Neuroscience Flashcards Preview

Neuro > Neuroscience > Flashcards

Flashcards in Neuroscience Deck (96):
1

Intramedullary lesions

produce burning or tingling pain in extremities

May spare sensation in perineal and sacral areas (located on periphery of cord)

2

Intradural lesions

Commonly benign masses (schwannomas of spinal

Usually painless, present w/ gradual symptoms

3

Extradural lesions

Tend to be more malignant processes (infections or cancer)

Associated w/ severe pain- bone destruction

Symptoms can progress rapidly

4

Cauda Equina Compression
Signs and Symptoms

□ Numbness in genitals, buttocks, and anus due to compression of sacral nerve roots (Saddle anesthesia)
□ Lower extremity weakness, often asymmetrical
□ Decreased knee reflexes
□ Bowel and bladder retention (often a later finding)
□ Pain if a disc herniation is the case

5

Cause of Cauda Equina Compression

herniated disk at L4,L5 or L5-S1

6

Conus medullaris Compression
Signs and Symptoms

□ Knee reflexes preserved, ankle reflexes gone

□ Bowel/bladder incontinence develop early, as does impotence

7

Lhermitte's Sign

electrical sensation

® Runs down back into limbs
® Caused by neck flexion
® Most commonly occurs in MS

8

Posterior cord syndrome

□ Loss of proprioception due to involvement of dorsal columns:
® Underrated syndrome
® Abnormal sensations, parethesias- burning, tingling, buzzing
® Can make patients miserable
® Central pain- originates in CNS

9

Anterior cord syndrome

□ Motor deficits- below lesion (corticospinal)
□ Loss of pain and temperature sensation (spinothalamic)
® Proprioception intact- sparing of dorsal columns
□ Bowel and bladder dysfunction, impairment of sexual function
□ Occlusion of anterior spinal artery (most common)
® Supplies anterior 2/3 of cord

10

Central cord syndrome

□ Loss of pain and temperature in arms, hands, and around shoulders and torso (shawl distribution)
® - disruption of spinothalamic tract as it crosses
® Lower extremities can be affected, not to same extent
□ Weakness of arms and hands- involvement of anterior horn cells w/in gray metter

11

Hemicord syndrome

□ Weakness on same side of lesion- injury of corticospinal tract (ipslateral)
□ Loss of proprioception on same side- injury to dorsal columns (ipslateral)
□ Loss of pain and temperature sensation on opposite side of lesion- injury to spinothalamic tract (contralateral)
□ Stabbed in the back

12

Transverse lesions

□ Complete motor or weakness loss below the lesions
® Paraparesis- weakness of the legs
® Quadraparesis- weakness of the arms and legs
® Paraplegia- paralysis of the legs
® Quadraplegia- paralysis of the arms and legs
□ Loss of sensation- damage to spinothalamic tract and dorsal columns
□ Bowel and bladder dysfunction, impairment of sexual function
□ i.e. transverse myelitis

13

Spinothalamic tract

pain and temperature from the opposite side of the body

ascending

14

Upper motor neuron signs

® Weakness, increased tone/spasticity, increased reflexes
® Pathological reflexes (Babinski, Hoffman's signs)
® Lack of atrophy

15

Clonus

Continuous involuntary muscle contraction, relaxation

16

Lower motor neuron signs

® Damage to anterior horn cells or peripheral nerves
® Decreased tone, decreased reflexes, atrophy, fasciculations
® Flaccid, atrophy…

17

Corticospinal tract

motor to same side of the body

descending

18

Dorsal columns/Medial Lemniscus tract

proprioception and vibration from same side of body

ascending

19

Adrenoleukodystrophy

Disorder of peroxisomal function

By gross pathology: disorder of adrenal and white matter

By EM: disorder of peroxisomal storage
Biochem: disorder of deficient activity of VLCFA

Eufibers, deep white matter completely gone

Enlarged cortical adrenal cells w/ prominent striations

20

Krabbe's disease

□ Autosomal recessive
□ Deficiecny of enzyme galactosyl ceramidase
□ Chromosome 14q31
□ Globoid cells w/ galactocerebroside shunting of galactocerebroside to phychosine
□ Very destructive, kills brain cells
□ Deteriorating around 4/5 months
□ Dense gliosis of the brain
□ Globoid cells- macrophages accumulating substance that isn't being properly digested

