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Minor Oral Surgery > Nerve Damage and 3rd Molar removal > Flashcards

Nerve Damage and 3rd Molar removal Flashcards

1
Q

Give instances where surgical intervention of damage to the inferior alveolar nerve can be undertaken

A
  • nerve is completely divided and severed ends are misaligned
  • if a bony fragment has compressed mandibular canal
  • patient suffers from persistent neuropathic pain
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2
Q

Following damage to the lingual nerve, if sensory testing demonstrates no neural recovery within ________, exploration of injury site and microsurgical repair of damaged nerve can be undertaken

A

3-4 months

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3
Q

What nerves are in close proximity with impacted 3rd molar teeth?

A
  • lingual
  • inferior alveolar
  • mylohyoid
  • buccal
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4
Q

What is parasthesia?

A

abnormal sensation

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5
Q

What is hypoaesthesia?

A

reduced sensation

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6
Q

What is dysaesthesia?

A

unpleasant abnormal sensation

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7
Q

What factors can aid the correct management of nerve injuries?

A
  • correct diagnosis of the type of injury
  • monitoring recovery
  • treatment of appropriate cases
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8
Q

Following IAN damage, what can cause retraction of severed nerve endings? What is the consequence of this?|

A

Displacement into the socket

This means that the severed nerve endings are no longer side by side; this can impact regeneration of the nerve

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9
Q

Regeneration of the IAN within the canal can be impeded by …

A

displaced fragments of bone from the roof of the canal

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10
Q

Most patients following IAN damage will regain normal sensation within weeks or months. True or false

A

True

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11
Q

What is hyperalgesia?

A

increased response to stimulus that is normally painful

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12
Q

What is allodynia?

A

pain due to stimulus that does not usually provoke pain

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13
Q

What are the 5 radiographic signs/ features that suggest juxtaposition of mandibular canal with the third molar roots? (Rood and Shehab, 1990)

A
  1. radiolucency across the roots of the third molar
  2. deviation of mandibular canal
  3. interruption of the white line of the canal. Signs considered to be clinically important
  4. deflection of the third molar roots by the cancal
  5. narrowing of the third molar root
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14
Q

A higher incidence of IAN injury has been reported with third molars that are …

A
  • horizontally impacted
  • mesioangularly impacted

AND
* have complete bone cover

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15
Q

One study has suggested that increasing age is associated with higher incidence of IAN injury. True or false

A

True

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16
Q

What covers the lingual nerve?

A

thin layer of soft tissue and mucosa

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17
Q

Outline some reasons why regeneration of axons across the gap is less successful in lingual nerve injury?

A
  • they may become trapped or constricted by scar tissue
  • adjacent soft tissue may also be distorted and thus the nerve endings are misaligned
  • the presence of functionally distinct nerve fibres (e.g. mechanosensitive, thermosensitive, gustatory, vasomotor and secretomotor) may make successful regeneration of axons back to the correct receptor/effector and location less likely
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18
Q

Outline some postulated reasons as to why the incidence of lingual nerve injury varies

A
  • differences in the time interval between tooth removal and the assessment of sensory impairment
  • whether or not the sensory deficit was established objectively by the clinician or based on a subjective patient assessment
  • differing surgical techniques
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19
Q

What would an early assessment of sensory impairment yield?

A
  • reports of transient changes that recover rapidly and completely
  • these changes would often be missed if assessment takes place following a longer recover period
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20
Q

What surgical technique is at increased risk of causing lingual nerve injury?

A

raising and retraction of a lingual mucoperiosteal flap

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21
Q

Outline one risk factor that increases risk of lingual nerve injury

A
  • if distal bone is removed during surgery
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22
Q

What are the strongest predictors of temporary and permanent lingual nerve injury?

A
  • difficulty of the extraction
  • factors reflecting the surgical skill (e.g. lingual plate perforation)
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23
Q

Briefly describe the path of the buccal nerve

A
  • descends between two parts of the lateral pterygoid muscle
  • it is medial to the ramus of the mandible
  • passes laterally across the exteral oblique ridge, distal to the third molar
  • supplies the cheek
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24
Q

What is included in the sensory distribution of the buccal nerve?

A
  • lower posterior buccal sulcus
  • gingivae
  • area of cheek mucosa
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25
Q

What are the 5 degrees of nerve injury according to Sunderland’s classification?

A
  • conduction block
  • transection of axon with intact endoneurium
  • transectioon of nerve fibre (axon and endoneurial sheath) inside intact perineurium
  • transection of nerve fibres and perineurium, nerve trunk maintained bu epineurial tissue
  • transection of the entire nerve trunk
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26
Q

Why is part or all of the buccal nerve at risk when a distal relieving incision is made during 3rd molar surgery?

