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85 Cards in this Set
- Front
- Back
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Key criteria for causation in epidemiology (3)
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1.Dose-response
2.Consistency 3.Temporality |
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What is the problem with point prevalence?
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Point prevalence can miss cases due to a specific point in time
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X-ray and radiation exposure are classic examples of causation of epidemiology in which of the following:
A.prevalence B.dose response C.temporality D.risk factor |
Dose response
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As more cases are added to a study, it will have a ______effect on point prevalence
A.Direct B.indirect C.Minimal effect D. no effect |
Direct effect
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In a case-control study, calculating the odd's ratio is the same as risk.
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FALSE
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If the odds ratio is less than 1, it indicates:
A.No effect B.Harmful exposure C.Shielding exposure D.Potential exposure |
Harmful exposure
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Types of bias in case-control studies includes:
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Recall bias and admission rate bias (Berkson's bias)
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An example of a case control study that compares lung cancer patients that do and do not drink coffee.
A.cohort analysis B.admission analysis C.stratified analysis D.trendline studies |
Stratified analysis
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Which is NOT a specific type of cohort study?
A.continuous variable B.inception cohort study C.Random cohort study D.discreet variables |
Random cohort study
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In a cohort study, the odds ratio will tend to _____the risk ratio
A.Underestimate B.Overestimate C.are unrelated |
Overestimate
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For case control studies, you must calculate ____ and not _____.
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Odds Ratio (OR) and not risk
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Dose response
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Greater exposure to risk factor leads to greater effect on health
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Case control study
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Similar to retrospective cohort study, disease or condition is known- looking back in time for risk factors.
2 types: Prevalent case (includes all persons) Cumulative incidence (only new cases) |
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Risk
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estimate of proportion of unaffected persons who will develop the disease of interest over a specified period of time
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Odds ratio (OR) formula
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AD/BC
A=Exposed Cases B=Exposed Controls C=Non-exposed Cases D=Non-exposed Controls |
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Bradford Hill's Criteria of Causation
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Strength of Association
Consistency Specificity in the case Temporality Dose-response relationship (Increase dose---> increase occurance) Plausibility Coherence Experimental evidence Analogy |
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Case control study advantages
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1.Good for investigating rare diseases
2.Can be performed quickly and inexpensively 3.Useful for studying disease with long latency periods. 4.Facilitate study of multiple potiental case studies at once 5. existing records can often be used |
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Case control study disadvantages
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1.relies on patient recall of past exposure
2.Does not permit calculation of true disease rates in the population 3.Difficult to validate information on exposure 4.Other variables associated with disease are not controlled. |
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Recall bias
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systematic differences between cases and controls in ability to recall past exposures
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Berkson's bias (admission rate bias)
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type of selection bias where hospitalized cases are different than hospitalized controls
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Stratified analysis
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Considers confounding variables, (such as alcohol consumption and lung cancer) Looks at effect each independent variable has on outcome seperately
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Point prevalence
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proportion of population with disease at a certain period of time....looking at one study.
Can miss episodic conditions!!!!!!!! |
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Period prevalence
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looking at multiple studies within a time period...looks at more of the whole picture
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4 types of publishable case studies:
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1. Unique case
2. unexpected association 3.unusual presentation 4.unexpected development |
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OR equals 1
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no effect
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OR less than one
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protective exposure
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OR greater than one
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harmful exposure
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odds ratio is best used for case control studies where
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disease rate is low
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Confidence interval (CI)
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CI=z-score x SEm
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null hypotheses Ho
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no effect of treatment on outcome
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alternative hypotheses Ha
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there is an effect of treatment on outcome
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type 1 error
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failure to accept Ho, (or not reject Ho) when it is true - false positive.
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type 2 error
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failure to reject Ho when it is false. (false negative)
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As probability of making type 1 error decreases, probability of making type 2 error
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increases
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alpha (significance level)
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probablity of making type 1 error
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confidence level
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1-alpha
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beta-
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probability of making type 2 error
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relative risk
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probability of disease in exposed group/probability of disease in an unexposed group
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Number needed to treat (NNT) is the inverse of
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Absolute risk reduction
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In the big scheme of research, case studies are ranked
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low
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Case studies are especially prone to
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publication bias
observation bias selection bias |
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Which of the following measures central tendency?
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mean
median mode |
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nominal data can be mathematically ranked
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FALSE
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The best symmetrical measure for interval and ratio data is the mean
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TRUE
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A normal distribution is symmetric about its mean
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TRUE
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Does the normal curve of a normal distribution ever reach zero?
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No
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In normal distribution, the central measure of tendencies are the same
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True
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Is it possible to have muliple modes of tendency in a modal distribution?
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yes
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In research, the error bars on graphs are typically the standard error of the mean
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true
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What type of review can be performed on group or single subject studies?
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systematic review
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______reviews can include both quantitative and qualitative analysis
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systematic review
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Disadvantages of systematic reviews over primary studies
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systematic reviews are not a primary study
systematic reviews are subject to bias systematic reviews are limited by validity of individual studies |
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What is meta anaylsis
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A statistical analysis of results of several similar studies
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correct order from weakest to strongest in the hierarchy of evidence
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animal research, editorials and opinions, case reports, case series, case control studies, cohort studies, RCT, systematic reviews, meta-analysis
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What is an advantage of narrative reviews over systematic reviews?
