Selected
References for the Hilger, Silverstein, and Brackmann II
Contents
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HILGER
ARTICLES
A Simple
Prognostic Test in Facial Palsy
E.D.R. Campbell, D.Phys.Med.
Journal of Laryngology 77: 462-66, June, 1963.
ABSTRACT: Nerve-excitability tests are easy to perform, need relatively
simple equipment and give 85-90 percent accuracy in the prognosis
of facial palsies. The results show how poor a recovery may be expected
when complete nerve degeneration occurs and some arguments are presented
in support of immediate decompression.
Global MST:
Predicting Prognosis for Bell's Palsy and Ramsay Hunt Syndrome Patients
Kedar K. Adour, MD
Paper presented at the American Academy of Otolaryngology, Head
and Neck Surgery, September, 1994. Send reprint requests to Kedar
K. Adour, MD, Dept. of Head and Neck Surgery, Kaiser Permanente
Medical Center, 280 W. MacArthur Blvd., Oakland, CA 94611-5693.
ABSTRACT: Global MST (Maximal Stimulation Test) using the Hilger
Facial Nerve Stimulator is an accurate, well-tolerated, easy-to-perform,
cost-effective method of predicting prognosis in patients with acute
facial palsy.
Hilger Facial
Nerve Stimulator: A 25-Year Update
Brent I. Lewis, MD; Kedar K. Adour, MD; Jonathan M. Kahn, MD; Alison
J. Lewis, MD
Laryngoscope 101:January, 1991, 71-74. Send reprint requests to
Kedar K. Adour, MD, Dept. of Head and Neck Surgery, Kaiser Permanente
Medical Center, 280 W. MacArthur Blvd., Oakland, CA 94611-5693.
ABSTRACT: Percutaneous nerve excitability testing using the Hilger
facial nerve stimulator was introduced about 25 years ago. The test
is reliable, easy to use, and inexpensive; it continues to be the
most frequently used method for predicting prognosis of facial nerve
disorders. Between 1966 and 1974, we recorded 10,243 nerve excitability
tests on 865 patients with a mean of 3.29 tests for each peripheral
branch and 3.43 for the trunk. Using a multiple regression model,
we determined the effect on nerve stimulation values of age, sex,
race, diabetes, hypertension, partial or complete clinical paralysis,
diagnosis of herpes zoster, year of testing, and eventual facial
paralysis recovery profile. We discuss statistical reliability,
provide a table of interpretive results, and offer "tips and
traps" invaluable to the practitioner. A prospective study
of 25 patients with residual facial paralysis was evaluated by two
separate otolaryngologists to determine intertester reliability.
Maximum Stimulation
Test (MST)
M. May
Excerpted from The Facial Nerve, New York: Thieme Medical Publishers,
1986.
ABSTRACT: The maximum stimulation test is an excellent way of evaluating
facial nerve degeneration soon after onset. The test can be performed
with any stimulator for which the strength and duration of the stimulus
can be varied. The test involves observing the muscle's response
to an electrical stimulus. Therefore, the patient must be cooperative
so that he does not flinch or pull away. The author suggests reassuring
the patient, in some cases sedation, and decreasing the skin resistance
to help diminish discomfort. First, the skin is prepared. After
the probe is applied to the skin, the current is slowly increased
from 1.0 milliamperes (mA) to 5.0 mA. The major branches of the
motor portion of the extracranial facial nerve are sampled: 1) forehead
and eyebrow, 2) preorbital area, 3) cheek, upper lip, and nasal
ala, 4) lower lip, 5) cervical and platysma area. In addition, the
area of the stylomastoid foramen is tested, which samples the entire
nerve rather than each branch. When interpreting the results, the
amount of muscle twitch in response to a stimulation on the affected
side is compared to that of the normal side. The observations are
useful in predicting the outcome in patients with traumatic facial
paralysis.
The Maximal
Stimulation and Facial Nerve Conduction Latency Tests: Predicting
the Outcome of Bell's Palsy
John M. Ruboyianes, MD; Kedar K. Adour, MD; David W. Santos, MD;
Peter G. Von Doersten, MD
Laryngoscope 104: January, 1994, 1-6. Send reprint requests to John
M. Ruboyianes, MD, North Campbell ENT, 3982 North Campbell, Tucson,
AZ 85719.
ABSTRACT: To test the hypothesis that the facial nerve conduction
latency test is a better and earlier indicator of prognosis than
other electrodiagnostic tests, 86 patients with Bell's palsy were
followed for a minimum of 4 months. To select control subjects for
our own research clinic and for comparison with the patient population,
latency values in 25 normal volunteers (50 sides) were determined.
