Posterior Fossa Craniotomy: Retrospective Analysis of 85 Patients

Introduction

Posterior fossa surgery is one of the important applications of neurosurgical practice. It differentiates from other regions of the brain in terms of the path of intervention and comprises important anatomical and neurovascular structures. Posterior fossa surgery is a routine procedure in the surgeries such as tumor, hemorrhage, cystic lesions that are located in posterior fossa and microvascular decompression. Traditional craniectomy procedure was performed during posterior fossa surgery in the past while craniotomy procedure started to be routine procedure in the last three decades.

Corresponding Author: Kadir Oktay, drkadiroktay@hotmail.com, Received: 18.03.2023, Accepted: 20.05.2024, Available Online Date: 30.06.2024 Cite this article as: Oktay K, Güzel E, Unal E, et al. Posterior Fossa Craniotomy: Retrospective Analysis of 85 Patients. J Cukurova Anesth Surg. 2024; 7(2): 85-9.

https://doi.org/10.36516/jocass.1454355 Copyright © 2024 This is an open access article distributed under the terms of the Creative Commons Attribution-Non-Commercial-No Derivatives License 4.0 (CC-BY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

Preservation of the bone structure is useful in many ways for the patient. There are studies in the literature examining osteoblastic craniotomies performed in posterior fossa interventions and comparing craniotomy and craniectomy procedures.1-4 Craniotomy is considered to be more advantageous. In this study, we aimed to evaluate 85 patients who underwent posterior fossa craniotomy for various pathologies.

Materials and methods

The records of 85 patients who underwent posterior fossa craniotomy for various pathologies between 2016-2021 were retrospectively reviewed. Patient records including age, gender, preoperative and postoperative neurological conditions, type and radiographic localization of their pathologies, applied surgical positions, closure methods of duramater, fixation methods of bone flaps, drain applications, hospitalization periods and postoperative complications were gathered.

(a) Preoperative axial and sagittal contrast-enhanced magnetic resonance images of 17-year-old female patient with 4. ventricle localized cavernoma. (b) Postoperative axial and sagittal contrast-enhanced magnetic resonance images of the same patient revealing total resection of the lesion.

Surgical planning was performed according to the location of the lesions. Contrast-enhanced magnetic resonance imaging of all of the patients was performed preoperatively (Figure 1). The patients were operated via sitting, prone and park bench positions. Duramater was closed with primary suturation in suitable patients while duraplasty with fascial graft was performed in inappropriate patients. However, watertight closure was ensured in all patients. Posterior fossa craniotomy procedures were applied to all patients (Figure 2). Craniotomy technique was applied to the patients with four burrholes from the safe areas and cutting with high-speed drill after dissection of the duramater under the bone. There was no dural or sinus injury in any of the patients except one. This patient had injury to the sigmoid sinus. However, the repair with the fascia graft and surgecell tamponade was performed and the patient was discharged without any problem. Bone flaps were fixed with silk in appropriate patients and by using miniplates in patients with defective or fragmented bone flaps. Jackson-pratt drains were placed in the required patients and drain was not placed in patients with good hemostasis. The patients were medicated with prophylactic antibiotherapy (ampicillin sulbactam) peroperatively and postoperatively for three days.

2.1. Statistical evaluation

SPSS software version 25.0 (IBM Corporation, Armonk, New York, USA) was used to analyze the variables. The Mann–Whitney U-test was applied with the Monte Carlo results to compare the categorical variables quantitatively. The quantitative variables were presented as the mean ± SD (standard deviation) and range (maximum-minimum) and the categorical variables as n (%). The variables were examined at a 95% confidence level, with p < 0.05 considered to indicate statistical significance.

Postoperative axial cranial computed tomography images of the same patient demonstrating suboccipital craniotomy for posterior fossa cavernoma excision

Results

3.1. Patient Profile

A total of 85 patients were included in the study. The mean age of the patients was 36.1 (2-82 years interval). 43 patients (50.5%) were female and 42 patients (49.5%) were male. 24 patients were in pediatric age group and 61 were adult. 63 patients had tumoral and 22 patients had non-tumoral pathologies. Of these 22 patients, 17 had trigeminal neuralgia, 2 had cerebellar abscess, 1 had hydatid cyst and 2 had traumatic epidural hematoma. In the tumoral group, 19 patients had medulloblastoma, 11 patients had epidermoid tumor, 8 patients had meningioma, 7 patients had schwannoma, 3 patients had hemangioblastoma, 4 patients had low grade glial tumor, 2 patients had high grade glial tumor, 2 patients had ependymoma and 1 patient had cavernoma (Table 1).