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easy for novice authors to prepare
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File drawer problem is a
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publication bias
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Similarity between studies and what increases their ability to be compared is:
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study homogeneity
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What does study heterogeneity hinder?
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Comparison subjects
Study Design Statistical heterogeneity |
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Subgroup analysis may be more valid and may reduce statistical power in study heterogeneity
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True
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What part of IMRAD answers the question How was it studied?
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Methods
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IMRAD format of a scientific paper has a ____heading format
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8
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Estimate of proportion of unaffected persons who will develop the disease of interest over a specified period of time
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Risk
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Prevalence is
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incidence X duration
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Point prevalence is the proportion with disease within a defined period of time
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FALSE
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What is needed in establishing causation in epidemiology?
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temporality
consistency dose response |
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____studies evaluate the exposure level and disease status of a target population at one point in time
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Cross-sectional studies
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What is significant with case control studies?
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disease or condition is already known
Disease or condition is compared with 2 groups of subjects, one with disease, one without |
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If odds-ratio is greater than 1, there is ____exposure
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harmful
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are cohort studies more or less subject to bias than case control studies?
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less
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Which study is the best design to determine level of risk and is better for studying common diseases?
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cohort studies
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When an outcome in a research study is common (more than 10% of unexposed group), the odds ratio will____the risk ratio
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overestimate
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If AAR=10%, what is the NNT or number or patients needed to treat?
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10 patients
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Are case studies usually retrospective or prospective?
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retrospective
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Case studies have a low validity and a ____clinical relevance
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high
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Case studies have a similar format to IMRAD, but with case description rather than:
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Methods, Results
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Phalen's test for carpel tunnel syndrome
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1.increases pressure in the carpal tunnel
2.pinches the median nerve btwn transverse carpal ligament and radius 3.burning, tingling, numbness comfirms carpal tunnel. Significance: Median nerve entrapment. |
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Tinel's sign
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A test to detect irritated nerves. Dr. supports patient's hand and strikes carpal tunnel
Classic response: Tingling distal to tapping Significance: Median nerve lesion |
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Erb-Duchenne Palsy
Nerves affected? Cause? |
C5,6 (dorsal scapular n., suprascapular n., axillary n., musculocutaneous n., radial n.)
Results from excessive displacement of the head to the opposite side and depression of the shoulder on the same side. Lateral traction injury. 1.Damage to the upper trunks of brachial plexus. 2.Loss of function of C5,C6 innervated muscles 3. Weakness in levator scapulae, rhomboids, deltoid, biceps, infraspinatus, and wrist extensors. *Arm is held to side, internally rotated, wrist flexed* Waiter's tip or Bellman's tip |
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Klumpke's Palsy
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Ulnar Nerve
Results from excessive traction or abduction of arm....mother jerks child up by one arm. Thoracic outlet syndrome- Compression of BP as it passes between clavicle and first rib-causes cervical rib and other boney abnormalities Pancoast's syndrome- apical lung tumor that extends into the lower brachial plexus 1.damage to lower trunks of brachial plexus 2.weakness of C8 and T1 innervated muscles 3.Paresis of muscles that extend the hand and fingers 4.Atrophy of hypothenar muscles 5.Sensory loss on ulnar aspect of forearm and hand 6.Horner's syndrome associated. |
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Horner's syndrome
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A clinical syndrome caused by damage to the SNS.
Causes: usually acquired but can also be congenital or iatrogenic. Signs: 1. ptosis- drooping upper eyelid from loss of sympathetic innervation to retractor bulbi m. 2. Miosis (constricted pupil) and dilation lag 3.enophthalmos (eye is sunk in) 4.anhidrosis on affected side of face(absence of sweating) 5.Can Lead to a difference in eye color in children. Clinical picture: 1. Damage to C8 and T1 2.Inability to abduct the fingers, 3. atrophy of the small muscles of the hand, loss of sensation along medial aspect of arm. 4. "claw hand" |
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Peroneal nerve palsy
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Causes:
1.Damage to common peroneal nerve as is passes over the head of the fibula 2. forcible foot inversion 3. compression by tight stockings 4.casts 5. crossed legs Clinical signs: 1. foot drop 2.weakness in inversion and eversion 3. sensory loss over dorsolateral foot and shin |
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Meralgia Paresthesia
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"a condition of the thigh characterized by pain and dysfunctional, disturbing sensations"
Damage to lateral femoral cutaneous nerve Causes: Entrapment as it passes under ingunial ligament or under fascia latae. Obesity, pregnancy, heavy equipment belts Clinical signs: Parethesias or loss of sensation of the lateral thigh |
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Coccygeal Plexus
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S(4), 5, Cy1
Branches: Branch to coccygeus m. Branch to skin over the coccyx |
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Intercostal Nerves T2-T12
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Run between each rib in subcostal groove
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Dermatomes
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greater occipital nerve-C2
C3,4 Upper and lower extremities T4-nipple |
