Preoperative 11 C-Methionine PET-MRI in Pediatric Infratentorial Tumors.

PURPOSE: MRI is the main imaging modality for pediatric brain tumors, but amino acid PET can provide additional information. Simultaneous PET-MRI acquisition allows to fully assess the tumor and lower the radiation exposure. Although symptomatic posterior fossa tumors are typically resected, the patient management is evolving and will benefit from an improved preoperative tumor characterization. We aimed to explore, in children with newly diagnosed posterior fossa tumor, the complementarity of the information provided by amino acid PET and MRI parameters and the correlation to histopathological results. PATIENTS AND METHODS: Children with a newly diagnosed posterior fossa tumor prospectively underwent a preoperative 11 C-methionine (MET) PET-MRI. Images were assessed visually and semiquantitatively. Using correlation, minimum apparent diffusion coefficient (ADC min ) and contrast enhancement were compared with MET SUV max . The diameter of the enhancing lesions was compared with metabolic tumoral volume. Lesions were classified according to the 2021 World Health Organization (WHO) classification. RESULTS: Ten children were included 4 pilocytic astrocytomas, 2 medulloblastomas, 1 ganglioglioma, 1 central nervous system embryonal tumor, and 1 schwannoma. All lesions showed visually increased MET uptake. A negative moderate correlation was found between ADC min and SUV max values ( r = -0.39). Mean SUV max was 3.8 (range, 3.3-4.2) in WHO grade 4 versus 2.5 (range, 1.7-3.0) in WHO grade 1 lesions. A positive moderate correlation was found between metabolic tumoral volume and diameter values ( r = 0.34). There was no correlation between SUV max and contrast enhancement intensity ( r = -0.15). CONCLUSIONS: Preoperative 11 C-MET PET and MRI could provide complementary information to characterize pediatric infratentorial tumors.

Craniopharyngioma and hypothalamic obesity in children.

BACKGROUND AND PURPOSE: Obesity is a major concern in children treated for craniopharyngioma and is caused by hypothalamic damage. The role of aggressive surgical removal has been questioned, leading some authors to recommend a minimalist approach. In order to test this hypothesis, we decided to study obesity in craniopharyngioma and the factors related to it. MATERIALS AND METHODS: We reviewed retrospectively our series of pediatric craniopharyngiomas operated since 1981. The body-mass index (BMI) was calculated for each patient pre- and at several intervals postoperatively and expressed as standard deviations (SD) adjusted for age and gender. RESULTS: We operated on 45 cases, which were followed up for a mean duration of 11.0 years. Initial resection was total in 25 cases (55.6%). No patient died because of surgery or tumor progression; two died with delay presumably because of endocrine failure. At last control, 28 patients (62%) had obesity (BMI over +2SD). Hypothalamic involvement was significantly correlated with preoperative and postoperative BMI. Subtotal tumor resection was significantly associated with obesity at last control. Reoperation for tumor recurrence was associated with a significantly higher BMI. CONCLUSIONS: Our results suggest that obesity results from hypothalamic lesions caused by the tumor rather than by surgery. The postoperative weight gain appears to result from the continued impact of preoperative hypothalamic damage. The high rate of tumor recurrence in children, with the risk of additional damage to the hypothalamus, incites us to recommend total resection whenever it appears safe during initial surgery.

Surgical resection of thalamic tumors in children: approaches and clinical results.

OBJECTIVES: Thalamic tumors are uncommon, and although gross total removal (GTR) is a prospective goal, its interest is debated because the thalamus constitutes a highly functional region. The relation of choice of the surgical approach, achievability of GTR, and operative morbidity to the anatomic location of the tumor has received little attention in the medical literature. MATERIALS AND METHODS: We reviewed retrospectively the cases of pediatric patients treated for thalamic tumor, with pre- and postoperative magnetic resonance imaging, and who were operated with the aim of maximal surgical removal. CONCLUSION: We reviewed 16 cases operated between 1992 and 2003. The clinical presentation was dominated by intracranial hypertension and hemiparesis. Fifteen children were operated through transcortical approaches: transfrontal in six cases, transparietal in six, and transtemporal in three. The remaining patient was operated through an infratemporal approach. All operations performed since 1998 used intraoperative neuronavigation. Complete or near-total resection was achieved in 11 cases; only subtotal resection was achieved in the remaining five cases. The most common postoperative morbidity was visual field defect. Hemiparesis was unchanged or improved in all the cases. Seven children died of tumor progression, in relation with high histological grade, and one died of acute hydrocephalus. The approach to thalamic tumors needs to be planned according to the location of critical neural structures. GTR of thalamic tumors in children bears acceptable morbidity and may even improve preoperative deficits. Surgery alone can be curative in low-grade tumors; in high-grade or infiltrating tumors, GTR is only part of the overall oncological management.