Porth's Essentials of Pathophysiology, 4e

natomically and functionally, the brain is the most complex structure in the body. It controls our abil- ity to think, our awareness of things around us, and our interactions with the outside world. Signals to and from various parts of the body are controlled by very specific areas in the brain. Therefore, the brain is much more vulnerable to lesions that in other organs might produce no significant effects. For example, an isolated renal infarct would not be expected to have a significant effect on kidney function, whereas an infarct of compa- rable size in a specific area of the brain could produce complete paralysis on one side of the body. Alterations in brain function can result from injury, cerebrovascu- lar disease, infection, tumors, disruptions in electrical activity (seizures), or impairment of memory (impaired cognition or dementia). Brain Injury The brain is protected from external forces by the rigid confines of the skull and the cushioning afforded by the cerebrospinal fluid (CSF). The metabolic stability required by its electrically active cells is maintained by a number of regulatory mechanisms, including the blood– brain barrier and autoregulatory mechanisms that ensure adequate blood supply. Mechanisms of Brain Injury Injury to brain tissue can result from a number of condi- tions, including trauma, infections, tumors, and degen- erative processes. Brain damage resulting from these disorders involves several common pathways, including hypoxia and ischemia, the effects of excitatory amino acid injury, and cerebral edema. In many cases the mechanisms are interrelated. Hypoxic and Ischemic Injury The brain relies on the ability of the cerebral circula- tion to deliver sufficient oxygen for its energy needs. Although the brain makes up only 2% of the body Disorders of Brain Function 37 C h a p t e r A

Brain Injury

Mechanisms of Brain Injury

Hypoxic and Ischemic Injury Excitatory Amino Acid Injury Cerebral Edema Increased Intracranial Pressure, Herniation, and Hydrocephalus

Brain Herniation Hydrocephalus Traumatic Brain Injury

Contusions Hematomas Concussions Diffuse Axonal Injury Manifestations of Diffuse Brain Injury Consciousness Other Manifestations of Deteriorating Brain Function Cerebrovascular Disease The Cerebral Circulation Regulation of Cerebral Blood Flow Stroke (Brain Attack) Ischemic Stroke Hemorrhagic Stroke Acute Stroke Management Poststroke Management and Deficits Intracranial Hemorrhage Aneurysmal Subarachnoid Hemorrhage Arteriovenous Malformations Infections Meningitis Acute Bacterial Meningitis Viral Meningitis Encephalitis Brain Tumors Types of Tumors Neuroglial Tumors Medulloblastomas Meningiomas Primary Central Nervous System Lymphomas Metastatic Tumors Manifestations Diagnosis and Treatment Seizure Disorders Provoked Seizures Febrile Seizures Unprovoked (Epileptic) Seizures Focal Seizures Generalized Seizures Diagnosis and Treatment Antiepileptic Drug Therapy Surgical and Neurostimulation Therapy Generalized Convulsive Status Epilepticus

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