Morphometry of the Digastric Ridge and Its Significance for Mastoid Surgeries—A Cadaveric Study

Objective: Digastric ridge (DR) is an important landmark to locate facial nerve (FN) and sigmoid sinus for mastoid surgeries and transmastoid approaches. We aim to look for the effect of temporal bone pneumatization on the morphometry of the DR and its relation to the adjoining structures. Methods: Temporal bones were harvested from unclaimed cadavers after the approval of the ethical committee. The dissection of the temporal bones was performed under a microscope, and the length of the DR and the distance between the mastoid segment of the FN and the anterior end of DR (FN-DR distance) were measured using a digital caliper. Stata version 14.0 was used to perform the statistical calculations. Results: Ninety-three temporal bones were microdissected (right:left = 47:46; well pneumatized:poorly pneumatized = 58:35). Mean length of the DR was 17.1 mm and was significantly longer in well-pneumatized bones ( P = .0000). The mean distance between the anterior end of the digastric ridge and the mastoid part of the facial nerve was 4 mm. The distance was significantly more in well-pneumatized bones. Conclusion: Prominence and the length of the DR, as well as the FN-DR distance, are significantly more in well-pneumatized bones compared to poorly pneumatized bones. This finding has potential surgical implications with reduced risk of injury to the FN resulting from a conspicuous DR in well-pneumatized bones.

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The depth of the facial nerve in the mastoid bone

International Journal of Otorhinolaryngology and Head and Neck Surgery ◽

10.18203/issn.2454-5929.ijohns20181009 ◽

2018 ◽

Vol 4 (3) ◽

pp. 666

Author(s):

B. Y. Praveen Kumar ◽

K. T. Chandrashekhar ◽

M. K. Veena Pani ◽

Sunil K. C. ◽

Anand Kumar S. ◽

...

Keyword(s):

Facial Nerve ◽

Temporal Bone ◽

Significant Variation ◽

Canal Wall ◽

Stylomastoid Foramen ◽

Cortical Mastoidectomy ◽

Canal Wall Down ◽

Canal Wall Down Mastoidectomy ◽

The Mean ◽

Temporal Bones

Background: The hallmark of the temporal bone is variation. Various important structures like the facial nerve run in the temporal bone at various depths which can be injured during mastoidectomy.Methods: Twenty wet cadaveric temporal bones were dissected. A cortical mastoidectomy was performed followed by a canal wall down mastoidectomy and the depth of the vertical segment of the facial nerve in the mastoid was determined. Results: The mean depth of the second genu was 13.82 mm. The mean depth of the stylomastoid foramen was 12.75 mm and the mean distance from the annulus at 6’0 clock to the stylomastoid foramen was 10.22 mm.Conclusions: There is significant variation in the average depth of the facial nerve in the mastoid.

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A New Landmark for Finding the Sigmoid Sinus in Suboccipital Craniotomies

Operative Neurosurgery ◽

10.1227/neu.0b013e3182082afc ◽

2011 ◽

Vol 68 (suppl_1) ◽

pp. ons1-ons6 ◽

Cited By ~ 2

Author(s):

Jair Leopoldo Raso ◽

Segastião Nataniel Silva Gusmão

Keyword(s):

