Rev. Chil. Anat., 20(3):281-284, 2002.

 

DETERMINATION OF THE LENGTH AND PENETRATION OF THE
DEEP TEMPORAL NERVES IN THE TEMPORAL MUSCLE

DETERMINACIÓN DE LA LONGUITUD Y PUNTO DE PENETRACIÓN DE LOS
NERVIOS TEMPORALES PROFUNDOS EN EL MÚSCULO TEMPORAL

^*Nilton Alves & ^**Fernando Fusari Bento de Lima

ALVES, N. & DE LIMA, F. F. B. Determination of the length and penetration point of the deep temporal nerves in the temporal muscle. Rev. Chil. Anat., 20(3):281-284, 2002.

SUMMARY: The aim of this study is to determinate the length and the penetration point of the deep temporal nerves, in the temporal muscles. Twenty hemiheads were used, fastened in formaldehyde, of adult individuals of both sexes and of different ethnic groups. Initially, it was made the dissection of the pieces by an endocranian access, once located the nerves, we passed to the measurement of the same ones, using as reference the oval foramen and the penetration point of the nerve in the muscle. For the determination of the penetration point it was used two pre-certain lines that delimited the area of penetration of the deep temporal nerves in the temporal muscle. The first, is a line that tangency the zigomatic arch, and the second, is a line parallel to the one that tangency the supra orbital margin. The penetration points were projected to the surface with the aid of a pin, and compared with the references already described giving, subsidies for an eventual approach of those structures for the surface. The results obtained were analyzed in a statistics, where we could conclude that there are no significant differences in the length among the right and left sides. Althought we could conclude that the medium length of anterior deep temporal nerve is 27,26mm; of the medium deep temporal nerve is of 26,02mm; and of the posterior deep temporal is of 24,93mm. We could conclude too that in most of cases the deep temporal nerves penetrates in the inferior third of the temporal muscle.

KEY WORDS: 1. Temporal muscle; 2. Deep temporal nerves. 

INTRODUCTION

The trigeminal nerve is a mixed nerve, in other words, it has a sensitive root and a motor root, being the sensitive component considerably larger. It emerges from the central nervous system between the bridge and the medium cerebellar peduncles and goes previously until the trigeminal impression (petrous part of temporal bone) where is the trigeminal ganglion.

Starting from the trigeminal ganglion, we have the three branches or divisions of the trigeminal nerve: ophthalmic nerve, maxillary nerve and mandibular nerve.

The mandibular nerve is the only one of the three branches of the trigeminal nerve that carries motor fibers, that are distributed to the mastication muscles (masseter muscle, temporal muscle, medial pterygoid muscle and lateral pterygoid muscle), mylohyoid muscle and anterior belly of the digastric muscle.

This study was accomplished with the intention to find the length and penetration point of the deep temporal nerves in the temporal muscle.

MATERIAL AND METHOD

This study used 20 hemiheads (11 right and 9 side), fixed in formaldehyde, of adult individuals of both sexes and of different ethnic groups. They belong to the Universidade Metodista de São Paulo (UMESP) and the Escola Paulista de Medicina (UNIFESP), São Paulo, Brazil.

First it was accomplished the dissection and afterwards of the temporal nerves were measured. The dissection was accomplished in the following way: firstly it was made transversal cut in the head, passing upper to the supra-orbital margin and removing the cranium cap. After having removed the encephalon, we started the dissection of the area to be studied, the access place being the floor of the medium fossa of the skull. Once located the trigeminal nerve, it was tonged and the dura-mater from the area was removed, preserving the mandibular branch (Fig. 1). Soon afterwards, we made the ostectomy of the area, using chisels and hammer, preserving the periosteum of the roof of the infratemporal fossa.

We continued with the removal of the periosteum and location of the deep temporal nerves, upper to the lateral pterygoid muscle. The deep temporal nerves were dissected until the penetration in the temporal muscle (Fig. 2) and so, we measured its length.

To the determination of the length of these nerves, the oval foramen was used as a proximal reference, and as distal reference, the penetration point of the nerve in the muscle.

The measurement of the nerves was accomplished with the aid of a Mitutoyo digital caliper. Precision: 0,01mm.

A delimeted area was fixed by a horizontal plan that was tangent to the superior margin of the zygomatic arch and for another plane parallel to this tangent to the supra-orbital margin. This area was measured in an upper-lower way, and it was divided in third parts: superior, medium and inferior.

The points of penetration of the nerves in the muscles were projected to the surface, with the aid of pins fixed exactly in these points until they appeared in the lateral face of the temporal muscle. Than it was measured the distance between the pin and the two described lines, so that we can determine in which third of the muscle the nerve penetrates.

