Study of Sigmoid Sinus Variations in the Temporal Bone by Micro Dissection and its Classification - A Cadaveric Study

Singh, Anup; Irugu, David Victor Kumar; Sikka, Kapil; Verma, Hitesh; Thakar, Alok

doi:10.1055/s-0039-1688455

Anup Singh

Department of Otorhinolaryngology and Head & Neck Surgery, All India Institute of Medical Sciences, New Delhi, Delhi, India

David Victor Kumar Irugu

Department of Otorhinolaryngology and Head & Neck Surgery, All India Institute of Medical Sciences, New Delhi, Delhi, India

https://orcid.org/0000-0002-1732-6504

Kapil Sikka

Department of Otorhinolaryngology and Head & Neck Surgery, All India Institute of Medical Sciences, New Delhi, Delhi, India

Hitesh Verma

Department of Otorhinolaryngology and Head & Neck Surgery, All India Institute of Medical Sciences, New Delhi, Delhi, India

Alok Thakar

Department of Otorhinolaryngology and Head & Neck Surgery, All India Institute of Medical Sciences, New Delhi, Delhi, India

Address for correspondence David Victor Kumar Irugu, MS, Department of Ear, Nose, and Throat, Teaching block, All India Institute of Medical Sciences, 4th floor, Room no.-4057, Ansari Nagar, New Delhi, 110029, India (e-mail: drdvki2776@gmail.com).

Conflicts of Interests

Irugu D. V. K. reports grants from the All India Institute of Medical Sciences, New Delhi, India, during the conduct of the study; grants from the All India Institute of Medical Sciences, New Delhi, India, outside the submitted work.

Figures (3)
Tables (4)

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Fig. 1
(A) Dissected temporal bone with marked anatomical reference points for anatomical grading of SS (B) SS grade I: The SS, PSBP, and PSCC are in the same vertical plane. All of the three structures are fully visible with good exposure of the Trautmann triangle and a voluminous mastoid cavity. (C) SS grading II: The SS is anteriorly placed obscuring the PSBP, but the PSCC can be seen. With the anterior placement of the SS, narrowing of Trautmann triangle and the reduction in the volume of the mastoid cavity can be appreciated. (D) SS grading III: Further anteriorly placed SS obscuring the PSBP and the PSCC with a significantly compromised volume of the mastoid cavity and significant reduction of the exposure of the Trautmann triangle. Abbreviations: AD, aditus; DR, digastric ridge; EAC, external auditory canal; LSCC, lateral semicircular canal; PMW, posterior meatal wall; PSBP, presigmoid bony plate; PSCC, posterior semicircular canal; SDA, sinodural angle; SS, sigmoid sinus; SSCC, superior semicircular canal.

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Fig. 2
Box and whiskers plot of sigmoid sinus grading with the volume of the mastoid cavity. (x-axis: sigmoid sinus grade; y-axis: volume of the mastoid cavity in ml; Vol: volume). (The boxes represent the interquartile range [the middle 50% of volume distribution], and the whiskers encompass the entire range of volume distribution. The lines dividing the boxes represent the median, and the dots outside the boxes are the outliers).

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Fig. 3
Box and whiskers plot of the correlation of results between the volume of the mastoid cavity with the sigmoid sinus grading and pneumatization (x-axis: sigmoid sinus groups; y-axis: volume of the mastoid cavity in ml). (The boxes represent the interquartile range {the middle 50% of volume distribution} and the whiskers encompass the entire range of volume distribution. The line dividing the box represents the median and the dots outside the box are the outliers). Abbreviations: NP, underpneumatized; P, well-pneumatized; SS, sigmoid sinus; Vol;, volume.

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Table 1
Distribution of bones according to pneumatization

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Table 2
Comparative results of sigmoid sinus grading with the volume of the mastoid cavity

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Table 3
Distribution of bones with respect to sigmoid sinus grading and pneumatization with the summary of the volume of the mastoid cavity

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Table 4
Lliterature review of classifications of sigmoid sinus variations

Pneumatisation	Bone side		Sigmoid sinus grading
Pneumatisation	Right	Left	I	II	III
Well-pneumatized	31	28	34	23	2
Underpneumatized	16	19	3	16	16
Total	47	47	37	39	18

Sigmoid sinus grading (Irugu & Singh)	Mean Volume (SD); (ml)	Number of bones (%)
I	6.58 (0.90)	37 (39.4)
II	4.41(0.84)	39 (41.5)
III	1.95 (0.69)	18 (19.1)

Sigmoid sinus grading and pneumatisation	Summary of the volume of the mastoid cavity; mean (SD); (ml)	Number of bones (%)
SSG I WP	6.64 (0.91)	34 (36.2)
SSG I UP	5.93 (0.51)	3 (3.2)
SSG II WP	4.69 (0.87)	23 (24.5)
SSG II UP	4.01 (0.62)	16 (17.0)
SSG III WP	3.25 (0.35)	2 (2.1)
SSG III UP	1.79 (0.53)	16 (17.0)

S. No.	Author and Year	Basis of the Classification [reference]
1	Ichijo et al (1993)	Shape of the sigmoid sinus⁷7 Ichijo H, Hosokawa M, Shinkawa H. Differences in size and shape between the right and left sigmoid sinuses. Eur Arch Otorhinolaryngol 1993;250(05):297-299
2	Kayalioglu et al (1996)	Anatomical position of the sigmoid sinus in the mastoid cavity²2 Kayalioglu G, Gövsa F, Ertürk M, Arisoy Y, Varol T. An anatomical study of the sigmoid sulcus and related structures. Surg Radiol Anat 1996;18(04):289-294
3	Sarmiento et al (2004)	Based on the narrowing of the Trautmann triangle⁴4 Sarmiento PB, Eslait FG. Surgical classification of variations in the anatomy of the sigmoid sinus. Otolaryngol Head Neck Surg 2004;131(03):192-199
4	Sun et al (2009)	Three imaginary radiological (computed tomography) reference lines theory¹1 SunD, Lee DH, Jang KH, et al.A SuggestedNewClassification System for the Anatomic Variations of the Sigmoid Sinus: A Preliminary Study. J Int Adv Otol 2009;5(01):1-5

[1] Address for correspondence David Victor Kumar Irugu, MS, Department of Ear, Nose, and Throat, Teaching block, All India Institute of Medical Sciences, 4th floor, Room no.-4057, Ansari Nagar, New Delhi, 110029, India (e-mail: drdvki2776@gmail.com).

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Study of Sigmoid Sinus Variations in the Temporal Bone by Micro Dissection and its Classification - A Cadaveric Study

Abstract

Introduction

Objective

Methods

Results

Conclusions