ANATOMICAL STUDY
Anatomical Study of Insula and Its Relationship With the Adjacent Structures Ye Zhang, MD,* Huan Wang, MD,† Ming Qian, MD,‡ Donghua Qian, PhD,§ and Dan Tong, PhD|| Introduction: Insular lobe is folded deep in the sylvian fissure, and the transsylvian transinsular approach is one of the most commonly used methods for lesions in the insula, basal ganglia, amygdala, and hippocampus. Hence, it is essential for surgeons to master a specific anatomic knowledge of the insula and its adjacent structures. This study aims to locate the insula, measure relevant parameters, and reduce the occurrence of surgical injury and postoperative complications. Patients and Methods: One hundred three individuals (53 males and 50 females) were selected randomly, and magnetic resonance imaging–based morphometric analysis was performed. We located the landmark and measured the parameters related to the transsylvian transinsular approach. The parameters and figures in the sagittal, coronal, and axial planes were used to illustrate the anatomical relationship between the insular lobe and its adjacent structures. Results: The length of the superior limiting sulcus (line A) was 52.05 ± 3.30 mm in the left and 51.56 ± 2.90 mm in the right. The length of the inferior limiting sulcus (line B) was 48.18 ± 3.01 mm in the left and 48.40 ± 3.34 mm in the right. The length of the anterior limiting sulcus (line C) was 22.64 ± 1.47 mm in the left and 22.50 ± 1.57 mm in the right. The length of the central insular sulcus (line D) was 31.36 ± 2.68 mm in the left and 31.52 ± 2.53 mm in the right. The distance from insular apex to brain surface through sylvian fissure (line E) was 19.26 ± 2.21 mm in the left and 19.36 ± 2.26 in the right. The distance from inferior limiting sulcus to the roof of temporal horn (line J) was 9.75 ± 1.38 mm in the left and 9.66 ± 1.18 mm in the right. The angle (θ), which was formed by line J and the vertical line via the inferior limiting sulcus (line I), was 30.51 ± 3.60 degrees in the left and 30.56 ± 3.11 degrees in the right. The distance from insular apex to the lateral side of putamen (line L) was 10.10 ± 1.59 mm in the left and 10.62 ± 1.39 mm in the right. The distance from insular apex to the middle of genu capsulae internae (line K) was 25.73 ± 1.02 mm in the left and 26.50 ± 1.15 mm in the right. Independent-samples t From the *Public Health School, †Norman Bethune Medical School, and ‡Prosthodontics Department of Stomatological Hospital, Jilin University; and Departments of §Respiration and ||Radiology, the first Affiliated Hospital of Jilin University, Changchun, Jilin, China. Received February 4, 2014. Accepted for publication April 20, 2014. Address correspondence and reprint requests to Dan Tong, PhD, No. 71 Xinmin Street, 130021, Changchun, Jilin Province, China; E-mail: [email protected] Y.Z. and H.W. contributed to the work equally and should be regarded as co–first authors. Financial support was provided by the Science and Technology Department of Jilin Province, China (20130522036JH). The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000001035
test showed no significant difference of the means between the right side and the left side. Conclusions: The statistics in our study can help to understand the complicated anatomical structures of insula and its surrounding area. Moreover, the parameters can increase the feasibility and safety of the surgery via transsylvian transinsular approach. Key Words: transsylvian transinsular approach, insula, insular apex, temporal stem, basal ganglia (J Craniofac Surg 2014;25: 1895–1897)
I
nsular lobe is a triangular structure located deep in the sylvian fissure, hidden between the temporal and the frontal lobe covered by opercula. Insula is delimited by the superior, inferior, and anterior limiting sulci, which makes it distinguished from surrounding structures. Central insular sulcus divides insula into 2 portions, the anterior insula and the posterior insula.1 Insula can be exposed by a dissection of the sylvian fissure. Under this circumstance, lesions deep seated in the brain can be resected via transsylvian transinsular approach. The approach was first used to facilitate the needle aspiration of hypertensive intracerebral hematoma,2 but now can be widely used to the resection of intrinsic insular tumors, selective amygdalohippocampectomy, and other deep-seated lesions. To facilitate surgery skills, it basically relies on an anatomical knowledge of insular lobe and its adjacent structures such as temporal stem and basal ganglia. However, the anatomical characteristics have not been quantified accurately and analyzed sufficiently by magnetic resonance imaging (MRI), which is widely used in the hospital. So, it is necessary to establish an anatomical database related to the transsylvian transinsular approach and apply it to clinical practice.
