Long-term outcome after management of pilocytic astrocytoma in the posterior fossa in a pediatric population

Diagnostic accuracy of MRI without gadolinium for follow-up of pilocytic astrocytoma in the paediatric population

PURPOSE

Pilocytic astrocytoma is the most common glial tumour in the paediatric population with a long-term life expectancy after surgery. Long-term radiological follow-up with magnetic resonance imaging (MRI) is necessary to detect recurrence of tumour or growth of residual tumour. Established MRI protocols typically dictate post-gadolinium sequences despite concerns around the side-effect and safety concerns of gadolinium-based contrast agents. This study aims to investigate whether omission of gadolinium-enhanced sequences for the long term follow-up MRI for paediatric patients with pilocytic astrocytoma, maintains diagnostic accuracy assessing potential recurrence or growth of residual tumour.

METHODS

A retrospective review of follow-up MRI for 47 patients with histopathologically proven pilocytic astrocytoma was performed. Patients with optic pathway or suprasellar glioma were excluded from this study. All patients underwent surgery and had a minimum of 2 years of postoperative imaging for review. MRIs were chosen from most recent report of stability or at a time when growth/progression had been diagnosed. Two neuroradiologists and two paediatric neurosurgeons were randomly allocated a series of MRIs with gadolinium enhanced sequences removed, reviewers were blinded to the original report and subsequent treatment decisions. In addition, 30 paired MRI studies were randomly allocated to second review to test interobserver reliability. The reviewer responses were recorded and compared with the original report and analysed with respect to preserved diagnostic accuracy.

RESULTS

170 MRI scans were subject to review across 66 episodes of care for 47 patients. 22.7 % of patients experienced growth of residual tumour during the period of follow-up. The sensitivity of non-enhanced MRI for detection of growth was 82 % (95 %CI 64.40-92.12) with a specificity of 97.10 % (95 % CI 90.03-99.20). Accuracy was similar for both neuroradiologists and neurosurgeons (91.49 % vs. 94 %). Interobserver reliability was calculated using Cohen's Kappa co-efficient with a result of 0.792 showing substantial agreement. We also confirmed a statistically significant difference between gross total resection and sub-total resection and correlation with future growth (41 % vs. 0 %, n = 64, p = 0.001).

CONCLUSION

In paediatric patients who have undergone surgery for pilocytic astrocytoma, long term MRI follow-up without gadolinium-enhanced sequences maintains diagnostic accuracy compared with enhanced sequences. Omission of gadolinium-enhanced sequences may lead to decreased costs, duration of scans and anxiety around follow-up procedures.

Laser ablation of a fourth ventricular hamartoma causing medically refractory hemifacial spasms in a child: illustrative case

BACKGROUND

Hamartomas of the floor of the fourth ventricle (HFFVs) are rare lesions that cause a variety of symptoms, including hemifacial spasm (HFS). When symptomatic, these deep-seated lesions are traditionally treated via open surgical approaches. The authors describe successful laser interstitial thermal therapy (LITT) of an HFFV causing intractable HFS.

OBSERVATIONS

A healthy 19-month-old girl presented with right HFS, present since birth, occurring continuously throughout the day. MRI revealed a right HFFV. Following an unsuccessful trial of medical treatment and serial imaging to rule out a neoplastic process, she underwent LITT of the HFFV with immediate resolution of her facial spasm. She was discharged on postoperative day 1 with durability of her treatment at the 1-year follow-up and no neurological complications.

LESSONS

Laser ablation of HFFVs provides a well-tolerated, durable treatment option for HFFVs in pediatric patients. https://thejns.org/doi/10.3171/CASE24721.