3.2. Patient Symptoms

The most common symptom was headache (84.5%). Other symptoms identified were cerebellar symptoms (68%), deterioration of consciousness (54%), nause (48%), cranial nerve dysfunction (34%) and hemiparesis (18.5%), respectively (Table 2).

3.3. Neuroimaging

The pathologies were extra-axial in 66 patients and intra-axial in 19 patients. Localization of the pathologies were; right cerebellopontine angle in 23 patients, left cerebellopontine angle in 21 patients, fourth ventricle in 20 patients, left cerebellum in 13 patients, right cerebellum in 6 patients and brainstem in 2 patients. According to the neuroimaging of the patients, hydrocephaly was detected in 22 patients. All patients with hydrocephalus had tumoral pathologies.

Demographic data of the patients in the study group

Clinical symptoms of the patients

Surgical procedures performed to the patients and postoperative complications

CSF: Cerebrospinal fluid,* Ventriculoperitoneal shunt was applied in 6 of these patients, 10 patient did not need ventriculoperitoneal shunt after tumor resection,

** Ventriculoperitoneal shunt was applied in 6 patients before the surgery and in 6 patients after external ventricular drainage.

3.4. Surgery

Posterior fossa craniotomies were applied to all patients. The operations of 48 patients was performed in the sitting position, 33 patients in the park bench position and 4 patients in the prone position. All craniotomies were performed using high speed drill. The duramater of the 68 patients were closed by primary suturation and the rest of the 17 patients underwent duraplasty with the fascia graft. Watertight closure was ensured with valsalva maneuver in all patients. Craniotomy flaps were fixed using only silk in 75 patients (Figure 3-4). In 10 patients, bone flaps were fixed with miniplates because they were fragmented or defective. During closure, Jackson-Pratt drains were placed in 74 patients. 11 patients did not have a drain due to good hemostasis (Table 3). The mean duration of hospitalization was 7.6 days (2-54 days interval).

At admission, hydrocephaly was present in 22 patients. Ventriculoperitoneal shunt was applied in 6 of these patients before tumor resection. The remaining 16 patients underwent external ventricular drainage. In 6 of these patients, ventriculoperitoneal shunt was needed and shunt was inserted after tumor resection. A total of 12 patients underwent ventriculoperitoneal shunting (Table 3).

Peroperative images of the same patient revealing suboccipital craniotomy fixation with silk sutures.

(a) Postoperative axial cranial computed tomography images of 32-year-old male patient who underwent microvascular decompression via left retrosigmoid craniotomy for trigeminal neuralgia. (b) Peroperative images of the same patient demonstrating left retrosigmoid craniotomy.

3.5. Complications

There were complications detected in 8 patients. During the follow-up, short term pseudomeningocele in 1 patient, long term pseudomeningocele in 1 patient, hematoma in 1 patient and co-existence of cerebrospinal fluid (CSF) leak from the wound and meningitis in 1 patient were detected. 3 patients died and 1 patient had vegetative status. The mortality rate was 3.5%. The patients who developed pseudomeningocele were treated with external lumbar subarachnoid drainage. The patient who developed hematoma in the operation region underwent re-operation and her hematoma was drained out. The patient who had co-existence of CSF leak from the wound and meningitis was treated with proper antibiotherapy and external lumbar subarachnoid drainage (Table 3).

Discussion

Traditionally, posterior fossa surgeries include craniectomy procedures. However, craniotomy procedures have been widely applied during the posterior fossa surgeries in the last three decades. This procedure was first described by Yaşargil and Fox5 in 1974. This craniotomy procedure is a technique applied by several burrholes using gigli wires. Ogilvy and Ojemann6 presented the craniotomy technique by using high-speed drill to the literature in 1993. In the following years, other techniques that have been modified using high-speed drill are also described in the literature7-10. This technique has been widely used in pediatric patients in previous periods and is currently used in both pediatric and adult age groups3.

There are some advantages of osteoclastic craniectomy technique used in traditional posterior fossa interventions. It is a more familiar technique by neurosurgeons in terms of application, it is easier to apply and can provide a wide field of view and it is easier to preserve duramater and vital neurovascular structures such as transverse and sigmoid sinuses during the procedure4. However, anatomical plane is impaired after resection of the occipital bone and the vital neurovascular structures in the posterior fossa remain vulnerable as a result of this technique1,4. In addition, posterior fossa craniectomies have been associated with an increase in surgical complications in the literature1-4.

