Facial nerve course in the temporal bone: Anatomical relationship between the tympanic and mastoid portions for safe ear surgery.

OBJECTIVE: Avoidance of iatrogenic injury to the facial nerve is crucial during ear surgery. The anatomical relationship between the tympanic portion of the facial canal (FC) and the mastoid portion of the facial nerve was analyzed using multi-slice computed tomography (CT) scans to avoid iatrogenic facial nerve injury. METHODS: In total, 364 ears of 351 patients who underwent CT scans were enrolled. The 364 ears were divided into two groups: 281 ears with middle ear inflammation (MEI) and 83 ears without middle ear inflammation (non-MEI). The anatomical relationship between the tympanic portion of the FC and mastoid portion of the facial nerve was analyzed on multi-slice CT images. The ears were categorized into three subgroups based on the course of the mastoid portion of the facial nerve to the tympanic portion of the FC: ("lateral running course", LRC), "on the tympanic line course" (OL), and "medial running course" (MRC). The proportions of ears in each subgroup were compared between the MEI and non-MEI groups. RESULTS: Overall, 15% of ears were categorized as LRC, 30% were OL, and 55% were MRC. In the MEI group, the proportions of LRC, OL, and MRC ears were 17%, 32%, and 51%, respectively, whereas they were 7%, 24%, and 69% in the non-MEI group. The proportion of LRC ears in the MEI group was significantly higher than that in the non-MEI group. CONCLUSIONS: Especially in patients with MEI, a more LRC for the facial nerve increases the risk of facial nerve injury during posterior tympanotomy or canal wall down mastoidectomy. The course of the facial nerve in the temporal bone should be evaluated before surgery on multi-slice CT images.

Anatomical assessment of the digastric branch of the facial nerve as a landmark to localize the extratemporal facial nerve trunk.

PURPOSE: Localization of the facial nerve trunk (FNT) [i.e., the portion of the facial nerve between the stylomastoid foramen (SMF) and pes anserinus] may be required during various surgical interventions such as parotidectomy and hypoglossal-facial anastomosis. Several landmarks have been proposed for efficient identification of the FNT. We sought to assess the anatomical features of the digastric branch of the facial nerve (DBFN) and its potential as a landmark to identify FNT. METHODS: Fifteen sides of eight cadaveric heads were dissected to find the DBFN. Anatomic features of DBFN including its point of origin relative to SMF, length, and important relationships, as well as the distance between the insertion point on the digastric muscle and mastoid tip were recorded. RESULTS: DBFN was found in all specimens originating from the FNT outside the SMF with an average length (± standard deviation) of 15.4 ± 3.4 mm. In all specimens, the DBFN inserted on the superomedial aspect of the posterior belly of the digastric muscle (PBD). In 8/15 specimens, DBFN was accompanied by the stylomastoid artery on its anteromedial side. Average distance (± standard deviation) between the mastoid tip and the nerve insertion point on PBD was 13.6 ± 2.0 mm (range 10-17). CONCLUSIONS: The DBFN is a reliable landmark for identifying the FNT. It could be consistently identified within 15-20 mm of the mastoid tip on the superomedial aspect of the PBD. The DBFN may be used as a supplementary landmark for efficient localization of the FNT. LEVEL OF EVIDENCE: Not applicable (anatomic study).

Nucleolus vs Nucleus Count for Identifying Spiral Ganglion in Human Temporal Bone.

OBJECTIVES: Spiral ganglion (SG) counting is used in experimental studies conducted on age-, noise-, and drug-induced sensorineural hearing loss, as well as in the assessment of cochlear implant performances. Different methods of counting have been reported, but no definite standardization of such procedure has been published. The aim of our study is to identify the best method to count human spiral ganglions (SGs). MATERIALS AND METHODS: By identification of nuclei or nucleoli as described by Schucknect, seven researchers with different experience levels counted SGs in 123 human temporal bones (TBs). Data on time of post-mortem bone removal post-mortem, methods of specimen's fixation, decalcification, and coloration were collected to test their possible influence on human tissue. Percentage, two-tailed t-test, Spearman's test, and one-way ANOVA were used to analyze the data. RESULTS: Nucleoli were identified in 61% of cases, whereas nuclei were recognized in 100% of cases (p<0.005). Nucleoli presence in all four segments in the same temporal bone (TB) was observed in 69 cases (92%), whereas nuclei were identified in all four segments in 103 cases (83.7%) (p<0.001). The junior investigators requested a double check by the seniors in 25 (20.3%) cases for identifying and counting nucleoli, whereas the senior researchers showed no doubts in their identification and count. The only parameter positively affecting nucleoli identification in tissue preparation was bone removal for <12 h with respect to longer post-mortem time (p<0.001). CONCLUSION: We suggest counting nuclei, rather than nucleoli, for spiral ganglion computation because of easier recognition of nuclei, especially in case of investigator's limited experience.

