Electrophysiological characteristics of lesions in facial palsies of different etiologies. A study using electrical and magnetic stimulation techniques

ELSEVIER

Electroencephalography and clinical Neurophysiology 97 (1995) 355-368

Electrophysiological characteristics of lesions in facial palsies of different etiologies. A study using electrical and magnetic stimulation techniques KM. Riisler ay*, M.R. Magi&-is b, F.X. Glocker ‘, A. Kohler b, G. Deuschl ‘, C.W. Hess a aDepartment of Neurology, University of Beme. Inselspital, CH-3010 Berne, Switzerland b Department of Neurology, University of Geneva, Geneva, Switzerland ’ Department of Neurology, Uniuersity of Freiburg. Freiburg, Germany

Accepted for publication: 29 May 1995

Abstract Using magnetic stimulation techniques in addition to conventional electrical stimulation, the entire facial motor pathway can be assessed electrophysiologically. To study the diagnostic yield of these examinations, 174 patients with facial palsies of a variety of etiologies were examined (85 Bell’s palsies, 24 Guillain-Barr6 syndrome (GBS), 19 Lyme borreliosis, 17 zoster oticus, 12 meningeal affections, 10 brain-stem disorders and 7 HIV-related facial palsies). The facial nerve was stimulated electrically at the stylomastoid fossa and magnetically within its canalicular portion. Additionally, the face-associated contralateral motor cortex was stimulated magnetically. Recordings were from the nasalis or mentalis muscle, or both, using surface electrodes. Bell’s palsy patients showed typically a unilateral local hypoexcitability of the facial nerve to canalicular stimulation. In GBS, bilateral latency prolongations were frequent, as expected for a myelinic disorder. In contrast, in zoster, predominant axonotmesis was unilateral, and in HIV infection sometimes bilateral. The method was very sensitive to detect subclinical dysfunctions in meningo-radiculitis and malignant meningeal diseases, either prior to the onset of palsy, or on the contralateral (clinically unaffected) side. It also distinguished reliably between central and peripheral facial motor pathway lesions. In our experience, these inexpensive and non-invasive electrophysiological techniques contribute substantially to the differential diagnosis of facial palsies. Keywords: AIDS; Bell’s palsy; Guillain-Bark

syndrome;

Herpes zoster; Lyme disease; Meningeosis

1. Introduction The clinical differential diagnosis of acute or progressive facial palsies is sometimes difficult, and paraclinical tests are required to elucidate their etiology. As yet, these investigations rely mainly on cerebrospinal fluid (CSF) analysis (to search for inflammatory signs, e.g., in Lyme borreliosis) and on neuroradiological investigations (to rule out processes in the posterior fossa or within the temporal bone). Neurophysiological examinations are usually performed to characterize the conduction disorder and for prognostic purposes (Zander Olsen, 1975; Mamoli, 1976;

* Corresponding author. Tel.: + 41 31 6323098; E-mail: [email protected].

Fax: + 41 31 6329679:

0924-980X/9.5/$09.50 0 1995 Elsevier Science Ireland Ltd. All rights reserved SSDI 0013-4694(95)00134-4

Esslen, 1977; Boongird and Vejjajiva, 1978; Thomander and St&erg, 1981). A limitation of the neurophysiological investigation in the diagnostic work-up of facial nerve disorders is the frequent location of facial nerve lesions within the skull, where the nerve is not accessible to conventional electrical stimulation. The introduction of magnetic stimulation techniques has changed this situation (Barker et al., 1985). With magnetic transcranial stimulation, the proximal intracranial part of the facial nerve and the contralateral hemisphere can be excited (Murray et al., 1987; Benecke et ‘al., 1988; Schriefer et al., 1988; Rasler et al., 1989). Hence, conduction measurements across the entire peripheral and central facial motor pathways can be performed (RSsler et al., 1989). Theoretically, these methods should allow further localization and characterization of intracra-

EEM 94679

K.M. Rtisler et al./

356

ElectroencephaloKraphy

and clinicul

nial facial nerve lesions. They might assist the clinician in narrowing the differential diagnosis of facial palsies and give new insights into the pathophysiology of dysfunctions of the facial motor pathways. To date, magnetic stimulation methods have been used to characterize the facial nerve lesions in Bell’s palsy (Meyer et al., 1989; Rimpilainen et al., 1992; Glocker et al., 1994), acoustic neuroma (Wolf et al., 1991; Rosier et al., 1994a), and hemifacial spasm (Gge et al., 1993). There are only anecdotal reports concerning facial palsies of other etiologies. It was the goal of the present investigation to characterize facial palsies of different etiologies using these methods.

2. Patients and methods 2.1. Subjects Since 1990, all patients admitted to our departments with facial palsies are examined using magnetic stimulation techniques, and introduced into a computerized facial palsy database. For this analysis, we selected 174 patients with one of the diagnoses given in Table 1 who had been examined within the first 3 weeks after the onset of their palsy. These disorders were chosen because they represent a possible differential diagnosis of the acute isolated facial palsy. Facial palsies due to acoustic neuroma are not reported since they have been described in detail previously (RSsler et al., 1994a). The severity of the palsy was graded clinically from 0 to 4 as follows: grade 0: no palsy; grade 1: mild palsy, no facial asymmetry at rest; grade 2: moderate palsy, eye closure possible but obvious facial asymmetry at rest; grade 3: severe palsy, incomplete eye closure, barely visible movement or tone, dysfiguring asymmetry; grade 4: total palsy without movement or muscle tone. At the time of the examination, all patients were symptomatic with facial palsies graded between 1 and 4. All patients were examined using both electrical stylomastoidal (Esslen, 1977) and magnetic transcranial stimulation

Neurophysiology

97 (IYYSI 355-368

of the facial nerve (Riisler et al., 1989). Follow-up examinations were done in most patients. The numerical values of these results are not reported here, but are discussed in comparison with the results of the first examination. Table 1 summarizes the anthropometric data. Parts of the results of the 85 patients with Bell’s palsy have been reported in a previous paper (Glocker et al., 1994); these patients are included for comparison. The diagnoses were based on the clinical work-up, which included CSF analysis in most patients, otological and neuroradiological examinations, and blood serologies (or extended immunological assays) for Borreliu burgdorferi. Additional electrophysiological examinations (needle myographies, blink reflex, neurographies on the extremities) also contributed to the diagnosis, but are not reported in detail here. Diagnoses were further supported by the evolution of the disease, with or without specific treatment such as plasmapheresis in Guillain-Barre syndrome or antibiotics in Lyme disease. 2.2. Electrophysiological

methods

All examinations complied with the standards of the local ethical committees. Electrical stimulation was usually performed using the stimulator output of the EMG apparatus. Rarely, a Digitimer D-180 stimulator was also used. Magnetic stimulation was performed with a previously described custom-made stimulator (Heckmann et al., 1989; RSsler et al., 1994a). or with a Magstim 200 (Magstim Company Ltd., Spring Gardens, Whitland, UK). Both stimulators used a stimulation coil of 90 mm mean diameter. Previous trials had shown that results obtained with these stimulators were identical. Records were made on standard EMG devices. The stimulation procedures used to assess facial motor pathways have been described in detail previously. All measurements were done on both sides. In short, compound muscle action potentials (CMAPS) were recorded with surface electrodes from the nasalis, mentalis, or both muscles (RGsler et al., 1989, 1994a; Glocker et al., 1994). Latencies were measured to the first negative deflection of the potential, and amplitudes were measured from the

Table 1 Patients data and etiology of the facial nerve disorders n

Bell’s palsy Idiopathic polyradiculitis Lyme disease Zoster oticus HIV Brain-stem disease Meningeal affection All patients GBS: Guillain-Barre

syndrome;

Gender (M:F)

Mean age (years) (range)

85

54:31

42

(12-19)

24 19 17 7 10 12

19:5 15:4 8:9 314

51 48 57 33 47 42

(17-85) (26-80) (19-74) (24-44) (17-69) (29-61)

174

114:60

614 9:3

HIV: human immunodeficiency

virus infection;

(20 GBS; 4 Miller-Fisher)

(6 nerve lesions, 1 nuclear lesion) (6 stroke, 3 MS, 1 tumor) (8 infectious, 4 malignant meningiosis)

45 (12-85) MS: multiple sclerosis.

