Medical brain notes 15

  INFECTIONS Meningitis  is inflammation of the 2 inner meningeal layers, the pia and the arach-noid. Acute aseptic (viral) meningitis  is caused by leptomeningeal inflammation due to   viruses (enterovirus most frequent); the inflammation produces a lymphocytic infiltration of leptomeninges and superficial cortex. Patients present with fever, signs of meningeal irritation, and depressed consciousness. Mortality is low. Viral meningitis carries a better prognosis than bacterial meningitis. Acute viral meningitis is the most common neurologic symptom associated with primary HIV infection; it presents around the time of seroconversion with an acute confusional state. Symptoms resolve after 1 month with supportive care.   Acute purulent (bacterial) meningitis  is a purulent leptomeningeal inflammation.   •           Streptococcus pneumoniae is the most common cause of meningitis in infants, young children, and ...

  CEREBROVASCULAR DISEASE   Cerebrovascular disease  is the third most frequent cause of death in industrialized   countries, and it is the leading cause of serious disability in the United States. Risk factors are similar to coronary artery disease.   •           Global cerebral ischemia  (diffuse ischemic encephalopathy) is caused by a fall   in blood flow to the brain, due to processes such as shock, cardiac arrest, and hypotensive episodes. While the entire brain can be damaged, some regions have selective vulnerability, including Purkinje neurons, hippocampus, CA1 (Sommer sector), and pyramidal neurons of cortex. The pathology often includes infarcts in watershed areas, cortical laminar necrosis, and diffuse ischemic necrosis of neocortex. Global cerebral ischemia may lead to brain death.   •           Transient ischemic attack  (TIA) is due to smal...

  Cranial Cavity and Brain Concussion  is mild traumatic brain injury with a transient loss of brain function.   The trauma is commonly due to a change in the momentum of the head (impact against a rigid surface). Concussion causes loss of consciousness and reflexes, tem-porary respiratory arrest, and amnesia for the event. The pathogenesis is uncertain. Parenchymal injuries may or may not be evident at autopsy Contusions  are bruises of the brain tissue. Common sites of injury include crests of   orbital gyri in frontal and temporal poles, in addition to  coup  (site of injury) and  contrecoup  (site diametrically opposite) injuries. Coup and contrecoup develop when   the head is mobile at the time of impact.   •           Acute contusion  is characterized by hemorrhage of brain tissue in a wedge-shaped area.   •           Subacute c...

  DEVELOPMENTAL ABNORMALITIES AND PERINATAL BRAIN INJURY   Neural tube defects  are the most common developmental central nervous system   abnormalities. They result from defective closure of the neural tube, and they tend to occur at the 2 extremities of the neuraxis. Folate deficiency is involved in the pathogenesis.   •           Anencephaly  is the absence of cranial vault. It is incompatible with life; babies   die soon after birth.   •           Neural tube defects of the spinal cord  may take a variety of forms. Significant   defects lead to paraplegia and urinary incontinence from birth.   •           Spina bifida occulta  is a bony defect of the vertebral arch.   •           Meningocele  is a bony defect with outpouching of meninges...