Micro-CT study of the dehiscences of the tympanic segment of the facial canal.

PURPOSE: To depict the anatomy of the tympanic segment of the facial canal using a 3D visualization technique, to detect dehiscences, and to evaluate their frequency, location, shape, and size. METHODS: Research included 36 human temporal bones (18 infant and 18 adult samples) which were scanned using a Nanotom 180N device. The final resolution of the reconstructed object was 18 µm. Obtained micro-CT data were subsequently processed by the volume rendering software. RESULTS: The micro-CT study allowed for the 3D visualization of the tympanic segment of the facial canal and detects dehiscences in the studied material in both infants and adults. Most of the dehiscences (66.7 %) involved the inferior wall of the tympanic segment in infants as well as in adults, and were located above and backward to the oval window. The most frequent dehiscence shape was elliptic (66.7 % in infants; 50 % in adults). Furthermore, we observed dehiscences of fusiform and trapezoidal shape in infants. Length of the dehiscences in most cases ranged from 0.5 to 1.4 mm (50 % in infants; 75 % in adults). CONCLUSIONS: Volumetric reconstructions demonstrated the course of the tympanic segment of the facial canal and its relationship with the tympanic cavity. Knowledge about the size and location of any dehiscence within the tympanic segment of the facial canal is necessary due to the surgical significance of this region. If a dehiscence occurs, there is an increased risk of injury to the facial nerve during the operations or spread of inflammation from the middle ear.

Neural connections between the nervus intermedius and the facial and vestibulocochlear nerves in the cerebellopontine angle: an anatomic study.

PURPOSE: Unexpected clinical outcomes following transection of single nerves of the internal acoustic meatus have been reported. Therefore, this study aimed to investigate interneural connections between the nervus intermedius and the adjacent nerves in the cerebellopontine angle. METHODS: On 100 cadaveric sides, dissections were made of the facial/vestibulocochlear complex in the cerebellopontine angle with special attention to the nervus intermedius and potential connections between this nerve and the adjacent facial or vestibulocochlear nerves. RESULTS: A nervus intermedius was identified on all but ten sides. Histologically confirmed neural connections were found between the nervus intermedius and either the facial or vestibulocochlear nerves on 34 % of sides. The mean diameter of these small interconnecting nerves was 0.1 mm. The fiber orientation of these nerves was usually oblique (anteromedial or posterolateral) in nature, but 13 connections traveled anteroposteriorly. Connecting fibers were single on 81 % of sides, doubled on 16 %, and tripled on 3 %, six sides had connections both with the facial nerve anteriorly and the vestibular nerves posteriorly. On 6.5 % of sides, a connection was between the nervus intermedius and cochlear nerve. For vestibular nerve connections with the nervus intermedius, 76 % were with the superior vestibular nerve and 24 % with the inferior vestibular nerve. CONCLUSIONS: Knowledge of the possible neural interconnections found between the nervus intermedius and surrounding nerves may prove useful to surgeons who operate in these regions so that inadvertent traction or transection is avoided. Additionally, unanticipated clinical presentations and exams following surgery may be due to such neural interconnections.

Facial nerve stimulation in the narrow bony cochlear nerve canal after cochlear implantation.