KM. Rijsleret al./ Electroencephalographyand clinical Neurophysiology 97 (1995) 355-368

baseline to the negative peak. Electrical stimulation was performed at the stylomastoid fossa (Esslen, 1977). Transcranial magnetic stimulation of the intracranial segment of the facial nerve was done by positioning the coil parietooccipitally on the affected side of the skull, with a clockwise current orientation on the right side and vice versa (Rbsler et al., 1989). The stimulator output was then increased stepwise until a maximal response was obtained. If the increased stimulator output resulted in extracranial nerve stimulation, the coil was repositioned more occipitally (RGsler et al., 1989, 1994a; Glocker et al., 1994). With magnetic transcranial stimulation, the nerve is excited at its entrance into the fallopian canal (“canalicular stimulation”) (RGsler et al., 1989, 1994b; Schmid et al., 1991, 1992; Rimpil’iinen et al., 1993). The technique of magnetic hemispheric (cortical) stimulation with recording from facial muscles was introduced in our laboratories after the collection of patients for the present study had begun. Therefore, it was performed in only 110 of the 174 patients. The coil was held with its circumference 6-8 cm lateral from the vertex (the center of the coil is then 1.5-3.5 cm lateral from the vertex), on the side opposite to the recorded muscle. The current orientation was clockwise for stimulation of the right hemisphere and vice versa. Patients were asked to gently activate the target muscle to facilitate the stimulus response. Since cortically evoked motor potentials are variable, and a supramaximal stimulation strength cannot be defined (Hess et al., 1987a), the shortest latency and greatest amplitude of 6 stimulation trials were considered for the analysis. The 3 stimulation sites allowed delineation of 3 segments along the facial motor pathway: the distal segment, the transosseal segment and the cortico-proximal segment (Fig. 1). The segment considered included the site of stimulation, since local hypoexcitability to stimulation may occur (particularly with canalicular stimulation). 2.3. Normal values and statistical analysis Normal values for facial nerve conduction studies were obtained from 14 normal subjects and from 168 unaffected sides of patients with acoustic neuroma and with a unilateral Bell’s palsy, who had been examined long after clinical recovery. These data were extracted from the original data of RSsler and Glocker and coworkers (Rijsler et al., 1989, 1994a; Glocker et al., 1994). The most sensitive electrophysiological sign of a Bell’s palsy, namely a marked amplitude reduction to magnetic canalicular stimulation (Glocker et al., 1994), had never been observed on the unaffected sides. Thus, we assumed that these data represent normal facial nerves. Since we used 2 different recording sites, normal values were calculated separately for studies involving the nasalis muscle (n = 100 normal neurographies, mean age of subjects 43 years, range 2276), and the mentalis muscle (n = 68 normal neurographies, mean age of subjects 44 years, range 14-78).

357

nasalis and/or muscle

I

: : :

: : : : : . I

brain stem

I

I

L cortico-proximal

I

’ trans- : * osseai* distal J

Segments Fig. 1. Diagram of the stimulation as assessed in the present study.

sites along the facial motor pathways

For the analysis we considered 11 parameters: the amplitudes and latencies to stylomastoidal, canalicular and cortical stimulation; the conduction times between the stimulation sites, i.e., transosseal conduction time (TOCT; latency difference between canalicular and stylomastoidal stimulation) and cortico-proximal conduction time (CPCT; latency difference between cortical and canalicular stimulation); the amplitude ratios of canalicular to stylomastoidal and cortical to stylomastoidal stimulation; and, finally, the presence or absence of an amplitude reduction of more than 90% between the stylomastoidal and canalicular stimulation sites. This parameter was introduced to account for the frequent observation in Bell’s palsy of a local hypoexcitability of the facial nerve to magnetic stimulation, not always related to conduction block (Schriefer et al., 1988; Rimpillinen et al., 1992; Glocker et al., 1994). For parameters that were distributed normally (gaussian distribution), normal limits were calculated as mean k 2 standard deviations (S.D.). Most parameters did not follow a gaussian distribution, so that a correction was performed as proposed by Robinson et al. (1991). In short, using a standard microcomputer spreadsheet program, the skew (i.e., the deviation of the data from the gaussian distribution) was calculated for each of the parameters. All values were then transformed by the following calculations: square, cube, square root, cube root, log, and negative inverse. The transformation method that yielded the lowest skew for a given parameter was chosen, and the mean f 2

KM. Rijsler et al. / Electroencephalography and clinical Neurophysiology 97 (1995) 355-368

358

Table 2 Normal values calculated separately for motor conduction correction method according to Robinson et al. (1991)

studies using m. nasalis or m. mentalis as target muscle. Given are means, normal limits and --

Target muscle M. mentalis

M. nasalis Unaffected nerves (n = 100)

Normal limit

Amplitudes fmVj Fossa stylomastoidea Facial canal cortex can./sty1. Cortex/Styl.

2.1 1.9 1.0 0.93 0.48

0.780.780.260.750.08-

Latencies fmsec) Fossa stylomastoidea Facial canal cortex Transosseal (TOCT) Proximal (CPCT)

3.6 4.8 9.9 1.2 5.1

2.43- 5.13 3.85- 6.40 7.43-14.73 0.64- 1.92 2.59- 9.93

3.95 3.77 2.33 1.16 0.88

Correction method

Unaffected nerves (n = 68)

Normal limit

Correction method

x1/’

2.6 2.6

1.33-4.89 1.31-4.62 not done 0.82-1.16 not done

log x log x

3.05-5.35 3.69-6.30 not done 0.19-1.64 not done

- l/x log x

Xl/J x1/s

log x not necessary

0.99

x’/”

4.0 4.9

-l/x -l/x

x’/’

0.9

log x

S.D. was calculated from the corrected values. Mean + 2 S.D. was then retransformed to yield the appropriate normal limits. Patient data were compared to the normal population data. A side-to-side comparison was not possible due to the great number of bilateral dysfunctions. Fisher’s exact test was used in a 2 X 2 contingency table to test for differences of frequencies of a given finding between the disorders. These contingency tables contained 6) the num-

Amplitudes fmV) Fossa stylomastoidea Facial canal cortex can./sty1. Cortex/Styl. Latencies (msecl Fossa stylomastoidea Facial canal Cortex Transosseal (TOCT) Proximal (CPCT)

not necessary

ber of patients with a given disorder and a specific abnormal electrophysiological finding, (ii) the number of patients with the disorder but without the abnormal electrophysiological finding, (iii) the number of patients with all other diseases and abnormal electrophysiological finding, and, finally, (iv> the number of patients with all other diseases but without the specific abnormal electrophysiological finding. Additionally, the odds ratio for an association of a specific finding with one of the diagnoses was

Table 3 Clinical and electrophysiological findings in our patients. Clinical severity of palsy graded between 0 (no palsy) and 4 (facial plegia); for detailed description see text. Given are and latencies are given with absolute ranges in parentheses. Standard deviation is not given because of the skewed data Only those patients were considered in whom measurements to nasalis muscle were available (this explains the slightly Lyme disease and HIV compared to Table 1). no resp.: no response. These examinations were not considered for conduction times