PATIENTS AND METHODS The whole-head MRI scanning data of individuals were collected in the First Hospital of Jilin University from January 2013 to December 2013 in accordance with ethical committee guidelines. Individuals were selected randomly, and samples with brain disease were excluded. The 103 selected samples consisted of 53 males TABLE 1. Landmarks Used in the Study Parameter Line A Line Line Line Line Line Line Line Line θ
B C D E I J K L
Definition Superior limiting sulcus Inferior limiting sulcus Anterior limiting sulcus Central insular sulcus The distance from insular apex to brain surface through sylvian fissure The vertical line via inferior limiting sulcus The distance from inferior limiting sulcus to the roof of temporal horn The distance from insular apex to the middle of genu capsulae internae The distance from insular apex to the lateral side of putamen The angle between lines I and J
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1895
Zhang et al
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
FIGURE 1. Restricted sagittal view of insula. Line A, superior limiting sulcus; line B, inferior limiting sulcus; line C, anterior limiting sulcus; line D, central insular sulcus.
and 50 females aged from 18 to 60 years, with an average age of 38.4 years. The 2 hemispheres were both measured in the sagittal, axial, and coronal planes by the same 3.0-T MRI machine. We could measure relevant data in any desired plane after multiplanar reconstruction. Parameters in the sagittal, axial, and coronal planes are listed in Table 1. T1-weighted images were obtained in the sagittal, axial, and coronal planes. Superior, inferior, anterior limiting sulcus and central insular sulcus were located and measured in the sagittal plane, which are shown in Figure 1. The level of 2 consecutive coronal planes is shown in Figure 2; lines E and J were measured in the 2 planes separately. After the insular apex was located in the coronal plane, the results of distance from insular apex to the middle of genu capsulae internae and from insular apex to the lateral side
FIGURE 3. Restricted axial view of insula and basal ganglia. F is the insular apex; G, the middle of genu capsulae internae; line K, the distance from insular apex to the middle of genu capsulae internae; line L, the distance from insular apex to the lateral side of putamen.
of putamen were accurately obtained in the axial plane, which are shown in Figure 3.
RESULTS The 4 sulci, lines A, B, C, and D, can be seen in Figure 1, and the results are listed in Table 2. In the 2 consecutive coronal planes, obvious locations of insular apex and temporal stem are shown in Figure 2; relevant parameters are listed in Tables 3 and 4. Insula has a close relationship with basal ganglia region, so we measured lines K and L to provide statistics for surgery via transsylvian transinsular approach, and the parameters are listed in Table 5.
DISCUSSION Transsylvian transinsular approach is widely applied in surgery of lesions in insula, basal ganglia, amygdala, and hippocampus. During the operation, surgeons are required to accurately TABLE 2. Statistics in the Sagittal Plane Parameter Side Line A Line B Line C FIGURE 2. Restricted coronal view of insula and its adjacent structures. A, At the level of insular apex. F is the insular apex; line E, the distance from insular apex to brain surface through sylvian fissure. B, At the level of temporal horn. G is the temporal horn; H, inferior limiting sulcus; line J, distance from G to H; line I, vertical line via H; θ, angle between lines I and J.
