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ENT
Electrophysiological Testing of the Facial Nerve
Built from Haynes-Glasscock-Shambaugh Surgery of the Ear, Seventh Edition
What’s inside
9 sections · 76 slides
Overview
- Scope of this topic
Clinical background
- Idiopathic facial palsy
- Paresis versus complete paralysis
- Who should be tested
Classification of neural injury
- Seddon and Sunderland schemes
- First degree injury: neuropraxia
- Second degree injury: axonotmesis
- Third to fifth degree injury: neurotmesis
- Endoneurial integrity and synkinesis
- Sunderland degrees of neural injury and recovery groups
- Peripheral nerve in cross section
- Limits of injury classification in practice
Wallerian degeneration
- Wallerian degeneration as the test substrate
- Axon fragmentation distal to nerve injury
- Consequences for test selection
Historical development
- Early electrical stimulation of the facial nerve
- Obstacles to electrodiagnosis
- Facial nerve within the petrous temporal bone
- Topognostic testing
- From excitability testing to electroneurography
Electroneurography
- Principle of electroneurography
- Electroneurography as evoked electromyography
- Recording electrode technique
- Consequences of fixed recording electrodes
- Calculating percent degeneration
- CMAP amplitude and conducting fibres
- Test-retest reliability
- Surface electrode recording of muscle potentials
- What electroneurography cannot detect
- Fisch and Esslen degeneration threshold
- Revised threshold in Bell's palsy
- Prognosis below the degeneration threshold
- Rate of degeneration and injury severity
- Time course of neural degeneration after complete paralysis
- Interpreting serial electroneurography
- Timing of the first study
- Serial testing algorithm in acute paralysis
- The surgical decompression decision
- Situations where electroneurography is invalid
- Deblocking
- Early deblocking and its surgical implication
- Aetiologies without proven ENoG prognostic value
Electromyography
- Principle of electromyography
- Needle electromyography technique
- Fibrillation potentials
- Timing of electromyographic changes
- Complementary timing of ENoG and EMG
- Electromyography in the acute phase
- Polyphasic potentials and reinnervation
- Chronic paralysis and muscle atrophy
- Electromyography and reanimation planning
- Grafting the neuromuscular unit
Nerve excitability and maximum stimulation tests
- Nerve excitability test
- Interpretation of nerve excitability testing
- Maximum stimulation test
- Prognostic value of maximum stimulation testing
- Why ENoG supplanted NET and MST
- Facial nerve in the facial canal
Putting the tests together
- Sequence of testing in acute complete paralysis
- Roles of the tests by phase of illness
- Key numerical thresholds
- Conclusions
- References
- References (continued)
- References (continued)
- References (continued)
- Haynes-Glasscock-Shambaugh Surgery of the Ear, Seventh Edition
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