The obtained results were statistically analyzed using the t-test: two samples supposing equivalent variances.

Fig. 1. Medium fossa of the skull, after the removal the dura-mater. In the tweezers we observe the mandibular nerve, (1) the trigeminal ganglion.

Fig. 2. Final aspect of the dissection, endocranial view. 1. Anterior deep temporal nerve; 2. Medium deep temporal nerve; 3. Posterior deep temporal nerve.

RESULTS

Having analyzed the results regarding the anterior deep temporal nerve, we concluded that in 75% of the cases this nerve penetrates in the inferior third of the temporal muscle. In 10% of the cases the anterior deep temporal nerve enters in the medium third of the temporal muscle, without noticing any case where this nerve penetrates in the superior third of the temporal muscle (Table I). In 15% of the cases the superficial course of this nerve beat in the medial face of the zygomatic arch, locating therefore, below to the pre-certain measurement area (Table I). The length of the anterior deep temporal nerve has varied between: 16,66mm and 34,54mm, with a length average of 27,26mm.

Using the t-test, at a level of significance of 5% alfa=0,05, we observed that Stat-t (calculated t) is smaller than the t-critical bi-caudal (t-fixed), we can affirm then, that there are no significant differences between the length of the right and left anterior deep temporal nerves (Table II).

Analysing the data regarding the medium deep temporal nerve we could see that in 25% of the cases this nerve penetrates in the inferior third of the temporal muscle, in 10% of the cases the superficial cases of this nerve beat in the medial face of the zygomatic arch, locating therefore, below to the pré-certain measurement area (Table I). In 65% of the cases this nerve was absent, considered by some authors an anatomical variation (Table I). During the dissection of this nerve, some anatomical variations were observed, example:

the origin that in some cases occurs in the previous trunk and in other cases in the subsequent trunk of the mandibular nerve or sometimes the origin is in the mandibular nerve. The length of the medium deep temporal nerve has varied between: 21,93mm and 34,38mm; with a length average of 26,02mm.

When the t-test was applied, at the level of significance 5% alfa=0,05, we observed that Stat-t (calculated t) is larger than the t-critical bi-caudal (t-fixed), then, we can affirm that in this case significant difference exists among the length of the right and left medium deep temporal nerves, considering that on average the right medium deep temporal nerves is larger than the left medium deep temporal nerve (Table III). But the sample were too small to provide us a precise conclusion.

Having analyzed the data regarding the posterior deep temporal nerve, we observed that in 35% of the cases the penetration point of this nerve is in the inferior third of the temporal muscle, there was not any occurrence in which the penetration point of the nerve in this muscle was in the superior or medium third, in 20% of the cases the superficial course of this nerve beat in the medial face of the zygomatic arch, and in 25% of the cases the superficial course of this nerve was below to the zygomatic arch (Table I). Therefore, in both situations the superficial course was out of the pre determinated mensurement area. We could also observe, that in 20% of the cases this nerve absent (Table I). The length of this nerve varied between: 18,15mm and 31,25mm; with a length average of 24,93mm.

After the t-test was applied, at the level of significance of 5% alfa=0,05, we observed that Stat-t (calculated t) is smaller than the t-critical bi-caudal (t-fixed), therefore, we can affirm that there are no significant difference among the length of the posterior deep temporal right and left nerves, (Table IV).

Table I: Penetration point of the deep temporal nerves.

	Anterior		Medium		Posterior
	F	%	F	%	F	%
Penetration point in the superior third	0	0	0	0	0	0
Penetration point in the medium third	2	10	0	0	0	0
Penetration point in the inferior third	15	75	5	25	7	35
Projection in the medial face of zygomatic arch	3	15	2	10	4	20
Projection lower to the zygomatic arch	0	0	0	0	5	25
Absent	0	0	13	65	4	20
Total	20	100	20	100	20	100

Table II. T-test: Two samples supposing equivalent variances for the anterior deep temporal nerve.
	Length of the right	Length of the left
Average	26,51	27,99
Variance	24,05	29,90
Standard desviation	4,90	5,47
Observations	11	9
Grouped variance	26,65
Hypothesis of the
average difference	0
Gl	18
Stat t	-0,63
t critic bi-caudal	2,10

Table III. T-test: Two samples supposing equivalent variances for the medium deep temporal nerve.
	Length of the right	Length of the left
Average	29,34	22,68
Variance	15,44	0,45
Standard deviation	3,92	0,67
Observations	4	3
Grouped variance	9,44
Hypothesis of the
average difference	0
Gl	5
Stat t	2,83
t critic bi-caudal	2,57