1896
Line D
Left Right Left Right Left Right Left Right
Mean, mm
SD, mm
Range, mm
95% Confidence Interval, mm
52.05 51.56 48.18 48.40 22.64 22.50 31.36 31.52
3.30 2.90 3.01 3.34 1.47 1.57 2.68 2.53
45.10–58.40 46.20–57.80 43.40–55.40 41.90–55.20 20.20–25.80 19.40–20.60 25.30–35.70 26.50–36.00
50.60–52.69 50.23–52.76 47.10–49.27 47.19–49.60 22.11–23.17 21.99–23.12 30.39–32.46 30.51–32.78
Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
TABLE 3. Statistics in the Coronal Plane Parameter Side Line E Line J
Left Right Left Right
Insula and Its Adjacent Structures
TABLE 5. Statistics in the Axial Plane
Mean, mm
SD, mm
Range, mm
95% Confidence Interval, mm
19.26 19.36 9.75 9.66
2.21 2.26 1.38 1.18
15.80–23.40 15.40–22.30 8.00–12.80 7.90–12.80
18.30–20.22 18.39–20.34 8.97–10.12 9.01–10.05
Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
distinguish landmarks related to the insula and its surrounding structures to decrease the risk of intraoperative damage and postoperative complications. Besides, it is necessary to summarize interindividual anatomical variations by a large cohort of statistics to minimize potential intraoperative damage. Hence, we attempt to identify the landmarks and measure the parameters related to transsylvian transinsular approach and then quantify accurately and analyze sufficiently. Transsylvian approach is a commonly used method that can avoid damage to the frontal, temporal, parietal cortex and render insula more superficial.3 Insula is a bridge of the region that can be explored through this approach. Insular apex, the part of insula nearest to the brain surface, is also a landmark during the sylvian fissure dissection. In our study, insular apex was located, and the distance from insular apex to brain surface through sylvian fissure was measured in the coronal plane (Fig. 2 and Table 3), which will lead to an appropriate and precise dissection through sylvian fissure. After the proximal sylvian fissure is open, the anterior insula is exposed, and the inferior limiting sulcus, another landmark, can be seen by retracting down the temporal operculum.4 Then, the inferior limiting sulcus needs to be incised if deep-seated lesions exist. The incision on the inferior limiting sulcus should be carefully chosen, because temporal stem is injured easily during this process. Temporal stem, which consists of white matter fiber, is a connecting line among the inferior limiting sulcus, limen insula, medial sylvian groove, and tail of caudate nucleus.5 In order to minimize the damage on temporal stem, operators must take into consideration the position, length, and angle of the incision. A study using volume rendering makes a conclusion that one-third point over the anterior side of inferior limiting sulcus is a good beginning of the operative route.6 Another report states that the most appropriate incision is generally 15 to 20 mm behind the limen insula. A mini-invasive and efficacious incision depends on a shorter incision and a thinner temporal stem.7 Hence, the preoperative evaluation on the thickness and the position of the temporal stem are helpful for protection. In our study, we identified points G and F (Fig. 2) and measured the length of line I and angle θ (Tables 3 and 4). Knowing specific parameters, the incision can be centered more precisely, and the exposure can be more limited to minimize the damage in the temporal stem. The distance from insular apex to genu capsulae internae and putamen in the axial plane was measured in our study to
TABLE 4. Statistics in the Coronal Plane Parameter
Side
Mean
SD
Range
95% Confidence Interval
θ
Left Right
30.51 30.56
3.60 3.11
22.80–35.90 24.50–35.00
28.66–31.84 28.98–31.74
The values are in degrees. Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
Parameter
Side
Mean, mm
SD, mm
Range, mm
95% CI, mm
Line L
Left Right Left Right
10.10 10.62 25.73 26.50
1.59 1.39 1.02 1.15
8.20–12.00 8.30–13.00 22.20–29.00 23.60–28.30
9.62–10.57 10.08–11.16 24.98–26.47 25.84–27.15
Line K
Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
explicit the relationship between the insula and the basal ganglia, which provides data support for surgeons and makes a benefit to operation safety. Spontaneous hypertensive intracerebral hemorrhage is one of the most serious forms of cerebrovascular disease. The basal ganglion is a high-risk area of hypertensive intracerebral hemorrhage, especially the putamen.8 Microsurgical treatment of hypertensive basal ganglia hemorrhage through transsylvian transinsular approach is much better than the traditional approach by treating the superior temporal gyrus. It can reduce injury during operation, if we choose the nearest place of insular cortex to separate lateral fissure.9 Insular apex is the nearest point from insula to brain surface. Thus, it is extremely important for neurosurgeons to have a firm understanding of the anatomical relationship between insular apex and basal ganglia. Although clinicians commonly use computed tomography to determine the location of the hematoma, it cannot provide the accurate distance from insular lobe to basal ganglia. So, we choose MRI to make our measurements more accurately, and the large quantities of samples with the statistical analysis may provide credible parameters for clinicians.
