Brain tumors may originate from neural elements within the brain or they may represent spread of distant cancers. Gliomas, metastases, meningiomas, pituitary adenomas, and acoustic neuromas account for 95% of all brain tumors.
Presenting symptoms and signs of patients with an intracranial neoplasm tend to be similar for primary brain tumors and intracranial metastases. The onset of symptoms usually is insidious, but an acute episode may occur with bleeding into the tumor or when an intraventricular tumor suddenly occludes the third ventricle.
Manifestations may be nonspecific and include the following:
Headache characteristics of brain tumors:
Usually nonspecific resembling tension-type headaches.
Not an isolated finding, often is a late complaint.
New onset headaches in middle-aged or older patients is worrisome.
The location of headache reliably indicates the side of the head affected, but it does not indicate the precise site of the tumor.
Headaches are more common with posterior fossa tumors.
Headache is a more frequent symptom of intracranial tumor in children.
Prevailing inaccurate portrayals of a tumor headache include:
Pain is worse in the early morning accompanied by vomiting (with or without nausea).
Exacerbation with Valsalva maneuver, bending over, or rising from a recumbent position.
Brain tumors may also manifest as follows:
More than one-third of patients with newly diagnosed brain tumors develop epileptic seizures. If the tumor involves the cerebral hemispheres, seizures occur in at least 50% of patients. Any brain tumor, benign or malignant, common or uncommon, can cause seizures. Patients with low-grade tumors may be more likely to develop epilepsy, possibly because their longer survival allows more time for seizures to develop.
The tumors that are highly associated with the development of epilepsy are:
The tumors most often presenting with seizures in adults are:
The tumors most often presenting with seizures in children are:
No physical finding or pattern of findings unmistakably identifies a patient with a central nervous system (CNS) neoplasm. Based on their location, intracranial tumors may produce a focal or generalized deficit, but signs may be lacking (e.g., frontal lobe tumors) or even falsely localizing.
Papilledema, which is more prevalent with paediatric brain tumors, reflects an increase in intracranial pressure (ICP) for several days or longer.
Diplopia may result from displacement or compression of the sixth cranial nerve at the base of the brain.
Impaired upward gaze, called Parinaud’s syndrome, may occur with pineal tumors.
Tumors of the occipital lobe specifically may produce homonymous hemianopia or partial visual field deficits.
Anosmia may occur in case of frontal lobe tumors.
Brain stem and cerebellar tumors induce cranial nerve palsies, ataxia, incoordination, nystagmus, pyramidal signs, and sensory deficits on one or both sides of the body.
CT and MRI have complementary roles in the diagnosis of CNS neoplasms. The speed of CT is desirable for evaluating clinically unstable patients; it is superior for detecting calcification, skull lesions, and hyperacute hemorrhage (bleeding less than 24 hours old) and helps direct differential diagnosis as well as immediate management. MRI has superior soft-tissue resolution; it can better detect isodense lesions, tumor enhancement, and associated findings such as edema, all phases of hemorrhagic states (except hyperacute), and infarction. High-quality MRI is the diagnostic study of choice in the single-photon emission computed tomography (SPECT) and positron emission tomography (PET) may be useful in differentiating tumor recurrence from radiation necrosis.
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6.1 Intracranial Tumors Based on Their Anatomic Location
6.1.2 Intraventricular tumors
Lateral ventricles (LVs) (favored sites)
Astrocytoma (anaplastic, glioblastoma)
Subependymal giant cell astrocytoma (Foramen of Monro)
Subependymoma (fourth ventricle)
Oligodendroglioma (neurocytoma) (septum pellucidum, LV)
Choroid plexus cysts/xanthogranulomas (atrium of LV)
Choroid plexus papilloma/carcinoma (atrium of LV)
Primary cerebral neuroblastoma
Cerebral hemangiomas (all sites)
Brenner AV, Linet MS, Fine HA, et al. History of allergies and autoimmune diseases and risk of brain tumors in adults. Int J Cancer 2002; 99(2):252–259
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6.2 Pineal Tumors
Pineal region tumors make up 0.4–1.0% of intracranial tumors in adults and 3.0–8.0% of brain tumors in children. Most children are aged 10–20 years at presentation, with the average age at presentation being 13 years. Adults typically are older than 30 years at presentation (▶Fig. 6.1).
