Pathomorph. II - CNS pathologies Flashcards
Congestive brain swelling, as distinguished from cerebral edema, is thought to represent, at least in part, an
unregulated vasodilation after trauma, and it can cause serious brain damage (even more severe than the primary injury) if not properly controlled.
difference between congestive brain swelling and cerebral edema
congestive brain swelling:
unregulated vasodilation within the brain
cerebral edema:
increased pressure following accumulation of fluid in the interstitium or intracellularly outside the circulation.
understanding of cerebral edema was advanced by Klatzo in 1967 when he proposed two distinct types:
(1) cytotoxic edema, or cell swelling, caused by increased intracellular fluid with normal vascular permeability and
(2) vasogenic edema, or tissue swelling, caused by increased extracellular fluid resulting from increased vascular permeability.
There is also a 3) hydrostatic type.
Interstitial edema also called
hydrostatic edema
Interstitial edema is characterized by
the accumulation of fluid in the extracellular space of the brain because of elevated ventricular hydrostatic pressure that accompanies hydrocephalus.
hydrostatic edema causes variable degeneration and loss of the periventricular white matter mostly through primary demyelination accompanied by loss of axons.
spongiform change is used to describe
morphologic changes in H&E stained sections that occur primarily in gray matter
spongiform changes are characterized by
small clear vacuoles of varied sizes that form in the cytoplasm of neuron cell bodies and proximal dendrites in diseases such as the transmissible spongiform encephalopathies (TSEs) and rabies encephalitis and in the processes of astrocytes that are spatially related to the affected neurons.
Status spongiosus (spongy degeneration) is a phrase whose exact meaning varies. It is defined as
multiple fluid-filled clear spaces in the white matter of H&E stained sections of the CNS and may be extracellular or intracellular.
This lesion results from the accumulation of edema fluid in the white matter secondary to a variety of causes, including cytotoxic edema, vasogenic edema, intramyelinic edema, Wallerian degeneration, and other hypoxic, toxic, and metabolic diseases.
Which immune cells can penetrate an intact blood-brain barrier?
Macrophages (monocytes) and T lymphocytes can penetrate an intact blood-brain barrier and enter the perivascular and subarachnoid spaces, transit these spaces, and return to the circulation in a role of protective immunologic surveillance of the CNS.
Dysraphia
Neural tube closure defects
Dysraphia literally means an abnormal seam, and these anomalies appear to result from defective interaction of neuroepithelium with adjacent notochordal and mesenchymal cells during closure of the neural tube in the early stages of development.
spina bifida
a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early
development in pregnancy.
Spina bifida is the vertebral counterpart of cranium bifidum.
Anencephaly literally means
an absence of the brain, but in many instances of so-called anencephaly only the rostral part of the brain (cerebral hemispheres) is absent, or very rudimentary, and to varying degrees the brainstem is preserved.
prosencephalic hypoplasia means
absence or underdevelopment of the proencephalon, or forebrain.
meningocele
A form of spina bifida in which a meningeal sac of cerebrospinal fluid protrudes through the skull or part of the vertebral column.
meningomyelocele is the same thing but includes herniation of part of the actual spinal cord in addition to the meninges.
spina bifida occulta
When spina bifida is present but there is no herniation of the meninges or spinal cord through the defect.
In this variation, there is an absence of skin over the affected vertebral arches, vertebral musculature is visible, and the dura mater and spinal cord can be seen in the spinal canal.
myeloschisis, is similar to
spina bifida except in its severe form, it results from failure of the entire spinal neural tube to close.
This lesion is therefore characterized by lack of development of the entire dorsal vertebral column.
Congenital hydromyelia is
an abnormal dilation of the central canal of the spinal cord that leads to the formation of a cavity in which CSF may accumulate.
In animals, this disorder likely results from infectious or genetic injury that results in damage to ependymal cells lining the canal.
Acquired hydromyelia is rare and is caused by obstruction of the central canal CSF flow. Causes of obstruction include infection, inflammation, and neoplasia.
In animals, the most common causes of cerebellar hypoplasia are
parvoviruses (kittens: panleukopenia virus and puppies: canine parvovirus) and
pestiviruses (calves: bovine viral diarrhea virus and piglets: classic swine fever virus).
Syringomyelia (congenital and acquired forms) is
a disorder in which a cyst forms in the spinal cord.
The cyst, a tubular cavitation called a syrinx, is not lined by ependyma and is separate from the central canal. The syrinx can extend over several spinal cord segments.
It has been suggested that pressure differences in the vertebral column cause CSF to continually move into the cyst, resulting in enlargement of the syrinx and additional compressive damage to the spinal cord.
The most common congenital malformations and developmental anomalies in veterinary medicine affecting cells that form the ependyma and choroid plexuses are (3)
hydrocephalus,
hydromyelia, and
syringomyelia.
the anomaly most likely to be caused by in utero injury following viral infection of the developing fetus
hydrocephalus
However, in some breeds (brachycephalic breeds), these disorders may have a genetic predisposition.
Parainfluenza virus can also cause the lesion in the dog.
the basic lesion of hydroencephalus is
stenosis of the mesencephalic duct that results in the development of noncommunicating hydrocephalus.
In the dog, closure of the mesencephalic duct can be incomplete.
Transmissible Spongiform Encephalopathies are caused by
proteinaceous infectious particles (prions) that (1) are composed of an abnormal isoform of a normal cellular protein, the prion protein and (2) resist inactivation by procedures that degrade nucleic acids and proteins (i.e., heat, ultraviolet irradiation, and strong enzymes).
Prion diseases are fatal. The adaptive immune system does not recognize prions as foreign; therefore no immunologic protection develops.
the prototype prion disease.
Ovine spongiform encephalopathy (scrapie)
Spongiform encephalopathies occur through
horizontal transmission (e.g. scrapie-infected sheep offal fed to cows [BSE] has been proposed)
and through an inherited mutation of the normal human prion gene (e.g. parent to child), resulting in the spontaneous formation of PrPSc.
In animals, the primary route of infection appears to be through horizontal transmission.