CONCLUSIONS The transsylvian transinsular approach is adopted in many cerebral diseases such as amygdalohippocampus lesions and hypertensive basal ganglia hemorrhage. Our measurements provide parameters of insula and its relationship with the adjacent structures, which may help neurosurgeons more precisely and vividly understand the transsylvian transinsular approach and reduce surgical injury and postoperative complications.
REFERENCES 1. Kalani MY, Kalani MA, Gwinn R, et al. Embryological development of the human insula and its implications for the spread and resection of insular gliomas. Neurosurg Focus 2009;27:E2 2. Suzuki J, Sato S. The new transinsular approach to the hypertensive intracerebral hematoma. Jpn J Surg 1972;2:47–52 3. Heffez DS. Stereotactic transsylvian, transinsular approach for deep-seated lesions. Surg Neurol 1997;48:113–124 4. Wang Feng, Sun Tao, XinGang Li, et al. Microsurgical and tractographic anatomical study of insular and transsylvian transinsular approach. Neurol Sci 2011;32:865–874 5. Chan-Young C, eong-Rok H, Gi-Taek Y, et al. Understanding of the temporal stem. J Korean Neurosurg 2010;47:365–369 6. Linpei J, Lue S, Wei S, et al. morphological study of transpterional-insula approach using volume rendering. J Craniofac Surg 2012;23:1893–1894 7. Nagata S, Sasaki T. The transsylvian trans-limen insular approach to the crural, ambient and interpeduncular cisterns. Acta Neurochir (Wien) 2005;147:863–869 8. Zhou HG, Zhang Y, Liu L, et al. Minimally invasive stereotactic puncture and thrombolysis therapy improves long-term outcome after acute intracerebral Hemorrhage. J Neurol 2011;258:661–669 9. Rajamani K, Barrett RJ, Carhuapoma JR. 10 most commonly asked questions about intracerebral and intraventricular hemorrhage. Neurologist 2003;9:214–219
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1897
Anatomical Study of Insula and Its Relationship With the Adjacent Structures Ye Zhang, MD,* Huan Wang, MD,† Ming Qian, MD,‡ Donghua Qian, PhD,§ and Dan Tong, PhD|| Introduction: Insular lobe is folded deep in the sylvian fissure, and the transsylvian transinsular approach is one of the most commonly used methods for lesions in the insula, basal ganglia, amygdala, and hippocampus. Hence, it is essential for surgeons to master a specific anatomic knowledge of the insula and its adjacent structures. This study aims to locate the insula, measure relevant parameters, and reduce the occurrence of surgical injury and postoperative complications. Patients and Methods: One hundred three individuals (53 males and 50 females) were selected randomly, and magnetic resonance imaging–based morphometric analysis was performed. We located the landmark and measured the parameters related to the transsylvian transinsular approach. The parameters and figures in the sagittal, coronal, and axial planes were used to illustrate the anatomical relationship between the insular lobe and its adjacent structures. Results: The length of the superior limiting sulcus (line A) was 52.05 ± 3.30 mm in the left and 51.56 ± 2.90 mm in the right. The length of the inferior limiting sulcus (line B) was 48.18 ± 3.01 mm in the left and 48.40 ± 3.34 mm in the right. The length of the anterior limiting sulcus (line C) was 22.64 ± 1.47 mm in the left and 22.50 ± 1.57 mm in the right. The length of the central insular sulcus (line D) was 31.36 ± 2.68 mm in the left and 31.52 ± 2.53 mm in the right. The distance from insular apex to brain surface through sylvian fissure (line E) was 19.26 ± 2.21 mm in the left and 19.36 ± 2.26 in the right. The distance from inferior limiting sulcus to the roof of temporal horn (line J) was 9.75 ± 1.38 mm in the left and 9.66 ± 1.18 mm in the right. The angle (θ), which was formed by line J and the vertical line via the inferior limiting sulcus (line I), was 30.51 ± 3.60 degrees in the left and 30.56 ± 3.11 degrees in the right. The distance from insular apex to the lateral side of putamen (line