Serial maximal stimulation tests (MST) and latency tests were conducted
to determine disease severity and prognosis in Bell's palsy patients.
Outcome was graded using the Facial Paralysis Recovery Profile (FPRP)
and Facial Paralysis Recovery Index (FRPI) as well as the House
grading system. The capability of the two tests to accurately predict
outcome was evaluated. The MST accurately predicted outcome in 94
percent of patients studied. In the control group, normal latency
values were a mean 3.8 msec with a standard deviation of 0.49. In
the patient population, latency values were either within normal
limits or absent. When done within 4 days of the onset of Bell's
palsy, neither test was capable of predicting axonal degeneration.
Statistical analyses included Fisher's Exact Test, the paired Student's
t test, and correlation coefficient calculations.
Nerve Excitability
Testing: Technical Pitfalls and Threshold Norms Using Absolute Values
George A. Gates, MD
Laryngoscope 103: April, 1993, 379-85. Send reprint requests to
George A. Gates, MD, 517 S. Euclid, Box 8115, St. Louis, MO 63110.
ABSTRACT: Percutaneous stimulation of the facial nerve is used widely
in tests to judge the severity and prognosis of facial paralysis.
Several test paradigms are used, including nerve excitability threshold
(NET), the maximum stimulation test (MST), and electroneurography
(EnoG). Consistent technique and careful control of variables are
essential to achieve accurate test results. The sources of variability
examined in this study were age, gender, body weight, and the use
of electrode paste; the NET was used as the test method. The facial
NET in 120 adults without a history of facial paralysis increased
linearly with age (P = .0004) and with body weight (P<.0001)
and was higher in men than in women adjusted for age and weight
(P = .0001). The mean NET ± SD was 0.7 ± 0.27 mA in the upper division
using the eyelid twitch as an end point, and 1.2 ± 0.40 mA in the
lower division. There was no statistically significant difference
in the results between sides. The NET was falsely elevated by the
use of electrode paste, presumably due to current shunting away
from the nerve.
Based on the technique described herein, an absolute
NET of > 1.25 mA in the upper division or an absolute Net >
2.0 mA in the lower division of the human facial nerve is statistically
abnormal. These norms are not applicable to grossly obese patients
or patients with facial edema or inflammation. Statistical norms
allow the NET results to be reported on a continuous scale rather
than the dichotomous scale used in the past. The predictive power
of the NET will be greatly enhanced by basing test interpretation
on both statistical and clinical significance.
Who's Afraid
of the Facial Nerve
Kedar K. Adour, MD
Excerpted from Otology (Chapter 21), S.E. Lucente, ed. St. Louis:
Mosby, 1995. Send reprint requests to Kedar K. Adour, MD, Dept.
of Head and Neck Surgery, Kaiser Permanente Medical Center, 280
W. MacArthur Blvd., Oakland, CA 94611-5693.
ABSTRACT: Facial paralysis is frightening to the patient and to
the physician. This fear often leads to unnecessary, expensive tests
and, at times, to inappropriate treatment. A systematic guide for
evaluating patients with facial paralysis is offered which includes
completion of a medical history and physical examination and selection
of laboratory, x-ray, magnetic resonance imaging (MRI), and prognostic
electrical testing. Nuances of differential diagnosis and use and
interpretation of electroneurography and maximal stimulation testing
(MST) are discussed. A newly revised method of recording and predicting
prognosis using the Hilger H3 Nerve Stimulator and MST is given.
Guidelines for frequency of follow-up visits, need for consultation,
and treatment are offered. The objective of this text is to instill
confidence in the treating physician, which in turn will reassure
the patient and reduce the cost of evaluation without sacrificing
sound medical judgment. Medico-legal implications will be considered,
and case studies will illustrate the course.
Value of
Nerve-Excitability Measurements in Prognosis of Facial Palsy
E.D.R. Campbell, D.Phys.Med.; R.P. Hickey, D.Phys.Med.; K.H. Nixon,
D.Phys.Med.; A.T. Richardson, D.Phys.Med.
British Medical Journal 2: July 7, 1962, 7-10.
ABSTRACT: A simple test of motor-nerve excitability is described.
This test distinguishes between physiological block and degeneration
of the facial nerve as early as 72 hours after the onset of facial
palsy. The results of this test and their relation to the time and
degree of recovery in facial nerve palsies of various types are
described. It is suggested that such a test should be used in the
assessment of treatments of facial palsy.
