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OMFS Year 2 > Nerves > Flashcards

Nerves Flashcards

1
Q

What is the etiology of nerve injuries?

A
  1. Odontectomy (removal of impacted tooth) - 3rd molars most concern because closest to IAN and PSA
  2. Trauma - fracture of jaw
  3. Implants - near inferior alveolar canal
  4. Reconstruction - removal of cysts, tumors –> nerves get resected sometimes
  5. Other (injection injury, root canal therapy, I & D) - root canal treatment can sometimes pass the apex of the tooth
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2
Q

What nerve is hard to visualize/detect?

A

The lingual nerve is hard to see because it’s very close to the alveolar crest and it’s usually low and medial. 20% of patients could also have it above the crest. The IAN is at least detectable radiographically.

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3
Q

When you extract 3rd molars what nerves should you be careful of?

A

IAN is always at risk for permanent parenthesia but also the lingual nerve

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4
Q

What kind of bony impact is the most likely to have altered sensation in patient after extraction?

A

Fully bony impaction > partial bony impaction > soft tissue impaction > erupted

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5
Q

What is the most common cause of nerve injuries?

A

Iatrogenic, most often because of dental treatment

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6
Q

Post-operation nerve injuries are more frequent in which nerve?

A

IAN

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7
Q

Nerve injuries after a year from surgery is most common in which nerve?

A

Lingual nerve

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8
Q

Patient comes in with an impacted third molar near the canal. The patient is asymptomatic, do we extract? Why?

A

No we do not need to extract. This is because if it is near the IAN canal and patient is asymptomatic there is no need to take the risk

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9
Q

When should we extract a 3rd molar near the IAN canal?

A

If there is a pathology or the position of the tooth will impact the long-term health of the 2nd molars

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10
Q

True or false: possible anterior crowding is indicative of 3rd molar extraction

A

False - 3rd molars will not cause anterior crowding

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11
Q

What is a partial odontectomy?

A

It is the resection of crown below CEJ – the residual root surface established at 3-4mm below Buccal and lingual alveolar crest.

You side step the risk of leaving the portion of the tooth near the nerve alone – incidence of infection is a little higher than taking the whole teeth out but still not that high.

Migration of teeth occurs within the first 12months, the remaining root migrates up

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12
Q

True or false: taking out the implant that has breached the IAN site will help alleviate some effects?

A

False - you will probably tear up the nerve even more

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13
Q

What are some possible injuries that occur due to implant therapy?

A
  1. Mental nerve trauma associated with ridge incision (edentulous mandibles)
  2. Mental nerve injuries associated with retraction (to get access to procedure)
  3. ***Most common is direct mechanical trauma – drill is longer than implant so much take into consideration
  4. Thermal injury - drilling on top of IAN so heat is transferred to the nerve
  5. IAN transposition/lateral inaction procedures
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14
Q

What are the different mechanisms/possiblities of nerve injury through injections?

A

Injection injury is mechanical injury from the needle that can result/stem from:

  1. Intra-neural hematoma formation
  2. Extra-neural hematoma formation
  3. Local anesthetic toxicity
    • higher concentration LA more toxic than others (septocaine)
    • relationship of position of lingual nerve and landmarks when we use IAB are highly variable which often results in trauma to lingual nerve.
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15
Q

What nerve is damaged more from an IAB?

A

Lingual nerve

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16
Q

True or false: if you want to avoid possible nerve damage, sealants are non-toxic to nerves with endodontic therapy?

A

False - sealants are highly toxic and causes inflammation

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17
Q

How does endodontic therapy result in possible nerve damage?

A

Sealants are often used to stop bacteria but if you perforate through the apex and apply a sealant then the sealant has a direct path to the nerve which is bad.

If patient feels numb/pain, need to get patient to OR or could have neuropathy

18
Q

How do you take history for trigeminal nerve injury?

A
  1. Date of injury
  2. Mechanism of injury
    - it is important to know mechanism because if it’s endo and there is an injured nerve you need to treat ASAP vs. impacted 3rd molar
  3. Symptom history
  4. History of prior treatment and response
    - time does matter, you can’t go back and fix nerves if they have been disconnected for a long time
  5. Functional deficit
  6. Psychological impact
19
Q

What examination must you give after a surgical procedure that involves risk to nerves?

A

Sensory nerve examination – challenge patient with different stimuli to see how nerve is working

20
Q

What different types of clinical exams can you give the patient to test nerves?