L) was 10.10 ± 1.59 mm in the left and 10.62 ± 1.39 mm in the right. The distance from insular apex to the middle of genu capsulae internae (line K) was 25.73 ± 1.02 mm in the left and 26.50 ± 1.15 mm in the right. Independent-samples t From the *Public Health School, †Norman Bethune Medical School, and ‡Prosthodontics Department of Stomatological Hospital, Jilin University; and Departments of §Respiration and ||Radiology, the first Affiliated Hospital of Jilin University, Changchun, Jilin, China. Received February 4, 2014. Accepted for publication April 20, 2014. Address correspondence and reprint requests to Dan Tong, PhD, No. 71 Xinmin Street, 130021, Changchun, Jilin Province, China; E-mail: [email protected] Y.Z. and H.W. contributed to the work equally and should be regarded as co–first authors. Financial support was provided by the Science and Technology Department of Jilin Province, China (20130522036JH). The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000001035
test showed no significant difference of the means between the right side and the left side. Conclusions: The statistics in our study can help to understand the complicated anatomical structures of insula and its surrounding area. Moreover, the parameters can increase the feasibility and safety of the surgery via transsylvian transinsular approach. Key Words: transsylvian transinsular approach, insula, insular apex, temporal stem, basal ganglia (J Craniofac Surg 2014;25: 1895–1897)
I
nsular lobe is a triangular structure located deep in the sylvian fissure, hidden between the temporal and the frontal lobe covered by opercula. Insula is delimited by the superior, inferior, and anterior limiting sulci, which makes it distinguished from surrounding structures. Central insular sulcus divides insula into 2 portions, the anterior insula and the posterior insula.1 Insula can be exposed by a dissection of the sylvian fissure. Under this circumstance, lesions deep seated in the brain can be resected via transsylvian transinsular approach. The approach was first used to facilitate the needle aspiration of hypertensive intracerebral hematoma,2 but now can be widely used to the resection of intrinsic insular tumors, selective amygdalohippocampectomy, and other deep-seated lesions. To facilitate surgery skills, it basically relies on an anatomical knowledge of insular lobe and its adjacent structures such as temporal stem and basal ganglia. However, the anatomical characteristics have not been quantified accurately and analyzed sufficiently by magnetic resonance imaging (MRI), which is widely used in the hospital. So, it is necessary to establish an anatomical database related to the transsylvian transinsular approach and apply it to clinical practice.
PATIENTS AND METHODS The whole-head MRI scanning data of individuals were collected in the First Hospital of Jilin University from January 2013 to December 2013 in accordance with ethical committee guidelines. Individuals were selected randomly, and samples with brain disease were excluded. The 103 selected samples consisted of 53 males TABLE 1. Landmarks Used in the Study Parameter Line A Line Line Line Line Line Line Line Line θ
B C D E I J K L
Definition Superior limiting sulcus Inferior limiting sulcus Anterior limiting sulcus Central insular sulcus The distance from insular apex to brain surface through sylvian fissure The vertical line via inferior limiting sulcus The distance from inferior limiting sulcus to the roof of temporal horn The distance from insular apex to the middle of genu capsulae internae The distance from insular apex to the lateral side of putamen The angle between lines I and J
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1895
Zhang et al
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
FIGURE 1. Restricted sagittal view of insula. Line A, superior limiting sulcus; line B, inferior limiting sulcus; line C, anterior limiting sulcus; line D, central insular sulcus.
