Neuro

Question 1

What are the two major functional elements of peripheral nerves?

Answer 1

1. Axonal processes

2. myelin sheaths

Question 2

Describe morphological changes associated with axonal degeneration

Answer 2

Axonal neuropathies are caused by direct injury to the axons themselves. Degeneration of axon distal to the injury. Decreased axon density, causes decrease in strength/amplitude of nerve impulses.

Question 3

Describe morphological changes associated with demyelination.

Answer 3

Damage to Schwann cells/myelin resulting in slow nerve conduction. No change in density of axons. Areas of demyelination may have repairs underway.

Question 4

Describe polyneuropathies

Answer 4

1. Usually affect peripheral nerves in a symmetric, length dependent fashion.
2. Axonal loss is typically more pronounced in the distal segments of longest nerves.
3. Loss of sensation and paresthesia starts in toes and spreads upwards.
4. “stocking-and-glove distribution” by the time sensory changes reach level of knees, hands are also affected.
5. Associated with toxic and metabolic damage.

Question 5

Describe mononeuritis multiplex

Answer 5

1. Damage randomly affects individual nerves (e.g. right radial nerve palsy and wrist drop, and later left foot drop)
2. Often caused by vasculitis.

Question 6

Describe simple mononeuropathy

Answer 6

Most commonly result of traumatic injury, or infections such as lyme disease

Question 7

Define Guillain-Barre syndrome

Answer 7

1. Rapidly progressive acute demylinating disorder affecting motor axons, resulting in ascending weakness.
2. Inflammatory peripheral neuropathy.
3. Can cause death from failure of respiratory muscles.
4. Triggered by vaccination or infection (EBV, Zika, Campylobacter jejuni)

Question 8

Define myasthenia gravis

Answer 8

1. Autoimmune disease with fluctuating muscle weakness that is caused by antibodies that target the nueromuscular junction.
2. Antibodies block, alter, or destroy postsynaptic Acetycholine receptor.
3. S/S include can include ptosis and diplopia

Question 9

What is cerebral edema?

Answer 9

Accumulation of excess fluid within the brain.

1. Vasogenic: disruption in blood-brain-barrier, fluid shifts from vascular compartment to extracellular spaces.
2. Cytotoxic: Increase in intracellular fluid due to neuronal and glial cell injury

Question 10

What is hydrocephalus?

Answer 10

Increase in CSF volume in ventricular system due to impaired flow or decreased reabsorption.

1. Communicating: entire ventricular system is involved.
2. Noncommunicating: localized obstacle to CSF flow, only portion of ventricles enlarged.

Question 11

What is brain herniation?

Answer 11

Displacement of brain tissue from one compartment to another in response to increased intracranial pressure.

1. Subfalcine (cingulate): unilateral or asymmetric expansion of cerebral hemisphere displaces cingulate gyrus.
2. Transtentorial (cingulate): medial aspect of temporal lobe is compressed against free margin of tentorium.
3. Tonsillar herniation: Displacement of cerebellar tonsils through foramen magnum, causes brain stem compression that can be fatal.

Question 12

Describe two mechanisms by which the brain may be deprived of oxygen.

Answer 12

1. Functional hypoxia: low partial pressure of oxygen, impaired oxygen-carrying capacity, or toxin interfering with oxygen use.
2. Ischemia: secondary to hypoperfusion, caused by hypotension, or vascular obstruction

Question 13

Describe mechanism and clinical outcomes of global cerebral ischemia.

Answer 13

1. Mechanism: generally occurs from drop of systolic pressure below 50 mm Hg.
2. Clinical outcomes: mild (post-ischemic confusional state) or severe (brain death)

Question 14

What is focal cerebral ischemia?

Answer 14

Cerebral arterial occlusion, first leads to focal ischemia and then to infarction in the distribution of compromised vessel.

Question 15

Describe embolic infarctions.

Answer 15

1. Cardiac mural thrombi are frequent source.
2. Myocardial dysfunction, valvular disease, and a-fib are predisposing factors.
3. Thromboemboli arise in arteries from atheromatous plaques in carotid arteries or aortic arch.
4. Tend to lodge where vessels branch or in areas of stenosis (middle cerebral artery most common).

