Small size craniotomy in endoscopic procedures: Technique and advantages.

BACKGROUND: Endoscopic procedure has been known as the method of choice for treatment of hydrocephalus with 8.5% complication rate. It seems that good dural closure, reconstructing bone defect and perfect pericranium suturing can decrease the wound complications. Here, we describe the method of minicraniotomy instead of the burr hole in the endoscopic procedure.
MATERIALS AND METHODS: A case-control study regarding the cranial opening for endoscopic surgery was done in 45 patients of <12 months age; 15 patients in case group for minicraniotomy and 30 infants as control group for burr hole. They were followed at least 1-month for complications including cerebrospinal fluid collection, wound dehiscence, wound infection, and meningitis. RESULT: Patients were between 1 and 11 months. Hydrocephalus (73%) was the most common etiology for endoscopic surgery in this series, followed by the arachnoid cyst (20%). Two patients in the case group and eight in control group developed complications. Meningitis was found in one infant in the control group. Despite less complications in the case group the difference between two cohorts was not statistically significant.
CONCLUSION: Minicraniotomy with providing more space in comparison to burr hole makes dural closure possible. It provides a small bone flap that can be replaced inside the bone defect. In spite of nonsignificant statistical difference between two groups regarding complication rate, we found less wound complications with minicraniotomy. Therefore, we advise this technique for the endoscopic procedure and propose minicraniotomy even in the older population to provide better dural opening, watertight dural closure and reconstructing the bone defect.

Introduction

Endoscopic third ventriculostomy (ETV) has been suggested as the method of choice for treatment of obstructive hydrocephalus like aqueductal stenosis[1] and fourth ventricle tumors.[23] Furthermore, the method has been used in nonobstructive hydrocephalus as an alternative treatment.[4567]

The overall complication rate is 8.5% ranging from 0% to 31.2% in different series.[89] Most complications can be categorized into three groups: (a) Intraoperative morbidities including bleeding, neuronal injury, hypotension and bradycardia,[101112] (b) immediate postoperative complications including cerebrospinal fluid (CSF) leakage, infection and hematoma,[131415] (c) late postoperative complications, including stoma occlusion and rarely sudden death.[1516] Thus, ongoing attempts continue to refine endoscopic techniques for a better outcome and less complication.

The conventional ETV is usually performed through a linear or curvilinear skin incision in the right frontal region, followed by a burr hole around the coronal suture and exposing the dura mater. After dural opening and cortical incision, neuroendoscope is introduced. At the end of procedure dura and cranium are unavoidably left open but subcutaneous tissue and the skin are closed as separate layers.[15] While CSF leakage is an uncommon complication in adult patients, it is a preoccupation for pediatric neurosurgeons performing the procedure, especially in babies with macrocephaly, large ventricles and thin scalp and skin.[71718]

Here, we describe the method of minicraniotomy that was done in children <1-year who underwent an endoscopic procedure. The complication rate of two techniques of bone opening (burr hole vs. minicraniotomy) was investigated.

Materials and Methods

A case–control study regarding the cranial opening for endoscopic surgery was conducted in Children's Hospital Medical Center between March 2012 and June 2013. Total 45 patients of <12 months age, with obstructive hydrocephalus, arachnoid cyst or brain tumor candidate for endoscopic intervention were included in this study. Fifteen patients in the case group were consecutively enrolled for endoscopic surgery via minicraniotomy. Thirty infants were considered as a control group where endoscopy was performed through a burr hole. Initially, patients with underlying diseases causing impaired wound healing including immunodeficiency diseases, and those with suspicion of metabolic disorders were excluded from the study.

In both groups, the patient was positioned in supine position. The limits of the anterior fontanel were defined for both groups. The skin was opened through a C-shape incision with a length of 3–4 cm at the lateral border of anterior fontanel, mostly in the right side to find access to frontal bone 1 cm in front of coronal suture and 2–2.5 cm far from midline. In the case group, lateral part of fontanel and the posterior edge of the frontal bone were exposed. Pericranium was cut with another C-shape incision with a direction exactly opposite to skin incision [Figure 1]. With a Penfield dissector, the posterior border of the frontal bone at the coronal suture was dissected and made free from dura. Using a sharp scissor, two parallel linear osteotomies were performed at the frontal bone and 15 mm distance from each other to make a small bone flap that was elevated anteriorly with a greenstick fracture. The bone flap remained attached to the bone from anterior border of craniotomy. Dura was opened with cruciate incision, and then corticotomy was performed. After performing the procedure, dural closure was done with nonabsorbable sutures. The osteoplastic flap was returned to its place, and the pericranium is sutured in a watertight manner. The skin was closed in two layers.

