Review of current surgical disclosures about technical surgery
The septum pellucidum (SP) is a translucent structure placed in the midline. It is part of the limbic system and is connected with the amygdala, habenula, and brainstem reticular formation [12]. The SP is composed of two parts: The upper SP contains only fiber tracts and the lower part called septum Verum (anterior to the foramen of Monro (FOM) and above the rostrum of the corpus callosum(CC)) which contains various nuclei including the septal nuclei, the diagonal band of Broca, the bed nucleus of the anterior commissure and the bed nucleus of the stria terminalis [13] The SP contains no arteries but one to three veins draining in the thalamostriate vein, with an asymmetric distribution in greater than 50% cases. In most cases, the large septal veins are located anterior to the foramen of Monro (3,4,5)
Nowadays, there is a constant controversy about the technical specifications for endoscopic septostomy. The first sticking point is the position of the patient's burr hole to access the lateral ventricle. Most authors advocate performing a single 1 cm precoronal drill, 2 or 3 cm from the midline, to get a trajectory more perpendicular to the septum pellucidum [10], [13] However, Tamburrini et al. consider a standard precoronal burr hole to be disadvantageous, arguing that it does not allow a sufficient view of the septal anatomy, making it difficult to perforate the septum. Therefore, they propose to make a more lateral frontal horn approach to a standard Kocher burr hole (1 cm precoronal, 3–5 cm from midline) [8]. Oertel et al. recommend an even farther lateral burr hole, up to 7 cm lateral to the midline and slightly anterior to the coronal suture. If a simultaneous ETV is planned, they recommend placing the burr hole not far than 4 cm lateral to the midline to allow a straight approach to the floor of the third ventricle [15] In our series we carried out a single precoronal burr hole of 1 cm and 3 cm away from the midline.
Entering the smaller or larger lateral ventricular cavity is another issue [8], [16], [17]. There is opposition among several authors, while some defend the approach by the smallest to avoid the decrease in the pressure gradient between the enlarged and normal ventricle, with the possibility of affecting the permeability of the septostomy [17]. In the situation of the contralateral slit ventricle, Tamburrini et al. prefer to enter the affected lateral ventricle with the aid of navigation to minimize the risk of injury to the contralateral thalamus when carrying out septostomy [8]. In contrast, other studies prefer to approach the largest ventricle due to its ease (even without neuronavigation) and greater workspace [10], [15]. In our series, we executed the septostomy, accessing the widest ventricle and use of neuronavigation in 8 patients (27.5%) when anatomical distortion was evidenced. Neuronavigation helps show the required depth and target point when anatomical orientation is lacking. The successful combination of frameless neuronavigation with neuroendoscopy has been previously reported [18], [19]. Rohde et al. found that neuronavigation was beneficial in 52.7% of septostomy cases performed with tumor biopsies, by allowing better anatomical orientation despite distortion caused by tumor growth [20]. According to Oertel et al., a septostomy can be carried out without neuronavigation, but they mention two situations in which it would be useful. The first situation is when we need to calculate the ideal approach for septostomy if it is combined with tumor biopsy or ETV, and the second is when the septum pellucidum is pushed contralateral with possible adherence to the contralateral thalamus causing a thalamic lesion with fenestrations [15].
The ideal site to fenestrate the septum pellucidum is not uniformly described in the literature [10], [11], [15]. Schroder et al. mention that the area of fenestration depends on the individual anatomy [16]. The septum pellucidum is divided into a frontal segment, which is the part anterior to the foramen of Monro, and an atrial segment, which consists of the part posterior to the foramen of Monro. In the frontal segment, there is a triangular avascular area delimited by the inferior septal vein, the floor of the frontal horn, and the corpus callosum. This triangular area is sufficiently translucent to allow the visualization of the contralateral part of the septum pellucidum and it is described as safe for fenestration. The recommended point site corresponds approximately 1.0 cm superior and 2.0 cm anterior to the superior margin of the foramen of Monro, also used by Aldana et al. [10] and Vinas et al. [12]. Furthermore, there are two other avascular areas located in the posterior atrial segment. One avascular area is between the superior septal vein and the posterior margin of septum pellucidum and another avascular area is identified in the atrial segment between the two septal veins, but Mohammad et al. considered that both of these areas are inconsistent in their size and shape [14]. However, Oertel et al. carried out the fenestration of 5 to 10 mm posterior to the foramen of Monro [15]. Hamada and Tamburrini et al. performed the fenestration between the anterior and the posterior septal vein [8], [11]. Finally, in contrast, we did the fenestration in the anterior avascular area, perforating layer by layer until creating a 5–10 mm stoma, using a number 4 Fogarty catheter, bipolar coagulation, and tweezers.
Role of SPT in the treatment of UVH/BVH.
There is currently a debate on several surgical procedures to manage UVH/BVH in the pediatric population. There are two therapeutic procedures and strategies to treat them, either single or combined. First, the ventriculoperitoneal shunt (VPS) is usually considered the simplest method, although higher rates of complications and revisions have been reported, especially in infants [4]–[7]. Second, more recent neuroendoscopic procedures alone or combined have been proposed as Septostomy (SPT) and/or Neuroendoscopic foraminal plasty of the foramen of Monro (NEFPFMO) [8].
