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Advances in neuroimaging in patients with epilepsy

Elysa Widjaja and Charles Raybaud

Intractable seizures can have a devastating effect on the development of a child. In children with intractable epilepsy that is refractory to medication, surgical treatment may be needed. Magnetic resonance imaging is an essential neuroimaging tool to assist in the identification of an epileptogenic substrate. The interpretation of MR images should be done in the context of clinical knowledge of the seizure symptomatology and electroencephalographic findings. Quantitative processing of structural MR data and advanced MR imaging such as diffusion tensor imaging and MR spectroscopy have the potential to identify subtle lesions that may otherwise have been missed. In addition to lesion localization, identification of eloquent cortex and white matter tracts are also an essential component of epilepsy surgery workup. Functional MR imaging maps the sensorimotor cortex and also lateralizes language. Diffusion tensor imaging tractography can be used to map the corticospinal tracts and the optic radiations. In addition to MR imaging, magnetoencephalography and nuclear medicine studies such as PET and SPECT scanning may be used to lateralize seizure focus when clinical, electrophysiological, and structural MR imaging findings are discordant.

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An angiographic study of meningiomas of the posterior fossa

Georges M. Salamon, André Combalbert, Charles Raybaud, and Jorge Gonzalez

✓ The meningeal vasculature of the posterior cranial fossa was studied on injected normal anatomical specimens and in angiograms of patients with posterior fossa meningiomas. The correlated results indicate that the dura anterior to the foramen magnum is supplied by meningeal vessels from the carotid siphon, the ascending pharyngeal and middle meningeal arteries. The dura posterior to the foramen magnum is supplied primarily by the occipital artery and secondarily by the vertebral artery.

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Surgical treatment of tentorial arteriovenous malformations draining into the subarachnoid space

Report of four cases

François Grisoli, François Vincentelli, Sylvaine Fuchs, Mario Baldini, Charles Raybaud, Toussaint A. Leclercq, and Robert Pierre Vigouroux

✓ Four patients with tentorial arteriovenous malformations (AVM's) were treated surgically. The operative findings in the first case suggested that clipping of the draining vein close to the AVM may result in complete cure. The three subsequent cases were treated with this technique. The clinical and radiological implications are discussed.

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Neuroradiological findings of bleomycin leakage in cystic craniopharyngioma

Report of three cases

Lucie Lafay-Cousin, Ute Bartels, Charles Raybaud, Abhaya V. Kulkarni, Sharon Guger, Annie Huang, and Eric Bouffet

✓Intracystic bleomycin therapy has been proposed as a treatment for predominantly cystic craniopharyngioma. The risks of using this therapy, however, have not been clearly identified. The authors report on three children treated with intracystic bleomycin who developed initially mild symptoms during their course of therapy. They describe the neuroimaging findings from computed tomography (CT) scans and magnetic resonance (MR) images and the medical management of these three cases.

Two patients in whom craniopharyngioma was recently diagnosed and one patient with recurrent craniopharyngioma were treated with a course of 3 mg of intracystic bleomycin three times a week for 5 weeks, followed by once every week for 10 weeks. All patients had a negative reservoir permeability test prior to beginning intracystic bleomycin therapy. Patients were asymptomatic or had mild symptoms at the time of neuroimaging.

Magnetic resonance images revealed extensive vasogenic edema surrounding the cyst in all three patients, consistent with signs of bleomycin leakage. The edema occurred near the time of the 12th injection in two patients, and at the end of treatment in the remaining patient. Subsequently, two patients developed further symptoms suggestive of hypothalamic injury. These two patients received corticosteroids, leading to a rapid and sustained clinical improvement. Follow-up serial MR images showed a progressive regression of the surrounding edema.

Neuroimaging documentation of bleomycin toxicity has been described mainly in adults experiencing severe toxicity. There was no correlation between clinical symptoms and the extent of edema in these three patients. An MR image provides a higher resolution than CT scans for evaluating the adjacent cerebral structures and is very sensitive in detecting early abnormalities, even in asymptomatic patients. Bleomycin therapy requires close clinical monitoring. Imaging evaluation should be performed using MR imaging during treatment to ensure the safety of the therapy. In the authors' experience, the toxicity to bleomycin was transient. Management of the toxicity using high-dose steroid administration appears to contribute to controlling the bleomycin-induced inflammatory process.

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Differential patterns of metastatic dissemination across medulloblastoma subgroups

Michal Zapotocky, Daddy Mata-Mbemba, David Sumerauer, Petr Liby, Alvaro Lassaletta, Josef Zamecnik, Lenka Krskova, Martin Kyncl, Jan Stary, Suzanne Laughlin, Anthony Arnoldo, Cynthia Hawkins, Uri Tabori, Michael D. Taylor, Eric Bouffet, Charles Raybaud, and Vijay Ramaswamy

OBJECTIVE

Metastatic dissemination is a major treatment challenge and cause of death in patients with medulloblastoma. However, the influence of molecular biology on the pattern of metastatic dissemination at diagnosis is not known. In this study, the authors sought to define the location, pattern, and imaging characteristics of medulloblastoma metastases across subgroups at diagnosis.

METHODS

A consecutive cohort of patients with metastatic medulloblastoma at The Hospital for Sick Children and the University Hospital Motol, who underwent up-front MRI of the craniospinal axis, was assembled and allocated to subgroups using NanoString limited gene–expression profiling. Radiological characteristics (including location, morphology, size, diffusion restriction, and contrast enhancement) were discerned through a retrospective review.

RESULTS

Forty metastatic medulloblastomas were identified with up-front neuroimaging of the craniospinal axis: 5 sonic hedgehog (SHH), 16 Group 3, and 19 Group 4 metastases. Significant subgroup-specific differences were observed, particularly with respect to tumor location, size, and morphology. Group 3 metastases were most frequently laminar compared with a more nodular pattern in Group 4 (14 of 16 in Group 3 vs 8 of 19 in Group 4; p = 0.0004). Laminar metastases were not observed in patients with SHH medulloblastoma. Suprasellar metastases are highly specific to Group 4 (p = 0.016). Two of the 5 SHH cases had multifocal lesions in the cerebellum, raising the possibility that these were in fact synchronous primary tumors and not true metastases. A minority of patients with Group 4 metastases harbored metastatic deposits that did not enhance on MRI after contrast administration, often in patients whose primary tumor did not enhance.

CONCLUSIONS

The location, morphology, and imaging characteristics of metastatic medulloblastoma differ across molecular subgroups, with implications for diagnosis and management. This suggests that the biology of leptomeningeal dissemination differs among medulloblastoma subgroups.