21

Differential Diagnoses for Leukodystrophy

□ Infantile Krabbe Disease- begins w/in first year of life
□ Metachromatic LD: 2nd year of life
□ Spongy degeneration: megalencephaly
□ Pelizaeus- Merzbacher: abnormal eye movements, microcephaly
□ Neonatal adrenoleukodystrophy- affects brain, liver, retina

22

Leukodystrophy

§ Hereditary
§ Normal early development
§ Affect brain myelin and causes regression
§ Commonly fatal
§ Progressive
□ Cognitive deterioration
□ Neuropsychiatric difficulties
□ Pyramidal and cerebellar abnormalities
□ Visual abnormalities
□ Deafness
§ Dementia and death within a few years

23

Gaucher disease

Lysosomal storage disorder
§ Autosomal recessive
§ Most prevalent lysosomal storage disease
§ Deficiency of enzyme, accumulation of glucocerebroside
§ Rare cases- deficiency of…
§ Non-neruonopathic form
□ Adult onset (Type 1)- hepatosplenomegaly, pancytopenia, skin
□ Bond- deformities of distal femur (Erlenmeyer)
§ Neuronopathic forms
□ Infantile (Type II)- rapidly progressive
□ Juvenile (Type III)- slowly progressive

24

Disorders of gray matter

§ Alpers-Huttenlocher syndrome
§ Pantothenate-kinase associated neurodegeneration
§ Menke's disease
§ Leigh's disease

25

Disorders of white matter

leukodystrophes

26

Metabolic diseases

associated with genetic defects involving specific cellular organelles: lysosomes, peroxisomes, mitochondria

unable to handle metabolism of neurons to execute their function, defect in myelination

27

Germinal matrix hemorrhage

○ Precise factors are unknown
○ Prematurity is commonest association
○ Not necessarily associated w/ stressed-out fetus
○ Hemorrhage may be localized or spread into ventricles and beyond
§ Can expand ventricle or explode into germinal matrix back into the brain (Grade IV)
○ Lower incidence when mom's were given K+ early on in fetal distress
Stabilizes germinal matrix

28

Dandy-walker malformation

§ Triad of 4th ventricle cystic dilatation, vermal agenesis, and enlargement of posterior fossa
□ Vermis between R and L cerebellar hemispheres
□ Cyst expands, full of fluid
§ Patency of foramina of Lushka and Magendie variable
□ Closed- fluid obstruction, hydrocephalus
§ Aplasia of the entire cerebellar vermis in 1/4 of patients
□ Can almost always find small remnants microscopically

29

Arnold-chiari malformation (Chiari Type II)

§ Small posterior fossa with downward displacement of cerebellar tissue (vermis) through foramen magnum
□ Malformation of skull?
§ Caudal displacement of medulla
§ Associated with hydrocephalus and lumbar meningomyelocele
§ Pathogenesis uncertain
§ Hydrocephalus

30

Hydranencephaly

§ Cerebral hemispheres largely absent
§ Fluid filled cavity instead
§ Fetal hypoxia, maternal intoxication, twinning
§ Skull present, often externally normal
Secondary destruction - brain tissue killed by hypoxic ischemic insults

31

Agenesis of corpus callosum

§ Brain won't learn how L and R talk to each other
§ Absence of white matter bundle connecting both hemispheres
§ Sporadic or inherited
§ Associated conditions: holoprosencephaly, midline tumors (lipoma, meningioma, etc.)

32

Microcephaly (micrencephaly)

§ Small brain
§ Numerous genetic syndromes, alcohol, drugs, viruses
§ In late stage of development
§ Very non-specific
§ Look at the family** small/large head?

33

Double cortex

§ Neurons made it half-way
§ Mutations in double cortin
§ Not connected appropriately, can be a cause of seizures

34

Nodular ventricular heterotopia

§ Nodular and laminar heterotopia
§ Neurons mature in wrong spot
§ Normal looking neurons, but not connected to anything else

35

Polymicrogyria

§ Small, irregularly formed, numerous individually thin gyri
§ Cobblestone appearance
§ Loss of external contours of the convolutions of the brain
§ Many genetic syndromes associated
§ Twinning, VZV, CMV, Toxo, syphillis….