OBJECTIVES/HYPOTHESIS: To evaluate the correlation between a narrow bony cochlear nerve canal (BCNC) and facial nerve stimulation (FNS) after cochlear implantation (CI) and their underlying mechanisms and to predict the risk of FNS preoperatively. STUDY DESIGN: Retrospective cohort study. METHODS: A total of 64 pediatric cases that underwent CI were included. Among them, 32 cases experienced FNS after CI, and another 32 cases were selected from 817 pediatric implantees by stratified random sampling. The width of the BCNC, the status of the cochlear nerve (CN) and the internal auditory canal (IAC), T level, and C level were compared and analyzed. Strategies for eliminating FNS were also analyzed. RESULTS: The FNS group showed a narrower BCNC (1.09 ± 0.52 mm) than the control group (1.99 ± 0.61 mm; P < .01), a lower CN/facial nerve ratio (0.32 ± 0.36) than the control group (1.34 ± 0.76; P < .01), and narrower IAC diameter (4.06 ± 1.71 mm) than the control group (5.66 ± 1.36 mm; P < .01). The FNS group also showed higher T level (165.7 ± 28.3 µA) than the control group (142.2 ± 21.2 µA; P < .01). Adjustment of the C levels and/or pulse width and switching off offending electrodes were attempted to eliminate FNS, with a 75.0% success rate. The FNS group still showed low Categories of Auditory Performance scores (3.00 ± 1.90) compared with the control group (5.94 ± 1.41, P < .01) after adjustment. CONCLUSIONS: A narrow BCNC could be a cause of FNS after CI. Therefore, careful selection of the side for CI and programming strategies are required to reduce FNS. LEVEL OF EVIDENCE: 4. Laryngoscope, 126:1433-1439, 2016.

Occult Temporal Bone Facial Nerve Involvement by Parotid Malignancies with Perineural Spread.

OBJECTIVE: To characterize disease presentation and outcomes following surgical treatment of parotid malignancies with occult temporal bone facial nerve (FN) involvement. STUDY DESIGN: Case series with chart review. SETTING: Tertiary academic referral center. SUBJECTS AND METHODS: Thirty consecutive patients (mean age 58 years; 77% men) who underwent surgery for parotid malignancies with occult perineural involvement of the intratemporal FN were included. Primary outcome measures included margin status and recurrence. RESULTS: The mean duration of clinical follow-up was 49 months, and the most common presenting symptom was FN paresis (n = 23; 77%) followed by pain (n = 15; 50%). To obtain a proximal FN margin, 27 patients (90%) underwent mastoidectomy, and 3 patients (10%) had lateral temporal bone resection. The intratemporal FN margin was cleared in 26 patients (87%), most commonly in the mastoid segment (60%). Adjuvant therapy was given in 25 patients (83%). Ten patients (33%) experienced locoregional (4; 13%) and/or distant (8; 27%) recurrence at a median of 19 months (mean 26, 2-54 months) following surgery. Locoregional failure was significantly more common in cases with a positive intratemporal FN margin (66% vs 8%; P = .045). Overall 1-, 3-, and 5-year disease-specific survival rates were 83%, 79%, and 72%, respectively. CONCLUSIONS: Perineural invasion of the intratemporal FN by parotid malignancy is uncommon. Normal preoperative FN function does not preclude histopathologic involvement. Temporal bone FN exploration should be considered when a positive margin is encountered at the stylomastoid foramen, as failure to do so is associated with an increased rate of locoregional recurrence.

Intrinsic facial nerve tumours of the temporal bone: a proposed management guideline.

OBJECTIVE: The aim of this paper was to propose a guideline for the management of intrinsic facial nerve tumours based on our practice and findings in the literature. METHOD: A retrospective review of intrinsic facial nerve tumours over the last 15 years was performed. Parameters measured included age, presenting symptoms, pre- and post-treatment hearing and House-Brackmann grading, tumour position, treatment and duration of follow up. RESULTS: A total of 15 patients presented with intrinsic facial nerve tumours over the study period. The most common presenting complaint was facial symptoms (93.3 per cent), followed by hearing loss (46.7 per cent). Three patients with stable facial nerve function (House-Brackmann grades II-III) were treated conservatively. Twelve patients underwent surgery to treat progressive or recurrent symptoms. Facial function was maintained or improved in 60.0 per cent of patients and hearing was preserved in 66.7 per cent. CONCLUSION: We propose that all stable tumours associated with good facial function of grade III or below should be treated conservatively. For symptomatic or progressive lesions, tailored surgery depending on the tumour site and hearing level should be offered to preserve native nerve function and facial musculature. For patients with prolonged paralysis, tumours can be monitored and other forms of facial reanimation and support offered.

Endoscopic approach to the trigeminal nerve: an anatomic study.