Fig. 6.1 Pineal lesions (a) Germinoma. Sagittal T1-WI with a large, solid space-occupying lesion originating from the pineal gland and a high postcontrast signal intensity causing compression of the brain stem and cerebellum with distortion of the fourth ventricle. There is also descent of the cerebellar tonsils. (b) Astrocytoma and suprasellar metastasis. Sagittal T1-WI shows a postcontrast enhancing mass in the pineal region producing compression of the quadrigeminal plate. A second suprasellar mass compresses the pituitary stalk. The patient presented clinical signs of diabetes insipidus. (c) Medulloblastoma. Sagittal T1-WI with a solid, multilobular space-occupying lesion, which presents an intermediate, heterogenous postcontrast enhancement and is housed in the upper region of the cerebellum and fourth ventricle. (d) Basilar aneurysm. Sagittal T1-WI demonstrates a partially thrombosed giant aneurysm of the basilar artery, which acts as a space-occupying mass and thus compresses the pons, the cerebral peduncles, and the third ventricle, extending retrochiasmatically into the suprasellar cisterns.
Most tumors are a result of displaced embryonic tissue, malignant transformation of pineal parenchymal cells, or transformation of surrounding astroglia. A complete differential diagnosis for masses in the pineal region should also include vascular anomalies, as well as metastatic tumor.
Mass lesions in the pineal region commonly present with headaches, nausea, and vomiting caused by aqueductal compression and resultant obstructive hydrocephalus, which if left untreated may lead progressively to lethargy, obtundation, and death. Compromise of the superior colliculus results in a syndrome of vertical gaze palsy (Parinaud’s syndrome) that can be associated with pupillary or oculomotor nerve paresis. Further compression of the periaqueductal gray region may cause mydriasis, convergence spasm, pupillary inequality, and convergence of refractory nystagmus. Children may also present with endocrine malfunction (diabetes insipidus, pseudoprecocious puberty—93% of girls > 12 years had secondary amenorrhea and 33% of patients < 15 years had growth arrest).
Pineal parenchymal (cell origin) tumors
Tumors of supportive tissues and adjacent structures
Metastatic tumors of the pineal gland (extremely rare; 75 total reported cases)
Non-neoplastic tumor-like conditions
Cho BK, Wang KC, Nam DH, et al. Pineal tumors: experience with 48 cases over 10 years. Childs Nerv Syst 1998; 14(1–2):53–58
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Villano JL, Propp JM, Porter KR, et al. Malignant pineal germ-cell tumors: an analysis of cases from three tumor registries. Neuro Oncol 2008; 10(2):121–130
Chang T, Teng MM, Guo WY, Sheng WC. CT of pineal tumors and intracranial germ-cell tumors. Am J Neuroradiol 1989; 10(5):1039–1044
6.3 Cerebellopontine Angle Masses
Tumors of the cerebellopontine angle (CPA) constitute about 6–10% of all intracranial tumors. It is a disease common in adults and rare in children. There is a wide variety of conditions that can occur at this level, derived from both the structures forming the CPA, as well as lesions that grow near it and can secondarily invade this area of CPA (▶Fig. 6.2 and ▶Fig. 6.3).
Fig. 6.3 Cerebellopontine angle (CPA) lesions. (a) Acoustic neurinoma. Axial CT with right acoustic neurinoma and erosion of the internal auditory meatus with a small protrusion of the tumor in the CPA. (b) Erosion of the auditory meatus. Bone windows of an axial CT of the same patient with an abnormal erosion of the right internal auditory meatus. (c) Acoustic neurinoma. A solid space-occupying mass with mild postcontrast enhancement producing erosion of the right acoustic meatus, protrusion into the right CPA, and compression of the pons and cerebellar peduncles. (d) Chordoma. Axial T1-WI shows a solid, space-occupying lesion with postcontrast enhancement occupying the left middle temporal fossa and ipsilateral CPA as well as erosion of the apex of the petrous and sphenoid bone. (e, f) Meningioma. Axial and coronal T1-WI with a postcontrast enhancing meningioma of the right CPA that extends into the right jugular foramen causing compression of the medulla oblongata and the right cerebellar hemisphere. (g) Epidermoid tumor. Coronal T1-WI with a cystic space-occupying, nonenhancing lesion in the right CPA with compression signs of the pons. (h) Epidermoid tumor. A solid and heterogeneous mass with smooth margins eroding the left occipital bone and compressing the left cerebellar hemisphere is seen on axial T1-WI.
