Exploring surgical outcomes of intra-axial posterior fossa tumor surgeries: A retrospective study of 126 patients in a single center over 5 years

Objective

This study aims to assess the results, complications, and surgical outcomes of intra-axial posterior fossa tumor surgeries conducted at Mahatma Gandhi Hospital, Jaipur.

Study design

This summary describes a retrospective study conducted on intra-axial posterior fossa tumors operated in the Department of Neurosurgery at Mahatma Gandhi Hospital, Jaipur, India, between January 2018 and April 2023. The study excluded cases without complete clinical data, as well as cerebello pontine (CP) angle tumors and brain stem lesions.

Inclusion and exclusion criteria

This summary describes a retrospective study conducted on intra-axial posterior fossa tumors operated in the Department of Neurosurgery at Mahatma Gandhi Hospital, Jaipur, India, between January 2018 and April 2023. The study excluded cases without complete clinical data, as well as CP angle tumors and brain stem lesions.

Key aspects of the study include:

• Data collection: Information on age, sex, clinical symptoms, radiological findings, surgical techniques, and histopathological results were gathered

• Pre-operative assessment: Clinical examination and imaging results (CT and MRI) were recorded from patient case sheets

• Post-operative evaluation: Clinical examination findings were documented until patient discharge. Tumor histopathology was retrieved from departmental records

• Surgical outcome assessment: Outcomes were categorized as excellent, good, or poor based on clinical and radiological evaluations at discharge.

  • Excellent: Total/near-total tumor excision without neurological deficits or complications

  • Good: Subtotal excision with no or reversible neurological deficits or total/near-total excision with reversible deficits

  • Poor: Subtotal or total/near-total excision with irreversible deficits, bedridden or comatose states, or death.

This classification provided a clear framework to evaluate the effectiveness of surgical interventions and patient recovery in this specific clinical setting.

Patient population

Out of 126 patients, 82 patients were males and 44 were females. The mean age was 30.8 ± 20.26 years, and they ranged from 1 to 83 years.

Pre-operative workup

This study included a detailed preoperative assessment for all patients, involving routine physical examinations and comprehensive neurological evaluations. Each case utilized a specialized neurosurgical sheet to ensure that all necessary clinical details were documented. Both CT and MRI scans, with and without contrast enhancement, were performed on all patients before surgery to obtain thorough imaging data. This rigorous pre-operative protocol was essential for planning surgical interventions and evaluating patient conditions accurately.

Operative note

All surgeries were performed under general anesthesia with patients in the prone position, utilizing an operating microscope and microsurgical instruments for precision. A midline or paramidline suboccipital approach was used for optimal access to the posterior fossa. The primary goal was complete tumor excision, but a conservative approach was taken in cases where the tumor involved the brainstem or critical vessels and nerves to prevent neurological damage.

General operative technique

The surgical protocol in this study emphasized precision and risk minimization. Key steps included:

• Patient Positioning: Patients were placed prone with thoracic and pelvic support, using the Mayfield system for head fixation (except for three children aged 2, 4, and 5 years)

• Skin Incision: A midline incision extended from the inion to the second cervical vertebra

• Muscle Dissection: Suboccipital and paracervical muscles were separated with diathermy

• Craniectomy: Adjusted for tumor size/location, including foramen magnum opening and atlas arch removal for craniocervical tumors

• Dural Incision: A Y-shaped incision provided optimal exposure

• Tumor Removal: Cortical incision exposed the tumor, which was removed using suction, piecemeal extraction, or ultrasonic aspiration, while carefully avoiding damage to the brainstem

• Closure: After hemostasis, the dura was closed watertight, with dural grafting as needed

• Post-operative Management: Malignant or residual cases were referred for further treatment, including Gamma Knife radiosurgery, chemotherapy, or radiotherapy.

This structured approach prioritized tumor resection while minimizing neurological risks.

Management of hydrocephalus

Preoperative shunting was performed in patients with compromised general condition and reduced consciousness caused by elevated intracranial pressure. Post-operative shunting was done if signs of increased intracranial pressure and hydrocephalus appeared after surgery.

Post-operative follow-up

Post-operative follow-up: An early CT scan was performed to detect any immediate complications. Patients were monitored clinically within the hospital initially, followed by outpatient visits to the neurosurgery clinic, with radiological follow-up extending over a 6-month period. CT ± MRI with contrast was conducted between the 3^rd and 6^th month after surgery. All intraoperative and post-operative complications were documented and reviewed to monitor for tumor recurrence.