SILVERSTEIN
ARTICLES
Adaptor
for Continuous Stimulation (SACS) with the WR-S8 Monitor/Stimulator
Herbert Silverstein, MD
Paper presented at the American Academy of Otolaryngology, September,
1989. Send reprint requests to Herbert Silverstein, MD, Ear Research
Foundation, 1921 Floyd St., Sarasota, FL 34239.
ABSTRACT: Routine intraoperative monitoring of facial nerve function
has been used since 1985. An adaptor has been developed for continuous
stimulation (SACS) to be used with the new WR-S8 Monitor/Stimulator.
The SACS allows the microsurgical instruments and air drills to
be electrified and to function as probe-tips during surgical dissection.
The new WR-S8 Monitor/Stimulator has an ultra-sensitive strain-gauge
which detects facial movement before it is palpable. The remote
probe allows an assistant to adjust the current easily. The routine
use of facial nerve monitoring with SACS has decreased surgical
time, has helped prevent iatrogenic injuries, and has improved our
ability to save the facial nerve during otological and neurotological
surgery.
Facial Nerve
Monitoring Among Graduates of the Ear Research Foundation
Michael J. Olds, P. Todd Rowan, Jon E. Isaacson, and Herbert Silverstein
The American Journal of Otology 18: 1997, 507-511. Send reprint
requests to Herbert Silverstein, MD, Ear Research Foundation, 1921
Floyd St., Sarasota, FL 34239.
ABSTRACT: Routine facial nerve monitoring is not considered the
standard of care in most communities; however risk of facial nerve
injury appears to be greatly reduced when this adjunctive technique
is emplyed.
Innovative
Techniques: Facial Nerve Monitoring and Stimulation During Surgery
for Chronic Ear Disease
Eric E. Smouha, MD
Operative Techniques in Otolaryngology-Head and Neck Surgery 3/1:
March, 1992, 43-37. Send reprint requests to Eric E. Smouha, MD,
Asst. Prof. of Surgery, Health Sciences Center T19, State University
of New York at Stony Brook, Stony Brook, NY 11794-8191.
ABSTRACT: Preservation of facial nerve function is a major concern
during surgery for chronic ear disease. Facial nerve monitors have
already gained broad acceptance in neurotologic and skull base surgery.
There has been a growing consensus, even among the most experienced
otologists, that facial nerve monitoring has value in middle ear
and mastoid surgery as well. It is likely that use of intraoperative
facial nerve monitoring will become more widespread in the future.
A competent otologist must have a thorough knowledge
of the anatomic relations of the facial nerve and must be technically
skilled at dissecting around the nerve. Facial nerve monitoring
cannot replace basic anatomic knowledge nor can it replace surgical
skill. It may, nonetheless, benefit the surgeon in certain instances.
The surgeon can use facial nerve monitoring and stimulation as
an aid to accomplish the following:
Estimate the location
of the facial nerve within bone, diseased soft tissue, or altered
anatomy.
Provide continuous feedback
when dissecting tissue from an exposed facial nerve.
Predict the presence
or absence of bony covering when a portion of the nerve is concealed
by soft tissue.
Specify the site and
magnitude of conduction block in cases of facial nerve paralysis.
Provide warning of imminent
injury to the nerve.
Predict functional integrity
at the end of surgery.
During supervision of resident cases, a monitoring
device may provide a margin of security to the attending surgeon
whose hands are not directly in the operative field. When used by
experienced surgeons, facial nerve monitoring and stimulation may
offer intangible advantages that allow surgery to proceed more rapidly
and with a greater sense of confidence.
Intraoperative
Monitoring, Part A: Facial Nerve
Herbert Silverstein, MD, and Seth Rosenberg, MD, eds.
Excerpted from Surgical Techniques of the Temporal Bone and Skull
Base, Chapter 3, Philadelphia: Lea and Febiger, 1992.
ABSTRACT: Intraoperative facial nerve monitoring has been shown
to reduce the probability of iatrogenic injury to the facial nerve
during surgery, to save surgical time, and to reduce both patient
and surgeon anxiety. However, it does not replace good surgical
judgment or thorough knowledge of facial nerve anatomy. The author
lists five goals of intraoperative facial nerve monitoring: 1) early
identification of the facial nerve through stimulation, 2) alerting
the surgeon of facial stimulation, 3) mapping the course of the
facial nerve, 4) reducing trauma to the facial nerve, and 5) evaluation
and prognosis of facial nerve function.