OBJECTIVE: To describe an endoscopic perspective of the surgical anatomy of the trigeminal nerve. METHODS: Nine adult cadaveric heads were dissected endoscopically. RESULTS: Opening the pterygopalatine fossa is important because many key anatomical structures (V2, pterygopalatine ganglion, vidian nerve) can be identified and traced to other areas of the trigeminal nerve. From the pterygopalatine ganglion, the maxillary nerve and vidian nerve can be identified, and they can be traced to the gasserian ganglion and internal carotid artery. An anteromedial maxillectomy increases the angle of approach from the contralateral nares due to an increase in diameter of the piriform aperture, and provides excellent access to the mandibular nerve, the petrous carotid, and the cochlea. CONCLUSIONS: Identification of key anatomical structures in the pterygopalatine fossa can be used to identify other areas of the trigeminal nerve, and an anteromedial maxillectomy is necessary to expose the ipsilateral mandibular nerve and contralateral cranial level of the trigeminal nerve.

Three-dimensional courses of zygomaticofacial and zygomaticotemporal canals using micro-computed tomography in Korean.

The zygomatic nerve (ZN), which originates from the maxillary nerve at the pterygopalatine fossa, enters the orbit through the inferior orbital fissure. Within the lateral region of the orbit, the ZN divides into the zygomaticofacial (ZF) and zygomaticotemporal (ZT) nerves. The ZF and ZT nerves then pass on to the face and temporal region through the zygomaticoorbital foramen and enter their own bony canals within the zygomatic bone. However, multiple zygomaticofacial and zygomaticotemporal canals (ZFCs and ZTCs, respectively) can be observed, and their detailed intrabony courses are unknown. The aim of this study was clarify the three-dimensional intrabony courses and running patterns of the ZFCs and ZTCs, both to obtain a detailed anatomical description and for clinical purposes. Fourteen sides of the zygomatic bones were scanned as two-dimensional images using a micro-computed tomography (CT), with 32-µm slice thickness. Intrabony structures of each canals were three-dimensionally reconstructed and analyzed using Mimics computer software (Version 10.01; Materialise, Leuven, Belgium). We found that some ZTC was originated from ZFC. In 71.4% of the specimens, the ZTC(s) divided from the intrabony canal along the course of the ZFC(s). In other cases, 28.6% of ZTCs were opened through each corresponding ZT foramen. Zygomaticofacial canal originates from zygomaticoorbital foramen, divided into some of ZTCs, and is finally opened as ZF foramen. This new anatomical description of the intrabony structures of the ZFC(s) and ZTC(s) within the zygomatic bone by micro-CT technology provided helpful information to surgeons performing clinical procedures such as Le Fort osteotomy and reconstructive surgeries in the midface region.

Measurement and analysis of facial nerve on fully displayed multislice computed tomographic multiplanar reconstruction image.

The objectives of this study were to measure the length of horizontal segment of facial nerve (HFN), the length of vertical segment of facial nerve (VFN), and the angle between these 2 segments on a fully displayed multislice computed tomographic multiplanar reconstruction (MPR) images of HFN and VFN and to analyze the data with respects to side, sex, and age. Parameters of 234 patients (468 observations, 118 men and 116 women, aged 4-70 years) with intact temporal bone were measured on multislice computed tomographic multiplanar reconstruction images. The data gained were analyzed by statistical method. The left and right lengths of VFN were significantly different (P < 0.05). And the length of HFN, the length of VFN, and the angle between males and females were significantly different (P < 0.05). We divided the data into 3 groups to study correlations between measurements and age. In underaged group, there was a strong positive correlation between the length of VFN and age; the value of Pearson correlation was 0.645. And there was a weak correlation between the angle and the age; the value of Pearson correlation was 0.270. In older-aged group, there was a moderate negative correlation between the length of VFN and age; the value of Pearson correlation was -0.408. Our results are of high potential to expand the visual field to facial nerve and may provide more detailed information to surgeries of facial nerve, middle ear, and temporal bone.

Anastomoses of the vestibular, cochlear, and facial nerves.

