Brain Tumors: Introduction, Classification, and Diagnostic Evaluation

00:01 Today we're going to talk about tumors of the nervous system.

00:04 This is one of my favorite topics in neurology.

00:07 I think you're going to really enjoy it, but it is complex.

00:10 So we'll walk through a systematic approach to evaluating patients or clinical vignettes, who are presenting with tumors of the nervous system.

00:19 Let's start with an introduction.

00:21 There are many types of brain tumors, and spinal cord tumors, and peripheral nerve sheath tumors that occur in the nervous system.

00:29 Here you can see just a few.

00:31 And in the course of this lecture series, I'd like for you to be able to approach a patient or a clinical vignette and understand the type of tumor and the treatment for that tumor that we would think about for a patient or that patient in a vignette.

00:45 We're going to talk about a number of different types of tumors.

00:48 We're going to talk about inherited tumor conditions, things like tuberous sclerosis and neurofibromatosis.

00:54 And you'll be able to recognize those images by the end of this lecture series.

00:58 We're going to talk about some common benign tumors that occur in the nervous system.

01:02 Things like meningiomas and pituitary adenomas, and be able to recognize what they look like on the imaging.

01:08 We'll also talk about common tumors you hear about, or may even have a personal connection with gliomas or glioblastomas and understand how to diagnose and treat those patients as well.

01:19 So at the end of this lecture series, I hope you can go through, and understand, and evaluate, and diagnose each of the tumors that are on this slide.

01:27 Let's start with some ways that we as clinicians go about understanding and classifying tumors.

01:33 The first is the think of the common things that occur in the nervous system, because common things are common.

01:39 And the most common tumor that occurs in the nervous system is actually not something that occurs and develops from the brain itself. It's a brain metastasis.

01:48 These are tumors that start in the systemic circulation from a circulating or systemic cancer, and travel or metastasized to the brain.

01:57 So the most common type of brain tumor is a brain metastasis.

02:00 And that accounts for about 50% of the tumors in the nervous system.

02:04 The other 50% of tumors are those primary brain tumors.

02:08 Things that start from the brain, and develop in the brain and cause problems in the brain.

02:13 And we're gonna think of four.

02:14 There are four common primary brain tumors.

02:17 The most common is the meningioma.

02:19 It's a benign brain tumor that occurs on the outer surface of the brain.

02:22 And we'll talk a little bit more about how you diagnose and manage patients with meningioma.

02:27 The second most common is the pituitary adenoma.

02:30 A common benign and often incidental finding for patients.

02:34 And that we may discover on a clinical vignette.

02:37 Gliomas are the third most common primary brain tumor.

02:40 And are really important to recognize, diagnose, and get to the right treatment, and we'll talk about that.

02:45 And then the fourth is the vestibular schwannoma, which can also occur in an inherited tumor syndrome.

02:51 The other way to classify and characterize brain tumors is by their cell type or location.

02:57 And this works really well when we're evaluating patients.

03:00 Patients present with a new typically focal neurologic deficit, and they get an image, a CT scan, or an MRI.

03:08 And we could see one and two things.

03:10 We could see a tumor in the brain parenchyma.

03:12 And then we'll use the cell type of origin method to develop a differential diagnosis, or the tumor could be outside of the brain or in a certain selected area and we'll use that location to develop a differential diagnosis.

03:26 So let's talk about each of those two methods for classifying brain tumors.

03:30 The cell type of origin, and the location.

03:36 First, let's think about the cells that live in the brain.

03:38 There are five major cells that I want you to think about.

03:41 The first is the oligodendrocyte.

03:43 That's the myelin producing cell in the brain.

03:46 It myelinates the nerve.

03:48 The second is the astrocyte.

03:50 That's the most abundant cell in the brain.

03:51 And it turns out, that's the most common tumor that we will see in the brain or cell type of origin.

03:58 There are microglia, there are ependymal cells there are neuroepithelial, or primitive neuroectodermal cells.

04:05 And each of these can give rise to a certain tumor.

04:08 And tumors that arise in the brain parenchyma, we can use those cell types to develop a differential diagnosis.

04:14 There are also five key locations that we can think about in the brain.

04:18 There the meninges, the pineal gland, the pituitary gland, this thing called the CP angle, or the cerebellopontine angle, and then the peripheral nerve, which is actually in the peripheral nervous system.

04:29 And we see tumors that occur in each of those locations and can use that location to develop a differential diagnosis.

04:36 So this helps us when we're evaluating patients.

04:39 When we think about tumors that arise in the brain parenchyma and think of those cell types that can drive us towards a certain tumor type.

04:47 From the astrocytes, we get astrocytoma.

04:50 And that's the most common, and most abundant malignant tumor of the brain.

04:53 From the oligodendrocytes, we see oligodendrogliomas.

04:58 From the ependymal cells, ependymomas.

05:01 From those primitive neuroepithelial, or neuroectodermal cells, which arise from the neural crest cells, we see Primitive Neuroectodermal Tumors or PNETs.

05:12 From the choroid plexus, we see choroid plexus tumors.

05:16 Circulating immune cells can get into the brain.

05:19 And those are typically lymphomas.

05:20 And we can see those arise in the brain parenchyma.

05:23 And then there are the neurons.

05:25 And these are actually the least common type of tumors in the brain.

05:28 The neurons do everything that the brain does, but we often don't see tumors that arise from the neurons.

05:33 And those neuronal based tumors are termed <inaudible> cell tumors or gangliocytomas.

05:41 The other classification system is the location.

05:43 And again, we talked about five locations: the meninges, the pineal region, the pituitary, that CP angle, or Cerebellopontine angle and the peripheral nerve sheath.

05:55 There are also two other special locations that I want you to at least know about and the first is the clivus, which is the bony structure that lies just the anterior just in front of the brainstem, and the posterior fossa because some things occur there that we should think about.

06:08 And in each of these locations, we can think about two major tumors that occur in that location and should be included in our imaging differential diagnosis.

06:17 In the meninges, we think about meningiomas, the most common primary tumor of the brain, and a less common tumor called a hemangiopericytoma.

06:28 In the sella is the seat in the anterior part of the brain into which the pituitary lies. We think about two tumors.

06:36 Pituitary tumors, benign adenomas, and malignant cancers and craniopharyngioma.

06:43 The pineal region is a vestigial structure.

06:46 It lies in the roof of the cerebral aqueduct, and fourth ventricle.

06:50 And we think about two tumors, pineal parenchymal tumors, and germ cell tumors.

06:55 Are really neat tumor that can occur in younger individuals and be very responsive to treatment.

07:00 In the cerebellopontine angle, we say AMEN, because we see Acoustic schwannomas, Meningiomas, Epidermoid cyst, and Facial Neuromas, or nerve sheath tumors, Nerve schwannomas.

07:13 So in the CP angle we say, AMEN.

07:17 In the Nerve sheath, we see two tumors.

07:19 That are nerve sheath tumors. Neurofibromas and Schwannomas.

07:23 In the clivus, we also think about two tumors chordomas, which are a mesenchymal based tumor that occur in the bones and osseous metastasis, metastasis to the bone.

07:35 And then finally, in the posterior fossa, we divide tumors into those that occur in adults and children.

07:41 In children, we think of medullablastoma, it is an important tumor in kids as well as pilocytic astrocytomas and ependyomomas.

07:48 And in adults, we think of brain metastasis, astrocytomas, and hemangioblastomas.

07:55 So that's an overview of the types of tumors that we'll consider.

07:59 And in the subsequent lectures, we'll dive into each of these in more detail so that you can understand how they present and how we may treat them in patients.