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BRAIN TUMORS
N Engl J Med
Sun Yong'an
BRAIN TUMORS
? The term "brain tumor" refers to a collection of neoplasms, each with its own biology, prognosis, and treatment; these tumors are better identified as "intracranial neoplasms," since some do not arise from brain tissue (e.g., meningiomas and lymphomas).
? However, for most intracranial tumors, the clinical presentation, diagnostic approach, and initial treatment are similar. This night we will focus on general presentation, diagnosis, and specific treatment.
EPIDEMIOLOGY
? The American Cancer Society estimates that 16,800 new intracranial tumors were diagnosed in 1999, more than double the number of diagnosed cases of Hodgkin's disease and over half the number of cases of melanoma
? Ionizing radiation is the only unequivocal risk factor that has been identified for glial and meningeal neoplasms. Irradiation of the cranium, even at low doses, can increase the incidence of meningiomas by a factor of 10 and the incidence of glial tumors by a factor of 3 to 7,with a latency period of 10 years to more than 20 years after exposure.
EPIDEMIOLOGY
? No other environmental exposure or behavior has been clearly identified as a risk factor. The use of cellular telephones, exposure to high-tension wires, the use of hair dyes, head trauma, and dietary exposure to N-nitro-sourea compounds or other nutritional factors have all been reported to increase the risk of brain tumors; however, the data are conflicting and unconvincing.
CLINICAL PRESENTATION
? Brain tumors can cause either focal or generalized neurologic symptoms. Generalized symptoms reflect increased intracranial pressure and consist of headache and, when the illness is. Focal symptoms and signs, such as hemiparesis and aphasia, reflect the intracranial location of the tumor. The severe, nausea, vomiting, and a sixth-nerve palsy frequency and duration of symptoms vary with the type of tumor. For example, a rapidly evolving hemiparesis is more typical of a high-grade than a low-grade glioma.
CLINICAL PRESENTATION
? Headache occurs in about half of all patients with brain tumors. Typically, the headache is diffuse, but it can accurately indicate the hemisphere in which the tumor is located.
? Seizures occur at presentation in 15 to 95 percent of patients with brain tumors, depending on the type of tumor (Table 2). Typically, the seizures are focal but may become generalized and cause loss of consciousness. Postictal hemiparesis or aphasia (Todd's phenomenon) may indicate the location of the tumor.
CLINICAL PRESENTATION
? Other symptoms that reflect the location of the tumor, such as hemiparesis or aphasia not associated with seizures, typically have a subacute onset and are progressive. The exception is a visual-field deficit that may develop progressively but that often goes unnoticed by the patient until it contributes to an accident (frequently an automobile accident).
DIAGNOSIS
? The only test needed to diagnose a brain tumor is cranial magnetic resonance imaging (MRI). Computed tomography (CT) can miss structural lesions, particularly in the posterior fossa, or nonenhancing tumors such as low-grade gliomas. Therefore, if a brain tumor is a diagnostic consideration, MRI with gadolinium enhancement is the test of choice; a normal contrast-enhanced MRI scan essentially rules out the possibility of a brain tumor.
GLIAL TUMORS
? Glial tumors are divided into two main categories: astrocytic and oligodendroglial. Both can be either low grade or high grade. High-grade (malignant) glial neoplasms can arise either alone (primary glioblastoma) or from a preexisting low-grade tumor (secondary glioblastoma); in secondary glioblastoma, low-grade tumor may be immediately adjacent to highly malignant disease. Error can occur when a small sample is taken for biopsy and the examined tissue does not reflect the biology of the entire tumor, particularly if features indicative of malignancy are missed. All gliomas, particularly the astrocytic neoplasms, are histologically, genetically, and thus therapeutically heterogeneous.
CLINICAL PRESENTATION
? Glial tumors are graded pathologically, on the basis of the most malignant area identified, according to either the World Health Organization (WHO) system or the St. Anne-Mayo system, both of which are based on the presence or absence of nuclear atypia, mitosis, microvascular proliferation, and necrosis(Fig. 1). Accurate pathological grading is essential because it defines treatment and prognosis. The histologic features of the tumor and the patient's age and performance status are major prognostic factors and have more influence than any specific therapy on the outcome.
CLINICAL PRESENTATION
? Astrocytic Tumors
Astrocytoma
Malignant Astrocytoma
? Oligodendroglial Tumors
Low-Grade Oligodendroglioma
Anaplastic Oligodendroglioma
Astrocytoma
? Astrocytomas are tumors found in young adulthood, with a peak incidence in the third to fourth decade of life. Typically, the first clinical manifestation is a seizure, which may be accompanied or followed by other neurologic symptoms or signs. The diagnosis is usually established when neuroimaging is performed to evaluate the seizure. The characteristic appearance of an astrocytoma on MRI is that of a diffuse, nonenhancing mass that is hypointense on T1-weighted images and best seen on T2-weighted images or those obtained with the use of fluid-attenuated inversion recovery, on which the mass is brightly outlined against normal brain tissue (Fig. 2).
CLINICAL PRESENTATION
? Because most patients with astrocytoma are young and neurologically normal, except for having had an isolated seizure, treatment is particularly challenging. When the lesion is amenable to complete surgical excision, resection should be performed.
? Radiation therapy is the most effective nonsurgical therapy for astrocytomas; however, early diagnosis and treatment do not necessarily improve survival and may cause disability.......（后略) ......
