Chapter 16: Disorders of Brain Function – Stroke & Injury

Disorders of Brain Function – Stroke & Injury delves into the pathology and clinical manifestations of various disorders affecting brain function, beginning with the fundamental mechanisms of injury such as hypoxic and ischemic injury, which can range from focal to global, and excitotoxic brain injury involving uncontrolled stimulation by neurotransmitters like glutamate. A central theme is the critical dynamics of the cranium, including the Monro–Kellie hypothesis concerning intracranial volume equilibrium, the dangers of increased intracranial pressure (ICP), and the resultant tissue displacement known as brain herniation. The text differentiates types of swelling, such as vasogenic and cytotoxic cerebral edema, and explores fluid accumulation disorders like hydrocephalus. Traumatic brain injuries are categorized into immediate primary injuries (e.g., contusions, concussions) and secondary damage, focusing specifically on life-threatening vascular complications like epidural, subdural, and intracerebral hematomas. The chapter extensively covers cerebrovascular disease, contrasting ischemic strokes—often preceded by transient ischemic attacks (TIAs) and involving the ischemic penumbra—with severe hemorrhagic strokes, including aneurysmal subarachnoid hemorrhage (SAH) and bleeding from Arteriovenous Malformations (AVMs). Clinical outcomes are detailed, emphasizing motor deficits, speech disturbances (aphasia), and cognitive syndromes (hemineglect). Furthermore, CNS infections like meningitis and encephalitis are discussed based on causative organisms and distinct clinical findings, such as nuchal rigidity. Lastly, seizure disorders are thoroughly classified into focal (aware or impaired awareness) and generalized types (like tonic–clonic or absence seizures), along with the medical emergency of status epilepticus and the necessary treatment protocols involving anticonvulsant medications or surgery.