Nerve injury

Seminar onNERVE INJURY AND

REPAIR

Presented byCathrine Diana PG I

Dept of oral and maxillofacial surgery

Cellular component: Neurons- cell body & axon Schwann cells Connective tissue Epineurium Perineurium endoneurium

Anatomy of nerve

Cranial - Motor, sensory, mixed Spinal nerves – sympathetic , parasympathetic Myelinated , non myeliniated

Nerve fibres: A - alpha – largest fibre, fastest conduction,

fine touch , position A-beta – proprioception A – delta – sharp pain , fast C fibres – slow pain

Types of nerve

Classification of nerve injury is based on the damage sustained by the nerve

components, nerve functionality, and the ability for spontaneous recovery

Classification of nerve injury

Etiologic Seddon’s Sunderlands Anatomic Samii’s Histological Based on onset(time)

Classification of nerve injury

Mechanical injury Crush/Compression injury Laceration Stretch High velocity trauma Cold injury Iatrogenic infectious

Etiologic classification

Seddon’s classification

Grade VI – complex peripheral nerve injury

Degree of nerve injury

Spontaneour recovery

Rate of recovery

Surgery

First neuropraxia Full Days to 3 months none

Second axonotmesis

full Regenerates at the rate of 1mm/month

none

third partial Regenerates at the rate of 1mm/month

None/neurolysis

fourth none Following surgery at the rate of 1mm/month

Nerve repair,graft or transfer

Fifthneurotmesis

none Following surgery at the rate of 1mm/month

Nerve repair,graft or transfer

Sixth –mixed injury

Recovery &type of surgery vary depends on combination of degrees of injury

Paralysis- loss of motor function Paresis – incomplete loss of motor function Anesthesia – loss of all sensation Hyperesthesia – excessive sensation Hypoesthesia – diminished sensation Hyperalgia- excessive sensitivity to painful stimuli Hypoalgesia – lowered pain sensitivity

Terminologies:

IAN - injured in case of mandibular fractures and ORIF, tooth extraction, injection, orthognathic surgeries,minor surgical procedures.

Lingual nerve – most commonly in third molar extraction,

Vulnerability of nerves of head and neck region to injury:

Mental N- fracture of mandible, genioplasty, minor surgical procedures, abnormal pressure from denture

Infra orbital N – fracture of infra orbital rim ASA/ PSA - osteotomy of maxilla, apicoectomy Facial N- penetrating injury, parotid surgeries,

TMJ surgeries Auriculo temporal N- TMJ surgeries

Segmental demyelination: it is the selective dissolution of the myelin sheath segment & is characterized by slowing of conduction velocity as nerve impulses travel along the de

associated with minor neuropraxia injury of axons.

Pathophysiology of nerve injury

It is a process that results when a nerve fibre is cut or crushed, in which the part of the axon separated from the neuron's cell body degenerates distal to the injury. This is also known as anterograde or orthograde degeneration

Wallerian degeneration

Some times wallerian degeneration begins in the most peripheral tissue and progress centrally from that point – common in trigeminal system caused by metabolic intoxication like metal poisoning, isoniazid and penicillin therapy

Dying back neuropathy

If the tissue deinnervated for a long period of time , certain clinical changes may take place, which are called as neurotophic effect.

Skeletal muscles – early spontaneous muscle spasm, flaccid paralysis,with progressive atrophy and lack of muscle definition and tone.

Skin & mucosa –cold, dry and inelastic, susceptibility to injury, poor healing, irregular keratinization, scaly , cracked skin.

Neurotrophic effect

Classic physical and occupational therapy: Like lubrication, protection of surface tissue from

trauma, manual stimulation of glandular tissue, warming and temperature control, electric stimulation of intact motor neuron

Starts at the coaptation site . In ideal suituation after injury, clearance of debris (by macropages & schwann cells) spourtings from proximal axon growth cones by cell elongation

Normal regeneration

secreation of neurotropic factors 7 folds in 14 days NGF,BDNF,GDNF (schwann cells in distal basal lamina)

attraction of GC towards neurotropic gradient guided by formation of fibroblast & collagen matrix

Migration of schwann cell formation of band of bungner

interaction of axon with CAM

Functional reconnection with target at basal lamina The thin nerve fibres will then gradually

thickened to their original diameter,and the investing schwann cell form the myelin sheath.

Provocation test of regeneration of nerve sprouts. Light palpation over suspected area of injury, produce distal referred tingling sensation at the target site. – indicate small nerve fibre recovery. But poorly correlate with functional recovery, may confused wit neuroma formation

Tinel’s sign:

The growing axonal sprouts may be inhibited by the scar tissue / foreign bodies which act as a barrier. When this happen the growth cone proliferate as aimless tumour along with the fibrous tissue to form a tumour called neuroma.