Clinical grade of palsy

not necessary

means + 1 S.D. Mean amplitudes distribution for most parameters. different number of patients with calculation of mean latencies or

Bell’s palsy (n = 85)

Guillain-Barre (n = 24)

Lyme disease (n = 18)

Zoster oticus (n = 17)

2.62 k 0.80

1.78+0.85

2.32 f 0.58

2.93 f 0.96

1.2 0.2 0.1 0.11 0.07

3.8 5.0 11.2 1.5 6.3

(0.0 - 3.8) (0.0 - 2.3) (0.0 - 1.1) (O.OO 1.05) (O.Ot- 0.91)

(2.4 (3.6 (7.2 (0.4 (2.7

5.8) - 6.3) -15.7) - 3.8) - 9.5)

1.4 0.7 0.4 0.39 0.31 no resp. 3 of 85 61 of 85 32 of 44 61 of 85 320f 44

4.5 5.7 13.7 1.8 7.3

(0.1 (0.0 (0.0 (OOO(O.Ot-

(2.4 (3.6 (7.2 (0.4 (2.7

4.1) 3.4) 1.9) 0.94) 1.88)

- 6.5) - 9.1) -22.1) - 5.0) -14.2)

1.3 0.3 0.1 0.21 0.06

(0.1 (0.0 (0.0 (O.Ot(OOC-

0.6 0.2 0.1 0.23 0.17

2.4) 1.4) 0.5) 1.14) 0.50)

no resp. Oof24 9of24 10of 22

4.1 5.8 14.3

(2.6 - 5.1) (4.8 7.1) (12.1 -18.6)

9 of 24 10of 22

1.8 6.0

(0.9 - 4.6) (5.9 - 6.0)

no resp. 0 of 18 4.3 11 of 18 4.5 12of 15 10.2 11 of 18 12 of 15

1.0 2.6

(0.0 (0.0 (0.0 (O.OO (OOO-

(2.2 (3.1 (5.3 (0.3 (2.1

2.6) 0.8) 0.8) 1.00) 0.88)

- 6.2) - 6.4) -15.9) - 1.7) - 3.1)

no resp. 4 of 17 12of 17 8 of 11 12of 17 8 of 11

KM. RGsler et al. / Electroencephalography and clinical Neurophysiology 97 (1995) 355-368 distal

cortico-proximal

359

phenomenon also known for motor evoked potentials recorded from limb muscles (Hess et al., 1987a). 3.2. Patient studies

??one segment

abnormal

?? multiple

segment abnormal

Fig. 2. Localization of the disorders in our patients. Displayed is the percentage of patients with a given localization along the facial motor path. The sum may be greater than 100% because multiple segments were affected in a considerable number of patients. It may be smaller than 100% because not all examinations allowed localization of the disorder. Asterisks denote significances of Fisher’s exact test as in Table 4.

calculated from these contingency tables. Non-parametric tests were used to test differences between group means (Mann-Whitney U test and Kruskal-Wallis ANOVA).

3. Results 3.1. Normal values Normal values for the nasalis and mentalis muscle records (and the correction method to derive normal limits according to Robinson et al. (1991) are given in Table 2. Amplitudes from mentalis were somewhat greater than from nasalis, and the distal motor latencies to mentalis were longer than to the nasalis muscle, probably due to the slightly greater distance between stimulation and recording sites. The muscle responses to cortical stimulation were about half the size of those to stylomastoid stimulation, a

Brain-stem (n = 10)

HIV (n = 6) 3.17*

1.33

Table 3 gives mean clinical palsy grades, and mean amplitudes and latencies at the different stimulation sites on the clinically affected side of our patients. If both sides were affected, the more severely affected side was chosen for calculations. Differences between the diagnostic groups were statistically significant for the clinical grade of palsy, for amplitudes to canalicular stimulation, the amplitude ratios of canalicular stimulation vs. stylomastoid stimulation and cortex stimulation vs. stylomastoidal stimulation, and for distal motor latencies (Kruskal-Wallis ANOVA; Table 3). Differences between the disorders almost reached statistical significance for the amplitudes to stylomastoid stimulation (Table 3). Hence, these parameters were discriminative between the disorders. 3.3. Localization

In most patients the dysfunction could be localized electrophysiologically to 1 (or more) of the 3 segments of the facial motor pathway (Fig. 2). When compared to all other disorders, the cortico-proximal segment was signiticantly more frequently affected in patients with brain-stem disease. Conversely, in all other affections, the transosseal segment was most often involved. In this series of patients isolated involvement of the distal nerve segment was not observed. A co-involvement of this segment along with other segments was, however, significantly more frequent in GBS patients as compared to the other disorders (P < 0.05, Fisher’s exact test; Fig. 2). Due to complete axonotmesis, localization was not possible in 12 patients (4 of them with zoster oticus and 3 with HIV infections).

disease

Meningeal (n = 12)

1.78 f 0.67

0.8 0.2 0.0 0.14

(0.0 -2.6) (0.0 -1.1) (0.0 -0.0) (0.00-0.42)

3.9 5.3 _ 1.5 _

(3.7-3.8) (5.3-5.3) (1.5-1.5) _

1.5 1.4 0.2 0.90 0.23 no resp. 3of6 5of6 2 of 2 5of6 2of2

4.3 5.7 12.1 1.4 6.2

of nerve dysfunction

Kruskal-Wallis ANOVA

process

P < 0.0001

2.55 i- 1.04

(0.5 (0.3 (0.0 (0.58(O.OO-

(3.0 (4.6 (11.7 (0.9 (3.0

3.8) 3.5) 1.0) 1.20) 0.82)

- 5.5) - 6.8) -15.7) - 1.7) -10.1)

1.3 0.7 0.2 0.50 0.28 no hasp. Oof 10 Oof 10 6of 10 Oof 10 6of 10

3.6 5.4 11.8 1.7 6.8

(0.0 (0.0 (0.0 (O.oo(O.OO-

(3.0 (4.3 (9.6 (0.7 (5.1

3.1) 2.4) 0.8) 1.10) 1.00)

- 4.1) - 7.4) -15.0) - 3.6) - 7.9)

ns. P < 0.001 ns. P < 0.0001 P < 0.05 no resp. lof12 4of 12 3 of 8 4of 12 3 of 8

P < 0.01 n.s. n.s. n.s. n.s.

K.M. Riisler et al./

360

Electroencephalography

and clinical

97 (I 995) 355-36X

b) local canalicular nerve hypoexcitability

a) prolonged latency CBS

Bell

Meningeal

Lyme

Brainstem

Zoster

Lyme

HIV

Bell

CBS

Zoster HIV

Neurophysiology

Meningeal

1

:

0%

:

20%

40%

,

Brainstem /_**

60%

0%

I 20%

40%

60%

80%

% of patients

o/o of patients

Fig. 3. Frequency of electrophysiological results suggestive of myelin disorders of facial motor pathways. Shown is the frequency of latency prolongations (irrespective of their localization) and of a local hypoexcitability of the facial nerve to canalicular magnetic stimulation (defined by a ratio of amplitudes of canalicular to stylomastoidal stimulation below 0. I ). For detailed description of the parameters see text. Asterisks denote significance in Fisher’s exact test as in Table 4.

