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Anatomy of the Individual > Nerve Variation > Flashcards

Nerve Variation Flashcards

1
Q

Describe the general size and shape of the brain in regards to variation?

A

Large normal variation in size and shape
Differences between genders
Textbooks show idealised pattern:
- Main sulci and gyri easily seen

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2
Q

What was the methodology of the Gur et al., (1991) study into brain variation?

A

MRI study of:

  • 69 adults
  • Ages 18-80
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3
Q

What was the range of brain volumes in the Gur et al., (1991) study?

A

822.19ml - 1363.66ml

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4
Q

In what part of the brain was brain volume to be greater in the Gur et al., (1991) study?

A

Right hemisphere

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5
Q

How do brains differ between the sexes?

A

Males are, on average, 91ml larger than female brains

Female brains have less atrophy with age

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6
Q

How does age affect the brain according to the study by Gur et al., (1991)?

A 
Negative correlation with brain volume:
- r = -0.32
- p < 0.01
Positive correlation with CSF volume:
- r = 0.74
- p < 0.0001
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7
Q

Where did Gur et al., (1991) find the worst brain atrophy? What could this suggest?

A

In the left hemispheres of male brains:

- Gender differences in age-related changes in menal ability

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8
Q

What is brain mapping?

A

Map a patient’s scan to ‘normal’ pattern to see which areas are damaged or diseased
Uses Brodmann’s cortical areas and Talairach system (3D grid)

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9
Q

What did Uylings et al., (2005) do in regards to brain mapping?

A

Compared brain atlases with macro- and microscopic anatomy

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10
Q

What were the results of the Uylings et al., (2005) brain mapping study?

A

Large interindividual differences in the location of:

  • Primary visual cortex
  • Association areas
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11
Q

What conclusions were made regarding the results of the Uylings et al., (2005) study?

A

The differences could result in erroneous hypotheses on:

  • Brain system(s) involved in functioning
  • Specific brain disorders
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12
Q

Where does CN V develop from and when?

A

1st branchial arch in weeks 5-6

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13
Q

What is the textbook course of the inferior alveolar branch of CN V3? What is the clinical implication of this?

A

One mandibular canal on each side:

  • Contains inferior alveolar nerve (and vessels) to lower teeth
  • Dentists inject near opening for a nerve block
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14
Q

What is the embryology of the mandibular canals?

A 
3 canals on each side:
- 1st to incisors
- 2nd to primary molars
- 3rd to permanent molars
The 3 canals then remodel into 1
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15
Q

What is the incidence of bifid mandibular canals?

A

0.08-0.9%

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16
Q

Regarding mandibular canals, what did Auluck et al., (2005) find in case studies?

A

2 cases of bifid canals in children:
- 9 year old female with bilateral bifid canals
- 10 year old male with right bifid canal
Trifid canal in 20 year old females in left mandible

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17
Q

When does the auriculotemporal branch of CN V3 develop?

A

Week 7

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18
Q

What is the textbook anatomy of the auriculotemporal nerve?

A

From posterior root of CN V3

2 roots which surround the middle meningeal artery in the infratemporal fossa

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19
Q

What did Gulekon et al., (2005) find on dissection of 32 infratemporal fossae (16 cadavers) in regards to the auriculotemporal nerve?

A

50% had 1 root

  1. 5% had 2 roots
  2. 4% had 3 roots
  3. 1% had 4 roots:
    - Formed a ganglion-like knot
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20
Q

What study showed similar results to those of Gulekon et al., (2005)?

A

Baumel et al., (1971)

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21
Q

What path does CN VII have the longest of?

A

Intraosseous path of the cranial nerves

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22
Q

How did the patient in a case study by Ahmed et al., (2006) present?

A

Progressive conductive left-sided hearing loss

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23
Q

What variation was noted in the patient in a case study by Ahmed et al., (2006)?