A
  1. Static light pressure (slow adapting mechoreceptors)
  2. Pin prick nocieception (small diameter fibers – A delta, C)
  3. Tinsel sign - shooting sensation or pain distally upon palpation of the injury site
  4. Directional determination - specific receptors innervated by larger myelinated fibers (A delta, B) and rapidly adapting mechanoreceptors
  5. Two point discrimination - large myelinated axons innervating pacinian corpucles
  6. Diagnostic nerve block – failure of a peripheral nerve block to alleviate pain suggests a psychosocial, sympathetic or centrally mediated pain process
  7. Somatosensory evoked potentials (SEP) - quantitative assessment of nerve integrity
21
Q

What are the 3 classifications of neural injuries?

A
  1. Neuropraxia
  2. Axonotmesis
  3. Neurotmesis
22
Q

What is neuropraxia?

A
  1. Immediate deficit in nerve conduction
  2. Anatomic continuity maintained
  3. No wallerian degeneration (when nerve is cut or crushed that the axon is separated from neurons cell body and degenerates)
  4. Spontaneous recovery

***like falling asleep on your arm, 100% recovery, no need surgery

23
Q

What is axonotmesis?

A
  1. Contusion or crush injury
  2. Basic architecture of endoneural sheath is maintained
  3. Wallerian degeneration distal to the point of injury
  4. May recover spontaneously within 2-6 months but the quality and degree of regeneration varies

We want to try and give them back some sensation and have them pain free

24
Q

What is neurotmesis?

A
  1. Physical disruption of the nerve trunk
  2. Wallerian degeneration distal to the point of injury
  3. Prognosis for regeneration depends on the quality of the transection and the orientation of the distal and proximal nerve segements
25
Q

What is the mechanism of nerve injury?

A
  1. Compression
  2. Contusion
  3. Crush
  4. Partial transection
  5. Complete transection
26
Q

What is a neuroma?

A

Neuroma is nerve scar tissue that is thick. There is a haphazard arrangement of nerve fibers after nerve injury in attempt to repair defect.

27
Q

True or false: there is a high sensory threshold (requires more stimulus to feel) than normal tissue due to thick scar tissue?

A

False- sensory thresholds are much lower compared to normal tissue

28
Q

What time frame should you wait for lingual nerve surgery? For IAN surgery?

A

Wait 3 months for lingual surgery if there is no improvement in monthly exams

Wait 6-12 months for IAN surgery if there is no improvement in monthly exams

29
Q

If patient comes in with nerve injury but is not in paint, what is the course of treatment?

A

Start with clinical exam and mapping. If there is improvement with monthly visits you just continue until nerve regenerates (1mm a day, 8-12 months)

If no improvement, consider surgery of lingual nerve or IAN

30
Q

If patient comes in with pain (dysesthesia) what is the course of treatment?

A

Start with clinical exam and mapping. If there is improvement then just follow monthly visits until patient is comfortable.

If there is no improvement you either alleviate pain with local anesthesia – tinel sign and do surgery. Or you can do a non-surgical treatment which is medical treatment directed at decreasing pain.

31
Q

What does anti-seizure medication do in treatment of painful nerve injury?

A

It increases the excitatory threshold

32
Q

What are the indications for microneurosurgery?

A
  1. Witnessed nerve injury with anesthesia and/or pain
  2. Dysesthesia alleviated by diagnostic nerve block
  3. No improvement or deterioration at monthly exam
  4. Immediate reconstruction
33
Q

What are the methods of repair in microneurosurgery?

A
  1. Surgical decompression if nerve is compressed
  2. Neurorraphy with primary repair
  3. Neuroma excision with primary repair
  4. Neuroma excision with an interpositional nerve graft
34
Q

Where do you incise to being surgery for access to lingual nerve?

A

Behind the 2nd molar – lateral to it. Nerve is usually right under periosteum in 3rd molar region.

35
Q

What is the different in surgery/repair of IAN vs. lingual nerve?

A

IAN is in a bony canal, it is a rigid structure that guilds regeneration of the IAN.

However, lingual nerve does not have the guidance process and that’s why lingual nerve injuries don’t recover as much as IAN

36
Q

True or false: it is common to use grafts for lingual nerve?

A

False - you usually use grafts for nerves in a bony canal (ex. IAN)

37
Q

What do you use to access the IAN in IAN surgery?

A

for decorticating use piezoelectric to cut bone but it does not cut soft tissue.

38
Q

If you were grafting for IAN surgery, what would you do?

A

A sural nerve graft from the foot

39
Q

Which patients have a higher surgical success rate, anesthesia or dysesthesia?

A

Anesthesia

40
Q

True or false: the shorter you wait to do surgery for anesthesia surgery patients, the better chance for success

A

True - earlier the better, beyond a year the outcome is not good

OMFS Year 2 (7 decks)

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