and 50 females aged from 18 to 60 years, with an average age of 38.4 years. The 2 hemispheres were both measured in the sagittal, axial, and coronal planes by the same 3.0-T MRI machine. We could measure relevant data in any desired plane after multiplanar reconstruction. Parameters in the sagittal, axial, and coronal planes are listed in Table 1. T1-weighted images were obtained in the sagittal, axial, and coronal planes. Superior, inferior, anterior limiting sulcus and central insular sulcus were located and measured in the sagittal plane, which are shown in Figure 1. The level of 2 consecutive coronal planes is shown in Figure 2; lines E and J were measured in the 2 planes separately. After the insular apex was located in the coronal plane, the results of distance from insular apex to the middle of genu capsulae internae and from insular apex to the lateral side
FIGURE 3. Restricted axial view of insula and basal ganglia. F is the insular apex; G, the middle of genu capsulae internae; line K, the distance from insular apex to the middle of genu capsulae internae; line L, the distance from insular apex to the lateral side of putamen.
of putamen were accurately obtained in the axial plane, which are shown in Figure 3.
RESULTS The 4 sulci, lines A, B, C, and D, can be seen in Figure 1, and the results are listed in Table 2. In the 2 consecutive coronal planes, obvious locations of insular apex and temporal stem are shown in Figure 2; relevant parameters are listed in Tables 3 and 4. Insula has a close relationship with basal ganglia region, so we measured lines K and L to provide statistics for surgery via transsylvian transinsular approach, and the parameters are listed in Table 5.
DISCUSSION Transsylvian transinsular approach is widely applied in surgery of lesions in insula, basal ganglia, amygdala, and hippocampus. During the operation, surgeons are required to accurately TABLE 2. Statistics in the Sagittal Plane Parameter Side Line A Line B Line C FIGURE 2. Restricted coronal view of insula and its adjacent structures. A, At the level of insular apex. F is the insular apex; line E, the distance from insular apex to brain surface through sylvian fissure. B, At the level of temporal horn. G is the temporal horn; H, inferior limiting sulcus; line J, distance from G to H; line I, vertical line via H; θ, angle between lines I and J.
1896
Line D
Left Right Left Right Left Right Left Right
Mean, mm
SD, mm
Range, mm
95% Confidence Interval, mm
52.05 51.56 48.18 48.40 22.64 22.50 31.36 31.52
3.30 2.90 3.01 3.34 1.47 1.57 2.68 2.53
45.10–58.40 46.20–57.80 43.40–55.40 41.90–55.20 20.20–25.80 19.40–20.60 25.30–35.70 26.50–36.00
50.60–52.69 50.23–52.76 47.10–49.27 47.19–49.60 22.11–23.17 21.99–23.12 30.39–32.46 30.51–32.78
Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 5, September 2014
TABLE 3. Statistics in the Coronal Plane Parameter Side Line E Line J
Left Right Left Right
Insula and Its Adjacent Structures
TABLE 5. Statistics in the Axial Plane
Mean, mm
SD, mm
Range, mm
95% Confidence Interval, mm
19.26 19.36 9.75 9.66
2.21 2.26 1.38 1.18
15.80–23.40 15.40–22.30 8.00–12.80 7.90–12.80
18.30–20.22 18.39–20.34 8.97–10.12 9.01–10.05
Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
distinguish landmarks related to the insula and its surrounding structures to decrease the risk of intraoperative damage and postoperative complications. Besides, it is necessary to summarize interindividual anatomical variations by a large cohort of statistics to minimize potential intraoperative damage. Hence, we attempt to identify the landmarks and measure the parameters related to transsylvian transinsular approach and then quantify accurately and analyze sufficiently. Transsylvian approach is a commonly used method that can avoid damage to the frontal, temporal, parietal cortex and render insula more superficial.3 Insula is a bridge of the region that can be explored through this approach. Insular apex, the part of insula nearest to the brain surface, is also a landmark during the sylvian fissure dissection. In our study, insular apex was located, and the distance from insular apex to brain surface through sylvian