INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING FOR MICROVASCULAR DECOMPRESSION SURGERY IN PATIENTS WITH HEMIFACIAL SPASM

Transcription

1 INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING FOR MICROVASCULAR DECOMPRESSION SURGERY IN PATIENTS WITH HEMIFACIAL SPASM WILLIAM D. MUSTAIN, PH.D., CNIM, BCS-IOM DEPARTMENT OF OTOLARYNGOLOGY AND COMMUNICATIVE SCIENCES UNIVERSITY OF MISSISSIPPI MEDICAL CENTER

2 DISCLOSURE I have no relevant financial or nonfinancial relationship(s) within the products or services described, reviewed, evaluated or compared in this presentation. William D. Mustain, Ph.D., CNIM, BCS-IOM Professor, Department of Otolaryngology and Communicative Sciences University of Mississippi Medical Center

3 BASIS OF INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING Reduce the risk of postoperative neurological deficits Help the surgeon carry out the operation

4 HEMIFACIAL SPASM (HFS) A syndrome of unilateral facial nerve hyperactive dysfunction Spasm begin as slight intermittent twitching of single facial muscle, becomes more intense over time and spreads to other muscles of facial expression Typical HMS starts in orbicularis oculi and spreads to frontalis and neck Atypical HMS starts in the lower face and spreads to orbicularis oculi Prevalence rate is 10 patients per 100,000 in the US population

5 PATIENT WITH HEMIFACIAL SPASM LEFT SIDE

6 SEVERE HFS- TONUS PHENOMENON

7 WHAT CAUSES HFS? Etiology - vascular compression of facial nerve - AICA and PICA are most common offending vessels Pathophysiology - peripheral theory - central theory

8 ELECTROPHYSIOLOGICAL FINDINGS IN HFS Clinical EMG studies show spontaneous, high frequency, synchronized firing Abnormal motor response (AMR) elicited with the blink reflex

9 TREATMENT FOR HMS Medication is usually ineffective Botox injections to facial nerve may provide temporary relief but is not curative Surgery is the preferred treatment

10 MICROVASCULAR DECOMPRESSION SURGERY (MVD) Suboccipital, retromastoid craniectomy for treatment of trigeminal neuralgia and hemifacial spasm Identifies vascular contact with cranial nerves V or VII Arteries are decompressed from the nerve Risks include hearing loss and cranial nerve damage Cure rate of over 90%

11 LATERAL DECUBITUS POSITION FOR MVD V VII V VII McLaughlin et al, J. Neurosurg. 90, 1999

12 PATIENT POSITIONED IN HEAD HOLDER

13 MICROVASCULAR DECOMPRESSION

14 GOALS OF IONM DURING MVD FOR HFS Provide evidence of adequate decompression of facial nerve - AMR (lateral spread) Reduce risk of postoperative hearing loss -BAEP Reduce risk of damage to cranial nerves VII, IX, X - free running/triggered EMG

15 MONITORING FOR DECOMPRESSION Abnormal Muscle/Motor Response (AMR) or lateral Spread - Peripheral stimulation of one branch of VII produces response from muscles innervated by that branch (M) response, but also from muscles innervated by a different branch (AMR or lateral spread - Stimulate temporal branch and AMR recorded from mentalis muscle or stimulate mandibular branch and record AMR from orbicularis oculi

16 BRANCHES OF THE FACIAL NERVE C A B D E

17 PERIPHERAL FACIAL NERVE STIMULATION + Stim zygoma Stimulation Parameters - Stimulate at zygoma or mandible - Subdermal needle electrodes 1 cm apart - Cathode toward ear msec pulse constant current ma at 2-4 Hz - Check stimulation location - No muscle relaxants + Stim mandible

18 ANESTHESIA CONSIDERATIONS Communicate with anesthesiologist before case begins Depolarizing muscle relaxant for intubation only Avoid nondepolarizing muscle relaxants Communicate with anesthesiologist during case

19 RECORDING SITES Orbicularis Occuli Orbicularis Oris Recording Parameters - Paired needle electrodes 1cm apart msec display time - Bandpass filter 20-3K Hz - Sensitivity uv/division - No muscle relaxants Mentalis

20 LATERAL SPREAD- PRESENT/RESOLVED occuli oris Lateral Spread mentalis 13:19:22 Post Incision 14:04:45 Post Decompression

21 LATERAL SPREAD- PRESENT/RESOLVED Lateral Spread 13:59:05 Post Incision 14:01:44 Post Decompression

22 LATERAL SPREAD- PRESENT/RESOLVED??? Lateral Spread 11:33:10 Preincision 12:28:27 Post Decompression

23 LATERAL SPREAD RETURNS TO RAPID STIMULATION 12:31:33 Rapid Stim. 12:40:44 Closing 13:18:15 Final data

24 DOES MONITORING AMR HELP??? Some patients have persistent AMR but good surgical outcome In some patients AMR is lost before decompression In some patients with clinical evidence of HFS, intraoperative AMR is absent In some patients AMR persists, but is reduced in amplitude Single institution case reports have small sample size

