Indmedica Home | About Indmedica | Medical Jobs | Advertise On Indmedica
Search Indmedica Web
Indmedica - India's premier medical portal

Journal of the Anatomical Society of India

Mastoid Canals and Grooves in Adult Japanese Human Skulls

Author(s): Singh M., Mishra A and *Nagashima M.

Vol. 53, No. 2 (2004-07 - 2004-12)

Institute of Medical Sciences, B.H.U., Varanasi, *Saitama Medical School, Saitama - 350-0495, Japan.

Abstract:

This study was undertaken to observe the frequency of mastoid canals and grooves in adult Japanese human skulls and analyse its sexwise distribution. 435 dry adult Japanese skulls of known age and sex from the osteology section of the department of Anatomy, Hokkaido University School of Medicine, Sapporo, Japan were selected and observed for the present study. The mastoid regions of dry skulls were observed for the presence of mastoid canals and grooves, if any. A hair bristle was passed through the canal for its confirmation and then the length was measured. Length of mastoid groove was not measured. The Mastoid canals were present in 52.4% of the total 435 skulls observed either bilaterally or unilaterally. Sexwise, their frequency was more in males (55%) than in females (34.5%). Mastoid grooves were present in 13.56% of the total skulls (435) observed. Sexwise their frequency was more in females (23.6%) than in males (12.1%). The blood vessels running on mastoid region were more frequently covered in a bony canal in males than in females where they were more frequently uncovered. The percentage frequency of these canals and grooves was higher in Japanese population than in Indian population.

Key words: Blood vessels, Hair bristle, Japanese human skulls, Mastoid Canal, Mastoid groove.

Introduction:

Mastoid canals and grooves have not been reported earlier except one report from Indian subjects by Choudhry et al (1996). But there also, the authors have reported only about the mastoid canals, not about the grooves. Moreover, they have not mentioned sexwise frequency of distribution which has been reported in this study. In addition, the frequency of mastoid grooves has also been reported. These vascular canals and grooves of varying calibre and length, just posterior to the mastoid process have not been described in any of the text-books of Anatomy, though these are of significant importance for neurosurgeons and otolaryngologists because they contain an arterial branch of occipital artery with its accompanying vein which is liable to injury resulting into severe bleeding.

Material and Methods:

A total of 435 dry adult human Japanese skulls of known sex and age were observed for the presence of Mastoid canals and grooves in mastoid region in the Department of Anatomy, Hokkaido University School of Medicine, Sapporo, Japan. Only those skulls which had canals patent to hair bristles were considered as possessing mastoid canals. The length of the canal was measured by passing bristles. The diameter of the canal could not be measured.

The grooves unaccompanied with canals only were taken into account. Their length was not measured, only their presence was noted.

Results:

A total of 435 dried human skulls (870 mastoid female skulls. Out of the total skulls observed [435], the regions) were observed for the presence of canals with mastoid canals were present in 228 [54.4%] skulls, either intact [Fig. 1] or perforated lateral wall or grooves [Fig. bilaterally or unilaterally. On sexwise analysis, it was 2] on the outer surface of mastoid processes, located present in 55% of male and 34.5% of female skulls posterior and parallel to the petrosquamous suture, [Table-I]. Bilateral canals were present in 109 [25.05%] anterior to the occipitomastoid suture and anteroinferior skulls. Out of these 103 [27.10%] belonged to males to the asterion. Out of these 380 were male and 55 were and 6 (10.9%) belonged to females. In 49 [11.26%] skulls [42 M, 7F] the canals were present on only right side. Out of these; in 7 skulls [5 M, 2F], grooves were present on left side at the corresponding site. In rest of the skulls, there was neither groove nor canal on left side at the corresponding site. In 70 (16.09%) skulls (64 M, 6 F) the mastoid canals were present on left side only. Out of these, in 13 skulls, grooves were present on right side at the corresponding site. Thus in 25.05% of the total skulls observed the mastoid canals were present bilaterally, in 11.26% they were present on right side only and in 16.09% they were present on left side only [Table I]. In 1.6% there was canal on right side only and groove on left side, and in 2.9% there was canal on left side and groove on right side. On sexwise analysis, in males bilateral presence of the mastoid canals was maximum (27.10%) followed by its presence on left side [16.8%] and then on right side (11.05%). In case of females, its right sided presence was maximum followed by its bilateral and left sided presence. But, when compared to the males, the percentage of bilateral presence of the canals was much reduced [10.9%], followed by left sided presence [10.9%] though its right side sided presence was slightly higher. [Table-1]

Fig. 1. A Mastoid Canal [probe passed].

