Does the ENoG Value of the Orbicularis Oris Muscle Does the ENoG Value of the Orbicularis Oris Muscle

Reflect Entire Facial Nerve Degeneration?Reflect Entire Facial Nerve Degeneration?ShinShin--Ichi Haginomori, MD, ShinIchi Haginomori, MD, Shin--Ichi Wada, MT, Takahiro Ichihara, MD, Atsuko Mori, MD Ichi Wada, MT, Takahiro Ichihara, MD, Atsuko Mori, MD

Atsuko Kanazawa, MD, Atsuko Kanazawa, MD, ReiRei Matsumura, MD, Ryo Kawata, MDMatsumura, MD, Ryo Kawata, MDDepartment of Otolaryngology Department of Otolaryngology -- Head and Neck Surgery, Osaka Medical College, Takatsuki, JapanHead and Neck Surgery, Osaka Medical College, Takatsuki, Japan

INTRODUCTIONINTRODUCTION

DISCUSSIONDISCUSSION

RESULTSRESULTS

ABSTRACT PATIENTSPATIENTS ANDAND METHODSMETHODS

CONCLUSIONSCONCLUSIONS ReferencesReferencesCONTACT

Objectives1.Compare ENoG values in patients with facial palsy using two different methods, the midline method that records compound muscle action potentials (CMAPs) from the orbicularis oris muscle - the standard muscle for facial ENoG - and five electroneurogram recordings that records five CMAPs from five different facial muscles. 2.Reveal whether the ENoG value obtained with the midline method reflects entire facial nerve degeneration.

MethodsForty patients with facial palsy were enrolled. CMAPs were recorded using the midline method, in which the anode was placed on the mental protuberance and the cathode was placed on the philtrum. Additionally, five electroneurogram recordings were obtained by placing the anode on the skin of the parietal region and five cathodes on the skin over five facial muscles (frontalis, orbicularis oculi, nasalis, orbicularis oris, and depressor anguli oris muscles). ENoG values recorded using the two methods were compared.

ResultsThe ENoG values of the five facial muscles did not differ from those obtained using the midline method. The total ENoG value calculated by summing five CMAPs from five facial muscles, which is considered to reflect total facial nerve degeneration, was not significantly different from that using midline methods; moreover, a strong positive correlation coefficient (r = 0.87) was found between them.

ConclusionThe midline ENoG method that records CMAP from the orbicularis oris muscle reflects entire facial nerve degeneration. The ENoG value calculated from the orbicularis oris muscle might be suitable to evaluate the total prognosis of facial palsy.

PATIENTS40 patients (21 males and 19 females; mean age, 48.6 years) with unilateral peripheral facial nerve paralysis.35 Bell’s palsy, 5 Ramsay-Hunt syndrome. All patients were treated using steroid and antiviral medicine.

We recommend the midline method as a superior ENoG technique for prognostic diagnosis in patients with facial nerve paralysis, because the ENoG value appears to reflect total facial nerve degeneration, setting of the electrodes is easy, and a more accurate prognosis can be obtained compared with the standard method.

Estimating the degree of facial nerve damage and evaluating the prognosis of facial nerve paralysis are most important to patients. Procedures that aid in prognostication include facial movement scoring scales, the nerve excitability test (NET), electroneurography (ENoG), electromyography, and stapedial reflex measurements. Among theseprocedures, ENoG is widely used.We proposed new electrode positions for measuring compound muscle

action potentials (CMAPs) from the facial muscles [1,2], in which the anode is placed on the mental protuberance and the cathode is placed on the philtrum over the orbicularis oris muscle, called the midline method. This method is simple in terms of electrode setting and is not influenced

by any resting asymmetry of the face in patients with unilateral facial nerve paralysis. However, whether ENoG using the midline method actually reflects the degree of damage in the entire facial nerve remainscontroversial.In the present study, we compared ENoG values in patients with facial

nerve paralysis using two different methods, the midline method and five electroneurogram recordings, to reveal whether the ENoG value obtained with the midline method reflects total facial nerve degeneration.