Seven

(2 Bell’s, 2 GBS, 1 zoster oticus, disorders) had normal neurographies.

patients

brain-stem

and 2

3.4. Types of nerce lesions The electrophysiological examination allowed an appreciation of the type of nerve lesion in many patients. Latency prolongations, indicative of a focal myelin disorder, were a typical finding in GBS patients (Table 3; Fig. 3a). Latency prolongations of the cortico-proximal segment were found in all of our patients with brain-stem demyelinating disorders, but not in those patients with vascular brain-stem disease. Bell’s palsy patients had significantly less often latency prolongations than patients affected by the other disorders (Fig. 3a). Conduction block, another electrophysiological finding of a focal myelin disorder, cannot be reliably measured by transcranial magnetic stimulation, as previously outlined (Glocker et al., 1994). A marked amplitude reduction to canalicular stimulation was significantly more frequent in Bell’s palsy than

HIV Zoster Meningeal Bell Brainstem CBS Lyme 0%

20%

40%

60%

80%

% of patients

??complete axonotmesis

0 Incomplete axonotmesis

Fig. 4. Frequency of electrophysiological results suggestive for an axonal lesion of the facial nerve. Asterisks denote significance in Fisher’s exact test as in Table 4.

in any other disorder (Fig. 3b1, and the mean amplitude ratio of canalicular vs. stylomastoidal stimulation was significantly lower in Bell’s palsy than in the other diseases (Table 3). Pronounced amplitude reductions to canalicular stimulation occurred in other affections as well, but they were generally not as marked as in Bell’s palsy. The average clinical grade of palsy did not differ significantly between patients with or without the amplitude reduction to canalicular stimulation in any of the disorders (Mann-Whitney U, P > 0.05). This supports the notion that the amplitude reduction was often not related to a local or more distal nerve conduction block. Nevertheless, in GBS patients this amplitude reduction was often related to a desynchronization of the motor potentials, as judged from the increased duration of the recorded CMAP (not reported in detail). It is especially noteworthy that in brain-stem disease these marked amplitude reductions to canalicular stimulation never occurred (Fig. 3b). To assess axonal nerve lesions, needle electromyographic studies are usually performed along with the neurographic methods. This was not done in all patients because examinations often took place within the first few days after onset of their palsy, when denervation signs are still lacking. Hence, we relied on the amplitude reductions from the distal stimulation site to evaluate the extent of axonal damage in our patients, being aware that this approach does not account for the possibility of distal conduction blocks between the stylomastoidal stimulation site and the muscle. Complete and partial axonal degeneration (i.e., lack of CMAP, or reduced amplitude below normal limits to stylomastoid stimulation, respectively1 was very often found in zoster oticus and HIV (Fig. 4). Mean amplitudes to stylomastoidal stimulation were smallest in these patients (Table 3). The course of the disease in zoster and HIV patients (late and incomplete recovery with synkinesis) subsequently confirmed that marked axonotmesis rather than neurapraxia had occurred.

Only transosseal segment affected Transosseal segment affected Local canalicular nerve hypoexcitability Clinical palsy grade > 3 Both sides affected (clin. or el.-phys.) Peripheral segment affected Prolonged conduction times Both sides affected (clin. or el.-phys.) Complete axonotmesis Axonotmesis Clinical palsy grade > 3 Complete axonotmesis Only cortico-proximal segment affected Cortico-proximal segment affected

findings

0.0 0.1 0.0 0.1

**

* ** ***

(0.0-0.6) *** (0.0-0.2) *** (0.0-0.5) *** (0.0-0.97) *

0.2 (0.1-0.5)

Clinical palsy grade > 3

Local canalicular nerve hypoexcitability Transosseal segment involved Only transosseal segment involved Clinical palsy grade > 3

0.2 (0.0-0.8) 0.2 (0. I-0.6) 0.1 (0.1-0.3)

Only cortico-proximal segment affected Prolonged latency Both sides affected (clinical or el.-phys.)

Odds ratio (95% conf. interval)

3.2 (1.7- 6.1)*** 5.1 (2.2-12.0) *** 4.4 (2.3- 8.4) *** 2.2(1.14.2)* 19.2 (5.4-68.1) *** 4.1 (1.1-15.2) * 8.4 (3.2-21.7) *** 2.9 (l.l7.6) * 5.7 (1.5-21.6)* 3.3 (1.2- 9.4) * 4.8 (1.3-17.7) * 13.2 (2.6-68.0) ** 13.5 (3.2-56.1) *** 5.2 (1.3-21.4) *

findings

Contradictive

Odds ratio (95% conf. interval)

* 0.05 > P > 0.005; ** 0.005 > P > 0.0005; *** P < 0.0005 (Fisher’s exact test).

HIV Brain-stem

Lyme disease Zoster oticus

Guillain-Barre

Bell’s palsy

Supportive

interpretation

with significant

odds ratio (i.e.,

Often highly axonal lesion Primary lesion localized to cortico-proximal segment. Clinically slight to moderate palsy

palsy

Typically bilateral dysmyelinic affection, may affect any nerve segment. Clinically slight to moderate palsy Often bilateral dysfunction Often highly axonal lesion. Clinically severe

Primary lesion localized to transosseal segment, locally increased threshold, typically unilateral. Clinically often severe palsy

Pathophysiological

Table 4 Distinctive clinical and electrophysiological findings in facial palsies of diverse etiologies. For the definition of parameters see text. The table contains only those parameters the 95% confidence interval does not enclose I). Meningeal diseases are not included because none of the parameters reached significance in these patients

K.M. RGsler et al./ Electroencephalography

362

3.5. Typical findings

and clinical Neurophysiology

orders were sometimes demonstrated prior to clinical involvement of facial muscles (see case reports 2 and 4 below). The importance of subclinical nerve involvement is exemplified in case report 1. Case report I (malignant meningeosis). In this 32-yearold male a highly malignant T cell non-Hodgkin lymphoma (state IVB) was diagnosed in May 1992. He had no neurological symptoms at that time. Cytostatic treatment

in the different disorders

Supportive and unsupportive neurophysiological findings for the disease entities are given in Table 4. This table presents the odds ratios for the association of some selected neurophysiological parameters with the facial nerve affections (the odds ratio is significant if the upper and lower limits of the 95% confidence interval do not enclose 1; a parameter is supportive of a diagnosis if its odds ratio is greater than 1 and contradictory of a diagnosis if its odds ratio is smaller than 1). For example, in Bell’s palsy the odds ratio was greater than 1 for an affection of the transosseal segment, and for the presence of a local hypoexcitability to canalicular stimulation. It was smaller than 1 (i.e., contradictive) for an affection of the corticoproximal segment or of the contralateral nerve (Table 4). The table summarizes also the main pathophysiological features disclosed by our results. 3.6. Electrophysiological findings and time course

results

in relation

led to a complete

r*

=0.17

of the lymphoma.

In March

At the same time, the patient complained of paresthesiae of the right hand and of both feet. Neurological examination showed a slight right sided peripheral facial weakness, a moderate weak ness of the proximal left arm, and signs of a symmetrical sensorimotor polyneuropathy. A malignant meningeal infiltration was suspected, but cranial MRI and CSF analysis were normal. The electrophysiological examination of the facial nerve was abnormal on both sides (Fig. 6a). On the right side, it showed a reduced CMAP amplitude (as compared to the left side) and a pathological prolongation of the TOCT (localizing a dysfunction to the transosseal segment). On the left, a barely reproducible potential with a prolonged CPCT could be evoked by cortical stimulation (localizing a dysfunction to the cortico-proximal segment, Fig. 6a). In view of the history, this result was interpreted as highly suggestive of a malignant meningeal infiltration, possibly with an underlying polyneuropathy. Since CSF and MRI were normal, no treatment was undertaken. Four months later, the patient was readmitted for intolerable headaches. The cranial CT scan showed an acute occlusive hydrocephalus and CSF examination revealed 1200 malignant cells. Cytostatic treatment and axial radiotherapy were started. In CBS and Miller-Fisher syndrome the results of the facial examination were compared to results of neurographies performed on the limbs. In these patients up to 8 limb nerves were investigated repeatedly, including F wave examinations, proximal, and sometimes cortical, stimulation. In all 4 Miller-Fisher patients and in an additional 4

to clinical

CBS

remission

1993, a right sided facial palsy occurred.

