Traumatic Bilateral Facial Nerve Palsy: A 10-Year Retrospective Study
Article information
Abstract
Background and Objectives
Simultaneous bilateral facial nerve palsy (FNP) is rare. Traumatic and nontraumatic causes have been demonstrated. This study was performed to determine the prevalence and outcomes of bilateral traumatic FNP.
Subjects and Methods
We retrospectively reviewed temporal bone fracture (TBF) cases from 2010 to 2019. Number of patients and each patient’s characteristics were obtained using the hospital coding system.
Results
A total of 336 TBF cases were identified, among which 316 (94%) were unilateral and 20 (6%) were bilateral. Among these 20 cases, five (25%) developed bilateral FNP, all resulting from bilateral TBF and accounting for 1.5% of all TBF cases. Four of these five patients experienced delayedonset bilateral FNP, and one patient experienced immediate onset on one side and delayed onset on the other. All five patients developed incomplete FNP, with the most severe case scored House–Brackmann grade IV. Longitudinal TBF was the cause in all but one case, which resulted from mixed fractures on one side. All five patients were treated conservatively with oral steroids and physiotherapy.
Conclusions
Although bilateral traumatic FNP is rare, it should be suspected in all cases of bilateral TBF, and close follow-up is required to achieve rapid diagnosis and enhance management. Because bilateral TBF strongly tends to be longitudinal, incomplete FNP is typical.
Introduction
Simultaneous bilateral facial nerve palsy (FNP) is a very rare condition, with an annual incidence rate of one case per five million [1]. Simultaneous bilateral involvement is defined as paralysis of both sides occurring within 4 weeks of each other [2]. The causes can be traumatic or non-traumatic (i.e., infection, neurological disorder, autoimmune conditions, degenerative disease, and systemic or metabolic causes). Temporal bone fracture (TBF) constitutes approximately 3% of the causes [1], and the majority result from road traffic accidents [3].
TBF can be classified into longitudinal, transverse, and mixed types in relation to the petrous pyramid axis. FNP is more common in the transverse type, although the incidence of this type is significantly lower than that of longitudinal and mixed types [4]. It is of paramount importance to classify traumatic FNP into immediate or delayed onset, and whether it is partial or complete palsy, as they suggest the nature of the nerve injury and determine the urgency and type of management. The early recognition and diagnosis of traumatic bilateral FNP in patients with traumatic brain injury can be particularly challenging due to a lack of facial asymmetry, and most patients are intubated and sedated during the first review.
The House–Brackmann (HB), Sunnybrook, and Sydney grading systems are usually used to assess the severity and monitor the progression of FNP clinically [5]. Electroneurography is an electrodiagnostic test commonly used in most otology centers to assess the percentage of facial nerve degeneration during the period from 3 days to 3 weeks and provide indication for facial nerve exploration. Unfortunately, these tests are less reliable in cases of bilateral FNP, as there is no normal side for comparison. The limited test available adds to the challenge in managing these cases.
The research on bilateral traumatic FNP is very limited, including mostly case reports. Thus, the management mainly depended on the surgeon’s personal experience and followed the principle of unilateral traumatic FNP. We did a retrospective record review of cases to determine the prevalence and outcomes of traumatic bilateral FNP.
Subjects and Methods
This 10-year retrospective study, conducted from January 1, 2010, to December 31, 2019, included patients with traumatic bilateral FNP treated at a tertiary hospital. The definition of traumatic bilateral FNP is FNP that occurred on bilateral sides secondary to trauma, and the time elapsed from paralysis of one side to paralysis of the other side does not exceed 4 weeks. The cases were traced using the hospital coding system employing the terms “temporal bone fracture” and “bilateral facial nerve palsy” from 2010 to 2019. Their records were traced and carefully analyzed. Data regarding the onset of FNP, severity, associated injury, management, and outcome were extracted. The inclusion criteria include all patients with bilateral FNP secondary to trauma who were treated and followed up by the otorhinolaryngology–head and neck surgery team at the Hospital Universiti Sains Malaysia (HUSM), with the diagnosis of bilateral traumatic FNP recorded in the HUSM coding system from 2010 to 2019. Meanwhile, exclusion criteria were patients with FNP prior to trauma and bilateral FNP secondary to iatrogenic cause (operation). Data are presented descriptively as numbers and percentages.
Ethical clearance
The study was approved by the Human Research and Ethical Committee of Universiti Sains Malaysia (USM/JEPeM/21080537). The requirement for informed consent was waived by the committee.
Results
Fig. 1 summarizes the number of cases observed during the study. There were a total of 336 TBF cases, of which 316 cases were unilateral, while the other 20 were bilateral. All cases with bilateral TBF developed at least unilateral FNP. Out of these, five cases were diagnosed with bilateral FNP. All five cases sustained bilateral TBF secondary to motor vehicle accident, and all of them were men aged 14–39 years.