A

this is because as the nerve crosses the external oblique ridge, it is composed of between 1 and 5 branches, the lowest of which may be >1cm below the deepest concavity of the ridge

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27
Q

What type of injury can give rise to a temorary conduction block?

A

minor compression injury (of the nerve)/ first degree injury

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28
Q

According to Seddon, a temporary conduction block is referred to as …

A

neuropraxia

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29
Q

What is the consequence of second degree injury?

A

in this type of injury the axon distal to the site of the injury degenerates (wallerian degeneration)

recovery is dependent on regeneration of damaged axons

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30
Q

What is a second degree nerve injury?

A

more sever compression or crush injury

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31
Q

According to Seddon, second degree nerve injury is referred to as …

A

axonotemesis

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32
Q

What is a third degree nerve injury?

A

rupture of the endoneurium

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33
Q

What is a fourth degree nerve injury?

A

rupture of the perineurium

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34
Q

What can cause third and fourth degree nerve injury?

A

raising a lingual mucoperiosteal flap - a stretch injury

35
Q

Give an instance that leads to a fifth degree nerve injury

A

if the IAN penetrates the root of a third molar and is severed during tooth removal

36
Q

Fifth degree nerve injuries are also referred to as …

A
  • complete resection of nerve trunk
  • neurotmesis (Seddon)
37
Q

What are the potential effects of a rotating bur on the lingual nerve?

A
  • partial division of the nerve
  • stretch the nerve
38
Q

What is the consequence of first degree nerve injury (conduction block) on the nerve ?

A
  • local thinning of the axons
  • segmental demyelination

these changes are reversible

39
Q

What causes slower recovery following first degree nerve injury?

A

segemental demyelination may cause recovery to be slightly slower

40
Q

Where does wallerian degeneration occur?

A

distal to the site of the nerve injury

it usually extends centrally for a few millimetres

41
Q

Outline the cellular events that follow axonal discontinuity of a myelinated fibre

A
  1. transection of the nerve fibre peripherally results in distal fragmentation of the axon and myelin; in the proximal segment, degeneration occurs to at least the first node of ranvier
  2. schwann cells in the distal stump form bands of Bungner through which axons sprouts can regenerate
  3. regenerated axons regain contact with periphery and matures but a reduction in diameter persists
  4. sprouts may locate and innervate inappropriate targets or if no target organ is located then axonal sprouts persist as a neuroma
42
Q

What is the consequence of a nerve injury if the cut ends of the nerve are widely seperated?

A

less likely that a good recovery will occur and abnormalities will persist

43
Q

What kind of changes can occur centrally following neuronal injury?

A

chromolytic changes

44
Q

Why will crush injuries have a more rapid recovery time compared to section injuries?

A

endoneurial sheaths remain intact and therefore the regenerating axons are guided to the correct receptor type at the correct location

45
Q

Recovery from crush injuries may take ______ and _________ be complete

A

months

may

46
Q

Recovery from section injuries will progress for at least ______ and will ______ be complete

A

a year

will never be complete

47
Q

Partial sensory loss is indicative of what type of nerve injury?

A

first degree injury

48
Q

It is impossible to determine whether or not complete anaesthesia is caused by a compression or section nerve injury. True or false

A

True

49
Q

How can you monitor sensory recovery?

A

application of stimuli to the denervated area

50
Q

Minor sensory disturbances may not be detected by testing. True or false

A

True

51
Q

Briefly describe the conditions required for simple sensory testing

A
  • pt should be seated in a quiet room
  • pts eyes should be closed
  • detection of stimulus should be indicated to examiner by pt raising a finger
  • results of each test should be then compared with normal (uninjured) side
52
Q

When should the first sensory tests ideally be undertaken?

A

within 2 weeks of the injury to establish a baseline

53
Q

How is light touch sensation most commonly tested?

A

gentle application of a wisp of cotton wool to the skin or mucosa

54
Q

What are the disavantages associated with using a wisp of cotton wool for the light touch sensation technique?

A
  • difficult to apply stimulus in a reproducible manner
  • application on moist oral mucosa is difficult
55
Q

What instrument/technique offers greater consistency and reproducibility for light touch sensation ?

A

Von Grey Hairs
- standard force of 20mN (20g)

56
Q
A
56
Q

What is the downside of using a dental probe or needle to assess pin prick sesnsation?

A

not reproducible

57
Q

What has allowed reproducible results to be obtained when assessing pin prick sensation?