A

Bifurcated horizontal part of CN VII:

- Straddling stapes footplate as it courses posteriorly

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24
Q

What are the embryological origins of CN VII dehiscence?

A

Failure of fusion of otic capsule and Reichert’s cartilage
Delayed fusion of stapes footplate and otic capsule:
- Allows forward progression of CN VII

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25
Q

What does dehiscence of CN VII leave it vulnerable to?

A

Tympanic membrane damage

Middle ear infection

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26
Q

What was the basis of the study by Lee et al., (2009)?

A

181 neck dissections:

- Investigated relations of CN XI and surrounding structures

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27
Q

What did Lee et al., (2009) find in regards to CN XI and its relations to the IJV?

A

CN XI crossed IJV:

  • Dorsally in 104 (57.4%)
  • Ventrally in 72 (39.8%)
  • Through it in 5 (2.8%)
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28
Q

What did Lee et al., (2009) find in regards to the supply to the SCM by CN XI?

A

Supplied in by branches:

  • Penetrating SCM in 98 (54.1%)
  • Not penetrating SCM in 83 (45.9%)
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29
Q

How many ganglia is the sympathetic chain usually composed of?

A

3 cervical
11 thoracic
5 lumbar
4 sacral

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30
Q

What is the intrathoracic nerve of Kuntz?

A

A nerve connecting the 2nd intercostal nerve to the ventral ramus of T1

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31
Q

What are the implications of the intrathoracic nerve of Kuntz?

A

Allows bypass of SNS chain:
- Failure of surgical sympathectomy
Contains fibres to brachial plexus
Doesn’t go through chain

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32
Q

What were the materials used in the Chung et al., (2002) study?

A

39 adult Korean cadavers:

- 66 sympathetic chains dissected

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33
Q

What were the results of the Chung et al., (2002) study into the intrathoracic nerve of Kuntz?

A

The intrathoracic nerve of Kuntz:

  • Present in 45 sides (68.2%)
  • Present bilaterally in 48.1% of cadavers
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34
Q

What are the types of intrathoracic nerve of Kuntz as described by Chung et al., (2002)?

A

Type A = Connection from T2 to T1
Type B = Connection from T2 to 1st intercostal nerve
Type C = Connection from T2 to rami communicans between the stellate ganglion and T1
Type D = INK was branched and connected T2 to both T1 and the 1st intercostal nerve

35
Q

What structure was noted by Chung et al., (2002) that could be mistaken for an intrathoracic nerve of Kuntz and what was its incidence?

A

A connection between T2 and the stellate ganglion:

- In 16 sides (24.2%)

36
Q

What is the stellate ganglion?

A

Lower cervical ganglion plus T1 ganglion

37
Q

What was the incidence of the stellate ganglion in the Chung et al., (2002) study?

A

84.8%

38
Q

What was the incidence of a large stellate ganglion that also included T2 in the Chung et al., (2002) study?

A

9%

39
Q

What is the main implication for the intrathoracic nerve of Kuntz?

A

Endoscopic thoracic sympathectomy for:

  • Hyperhidrosis of palms and axilla
  • Raynaud’s phenomenom
40
Q

What were the methods of the Ramsaroop et al., (2001) study?

A

Bilateral microdissections of the upper 5 intercostal spaces in:
- 32 foetuses (from 18 weeks to term)
- 18 adult cadavers
(Total of 99 sides)

41
Q

What were the results of the Ramsaroop et al., (2001) study?

A

SNS connections to T1 in 60 cases:
- 46 confined to 1st IC space ONLY
34 cases of intrathoracic nerve of Kuntz
Additional pathways and rami communicantes also noted

42
Q

What did Murata et al., (2003) study?

A

393 ganglia and 718 rami communicantes from 50 cadavers

43
Q

What were the findings of the Murata et al., (2003) study?