Table IV. T-test: Two samples supposing equivalent variances for the posterior deep temporal nerve.
	Length of the right	Length of the left
Average	25,23	24,62
Variance	22,21	20,98
Standard deviation	4,71	4,58
Observations	9	7
Grouped variance	21,68
Hypothesis of the
average difference	0
Gl	14
Stat t	0,26
t critic bi-caudal	2,14

DISCUSSION

Regarding the anterior deep temporal nerve, we could observe in our research that, in 75% of the cases this nerve penetrates in the inferior third part of the temporal muscle, its medium length was 27,26mm and also that it is a branch of the buccal nerve (Balli et al., 1932; Cunningham, 1976; Dubrul, 1991; Goss, 1988; Gray,1989; Hollinshead, 1980; Hollinshead, 1961; Júnior, 1973; Testut et al., 1954 and Warwick et al., 1979). However we should emphasize that the same emerges upper to the lateral pterygoid muscle.

Regarding the posterior deep temporal nerve, we observed that in 35% of the cases it enter into the inferior third of temporal muscle, having an average length of 24,93mm. We also observed that in all cases it originates with the masseteric nerve, which is in agreement with the authors that affirm that it usually happens (Balli et al.; Goss; Gray; Shaefer, 1961; Testut and Warwick).

Considering the medium deep temporal nerve we not only observe that in 25% of the cases it penetrates in the inferior third of the temporal muscle, and that its medium length is 26,02mm, but also noticed that in 65% of the cases it is absent. This allows us to agree with the authors that affirm that the deep temporal nerves are three (Balli), and also with that affirm that they are two (Gray; Schaffer and Warwick).

RESUMEN: El objetivo de este estudio fue determinar la longitud y el punto de penetración de los nervios temporales profundos, en los músculos temporales. Se usaron 20 hemi-cabezas formolizadas, de individuos adultos de ambos sexos y de diferentes grupos étnicos. La disección se efectuó por vía endocraneana y una vez localizados los nervios temporales, fueron medidos usando como referencia el foramen oval y el punto de penetración del nervio en el músculo temporal. Para la determinación del punto de penetración se usaron dos líneas que delimitaban el área de penetración de los nervios temporales profundos en el músculo temporal. Los puntos de penetración se proyectaron a la superficie. Los resultados obtenidos fueron analizados estadísticamente, no encontrándose diferencias significativas entre ambos lados. La longitud promedio de los nervios temporales profundos fue: anterior 27,26mm; medio 26,02mm; posterior 24,93mm. Concluimos que en la mayoría de los casos los nervios temporales profundos penetran en el tercio inferior del músculo temporal.

PALABRAS CLAVE: 1. Músculo temporal; 2. Nervios temporales profundos.

REFERENCES

Balli, R.; Bertelli, D.; Bruni, A. C.; Granelli, L.; Luna, E.; Pinde, N.; Sala, L.; Salvi, G. &Versari, R. Trattato di Anatomia Umana. 2ª ed. Milano, Vallardi, 1932.

Cunningham, D. Manual de anatomia prática. 13ª ed. São Paulo, Atheneu, 1976.

Dubrul, E. L. Anatomia Oral. 8ª ed. São Paulo, Artes Médicas, 1991.

Goss, C. M. Gray Anatomia. 29ª ed. Rio de Janeiro: Guanabara Koogan, 1988.

Gray, H. Gray's Anatomy. 37ª ed. London, Livingstone, 1989.

Hollinshead, W. H. Livro texto de anatomia humana. São Paulo, Harbra, 1980.

Hollinshead, W. H. Anatomy for surgeons. New York, Hoeber Harper Book, 1961.

Júnior, S. F .S. Sinopses Anatómicas. Rio de Janeiro, Atheneu, 1973.

Schaeffer, J. P. Morris' Human Anatomy. A Complete Systematic Treatix. 10ª ed. Philadelphia, Blankinston, 1961.

Testut, L. & Latarjet, A.  Tratado de Anatomía Humana.  9ª ed.  Barcelona, Salvat, 1954.  V. 3.

Warwick, R. & Williams, P. L. Gray Anatomia. 35ª ed. Rio de Janeiro, Guanabara Koogan, 1979. V. 2.

Dirección para correspondencia:
Prof. Dr. Nilton Alves
UNESP- Universidade Estadual Paulista
Julio de Mesquita Filho
Câmpus de Araraquara- SP
Rua Humaitá,1680
CEP 148011-903
BRASIL

Email: nilton@foar.unesp.br

Recibido : 04-06-2001
Aceptado: 27-09-2002

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^* Department of Morphology,  Faculdade de Odontologia,  Universidade Estadual Paulista Júlio de Mesquita Filho - UNESP, Brasil.

^**Department of Anatomy, Instituto de Ciências Biomedicas, Universidade de São Paulo - USP, Brasil.