The grade of palsy differed significantly between the disorders, being highest in HIV and zoster and lowest in GBS (Table 3). In all disorders, there was a considerable variation of the CMAP amplitudes to stylomastoid stimulation in relation to the clinical grade of palsy (Fig. 5). The correlation coefficient between the clinical grade of palsy and CMAP amplitudes to stylomastoidal stimulation was greater in zoster with its high percentage of axonal lesions, and lower in the predominantly neurapraxic disorders observed in GBS and Lyme disease (Fig. 5). Clinically, 27 patients had bilateral facial palsies. In 26 additional patients, a subclinical contralateral nerve lesion could be demonstrated electrophysiologically (Fig. 6b). Clinical and/or electrophysiological bilateral involvement was most often found in GBS and Lyme disease, but rarely in Bell’s palsy patients (Fig. 6b). In meningo-radiculitis patients unilateral or bilateral subclinical facial nerve dis-

Bell

97 (19951355-368

r* =O.lS

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= 0.34

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clinical grade of palsy

3

4

0

12

0

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Fig. 5. Relationship between the amplitudes of the nasalis muscle response to stylomastoid stimulation and the clinical grades of palsy in patients with Bell’s palsy, Guillain-Barr6 syndrome (GBS; MFS: Miller-Fisher syndrome), Lyme disease, and zoster oticus. The correlation is best in zoster with its high incidence of axonal nerve lesions. Correlations did not reach statistical disorders in this study, because of the smaller numbers of patients.

significance

in GBS and Lyme disease. Relationships

are not shown for the other

K.M. Riisler et al./Electroencephalography

GBS patients out of 20, facial nerve examination yielded the only or earliest abnormal paraclinical result. It is noteworthy that in one of the Miller-Fisher patients clinically a mesencephalic stroke was initially suspected, and facial nerve examination provided the first clue to the true nature of the disorder. The time course of the parameters is not available for all patients. For Bell’s palsy, the time course of electrophysiological parameters has been reported in detail in a previous article (Glocker et al., 1994). Particularly in Lyme disease, the electrophysiological findings at a given time resembled those of Bell’s palsy, but the time course was quite different. Three case reports are included to exemplify the different time course patterns observed. Case report 2 (meningo-radiculitis of unknown etiology). This 48-year-old male was admitted for a 3 day history of paresthesiae in both feet and hands as well as cervical and lumbar pain radiating into arms and legs. He had no facial palsy at this time. The initial neurological examination revealed diminished ankle reflexes but was otherwise normal. CSF analysis disclosed an increased total protein content of 1.48 g/l and a lymphocytic pleocytosis of 933 cells/pi. Sensory and motor neurographies of the upper and lower extremities remained normal during several follow-up studies. Facial motor neurography was abnormal on the right side. There was no reproducible CMAP to magnetic cortex stimulation, suggesting subclinical involvement of the right sided facial nerve (Fig. 7). Two days later the patient developed a severe facial palsy on the right side with incomplete eye closure (grade 3). In the follow-up examination 7 days later, no muscle response was obtained to magnetic canalicular stimulation on the right side, suggesting distal spread of the inflammatory process. Blood and CSF serologies for Borrelia burgdorferi and tuberculosis, as well as for neurotropic viruses including herpes simplex, HIV, cytomegaly, Epstein-Barr and varicella, were negative; the angiotensin converting enzyme was normal. A polymerase chain reaction assay in the CSF for Borrelia burgdorferi was negative. The patient was treated with ceftriaxon for 2 weeks and with steroids. Three weeks later paresthesiae and radiating pain had disappeared and the facial weakness had improved (grade 2). Electrophysiologically a CMAP to magnetic cortex stimulation was now obtained, but the cortico-proximal conduction time was still markedly prolonged (Fig. 7). The CSF protein had normalized and the CSF cell count was 17 cells/pi. On hospital discharge the patient was free of symptoms. With respect to the clinical syndrome with distal tingling of the extremities, polyradicular pain, unilateral facial palsy and the CSF findings the diagnosis of an infectious polyradiculitis of unknown origin was made. This case demonstrates the subclinical involvement of the facial nerve before onset of the clinical facial palsy. Case report 3 (Lyme disease). This 68-year-old woman suffered a left sided facial palsy in August 1991. She

and clinical Neurophysiology 97 (1995) 355-368

363

a) right

left

a’

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c’

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CBS Lyme Meningeal Zoster Brainstem HIV Bell 0%

25%

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75%

100%

% of patients Fig. 6. a: records from the nasalis muscle in patient 1. The patient suffered from a malignant meningeal infiltration by a non-Hodgkin lymphoma. Clinically, he presented with a slight right sided facial palsy. Traces: a, stylomastoidal stimulation; b, canalicular stimulation; c, cortical stimulation. Latencies (arrows), right side: a, 3.8 msec; b, 7.4 msec (TOCT: 3.6 msec; normal limit < 1.92 msec); c, 15.0 msec (CPCT: 7.6 msec); left side: a’, 3.7 msec; b’, 4.8 msec (TOCT: 1.1 msec); c’, 18.8 msec (CPCT: 14.0 msec; normal limit < 9.93 msec). Note that the amplitude of trace c on the right side (cortex stimulation) is within normal limits and does not indicate a conduction block between sites c and b. The result suggests a bilateral dysfunction of the facial nerve, localized to the transosseal segment on the right, and to the cortico-proximal segment on the left side. b: percentage of patients with contralateral involvement in the different disorders. Asterisks denote significance in Fisher’s exact test as in Table 4.

KM. Riisler et al. / Electroencephalography and clinical Neurophysiology 97 Cl9951 355-368

364

2 days before clinical onset of palsy

7 days after onset: severe facial palsy (grade 3)

30 days after onset: moderate facial palsy (grade 2)

a

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Fig. 7. Facial motor conduction studies on the right side of surface electrodes, a: electrical stylomastoidal stimulation; whole course of the disease, a normal response is obtained days before occurrence of the facial palsy, no response is and stylomastoidal stimulation. Seven days after occurrence spread of the inflammatory process. At clinical recovery hypoexcitable to canalicular stimulation.

a patient with an infectious polyradiculitis (case report 2). Records from the nasalis muscle with b: magnetic transcranial canalicular stimulation; c: magnetic cortex stimulation. During the with electrical stylomastoid stimulation, suggesting a proximal, mostly neurapraxic, lesion. Two obtained to cortex stimulation, but CMAPs within normal limits are recorded from canalicular of the facial palsy the facial nerve is hypoexcitable to canalicular stimulation, suggesting distal 30 days after disease onset a CMAP to cortex stimulation is recorded, but the nerve remains

sought medical advise only 8 days later, when a contralatera1 right sided facial palsy occurred. A tick bite was not remembered by the patient. On examination, she had a severe facial palsy on the right side (grade 3) and a facial plegia on the left side (grade 4). Taste sensation was bilaterally severely impaired. The CSF revealed a cell count of 98 mononuclear cells. Serum antibodies to Borrelia burgdorferi were highly positive. The diagnosis of

day 1: severe palsy (grade 3)

Lyme disease was established, and an intravenous antibiotic therapy with ceftriaxon was begun. The CSF cell count decreased to normal within 2 weeks, and the facial palsies recovered within months. Electrophysiological examinations were carried out on days 1, 6 and 52 (from onset of the right sided palsy; Fig. 8). During this period, the paresis gradually recovered, but the amplitude to canalicular stimulation decreased progressively (Fig. 8).

day 6: severe palsy

day 52: s&igtf y;lsy

(grade 3)

ra e

a b

1

0.5 mV L

5 ms

Fig. 8. Time course of electrophysiological findings in a patient with Lyme disease. a: electrical stylomastoidal stimulation; b: magnetic transcranial canalicular stimulation. Results to cortex stimulation are not shown; there was no reproducible muscle response obtained. Clinically, the patient had a severe facial palsy which gradually improved. Electrophysiologically, the unchanged amplitudes to stylomastoidal stimulation prove the presence of a proximal neurapraxia causing the palsy. At the same time, the amplitude to canalicular stimulation decreases at days 6 and 5 1 of the disease, but this decrease is not related to the clinical degree of paresis (hence unrelated to the proximal conduction block and indicative of a local hypoexcitability).