A

Range of 2-6 lumbar SNS ganglia per chain
Rami from ganglia to L1 ventral ramus longest
Rami from ganglia to L5 ventral ramus shortest
Ganglia and rami communicantes NOT distributed segmentally

44
Q

What is the textbook course of the phrenic nerve in the neck?

A

Runs over the anterior surface of the anterior scalene muscle in the neck

45
Q

What variations of the phrenic nerve can be seen?

A

Communicating branch to C5 and phrenic nerve over subclavian vein
Accessory phrenic nerve from:
- C5 and C6
- Nerve to subclavius (up to 75% of cases)

46
Q

What nerve roots does an interscalene block anaesthetise?

A

C5-C8/T1

47
Q

When is an interscalene block not usually used and why?

A

For hand procedures:

- C8/T1 not often well blocked

48
Q

What nerve roots does a supraclavicular block anaesthetise?

A

C5-T1

49
Q

What procedures is a supraclavicular block used for?

A

Mid-humeral to hand procedures

50
Q

During what nerve block is the phrenic nerve often accidentally anaesthetised?

A

Interscalene block:

- 36-67%

51
Q

What did the patient in the Gupta et al., (2009) case study undergo a supraclavicular brachial plexus block?

A

Right ulnar implant removal

52
Q

What happened to the patient in the Gupta et al., (2009) case study? What did scans show?

A

Patient complained of dyspnoea:
- Right hemidiaphragm paralysed
- Breathing was intercostal on ipsilateral side
CXR showed:
- Right hemidiaphragm at 5th IC space (during op.)
- Right hemidiaphragm at 7th IC space (post-op)

53
Q

Why did the patient in the Biegleisen, (2003) case study undergo supraclavicular block?

A

Right ulnar osteotomy and ulnar nerve transposition

54
Q

What happened to the patient in the Biegleisen, (2003) study?

A

Also showed stimulation of phrenic nerve:

- Diaphragmatic twitches

55
Q

What is the textbook anatomy of the sciatic nerve?

A

Nerve roots = L4-S3
Passes through greater sciatic notch
Passes underneath piriformis into gluteal region
Divides into tibial and common fibular nerves near popliteal fossa

56
Q

What did Pokorny et al., (2006) study?

A

The relationship between piriformis and sciatic nerve

57
Q

What were the results of the Pokorny et al., (2006) study?

A

91 cadavers:

- Anomalies in 19 (20.9%)

58
Q

What are the 6 types of relationship between piriformis and the sciatic nerve?

A

Type I = Unsplit and below piriformis
Type II = Split; 1 above and 1 through piriformis
Type III = Unsplit and above/dorsal to piriformis
Type IV = Split; 1 below and 1 through piriformis
Type V = Unsplit and through piriformis
Type VI = Split; 1 above and 1 below piriformis

59
Q

What were the incidence rates of the 6 types of relationship between piriformis and sciatic nerve as found by Pokorny et al., (2006)?

A 
Type I = 79.1%
Type II = 0%
Type III = 0%
Type IV = 14.3%
Type V = 2.2%
Type VI = 4.4%
60
Q

What is the name for the classification of the relationship between piriformis and the sciatic nerve?

A

Beaton’s classification

61
Q

In what study were Type II and Type III relationship between piriformis and the sciatic nerve seen? What does this suggest?

A

A study of a Chinese population by Lee and Tsai, (1974):

- Racial differences?

62
Q

What is the potential implication of sciatic nerve variations?

A

Neurological deficit following total hip arthroplasty

63
Q

What technique is carried out during a total hip arthroplasty to allow the hip to be dislocated?

A

Partial/Complete tenotomy of pelvitrochanteric muscles:

  • Mainly in posterior (but also anterior) approaches
  • May be reattached
64
Q

What happens during recovery following total hip arthroplasty that may affect the sciatic nerve?