36

Pachygyria (macrogyria)

§ Reduced number of broadened convolutions (gyri)
§ Reduction in number of neurons reaching neocortex
§ Results in simplification of gyral foldings

37

Agyria (lissencephaly)

§ Small brain with smooth cerebral surface
§ Absence of gyri and sulci
§ Neuroblasts migrated into subarachnoid space
Defect in border preventing neurons from getting out

38

Arrhinencephaly

olfactory aplasia

Agenesis of olfactory bulbs and tracts and related structures

Mildest form of craniofacial anomalies

Incidental, or with holoprosencephaly

39

Holoprocencephaly

Failure in outgrowth/cleavage of pros encephalic vesicle

Incomplete separation of cerebral hemispheres

Single ventricle and fused basal ganglia (holosphere)

Associated w/ Trisomy 13, maternal diabetes, rubella, toxo, fetal-alcohol syndrome
□ Severe facial malformation (cyclopia)
□ Severe mental retardation and reduced lifespan

40

Myelomeningocele

Failure of posterior end of NT closure
Both meninges and deformed spinal cord herniate through defect in vertebrae
Covered by skin membrane or skin
Mostly in lumbosacral region (motor and sensory deficits in LE)
Defect limited to spine (spina bifida occulta)

41

Encephalocele

Hernia of brain tissue through midline defect in cranial cavity (mesodermal defect)
Mostly located in occipital or posterior fossa regions, can be frontal
Mostly female
There may be associated abnormalities- hydrocephalus

42

Anencephaly

Failure of anterior end of neural tube closure
Complete loss of brain- leakage of fluid into brain
1-5/1000 live births, mostly females
28 days of gestation
□ Detected early in gestation by US
Absence of brain and calvarium
Small disc shaped brain (area cerebrovasculosa)
Rarely survives more than a few hours
Raised alpha-fetoprotein level
Protuberant eyes, short neck, low set ears
Incidence high in Ireland, Wales, France (10X)

43

completion of neurulation

4 weeks

44

completion of segmentation and cleavage

8 weeks

45

proliferation and migration

8 weeks --> birth

46

etiology of CNS abnormalities

genetic, sporadic, familial
infectious: VZV, CMV, toxo
metabolic: maternal diabetes, folate deficiency
toxic: alcohol

47

etiology of CNS structural malformations

Genetic factors (most cases have no link)
Intrauterine infections, particularly viral
Systemic factors: hypoxia, hypoglycemia, alcoholism, drugs, CO-poisoning
Physical factors: ionizing radiation
Idiopathic: often the specific cause is unknown

48

lower motor neuron lesion

Loss of volitional control
Weakness
Hyporeflexia
Flaccidity
Fasciculations
Atrophy

49

upper motor neuron lesion

® Initial flaccidity and loss of reflexes due Hyperreflexia
Spasticity
Weaknss
Loss of volitional control (particularly the digits)
No atrophy (except for disuse)

50

reflex (definition)

a reflex is relatively predictable, involuntary, and stereotyped response to a particular stimulus

51

components of reflex

□ Afferent limb (Ia, Ib, II, FRAs)
□ Central component (ITNs)
□ Efferent limb (motor neurons)

52

membrane potential

voltage (electrical potential) between the inside of a neuron and the surrounding liquid

53

neuron resting potential

resting potential of between -90 and -40mV

54

depolarization

increase in membrane potential

55

hyperpolarization

decrease in membrane potential

56

ions inside of cell at rest

K+, Cl-

57

ions outside of the cell at rest

Na+, Ca++, Cl-

58

Action potential

rapid electrical event that allows a neuron to signal over a long distance (e.g. from the brain to a distant muscle).

59

Hodgkin-Huxley Model

mathematical framework for understanding the action potential and the electrical behavior of neurons in general. This model describes the cell as an electrical circuit, in which different currents are carried by different ions

60

3 variables for Hodgkin-Huxley model

peak conductance
gating variables
driving force

61

synaptic potentials

are mediated by ligand-gated ion channels, ion channels that are activated by neurotransmitters rather than by voltage. Synaptic potentials are graded, rather than all-or- none like action potentials.

62

what do Neurons use to store energy and facilitate rapid signaling

active transport

63

what allows for the generation of rapid signals

ion channels

64

how can ion channels be activated

voltage, chemical ligands, sensory stimuli

65

use of electrical circuit model

can be used to understand how ion channels interact to produce cellular behavior.