Question 16

Describe thrombotic occlusions.

Answer 16

1. Superimposed on atherosclerotic plaques.
2. Common sites: carotid bifurcation, origin of middle cerebral artery, either end of basilar artery.
3. Lacunar infarcts: small infarcts only a few millimeters caused by long-standing hypertension.

Question 17

Describe nonhemorrhagic infarcts

Answer 17

1. Result from acute vascular occlusions.

2. Tissue liquefies and leaves a fluid filled-cavity, gradually expands.

Question 18

Describe Hemorrhagic infarcts

Answer 18

1. Reperfusion of ischemic tissue through collaterals or after dissolution of emboli.
2. Manifest as petechial hemorrhages.

Question 19

What are 3 main causes of intracranial hemorrhages?

Answer 19

1. hypertension and diseases of vascular wall
2. Structural lesions such as arteriovenous or cavernous malformations
3. tumors

Question 20

What is Primary intraparenchymal hemorrhage?

Answer 20

1. Rupture of small intraparenchymal vessel, underlying cause of hypertension or cerebral amyloid angiopathy.
2. Extravenous blood compresses parenchyma, shows as cavity with brown rim

Question 21

What is Subarachnoid hemorrhage and saccular (berry) aneurysms?

Answer 21

1. Rupture of a saccular aneurysm.
2. Location: anterior circulation near major arterial branch points.
3. Morphology: Thin walled outpouching of artery ruptures releasing blood into subarachnoid space, substance of brain, or both.

Question 22

What is arteriovenous malformation?

Answer 22

1. Manifests with seizures, intracerebral hemorrhage or subarachnoid hemorrhage.
2. Located in subarachnoid vessels extending into brain parenchyma or occur exclusively within hte brain.
3. Tangled network of wormlike vascular channels.

Question 23

How is a contusion brain injury caused?

Answer 23

Caused by rapid tissue displacement, disruption of vascular channels, and subsequent hemorrhage, tissue injury, and edema.

Question 24

What is a concussion?

Answer 24

Describes reversible altered brain function, with or without loss of consciousness, from head injury.

Question 25

What is diffuse axonal injury?

Answer 25

More subtle widespread injury to axons within the brain, sometimes with devastating consequences.

Question 26

What is epidural hematoma?

Answer 26

Between dura and skull. Usually from skull fracture in children and adults (infants may form in absence of fracture). Blood accumulates under arterial pressure. Patients may be lucid for several hours before neuro signs appear. Expands rapidly.

Question 27

What is a subdural hematoma?

Answer 27

Bleeding between two layers of the dura. Typically manifest within first 48 hours after injury. Slowly evolving neurological symptoms. Symptoms include headache and confusion.

Question 28

What are the 4 main routes of infectious spread in the nervous system.

Answer 28

1. Hematogenous spread: travel via arterial blood supply, or retrograde venous spread (facial veins and venous sinus) 2. Direct implantation: due to open/penetrating trauma or iatrogenic. 3. Local extension: infections of skull or spine including: air sinuses, infected teeth, osteomyelitis, congenital malformation. 4. Peripheral nerves: mainly viruses

Question 29

What is meningitis?

Answer 29

Inflammatory process involving the leptomininges (arachnoid and pia mater) within the subarachnoid space. If infection spreads into the underlying brain, it is meningoencephalitis.

Question 30

What are pathogens and signs/symptoms of pyogenic (bacterial) meningitis?

Answer 30

1. E. coli, group B strep (infants), neisseria meningitis (young adults), strep. pneumoniae or listeria monocytogenes (older adults) 2. S/S: systemic signs of infection, meningeal irritation, headache, photophobia, neck stiffness, "cloudy consciousness"

Question 31

What are pathogens and signs/symptoms of acute aseptic (viral) meningitis?