The final outcome was evaluated as excellent, good, or poor 3 months after discharge.^[8]

Statistical analysis

Data analysis was carried out using Statistical Package for the Social Sciences version 20. Quantitative data were evaluated using the mean and standard deviation, while qualitative data were analyzed by frequency and percentage. Fisher’s exact test was applied to analyze qualitative data, with a P ≤ 0.05 considered statistically significant (*) and >0.05 considered statistically insignificant.

Age incidence

Patients were categorized into seven age groups, with the highest number of cases found in the 0–20-year age group. The mean age of the patients was 30.8 ± 20.3 years, with an age range of 1–83 years [Table 1].

Clinical presentation

The most common symptom was headache, occurring in 95 cases (75.4%). This was followed by vomiting in 86 cases (68.3%), ataxia in 65 cases (51.6%), and cranial nerve palsy in 8 cases (6.3%).

Management of hydrocephalus

Out of 53 patients with radiological evidence of hydrocephalus, 43 patients underwent a preoperative ventriculoperitoneal (VP) shunt. Post-operative shunt surgery was required in 10 patients, primarily those who experienced postoperative deterioration due to hydrocephalus, often following partial tumor removal. Table 2 shows the incidence of shunt insertion based on tumor pathology.

Histological distribution

The most common tumor type based on histopathology was astrocytoma, observed in 43 cases (34.1%). This was followed by medulloblastoma in 36 cases (28.6%), metastatic tumors in 13 cases (10.3%), and ependymoma in 9 cases (7.1%), which included variants such as ependymoma grade 2 (5 cases) and anaplastic ependymoma grade 3 (4 cases). Hemangioblastoma was identified in 9 cases (7.1%), epidermoid cysts in 7 cases (5.5%), lymphoma in 2 cases (1.6%) [Figures 1a-b and 2a-b and Table 1].

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Figure 1:

(a) Pre-operative radiological brain images with contrast for 7-year-old female of posterior fossa ependymoma grade 2: T1-weighted magnetic resonance imaging Contrast - Axial, sagittal, and coronal cuts. (b) Postoperative radiological brain images – computed tomography axial cuts.

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Figure 2:

(a) Preoperative radiological brain images with contrast for 70-year-old male (known case of VHL syndrome) with posterior fossa Hemangioblastoma: T1-weighted magnetic resonance imaging Contrast – Axial and coronal cuts. (b) Post-operative radiological brain images – computed tomography axial cuts.

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CT/MRI findings

Most intra-axial tumors originated from the midline, with some extending laterally. Medulloblastomas were predominantly hyperdense, while cerebellar astrocytomas appeared hypodense. Ependymomas were most commonly associated with calcifications. The fourth ventricle was displaced anteriorly in most cases of medulloblastoma, anterolaterally in cerebellar astrocytomas, metastases, epidermoid cysts, dermoid tumors, and lymphomas, and posteriorly in ependymomas and hemangioblastomas. Contrast injection revealed varying degrees of enhancement across all tumors. MRI provides better delineation of normal anatomy, the extent of space-occupying lesions, and the displacement of anatomical structures [Table 3].

Complications

The study identified CSF leakage ± pseudo-meningocele and mutism in 4 cases (3.1%), wound and chest infections in 3 cases (2.4%), and cranial nerve palsy and hemorrhage/hematoma in 2 cases (1.6%) [Table 1].

Surgical outcomes

The surgical outcomes in this study were categorized as excellent in 84 cases (66.7%), good in 34 cases (27%), and poor in 8 cases (6.3%).

Table 4 illustrates that pilocytic astrocytoma had the best outcomes, with 95.4% of cases classified as excellent and 2.3% as good. Hemangioblastoma followed, with 88.9% of cases having excellent outcomes and 11.1% having good outcomes. In contrast, gliomas had the worst outcomes, with 66.7% of cases classified as poor, followed by medulloblastomas with 11.1% poor outcomes. However, these differences were statistically insignificant.

Follow-up

During the follow-up period, recurrence was noted in 8 patients (6.3%), including 4 with medulloblastomas and one each with hemangioblastoma, pilocytic astrocytoma, anaplastic ependymoma, and glioma. In addition, 4 patients (3.2%) died within 6 months postoperatively: 2 with recurrent medulloblastomas and 1 each with glioma and anaplastic ependymoma.