Few published reports have addressed the results of SPT among other endoscopic procedures and only eight series deal with the technical aspects of this procedure [10], [11], [15], [16], [21], [22]. At the moment, our report is the third-longest in the literature after Aldana and Oertel et al. [10], [15]. Concerning all the series (n = 8), cases are described with a range of age between 5 months to 44 ages, and up to half of the series (n = 4) have included the pediatric population (Table 3). In the same way, surgical management in four series was SPT alone [10], [17], [21], [23], Schroeder et al. only combined procedures [16], and three series both single and combined [11], [15], [22]. In our series, half of the patients were managed with a unique surgical procedure, while the other half with combined procedures. Of these viable combinations, Gabb et al. described an experience with 75% of SPT plus ETV and 25% SPT plus VPS, meanwhile, Oertel et al. mixed 88% of SPT plus ETV and 12% SPT plus VPS, Oi et al. described a case of SPT plus NEPFMO and also Hamada presented one case with SPT plus VPS [11], [15], [16], [22]. These findings were like to our study, in which an SPT plus VPS was reported in almost half of the patients. In the overall series, Aldana reported the longest follow-up period with a mean of 31 months [10]. Interestingly, our study could reach a mean of 46 months. Hayashi reported a reoperation proportion in half of the patients, while Oertel and Aldana reported a proportion of one-third and Hamada only 10% of cases [10], [11], [15]. Our report reached a reoperation in almost one-quarter of patients.
Table 3
Septostomy series reported in the literature
Details/Author
|
|
Heilman and Cohen
|
Gaab and Schroeder
|
Oi et al.
|
Hayashi et al.
|
Gangemi et al.
|
Aldana et al.
|
Hamada et al.
|
Oertel et al.
|
Present series
|
Year of publication
|
|
1991
|
1999
|
1999
|
2000
|
2002
|
2003
|
2003
|
2009
|
-
|
Number of patients
|
|
2
|
4
|
5
|
4
|
5
|
32
|
20
|
30
|
29
|
Age group
|
Pediatric
|
X
|
-
|
-
|
X
|
X
|
X
|
-
|
-
|
X
|
Adult
|
-
|
X
|
X
|
X
|
X
|
-
|
X
|
X
|
-
|
Average age
|
|
7 months
|
33 years
|
7.6 years
|
-
|
11 years
|
5 months
|
44 years
|
32 months
|
73 months
|
Etiology subgroups
|
Oncological
|
1
|
4
|
-
|
-
|
-
|
6
|
-
|
19
|
14
|
Congenital
|
-
|
-
|
-
|
-
|
-
|
4
|
-
|
-
|
7
|
Secondary
|
-
|
-
|
-
|
4
|
-
|
16
|
15
|
6
|
8
|
Others
|
1
|
-
|
-
|
-
|
-
|
6
|
5
|
5
|
-
|
Clinic signs and symptoms
|
High-pressure symptoms
|
2
|
2
|
-
|
-
|
-
|
-
|
-
|
23
|
22
|
|
Long-standing hydrocephalus
|
-
|
2
|
-
|
-
|
5
|
-
|
-
|
7
|
7
|
Previously implanted VPS
|
|
2
|
-
|
-
|
2
|
3
|
-
|
9
|
1
|
9
|
Septostomy
|
|
1
|
4
|
5
|
4
|
4
|
32
|
20
|
30
|
29
|
Characteristics of the procedures
|
Sole
|
2
|
-
|
4
|
4
|
5
|
32
|
9
|
1
|
8
|
|
Combined
|
-
|
4
|
1
|
-
|
-
|
-
|
11
|
2
|
21
|
Additional surgical procedure
|
VPS
|
-
|
0
|
-
|
-
|
-
|
-
|
11
|
4
|
16
|
|
ETV
|
-
|
3
|
-
|
-
|
-
|
-
|
-
|
26
|
-
|
|
NEFPFMO
|
-
|
-
|
1
|
-
|
-
|
-
|
-
|
-
|
2
|
Improvement
|
Clinical
|
2
|
3
|
5
|
2
|
5
|
-
|
-
|
26
|
22
|
|
Radiological
|
2
|
4
|
3
|
2
|
5
|
17
|
-
|
23
|
-
|
Reoperation
|
|
-
|
-
|
-
|
2
|
-
|
10
|
20
|
10
|
7
|
Complications
|
|
-
|
1 dead
|
-
|
-
|
-
|
4 (1 intraventricular hemorrhage. 1 meningitis. 1 VPS infection. 1 skin infection)
|
-
|
-
|
-
|
Follow-up (months)
|
|
8
|
10
|
-
|
-
|
-
|
31
|
-
|
16
|
46
|
In conclusion, the surgical management of UVH and BVH has still some disclosure points to be reviewed. However, SPT and NEFPFMO seem to be secure, non-traumatic, and efficient procedures. Larger pediatric population series have to be analyzed to establish clinical care guidelines.