Lingual Nerve Injury

Steven B. Graff-Radford, DDS, Randolph W. Evans, MD

Disclosures

Headache. 2003;43(9) 

In This Article

Classification

In 1943, Seddon classified nerve injury as: (1) neuropraxia -- conduction block resulting from mild trauma, without axonal damage, and with resolution of sensory deficit within days to months; (2) axonotmesis -- more severe injury, with preservation of the nerve sheath but afferent fiber degeneration, and incomplete sensory recovery; neuroma formation may occur, and the typical clinical presentation involves severe dysesthesia; (3) neurotmesis -- most severe injury, with nerve severance and anesthesia in the nerve distribution, and no sensory recovery (especially if the nerve course is in soft tissue; if the nerve course is in bone, regeneration may occur).[14]

In 1951, Sunderland classified nerve injury based on the degree of tissue injury.[15] Under his system, first-degree injury, of which there are 3 types, is similar to Seddon's neuropraxia. Type 1 results from nerve trunk manipulation, mild traction, or mild compression and is thought to reflect transient ischemia. If blood flow is restored, nerve function usually returns to normal; with more prolonged ischemia, permanent injury and anesthesia may occur. Type 2 results from more prominent traction or compression that produces intrafascicular edema, decreased blood flow, and a conduction block. Recovery is variable. Type 3 injuries result from severe nerve traction or compression causing segmental mechanical disruption of the myelin sheaths and demyelinization. Recovery is delayed and sensory loss may be permanent.[16]

Second-, third-, and fourth-degree injuries correspond with Seddon's classification of axonotmesis. The afferent or efferent fibers are damaged, but endoneurium, perineurium, and epineurium remain intact. Surgical decompression may be necessary, and recovery requires axonal regeneration.Third-degree injury occurs when the intrafascicular tissue components (axons and endoneurium) are damaged. If there is poor clinical recovery, surgical reconstruction may be needed. Fourth-degree injury implies fascicular disruption: all components are damaged and only the epineurium remains intact. The prognosis is poor, and surgical reconstruction may be indicated.

Fifth-degree injury implies nerve transsection. Surgical approximation and coaptation may be required.

MacKinnon and Dellon, in 1988, added sixth-degree injury to describe a variation wherein a combination of Sunderland's 5 degrees of injury coexist within the same nerve trunk.[17]

Attempting to correlate histological findings with clinical data, Rood concluded that the clinical course is most reflective of the degree of initial injury.[18] If there is complete numbness that improves over time, this is indicative of first- or second-degree injury per the Sunderland classification. The presence of complete numbness initially does not indicate nerve severance.[5]

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