Answer 31

1. Enteroviruses, measles, influenza species, lymphocytic choriomeningitis virus 2. S/S: Less fulminant than pyogenic meningitis, lymphocytosis, moderate protein elevation, normal glucose levels. Bacteria can't be cultured.

Question 32

What are pathogens and signs/symptoms of chronic meningitis?

Answer 32

1. TB (mycobacterium tuberculosis), Spirochetal (borrelia burgdorferi, treponema pallidum), and Fungal (cryptococcus neoformans, histoplasma capsulatum, coccidioides immitis) 2. S/S: TB (headache, malaise, mental confusion, vomiting, tuberculoma), Paretic neurosyphilis (insidious progressive loss of mental and physical functions, mood alterations, severe dementia), Tabes dorsalis (impaired proprioception and ataxia, loss of pain sensation)

Question 33

Describe differences between central and peripheral nervous system myelin.

Answer 33

1. CNS: Oligodendrocyte processes myelinate >1 internode. | 2. Schwann cells myelinate 1 internode

Question 34

Define multiple sclerosis

Answer 34

An autoimmune demyelinating disorder characterized by episodes of disease activity, separated in time, that produce white matter lesions that are separated in space. Caused by environmental triggers, genetic predisposition, involves TH1 and TH17 T cells.

Question 35

What are symptoms of multiple sclerosis?

Answer 35

Gradual, often stepwise, accumulation of neurological deficits that occur from multiple relapses followed by episodes of remission, changes in cognitive function.

Question 36

Describe the neurological effects of thiamine deficiency.

Answer 36

Thiamine deficiency (beriberi). Particularly common with alcoholism. 1. Wernicke encephalopathy syndrome: abrupt onset of confusion, abnormalities in eye movement, and ataxia. 2. Korkasoff syndrome: irreversible profound memory disturbance.

Question 37

Describe alzheimer's disease.

Answer 37

1. Accumulation of AB plaques and tau tangles 2. Most common cause of dementia in older adults 3. Impaired higher intellectual function, memory impairment, altered mood and behavior.

Question 38

Describe frontotemporal lobar degeneration (FTLD), including Pick's disease.

Answer 38

FTLD encompasses several disorders that preferentially affect frontal and temporal lobes. Distinguished by lesions including tau or TDP43. Progressive deterioration of language and changes in personality. Pick disease associated with smooth, round inclusions called Pick bodies.

Question 39

Describe Parkinson's disease.

Answer 39

1. Hypokinetic movement disorder. 2. Loss of dopaminergic neurons in substantia nigra 3. Tremor, rigidity, bradykinesia, instability. 4. Progresses over 10-15 years, producing severe motor slowing to point of immobility.

Question 40

Describe Huntington's disease

Answer 40

1. Autosomal dominant movement disorder. 2. Associated with degeneration of striatum (caudate and putamen) 3. Characterized by involuntary jerky movements of all parts of body, writhing movements of extremities. 4. Progressive, death after disease course of 15 years.

Question 41

Describe Amytrophic lateral sclerosis (ALS)

Answer 41

1. Results from death of lower motor neurons in spinal cord and brain stem, and upper motor neurons (Betz cells) in motor cortex. 2. Lower moton neuron loss: denervation of muscles, muscular atrophy, weakness and fasciculations. 3. Upper motor neuron loss: Paresis, hyperreflexia, spasticity, upward babinski, degeneration of corticospinal tracts. 4. Sensation unaffected, may have cognitive impairment

Question 42

Describe unique characteristics of tumors in the nervous system

Answer 42

1. Do not have morphologically evident premalignant or in situ stages 2. Even low-grade lesions may infiltrate large regions of the brain, leading to serious clinical deficits, inability to be resected, poor prognosis. 3. Anatomic site can influence outcome independent of histological classification (e.g. benign meningioma may cause cardiorespiratory arrest from compression of medulla) 4. Even most highly malignant gliomas rarely spread outside CNS.

Question 43

List 5 most common primary sites of metastatic CNS lesions.

Answer 43

1. Lungs 2. Breast 3. Skin (melanoma) 4. Kidney 5. GI tract