Electrodiagnostic Studies & P rognostication in F acial n. L esions

1. Electrodiagnostic Studies &Prognostication in Facial n. Lesions By S. Khosrawi MD , Physiatrist Dept. of Physical Medicine & Rehabilitation Isfahan University of Medical Sciences

2. The purposes : • Brief Anatomy • Describe models for determination of the degree of nerve fiber injury • To clarify some aspects and limitations of prognosticationvalue of EDXtesting

3. between the nerve's exit from the brainstem to the point where it enters the internal auditory meatus • between the internal auditory meatus and the stylomastoid foramen • begins at the facial nerve's appearance at the stylomastoid foramen • Intracranial • Intratemporal • Intrameatalthe narrowest point in facial canal • Labyrinthin • Tympanic • Mastoid • Extracranial

9. Prior to formulating an appropriate treatment plan, an accurate diagnosis of the lesion's magnitude and completeness should be determined and a prognosis arrived at. The best quantitative method available for accomplishing both of these goals is electrophysiologic testing.

10. House-Brackmann facial grading scale

11. Models for determination of the degree of nerve fiber injury • Seddon • Saunderland

12. Seddon Saunderland 1° 2° 3° 4° 5° Neurapraxia block Axonotmesis axons endoneurium Neurotmesis perineurium epineurium

13. Histopathologic studies of Bell’s palsy and herpes zoster oticus suggest that nerve injuries as severe as 4th.degree injury may occur in these pathologies.

15. Evaluation of facial palsy • Single most important prognostic factor is : whether the palsy is complete or incomplete ? • Incomplete palsies have satisfactory recovery of facial function; Complete recovery in 80-90% • Complete paralysis often portends a poorer prognosis, and requires quicker assessment and management. • Electrophysiologic tests (ENoG, NET, MST, EMG): helps determine endpoint of degeneration and prognosis for return of motor function, usually in preparation for surgery.

16. Electrodiagnostic testing encompasses main roles in the evaluation and management of patients with neuromuscular disease : • Most frequently, EDX testing is used as an extension of the neurological examination. • EDX testing can……assist in making a diagnosis while.………………excluding alternatives, provide…………….prognostic information, and can…………….guide and monitor treatment.

17. Facial Nerve CMAP In the otorhinolaryngology literature evoking a facial nerve CMAP may be referred to by different terms: Electro-Neurono-Graphy (ENoG) Electro-Neuro-Graphy (ENG) Evoked-Electro-Myo-Graphy (EEMG) Irrespective of the terminology, they all represent stimulation of the facial nerve and recording a compound muscle action potential (CMAP) from some facial muscles

19. EEMG ( ENoG ) : Considered to be an accurate prognostic test peak-to-peak or baseline-to-peak amplitudecomparison first time at 3rd. day post-onset and again at 3-5 day intervalsuntil a trend can be obtained most reliable during the first 2–3 weeks(especially on the 5th. day) After 3rdwk.regeneration or sprouts(controversy)little clinical use . **Patients with clinically incomplete paralyses due to Bell’s palsy invariably recover function to normal or near-normal levels and do not require EEMG. >90% ===>poor prognosis(80%) ===> ? decompression <90% ===>excellent recovery (90%) ===> conservative Rx.

20. The above concepts apply primarily to patients with Bell's palsy, but may be applied to persons with trauma or Ramsay Hunt syndrome. • The indications for surgery in these patients, however, are slightly different. • In trauma patients, axonal loss of greater than 90% within the first 6 days is believed to indicate the need for surgical intervention. • Ramsay Hunt syndrome can be considered similar to Bell's palsy.

21. Nerve Excitability Test ( NET ) : most commonly performed electrical test Timing < 3 wks. , but Not useful in the 1st 3 days or during recovery The lowest electric current (threshold) necessary to elicit a facial twitch … If ∆ > 3.5 mA ===> poor prognosis for return of facial function; Shortcomings: > 40% false negative, time lag with CMAP abnormalities, masseter muscle, somehow subjective *NOT RELIABLE !

22. Maximal Stimulation Test ( MST ) : (modified form of NET but superior to it) “patients‘ tolerance” Maximal clinical response evaluated on the 5th , 7th , 10th , and 14th day Graded as : (1)equal to the contralateral side, (2)minimally diminished (>50% of normal), (3)markedly diminished (< 25% of normal), (4)absent Grades 3 or 4 advanced degeneration and poor prognosis (75% ) Grade 1  complete return ( > 90% ) Shortcomings: Not Objective and reliable , subject to significant error

23. * Don’t forget : • ENoG , NET& MST are most useful in evaluating acute paralysis while nerve is in degenerative phase (i.e. < 3 wks. ) • ENoG , NET & MST will show normal results for the first 3-4 days after nerve injury. • ENoG , NET & MST will only work if the patient has unilateral involvement.

24. Electromyography: Indication: Acute paralysis less than 1 wk. or after 3 wks. 1* If voluntary active motor units during the first 3-4 days===> intact motor axons (incomplete injury) 2* If not ===> ??? ( EMG cannot differentiate complete Neurapraxiaand/or axonal loss) 3* If polyphasic potentials ===> regeneration (4-6 weeks) Good for follow-up

25. Nerve conduction time (latency) : Upper limits of normal: adults: 4 msec , neonates/infants: 7-10 msec.; *The least reliable prognostic test !*

26. Blink reflex

27. Blink reflex: One of prognostic tests that measures central pathology of facial nerve Absent R1 ===>little chance of recovery in the first 2 months Preserved R1 ===>return within the first month * Considered investigational *

28. Prognosis It is usually possible to reliably state a prognosis in about 80% of patients by the end of the first week and in over 95% of patients by the end of the 12th day of palsy.

30. Bell's Palsy: Putting It All Together* • < 90% axonal loss  89% H-B grade I, and 11% grade II • >90% axonal loss  If treated with steroids  42% H-B grade I or II • >90% axonal loss  If surgery within 14 days 91% H-B grade I or II • >90% axonal loss  If surgery after 14 days same as medical Rx. *GantzBJ, Rubinstein JT, Gidley P, Woodworth GG: Surgjcal management of Bell's palsy. Laryngoscope

31. Congenital vs. traumatic facial paralysis • Electrophysiologic testing within the first 3 days of life • In traumatic injuries, the nerve can be stimulated for 3-5 days post- injury with fibrillation potentials visible at 10- 14 days. • In congenital causes, the ability to stimulate the nerve will probably be absent at birth with no fibrillation potentials visible on EMG.