Temporal Bone ◽

Light Emitting Diode ◽

Sigmoid Sinus ◽

Light Emitting ◽

Suboccipital Craniotomy ◽

Stylomastoid Foramen ◽

Inner Surface ◽

The Mean ◽

The Right ◽

Digital Caliper

Abstract BACKGROUND: The suboccipital craniotomy is one of the most commonly performed neurosurgical approaches. OBJECTIVE: To define a new cranial landmark, the digastric point, located at the top of the mastoid notch in the mastoid portion of the temporal bone that may assist surgeons performing this craniotomy and to study the relationships between this point and other surface landmarks. METHODS: Craniometric measures were taken from 127 dry human adult skulls (90 male and 37 female). The measures were taken in millimeters by a digital caliper. Transillumination of the skull with laser or light-emitting diode was used to assess the correspondence of the digastric point in the inner surface of the skull. RESULTS: The mean distance between the digastric point and the sigmoid sulcus in 254 measures was 3.10 mm (SD, 3.11 mm). The digastric point was over the sulcus of the sigmoid sinus in 49.6% of the cases on the right side and in 29.9% of the cases on the left side. The distance between the jugular point and the stylomastoid foramen was smaller on the right side (mean, 8.89 mm; SD, 2.61 mm; P = .041). Comparing genders regardless of side, the distances between the digastric and jugular points and from the jugular point to the stylomastoid foramen were smaller in female skulls (P = .000 and .006, respectively). CONCLUSION: The digastric point may be a useful landmark to expose the sigmoid sinus during suboccipital approaches.

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Correlation between temporal bone pneumatization, location of lateral sinus and length of the mastoid process

The Journal of Laryngology & Otology ◽

10.1017/s0022215100119942 ◽

1992 ◽

Vol 106 (6) ◽

pp. 485-489 ◽

Cited By ~ 32

Author(s):

S. Turgut ◽

M. Tos

Keyword(s):

Temporal Bone ◽

Middle Ear ◽

External Auditory Canal ◽

Sigmoid Sinus ◽

Mastoid Process ◽

Lateral Sinus ◽

Gross Pathology ◽

Significant Difference ◽

Temporal Bone Pneumatization ◽

Temporal Bones

AbstractThe relationship between temporal bone pneumatization and the location of the lateral sinus and length of the mastoid process was investigated in 60 fresh frozen adult temporal bones, by plain X-rays, computed tomography and surgical dissection including otomicroscopic findings. Temporal bone pneumatization was classified as small, moderate and large. After drilling, the shortest distances between the middle fossa dura and mastoid tip representing the mastoid length and between the sigmoid sinus and posterior border of external auditory canal were measured and compared to the degree of pneumatization. The distances in the specimens with pathological eardrum and adhesions in the middle ear were compared to the ones without gross pathology. The length of mastoid process was significantly shorter in specimens with small pneumatization than those with large (Mann Whitney P<0.001).The specimens with a pathological eardrum and middle ear adhesions had a significantly shorter mastoid length than those without gross pathology. There was no significant difference between degree of pneumatization and the shortest distance between sigmoid sinus and external auditory canal (Mann Whitney P>0.05). It is demonstrated that the ‘under-developed’ mastoid process can be a consequence of hampered pneumatization.

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Fully automated preoperative segmentation of temporal bone structures from clinical CT scans

Scientific Reports ◽

10.1038/s41598-020-80619-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

C. A. Neves ◽

E. D. Tran ◽

I. M. Kessler ◽

N. H. Blevins

Keyword(s):

Facial Nerve ◽

Inner Ear ◽

Temporal Bone ◽

Hausdorff Distance ◽

Sigmoid Sinus ◽

Ct Scans ◽

Automated Segmentation ◽

Dice Coefficient ◽

Lateral Skull Base ◽

End To End

AbstractMiddle- and inner-ear surgery is a vital treatment option in hearing loss, infections, and tumors of the lateral skull base. Segmentation of otologic structures from computed tomography (CT) has many potential applications for improving surgical planning but can be an arduous and time-consuming task. We propose an end-to-end solution for the automated segmentation of temporal bone CT using convolutional neural networks (CNN). Using 150 manually segmented CT scans, a comparison of 3 CNN models (AH-Net, U-Net, ResNet) was conducted to compare Dice coefficient, Hausdorff distance, and speed of segmentation of the inner ear, ossicles, facial nerve and sigmoid sinus. Using AH-Net, the Dice coefficient was 0.91 for the inner ear; 0.85 for the ossicles; 0.75 for the facial nerve; and 0.86 for the sigmoid sinus. The average Hausdorff distance was 0.25, 0.21, 0.24 and 0.45 mm, respectively. Blinded experts assessed the accuracy of both techniques, and there was no statistical difference between the ratings for the two methods (p = 0.93). Objective and subjective assessment confirm good correlation between automated segmentation of otologic structures and manual segmentation performed by a specialist. This end-to-end automated segmentation pipeline can help to advance the systematic application of augmented reality, simulation, and automation in otologic procedures.