66

Tetrodotoxin poisoning

Na+ channel blocker
can't generate AP's
doesn't cross BBB?- stay conscious

67

Charybdotoxin

K+ channel blocker
prevent depolarization, hyperactive-state, convulsions

Scorpion bite

68

Saxitoxin

paralytic shellfish poisoning

Na+ channel blocker
can't generate AP

69

cause of MG

Auto-antibodies directed against neuromuscular junction proteins
85%: Ab against postsynaptic Ach receptors
10%: Ab against MuSK (less ocular symptoms)
Rare and of unknown pathogenicity: Abs against LRP4 and agrin
POSTsynaptic abnormality

70

Symptoms of MG

Diplopia (double vision) or ptosis (eyelid drooping) – initial symptom in 2/3 of patients
Bulbar dysfunction – difficulty chewing, swallowing, talking
Limb weakness – hip flexors, neck extensors, ankle dorsiflexors

71

Course of MG

Symptoms fluctuate, fatigue-able, worse later in day and with prolonged use
Weakness limited to ocular muscles -10%
Most cases progress with weakness within 2 years of onset
Spontaneous improvement with symptom free intervals can occur early in disease

72

Aggravating factors in MG

Systemic illness
Thyroid dysfunction
Pregnancy / menstrual cycle
Increased body temperature
Emotional distress
Drugs: aminoglycosides, fluoroquinolones, macrolides, magnesium, quinidine, procainimide

73

tensilon test

diagnosis of MG

Acetylcholinesterase inhibitor
Most reliable if ptosis present, + in 90% of MG patients
Incremental injections of tensilon, monitor every 60 seconds for improvement in lid ptosis
Can cause bradyarrhythmias and syncope

74

nerve conduction study purpose

Helps distinguish myelin from axon problem on the nerve

75

EMG purpose

Helps distinguish neuropathic from myopathic disorders

76

treatment of MG

Initial therapy- acetylcholinesterase inhibitors (AchE inhibitors)
Pyridostigmine (most common) or neostigmine
If ocular symptoms become debilitating or weakness of oropharyngeal/limb muscles:
Prednisone (can use azathioprine if want to spare steroids)
IVIG or plasma exchange + azathioprine
Thymectomy- in all patients with thymoma, optional in patients without one

77

LEMS- cause

Autoimmune attack against the voltage gated calcium channels on motor nerve terminal
PREsynaptic abnormality of Ach release
Half have underlying malignancy
Usually small cell lung cancer

78

Symptoms of LEMS

Difficulty walking- most common initial symptom
Bulbar and ocular muscles typically spared or mildly affected
Dry mouth
Postural hypotension, erectile dysfunction

79

course of LEMS

Strength improves after exercise in most patients
Weakness is rarely life threatening
May be aggravated by agents that also worsen MG

80

PE in LEMS

Symptoms typically out of proportion to degree of weakness found on exam
Tendon reflexes absent or reduced
Can be increased by brief activation of appropriate muscles or by tapping the tendon repeatedly

81

treatment of LEMS

Treat any malignancy present- weakness may improve without any further treatment
AchE inhibitors may help dry mouth but rarely weakness in LEMS
Amifampridine (3,4-Diaminopyridine)
Increases Ach from autonomic and motor nerve terminal
Prednisone, azathioprine– modest benefit
IVIG, plasma exchange – for rapid, temporary improvement (like in MG)

82

tick paralysis

Blocks Na ion influx, inhibits presynaptic depolarization

83

snake venom

Can affect pre- or postsynaptic junction

84

organophosphates and carbamates

Inhibit acetylcholinesterase abundance of Ach
Sx: miosis, bradycardia, salivation, bronchospasm, diarrhea, urination, vomiting
Tx: atropine, pralidoxime

85

hypermagnesemia

IV administration in women with eclampsia
blocks Ca channels weakness, absent DTRs

86

hypocalcemia

Increases permeability to Na ions  progressive depolarization  sustained contractions = tetany

87

anesthetic agents

Succinylcholine – binds AchR, does not allow muscle to repolarize
Curare – blocks Ach R

88

What major ions and neurotransmitters play a role in neural transmission at the NMJ?

Ca, Na, K, Ach

89

Which enzyme is responsible for stopping neural transmission?

Acetylcholinesterase

90

Which part of the synaptic membrane does myasthenia gravis affect?

Postsynaptic

91

Which part of the synaptic membrane does LEMS affect?

Presynaptic

92

Most common presenting symptom in MG?

Diplopia

93

Most common presenting symptom in LEMs?

Falls, difficulty walking

94

How can you diagnose MG and LEMS?

Serum antibodies, RNS

95

When should a thymectomy be done?

Definitely if there is a thymoma, optional otherwise

96

What are key features of botulism

Cranial nerve palsies, descending weakness