KM. Riisler et al./ Electroencephalography and clinical Neurophysiology 97 (1995) 355-368

Case 3 shows that, in Lyme disease, the deterioration of electrophysiological parameters may sometimes follow rather than precede the clinical signs. Case report 4 (Lyme disease). This 44-year-old nurse presented with a left sided facial palsy in February 1993. She had been in good health until 3 days before, when she suffered violent pain in her left shoulder. She recalled an insect bite 3 weeks previously with a skin erythema consisting of multiple small red spots. On examination, there was a severe left peripheral facial palsy (grade 3), with impaired taste sensation, and a proximal weakness of the left arm (particularly the deltoid and the supra- and infraspinatus muscles). Electroneuromyography performed on the 6th day of the facial palsy showed normal responses of both mentalis and nasalis muscles to electrical stimulation, while magnetic canalicular stimulation evoked no responses on either side. Bilateral dysfunction of the facial nerves was considered likely, with a marked neurapraxia on the left and an asymptomatic hypoexcitability to canalicular stimulation on the right. Three days later she developed a facial palsy of the right side, while the weakness of the left arm had increased. A right scapula alata became apparent. The CSF protein was 0.66 g/l with 2 leukocytes/pi. CSF protein electrophoresis was normal. Serum and CSF antibodies against Borrelia burgdorferi were negative by immunofluorescence, but with the Western blot technique IgG were slightly positive. She was treated with ceftriaxon for 2 weeks. Two days after the beginning of the treatment the left facial palsy improved. Electrophysiological examination of the facial nerves, performed on the 1 lth day, remained unchanged (in spite of the nearly complete recovery of the left facial palsy), i.e., normal responses to electrical stimulation and absent responses to canalicular stimulation on both sides. The right facial palsy improved rapidly. Three weeks later she had almost completely recovered, and the CSF was normal. On the 30th day a response to magnetic canalicular stimulation was evoked on both sides (using higher than usual stimulation intensities) with a normal amplitude on the right, and a small amplitude as compared to mastoid electrical stimulation on the left. We concluded that, in spite of the only slight elevation of the antibodies against Borrelia burgdorferi, the clinical presentation, the CSF, and the excellent and rapid response to the treatment, strongly favored the diagnosis of Lyme disease. This case demonstrates that in Lyme disease a dysfunction is often bilateral, and that electrophysiological abnormalities may precede development of the clinical palsy.

4. Discussion The clinical and electrophysiological spectrum of facial palsies is broad, even within one disease entity. Since in cases of suspected infectious etiologies such as Borreliosis a lumbar puncture is needed, early diagnostic clues are

365

most desirable. The new magnetic stimulation techniques introduce a number of new diagnostic parameters to the investigation of facial palsies, which help narrow the clinical differential diagnosis, and which give new insights into the dynamics and pathophysiology of facial palsies. This technique is a useful addition to the traditional techniques, i.e., distal stylomastoidal stimulation, electromyography, which demonstrates denervation signs 1 or 2 weeks later (Ludin, 1980; Daube, 1991>, and blink reflex studies (Kimura, 1971; Esslen, 1977; Gilchrist, 1993), allowing an indirect assessment of intracranial lesions. Our data are well in line and extend previously known characteristics of facial nerve involvement in a variety of diseases. 4.1, Electrophysiological

characterization cial motor pathway disorders

of different fa-

Bell’s palsy is characterized by a marked reduction of the response amplitude to magnetic canalicular stimulation due to an enhanced stimulation threshold, as reported previously in detail (Glocker et al., 1994). This phenomenon can be observed within hours after the clinical onset of the disease, and persists sometimes for months after complete clinical recovery (Glocker et al., 1994). Various degrees of amplitude reduction to stylomastoid stimulation are also present, indicating the importance of axonotmesis. Clinical involvement of the contralateral nerve is rare (1 out of 85 patients), and electrophysiological contralateral nerve abnormalities are unusual (9 of 85 patients; Fig. 6b, Table 4). In this study, normals and Bell’s palsies served as reference groups to study the diagnostic yield of the method in other disorders. Lyme-related facial palsies often resembled Bell’s palsies with a combination of neurapraxia and axonotmesis, as reported by others (Sterman et al., 1982; Vallat et al., 1987; Krishnamurthy et al., 1993). The predominance of neurapraxia in Lyme disease is demonstrated by the lack of a relationship between the clinical grade of palsy and the size of the distally evoked muscle response (Fig. 5). In Lyme borreliosis, a local hypoexcitability to canalicular stimulation was found almost as often as in Bell’s palsy (Fig. 3b); nevertheless, facial palsies in Lyme borreliosis were often different electrophysiologically, particularly by their different time course. This is demonstrated in our case report 3, where this local hypoexcitability was found only after weeks, and in our case report 4, where it disappeared in parallel with the clinical palsy. In Bell’s palsy, on the other hand, it always occurred as early as within hours after the clinical onset of the palsy and persisted for months after clinical recovery (Glocker et al., 1994). Another frequent difference between the two entities was the greater number of bilateral facial affections in Lyme borreliosis (Fig. 6b; Table 4). In many of our patients a bilateral involvement was detected only electrophysiologically (Fig. 6b), as in our case report 4 where an absent response to magnetic canalicular stimu-

366

K.M. Riisler et al./ Electroencephalography

lation preceded the palsy by several days. It should be mentioned that in all of these cases the response to stylomastoid stimulation was normal. Thus, the differential diagnosis between tick-born and idiopathic facial palsy relies on the different electrophysiological time course, on the frequent detection by magnetic canalicular stimulation of (sometimes subclinical) bilateral dysfunctions, and on other systemic neurological i’indings and CSF abnormalities (Kuiper et al., 1992). CBS, as a demyelinating disorder, mainly showed latency prolongations (Fig. 3b, Table 4) (Kimura, 1971; Comblath, 1990), which were often diffuse to all 3 segments (Fig. 2), with a considerable number of abnormalities on the contralateral and clinically unaffected sides (Fig. 6b) (Hausmanowa-Petrusewicz et al., 1987). Also in GBS, amplitude reductions to magnetic canalicular stimulation were often found (Fig. 3b). It is possible that - as in Bell’s palsy - a local hypoexcitability of the nerve accounted for this finding in some GBS patients. However, in a number of patients this amplitude reduction was caused by the desynchronization of the motor potential, as judged by the increase in duration of the recorded CMAP. Thus, a desynchronization of conduction and even conduction block may be present in GBS (as commonly observed in limb peripheral nerves). Electrophysiologically, facial nerve conduction blocks are distinguishable only from the local hypoexcitability observed in Bell’s palsy, by comparison of the distally evoked potential with a reduced recruitment pattern during maximal voluntary activity (Roth et al., 1986), or by blink reflex studies, but not by magnetic stimulation (Glocker et al., 1994). As in Lyme disease, the lack of correlation between the clinical grade of palsy and the size of the distally evoked muscle response underlined the predominantly neurapraxic nature of the disorder (Fig. 5). A major finding of this study was the high sensitivity of the transcranial facial nerve examination technique to detect abnormalities in idiopathic polyradiculoneuritis. In all Miller-Fisher patients these techniques provided the first (or only) electrophysiological abnormality. In 4 out of the 20 additional GBS patients these techniques were more sensitive than limb neurographies, including F wave examinations and proximal stimulation techniques. Moreover, in 2 GBS patients the facial nerve was the only nerve out of 8 examined that showed electrophysiological abnormalities, although clinically there was no facial palsy detected (these 2 patients were not included in the present series of 24 GBS patients because they had no facial palsies). Finally, we observed that in GBS (as in Lyme disease) bilateral electrophysiological abnormalities often preceded a facial palsy by several days. Detection of abnormalities depended in these cases on the magnetic stimulation technique, since results to stylomastoidal stimulation were usually normal. The facial nerve may be especially sized to detect dysfunctions in GBS and other inflammatory radiculopathies, possibly due to its large contact zone with the CSF, since the new methods allow assessment of the nerve

