NEURO PATHOLOGY

Neurons

What is the principal functional unit of the CNS?

Acute or Chronic

What are the two categories of neuronal reactions to injury?

Red Neurons

What is another name for neurons in acute injury?

Degeneration

What is the term for the chronic reaction of neurons to injury?

Shrinkage, pyknosis, and intense eosinophilia

What are the three key morphologic features of acute neuronal injury?

Metabolic buffers, detoxifiers, and CNS repair

What are the three primary functions of astrocytes?

Reactive Gliosis

What is the specific reaction of astrocytes to CNS injury?

Hypertrophy, hyperplasia, and increased GFAP expression

What are the three morphologic features of reactive gliosis?

GFAP

Which protein expression increases in reactive gliosis?

Oligodendroglia

Which CNS cells produce myelin?

Schwann cells

Oligodendroglia are the CNS equivalent of which peripheral nervous system cells?

PML or MSA

In which two diseases do inclusions appear in oligodendroglia?

Small round nuclei with clear halos

What describes the fried egg appearance of oligodendroglia?

Microglia

Which cells are the resident macrophages and antigen-presenting cells of the CNS?

Rod cells, nodules, and neuronophagia

What are the three reactions of microglia to injury?

Elongated nuclei

What is the key morphologic feature of microglial rod cells?

Aggregates around necrosis

What is the key morphologic feature of microglial nodules?

Ependymal Cells

Which cells line the ventricles and handle substance transport?

Ependymal granulations

What is the reaction of ependymal cells to injury?

Disruption of lining paired with subependymal astrocyte proliferation

What are the morphologic features of ependymal granulations?

Raised Intracranial Pressure or ICP

What causes the displacement of brain tissue across rigid dural reflections?

Edema, hydrocephalus, or lesions

Name three things that cause mass effects leading to brain herniation.

Subfalcine

Which herniation involves the cingulate gyrus?

Cingulate gyrus

Which structure is displaced under the falx in subfalcine herniation?

Falx

Under what structure is the cingulate gyrus displaced in subfalcine herniation?

Anterior Cerebral Artery or ACA

Which artery may be compressed as a consequence of subfalcine herniation?

Transtentorial or Uncal

Which herniation involves the medial temporal lobe?

Medial temporal lobe

Which structure is displaced against the tentorium in uncal herniation?

Tentorium

Against what structure is the medial temporal lobe displaced in transtentorial herniation?

Brainstem

What structure is compressed in transtentorial herniation?

Secondary Duret hemorrhages

What is a pathologic consequence of transtentorial herniation besides brainstem compression?

Tonsillar

Which herniation involves the cerebellar tonsils?

Cerebellar tonsils

Which structures are displaced through the foramen magnum in tonsillar herniation?

Foramen magnum

Through which opening are cerebellar tonsils displaced in tonsillar herniation?

Vital medullary centers

What is compressed in tonsillar herniation?

Life-threatening

What is the clinical significance of tonsillar herniation?

Failures in neural tube closure or neuronal migration and generation

What are the two main causes of developmental malformations of the CNS?

Anencephaly

Which neural tube defect involves the absence of the brain and calvarium?

Area cerebrovasculosa

What is the name of the remnant tissue found in anencephaly?

Myelomeningocele

Which neural tube defect involves the extension of CNS tissue and meninges through a vertebral defect?

Holoprosencephaly

Which forebrain anomaly involves incomplete separation of cerebral hemispheres?

Cerebral hemispheres

Which structures fail to separate completely in holoprosencephaly?

Cyclopia

What specific physical abnormality can be caused by holoprosencephaly?

Lissencephaly

Which forebrain anomaly is characterized by a reduction in gyri?

Agyria

What is the term for the reduction in gyri seen in lissencephaly?

Type 1

Which type of lissencephaly results in a smooth surfaced brain?

Joubert Syndrome

Which posterior fossa anomaly involves vermis hypoplasia?

Vermis hypoplasia

What cerebellar finding is characteristic of Joubert Syndrome?

Molar tooth sign

What is the characteristic appearance of elongated superior cerebellar peduncles in Joubert Syndrome?

Elongated superior cerebellar peduncles

Which anatomical change creates the molar tooth sign in Joubert Syndrome?

