Chapter 14: Nervous System Alterations

The nervous system's basic architecture comprises neurons as functional units and neuroglia serving supportive roles, with blood flow to the brain representing 15 to 20 percent of cardiac output delivered through the carotid and vertebral arterial systems that converge at the Circle of Willis. The brain's exclusive dependence on glucose and aerobic metabolism creates extreme vulnerability to hypoxia, with irreversible cellular damage occurring within minutes of oxygen deprivation. Cerebral autoregulation maintains stable blood flow across varying blood pressure ranges through adaptive changes in vessel diameter, while the blood-brain barrier selectively permits passage of essential molecules like glucose, oxygen, and carbon dioxide while blocking harmful substances. Accurate neurologic assessment forms the foundation of early deterioration detection, utilizing standardized tools such as the Glasgow Coma Scale and FOUR score to quantify consciousness and brainstem function, while pupillary responses and motor strength evaluation reveal progression of intracranial pathology. Elevated intracranial pressure represents a medical emergency when sustained above 20 millimeters of mercury, potentially precipitating herniation and requiring aggressive intervention through head elevation, neck alignment, activity spacing, and pharmacologic measures including osmotic diuretics and CO2 regulation. Traumatic brain injury encompasses both primary mechanical damage and secondary biochemical cascades, manifesting as skull fractures and intracranial hematomas with characteristic clinical presentations including lucid intervals and progressive neurologic decline. Acute ischemic stroke, accounting for the majority of cerebrovascular events, requires thrombolytic therapy administration within a narrow therapeutic window, while hemorrhagic strokes result from vessel rupture and demand distinct management approaches. Seizure emergencies, particularly status epilepticus, necessitate immediate airway protection and benzodiazepine administration to prevent ongoing neuronal injury. Central nervous system infections such as bacterial meningitis present as medical urgencies with distinctive clinical signs, and spinal cord injury triggers cascading edema and inflammation leading to temporary neurologic shutdown, with autonomic dysreflexia representing a particularly dangerous complication in high cervical injuries.