ad

clinical Neurophysrology

97

C19%)355-368

course through the CSF. In patients presenting with symmetrical sensorimotor deficits of the limbs only, facial nerve examination may be a helpful clue to the electrophysiological diagnosis of GBS. Meningeal ufjrections of various other etiologies can also affect the facial nerve. Our patient group with meningeal affections was too small and heterogeneous to draw general conclusions. Again, the magnetic stimulation techniques were very sensitive for the early detection of facial nerve conduction disorders within the CSF, as demonstrated in our case reports 1 and 2. In case report 1 the facial neurography was the most sensitive sign of the meningeal malignant infiltration, since cranial MRI and CSF analysis were still normal at the time when electrophysiological abnormalities were detected (Fig. 6a). The meningeal infiltration was finally proven several months later by the evolution of the disease. In case report 2, with an infectious meningo-radiculitis of unknown etiology, follow-up examinations revealed the dynamics of the affection. In this case the meningeal infection first affected the cortico-proximal segment (by involving the nerve within its cistemal course) without clinical correlate. The facial paresis became clinically apparent only later when the electrophysiological results suggested a distal spread to the transosseal nerve segment (Fig. 7). Herpes zoster-related facial palsies often presented with a high degree of axonotmesis (Fig. 4, Table 4). Consequently, the clinical grade of palsy correlated significantly with the amplitude of the distally evoked muscle response (Fig. 5). Clinically, a rapid development of a severe to complete facial palsy was often encountered. The amplitude to canalicular stimulation was often reduced, yet often in the same range as to stylomastoidal stimulation. The electrophysiological findings are explained by the pathophysiology of this neurotropic viral infection, where virus invasion of the neuronal soma leads to cell death (re-viewed by Mumenthaler, 1985). HIV-related facial palsies may occur at any stage of the disease, including at seroconversion time (Uldry and Regli, 1988; Simpson, 1992; Ghika-Schmid et al., 1994). A facial palsy may thus herald the diagnosis of a HIV infection. III our small series of patients axonotmesis predominated (Fig. 4, Table 4). One patient presented with a subtotal axonotmesis that concerned both facial nerves and was thus readily distinguishable from a zoster-related palsy. On the other hand, in 3 seropositive patients the unilateral facial palsy was identical to (and may have been) a Bell’s palsy. In most of our patients with brain-srem lesions the electrophysiological measurements localized the lesion correctly within the cortico-proximal facial motor pathway segment (Fig. 2) (Riepe and Ludolph, 1993). Moreover, the patients with a brain-stem MS plaque had always a prolonged cortico-proximal conduction time, as expected in a central demyelinating disorder (Hess et al., 1987b). None of these patients showed hypoexcitability to canalic-

KM. Riisler et al./ Electroencephalography

ular stimulation. In these patients we did not differentiate between supra- and infranuclear lesions, because the magnetic stimulation techniques yield a cortico-proximal conduction time which includes both infra- and supranuclear paths. Measurement of blink reflex latencies along with the central conduction time may be helpful to differentiate between supra- and infranuclear lesions. 4.2. Usefulness of electrophysiological

examination

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unclear etiology since they add a substantial diagnostic yield. These methods become diagnostically useful immediately after disease onset, whereas prognosis relies on quantification of wallerian degeneration only 6 or more days later (Landau, 1953). The described techniques are non-invasive, quickly performed, and inexpensive. By narrowing the differential diagnosis of facial palsies, they are a valuable complement to the clinical examination.

in fa-

cial palsy

What is the impact of the described neurophysiological techniques in the differential diagnosis of facial palsies? First, in many affections an involvement of the transosseal nerve segment is found (Fig. 2), which is inaccessible to electrical stylomastoidal stimulation. Magnetic canalicular stimulation yields an extremely sensitive parameter for the function of this nerve segment, since very often a local hypoexcitability is found (Fig. 3b). An enhanced stimulation threshold was never found in healthy subjects. In patients it may precede the facial palsy (case 4) may be observed on the clinically unaffected side (case 4), and may follow the palsy long after clinical recovery (Glocker et al., 1994). Thus, it is of greater sensitivity for detection of a nerve dysfunction than the clinical examination. In addition to its sensitivity, this parameter is highly specific for a dysfunction localized to the canalicular portion of the transosseal segment. Since it is never found in patients with central lesions of the facial pathways, it is helpful when the question arises whether a facial palsy is of central origin or not, or whether a facial palsy is due to a partial facial nucleus lesion or a more peripheral lesion (a complete facial nucleus lesion cannot be distinguished from a complete axonotmesis more distally on the nerve). Second, to differentiate between the etiologies of facial palsies, the other electrophysiological parameters and their time course can be used. One has to bear in mind, however, that none of the single electrophysiological parameters is diagnostic per se, and combinations of electrophysiological parameters yield more specific information to narrow the differential diagnosis of facial palsies. If needed, additional electrophysiological methods can be applied. For example, blink reflex studies may be more sensitive to detect proximal conduction blocks, and quantification of such conduction blocks may be achieved by comparing the distally evoked potential to a reduced recruitment pattern during maximal voluntary activity (Roth et al., 1986). Supportive and unsupportive findings for the etiologies are analyzed in Table 4. It is noteworthy that these methods offer, for the first time, positive criteria for the diagnosis of a Bell’s palsy, since early nerve hypoexcitability to canalicular stimulation (i.e., 1 or 2 days after onset of the palsy) along with an electrophysiologically unaffected contralateral nerve is highly suggestive for this diagnosis. Using the described methods, neurophysiological means have more than a prognostic value in facial palsies of

