Block 2 Trans Flashcards
Dysraphism
A disturbance in this process results in a midline congenital abnormality
Anencephaly
The most serious neural tube defect, occurring in 1 of 1000 deliveries, is anencephaly, in which the cerebral hemispheres are absent and the rest of the brain is severely malformed. Affected fetuses are often spontaneously aborted.
spina bifida occulta
The problem may be slight and cause only a minor problem in closure of the vertebral arch. This malformation affects ∼10% of the population, usually at the fifth lumbar or first sacral vertebra, and generally causes no significant sequelae
spina bifida cystica
The dura and arachnoid membranes herniate (i.e., protrude) through the vertebral defect.
myelomeningocele
The spinal cord also herniates through the defect.
cephalocele
partial brain herniation through skull defect(cranial bifidum)
Meningocele
meningeal herniation through skull or spine defect
Brain Defects (three)
Anencephaly, Cepaholcele, and Meningocele
Spinal cord defects (three)
myelomeningocele, spina bifida cystica, and spina bifida occulta
Axonal Degneration steps
Synaptic terminal degeneration->Wallerian degeneration-> Myelin degeneration-> Scavenging of debris->chromatolysis-> retrograde degeneration->anterograde degeneration.
Chromatolysis
After axonal injury, most neuron cell bodies swell and undergo a characteristic rearrangement of organelles called chromatolysis. The nucleus also swells and moves to an eccentric position. The endoplasmic reticulum, normally close to the nucleus, reassembles around the periphery of the cell body. Chromatolysis is reversible if the neuron survives and is able to re-establish its distal process and contact the appropriate target.
Retrograde transneuronal degeneration
. Neurons that are synaptically connected to injured neurons may themselves be injured, a condition called transneuronal or trans-synaptic degeneration. If the neuron that synapses on the injured cell undergoes degeneration, it is called retrograde degeneration.
Anterograde transneuronal degeneration
If a neuron that received synaptic contacts from an injured cell degenerates, it is called anterograde degeneration. The magnitude of these transneuronal effects (retrograde and anterograde degeneration) is quite variable.
fibrillation
. If the axon is cut or dies, this trophic influence is lost and the muscle undergoes denervation atrophy…leading to muscle fibers may twitch spontaneously
fasciculations
When a motor axon is first damaged but has not yet lost continuity with the muscle fibers that it innervates, these muscle cells may twitch in unison. These small twitches can be seen under the skin
stocking pattern vs stocking and glove pattern
weakness in feet vs weakness in feet and hands
paresthesias
tingling sensation(complaint by PNS problem patients.)
Communicating hydrocephalus
commonly results from impaired absorption of CSF at the arachnoid granulation or a tumor in the subarachnoid space that impedes CSF flow. Spinal tap shows HIGH pressure and MRI shows ventricle enlargement.
Normal pressure hydrocephalus
a form of communicating hydrocephalus that is common in elderly and is caused by impaired absorptiona tumor, inflammation or blood in the CSF, but spinal tap shows NORMAL pressure. The MRI also shows enlargement just like communicating. Patients with normal-pressure hydrocephalus typically have progressive dementia, urinary incontinence, and gait disturbance, probably caused by stretching of axon pathways that course around the enlarged ventricles
Noncommunicating hydrocephalus
results from an obstruction of CSF flow inside the ventricular system.
Hydrocephalus ex vacuo
increase in ventricular size and an increase in the volume of CSF secondary to a pathological loss of brain tissue.The brain looks a lot smaller on an MRI than it should be normally
obstructive hydrocephalus
In this condition, CSF outflow from the ventricles is blocked, typically at the aqueduct of Sylvius.
cerebral edema
This swelling is frequently accompanied by a net accumulation of water within the brain that is referred to as cerebral edema. Cell swelling in the absence of net water accumulation in the brain does not constitute cerebral edema. Extra water comes from blood.
Cerebral edema treatment and symptoms
Symptoms includes headache, vomiting, altered consciousness, and focal neurological problems such as stretching and dysfunction of the sixth cranial nerve.
Treatment:Mannitol (dehydration) and Hyperventilation (decrease pH/alkalosis). Hyperventilation is the most effective means of combating the acute increase in intracranial pressure associated with severe cerebral edema. Hyperventilation causes a prompt respiratory alkalosis that is rapidly translated to an increase in the pH surrounding vascular smooth muscle, thereby triggering vasoconstriction and reduced cerebral blood flow. Thus, total intracranial blood content falls, with a rapid subsequent drop in intracranial pressure. Alternatively, the brain can be partially dehydrated by adding osmoles to the blood in the form of intravenously administered mannitol.
excitotoxicity
cycle where trauma (low o2, blood) Trauma causes low levels of ATP which stops Na/K pump. Change in membrane depolarization leads to burst of gluatamate. Astrocytes need ATP to metabolize glutamate. Thus, glutamate ends up going into BECF. Leads to neuroal problems.
In anoxia and ischemia or trauma, inhibiting Na/K pump leads to
large increases in [K+]o and [Na+]i.. These changes result in membrane depolarization, with an initial burst of glutamate release from vesicles in presynaptic terminals. Vesicular release, however, requires cATP and probably halts rapidly. The ability of astrocytes to remove glutamate from the BECF is impeded by the elevated [K+]o, elevated [Na+]i, and membrane depolarization. In fact, the unfavorable ion gradients can cause the transporter to run in reverse and dump glutamate into the BECF. The action of rising levels of extracellular glutamate on postsynaptic and astrocytic receptors reinforces the developing ionic derangements by opening channels permeable to Na+ and K+.-excititoxicity
The signs and symptoms of MS
- An optic neuritis may cause decreased visual acuity.
- An internuclear ophthalmoplegia results in an inability of the eyes to adduct on lateral conjugate gaze, reflecting a lesion in the medial longitudinal fasciculus, a white matter tract. The result is double vision.
- The Lhermitte sign is an electrical sensation that shoots down the back and into the legs when the neck is flexed.
Congenital Central Hypo-ventilation syndrome
heterozygous mutation in PHOX2B, a congential form of Ondine’s curse. Infants have breathing issues. Combination of CCHS and Hisrchprung(ENS develops abnormally) is Haddad syndrome. PHOX2B is master gene of visceral control system.
