Supratentorial Cortical-Based Tumors

Supratentorial cortical-based tumors represent 25 to 40% of all pediatric brain tumors and are typically derived from either glial or neuronal tissues.12 Up to 50% of the tumors in this region are astrocytomas, a glial-based tumor.12 Primary neuronal tumors include gangliogliomas, gangliocytomas, dysembryoplastic neuroepithelial tumors, and neurocytomas. Oligodendroglial, ependymal, and primitive neuroectodermal tumors also have predisposition for the cortex.

Supratentorial gliomas are often low grade, resulting in a slow and often unrecognizable progression of symptoms until cerebrospinal fluid is critically obstructed. The slow progression of symptoms is subsequently associated with a prolonged latency period prior to diagnosis. One study reported a mean latency of 8 months in the diagnosis of childhood supratentorial brain tumors.13 Nearly 50% of supratentorial tumors present with increased intracranial pressure, and upward of 40% of supratentorial tumors are associated with seizures.6 Other common manifestations of supratentorial cortical-based tumors are focal weakness and sensory deficits secondary to compression or destruction of motor and sensory pathways. More insidious symptoms such as difficulties with learning or memory may also be seen with cortical tumors.

The first presenting neurologic abnormality of both glial and neuronal tumors can be seizure.14 Although childhood seizures have been reported as the presenting symptom of brain tumors in 9% of children in one series, tumors are not commonly found in first-onset infantile seizures or childhood status epilepticus.3,15,16 The pathophysiology of the tumor-associated epileptogenesis is multifactorial and includes direct cortical tissue irritation, vasogenic/cytotoxic edema, dysplasia, microhemorrhage, and abnormal levels of neurotransmitters.17,18 EEG abnormalities that should prompt urgent neuroimaging (MRI with and without contrast) to exclude the presence of a brain tumor include noticeable asymmetry in background awake or asleep architecture and focal epileptiform discharges.

Deep Midline Tumors

Childhood deep midline tumors are a heterogeneous group of neoplasms that include those of the optic chiasm, pituitary, hypothalamus, thalamus, pineal gland, midbrain tectum, basal ganglia, and third ventricle. Compression of any one of these structures leads to recognizable symptoms based on the neuroanatomic pathway disruption ( Fig. 3.1 ). In the suprasellar region, craniopharyngiomas, hypothalamic/chiasmatic low-grade gliomas, and germinomas constitute the majority of tumor pathology. More than 50% of these tumors present with increased intracranial pressure.10

Vision loss is often the only complaint of an optic tract tumor, whereas a mass in the hypothalamic region can present with failure to thrive, precocious or delayed puberty, diabetes insipidus, and headaches, in addition to visual field defects. Young children and infants with failure to thrive secondary to diencephalic tumors often are misdiagnosed and undergo an extensive gastrointestinal evaluation for intractable anorexia, subsequently delaying diagnosis. Older children and adolescents with severe anorexia secondary to central nervous system (CNS) germinomas are also at risk of misdiagnosis with a primary psychiatric disorder.19,20 An expanding tumor of the thalamus may also result in compression and mass effect on the pyramidal tracts, thalamic nuclei, and optic radiations resulting in behavioral changes, mental status changes, increased intracranial pressure, motor deficits, and seizures.21 Although craniopharyngiomas and pituitary tumors are generally amenable to surgical resection, they can carry significant morbidity secondary to visual field loss and endocrinopathies.22,23

Tumors of the pineal and tectal region are commonly associated with obstructive hydrocephalus that can develop over days or months depending on tumor pathology. Tumors of this location can cause compression of the oculomotor nerve, and nearby Edinger-Westphal nuclei resulting in Parinaud′s syndrome, which is a constellation of paralysis of upgaze, pseudo-Argyll Robertson pupils, convergence or retraction nystagmus, and eyelid retraction. Tumors of the basal ganglia can present with unusual symptomatology including tics and other movement disorders. In the case of CNS germinoma, they can have unusual, nonspecific MRI features leading to significantly delayed diagnosis.20