Clinical features

In our study, patients with midline posterior fossa tumors primarily presented with headaches (75.4%) and vomiting (68.3%). Cerebellar signs were observed in 51.6% of patients, while lower cranial nerve palsies and focal neurological deficits were noted in 8 cases. Gait disturbances and truncal ataxia were also common, affecting 51.6% of the cohort. These findings align with previous studies by Jiang et al.,^[13] Shih and Smirniotopoulos,^[44] Sajjad et al.,^[26] and Roberti et al.,^[22] who similarly reported headache and vomiting as frequent symptoms. Muzumdar et al. also found that 75.3% of medulloblastoma patients presented with these symptoms.^[45]

Walker and Petronio identified headache, vomiting, and papilledema as the dominant symptoms,^[46] while Chang et al. noted headache, vomiting, and gait disturbance as the most common in patients with medulloblastoma, cerebellar astrocytoma, and ependymoma.^[47] Kalyani et al. reported headache and vomiting in 70.3% of patients, slightly lower than our findings (75.4% and 68.3%).^[23] However, motor deficits and cranial nerve palsies were more common in their study. Both studies showed similar prevalence of cerebellar signs.^[23]

Chang et al. found that most medulloblastomas were midline, with 8% extending laterally, compared to 5.6% in our study.^[47] For cerebellar astrocytomas and ependymomas, Chang et al. reported lateral extension in 26% and 21% of cases, while we found 39.5% of astrocytomas extending laterally. Kingsley observed calcifications in 44% of ependymomas, 12% of medulloblastomas, and 9% of cerebellar astrocytomas, with Chang et al. reporting higher rates for ependymomas (70%) and medulloblastomas (29%). In our study, calcifications were present in 11.1% of medulloblastomas and 44.4% of ependymomas.^[47,48]

Hydrocephalus occurred in 52.8% of medulloblastoma cases, 77.8% of ependymoma cases, and 30.2% of cerebellar astrocytoma cases.

Shunt surgery

In our study, shunt placement was performed in 19 medulloblastoma, 13 cerebellar astrocytoma, 6 ependymoma, 5 metastasis, and several other tumor cases. Pre-operative VP shunts were used in 43 patients, and 10 required post-operative shunts due to hydrocephalus from fourth ventricular obstruction. Schmidt reported that only 7% of midline posterior fossa tumor patients needed shunts,^[38,49-51] while our study showed a higher incidence, possibly due to late presentation. Kalyani et al. found 77% of patients required CSF drainage,^[23] compared to 42.1% in our study, while other studies reported 33–53% requiring shunts.^[3,51]

Definitive surgery

In our study, gross total or near-total resection was achieved in 108 patients (85.7%), with a residual lesion left in 18 patients (14.3%). This result aligns with findings from Cochrane, where near-total resection was similarly prevalent.^[25] However, other studies have reported less favorable outcomes, with nearly half of the patients undergoing subtotal resection.^[26]

Specifically, among the 36 cases of medulloblastoma, near-total excision was accomplished in 31 cases (86.1%), while subtotal excision was performed in 5 cases (13.9%). For cerebellar astrocytoma, total or near-total excision was achieved in 41 cases (95.3%) and subtotal excision in 2 cases (4.7%). In ependymoma cases, near-total excision was achieved in 6 patients (66.7%), with subtotal excision in 3 patients (33.3%). In glioma cases, subtotal excision was performed in 2 patients, while near-total excision was achieved in 1 patient. For metastatic tumors, gross total excision was achieved in 12 of 13 patients. All patients with dermoid and hemangioblastoma tumors had near-total excision. Out of 7 cases of epidermoid tumors and 4 cases of lymphoma, subtotal resection was achieved in 3 cases of epidermoid tumors and 2 cases of lymphoma.