The internal auditory canal (IAC) is 10 to 17 mm in length, and the facial nerve and vestibulocochlear nerve, which consist of the cochlear nerve, the superior vestibular nerve, and the inferior vestibular nerve, run together in the IAC packaged in dura mater. Oort first described the vestibulocochlear anastomoses in 1918, which is important for the understanding of the pathogenesis and pathophysiology of otologic disorders. The current study documents the existence of vestibulofacial and vestibulocochlear neural connections and topographical relationship of the nerves as part of a radiologic evaluation of 73 human temporal bones from brainstem to the lateral portion of IAC.

Clinical feasibility of temporal bone magnetic resonance imaging as a prognostic tool in idiopathic acute facial palsy.

OBJECTIVE: To assess the feasibility of temporal bone magnetic resonance imaging for evaluating the severity and prognosis of idiopathic acute facial nerve palsy. METHODS: Forty-four patients with idiopathic acute facial nerve palsy who had undergone gadolinium-enhanced magnetic resonance imaging were selected retrospectively. The degree of radiological facial nerve enhancement was determined using quantitative analysis (with region-of-interest measurements for separate facial nerve segments) and using subjective visual analysis. The clinical severity of facial nerve palsy was then correlated with the degree of facial nerve enhancement. RESULTS: The visually determined degree of facial nerve enhancement did not correlate significantly with the House-Brackmann grade at either the early or late stages (p > 0.05). Results using the region-of-interest system were similar (p > 0.05). CONCLUSION: Temporal bone magnetic resonance imaging is not essential for patients with acute facial nerve palsy.

Contemporary techniques for the correction of temporal hollowing: augmentation temporoplasty with the classic dermal fat graft.

INTRODUCTION: Temporal hollowing is a depression within the soft tissues overlying the temporal fossa, sometimes seen after surgical dissection for access to the facial skeleton. Surgeons have successfully used bone grafts, hydroxyapatite, methyl methacrylate, and autogenous tissue to correct the deformity. A systematic review of the literature demonstrated that the most popular technique for the correction of temporal hollowing seems to be the use of nonbiologic materials. These materials have been used successfully but are associated with some complications. There has been a growing experience with augmentation of the soft tissues of the temporal fossa using dermal fat grafts at our institutions, and this article describes this experience. METHODS: Two senior surgeons' recent experience with the correction of temporal hollowing was reviewed and analyzed. RESULTS: The retrospective review revealed 5 cases of temporal hollowing treated with dermal fat graft placement. Follow-up at 1 year revealed aesthetically pleasing results. CONCLUSIONS: A thorough understanding of temporal anatomy and conscious effort to respect structural integrity during dissection are essential in avoiding temporal hollowing. Sometimes, however, this deformity is impossible to avoid. In these patients, there are a number of options for correction. Open placement of the classic dermal fat graft is a technique that seems to offer good long-term aesthetic results.

Transcervical double mandibular osteotomy approach to the infratemporal fossa.

BACKGROUND: In this study, we propose an alternative to the traditional transmandibular lower lip and chin splitting approach for exposing high infratemporal fossa and parapharyngeal space lesions involving the carotid canal and jugular foramen. METHODS: We present 2 cases of high skull base tumors removed transcervically with anterior and posterior segmental mandibulotomies preserving the mental nerve without the use of a lip or chin incision. RESULTS: Making the posterior osteotomy in an inverted L configuration is necessary so that the coronoid process does not prevent rotation of the mandible out of the visual field. Both patients had complete tumor resection with access to the carotid canal and jugular foramen and functional preservation of the mental nerve and marginal branch of the facial nerve. Neither patient had malocclusion or other dental complications from the approach. CONCLUSIONS: This novel technique is useful for providing excellent access to high infratemporal fossa or parapharyngeal space tumors. It avoids the traditional chin or lip incision and preserves the mental and facial nerves and is a useful procedure in the armamentarium of skull base/cerebrovascular neurosurgeons.

Double facial nerve trunk emerged from the stylomastoid foramen and petrotympanic fissure: a case report.

There are several studies concerning branches of the facial nerve, but we encountered less information about the trunk of the facial nerve in the literature. During the routine dissection of a 65-yr-old Caucasian male cadaver, double facial nerve trunk emerged from the stylomastoid foramen and petrotympanic fissure were encountered. Because of an extremely rare variation, we presented this case report. In addition this cadaver had two buccal plexuses. These plexuses and other branches were formed to structures like to polygon. These anatomic peculiarities were described, photographed and illustrated. Finally, magnetic resonance imaging was performed by using 1.5T scanner to this cadaver. The facial nerve trunk can be damaged during surgical procedures of the parotid gland tumours and submandibular region. Surgeons who are willing to operate on this area should be aware of the possible anatomical variations of the facial nerve trunk.