The masses are the most commonly vestibular-cochlear schwannomas and meningiomas, representing approximately 85–90% of all tumors of the anterior pontine cistern (APC). Next in frequency are epidermoid cyst and schwannomas of other cranial nerves.
Masses of the CPA with their frequency are discussed below.
6.3.1 Adult
Most common mass that comprises 60–92% of CPA lesions and involves the vestibular division of the CN VIII.
Second most common lesion seen in up to 3–7% of cases. Usually arises from posterior surface of the petrous bone and does not extend into IAC. Broad-based against petrous bone.
Also known as congenital cholesteatoma or pearly tumor; accounts for 2–6% of CPA masses. Congenital lesions of rest of ectodermal tissue containing stratified squamous linings and keratin. May arise within the temporal bone or in the CPA. Low attenuation (CT); lobulated mass (MRI) of signal similar to cerebrospinal fluid (CSF) on most sequences but increased signal on fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI). Grows surrounding vessels and nerves.
Also known as glomus jugulare tumor; a chemodectoma arising from the jugular foramen (JF) and extending into the CPA.
Trigeminal and facial nerves are probably the most common sites of nonacoustic schwannomas. Other cranial nerves involved are CNs VI, IX, X, XI, and rarely XII.
Vertebrobasilar dolichoectasia (3–5%)
Elongation and dilatation of the vertebrobasilar artery. Symptoms are fascial spasms, trigeminal neuralgia etc.
Anterior inferior cerebellar artery (AICA) loop: May loop over, under, or between CNs VII and VIII. Main symptom is vertigo.
Choroid plexus papilloma (1%; primary in the CPA or extension via the lateral foramina of Luschka)
Ependymoma (1%; extension from the fourth ventricle)
Skull base/temporal bone tumors (e.g., glomus tumors, metastases, cholesterol granuloma)
Skull base infection (e.g., osteomyelitis of the petrous apex = Gradenigo’s syndrome, malignant otitis external)
Uncommon lesions (< 1% incidence)
6.3.2 Paediatric
6.3.3 Differential diagnosis based on the MRI characteristics
Hemorrhagic acoustic schwannoma
Neurenteric cyst (usually prepontine, but fluid may be proteinaceous and high on T1-WI)
Thrombosed berry aneurysm (often will have calcified rim, and hemosiderin staining)
White epidermoid (rare, and will restrict on DWI)
CPA lipoma (usually has the facial nerve and vestibulocochlear nerve coursing through it; will saturate on fat suppressed sequences)
Ruptured intracranial dermoid (often multiple droplets, and original midline lesion can be often seen)
Low T1 signal mass (CSF density mass)
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6.4 Internal Auditory Meatus Masses
Neuritis (Bell’s palsy, Ramsay Hunt syndrome or herpes zoster otitis, and viral infections are benign conditions that can cause cranial nerve enlargement)
Postoperative reactive dural fibrosis (second most common cause of enlargement of the internal auditory meatus)
Vascular (hemorrhage, vascular loop of AICA, arteriovenous malformations (AVM) or aneurysm)
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Bohner PS, Chole RA. Unusual lesion of the internal auditory canal. Am J Otol 1996; 17(1):140–186
6.5 Foramen Magnum Masses
In cases of benign extramedullary tumors of the foramen magnum (e.g., commonly meningiomas, neurofibromas, and the less common teratomas, chordomas etc.), the most frequent presenting complaints were suboccipital neck pain, dysesthesias, gait disturbances, weakness, and hand clumsiness. The average time from initial symptoms to diagnosis was 2¼ years. The most common findings included hyperreflexia, arm or hand weakness, Babinski sign, spastic gait, sensory loss, and CN XI involvement. There is no clinical finding that is pathognomonic (▶Fig. 6.4 and ▶Fig. 6.5).