Abnormal regeneration

Amputation neuroma:

Various types of neuroma

Neuroma incontinuity: neuroma along the nerve line – may produce

artificial synapses Leads to abnormal chain reaction to original

stimuli. This may be a common explaination for trigeminal neuralgia,& post traumatic casualgia.

Lateral adhesive neuroma Lateral exophytic neuroma

Anaesthesia dolorosa -it is a constant boring penetrating or grinding pain in the distribution of numbness .

Post traumatic pain syndromes

Triggered tick like neuralgiform pain: some case with in first week after nerve injury,

pt may experience stabbing , flashing pain secondary to mechanical irritation/ inflammation in the still intact nerve trunk.

Peripheral microneurosurgery is effective in pt with neuromas, pharmacological therapy are most appropriate in cases of central neuropathology

means burning sensation pain begins at least 2 weeks after

penetrating missile inury in mixed peripheral nerves, region

due to the artificial synapse of demyelinated somatic sensory nerve segment with unmyelinated efferent sympathetic fibre

Casualgias

sense of awareness of missing body part after amputation is called phantom phenomenon.

Paroxysomal stabbing , itching deep burning of missing part appx 10 mins of duration. Triggered by tactile sensation

phantom pain syndrome:

1.Clinical neurosensory testing Level A,B,C 2.McGill pain questionnaire 3.Visual analogue scale 4.Electrophysiological testing: EMG SSEP NCS 5. MRN

Subjective assessment : visual analogue scale

Objective assessment: Level A : static two point discrimination brush stroke directional discrimination Level B : contact detection Level C: pin prick nociception, thermal

discrimination

surgicalNon surgical

treatment

Local anaesthesia - EMLA Analgesics-The use of analgesics can help patients control

pain Anticonvulsants –now a days carbamazepine is the drug of

choice 200- 800 mg/ day Corticosteroids – reduce the inflammation Narcotic analgesia Muscle relaxant Tranquilizers – benzodiazepienes used in chronic pain Antidepressents

 when to go for surgery?

Evaluation of Closed Injury

Neurolysis is performed on intra-neural and extra-neural scar tissue to release regenerating nerve fibres in the hope of improving functional recovery

External Internal

Neurolysis / decompression

External neurolysisIt is the process of nerve decompression. Microdissection of nerve involves liberation of nerve from the surrounding scar tissue , fixation of fracture segmentDone under magnification 4X & 8X

turnover epineural sheath tube in primary repair of peripheral nerves. Ann Plast Surg. 2002 Apr;48(4):392-400Yavuzer R1esAyhan S (Latifoğlu Ox8Atabay K

Indicated in case of incomplete return of normal sensory function of previously injured nerve. Under magnification,12x/ 16x epineurium dissected longitudinally to release the adhesion around or within the fascicles

Internal neurolysis:

Epifascicular epineurotomy Epifascicular epineurectomy Inter fascicular epinuerectomy

Goals of Primary nerve repair < 1 wk Proper coaptation Vascularity Free of tension

Nerve repair

Failure to perform primary repair Late Repair > 1 wk Crush injury

Secondary nerve repair

Glial scars Astrocytes form a barrier preventing further

growth by forming gap junctions Tension in the rejoined nerve

Challenges in nerve repair:

Anastomosis of proximal and distal nerve ending

Epineurial Fascicular Perineuial

neurorraphy

Epineurial Approach

adequate exposure Proper anesthesia Magnification with loupes 8x- 10 x The nerve ends are then sharply transected

perpendicular to the long axis. Minimum of two epineural sutures with 8-0/ 9-0

nylon 180° to each other. Careful alignment is the critical factor in this

first step

Perineurial repair involves the individual fascicles and placing sutures through the perineurium, the protective sheath surrounding fascicles

Drawback: Trauma to nerve Fibrosis Tissue reaction

perineurial repair:

Least accessible fascicle – suture first Fewest suture as possible

fasicular repair

Single site of suturing Better coaptation & vascularity Less chance of mismatch & collateral axonal

micro sprouting outside epineurium.

Merits of neurorraphy over grafting

Reconstruction after peripheral nerve injury may require management of segmental defects or "gaps" in the injured nerve

A nerve graft will be about 10 % longer than the gap between the nerves, and the cross-section of the nerve end will be a quite larger than the diameter of the nerve graft to allow for growth

Nerve grafting..

Sural nerve Greater auricular nerve Antebrachial cutaneous nerve

Donor Nerve

Sural nerve

2.1mm

Greater auricular N1.5 mm

Greater auricular cable 3mm

Inferior alveolar nerve 2.4 mm

88% 63% 125%

Lingual nerve3.2mm

66% 47% 94%

.Tension of the suture line and inadequate preparation of the nerve stumps are the 2 leading causes of regenerative failure across the suture site, resulting in poor recovery of nerve function.