Craniectomy procedures are thought to increase especially CSF leak in posterior fossa surgeries1-4. In cases where the skin integrity does not deteriorate, pseudomeningocele formation occurs, and in cases of deterioration, CSF leak and infections such as meningitis occur. In the study performed by Gnanalingham et al., three hypotheses were presented. The first one is the iatrogenic elimination of one of the anatomical layers to be breached before CSF can leak from the wound. The second is the bulging of the sutured duramater from the craniectomy defects with the increase in the intracranial pressure, such as coughs or strains, and dural sutures may tear out in these patients. The third is the formation of a dead space in the region where the muscles adhere together as a result of the resection of the bone, which is an adhesion area for the paravertebral muscles. Even in the small defects in the dura, this dead space is suitable for the formation of CSF collection and pseudomeningocele in the later stages1.

CSF leak may also be seen after posterior fossa craniotomies. However, CSF leak rates were found to be much lower in craniotomies in the studies presented in the literature1-4. In the study performed by Legnani et al.4, pseudomeningocele rates were 4% in craniotomy and 19.2% in craniectomy. CSF fistula rates were found to be 11.5% in craniectomy and 2% in craniotomy. Gnanalingham et al.1 presented similar results. In the craniotomy group, the rate of pseudomeningocele was 9% and CSF leak rate was 4%, while these rates were 23% and 27% in the craniectomy group. Because of the high CSF leak rates, wound infection and meningitis rates also increased in the craniectomy patients. In the present study, the rates of CSF leak and pseudomeningocele were 1% and 2% in patients who underwent craniotomy. Meningitis occured in one patient who had risk factors including CSF leak from the wound and long-term stay in the intensive care unit. This patient was treated with appropriate antibiotherapy and external lumbar subarachnoid drainage application and discharged with no problem.

Severe headache is another problem that may occur after craniectomy procedures in posterior fossa surgery. It is thought that this situation is caused by adhesion of the paravertebral muscles to the duramater and traction of the duramater during neck movements1,9,11. In accordance with this, we did not observe severe headache in the present craniotomy cohort. Another advantage of craniotomy is the ease of reoperations in the long term. Since the anatomical plane is impaired in patients undergoing craniectomy, the risk of damage to the duramater and vital neurovascular structures increases in recurrent surgeries1,4,9,12.

In previous periods, there was a thought that the craniectomy procedure would save the patients in emergency cases such as sudden brain swelling. However, it was found that this situation was not significant. No significant difference was found in the studies presented in the literature2-4. In order to avoid this situation, we think that total resection of the pathology in suitable patients, careful hemostasis, proper opening of subarachnoid cisterns and drainage of CSF should be performed.

In the literature, there are also publications in which the craniectomy defect is closed by using the autologous bone particles. Missori et al.13 presented a technique in which autologous bone fragments were covered with Surgicel (Ethicon, Johnson & Johnson) and the suboccipital craniectomy defect was reconstructed. In the study performed by Sheikh et al.10, reconstruction of the craniectomy defect was described by adding tissue glue to the autologous bone particles and covered with gel foam. There are also more studies about craniectomy defect reconstruction using tissue glue in the literature14-16. However, in such techniques, a certain fusion period is required for the bone flap and the strength of the bone in the early stages is not sufficient to be protective. In addition, we believe that craniotomy technique is more advantageous in terms of both susceptibility to infection and cost because it is applied without using a foreign body. Foreign material such as cranioplastic kit may cause artifacts in the neuroimaging of patients at later stages.

There are certain limitations of the present study. The most important limitation was the retrospective nature of the study. The absence of a craniectomy cohort in which we can compare the craniotomy group is another important limitation. The patient group was not classified as pediatric and adult, and a study group of total of 85 patients was composed.

Conclusion

Craniotomy procedure in posterior fossa surgery is a technique that has become widely used in recent years and replaces traditional craniectomy procedure. Although the application technique was thought to be more difficult in the early stages, it has been determined that the neurosurgeons could apply craniotomy procedure without damaging the patient with their modified techniques. It was difficult to apply with gigli wires in the past, but with the technology advancement, it was facilitated with the use of high-speed drill. It can be applied without any problem as a result of a certain learning period. In the present study, we present patients who underwent posterior fossa craniotomy with various pathologies. Posterior fossa craniotomy is a prominent technique with the low complication rates and high patient comfort in the postoperative period.

Statement of ethics

This study was conducted in accordance with the ethical principles of the Declaration of Helsinki and was approved by Cukurova University Clinical Research Ethics Committee (Date: 23/02/2024, decision number 22).

Conflict of interest statement

The authors declare that they have no financial conflict of interest with regard to the content of this report.

Funding source

The authors received no financial support for the research, authorship, and/or publication of this article.

Author Contributions

KO is the major contributor in writing the manuscript. KO, EG and AG are involved in the design and conception of the study. KO, EG, EU, MM, HS, and AG are involved in the collection of the data and the clinical follow-up of the patients. All authors read and approved the final version of the manuscript.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Originality Assertion

The authors have not submitted this article to another journal previously.