A

A pin attached to a spring

allows a known pressure of up to 150mN (15g) to be applied

58
Q

Briefly describe how pin prick sensation can be assessed

A
  • first 15g of pressure is randomly applied to test area to map out any areas of anaesthesia
  • [if sensation is detected on affected injured side then pin prick sensation threshold is determined]
  • the pin is applied at steadily increasing pressures and the patient is asked to indicate the point at which the sensation becomes sharp as opposed to dull
59
Q

What is the two-point discrimination test? Briefly describe an instrument that can be used to carry out a rapid 2-point discrimination test

A

sensory test designed to test the ability to distinguish whether one or two pressure points have been applied to an area

pairs of blunt probes with different seperations (from 2-20mm mounted around a disc

60
Q

Describe how a two point discrimination test is performed

A
  • [used on lips or tongue]
  • probes drawn a few millimetres across the surface at a constant pressure
  • the patient is asked if they feel one or two points
61
Q

What is the two point discrimination threshold?

A

this is the minimum seperation (between the probe pairs) that is consistently reported as two points

-mimimum seperation where they can tell distinguish two seperate probe points

62
Q

What is usually the 2 point discrimination threshold on the tongue and lip?

A

2-4mm

can detect 2 points at a smaller distance

63
Q

What is the usual 2 point discrimination threshold of the skin on the lower border of the chin?

A

8-10mm

64
Q

What is the consequence of lingual nerve injury?

A

taste loss from the ipsilateral anterior segment of the tongue

65
Q

What materials can you use to assess taste stimulation?

A

Cotton wool pledgets soaked in
* 1M NaCl
* 1M sucrose
* 0.4M acetic acid
* 0.1M quinine

66
Q

Briefly describe how you can assess taste stimulation?

A
  • cotton wool pledget soaked in chosen stimulant is drawn across the lateral border ot the tongue
  • patient is asked to indicated whether sweet, salty, bitter, sour or no taste before placing tongue back in the mouth
  • stimuli should be applied in a random order to each side of tongue
  • rinsing with tap water between tests is permitted
67
Q

What is the appropriate management of the division of the IAN noted at the time of 3rd molar surgery if severed ends do not remain in apposition?

apposition: side by side

A
  • immediate microsurgical repair
  • urgent referral
68
Q

What is the appropriate management of the division of the lingual nerve noted at the time of surgery?

A
  • immediate microsurgical repair
  • urgent referral
69
Q

Where there is anaesthesia asssociated with an area innervated by the IAN, what should you do?

A
  • radiograph to determine wheter or not a bony fragment from the roof of the mandibular canal is causing an obstruction
  • if yes, refer
  • if no, monitor recovery monthly
70
Q

Where there is paraesthesia asssociated with an area innervated by the IAN, what should you do ?

A
  • monitor recovery monthly - surgery is unlikely
71
Q

What methods can be used to monitor recovery following nerve (IAN and lingual) injury monthly?

A
  • light touch sensation
  • pin prick sensation
  • two point discrimination
72
Q

Where there is paraesthesia asssociated with an area innervated by the lingual nerve, what should you do ?

A

monitor recovery (monthly)- surgical intervention unlikely

73
Q

Where there is anaesthesia asssociated with an area innervated by the lingual nerve, what should you do ?

A

surgical intervention may be required

monitor monthly

74
Q

If there is no evidence of progressive sensory recovery 3 months post IAN/lingual nerve injury, what should you do?

A

refer to a specialist centre

75
Q

When is surgery considered 3 months following an IAN nerve injury?

A
  • discontinuity of canal visible
  • persistent dysaesthesia (abnormal, unpleasant sensation)
76
Q

How should a lingual nerve that has been knowingly transected during wisdom tooth removal be repaired?

A
  • immediately using epineurial sutures
77
Q

Where the lingual nerve has been found in tact and of uniform thickness at the time of surgery but constricted by scar tissue, what resolution can be applied?

A

external neurolysis and wound closure

78
Q

How are neuromas treated?

A

they must be excised along with the damaged segment of the nerve

79
Q

Describe the characteristic appearance of neuromas?

A

they are a marked expansion at the site of injury

80
Q

What type of epineurial suture should be used to perform a repair of the lingual nerve?

A

8/0

or

9/0

sutures

81
Q

In the case of a neuroma, a segment of ____ mm in length can be excised without causing excessive tension at the repair site and without the need for a nerve graft

A

10-15mm

82
Q

If there is no evidence of progressive sensory recovery 3 months following a lingual nerve injury, how should this be managed?

A

exploration and if necessary repair

surgery should be offered to all patients with lingual nerve injury who show few signs of spontaneous repair

Minor Oral Surgery (36 decks)

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