Medical Sciences

 Brain herniation: DEFINITION: Displacement of brain tissue from one compartment to another in response to increase intracranial pressure . Intracranial compartment is divided by rigid dural folds ,if pressure in increased portion of brain are displaced across thses rigid structures,herniation leads to compromise blood supply to compressed tissue producing infarction ,additional swelling and further herniation. TYPES OF HERNIATION: 1. SUFBFALCIAN [CINGULATE] HERNIATION. 2. TRANSTENTORIAL[UNCINATE] HERNIATION. 3. TONSILLAR HERNIATION. SUBFALCIAN HERNIATION: DEFINITION: Unilateral or asymmetrical expansion of cerebral hemisphere that causes cingulate gyrus to displace under edge of falx cerebri. This herniation compress the anterior cerebral artery. TONSILLAR HERNIATION: DEFINITION: Displacement of cerebral tonsils through foremen magnum. This displacement cause compression of brain stem which comprises the vital respiratory and cardialC centers in medulla. TRANSTENTORIAL HERNI...

 CEREBRAL EDEMA: DEFINITION: Accumulation of fluid within the brain parenchyma following a generalized injury to brain. TYPES: There are two types of cerebral edema  1.Vasogenic Edema. 2.Cytotoxic Edema. VASOGENIC EDEMA: • It is defined as accumulation of extracellular fluid which occurs when blood brain barrier is disrupted. • Fluid moves from vascular compartment to extracellular spaces of brain . It is further divided into types namely 1.localized [for example after inflammation] 2.Gneralized .[for example after profuse injury] CYTOTOXIC EDEMA: • This type of edema is because of generalized hypoxia ,ischemia and exposure to certain toxin. • All these events leads to neuronal and glial cell injury which ultimately results in accumulation of fluid in extracellular spaces. CONSEQUENCES OF EDEMA: 1. Brain become edematous and soft. 2. Overfill the cranial vault. 3. Gyri become flattened. 4. Sulci become narrowed. 5. Ventricular cavities become compressed.

HYDROCEPHALUS: It is a condition more or less similar to water in the brain. DEFINITION: INCREASE IN CSF VOLUME DUE TO IMBALANCE BETWEEN PRODUCTION AND REABSORPTION OF CEREBROSPINAL FLUID. CAUSE: Impaired flow Diminished reabsorption TYPES: It is divided into two types  1.Non communicating [obstructive] hydrocephalus 2.communicating hydrocephalus  1.COMMUNICATING HYDROCEPHALUS: It is due to localized obstacle to CSF flow. In this condition, a part of the ventricle is enlarged while the remainder does not. 2.NON-COMMUNICATING HYDROCEPHALUS: It is because of reduced  CSF reabsorption. The entire ventricular system is enlarged If hydrocephalus develops before the closure of cranial suture then *head enlarges*.  If hydrocephalus after the closure of cranial suture then *no head enlargement but intracranial pressure is increased*. TREATMENT OF HYDROCEPHALUS: A most common treatment is the surgical insertion of f drainage system called a shunt. THIS SHUNT SYSTEM MOVES FLUI...

Blood Supply Of Brain The brain is supplied by two systems namely 1. Carotid system(70%) 2. Vertebrobasilar system(30%) Carotid System: Carotid system consists of an internal carotid artery, a branch of the common carotid artery. Internal carotid artery originates from the common carotid artery at the level of C4. After originating from the common carotid artery ascends upward through the carotid canal of the temporal bone then passes anterior through the cavernous sinus and enters the subarachnoid space. At lateral sulcus, ICA divides into  Anterior cerebral artery. Middle cerebral artery. Following are the branches of ICA which supplies the brain  1.ANTERIOR CEREBRAL ARTERY It curves backwards over corpus callosum and does an anastomosis with posterior cerebral artery. Cortical branches Supply the medial surface of hemisphere while central branches supply lentiform caudate and internal capsule. 2.OPHTHALMIC ARTERY  Supplies orbital structures. 3.MIDDLE CEREBRAL ARTERY R...