Path 2 - Neuro 1

pbhati17's version from 2017-03-04 16:25

Intro: Unique Histopathologic rxns in nervous tissue

Question Answer
Chromatolysis (what is this/what's happening?)Pale areas in neuronal cytoplasm from dispersion of Nissl’s substance (rER) (Chromatolysis is the dissolution of the Nissl bodies in the cell body of a neuron. It is an induced response of the cell usually triggered by axotomy, ischemia, toxicity to the cell, cell exhaustion, virus infxns & hibernation in lower vertebrates.)
Demyelination (what is this/what's happening? how can you detect it? is this fixable?)This is a loss of myelin w/ preservation of the cell body & axon. You can tell this is happening bc myelin progressively loses it affinity for myelin stains so it looks like an unstained area surrounding the axon. This leads to disruption & phagocytic removal of myelin. There is a little hope tho, myelin may be regenerated by Schwann cells in the PNS
Wallerian degeneration → what is this/how does it happen? Is this fixable?This is the destruction of axon & myelin sheath following trauma or toxic injury. It may regenerate in the PNS
What is Satellitosis?Accumulation of glial cells (mainly microglia) around damaged neurons
What is Neuronophagia?Macrophagic phagocytosis of necrotic neurons
What is going on in Perivascular cuffing? What are the 2 types?This happens when there is an accumulation of leukocytes in perivascular (Virchow-Robin) spaces.
There is:
(1) Polymorphonuclear (suppurative)
(2) Mononuclear (non-suppurative) (note: type of cell can hint towards most likely causative agent or pathogen. if bact-neutrophils, eosino-allergic/parasite, lymphocytes-viral)
What is Malacia?Softening & liquefaction of nervous tissue from necrosis of neurons & glial cells
Neuronal inclusion bodies → what are the 2 types?Intracytoplasmic & intranuclear
Neuronal inclusion bodies → intranuclear → what are the 2 kinds & how are they different?(1) "Cowdry's Type A": These are eosinophilic, are usually SINGLE & DISPLACE THE NUCLEOLUS! also surrounded by a clear halo w/ margination of chromatin on the nuclear membrane. SPECIFIC FOR VIRAL INFXNS. (As the big #1)
(2) "Cowdry's Type B": LESS SPECIFIC, also eosinophilic, they are often multiple & nucleolus is not displaced
Neuronal inclusion bodies → intracytoplasmic → what is a specific type that is specific for Rabies? What do they look like?NEGRI BODIES! They are eosinophilic w/ internal granules which stain purple w/ methylene blue & basic fuchsin
Neuronal inclusion bodies → intracytoplasmic → what are 2 DDX DIAGNOSES for intracytoplasmic inclusion bodies? (That aren't Rabies) (Explain them a little)(1) There are tiny spherical bodies w/o a limiting membrane are encountered in the neurons of nonrabid animals. They are more eosinophilic & are seen in seen in the cat, dog, fox, skunk & laboratory mice
(2) "Feline inclusions" have been described in the neurons of normal cats
Intracytoplasmic neuronal vacuolization → when do you see this?See in chronic nerve cell changes (degeneration)

Congenital anomalies

Question Answer
Whats the fancy word for Neural tube closure defects?Dysgraphia
What are the 4 conditions associated w/ neural tube closure defects? (Dysgraphia)(1) Anencephaly & Prosencephalic Hypoplasia
(2) Meningoencephalocele & Cranium Bifidum
(3) Meningomyelocele & Spina Bifida
(4) Hydromyelia
Closure of the neural tube occurs at 4 distinct locations (closure initiation sites) in the embryo. Disruption of this process at these sites leads to site-specific dysraphias.... Sites I, II, III, IV happen from which neuropores?Site I= posterior neuropore
Sites II, III, IV are the anterior neuropore
What is Anencephaly? Describe itTotal absence of the entire brain (rare)...more commonly, the term is used even tho a small portion of the brain persists (often the medulla is present & occasionally some of the mesencephalon). The lesions are absence of the cerebral hemispheres + failure of forebrain fusion
What is Prosencephalic hypoplasia? (What is the prosencephalon?) Who gets this? What is the etiopathogenesis?(Prosencephalon is the 1st sacular diverticulation which later separates, aka forebrain) This condition is common in pigs & lambs. Etiopathogenesis: failure of bilateral separation of the primitive single telencephalic cavity into 2 hemispheres
What are the lesions associated w/ Prosencephalic hypoplasia? What condition does this usually associate w/?You will see a a single central ventricle! Absence of the longitudinal fissure, the corpus callosum, olfactory bulb & optic tracts, brain stem & cerebellum are normal. This is associated w/ cyclopia
What is a (meningio) Encephalocele? (Defect where? related to what disorder? related to what anatomical feature? where is it usually located?)This is a protrusion of the brain (along w/ the meninges) through a defect in the cranium (cranium bifidum). It is related to suture lines (the lines where the plates come together in the skull) & is almost ALWAYS median. The skin forms the hernia sac w/ the brain & meninges inside.
What is a Meningocele?Protrusion of the meninges from skull, similar to encephalocele, but fluid-filled w/ no brain inside
What is spina bifida?Absence of the dorsal portions of the vertebrae (imprecise term) GOOGLE SAYS: A birth defect in which a developing baby's spinal cord fails to develop properly
Explain Spina bifida w/ meningomyeloceleSpina bifida is incomplete development of the spinal cord & myelomeningocele is when the SC & meninges then protrude is a specific type of spina bifida. INTERNET SAYS: Myelomeningocele is a neural tube defect in which the bones of the spine do not completely form, resulting in an incomplete spinal canal. This czs the spinal cord & meninges (the tissues covering the spinal cord) to protrude from (stick out of) the child's back.