1. Haginomori S, Wada S, et.al. A new method for measuring compound muscle action potentials in facial palsy : a preliminary study. Muscle Nerve 2008;37:764–9.

2. Haginomori S, Wada S, et.al. A novel electroneurography method in facial palsy. Acta Otolaryngol 2010;130:520–4.

Shin-Ichi Haginomori, M.DDepartment of Otolaryngology - Head and Neck surgery, Osaka Medical Collegee-mail: hagi@poh.osaka-med.ac.jp

midline method

5 electroneurogram recordings

–, cathode+, anode

frontalis m.

orbicularis oculi m.

orbicularis oris m.

nasalis m.

depressor anguli oris m.

Figure 1. Midline method and 5 electroneurogram recordings

ENoG value correlation coefficient

（％, mean ± SE ）

Midline method 26.4 (± 3.6)

5 electroneurogram recordings

frontal muscle 25.3 (± 4.9) 0.48

orbicularis oculi muscle

29.8 (± 4.7) 0.75

nasalis muscle 35.7 (± 5.0) 0.77

orbicularis oris muscle

28.7 (± 4.2) 0.77

depressor anguli oris muscle

29.8 (± 3.7) 0.76

total from 5 muscles 29.1 (± 3.6) 0.87

Table 1 ENoG values obtained using the midline method and from 5 electroneurogram recordings for each facial muscle.

METHODS (Figure 1)We recorded CMAPs using the midline method and five

electroneurogram recordings separately from five facial muscles (frontalis, orbicularis oculi, nasalis, orbicularis oris, and depressor anguli oris muscles) simultaneously. ENoG values were calculated using CMAPs for the

midline method and five electroneurogram recordings in each patient. Total ENoG values were calculated by summing the five CMAP amplitudes recorded from 5 facial muscles using 5 electroneurogram recordings in each patient. ENoG values using these two methods were compared statistically.

ENoG values obtained using the midline method did not differ among the five studied facial muscles. Correlation coefficients for ENoG values between the midline method and five electroneurogram recordings ranged from 0.48 in the frontal muscle to 0.77 in the nasalis and orbicularis oris muscles. Moreover, ENoG values obtained using the midline method showed strong positive correlations with total ENoG values calculated for the five facial muscles. These results suggest that the ENoG value obtained using the midline method may reflect the degree of the entire facial nerve damage in patients with facial nerve paralysis, and may be considered representative facial nerve ENoG values.

1. ENoG values obtained using the midline method and from five electroneurogram recordings for each facial muscle (Table 1, Figure 2a-e)The mean ENoG value obtained using the midline method was 26.4 ± 3.6% (mean ± SE). The mean ENoG values obtained from five electroneurogram recordings ranged from 25.3 ± 4.9% in the frontal muscle to 35.7 ± 5.0% in the nasalis muscle. Statistical analysis revealed no difference between each of the six ENoG values obtained by the midline method and from five electroneurogram recordings. Figure 2a-e shows the relationships between the ENoG values obtained using the midline method and those from five electroneurogram recordings in each patient. The correlation coefficients ranged from 0.48 in the frontal muscle to 0.77 in the nasalis and orbicularis oris muscles.

Figure2 The relationships between the ENoG values obtained using the midline method and those from five electroneurogram recordings

Frontal muscle Orbicularis oculi muscle

Nasalis muscle Orbicularis oris muscle

Depressor anguli oris muscle Total ENoG value (f)2. ENoG values obtained using the midline method and total ENoG values from five electroneurogram recordings (Figure 2f)The total CMAP amplitudes from five facial muscles were 2.85 ± 0.39 mV on the paralytic side and 10.16 ± 0.61 mV on the healthy side. The total ENoG value was 29.1 ± 3.6%, which did not differ significantly from the value obtained using the midline method (26.4 ± 3.6%). Figure 2f shows the relationship between the ENoG value obtained using the midline method and the total ENoG value from five electroneurogram recordings in each patient. A strong positive correlation (r = 0.87) was observed.