Figure 1

(a) The skin incision is usually C shape (vertical narrow arrow), the pericranium is cut C shape in a direction apposite to the direction of skin incision (horizontal thick arrow). The bone flap (asterisk) is elevated after dissecting the dura from coronal sutures and making two parallel osteotomies around the place of routine endoscopic procedure burr hole, 2–2.5 cm off midline and 1 cm in front of coronal suture, dura is opened with cruciate incision (b) and is sutured in a watertight manner. The bone flap is replaced at the location of bone defect

In the control group, the skin incision was made as case cohort but a burr hole was inserted to provide cranial opening necessary for the endoscopic approach. Dura was opened with cruciate incision but at the end of the procedure dura was not closed in watertight manner due to the small dimension of the burr hole and the place of the burr hole was filled with with surgicel. After that pericranium and skin were closed in the same way as case group. All surgeries were performed by a single surgeon. Patients were followed at least 1-month for complications including CSF collection, wound dehiscence, wound infection, CSF leakage, and meningitis. The statistical analysis was performed with SPSS version 20. The level of significance was defined as P < 0.05.

Results

Mean age of patients at case and control group was 5.2 m and 5.06 m respectively (ranging from 1 m to 11 m). Hydrocephalus (73%) was the most common etiology for endoscopic surgery in this series, followed by the arachnoid cyst (20%). Comparing case and control for age, sex and etiology two groups did not have significant statistical difference.

Among 15 patients in minicraniotomy Group 2 (13%) developed one kind of complications, compared to 8 out of 30 in the control group. Accordingly, the risk seems to be twice in burr hole group. Moreover, three out of eight complicated patients in burr hole group had more than one complication, so overall complication rate in this group was 11 (36%). Meningitis was found in one infant that was related to control group. However, the results showed minicraniotomy group had only two CSF collection, there is no infection or dehiscence or leakage at our experience with this method. Overall complication rate of minicraniotomy group is much less than of the burr hole group. In spite of less complication in minicraniotomy group this difference is not statistically significant [Table 1].

Table 1

Demographic information of minicraniotomy and burr hole groups and comparison of two groups for complications

Discussion

Endoscopic surgery is a treatment option for obstructive hydrocephalus[1] and an alternative method of management for nonobstructive hydrocephalus, which is associated with low morbidity and relatively high efficacy.[45] Thus, ongoing attempts continue to refine endoscopic techniques for better outcomes and complication avoidance.[192021]

One of the discomforting complications is related to the wound problem including dehiscence, CSF collection, and leakage. Some authors studied the ways that the wound complications can be diminished. Karabetsos et al., evaluated the effect of wound closure on CSF leakage and showed that saving the bony component and good closure of pericranium could decrease the risk of CSF leakage. Using fibrine glue had no effect on the complication rate in this study.[19] Costa Val showed that minicraniotomy with its specific paradigm significantly decreased CSF leakage and reported no CSF leakage in children <2 years of age which was different from his previous experience.[21]

A minicraniotomy could be easily done, and its advantages include correctly closing dura mater due to more space to access dura and restoring bone integrity.[20] The technique that we have used in our minicraniotomy group is no longer than burr hole method and can provide a flap that makes enough space to suture dura mater in watertight fashion and provides small bone flap that can be replaced after the procedure is done.

In spite of nonsignificant statistical difference between two techniques of bone opening in our study, minicraniotomy could decrease CSF leakage and subsequent infections. This result is supported with Costa Val study.[2021]

Since the main limitation of our study is small sample size, studies with more patients and larger sample size can be useful.

On the other hand, decreasing the wound complication is invaluable so we can propose small craniotomy in the endoscopic procedure at any age. In an age more than 1-year it is impossible to perform craniotomy with blunt dissection and scissor. Small craniotomy with maximum 2 cm diameter in this age is possible with one small burr hole and craniotomy. This provides a small bone flap with larger access to dura and subsequent dural repair. It can only add a few minutes to the time of surgery.

Conclusion

Minicraniotomy is a safe and rapid technique comparing to burr hole in young infants with a thin skull for finding access to intracranial contents during an endoscopic procedure. In spite of no significant statistical difference complication rate of minicraniotomy is lower than burr hole. We propose minicraniotomy in the older population to provide better dural opening and watertight closure due to larger space.