Anatomic location and magnitude of physical forces

What two factors determine the consequences of CNS trauma?

Concussion

Which injury type involves a change in head momentum?

Transient neurologic dysfunction without structural consequences

What are the clinical features of a concussion?

Contusion

Which injury type is caused by direct kinetic energy transmission?

Wedge-shaped bruises

What is the gross appearance of a brain contusion?

Plaque jaune or yellow patches

What do old contusion lesions show?

Diffuse Axonal Injury

Which injury results from mechanical forces altering axoplasmic flow?

Widespread asymmetric axonal swellings

What is the pathologic hallmark of diffuse axonal injury?

Silver stains

Which stains are used to highlight axonal swellings in diffuse axonal injury?

Epidural Hematoma

Which injury involves the rupture of a meningeal artery?

Middle Meningeal Artery or MMA

Which specific artery is usually ruptured in an epidural hematoma?

Arterial blood between dura and skull

Where is the blood located in an epidural hematoma?

Skull fractures

Epidural hematomas are often associated with what type of bone injury?

Subdural Hematoma

Which injury involves damage to bridging veins?

Bridging veins

Which specific vessels are damaged in a subdural hematoma?

Venous blood in the subdural space

What type of blood is found in a subdural hematoma and where is it located?

Dura remains attached to the skull

What is the state of the dura in a subdural hematoma?

Stroke

What is designated when neurologic signs arise from vascular mechanisms and persist for more than 24 hours?

24 hours

How long must signs persist to be classified as a stroke?

Embolic Infarct

What is the most common category of stroke?

Distant sources like cardiac mural thrombi

What is the typical cause of an embolic infarct?

Blood vessel branches

Where do embolic infarcts tend to lodge?

Thrombotic Infarct

Which stroke type is typically caused by vulnerable atherosclerotic plaques?

Carotid bifurcation or origin of the MCA

Where are thrombotic infarcts commonly located?

Watershed Infarct

Which infarct is caused by a generalized reduction of perfusion?

Cardiac arrest

What is a typical cause of generalized perfusion reduction leading to a watershed infarct?

Border zones between arterial territories

Where specifically do watershed infarcts occur?

ACA/MCA

Give an example of a border zone between arterial territories where watershed infarcts occur.

Lacunar Infarct

Which infarct type is caused by arteriolosclerosis from hypertension?

Hypertension

What condition causes the arteriolosclerosis seen in lacunar infarcts?

Less than 15mm

What is the typical size of a lacunar infarct cavitary lesion?

Basal ganglia or brainstem

Where are lacunar infarcts usually found?

6 to 12 Hours

At what time post-insult is there little change visible gross morphology of an infarct?

Red neurons and cytotoxic/vasogenic edema

What are the microscopic features of an infarct 6 to 12 hours post-insult?

Eosinophilic necrosis

What is the microscopic description of red neurons?

Up to 48 Hours

When does tissue appear pale, soft, and swollen after a non-hemorrhagic infarct?

Infiltration of neutrophils

What microscopic event begins at vessel edges up to 48 hours post-infarct?

2 to 10 Days

When does the brain become gelatinous and friable following an infarct?

Phagocytic macrophages stuffed with myelin products

Which cells predominate microscopically 2 to 10 days after an infarct?

10 to 21 Days

When does tissue liquefaction occur following an infarct?

Fluid-filled cavity surrounded by residual gliosis

What is the microscopic appearance of an infarct 10 to 21 days post-insult?

Hematogenous spread, direct implantation, local extension, or the PNS

Name four ways microbes enter the CNS.

TB Meningitis

Which infection is caused by M. tuberculosis?

Basal gelatinous exudate

What diagnostic hallmark of TB meningitis encases cranial nerves?

Cranial nerves

Which structures are encased by the basal gelatinous exudate in TB meningitis?

HSV-1 Encephalitis

Which infection is caused by Herpes Simplex Virus 1?

Bitemporal necrotizing encephalitis

What is the clinical manifestation of HSV-1 encephalitis?

Cowdry Type A inclusions

What diagnostic inclusion is associated with HSV-1 encephalitis?

Rabies

Which infection is caused by the Rabies Virus?

Negri bodies

What diagnostic hallmark is found in pyramidal hippocampal neurons and Purkinje cells during rabies?