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Bilateral temporal bone fractures: a case report

International Journal of Otorhinolaryngology and Head and Neck Surgery ◽

10.18203/issn.2454-5929.ijohns20175640 ◽

2017 ◽

Vol 4 (1) ◽

pp. 271

Author(s):

Kiran Natarajan ◽

Koka Madhav ◽

A. V. Saraswathi ◽

Mohan Kameswaran

Keyword(s):

Hearing Loss ◽

Case Report ◽

Facial Nerve ◽

Temporal Bone ◽

Facial Paralysis ◽

Bone Fractures ◽

Clinical Manifestations ◽

Csf Leak ◽

The Right ◽

Temporal Bones

Bilateral temporal bone fractures are rare; accounting for 9% to 20% of cases of temporal bone fractures. Clinical manifestations include hearing loss, facial paralysis, CSF otorhinorrhea and dizziness. This is a case report of a patient who presented with bilateral temporal bone fractures. This is a report of a 23-yr-old male who sustained bilateral temporal bone fractures and presented 18 days later with complaints of watery discharge from left ear and nose, bilateral profound hearing loss and facial weakness on the right side. Pure tone audiometry revealed bilateral profound sensori-neural hearing loss. CT temporal bones & MRI scans of brain were done to assess the extent of injuries. The patient underwent left CSF otorrhea repair, as the CSF leak was active and not responding to conservative management. One week later, the patient underwent right facial nerve decompression. The patient could not afford a cochlear implant (CI) in the right ear at the same sitting, however, implantation was advised as soon as possible because of the risk of cochlear ossification. The transcochlear approach was used to seal the CSF leak from the oval and round windows on the left side. The facial nerve was decompressed on the right side. The House-Brackmann grade improved from Grade V to grade III at last follow-up. Patients with bilateral temporal bone fractures require prompt assessment and management to decrease the risk of complications such as meningitis, permanent facial paralysis or hearing loss.

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Temporal bone Pneumatization in Otosclerosis

Otolaryngology ◽

10.1016/j.otohns.2008.09.004 ◽

2008 ◽

Vol 139 (6) ◽

pp. 850-853 ◽

Cited By ~ 1

Author(s):

Daniel T. Ganc ◽

Robert W. Jyung

Keyword(s):

Temporal Bone ◽

Statistical Significance ◽

Three Dimensional ◽

Neck Surgery ◽

Adult Patients ◽

Control Group ◽

Test Analysis ◽

Temporal Bone Pneumatization ◽

History Of ◽

Temporal Bones

Objectives To determine whether there is a difference in the pneumatization of temporal bones with otosclerosis versus normal temporal bones. Methods A retrospective study of 46 ears from 24 adult patients with otosclerosis and 64 ears from 47 adult patients in a control group. The study group included temporal bone CT scans available from patients with otosclerosis. The control group consisted of patients who had temporal bone CTs for reasons likely unrelated to a history of middle ear disease. Data were obtained with a virtual reality system that allows three-dimensional manipulation and analysis. Results The temporal bone pneumatization for the otosclerosis group was 4.82 ± 2.27 cm3 vs 6.06 ± 2.71 cm3 for the control group. Two-sample t test analysis revealed no statistical significance ( P = 0.059) between pneumatization in the control vs otosclerosis groups. Conclusion There is no difference in temporal bone pneumatization between patients with otosclerosis and a control population. Therefore, temporal bone pneumatization by itself is not an adequate explanation for the apparent protective effect of otosclerosis against otitis media. © 2008 American Academy of Otolaryngology-Head and Neck Surgery Foundation. All rights reserved.