Flowchart showing the number of cases being reviewed. FNP, facial nerve palsy; TBF, temporal bone fracture.
Table 1 shows the details of each case. Case number (CN) 1 was a car driver and was alleged skidded. He sustained severe traumatic brain injury (TBI) and intracranial bleeding (ICB), which required intubation on arrival to the hospital. Bilateral FNP was noticed simultaneously on day 6 post-trauma, after he was extubated. The HB grades were III on the right side and II on the left side. CN 2 was a back-seat passenger in a car that was alleged to have skidded. He sustained moderate TBI with no ICB, not requiring intubation, and his bilateral FNP, HB grade IV, was detected simultaneously on day 3 post-trauma. Another case (CN 3) was a front-seat passenger who was allegedly hit by a falling log from the lorry that was in front. He sustained severe TBI with ICB and was intubated for 4 days. He complained of bilateral facial weakness on day 8 posttrauma and on examination revealed bilateral FNP, HB grade IV. The other two cases were motorbike riders who allegedly collided with a car. CN 4 sustained moderate TBI with ICB, did not require intubation, and developed immediate FNP HB grade II, on the right side. The facial nerve progressively worsened to become HB grade IV. His left FNP developed later and was noted to be grades III and IV at 2 and 4 weeks posttrauma, respectively. CN 5 had severe TBI with no ICB, required intubation, and developed bilateral FNP, HB grade IV, on day 4 post-trauma. In addition, he also had bilateral abducens nerve palsy.
Details of each case of bilateral facial nerve palsy secondary to bilateral temporal bone fracture
All cases had bilateral hemotympanum with intact tympanic membranes. There was bilateral longitudinal TBF in all cases, except for CN 4, with a longitudinal fracture on one side and a mixed fracture on the other. Facial canal disruptions were seen in two cases (CN 2 and 4), involving the labyrinth segment and first genu. Ossicular disruption occurred in three cases (CN 2, 4, and 5). CN 1 had associated mild high-frequency hearing loss on one side and mild to moderate conductive hearing loss (CHL) on the other. Two cases (CN 2 and 3) had mild to moderate CHL, while CN 4 had mild to moderate mixed hearing loss (MHL), and CN 5 had moderate to profound MHL.
All cases were treated conservatively with oral prednisolone (started with 1mg/kg/day and a tapering for period of 2 weeks) and physiotherapy. The facial nerve completely back to normal in four cases. A case (CN 5) had shown incomplete recovery on both sides with HB grade III at 11 months of follow-up. Ossiculoplasty was performed in one patient (CN 5) with ossicular discontinuity, as the patient complained of significant hearing impairment, and pure tone audiometry showed a large air-bone gap. The other cases were not keen on ossiculoplasty as they claimed the hearing deficit did not disturb their daily activity.
Discussion
Bilateral FNP represents only <2% of all FNP [6]. Trauma contributes about 5% of all FNP, and 3% of cases are associated with TBF [7]. The exact incidence of traumatic bilateral FNP is not known; it is probably very rare, and the majority are published as case reports. A literature review published in 2015 by Eliçora, et al. [7] has found only eight cases from different institutions reported up to the date. Darrouzet, et al. [8] reported two cases of traumatic bilateral FNP among 115 cases of facial nerve injury caused by TBF over 13 years of a retrospective study.
There were five cases of traumatic bilateral FNP presented and treated at our hospital over ten years. All cases were associated with head injury and bilateral TBF. Interestingly, all cases with bilateral TBF developed FNP either unilaterally or bilaterally. Traumatic bilateral FNP accounts for about 25% of bilateral TBF and 1.5% of all TBF. Traumatic unilateral FNP was far higher, 36 cases or 75% of bilateral TBF and 10.7% of all TBF. These features showed that the incidence of traumatic FNP is very high in cases of bilateral TBF, and unilateral FNP is higher when there is bilateral TBF. The majority of bilateral FNP in our study were caused by longitudinal TBF; four cases sustained bilateral longitudinal TBF, and only one case sustained longitudinal TBF on one side and mixed TBF on the other.
Longitudinal TBF, although more common, constitutes about 90% of all TBF; however, the incidence of FNP is lower, about 10%–25% of cases [8]. Mixed TBF occur at rates 0%–20% [9]. FNP is generally more common (30%–50%) and more severe, and the prognosis is poor in transverse TBF [9]. The statistics of this previous study are probably true for unilateral TBF. In bilateral TBF, as the magnitude of injury seems to be higher and associated with a more severe type of longitudinal TBF; thus, a higher incidence of FNP was seen in longitudinal TBF in our study. In addition, it has been proposed that longitudinal fracture of petrous part of temporal bone can lead to backward displacement of the petrous apex and coronal splitting of the body of sphenoid, leading to mirror image fracture in the opposite temporal bone producing bilateral FNP, while a transverse fracture of the petrous bone will not involve bilateral facial nerves [6].