The types of monitors include muscle movement
detection devices, such as the Silverstein Model S8, which uses
a solid-state cheek sensor. Mechanical muscle contractions cause
the pressure in the sensor to change, which sounds an alarm. False
muscle movement artifacts are electrically filtered. A supplement
to the monitor, the Silverstein Adaptor for Continuous Stimulation
(SACS), allows the surgeon to electrify microinstruments or air
drills. The use of electrified microinstruments and drills allows
rapid identification of the facial nerve and helps the surgeon find
the facial nerve obscured by disease or tumor. A second type of
monitor detects electrical activity in muscles. Electromyographic
recording devices use electrodes placed in facial muscles to detect
nerve activity due to physiologic activity, manipulation, trauma,
or electrical stimulation. The activity is presented to the surgeon
in both audio and visual forms.
Both mechanical pressure and EMG monitoring of
the facial muscles give the surgeon valuable information about
the status of the facial nerve. Each system has advantages and disadvantages,
and may be used simultaneously to provide safe monitoring of the
facial nerve.
Medical-Legal
Aspects of Temporal Bone Surgery
Herbert Silverstein, MD, and Seth Rosenberg, MD, eds.
Excerpted from Surgical Techniques of the Temporal Bone and Skull
Base, Chapter 1, Philadelphia: Lea and Febiger, 1992.
ABSTRACT: Over the last two decades, knowledge of the medical-legal
aspects of medicine has become as important as knowledge of the
disease processes and surgical techniques. Fortunately, in recent
years the number of malpractice suits against temporal bone surgeons
has decreased. This has been due in part to advances in surgical
techniques, such as intraoperative monitoring, and in part to greater
awareness and understanding by otologists of the medical-legal
issues
of medicine. A "bad result" is sometimes inevitable;
however, through meticulous risk management, some malpractice suits
can be
avoided.
Operating
Room and Patient Setup
Herbert Silverstein, MD, and Seth Rosenberg, MD, eds.
Excerpted from Surgical Techniques of the Temporal Bone and Skull
Base, Chapter 2, Philadelphia: Lea and Febiger, 1992.
ABSTRACT: One of the most important things for the neuro-otologic
surgeon to achieve is a well-equipped operating room with specialized
personnel dedicated to otology and neuro-otology. A personal scrub
assistant who takes care of the instruments and assists with surgery
will make surgical procedures proceed smoothly and efficiently and
reduce surgical time. The setup for otologic and neuro-otologic
cases is both time consuming and detailed. It is best to have one's
own surgical equipment that is not used by other surgeons, so that
missing or broken equipment is not discovered during surgery. Once
the personnel are trained and the equipment is obtained, one must
establish a routine that is followed for each case.
Routine Identification
of the Facial Nerve Using Electrical Stimulation During Otological
and Neurotological Surgery
Herbert Silverstein, MD; Eric Smouha, MD; and Raleigh Jones, MD
Laryngoscope 98/7: July, 1988, 726-30. Send reprint requests to
Herbert Silverstein, MD, Ear Research Foundation, 1921 Floyd St.,
Sarasota, FL 34239.
ABSTRACT: We routinely identify the facial nerve to avoid facial
nerve injury during most otologic surgery. Since 1985, we have used
a facial nerve stimulator/monitor as an added safety feature in
383 consecutive otologic and neurotologic cases. In our last 30
middle-ear, 8 retrolabyrinthine vestibular neurectomy, and 14 acoustic
neuroma cases we used the monopolar stimulator probe-tip to determine
threshold currents needed to produce facial twitch. Stimulation
thresholds varied according to the amount of soft tissue or bone
overlying the facial nerve. The stimulator was useful for predicting
dehiscences in the bony facial canal during middle-ear and mastoid
surgery. The exposed facial nerve usually stimulated at a level
less than 0.1 mA (mean 0.05 mA), and the horizontal facial nerve
covered by bone stimulated at 0.25 mA or greater (mean 0.6 mA).
The stimulator was also used to predict the amount of bone overlying
the vertical facial nerve at the annulus. An approximate relationship
of 1.0 mA of threshold current to 1.0 mm of bony covering was found.
After acoustic neuroma surgery, the stimulation threshold of the
facial nerve at the brain stem helped predict postoperative facial
function. Cases with current thresholds of 0.3 mA or less resulted
in normal facial function. During ear surgery, routine identification
of the facial nerve with the aid of a facial nerve stimulator will
help avoid facial nerve injury.
Routine Intraoperative
Facial Nerve Monitoring During Otologic Surgery
Herbert Silverstein, MD; Eric E. Smouha, MD; and Raleigh Jones,
MD
The American Journal of Otology 9/4: July, 1988, 269-75. Send reprint
requests to Herbert Silverstein, MD, Ear Research Foundation, 1921
Floyd St., Sarasota, FL 34239.