Question Answer
What is Hydromyelia?It is a simple dilatation of the central canal of the spinal cord. It is connected w/ the central canal & is lined by ependymal cells. INTERNET SAYS: is an abnormal widening of the central canal of the spinal cord, which creates a small space that can fill w/ cerebral spinal fluid (CSF).
Neuronal migration disorders → Defects in cerebral corticogenesis → Lissencephaly. What is this aka? What is going on w/ this? Who does this occur in?AKA AGYRIA. in this condition the brain's convolutions almost entirely absent... i.e., absence of primary gyri (lack of folds in the brain). Brain surface is perfectly smooth ("smooth brain") & there is an excessively thin cerebral cortex. This defect is due to defective neuronal migration. It occurs in Lhasa Apso dogs
Encephaloclastic (destructive) defects → Porencephaly. What is this? What part of the brain is involved?This is when cysts or cavities are in the wall of the cerebral hemisphere (Cystic cavitation of the brain). Typically involves the white matter of the cerebral hemispheres & the cyst communicates w/ the subarachnoid space & or lateral ventricle.
What is the etiopathogenesis of porencephaly?(When cysts/cavities are in the wall of the cerebral hemisphere) This is a congenital anomaly, but is also associated w/ prenatal viral infxns (remnants of destructive lesions) from infxns like Border Dz, hairy shaker Dz, BVD
Encephaloclastic (destructive) defects → Hydrocephalus: What are the 2 types of this?Congenital hydrocephalus, Acquired hydrocephalus
What is Hydrocephalus?Abnormal accumulation of fluid in the ventricles of the brain & sub-meningeally. If can be congenital or acquired. NOTE: This is PHYSIOLOGICAL (i.e. normal) in the EARLY FETUS.
When is hydrocephalis no thang? (2)(1) It is physiological (normal) in the early fetus
(2) Internal hydrocephalus (fluid accumulates in the ventricles) is common in the brachycephalic breeds & in aged animals
What is internal hydrocephalus?Fluid accumulates in the ventricles
What is external hydrocephalus?Fluid accumulates in the sub-arachnoid space
What is communicating hydrocephalus?When fluid accumulates in both the ventricles & in the sub-arachnoid space
Describe the circulation of CSF1st it is produced by the choroid plexuses, then it flows from the lateral ventricles through the foramen of Monro to the 3rd ventricle and, via the aqueduct of Sylvius, to the 4th ventricle. The exit of fluid from the ventricular system is via the foramen of Luschka to the subarachnoid space (pic on slide 53)
What are the 3 possible pathogenesis of hydroencephalus?(1) ↑ production of CSF
(2) Obstruction of the normal flow of CSF
(3) Defective absorption of CSF
Congenital hydrocephalus → what is the etiology of the CONGENITAL form? (5) (When would obstruction develop?)(1) Idiopathic
(2) Intra-uterine viral infxns
(3) Nutritional deficiencies
(4) Familial in pigs
(5) Malformation of the cranium.
OBSTRUCTION: obstruction mostly develops as the consequence of a periductal gliosis of the aqueduct of Sylvius
Congenital hydrocephalus → who is this most common in? What are the lesions like?More common in dogs, calves & foals. The lesions are dilated ventricles or the duct system & a dome-shaped, thin-boned & enlarged cranium (the big head horse & the inflated dog & cow were full of themselves)
**Acquired hydrocephalus → which type of hydro. Is this usually (internal, external or communicating)? What is causing this? How does it appear?Seen most commonly as an internal hydrocephalus. It is a progressive condition. There is obstruction of flow due to an accumulation of & organization of exudate, but no malformation of the cranium!
Acquired hydrocephalus → etiopathogenesis? (5)(1) Bacterial meningitis (in this case, most cases are acutely fatal)
(2) Granulomatous meningitis (TB, Cryptococcosis, FIP)
(3) Intracranial neoplasms
(4) Parasitic cysts
(5) Cholesteatoma (cholesterolinic granuloma) in horses