Missing Image

Fig. 2. A shallow Mastoid Groove

Missing Image

Table I : Distribution of canals in the mastoid region.

Sex No. of Skulls Bilateral Right Left Total Rt Canal
Lt. groove
Lt. Canal
Rt groove
No. % No. % No. % No. % No. % No. %
Total 435 109 25.05 49 11.26 70 16.09 228 52.40 7.0 1.60 13.0 2.9
Male 380 103 27.10 42 11.05 64 16.80 209 55.0 5.0 1.3 13.0 2.9
Female 55 6 10.90 7 12.72 6 10.90 19 34.50 2.0 3.6 0 0

Table II : Distribution of mastoid grooves.

Sex No.of Skulls Bilateral Right Left Total
No. % No. % No. % No. %
Total 435 21.1 4.8 20.0 4.5 18.0 4.13 59 13.56
Male 380 15.0 3.9 17.0 4.4 14.0 3.60 46 12.10
Female 55 6.0 10.9 3.0 5.4 4.0 7.20 13 23.6

Table - III: Distribution of canals / grooves in total mastoid regions (435x2).

Sex No. Mastoid Canals Mastoid Grooves
Right Left Total Right Left Total
No. % No. % No. % No. % No. % No. %
Total 870 158 18.16 179 20.5 337 38.70 41 4.7 39 4.4 80 9.19
Male 760 145 19 167 21.9 312 41.05 32 4.2 29 3.8 61 8.62
Female 110 13 11.80 12 10.9 25 22.70 9 8.18 10 9.0 19 17.2

Table - IV: Size of the mastoid canals in mm

Sex Right Side (mm) Left side (mm)
1- 10 11- 21 1-10 11- 21
No. % No. % No. % No. %
Total 85 53.70 73 16.20 114 63.60 65 36.30
Male 76 48.10 69 43.60 106 59.20 61 36.52
Female 9 69.20 4 30.70 8 66.60 4 33.30

Observation of the corresponding mastoid regions for grooves only, either shallow (Fig.2) or deep revealed its presence in 13.56% (59) skulls. On sexwise analysis it was present in 12.10% (48) in males and 23.6% (13) in females. Bilateral presence of grooves was observed in 4.8% (21) skulls [15 M, 6 F] unilateral right sided grooves in 4.5% (20) skulls [17 m, 3 F] and left sided grooves in 4.13% (18) skulls [14 M, 4 F] (Table-II). In the specimens with unilateral groove, the contralateral mastoid region contained neither any groove nor any canal. Presence of right sided groove associated with left sided canals was observed in 13 male skulls only, whereas left sided groove associated with right sided canal was observed in 5 male and 2 female skulls. (Table1)

Thus out of the total mastoid regions studied (870), canals were present in 38.7% (337) of the regions. On sidewise analysis, right-sided canal was present in 18.16% and left sided canal was present in 20.5% of the regions. On sexwise analysis on right side it was present in 19% of male mastoid regions and in 11.8% of female mastoid regions. On left side, it was present in 21.9% male regions and 10.9% female regions[Table-III].

Out of the total mastoid regions (870), mastoid grooves were present in 9.19% [80], mastoid regions of the skulls. On sexwise analysis it was present in 8.62% [61] in males and 17.2% [19] in females. On sidewise analysis it was present on right side in 4.7% [41] in total, out of which it was present in 4.2% [32] in males and in 8.18% [9] in females. On left side, it was present in 4.4% [39] in total, out of which it was present in 3.8% [29] in males and 9.0% [10] in females. The measurement of length of mastoid canals showed variation of length, from 1-10 mm in 53.7% [85] and 1121 mm in 16.2% [73] of the canals on right side. On sexwise analysis the length varied from 1-10 mm in 48.1% of male canals [76] and 69.2% [9] of the female canals and 11-21 mm in 43.6% [69] of male and 30.7% [4] of the female canals. On left side, the length of mastoid canals varied from 1-10 mm in 63.6% [114] and 11-21 in 36.3% [65] out of the total canals measured. On sexwise analysis, it varied from 1-10 mm in 59.2% [106] of male canals and 66.6 [8] of female canals. In 36.5% [61] of male canals and 33.3% [4] of female canals, it measured 11-21 mm. Discussion:

