Posterior Fossa Cyst and Hydrocephalus

A Dandy-Walker malformation is an anatomical triad characterized by a large posterior fossa, agenesis of the cerebellar vermis, and dilation of the 4th ventricle. Up to 90% of patients will have hydrocephalus secondary to obstruction of fourth ventricular outflow through the foramen of Luschka and Magendie. The differential diagnosis of Dandy-Walker malformation includes Blake’s pouch cyst, a cystic structure originating within the roof of the 4th ventricle that herniates into the cisterna magna, and posterior fossa arachnoid cysts, which typically displace both the cerebellum and 4th ventricle anteriorly and demonstrate a propensity to enlarge. Brain MRI is the best diagnostic imaging modality to evaluate posterior fossa anatomy and cystic structures. Not all posterior fossa cysts require treatment. Indications for surgical intervention include enlargement, symptomatic mass effect and/or hydrocephalus.

Craniopharyngioma

Pediatric craniopharyngioma is a histologically benign neoplasm with potential for malignant clinical behavior. Presenting vision and endocrine deficits are common, and the natural history carries unacceptable morbidity, including blindness, complete hypothalamic and pituitary dysfunction, and death. The goal of initial treatment for craniopharyngioma in the pediatric population should be permanent tumor control or cure in order to minimize morbidity from recurrent and progressive disease. Treatment-related morbidity is acute with surgical intervention and requires immediate postoperative endocrinological care. Radiotherapy is associated with delayed treatment morbidity, and long-term monitoring is critical. Inadequate tumor control after initial treatment will result in inevitable recurrence, with more complex and less effective treatment options and higher associated treatment morbidity. Unexpected intraoperative complications can be avoided with careful preoperative planning and good surgical technique.

Mesial Temporal Glioma

A patient with classic temporal lobe seizure semiology may present with aura, automatisms, and dystonic posturing. Video-electroencephalography (EEG) may identify the ictal onset and magnetoencephalography may further elucidate the anatomy of a temporal lobe abnormality, EEG dipoles, epileptogenic spike sources, and eloquent areas of language or motor function. Structural imaging of the temporal lobe with magnet resonance imaging (MRI) should also be obtained, as well as functional and metabolic imaging such as a subtraction single-photon emission computed tomography (SPECT) and interictal positron emission tomography (PET). Early surgery should be considered in pediatric patients for seizure control, to minimize the adverse effects of anti-epileptic drugs, maximize the child’s developmental potential, and reduce behavioral, cognitive and psychosocial problems. Intraoperative stereotactic navigation and electrocorticography (ECoG) can guide resection. Careful pre-operative planning for correct extent of surgery is key to the best possible seizure outcome.

Moyamoya Disease

Moyamoya disease is defined by stenosis of the distal intracranial internal carotid arteries up to and including the bifurcation, with segments of the proximal anterior and middle cerebral arteries, dilated basal collateral vessels, and bilateral findings. Detailed assessment with digital subtraction angiography will define the severity of disease (Suzuki stage) and presence of spontaneous transdural collateral vessels from external carotid artery branches. These collateral vessels must be protected during surgical intervention. The surgical goal is to establish a new vascular supply to the areas of the brain at risk for stroke, utilizing vessels from the external carotid circulation. Blood pressure control and avoidance of hyperventilation are key to minimize perioperative stroke risk. Preoperative hydration, ongoing use of aspirin, and good pain control will also minimize surgical complications.

Chiari Malformation with Syringomyelia

Chiari I malformation (CIM) is defined by pathological herniation of the cerebellar tonsils below the foramen magnum. Operative intervention for CIM is generally undertaken to treat neurological deficits associated with tonsillar herniation or with associated syringomyelia. A complete brain and spine MRI is indicated to rule out associated abnormalities and to identify and the presence and extent of syringomyelia. The type of surgical decompression remains controversial but may include bone-only decompression, bony decompression followed by duraplasty, and bony decompression followed by duraplasty and tonsillar shrinkage. Post-operative monitoring for CSF leakage, inadequate decompression, subtle chronic craniocervical instability, and hydrocephalus is critical.

Prematurity and Intraventricular Hemorrhage

Intraventricular hemorrhage caused by bleeding in the germinal matrix is a complication often seen in premature infants. Variations in cerebral blood flow may lead to rupture of the fragile, immature blood vessels due to their inability to autoregulate or accommodate changes in cerebral perfusion. Post-hemorrhagic hydrocephalus (PHH) may lead to significant neurologic compromise and can be diagnosed by assessing for symptoms and signs of infantile hydrocephalus, followed by radiologic imaging. Treatment options may include temporary and permanent cerebrospinal fluid diversion. Head ultrasound is a common imaging modality used for hydrocephalus surveillance in infants during their postnatal hospital stay in the neonatal intensive care unit. Evidence-based guidelines for the treatment of PHH have been published by the Joint Guidelines Committee of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons.

Sinusitus with Subdural Empyema

Subdural empyema is considered a neurosurgical emergency and, if found on neuroimaging, should prompt craniotomy for evacuation followed by broad spectrum antibiotics. In the setting of a patient with severe parenchymal swelling, a craniectomy may be indicated, as well as other modalities to lower intracranial pressure. Clinical care and decision making occurs with a multidisciplinary team of pediatric intensivists, infectious disease specialists, otolaryngologists, and neurosurgeons. Detection of recurrent subdural empyema is critical to prevent further morbidity and mortality, and surveillance of fever, neurologic examination, and follow-up imaging is critical. Timely surgical treatment of these infections can lead to good clinical outcomes.

Posterior Fossa Ependymoma

Pediatric posterior fossa ependymomas are typically well-delineated masses with heterogenous enhancement arising from the floor, lateral aspect, or roof of the fourth ventricle. Growth of tumor into the posterior fossa subarachnoid spaces, particularly into the foramen of Magendie and the cerebellopontine angles via the foramen of Luschka, is a radiological hallmark of this tumor. Clinical findings of elevated intracranial pressure and obstructive hydrocephalus are common at presentation. The current standard of care for children with ependymoma consists of gross total resection with subsequent focal radiotherapy. The extent of resection is the single most important determinant of outcome. Hydrocephalus typically resolves after resection, and it is uncommon to require cerebrospinal shunt placement after tumor removal.

Medulloblastoma

Medulloblastoma (MB) is the second most common cancer in children and the most common posterior fossa tumor. Presenting symptoms are key to an early diagnosis and may include signs and symptoms of hydrocephalus, cranial neuropathies, ataxia, or nystagmus. MRI of the neuraxis should be completed to aid in operative planning. Preoperative relief of hydrocephalus may be necessary, depending on the patient’s condition. Complete resection is the primary goal, and extent of resection, patient age, ependymal spread, and tumor subtype are all important predictors of overall survival. Spine imaging and lumbar puncture are standard to complete the initial work-up. Chemotherapy and radiation are used for adjuvant therapy after surgical resection. The need for postoperative shunt placement is rare, as most children can be weaned from their ventriculostomy catheters or an endoscopic third ventriculostomy can be performed.

Extratemporal Refractory Epilepsy

Medically refractory epilepsy is defined as the persistence of seizures after appropriate treatment with 2 different medications. A thorough understanding of the clinical history and semiology of seizures is important when considering surgical treatment options, as multifocal epilepsy may not be amenable to resective surgery. Anatomic, functional, and metabolic imaging sequences may assist in identifying a seizure focus, and EEG will provide a functional localization. The surgeon must make a careful and informed decision about the maximal amount of lesion that may be resected without incurring neurologic deficits. Specific postoperative management should be dictated by the natural history of the noted pathology.