Intratemporal course of the facial nerve: morphological, topographic and morphometric features.

The purpose of this study is to present some morphological and morphometric aspects of the facial nerve and especially of the tympanic and mastoid segments of this nerve. The authors follow up a mesoscopic study concerning the tract (length, angulation, width) of these segments and the anatomic relations with the important structures of the middle ear. At the same time, some anatomical variations which involve the canal of the facial nerve (dehiscences, tract deviation or other anatomical deviations) are presented. To evaluate the risk of the facial nerve injury during operations for chronic otitis media with or without cholesteatoma, stapedectomy in otosclerosis, exploratory tympanotomy, tympanoplasty, canaloplasty, osteomas surgery or other otologic surgery that involve facial nerve area. The intricate course of the facial nerve through the temporal bone is of vital concern to all otologic surgeons, since it often traverses the surgical field. Therefore, authors will review the course of the facial canal through the petrosal portion of the temporal bone from the internal auditory meatus to the stylomastoid foramen, paying particular attention to its relations to adjacent structures.

Morphology and compartmentation of the jugular foramen in adult Indian skulls.

PURPOSE: Knowledge of the complex anatomy of the jugular foramen is vital for a favorable surgical outcome in technically challenging operations of this region. Various reports about the compartmentation of this foramen and the contents passing through them have come up with conflicting observations. METHOD: As many as 116 dry, adult skulls were utilized to study the morphology and the compartmentation of the jugular foramen. RESULTS: The study demonstrates and describes the precise location and frequency of occurrence of processes bridging the foramen and clarifies the existing ambiguity and confusion regarding the compartmentation and the contents passing through. A comprehensive classification for the bridging pattern and compartmentation of the jugular foramen is suggested. CONCLUSION: This information will be of help to the clinicians for understanding clinical presentations and progression of the lesions of the jugular foramen region and planning for the operations.

Double Facial Nerve Trunk Emerged from the Stylomastoid Foramen and Petrotympanic Fissure: A Case Report

There are several studies concerning branches of the facial nerve, but we encountered less information about the trunk of the facial nerve in the literature. During the routine dissection of a 65-yr-old Caucasian male cadaver, double facial nerve trunk emerged from the stylomastoid foramen and petrotympanic fissure were encountered. Because of an extremely rare variation, we presented this case report. In addition this cadaver had two buccal plexuses. These plexuses and other branches were formed to structures like to polygon. These anatomic peculiarities were described, photographed and illustrated. Finally, magnetic resonance imaging was performed by using 1.5T scanner to this cadaver. The facial nerve trunk can be damaged during surgical procedures of the parotid gland tumours and submandibular region. Surgeons who are willing to operate on this area should be aware of the possible anatomical variations of the facial nerve trunk.

Orbital restoration surgery in the zygomaticotemporal and zygomaticofacial nerves and important anatomic landmarks.

A variety of etiologies may result in functional and aesthetic deficiencies requiring orbital reconstruction. Fractures of the zygomaticomaxillary complex in the acute stage are frequently accompanied by sensory disturbances of the zygomatic nerve (ZN). The purpose of the current study was to describe the anatomic and topographic landmarks of the ZN in 18 adult human cadavers regarding the localization and dimensions in the orbit. The zygomaticotemporal (ZTN) and zygomaticofacial nerves (ZFN) along the lateral wall of the orbit passed through the zygomaticotemporal and zygomaticofacial foramens, respectively. The angle between the ZTN and the ZFN within the orbit was approximately 42.21 degrees. The mean (SD) distance between the orbital opening of the ZTN and the meeting point of the ZTN was measured as 9.21 (5.18) mm. The mean (SD) distance between the orbital opening of the ZFN and the meeting point of the ZTN was calculated as 11.22 (4.25) mm. The mean (SD) distance between the orbital opening of the ZFN and the infraorbital margin of the orbit was 13.04. (3.21) mm. A detailed knowledge of the ZN's passage in the orbit is necessary for a surgeon while performing maxillofacial surgery. If these measurements are taken into account, there will be little surgical risk, and this will be helpful in identifying the extent of the operative field.