NERVE INJURIESNERVE INJURIES

Dr V.RAMKUMARDr V.RAMKUMAR CONSULTANT DENTAL CONSULTANT DENTAL

&FACIOMAXILLARY SURGEON&FACIOMAXILLARY SURGEON REG NO-4118 TAMILNADU –INDIA(ASIA)REG NO-4118 TAMILNADU –INDIA(ASIA)

NERVENERVE

Nerve is a bundle of fibres that uses Nerve is a bundle of fibres that uses chemical &electrical signals to transmit chemical &electrical signals to transmit sensory & motor information from one sensory & motor information from one body part to another. body part to another.

NERVE INJURYNERVE INJURY

Nerve injury can be defined as damage to Nerve injury can be defined as damage to a sustained component of the nerve which a sustained component of the nerve which may or may not be recovered functionally may or may not be recovered functionally after any type of injury ( mechanical after any type of injury ( mechanical electrical ,thermal).electrical ,thermal).

Mesoneurium- suspends the nerve trunk Mesoneurium- suspends the nerve trunk with in the soft tissue & contains the with in the soft tissue & contains the segmental blood supply of the nerve.segmental blood supply of the nerve.

Epineurium- loose connective tissue that Epineurium- loose connective tissue that defines the nerve trunkand protects defines the nerve trunkand protects against mechanical stress,against mechanical stress,

Perineurium is a contiuation ofpia Perineurium is a contiuation ofpia arachanoid of cns , perineurium helps in arachanoid of cns , perineurium helps in active transport of certain molecules.active transport of certain molecules.

Endoneurium –composed of external layer Endoneurium –composed of external layer of collagen and internal layer of of basal of collagen and internal layer of of basal lamina and endoneural capillaries.lamina and endoneural capillaries.

VARIOUS TERMINOLOGYVARIOUS TERMINOLOGY

Allodynia –pain due to a stimulus that Allodynia –pain due to a stimulus that normally do not provokenormally do not provoke

Analgesia-absence of pain in response to Analgesia-absence of pain in response to the stimiulationthat would normally be the stimiulationthat would normally be painful or non pain fulpainful or non pain ful

Anaesthesia-total loss of all types of Anaesthesia-total loss of all types of sensation in response to stimulationsensation in response to stimulation

Paresthesia-altered sensation which is not Paresthesia-altered sensation which is not pleasant like tingling crawlning burningpleasant like tingling crawlning burning

Dysaesthesia- an unpleasent painful Dysaesthesia- an unpleasent painful abnormal sensation either spontaneous or abnormal sensation either spontaneous or evokedevoked

Hyperaesthesia-an increase sensitivity to Hyperaesthesia-an increase sensitivity to stimulusstimulus

Hypoaesthesia-decreased sensitivity to Hypoaesthesia-decreased sensitivity to stimulus.stimulus.

Hypo-&hypergesia-decreased or increases Hypo-&hypergesia-decreased or increases response to a stimulus that is normally response to a stimulus that is normally painful.painful.

Ageusia-loss of tasteAgeusia-loss of taste

Neuritits- inflammmation of a nerve.Neuritits- inflammmation of a nerve.

Neuralgia-transmission of pain impulse Neuralgia-transmission of pain impulse passed along the course of the nerve.passed along the course of the nerve.

Neuromas are characterized by Neuromas are characterized by disorganized microsprouting ,formation of disorganized microsprouting ,formation of disorganized collagen&randomly oriented disorganized collagen&randomly oriented small neural fascicles.small neural fascicles.