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Morphometric analysis of anatomical relationships of the facial nerve for mastoid surgery

The Journal of Laryngology & Otology ◽

10.1258/0022215011908135 ◽

2001 ◽

Vol 115 (6) ◽

pp. 447-449 ◽

Cited By ~ 15

Author(s):

Asim Aslan ◽

Cihan Goktan ◽

Mevlut Okumus ◽

Serdar Tarhan ◽

Halis Unlu

Keyword(s):

High Resolution ◽

Facial Nerve ◽

Temporal Bone ◽

Morphometric Analysis ◽

External Auditory Canal ◽

Lateral Surface ◽

Sigmoid Sinus ◽

Ct Scans ◽

The Right ◽

Mastoid Surgery

Surgical anatomical relationships of the facial nerve (FN) with several landmarks used in mastoid surgery were studied in temporal bone axial high resolution CT scans of 90 patients (180 ears). The shortest distances between the FN and external auditory canal (EAC), sigmoid sinus (SS), posterior fossa dural plate (PFD), and joint of the bony EAC with the lateral surface of the mastoid (M) were measured. These measurements were also analysed in respect of pneumatization and side differences. On average, it was found that FN–EAC was 2.9 mm, FN–SS was 10.5 mm, FN–PFD was 7.3 mm and FN–M was 15.3 mm. FN–EAC was found to be longer in poorly pneumatized bones whereas other distances were longer in pneumatized bones. FN–M was found to be longer on the right side.

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Positional relationship between the facial nerve and other structures of the temporal bone

The Journal of Laryngology & Otology ◽

10.1258/002221504772784540 ◽

2004 ◽

Vol 118 (2) ◽

pp. 106-111 ◽

Cited By ~ 11

Author(s):

Peidong Dai ◽

Tianyu Zhang ◽

Keqiang Wang ◽

Jichang Song ◽

Wen Qian ◽

...

Keyword(s):

Facial Nerve ◽

Temporal Bone ◽

Partial Correlation ◽

Jugular Bulb ◽

High Resolution Computed Tomography ◽

Real Relationship ◽

Mastoid Pneumatization ◽

Variable Position ◽

Temporal Bones ◽

Relationship Of

The quantitative relationships between the position of the mastoid segment of the facial nerve, mastoid pneumatization and the positions of neighbouring structures are undetermined. Using high resolution computed tomography (HRCT), the positions of these structureswere measured in 66 normal temporal bones. A new method for measuring the volume of pneumatization in the temporal bone based on the serial digital images of CT was designed. The method of partial correlation analysis was used to find the real relationship of the two variables. The results suggest that the factors that influence the position of the mastoid segment of the facialnerve are complicated and multiple. The development of the cranium including the temporal bone,the temporal bone pneumatization and the variable position of the jugular bulb are considered to be important factors.

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Auditory and Temporal Bone Abnormalities in Charge Association

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348948609500509 ◽

1986 ◽

Vol 95 (5) ◽

pp. 480-486 ◽

Cited By ~ 40

Author(s):

Charles G. Wright ◽

William L. Meyerhoff ◽

O. E. Brown ◽

J. C. Rutledge

Keyword(s):

Hearing Loss ◽

Facial Nerve ◽

Temporal Bone ◽

Choanal Atresia ◽

Charge Syndrome ◽

Oval Window ◽

Congenital Defects ◽

Auditory Brain Stem Response ◽

Charge Association ◽

Temporal Bones

CHARGE association is a recently described cluster of congenital defects including ocular coloboma, heart disease, choanal atresia, retarded development and/or CNS abnormalities, genital hypoplasia, and ear anomalies. Although congenital hearing loss has been reported in CHARGE association, no information regarding the underlying temporal bone disease is available in the literature to date. The authors evaluated four patients with multiple anomalies consistent with CHARGE syndrome. Two surviving patients have bilateral severe hearing loss on auditory brain stem response testing. Two patients did not survive, and their temporal bones were obtained at autopsy for histologic examination. All four temporal bones showed severe middle ear defects including ossicular deformities, absence of the stapedius muscle, absence of the oval window, aberrant course of the facial nerve, and dehiscence of the facial nerve canal. In the more severely affected case, a Mondini-type malformation of the cochlea was present, together with multiple anomalies of the vestibular apparatus. Vestibular defects also occurred in the other case; however, the cochleae were found to be normally developed.

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