Road traffic accidents remained the main mode of injury, involved in all cases of our study, and it is consistent with other studies [7,8,10]. Widely and compulsory seatbelt use, as well as airbag use, is currently believed to reduce the severity of head injury and TBF, thus dramatically decreasing the incidence of facial nerve injury [8]. Two of our cases were associated with bilateral vestibulocochlear nerve injury, in which one of them also sustained bilateral abducens nerve palsy. TBF has been associated with intracranial injuries in 22% of the cases [11]. Three of our cases sustained severe TBI and ICB. However, the severity of traumatic bilateral FNP does not seem to be correlated with the severity of intracranial injury in our study.
Average young adult males are the most affected group, probably due to their more frequent outdoor activity and being on the road, which is consistent with other research [8,10]. Delayed onset FNP usually follows longitudinal TBF and accounts for the majority of the cases. Only one of our cases developed immediate FNP. Diamond and Frew [12] classified traumatic FNP into immediate and delayed onset. The facial nerve is directly injured at the site of fracture as a result of bone splinters, crush, or traction in immediate onset. Delayed onset can be due to edema, delayed arterial spasm, arterial or venous thrombosis, or external compression by hematoma. This classification is markedly important in terms of management, particularly in deciding the option of treatment, either conservative or surgical exploration and decompression, as well as the timing of surgery. However, it is quite difficult to detect FNP early, particularly when involving bilateral sides and the patient is intubated and sedated secondary to concomitant intracranial injury. Detection of Bell’s phenomenon and inadequate eyelid closure can be very helpful in this situation [6,9]. The timing of onset is best determined through a combination of early clinical records, imaging results, and observed signs in these types of cases.
Hemotympanum was observed in all cases, while ossicular disruption occurred in three; hence, all of them had a conductive component of hearing loss. Two patients also had a sensory component of hearing loss. Subsequent pure tone audiometry showed improvement in conductive element in cases without ossicular injury. Tympanic membranes were intact in all cases, and no cerebrospinal fluid otorrhea.
Apart from the history of immediate onset of FNP, disruption of the facial canal seen on high-resolution computed tomography (HRCT) of the temporal bone is the most important indication for facial nerve exploration [8,9]. Studies have shown that the perigeniculate region is the most common site of injury [13,14]. Contrast-enhanced magnetic resonance imaging was found to be another useful tool as it can reveal any inflammation and trauma to nerve, including clinically silent damage in trauma [15]. Especially connected to FNP, the enhancement of the distal intrameatal and labyrinthine segments is a specific finding [15].
The principle of management of traumatic bilateral FNP is almost identical to traumatic unilateral FNP, and it can be divided into medical and surgical management. The difference is probably in the decision which side requires more attention and an earlier intervention, especially when involving surgical management. The selection of treatment is based on clinical factors (onset of FNP), radiology (visualization of fracture line on HRCT), and electrophysiologic data (degree of degeneration or evidence of regeneration by EMG) [8]. Surgery is indicated in cases of immediate onset of FNP, a clear-cut fracture line of fallopian canal seen in HRCT, and evidence of severe FNP shown in EMG. Other than these, medical or conservative management has been proven to be beneficial, as seen in our cases. The timing and anatomical extent of facial nerve decompression are still controversial [16]. Chang and Cass [17] and Hato, et al. [18] advocate early exploration within 2 weeks. We believe surgery should be carried out as soon as possible once the criteria are fulfilled and following accurate clinical judgment and judicious use of electrodiagnostic tests. Electrophysiologic and clinical monitoring is recommended in delayed onset severe FNP without visualized fracture of fallopian canal on HRCT, and surgery may be performed later if there is no improvement within 6 months [8].
Steroids are widely used either as the main medical treatment or as adjunct to surgery in traumatic FNP, with an aim to reduce edema, swelling, and scar formation [19]. All our cases were given oral prednisolone with a total duration of 2 weeks, and four of them showed complete recovery, while the remaining one showed improvement.
In conclusion, although bilateral traumatic FNP is rare, it should be suspected in all cases with bilateral TBF, and a close follow-up is required to avoid delay in diagnosis and management. However, bilateral TBF tend to be longitudinal in almost all cases, thereby causing incomplete FNP.
Notes
Conflicts of Interest
The authors have no financial conflicts of interest.
Author Contributions
Conceptualization: Vshakri Ehdam, Mohd Khairi Md Daud. Data curation: Vshakri Ehdam. Formal analysis: Vshakri Ehdam. Methodology: Mohd Khairi Md Daud. Supervision: Mohd Khairi Md Daud. Writing—original draft: Vshakri Ehdam. Writing—review & editing: Mohd Khairi Md Daud. Approval of final manuscript: Vshakri Ehdam, Mohd Khairi Md Daud.
Funding Statement
None
Acknowledgments
The authors acknowledge the help of the staff at medical record department for providing the documents needed in the study.