A

Piriformis heals, scars and will contract:

  • Not an issue in Type I (‘normal’) sciatic nerve
  • May overstretch/compress the nerve in variants (especially those where the nerve goes through piriformis = Types II, IV and V)
65
Q

What are the textbook roots of the brachial plexus?

A

C5-T1

66
Q

What are potential variations of the brachial plexus?

A

Pre-fixed = C4-C8
Post-fixed = C6-T2
Trunk, cord and terminal branch variations

67
Q

How do variations of the brachial plexus affect clinical practice?

A

Affect clinical evaluation of motor and sensory supply to the upper limb

68
Q

What were the variations seen in a 56 year old male cadaver by Bhanu et al., (2010)?

A 
Median nerve:
- Directly from lateral cord
- No contribution from medial cord
Lateral pectoral nerve from anterior divisions of upper and middle trunks (instead of from lateral cord)
Communicating branch between:
- Ulnar nerve AND
- Anterior division of middle trunk
69
Q

What were the variations seen in a 60 year old male cadaver by Saeed and Rufai, (2003)?

A

Median nerve formed from 3 roots:
- 2 from lateral cord
- 1 from medial cord
Variant lateral root crossed anteriorly to axillary artery

70
Q

What variations in a 60 year old female cadaver were noted by Bertha et al., (2009)?

A

Right sided axillary arch above vessels
Left sided axillary arch:
- Below vessels
- Enclosed by 2 roots of radial nerve

71
Q

What did Kervancioglu et al., (2011) study?

A

Branching patterns of the musculocutaneous nerve in foetuses

72
Q

What variations were noted by Kervancioglu et al., (2011)?

A

Musculocutaneous nerve course and branching:
- Pierce coracobrachialis or not
- 1 or 2 branches to biceps brachii
Communication between MCN and median nerve

73
Q

How does cutaneous nerve variation affect clinical practice?

A

Affects evaluation of nerve damage in the periphery

74
Q

What is the textbook cutaneous supply of the sural nerve?

A

Posterior calf

Dorsolateral foot

75
Q

What is the textbook origin of the sural nerve?

A

Tibial nerve
OR
Tibial and common fibular nerves

76
Q

Regarding the origin of the sural nerve, what did Mahakkanukrauh and Chomsung, (2002) note?

A

67.1% from the union of medial sural cutaneous nerve (tibial) and lateral sural cutaneous nerve (fibular)
OR
32.2% are a continuation of the tibial nerve
OR
0.7% medial sural cutaneous nerve (tibial) plus another branch of fibular

77
Q

Regarding union sites forming the sural nerve, what did Mahakkanukrauh and Chomsung, (2002) find?

A

Popliteal fossa (5.9%)
Middle 1/3 leg (1.9%)
Lower 1/3 leg (66.7%)
Just below ankle (25.5%)

78
Q

In what percentage of cadavers was bilateral asymmetry of the sural nerve noted in the Mahakkanukrauh and Chomsung, (2002) study?

A

80%

79
Q

Where was there a consistent location of the sural nerve noted in the Mahakkanukrauh and Chomsung, (2002) study?

A

1-1.5cm posterior to posterior border of lateral malleolus

80
Q

What implications did Mahakkanukrauh and Chomsung, (2002) suggest could result because of sural nerve variation?

A

Nerve conduction studies

Nerve grafting

81
Q

What were the cadavers used in the Madhavi et al., (2005) study into sural nerve distribution on the dorsum of the foot?

A 
Adults:
- Males = 60 pairs
- Females = 18 pairs
Foetal:
- Males = 20 pairs
- Females = 32 pairs
82
Q

What were the results of the Madhavi et al., (2005) study into the sural nerve?

A

6 patterns of innervation found
‘Normal’ Type I in 35.8% o feet
Wider area of skin than textbook
No relation to gender or side

83
Q

What are the implications of findings of the Madhavi et al., (2005) study?

A

Patterns of sensory loss
Diagnosis
S1 dermatome

Anatomy of the Individual (10 decks)

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