Fig. 6.5 Foramen magnum (a) Glioma of the high cervical spinal cord (C2), producing a focal expansion of the spinal cord, is seen on this midsagittal T1-WI. (b) Meningioma. Axial CT demonstrates a calcified meningioma of the posterior part of the foramen magnum compressing the medulla oblongata. (c) Epidermoid cyst. Axial CT with a cystic lesion of the foramen magnum causing compression of the medulla oblongata. (d) Chiari II malformation. Sagittal T1-WI shows a descent of the cerebellar tonsils and compression of the medulla oblongata and associated syringomyelia. (e) Osteolysis of C2 and a mass of soft tissues producing compression and displacement of the spinal cord is seen on coronal T1-WI. (f) Atlantoaxial subluxation. Sagittal T2-WI shows atlantoaxial subluxation with the development of inflammatory tissue around the dens of C2. This pathology causes stenosis of the foramen magnum and compression of the spinal cord and lower medulla. Focal myelinolysis is indicated by a high-intensity signal.
Intra-axial cervicomedullary masses
Commonly of low grade and 50% of them occur in the cervicomedullary junction. Extension of spinal cord glioma in this area is also common. Other types of gliomas, however, such as anaplastic astrocytoma, ganglioglioma, ependymoma are also found here.
Inferior extension of medulloblastoma in children and hemangioblastoma in adults are common in this area.
Anterior extramedullary intradural masses
Most common mass anterior to the medulla is a tortuous, ectatic vertebral artery. Occasionally, aneurysms of the vertebral or the PICA are seen.
Most common primary neoplasm in this area.
From CNs IX and XI. Neurofibromas from existing spinal nerve segments occur laterally.
Metastases (cisternal, perineural, and skull base)
Arachnoid, inflammatory, and neurenteric cysts
Posterior extramedullary intradural masses
Congenital/acquired tonsillar herniation (comprises 5–10% of all foramen magnum masses)
Ependymoma and medulloblastoma (intra-axial caudal extension of posterior fossa neoplastic masses)
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6.6 Skull Base Tumors
Skull base tumors arise from the cranial base or reach it either from an intracranial or extracranial origin. These may originate from the neurovascular structures of the base of the brain and the basal meninges (e.g., meningioma, pituitary adenoma, schwannoma, paraganglioma, hemangiopericytoma), the cranial base itself (e.g., chordoma, chondrosarcoma, osteosarcoma, plasmacytoma, metastasis), or the subcranial structures of the head and neck (e.g., sinonasal carcinomas, olfactory neuroblastoma, juvenile angiofibroma, nasopharyngeal carcinoma, adenoid cystic carcinoma, primary sarcomas) (▶Fig. 6.6 and ▶Fig. 6.7).
Fig. 6.7 Skull base lesions. (a) Fibrous dysplasia. Axial proton density MRI with thickening of the right sphenoid bone and reduction of the size of the orbit and associated exophthalmos. (b) Meningioma of the right cavernous sinus. Coronal T1-WI shows expansion of the right cavernous sinus and a very high signal intensity following contrast enhancement. (c) Metastasis. Axial CT demonstrating an osteolytic lesion of the sphenoid tip of the petrous bone. (d) Chordoma. Axial CT with a high-density space-occupying lesion of the left temporal fossa and the parasellar region. The mass is eroding the apex of the petrous bone and is extending to the cerebellopontine angle (CPA) of the same side. (e) Paraganglioma or glomus jugulare. Axial CT shows a space-occupying lesion of the right CPA that occupies the right jugular foramen and demonstrates intense, heterogeneous postcontrast enhancement. (f) Paget’s disease. Axial CT shows a marked thickening of all bones of the skull base with reduction of the size of the posterior fossa.
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