ETIOLOGYETIOLOGY

maxillo facial surgery which run the risk of maxillo facial surgery which run the risk of injury to the sensory branch of trigeminal injury to the sensory branch of trigeminal nerve includesnerve includes

Inferior alveolar nerveInferior alveolar nerveLingualnerveLingualnerve Infraorbital nerveInfraorbital nerveAuriculotemporalnerveAuriculotemporalnerve

WALLERIANDEGENERATIONWALLERIANDEGENERATION

. It is a process by which the damaged . It is a process by which the damaged segment of a nerve is phagocytosed, segment of a nerve is phagocytosed, beginning at the first intact node of beginning at the first intact node of Ranvier. The Schwann cell tubes also are Ranvier. The Schwann cell tubes also are phagocytosed to prevent obstruction of the phagocytosed to prevent obstruction of the regenerating axon. Many different growth regenerating axon. Many different growth factors and cytokines affect this process of factors and cytokines affect this process of degeneration-regeneration. degeneration-regeneration.

WALLERIAN DEGENARTIONWALLERIAN DEGENARTION

CLASSIFICATION OF NERVE CLASSIFICATION OF NERVE INJURIESINJURIES

Seddon classification is based on the time Seddon classification is based on the time course and completeness of sensory course and completeness of sensory recovery.recovery.

Sunderland it also includes the same Sunderland it also includes the same feature but includes the amount of nerve feature but includes the amount of nerve tissue damaged and tissue still intact tissue damaged and tissue still intact

NEUROPRAXIANEUROPRAXIA

Neurapraxia is a reduction or complete Neurapraxia is a reduction or complete block of conduction across a segment of a block of conduction across a segment of a nerve with axonal continuity conserved. nerve with axonal continuity conserved. More specifically, it is dysfunction and/or More specifically, it is dysfunction and/or paralysis without loss of nerve sheath paralysis without loss of nerve sheath continuity and peripheral wallerian continuity and peripheral wallerian degeneration. Nerve conduction is degeneration. Nerve conduction is preserved both proximal and distal to the preserved both proximal and distal to the lesion but not across the lesionlesion but not across the lesion

AXONOTMESISAXONOTMESIS

Axonotmesis is a more severe grade of nerve Axonotmesis is a more severe grade of nerve injury compared with neurapraxia. Axonotmesis injury compared with neurapraxia. Axonotmesis is a result of damage to the axons with is a result of damage to the axons with preservation of the neural connective tissue preservation of the neural connective tissue sheath (endoneurium), epineurium, Schwann sheath (endoneurium), epineurium, Schwann cell tubes, and other supporting structures. cell tubes, and other supporting structures. Thus, the internal architecture is relatively Thus, the internal architecture is relatively preserved. This can guide proximal axonal preserved. This can guide proximal axonal regeneration to reinnervate distal target organs. regeneration to reinnervate distal target organs. Distal wallerian degeneration occurs in Distal wallerian degeneration occurs in axonotmesis axonotmesis

NEUROMETOSISNEUROMETOSIS

Neurotmesis is the most severe grade of Neurotmesis is the most severe grade of peripheral nerve injury. It occurs when the peripheral nerve injury. It occurs when the axon, myelin, and connective tissue axon, myelin, and connective tissue components are damaged and disrupted components are damaged and disrupted or transected.Recovery through axonal or transected.Recovery through axonal regeneration cannot occur. This grade of regeneration cannot occur. This grade of injury includes nerve lesions in which injury includes nerve lesions in which external continuity is preserved but external continuity is preserved but intraneural fibrosis occurs and blocks intraneural fibrosis occurs and blocks axonal regeneration axonal regeneration

SUNDERLAND GRADING OF SUNDERLAND GRADING OF INJURIESINJURIES

Sunderland (1951) categorized nerve Sunderland (1951) categorized nerve injuries into 5 grades. Grades I and II injuries into 5 grades. Grades I and II correspond to Seddon's neurapraxic and correspond to Seddon's neurapraxic and axonotmetic grades of injury. Sunderland axonotmetic grades of injury. Sunderland further divided Seddon's category of further divided Seddon's category of neurotmesis injuries into grades III, IV, and neurotmesis injuries into grades III, IV, and V based on the extent of damage to the V based on the extent of damage to the axonal supporting structures axonal supporting structures