fissure was measured in the coronal plane (Fig. 2 and Table 3), which will lead to an appropriate and precise dissection through sylvian fissure. After the proximal sylvian fissure is open, the anterior insula is exposed, and the inferior limiting sulcus, another landmark, can be seen by retracting down the temporal operculum.4 Then, the inferior limiting sulcus needs to be incised if deep-seated lesions exist. The incision on the inferior limiting sulcus should be carefully chosen, because temporal stem is injured easily during this process. Temporal stem, which consists of white matter fiber, is a connecting line among the inferior limiting sulcus, limen insula, medial sylvian groove, and tail of caudate nucleus.5 In order to minimize the damage on temporal stem, operators must take into consideration the position, length, and angle of the incision. A study using volume rendering makes a conclusion that one-third point over the anterior side of inferior limiting sulcus is a good beginning of the operative route.6 Another report states that the most appropriate incision is generally 15 to 20 mm behind the limen insula. A mini-invasive and efficacious incision depends on a shorter incision and a thinner temporal stem.7 Hence, the preoperative evaluation on the thickness and the position of the temporal stem are helpful for protection. In our study, we identified points G and F (Fig. 2) and measured the length of line I and angle θ (Tables 3 and 4). Knowing specific parameters, the incision can be centered more precisely, and the exposure can be more limited to minimize the damage in the temporal stem. The distance from insular apex to genu capsulae internae and putamen in the axial plane was measured in our study to
TABLE 4. Statistics in the Coronal Plane Parameter
Side
Mean
SD
Range
95% Confidence Interval
θ
Left Right
30.51 30.56
3.60 3.11
22.80–35.90 24.50–35.00
28.66–31.84 28.98–31.74
The values are in degrees. Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
Parameter
Side
Mean, mm
SD, mm
Range, mm
95% CI, mm
Line L
Left Right Left Right
10.10 10.62 25.73 26.50
1.59 1.39 1.02 1.15
8.20–12.00 8.30–13.00 22.20–29.00 23.60–28.30
9.62–10.57 10.08–11.16 24.98–26.47 25.84–27.15
Line K
Independent-samples t test showed no significant difference of the means between the right side and the left side (P > 0.05).
explicit the relationship between the insula and the basal ganglia, which provides data support for surgeons and makes a benefit to operation safety. Spontaneous hypertensive intracerebral hemorrhage is one of the most serious forms of cerebrovascular disease. The basal ganglion is a high-risk area of hypertensive intracerebral hemorrhage, especially the putamen.8 Microsurgical treatment of hypertensive basal ganglia hemorrhage through transsylvian transinsular approach is much better than the traditional approach by treating the superior temporal gyrus. It can reduce injury during operation, if we choose the nearest place of insular cortex to separate lateral fissure.9 Insular apex is the nearest point from insula to brain surface. Thus, it is extremely important for neurosurgeons to have a firm understanding of the anatomical relationship between insular apex and basal ganglia. Although clinicians commonly use computed tomography to determine the location of the hematoma, it cannot provide the accurate distance from insular lobe to basal ganglia. So, we choose MRI to make our measurements more accurately, and the large quantities of samples with the statistical analysis may provide credible parameters for clinicians.
CONCLUSIONS The transsylvian transinsular approach is adopted in many cerebral diseases such as amygdalohippocampus lesions and hypertensive basal ganglia hemorrhage. Our measurements provide parameters of insula and its relationship with the adjacent structures, which may help neurosurgeons more precisely and vividly understand the transsylvian transinsular approach and reduce surgical injury and postoperative complications.
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© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
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