The nerve graft act as a distal nerve stump, so it ll undergo wallerian degeneration, to provide a conduit for axon regeneration, schwann cell regeneration is critical for this

Limitations:

Need for adequate revacularisation – initially occurs through diffusion from tissue bed reaches supranormal in 4-5 days.

Grafr size – in case of increased graft size , central necrosis occurs due to increased volume of tissue beyond perfusion

Sensory loss, scarring and neuroma formation can cause morbidity to the donor site of the patient the nerve is harvested from

Primary repair Interpositional grafting Cross facial nerve repair Cross over graft or split graft

Facial nerve repair

The use of allograft nerve material is particularly appealing because of its available quantity and lack of donor site morbidity.

Need for prolonged immunosuppression required to maintain Schwann cell viability limits clinical implementation of this method.

Allografting:

Various materials are used as conduits, Autogeneous materials – muscles , fascia, veins

collagen Alloplastic material –polyglycolic acid,

Polyester,PTFE , scilicone Used in case if the gap is 0.5mm- 3mm

Entubulation/conduits

Type of injury Time of surgery. Patient age, level of injury, mechanism of injury, and associated medical conditions all

influence outcome.

Factors influence recovery:

evaluated by static 2-PD- perceived by Merkel cell, , moving 2-PD- Meissner corpuscle and pinprick. - Free nerve endings transmit

painful stimuli Innervation testing – monofilament testing

Assessment of recovery:

Postoperative management after nerve repair or reconstruction is aimed toward wound healing, and re-establishing longitudinal excursion of the nerve

Repairs are immobilized for approximately 3 weeks by splinting.

Nerve Repair and Grafting in the Upper Extremity S. Houston Payne, Jr., MD J South Orthop Assoc. 2001;10(2) 

Aftercare and Rehabilitation

Sensory re-education is designed to help the patient recognize new input in a useful manner

Sensory re-education is carried out in three stages:

desensitization, early-phase discrimination localization, late-phase discrimination tactile gnosis

Sensory Re-education

Transcutaneous nerve stimulations (TNS) – cutaneous bipolar surface electrodes are placed in painful regions of body &low voltage electric current is administered. Best results will obtained if intense of stimulation is maintained for 1 hour daily > 3 weeks

Latest advancements:

Coaptation of nerve tissue without suture is appealing and would potentially eliminate the trauma associated with traditional suturing technique. (1) more efficient,

(2) eliminate variables of tension due to suture placement and technique,

(3) improve alignment of fascicles

Sutureless Nerve Repair

The two techniques that have been most carefully evaluated are coaptation by fibrin glue and by laser gallium-alluminium arsenide at 820 nm wavelength

Aiding with growth factors – N-acetylmuramyl-L-alanyl-D-isoglutamine

Stem cells

Cell therapy

Frozen nerve repair Metabolic manipulations using pulsating electric fields – include

growth factors to influence neurite growth Vascularized nerves can be useful to repair nerves longer than 8

cm and grafts placed in poor vascular beds that are heavily scarred

Microsurgery 989;10(3):220-5. Sciatic nerve regeneration in the rat. Validity of walking track

assessment in the presence of chronic contractures. Dellon AL1, Mackinnon SE

Studies in trial

Immediate primary repair in sharp injuries

with suspected transsection of nerve

because delay leads not only to retraction

but also to severe scaring

Bluntly transsected nerve best repaired

after a delay of several weeks.

Summary..

A focally injured nerve should be explored if no

functional return within 8-10 weeks

Decision - making as to whether neurolysis or

resection & repair in a lesion in gross continuity based

on intraoperative electrophysiological evaluation

Split repair with usually graft – lesion in

continuity ,partial function or undergoing partial

regeneration

Careful patient selection for operation Nerve anastomosis failure ① inadequate resection of scarred nerve

ends ② nerve suture distration A good end result requiring rehabilitation from

onset of treatment. Prevention of disuse, relief of pain, predicting

probable end results of operative procedures

References: Peterson’s principle of oral &maxillofacial surgery 2nd edt Text book of Oral and maxilla facial surgery – Gustav kruger 6th edt Nerve injury and repair – sussan E mackinnon, Washington university school of

medicine Peripheral nerve injuries anr repair – Adam osbourn – review of surgeries turnover epineural sheath tube in primary repair of peripheral nerves. Ann Plast

Surg. 2002 Apr;48(4):392-400 Nerve Repair and Grafting in the Upper Extremity S. Houston Payne, Jr., MD J South

Orthop Assoc. 2001;10(2)  Static and dynamic repairs of fascial nerve injury -Hillary White, Eben Rosenthal-

oral & maxillofacial surgery clinics of north America 25(2013) 303- 312 Lingual nerve repair to graft or not? Michael millaro DMD et al YJOMS

Thank you