Towards a Risk-Based Follow-Up Surveillance Imaging Schedule for Children and Adolescents with Low-Grade Glioma

The frequency and duration of imaging surveillance in children and adolescents with pediatric low-grade gliomas (pLGGs) aims for the early detection of recurrence or progression. Although surveillance of pLGGs is performed routinely, it is not yet standardized. The aim of the current review is to provide a comprehensive synthesis of published studies regarding the optimal frequency, intervals, and duration of surveillance. Several key influencing factors were identified (age, the extent of resection, the tumor location, the histological type, and specific molecular characteristics). However, the lack of consistent definitions of recurrence/progression and the extent of resection meant that it was not possible to perform a meta-analysis of the data from the 18 included articles. This review highlights the need for updating the definition of these terms for uniform and global use both in routine clinical practice as well as in upcoming trials. Thus, future studies on the heterogenous group of pLGGs will allow for the better tailoring of both the frequency and duration of imaging surveillance protocols in relevant settings.

Rare vermian pilocytic astrocytoma with recurrent spontaneous hemorrhage in the elderly: A case report and review of literature

Background

Pilocytic astrocytoma (PA) is a benign glial tumor predominately seen in pediatrics and early adolescence with associated overall good outcomes. Very few cases of elderly PA have been reported in the literature, and they are known to display unique anatomic, histologic, and genetic peculiarities distinct from pediatric disease. We report a rare case of vermian PA in an octogenarian with recurrent spontaneous intratumoral hemorrhage as a presenting symptom. Furthermore, a review of the literature on the peculiarities of PA in the elderly will be discussed.

Case Description

An 81-year-old woman presented with features suggestive of repeated posterior fossa hemorrhages characterized by headaches, diplopia, and alteration in sensorium occurring about 5 months apart. Brain neuroimaging showed a cerebellar vermian tumor with features suggestive of repeated intratumoral bleeding. She had an initial ventriculoperitoneal shunting for acute hydrocephalus and subsequently had a suboccipital craniotomy and subtotal tumor excision due to morbid adherence to the brainstem. The histologic diagnosis was PA with Ki-67 <1% and negative for isocitrate dehydrogenase-1. There was a slow but progressive clinical improvement, and she has remained symptom-free for 4 years on follow-up.

Conclusion

PA in the elderly is a rare disease with distinct histologic and genetic peculiarities. This case review showed one of the oldest cases of cerebellar vermian PA presenting with recurrent spontaneous intratumoral hemorrhage, an extremely rare occurrence in benign glioma. Although complete surgical excision is recommended, partial resection is advocated for morbidly adherent tumors. Overall prognosis is worse in elderly PA.

Pathological perspectives in pilocytic astrocytomas: Extent of resection as the sole critical factor for recurrence-free survival, and the challenge of evaluating conclusions derived from limited data

Introduction: Pilocytic astrocytoma (PA) is one of the most common primary intracranial neoplasms in childhood with an overall favorable prognosis. Despite decades of experience, there are still diagnostic and treatment challenges and unresolved issues regarding risk factors associated with recurrence, most often due to conclusions of publications with limited data. We analyzed 499 patients with PA diagnosed in a single institution over 30 years in order to provide answers to some of the unresolved issues. Materials and Methods: We identified pilocytic astrocytomas diagnosed at the University of California, San Francisco, between 1989 and 2019, confirmed the diagnoses using the WHO 2021 essential and desirable criteria, and performed a retrospective review of the demographic and clinical features of the patients and the radiological, pathologic and molecular features of the tumors. Results: Among the patients identified from pathology archives, 499 cases fulfilled the inclusion criteria. Median age at presentation was 12 years (range 3.5 months - 73 years) and the median follow-up was 78.5 months. Tumors were predominantly located in the posterior fossa (52.6%). There were six deaths, but there were confounding factors that prevented a clear association of death to tumor progression. Extent of resection was the only significant factor for recurrence-free survival. Recurrence-free survival time was 321.0 months for gross total resection, compared to 160.9 months for subtotal resection (log rank, p <0.001). Conclusion: Multivariate analysis was able to identify extent of resection as the only significant variable to influence recurrence-free survival. We did not find a statistically significant association between age, NF1 status, tumor location, molecular alterations, and outcome. Smaller series with apparently significant results may have suffered from limited sample size, limited variables, acceptance of univariate analysis findings as well as a larger p value for biological significance. PA still remains a predominantly surgical disease and every attempt should be made to achieve gross total resection since this appears to be the most reliable predictor of recurrence-free survival.