References Barker, A.T., Jalinous, R. and Freeston, I.L. (1985) Non-invasive magnetic stimulation of the human motor cortex. Lancet, i: 1106-l 107. Benecke, R., Meyer, B.U., Schiinle, P. and Conrad, B. (1988) Transcranial magnetic stimulation of the human brain: responses in muscles supplied by cranial nerves. Exp. Brain Res., 71: 623-632. Boongird, P. and Vejjajiva, A. Electrophysiologic findings and prognosis in Bell’s palsy. Muscle Nerve, 1978, 1: 461-466. Comblath, D.R. (1990) Electrophysiology in Guillain-Barre syndrome. Ann. Neurol., 27 (Suppl.): S17-S20. Daube, J.R. ( 1991 J AAEM minimonograph no. 11: needle examination in clinical electromyography. Muscle Nerve, 14: 685-700. Esslen, E. (1977) The Acute Facial Palsies. Springer, Berlin. Ghika-Schmid, F., Kuntzer, T., Chavre, J.P., Miklossy, J. and Regli, F. (19941 Diversite de l’attainte neuromusculaire de 47 patients infect& par le virus de I’immunodtficience humain. Schweiz. Med. Wschr., 124: 791-800. Gilchrist, J.M. (1993) AAEM case report no. 26: seventh cranial neuropathy. Muscle Nerve, 16: 447-452. Glocker, F.X., Magistris, M.R., Riisler, K.M. and Hess, C.W. (1994) Magnetic transcranial and electrical stylomastoidal stimulation of the facial motor pathways in Bell’s palsy: time course and relevance of electrophysiological parameters. Electroenceph. clin. Neurophysiol., 93: 113-120. Hausmanowa-Petrusewicz, I., Ryniewicz, B., Rowinska-Marcibska, K., Emeryk, B. and KopeC, A. (1987) The subclinical facial nerve involvement in generalized neuropathies. Electromyogr. Clin. Neurophysiol., 27: 2299234. Heckmann, R., Hess, C.W., Hogg, H.P., Ludin, H.P. and Wiestner, T. (1989) Transkranielle Magnetstimulation des motorischen Kortex und perk&me Magnetstimulation peripher-nervijser Strukturen beim Hund. Schweiz. Arch. Tierheilk., 131: 341-350. Hess, C.W., Mills, K.R. and Murray, N.M.F. (1987a) Responses in small hand muscles from magnetic stimulation of the human brain. J. Physiol. (Lond.1, 388: 397-419. Hess, C.W., Mills, K.R., Murray, N.M.F. and Schriefer, T.N. (1987b) Magnetic brain stimulation: central motor conduction studies in multiple sclerosis. Ann. Neurol., 22: 744-752. Kimura, J. (197 1) An evaluation of the facial and trigeminal nerves in polyneuropathy: electrodiagnostic study in Charcot-Marie-Tooth disease, Guillain-Barre syndrome, and diabetic neuropathy. Neurology, 21: 745-752. Krishnamurthy, K.B., Liu, G.T. and Logigan, E.L. (1993) Acute Lyme neuropathy presenting with polyradicular pain, abdominal protrusion, and cranial neuropathy. Muscle Nerve, 16: 1261-1264. Kuiper, H., Devriese, P.P., De Jongh, B.M., Vos, K. and Dankert, J. (1992) Absence of Lyme borreliosis among patients with presumed Bell’s palsy. Arch Neurol., 49: 940-943. Landau, W.M. (1953) The duration of neuromuscular function after nerve section in man. J. Neurosurg., 10: 64-68. Ludin, H.-P. (1980) Electromyography in Practice. Thieme-Stratton, New York. Mamoli, B. (1976) Zur Prognosestellung peripherer Fazialisparesen unter

368

K.M. RBsler er al. / ElectroencephaloRraphy

besonderer Beriicksichtigung der Elektroneurographie. Wien. Klin. Wschr., Suppl. 53: 1-28. Meyer, B.U., Britton, T.C. and Benecke, R. (1989) Investigation of unilateral facial weakness: magnetic stimulation of the proximal facial nerve and of the face-associated motor cortex. J. Neurol., 236: 102-107. Mumenthaler, M. (1985) Zosterinfektionen des Nervensystems. Klinik und Therapie. Akt. Neurol., 12: 1455152. Murray, N.M.F., Hess, C.W., Mills, K.R., Schriefer, T.N. and Smith, S.J.M. (1987) Proximal facial nerve conduction using magnetic stimulation. Electroenceph. clin. Neurophysiol.. 66: S71. Gge, A.E., Yazici, J., Boyaciyan, A., Tanyeri, S.. Celik, M., Konyalioglu. R. and Baslo, A. (1993) Magnetic stimulation in hemifacial spasm and post-facial palsy synkinesis. Muscle Nerve, 16: 1154- 1160. Riepe, M. and Ludolph, A.C. (19931 Untersuchung kortikobulbarer Bahnen und peripherer Hirnnerven bei Normalpersonen und Patienten mit multipler Sklerose: Ergebnisse nach nichtinvasiver elektromagnetischer Reizung. Z. EEG-EMG, 24: 269-273. Rimpillainen, I., Karma, P., Laranne, J., Eskola, H. and Hakkinen, V. (1992) Magnetic facial nerve stimulation in Bell’s palsy. Acta Otolaryngol., 112: 311-316. Rimpillinen, I., Pyykko, I., Blomstedt, Cl., Kuurne, T. and Karma, P. (1993) The site of impulse generation in transcranial magnetic stimulation of the facial nerve. Acta Otolaryngol., 113: 339-344. Robinson, L.R., Temkin, N.R., Fujimoto, W.Y. and Stolov, W.C. (1991) Effect of statistical methodology on normal limits in nerve conduction studies. Muscle Nerve, 14: 1084-1090. Rosier, K.M., Hess, C.W. and Schmid, U.D. (1989) Investigation of facial motor pathways by electrical and magnetic stimulation: sites and mechanisms of excitation. J. Neurol. Neurosurg. Psychiat., 52: 1149-1156. Rosier, K.M., Jenni, W.K., Schmid, U.D. and Hess, C.W. (1994a) Electrophysiological characterization of pre- and postoperative facial nerve function in patients with acoustic neuroma using electrical and magnetic stimulation techniques. Muscle Nerve, 17: 183- 191.

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Neurophysiology

97 (19951355-368

Rosier, K.M., Schmid, U.D. and Moller, A.R. (1994b) Magnetic stimulation of the facial nerve: strong clinical and electrophysiological evidence places the excitation site to the labyrinthine segment of the nerve (Letter). Neurosurgery, 35: 1 I86- 1188. Roth, G.. Rohr, J., Magistris, M.R. and Ochsner. F. (1986) Motor neuropathy with proximal multifocal persistent conduction blocks. fasciculations and myokymia. Eur. Neural., 26: 416-423. Schmid, U.D.. Moller, A.R. and Schmid, J. (19911 Transcranial magnetic stimulation excites the labyrinthine segment of the facial nerve: an intraoperative study in man. Neurosci. Len., 124: 273-276. Schmid. U.D.. Moller. A.R. and Schmid, J. (1992) Transcranial magnetic stimulation of the facial nerve inbaoperative study on the effect of stimulus parameters on the excitation site in man. Muscle Nerve, 15. 8299836. Schriefer, T.N., Mills, K.R., Murray, N.M.F. and Hess, C.W. (1988) Evaluation of proximal facial nerve conduction by transcranial magnetic stimulation. J. Neurol. Neurosurg. Psychiat., 51: 60-66. Simpson. D.M. (1992) Neuromuscular complications of human immunodeficiency virus infection. Sem. Neural., 12: 34-42. Sterman. A.B., Nelson, S. and Barclay, P. (1982) Demyelinating neuropathy accompanying Lyme disease. Neurology, 32: 1302- 1305. Thomander, L. and S&berg, E. (1981) Electroneurography in the prognostication of Bell’s palsy. Acta Otolaryngol., 92: 221-237. Uldry, P.-A. and Regli, F. (1988) Paralysie faciale peripherique isolte et recidivante dans I’infection a human immunodeficiency virus (HIV). Schweiz. Med. Wschr., 118: 1029-1031. Vallat, J.M., Hugon, J., Lubeau, M., Leboutet, M.J., Dumas, M. and Desproges-Gotteron, R. (19871 Tick-bite meningoradiculoneuritis. clinical, electrophysiologic, and histologic findings in 10 cases. Neurology, 37: 749-753. Wolf, S.R., Goertzen. W. and Schneider, W. (1991) Transcranial magnetic stimulation of the facial nerve in patients with acoustic neurinoma. HNO, 39: 4822485. Zander Olsen, P. (1975) Prediction of recovery in Bell’s palsy. Acta Neural. Stand., 52 (Suppl. 61): 90.