BRAIN TUMORS
N Engl J Med
Sun Yong'an
BRAIN TUMORS
? The term "brain tumor" refers to a collection of neoplasms, each with its own biology, prognosis, and treatment; these tumors are better identified as "intracranial neoplasms," since some do not arise from brain tissue (e.g., meningiomas and lymphomas).
? However, for most intracranial tumors, the clinical presentation, diagnostic approach, and initial treatment are similar. This night we will focus on general presentation, diagnosis, and specific treatment.
EPIDEMIOLOGY
? The American Cancer Society estimates that 16,800 new intracranial tumors were diagnosed in 1999, more than double the number of diagnosed cases of Hodgkin's disease and over half the number of cases of melanoma
? Ionizing radiation is the only unequivocal risk factor that has been identified for glial and meningeal neoplasms. Irradiation of the cranium, even at low doses, can increase the incidence of meningiomas by a factor of 10 and the incidence of glial tumors by a factor of 3 to 7,with a latency period of 10 years to more than 20 years after exposure.
EPIDEMIOLOGY
? No other environmental exposure or behavior has been clearly identified as a risk factor. The use of cellular telephones, exposure to high-tension wires, the use of hair dyes, head trauma, and dietary exposure to N-nitro-sourea compounds or other nutritional factors have all been reported to increase the risk of brain tumors; however, the data are conflicting and unconvincing.
CLINICAL PRESENTATION
? Brain tumors can cause either focal or generalized neurologic symptoms. Generalized symptoms reflect increased intracranial pressure and consist of headache and, when the illness is. Focal symptoms and signs, such as hemiparesis and aphasia, reflect the intracranial location of the tumor. The severe, nausea, vomiting, and a sixth-nerve palsy frequency and duration of symptoms vary with the type of tumor. For example, a rapidly evolving hemiparesis is more typical of a high-grade than a low-grade glioma.
CLINICAL PRESENTATION
? Headache occurs in about half of all patients with brain tumors. Typically, the headache is diffuse, but it can accurately indicate the hemisphere in which the tumor is located.
? Seizures occur at presentation in 15 to 95 percent of patients with brain tumors, depending on the type of tumor (Table 2). Typically, the seizures are focal but may become generalized and cause loss of consciousness. Postictal hemiparesis or aphasia (Todd's phenomenon) may indicate the location of the tumor.
CLINICAL PRESENTATION
? Other symptoms that reflect the location of the tumor, such as hemiparesis or aphasia not associated with seizures, typically have a subacute onset and are progressive. The exception is a visual-field deficit that may develop progressively but that often goes unnoticed by the patient until it contributes to an accident (frequently an automobile accident).
DIAGNOSIS
? The only test needed to diagnose a brain tumor is cranial magnetic resonance imaging (MRI). Computed tomography (CT) can miss structural lesions, particularly in the posterior fossa, or nonenhancing tumors such as low-grade gliomas. Therefore, if a brain tumor is a diagnostic consideration, MRI with gadolinium enhancement is the test of choice; a normal contrast-enhanced MRI scan essentially rules out the possibility of a brain tumor.
GLIAL TUMORS
? Glial tumors are divided into two main categories: astrocytic and oligodendroglial. Both can be either low grade or high grade. High-grade (malignant) glial neoplasms can arise either alone (primary glioblastoma) or from a preexisting low-grade tumor (secondary glioblastoma); in secondary glioblastoma, low-grade tumor may be immediately adjacent to highly malignant disease. Error can occur when a small sample is taken for biopsy and the examined tissue does not reflect the biology of the entire tumor, particularly if features indicative of malignancy are missed. All gliomas, particularly the astrocytic neoplasms, are histologically, genetically, and thus therapeutically heterogeneous.
CLINICAL PRESENTATION
? Glial tumors are graded pathologically, on the basis of the most malignant area identified, according to either the World Health Organization (WHO) system or the St. Anne-Mayo system, both of which are based on the presence or absence of nuclear atypia, mitosis, microvascular proliferation, and necrosis(Fig. 1). Accurate pathological grading is essential because it defines treatment and prognosis. The histologic features of the tumor and the patient's age and performance status are major prognostic factors and have more influence than any specific therapy on the outcome.
CLINICAL PRESENTATION
? Astrocytic Tumors
Astrocytoma
Malignant Astrocytoma
? Oligodendroglial Tumors
Low-Grade Oligodendroglioma
Anaplastic Oligodendroglioma
Astrocytoma
? Astrocytomas are tumors found in young adulthood, with a peak incidence in the third to fourth decade of life. Typically, the first clinical manifestation is a seizure, which may be accompanied or followed by other neurologic symptoms or signs. The diagnosis is usually established when neuroimaging is performed to evaluate the seizure. The characteristic appearance of an astrocytoma on MRI is that of a diffuse, nonenhancing mass that is hypointense on T1-weighted images and best seen on T2-weighted images or those obtained with the use of fluid-attenuated inversion recovery, on which the mass is brightly outlined against normal brain tissue (Fig. 2).
CLINICAL PRESENTATION
? Because most patients with astrocytoma are young and neurologically normal, except for having had an isolated seizure, treatment is particularly challenging. When the lesion is amenable to complete surgical excision, resection should be performed.
? Radiation therapy is the most effective nonsurgical therapy for astrocytomas; however, early diagnosis and treatment do not necessarily improve survival and may cause disability.......（后略) ......
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