Amongdementias,Alzheimerdisease(withplaquesofAβ andtanglesoftau)isthemostcommon;otherpredominantlydementingdiseasesincludethevariousformsofFTLDs(bothformswithtau-containinglesionsandwithothertypesofinclusions)anddementiawithLewybodies(withα-synucleincontaininglesions).
Amongthehypokineticmovementdisorders,Parkinsondiseaseisthemostcommon,withα-synucleincontaininginclusions.
Amyotrophiclateralsclerosis(ALS)isthemostcommonformofmotorneurondisease,withdiversegeneticcausesaswellassporadicforms.
The annual incidence of CNS tumors ranges from 10 to 17 per 100,000 individuals for intracranial tumors and 1 to 2 per 100,000 individuals for intraspinal tumors; about one- decades of life. They usually are found in the cerebral hemispheres. The most common presenting signs and symptoms are seizures, headaches, and focal neurologic deficits related to the anatomic site of involvement. On the basis of histologic features, astrocytomas are stratified into three groups: diffuse astrocytoma (grade II), anaplastic astrocytoma (grade III), and glioblastoma (grade IV), with increasingly grim prognosis as the grade increases.
There is emerging evidence that genetic subtyping provides important additional prognostic information.
Diffuse astrocytomas can be static for several years, but at some point they progress; the mean survival is more than 5 years. Eventually, patients suffer rapid clinical deterioration that is correlated with the appearance of anaplastic features and more rapid tumor growth. Other patients present with glioblastoma from the outset. Once the histologic features of glioblastoma appear, the prognosis is very poor; with treatment (resection, radiotherapy, and chemotherapy), the median survival is only 15 months.
half to three-fourths are primary tumors, and the rest are metastatic. Tumors of the CNS make up a larger propor- tion of childhood cancers, accounting for as many of 20% of all pediatric tumors. Childhood CNS tumors differ from those in adults in both histologic subtype and location. In childhood, tumors are likely to arise in the posterior fossa, whereas tumors in adults are mostly supratentorial.
Tumors of the nervous system have unique characteristics that set them apart from neoplastic processes elsewhere in the body.
These tumors do not have morphologically evident premalignant or in situ stages comparable to those of carcinomas.
Even low-grade lesions may infiltrate large regions of the brain, leading to serious clinical deficits, inability to be resected, and poor prognosis.
The anatomic site of the neoplasm can influence outcome independent of histologic classification due to local effects (e.g., a benign meningioma may cause cardiorespiratory arrest from compression of the medulla).
Even the most highly malignant gliomas rarely spread outside of the CNS.
Gliomas are tumors of the brain parenchyma that have long been classified as astrocytomas, oligodendrogliomas, and ependymomas based on their morphologic resemblance to different types of glial cells. With emerging genetic information, it has become clear that the gliomas are a molecularly distinct family of neoplastic lesions, independent of the histologic patterns. Nonetheless, histologic patterns continue to inform diagnosis and guide treatment, with refinement based on molecular characterization. The diffuse gliomas constitute the vast majority of gliomas that occur in adults, and include diffuse astrocytomas and oligodendrogliomas.
Astrocytomas account for about 80% of adult gliomas. They are most frequent in the fourth through the sixth
GradeIIandIIIastrocytomasarepoorlydefined,gray,infiltrativetumorsthatexpandanddistorttheinvadedbrainwithoutformingadiscretemass(