding the pathophysiology of brain injury and finally, its clinical application in diagnosing neurological conditions and prognostication of outcome in patients with neurological disorders.
Regional differences in vascular response to anesthetic agents in brain areas with and without tu... more Regional differences in vascular response to anesthetic agents in brain areas with and without tumors have not been investigated till now. The existence of such differences may influence the regional distribution of cerebral blood flow under anesthesia. In 8 patients with frontotemporal gliomas, middle cerebral artery blood flow velocity (VMCA), pulsatality index (PI) and resistance index (RI) were determined in the normal and pathological cerebral hemispheres before and after stable nitrous oxide-halothane anesthesia. During halothane anesthesia, there was an increase in VMCA both in the normal cerebral hemisphere (69 +/- 11 to 100 +/- 38 cm/s; P = 0.05) and the hemisphere with tumor (65 +/- 17 to 83 +/- 28 cm/s; P = 0.04). A significant decrease in the pulsatality index and the resistance index was also observed in both the hemispheres (P < 0.05). The percentage changes of VMCA, PI and RI in both the hemispheres after anesthesia were not significantly different. In patients wit...
called autoregulation to secure a constant cerebral blood flow over a wide range of mean BP. Howe... more called autoregulation to secure a constant cerebral blood flow over a wide range of mean BP. However, cerebral autoregulation does not work if the brain becomes ischemic. Then, cerebral blood flow will be dependent on its mean BP. In this instance, high BP would have a beneficial effect on the maintenance of cerebral perfusion. In fact, transient arterial BP elevation is observed in 80% of ischemic stroke patients. The course of transient high BP in the acute ischemic stroke was inversely associated with the degree of recanalization in the ischemic area. When recanalization failed, high BP was sustained longer than in successfully recanalized cases. In conclusion, it would be reasonable for the anesthesiologist to consider the possibility of thromboembolism in the case of sudden high BP with no reason.
Brain tumours constitute the majority of neurosurgical conditions that present for elective opera... more Brain tumours constitute the majority of neurosurgical conditions that present for elective operations. The nature of the lesions varies from benign tumours like meningiomas and schwannomas to highly malignant tumours like glioblatomas. About 80% of the tumors are located in the supratentorial compartment and about 20% in the posterior fossa.
Patients presenting for neurosurgery may have coexisting ophthalmic diseases. During the process ... more Patients presenting for neurosurgery may have coexisting ophthalmic diseases. During the process of surgery for the primary neurosurgical condition, the ophthalmic disease may get aggravated. The following is a discussion on a few such conditions, which need to be taken care of to ensure that the success of neurosurgery is not associated with deterioration of the ophthalmic condition.
Guillain Barré Syndrome (GBS) is one of the commonest acquired immune-mediated neuropathies, ofte... more Guillain Barré Syndrome (GBS) is one of the commonest acquired immune-mediated neuropathies, often preceded by infections. Although cellular immune responses are shown to substantially account for the pathophysiology of GBS, the precise mechanistic basis of risk and disease course remains enigmatic till date. Cytokines are best known for their abilities to drive cellular immunity and inflammation through their co-ordinated actions. Data obtained from clinical and animal model studies suggest important implications of some of the cytokines in the progression and recovery of GBS. However, these studies were performed on few cytokines and small set of GBS patients, thereby lacking a complete understanding of the patterns of association of cytokines representing Th1, Th2, and Th17 responses with GBS. We studied 65 well-characterized GBS patients and 73 age- and sex-matched healthy controls. A panel of 15 cytokines representing Th1, Th2 and Th17 pathways was assayed using Multiplex Suspe...
There have been some major conceptual changes in the approach to patients with both traumatic and... more There have been some major conceptual changes in the approach to patients with both traumatic and nontraumatic cerebral injury, in recent years. These changes have their basis in a better understanding of the cerebral pathophysiology and availability of some recent monitors of cerebral function. Both traditional and modern therapeutic innovations are being subjected to extensive investigation. Evidence-based guidelines are now available for the management of traumatic brain injury. Increasing emphasis is being laid on monitoring not only intracranial pressure and cerebral perfusion pressure, but also cerebral blood flow, oxygenation and metabolism. Alternative osmotherapeutic choices are being explored. With a large pool of high quality evidence, more focused and precise therapeutic innovations are likely to emerge in near future.
... Curr Op Anesthesiol 2007; 20:331-335. 6. Sarang A, Dinsmore J. Anaesthesia for awake cranioto... more ... Curr Op Anesthesiol 2007; 20:331-335. 6. Sarang A, Dinsmore J. Anaesthesia for awake craniotomy evolution of a technique that facilitates awake neurological testing. ... Neurosurgery1998;42:219-225. 8. Anandh B, Reddy KRM, Mohanty A, Umamaheswara Rao ...
Human consciousness is considered a result of the synchronous “humming” of multiple dynamic netwo... more Human consciousness is considered a result of the synchronous “humming” of multiple dynamic networks. We performed a dynamic functional connectivity analysis using resting state functional magnetic resonance imaging (rsfMRI) in 14 patients before and during a propofol infusion to characterize the sedation-induced alterations in consciousness. A sliding 36-second window was used to derive 59 time points of whole brain integrated local connectivity measurements. Significant changes in the connectivity strength (Z Corr) at various time points were used to measure the connectivity fluctuations during awake and sedated states. Compared with the awake state, sedation was associated with reduced cortical connectivity fluctuations in several areas connected to the default mode network and around the perirolandic cortex with a significantly decreased correlation of connectivity between their anatomical homologues. In addition, sedation was associated with increased connectivity fluctuations ...