Question Answer
Acquired hydrocephalus → what are the lesions? Who might be difficult to see this condition in?Pressure atrophy of the septum pellucidumand hippocampus, ventricular dilatation, pressure atrophy of cerebrocortical white matter. (May be difficult to observe in neonates where the brain is soft & easily collapses)
What is Hydranencephaly? (HYDRA NOT HYDRO)Complete or almost complete absence of the cerebral hemispheres in a cranium of normal size & formation
Hydranencephaly → what is Leptomeninges? What’s going on w/ it in hydrAencephaly? What's going on w/ the epedenyma?The Leptomeninges are the pia mater & the arachnoid considered together as investing the brain & spinal cord. In hydraencephaly, they remain in their normal position, which form sacs enclosing CSF (the fluid occupies space normally occupied by the parenchyma). Since the cerebral hemispheres are totally or almost gone, this means there are large Cystic spaces or sacs. The epedenyma is absent (thin epithelium-like lining of the ventricular system of the brain & the central canal of the spinal cord.)
Hydraencephaly → who does this occur most commonly in?Most commonly in calves in association w/ cerebellar hypoplasia. In lambs of ewes vxd during pregnancy for bluetongue (a waterbed? no a waterHEAD make of leather & wool)
Hydranencephaly is the residual lesion of___?The residual lesion of full-thickness necrosis of the cerebral hemisphere associated w/ fetal viral infxns (Akabane, Bluetongue, Rift Valley Fever, Wesselsbron Dz, BVD, Border Dz)
Malformations of the cerebellum → Cerebellar hypoplasia: Who does this happen in most commonly? What usually czs this (general)Usually occurs in common in cats, dogs & calves, usually following intra-uterine viral infxns. CAN be inherited
Cerebellar hypoplasia → This is usually czd by intra-uterine viral infxns. List 5 common viral etiologies(1) Feline panleukopenia → ataxia in kittens
(2) BVD/MD (bovine viral diarrhea/mucosal dz ← chronic form)
(3) Hog cholera Vx\
(4) Border Dz (hairy shaker dz, pestivirus)
(5) Rat virus, hamster osteolytic virus
Cerebellar hypoplasia → what do the gross lesions of this look like? (2)Can look NORMAL in size or appearance (only microscopic probs), OR it can just be a small stump of tissue
Cerebellar hypoplasia → what do the microscopic lesions of this look like?Loss of purkinje cells (class of GABAergic neurons located in the cerebellum), The granular layer is narrowed & deficient in cells. The molecular layer is usually normal.
**What is Syringomyelia? How common is it? Who does it usually occur in?Tubular cavitation (cavities in it) (syrinx) of the spinal cord extending over several segments. This is rare, except in the Weimaraners (a SYRINGE injected a HUGE CAVITY of fluid into the Weimaraners spine)
How does Syringomyelia present clinically?Affected dogs are unable to completely extend the hind limbs, crouched posture, hind limbs are moved together in progression (symmetrical hopping gait), lesions are not observed until about the 8th month of life
What does Syringomyelia look like grossly? Microscopically?GROSS: Cavitations in the lumbar segments. The cavitations may or may not be visible to the naked eye
MICROSCOPICALLY: Cavitations in the central gray matter (dorsal & lateral to the central canal) → the cavitation is not lined by ependymal cells
*What is the lesion that both CONGENITAL & ACQUIRED hydroencephalus have? What is the major difference?BOTH HAVE LAT VENTRICULAR DISTENTION!! However congenital will have an ENLARGED CRANIUM & acquired will NOT
*HYDRANENCEPHALY vs PORENCEPHALY → which is MORE SEVERE? What is the major defect in hydra, what is the major defect in poren?HYDRA IS WAY MORE SEVERE, BC THERE IS ABSENCE OF CEREBRAL HEMISPHERES. POREN on the other hand is CYSTS (white matter defect)
*Which viruses cz cerebellar hypoplasia?Feline panleukopenia
BVD in cattle
Herpesvirus in dogs

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