ABSTRACT: We have used intraoperative monitoring and stimulation
of facial nerve function routinely in 301 consecutive otologic and
neurotologic cases. The device has been safe, simple to use, and
practical. Facial contraction is detected by a strain-gauge sensor
in the corner of the mouth and is signaled audibly to the surgeon.
Electrical stimulation of the facial nerve can be delivered through
a sterile probe, which produces a constant-current-square-wave impulse.
The device has several advantages: it signals unintentional mechanical
stimulation of the facial nerve during surgery; it allows mapping
of the nerve through soft tissue, tumor, and bone; it predicts dehiscences
in the bony covering of the nerve; and it allows confirmation of
the electrical integrity of the nerve before and after surgery.
In this paper we present a technical description of the device,
relevant intraoperative electrical measurements, and illustrative
case examples. Although the device does not replace anatomic knowledge
and surgical ability, it provides a margin of security during ear
surgery. This system for intraoperative facial monitoring is practical,
and the authors encourage its routine use.
BRACKMANN
II ARTICLES
Improved
Preservation of Facial Nerve Function in the Infratemporal Approach
to the Skull Base
John P. Leonetti, MD; Derald E. Brackmann, MD; and Richard L. Prass,
MD, PhD
Otolaryngology-Head and Neck Surgery 101/1: July, 1989, 74-78. Send
reprint requests to John P. Leonetti, MD, Division of Otology, Neurotology,
and Skull Base Surgery, Dept. of Otolaryngology, Loyola University
Medical Center, 2160 First Ave., Maywood, IL 60153.
ABSTRACT: Although the infratemporal approach described by Fisch
provides excellent exposure of the jugular foramen, intrapetrous
carotid artery, and lateral skull base, the anterior displacement
of the seventh cranial nerve often results in temporary facial paralysis.
The use of a modified technique for facial nerve mobilization resulted
in significant improvement of both early and final facial function.
Since that earlier report, continuous intraoperative electrical
facial nerve monitoring has been used during the infratemporal approach
in 20 additional cases. Immediate postoperative facial function
was normal in 93 percent of the monitored cases and in 70 percent
of the cases in the unmonitored group. More important, no patients
in the monitored group developed grade V or VI weakness after surgery,
whereas 48 percent of the unmonitored patients had grade V or VI
weakness during the early postoperative period. This article will
describe how intraoperative facial nerve monitoring is used during
infratemporal surgery and will compare early facial function in
31 unmonitored patients with early facial function in 20 monitored
procedures.
Practical
Aspects of EMG Facial Nerve Monitoring: Insights and Pitfalls
Allen J. Senne, MA
Paper presented at the Annual Convention of the American Academy
of Otolaryngology-Head and Neck Surgery Foundation, September, 1992.
ABSTRACT: Continuous intraoperative EMG facial nerve monitoring
(EMGFNM) has become a well established practice that assists the
surgeon in preserving the functional integrity of the facial nerve.
It has been successfully employed during neurologic, as well as
selective otologic procedures. The proper use of EMGFNM has resulted
in a significant reduction in both the incidence and degree of post-operative
facial nerve weakness.
During the past several years, the practice of
EMGFNM has evolved from the rudimentary auditory amplification of
the alterations of electrical potentials recorded at musculature
innervated by the facial nerve, to a refined combination of oscilloscopic
and acoustic representations of EMG activity. These dramatic improvements
in instrumentation, and the concurrent evolution of a fairly standard
monitoring protocol, have generated a demand for a more concise
interpretation of these alterations of intraoperative EMG activity
levels. These fluctuations in EMG activity levels have been grossly
referred to in the literature as "bursts" or "trains"
of activity, although the relative significance of either type of
activity is still a matter of speculation. In addition, several
authors' studies have also proposed a correlation between the degree
and type of activity seen during surgery and the post-operative
facial result. It appears, then, that given the lack of standard
interpretive criteria available, there is a wide chasm between the
stimulus that appears and is heard on the monitor during a procedure,
and understanding the true significance of that stimulation. The
result of this dilemma is an uncertain response from the surgical
team to what is perceived on the monitor. Since significant surgical
decisions often depend on the interpretation of the monitored signal,
a clear understanding of the factors that can adversely affect the
reliability of the EMG signal is essential. This paper addresses
three problems commonly encountered while monitoring the facial
nerve during surgery, and then offers some practical suggestions
for the interpretation of the EMG response.
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