This study proves that the mastoid canals are not confined to Indian population only as described earlier by Choudhry et al (1996). Moreover, the percentage frequency of mastoid canals in Japanese population is observed to be higher than in Indian population indicating that these features might be present throughout the world with varying percentage, though still further reports are awaited in this direction.

In the present study, no dissection was done to confirm the arterial branch traversing the observed canal or groove. Hollinshed (1982) and Schaeffer (1953) have described an ascending or auricular branch of the occipital artery, Gardener et al (1963) reported inconstant presence of this artery and Warwick et al (1995) reported two occipital branches of the occipital artery at this site. Ludman (1988), Romanes (1981) and Glasscock and Shambaugh (1990) reported an occipital branch of the posterior auricular artery whereas Choudhry et al (1996) reported a sizeable branch of the occipital artery and its accompanying vein at this site.

The reason of the development of mastoid canal whether it contains an auricular or occipital branch of the occipital artery or occipital branch of the posterior auricular artery, seems to be developmental as the ossifying squamotemporal bone buries it Wright (1987) and Choudhry et al (1996). The squamous part which arises in mesenchyme at 8 weeks of fetal life, forms the anterosuperior part. This squamous plate grows posteriorly and covers a large area of the lateral surface of petromastoid bone which develops from the cartilaginous epiotic centre at 5-6 months of fetal life and forms the posteroinferior part by 1 year of age Schaeffer (1953). The extent of this overlapping may be responsible for the presence of varying length of mastoid canals in this region enclosing partially the artery which runs in close contact with bone. The same factor may be responsible for the presence of exposed artery in those specimens where only grooves are observed.

In case of males, the frequency of mastoid canals was more (55.0%) in males than in females (34.5%). On sidewise analysis also, it remained higher in males bilaterally as well as on left side also than in females. On right side it was negligible lower (11.05%) than in females (12.72%). But the frequency of mastoid grooves was higher in females (23.6%) than in males (12.10%). Sidewise also it remained higher.

Therefore, the frequency of exposed artery in this region is more in females than in males where as the frequency of covered artery is more in males than in females.

Since the presence of artery with its accompanying vein in this region (anterior to the mastoid emissary formina) is liable to injury as it may be undetected, it is necessary for surgeons operating in this area to be aware of this vascular arrangement to avoid troublesome bleeding with more care in case of females. The importance of structures in the mastoid area has increased due to the increasing use of the transtemporal route for surgical procedures involving access to structures in the posterior fossa and the mastoid air system by neurosurgeons and otolaryngologists.

References:

  1. Choudhry R, Raheja S, Gaur U, Anand C : Mastoid canals in adult human skulls. Journal of Anatomy 1996; 188 : 217-219.
  2. Gardner E, Gray DJ, O'Rahilly R : Anatomy. Philadelphia, WB Saunders; 1963, p.16.
  3. Glasscock ME and Shambaugh GE : Surgery of the ear. Philadelphia, WB Saunders; 1990, p.224.
  4. Hollinshead WH : Anatomy for surgeons. New York, Harper and Row; 1982, p.183.
  5. Ludman H : Mawson's diseases of the ear. London; Edward Arnold; 1988, p20.
  6. Romanes GJ : Cunningham's text book of Anatomy, (12th edn.). London, Oxford University Press; 1981, p.902-903.
  7. Schaeffer JP : Morris' Human Anatomy, (11th edn.) New York, Blakiston; 1953, p.166.
  8. Warwick PL, Williams R, Dyson M and Bannister LH : Gray's Anatomy, (38th edn.) Edinburgh, Churchill Livingstone; p.591.
  9. Wright D Scott-Brown's otolaryngology : 5th edn. London, Butterworths; 1987, p.10.
Access free medical resources from Wiley-Blackwell now!

About Indmedica - Conditions of Usage - Advertise On Indmedica - Contact Us

Copyright © 2005 Indmedica