Cerebellar Tumors

Approximately 45 to 60% of pediatric tumors originate in the posterior fossa and most frequently are juvenile pilocytic astrocytomas, medulloblastomas, ependymomas, as well as atypical teratoid rhabdoid tumors in young children.12 The most frequent symptoms include nausea, vomiting, and headache as a result of increased intracranial pressure, and ataxia as a result of cerebellar involvement.6,10 Cerebellar ataxia can either be axial or appendicular, depending on whether the tumor involves the midline or lateral cerebellum, respectively. The increased intracranial pressure component is a result of obstructive hydrocephalus at the level of the fourth ventricle. Depending on the chronicity of increased intracranial pressure, papilledema will not always be readily noticeable on routine funduscopic examination. Cerebellar tumors also affect speech with a characteristic “scanning” component termed cerebellar speech. Other associated symptoms related to posterior fossa tumors include torticollis and abnormal eye movements as a result of involvement of the flocculonodular lobe of the cerebellum.24

Brainstem Tumors

Greater than 10% of all childhood CNS tumors are located in the brainstem, according to data from Central Brain Tumor Registry of the United States.25 Brainstem tumors are usually described radiographically as diffuse, focal intrinsic, focal exophytic, and cervicomedullary.26 Critical structures of the brainstem that are disrupted by brainstem tumors include cranial nerve nuclei, the red nucleus, substantia nigra, locus coeruleus, corticospinal, corticopontine, spinothalamic, and spinocerebellar tracts.

Ocular symptoms are among the most frequent neurologic abnormalities that are recognizable by parents and clinicians in children with brainstem tumors involving the midbrain and pons. Tumors of the midbrain may cause oculomotor nerve palsy as well as tremors resulting from red nucleus disruption (rubrospinal tremor) or parkinsonian features related to involvement of the substantia nigra. Pontine tumors often present with abducens nerve palsy, facial nerve palsy, and motor deficits due to corticospinal tract involvement. Children with acute/subacute facial nerve palsy can be misdiagnosed as having Bell′s palsy if other cranial nerve deficits (weakness, hearing loss, and dysco-ordination) are not carefully tested. Involvement of the medial longitudinal fasciculus and parapontine reticular formation can manifest as uncoordinated lateral eye movements involving the third and sixth cranial nerves. Children with pontine tumors can also have urinary retention and overflow incontinence, secondary to involvement of the pontine micturition center.

Tumors of the cerebellar pontine angle, including gliomas, schwannomas, and meningiomas, can present with focal sensorineural hearing loss, tinnitus, or vertigo. Atypical features of brainstem gliomas that are often overlooked include abnormal behavior such as anxiety or inappropriate laughter, likely as a result of cerebropontocerebellar pathway involvement.27 Cervicomedullary junction tumors frequently present with lower cranial nerve palsies, resulting in dysphagia, dysarthria, apnea, and torticollis.14 Children with distal brainstem tumors may have ipsilateral sensory and contralateral motor deficits (i.e., crossed findings) due to the decussation of the corticospinal tracts at the level of the pontomedullary junction.

Spinal Cord Tumors

Primary spinal cord tumors account for approximately 6% of all childhood CNS tumors.25 Most common pathologies include pilocytic astrocytomas, ependymomas, primitive neuroepithelial tumors, and schwannomas, and they occur in the intramedullary, extramedullary intradural, and extradural space.28 Tumors of primary and nonprimary CNS origin, however, may metastasize to the spinal cord.

Without a careful history and neurologic examination, the diagnosis of spinal cord tumors can be delayed for months to years.29–31 Presenting symptoms of a spinal tumor are often quite subtle and may resemble other more common childhood spinal cord diseases such as Guillain-Barré, transverse myelitis, and acute disseminated encephalomyelitis. The most frequently reported symptom is back pain that typically worsens in the supine position and may present during the evening, but additional symptoms also include weakness, an abnormal gait or decreased coordination, a spinal deformity, abnormal bowel and bladder function, and focal motor weakness.3,30,31 Subtleties on examination may be notable for hemiatrophy and an abnormal sensory level pattern. Presenting features in the young child can be especially elusive, including symptoms such as gait abnormalities, abnormal eye movements, head tilt, early handedness, and torticollis.24,28,29 Involvement of the cervical cord may result in damage to the sympathetic chain at either the first-, second-, or third-order neurons, resulting in Horner syndrome (ptosis, miosis, and anhidrosis).