25 PROGNOSTIC VALUE OF AMR MONITORING, LARGE SINGLE INSTITUTION EXPERIENCE - Hyun et al, Neurosurgery Review, Prospective study of 1,174 case of MVD for HFS - AMR present in 85.5% - AMR disappeared- 94.9% complete relief at 1 yr, 5% continued symptoms - Persistent AMR- 67.6% complete relief at 1 yr, 32.3% continued symptoms

26 PROGNOSTIC VALUE OF AMR MONITORING, META- ANALYSIS - Sekula et al, Neurosurg Focus, Meta-analysis of 11 studies from 1985 to 2009, 855 patients - If AMR resolved failure rate was 9.5% - If AMR persisted failure rate was 39% - Chance of being cured is 4.2 times greater if AMR resolved

27 ADDITIONAL META-ANALYSIS DATA Eckardstein et al, J Neurolog Surg, 75, 2014 Added 4 additional studies to Sekula study for total of 1301 patients Positive predictive value of AMR resolution 89% Negative predictive value of AMR resolution 24%

28 MONITORING FOR COMPLICATIONS Hearing loss - occurred in % of MVC surgeries prior to ABR monitoring - reduced to % with ABR monitoring Injury to cranial nerves VII, IX, X - facial weakness (immediate or delayed) 66.8/ % - hoarseness or dysphagia (transient or permanent) %/ %

29 INTRAOPERATIVE ABR MONITORING

30 Preincision 11:29:06 Decompression Complete 12:51:00 Final Data 13:21:48

31 10:50:22 11:04:31 12:35:07

32 RISK TO HEARING DURING MVD Critical stages of surgery - retraction of cerebellum - manipulation of vessels - decompression Mechanisms of injury - stretching of nerve - direct trauma - vascular compromise - saline induced compression

33 WARNING SIGNALS Conventional wisdom - loss of waves - shift of V latency >1 msec., I and/or V amplitude reduced by >50% - changes in III latency and amplitude?? Revised for MVD, (Polo et al, Neurosurgery, 54, 2004) - shift of V latency 0.4 msec watching signal - shift of V latency >0.6 msec warning signal - no added value from changes in III (Thirumala et al, J Clin Neurophys, 31,2014)

34 ARTIFACTS Electrocautery, CUSA, Drilling - stop recording Line frequency artifact - notch filter - filter settings - stimulation rate Movement artifact - pause/ask surgeon to pause - use alternate recording site

35 CRANIAL NERVE MONITORING Free running EMG - subdermal needle electrodes placed in appropriate muscles - presence of neurotonic discharges Triggered EMG - monopolar or bipolar stimulation by surgeon - presence or absence of CMP/ threshold of CMP

36 NEUROTONIC DISCHARGE

37 TRIGGERED EMG Proximal Stimulation Distal Stimulation Holland, N, J Clin Neurophysiol, 19, , 2002

38 EMG MONITORING FOR LOWER CRANIAL NERVES E

39 WHAT S NEW?? Z-L Response (AN-AMR) - First reported in 2012 Acta Neurochir Stimulate wall of offending vessel with bipolar concentric electrode - Response recorded from same muscles as AMR - Z-L response usually same course as AMR but not always - Useful when AMR is absent before decompression or persists - AN-AMR more sensitivity for identifying the real offending vessel

40 Z-L RESPONSE (AN-AMR)

41 FACIAL NERVE MEPS TCMEPS - Multipulse transcranial stimulation activates the CST and produces CMAP from distal muscles - Routinely applied to monitor spine surgeries Corticobulbar MEPs - Same principle can be applied for stimulating the corticobulbar tract and recording from cranial nerves - Use different stimulation sites, short ISI and verify no response to single pulse - Facial nerve MEPs have been shown to be modified after MVD supporting central involvement

42 SINGLE PULSE VS TRAIN STIMULATION Fernandez-Conejero, I. et al, Clinical Neurophysiology, 123, 78-83, 2012

43 FACIAL NERVE MEPS DURING MVD/SINGLE PULSE Wilkinson, M. et al, J. Neurosurgery, 103, 64-69, 2005

44 FACIAL NERVE MEPS DURING MVD/ TRAIN STIMULUS Fuduka, M., et al, J. Neurol Neurosurg Psychiatry, 81, , 2010

45 FACIAL NERVE MEPS/ TRAIN AND SINGLE PULSE Fernandez-Conejero, I. et al, Clinical Neurophysiology, 123, 78-83, 2012

46 SUMMARY Intraoperative monitoring (lateral spread) is useful Intraoperative monitoring (ABR and EMG) reduces complications Intraoperative monitoring (MEPs and ANR-AMR) show promise

47 UNIVERSITY OF MISSISSIPPI MEDICAL CENTER