Journal of Neuroanaesthesiology and Critical Care, 2015
Recent advances in functional imaging of the brain have enabled a better understanding of the bra... more Recent advances in functional imaging of the brain have enabled a better understanding of the brain functions in health and disease. Amongst various functional imaging techniques, functional magnetic resonance imaging (fMRI) has been more rigorously employed in both clinical practice and in the research arena. This review will discuss the principles and techniques of fMRI, its role in understanding the pathophysiology of brain injury and finally, its clinical application in diagnosing neurological conditions and prognostication of outcome in patients with neurological disorders.
Regional differences in vascular response to anesthetic agents in brain areas with and without tu... more Regional differences in vascular response to anesthetic agents in brain areas with and without tumors have not been investigated till now. The existence of such differences may influence the regional distribution of cerebral blood flow under anesthesia. In 8 patients with frontotemporal gliomas, middle cerebral artery blood flow velocity (VMCA), pulsatality index (PI) and resistance index (RI) were determined in the normal and pathological cerebral hemispheres before and after stable nitrous oxide-halothane anesthesia. During halothane anesthesia, there was an increase in VMCA both in the normal cerebral hemisphere (69 +/- 11 to 100 +/- 38 cm/s; P = 0.05) and the hemisphere with tumor (65 +/- 17 to 83 +/- 28 cm/s; P = 0.04). A significant decrease in the pulsatality index and the resistance index was also observed in both the hemispheres (P < 0.05). The percentage changes of VMCA, PI and RI in both the hemispheres after anesthesia were not significantly different. In patients wit...
called autoregulation to secure a constant cerebral blood flow over a wide range of mean BP. Howe... more called autoregulation to secure a constant cerebral blood flow over a wide range of mean BP. However, cerebral autoregulation does not work if the brain becomes ischemic. Then, cerebral blood flow will be dependent on its mean BP. In this instance, high BP would have a beneficial effect on the maintenance of cerebral perfusion. In fact, transient arterial BP elevation is observed in 80% of ischemic stroke patients. The course of transient high BP in the acute ischemic stroke was inversely associated with the degree of recanalization in the ischemic area. When recanalization failed, high BP was sustained longer than in successfully recanalized cases. In conclusion, it would be reasonable for the anesthesiologist to consider the possibility of thromboembolism in the case of sudden high BP with no reason.
Brain tumours constitute the majority of neurosurgical conditions that present for elective opera... more Brain tumours constitute the majority of neurosurgical conditions that present for elective operations. The nature of the lesions varies from benign tumours like meningiomas and schwannomas to highly malignant tumours like glioblatomas. About 80% of the tumors are located in the supratentorial compartment and about 20% in the posterior fossa.
Patients presenting for neurosurgery may have coexisting ophthalmic diseases. During the process ... more Patients presenting for neurosurgery may have coexisting ophthalmic diseases. During the process of surgery for the primary neurosurgical condition, the ophthalmic disease may get aggravated. The following is a discussion on a few such conditions, which need to be taken care of to ensure that the success of neurosurgery is not associated with deterioration of the ophthalmic condition.
Guillain Barré Syndrome (GBS) is one of the commonest acquired immune-mediated neuropathies, ofte... more Guillain Barré Syndrome (GBS) is one of the commonest acquired immune-mediated neuropathies, often preceded by infections. Although cellular immune responses are shown to substantially account for the pathophysiology of GBS, the precise mechanistic basis of risk and disease course remains enigmatic till date. Cytokines are best known for their abilities to drive cellular immunity and inflammation through their co-ordinated actions. Data obtained from clinical and animal model studies suggest important implications of some of the cytokines in the progression and recovery of GBS. However, these studies were performed on few cytokines and small set of GBS patients, thereby lacking a complete understanding of the patterns of association of cytokines representing Th1, Th2, and Th17 responses with GBS. We studied 65 well-characterized GBS patients and 73 age- and sex-matched healthy controls. A panel of 15 cytokines representing Th1, Th2 and Th17 pathways was assayed using Multiplex Suspe...
There have been some major conceptual changes in the approach to patients with both traumatic and... more There have been some major conceptual changes in the approach to patients with both traumatic and nontraumatic cerebral injury, in recent years. These changes have their basis in a better understanding of the cerebral pathophysiology and availability of some recent monitors of cerebral function. Both traditional and modern therapeutic innovations are being subjected to extensive investigation. Evidence-based guidelines are now available for the management of traumatic brain injury. Increasing emphasis is being laid on monitoring not only intracranial pressure and cerebral perfusion pressure, but also cerebral blood flow, oxygenation and metabolism. Alternative osmotherapeutic choices are being explored. With a large pool of high quality evidence, more focused and precise therapeutic innovations are likely to emerge in near future.
... Curr Op Anesthesiol 2007; 20:331-335. 6. Sarang A, Dinsmore J. Anaesthesia for awake cranioto... more ... Curr Op Anesthesiol 2007; 20:331-335. 6. Sarang A, Dinsmore J. Anaesthesia for awake craniotomy evolution of a technique that facilitates awake neurological testing. ... Neurosurgery1998;42:219-225. 8. Anandh B, Reddy KRM, Mohanty A, Umamaheswara Rao ...
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