Refaat et al. reported near-total excision in 92% of medulloblastoma cases, compared to 63.9% in our study, and near-total excision in 80% of ependymoma cases.^[52] Sutton reported that 73% of patients with cerebellar astrocytoma underwent total resection, while 27% had subtotal resection; our series achieved total resection in 95.3% and subtotal resection in 4.7% of cases.^[29]

In our study, the surgical outcomes were categorized as excellent in 84 cases (66.7%), good in 34 cases (27%), and poor in 8 cases (6.3%). Shaikh et al. reported that 77% of their patients had good outcomes, while 23% had poor outcomes, characterized by moderate disability or significant neurological deficits.^[53] Our study found the best outcomes in patients with astrocytoma (95.4% excellent) and hemangioblastoma (88.9% excellent), whereas gliomas had the worst outcomes (66.7% poor), followed by medulloblastomas (11.1% poor). In contrast, another study reported the best outcomes in ependymoma, then astrocytoma, with the worst outcomes in metastatic tumors, followed by medulloblastomas.^[53]

Recurrence occurred in 6.3% of patients in our study, with 4 cases of medulloblastoma and 1 case each of hemangioblastoma, pilocytic astrocytoma, anaplastic ependymoma, and glioma. Four patients (3.2%) expired. Shaikh et al. found a recurrence rate of 8.33%, with 2 cases of medulloblastoma and a mortality rate of 4.87%.^[53] Another study reported a 6.7% death rate.^[54]

The lower mortality and morbidity rates observed in our study may be attributed to advancements in surgical skills and state-of-the-art equipment available in modern neurosurgical centers. In contrast, surgeons in third-world countries often rely on their expertise without access to advanced tools and technology. Issues such as corruption and departmental policies can further exacerbate these challenges.

Our goal was to document and assess surgical outcomes, noting significant improvements over time. Enhanced familiarity with fourth ventricle anatomy, identification of critical structures such as the stria medullaris and PICA, and meticulous surgical techniques have contributed to better outcomes. These advances have resulted in higher rates of complete tumor excision, reduced mortality, fewer post-operative complications, and shorter intensive care unit stays. The evolution of surgical skills, learning from past experiences, and a commitment to preserving nerve tissue have all contributed to these improvements in patient outcomes.

Complications

Sawaya et al. categorized complications associated with craniotomy into three major types: neurological, regional, and systemic.^[55] In this study, we focused primarily on neurological and regional complications due to their higher frequency and direct association with surgical procedures. Our findings on post-operative complications such as transient cerebellar mutism, CSF leakage, wound infection, cranial nerve palsies, and meningitis are consistent with international studies.^[9,56,57]

CSF leakage is a common complication in cranial base surgery, typically presenting in the immediate post-operative period as clear fluid drainage from the nose, ear, or incision site. It accounts for 25.8% of all complications.^[55,58] In our study, incisional CSF leakage occurred in four patients (3.1%), often due to incomplete watertight dural closure.^[55] These cases were managed with additional stitches or repeated lumbar punctures or drainage.

Post-operative infections can range from superficial wound infections to more severe cases involving the bone flap or meninges. Some studies report a risk of 1–2% after supratentorial craniotomy.^[23,59,60] In our study, three cases (2.3%) of wound infection was documented. Extradural hematoma was observed in one patient with ependymoma and another with post-operative site hematoma.

Roberti et al.^[22] reported six cases of cerebellar mutism, a condition that predominantly affects children following the removal of posterior fossa tumors, though a few cases have also been documented in adults.^[61-63]

Cerebellar mutism, a rare complication mostly observed in children after posterior fossa tumor removal, was noted in four patients (3.1%) in our study, including two with medulloblastoma and two with ependymoma. All cases improved within 2–3 months. It is hypothesized that involvement of the dentate nucleus or disruption of the dentato-thalamo-cortical pathway may contribute to cerebellar mutism.^[64]

Cranial nerve complications are also frequently encountered following posterior fossa surgery. These deficits are often due to nerve retraction, direct injury, or compromised blood supply.^[61] In our study, three patients (10%) experienced cranial nerve palsy, specifically bulbar palsy. Injuries to lower cranial nerves IX, X, XI, and XII are rare, typically occurring in cases with large tumors that distort and displace the nerves.^[65,66]

Refaat et al.^[52] reported no intraoperative mortalities in their series of 25 cases, with 28% experiencing new post-operative neurological findings, including cerebellar mutism in two cases, post-operative hypotonia, facial palsy, bulbar palsy, and one case with both bulbar and facial palsy. One case of cerebellar mutism improved after 2 months, while the other persisted until the end of follow-up.

In terms of operative mortality for medulloblastoma, Cushing reported a rate of 33%, Park et al. 11.1%, Choux et al. 11.3%, Bloom 10%, and Varma et al. 12.5%. In contrast, our series reported no immediate post-operative mortality.^[57,67-70]