Brain Surgery Information:

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CHAPTER 4: TYPES OF BRAIN DISORDERS

There are a wide variety of brain disorders. Many of these require a neurosurgeon. Note that what doctors refer to as a lesion may be any structural abnormality such as a tumor, an inflammatory plaque, a blood clot or hematoma, or an aneurysm or AVM. Brain disorders can be classified as follows, with examples:

·  Vascular: Pertaining to conditions affecting brain blood vessels. For example: Brain aneurysms which are balloon like outpouchings from brain vessels that can rupture or cause cerebral vasospasm following rupture (www.brain-aneurysm.com); AVMs which are abnormal communications between arteries and veins that can also rupture or cause seizures; cavernous malformations which are abnormal oozy sacs or caverns that progressively enlarge through microbleeds or microhemorrhages; and carotid artery stenosis, which refers to blockage of major arteries supplying the brain. Brain hemorrhage from uncontrolled blood pressure or hypertension can also occur.

·  Inflammatory: Pertaining to conditions which cause inflammation of the brain and its coverings. For example: Neurosarcoidosis, a peculiar chronic inflammatory condition of the CNS; vasculitis such as giant cell arteritis or moya moya disease, referring to inflammation of blood vessel walls that can cause blood vessels to shut down or bleed as part of a stroke; and multiple sclerosis, which is a chronic disease affecting CNS nerve conduction by damaging its white matter myelin. Also, following brain radiation, there may be some form of delayed inflammatory swelling within the brain referred to as radiation necrosis (RN). The swelling caused by RN can be so significant, it may be mistaken for regrowing or recurrent tumor.

·  Traumatic: Pertaining to injury to the brain following some form of mechanical injury such as a motor vehicle accident, assault, and so forth. Some types of traumatic brain injury (TBI) include contusions or bruising of the brain, subdural or epidural hematoma which refers to an expanding collection of blood or blood clot on the brain surface, in addition to skull fractures and hemorrhage within the brain itself. A particular type of brain injury known as diffuse axonal injury (DAI) involves multiple areas of shear injury to brain tissue, especially axons running in the white matter, from acceleration-deceleration and torquing events.

·  Congenital: Pertaining to conditions that an individual is born with, such as neurofibromatosis (NF), von Hippel Lindau (VHL) disease, and Chiari malformations. There may or may not be specific genetic disturbances associated with the congenital condition, and the condition itself may be diagnosed later in life when it becomes symptomatic. Certain hereditary conditions or disorders that are known to run in families due to some genetic abnormality, such as Marfan syndrome, osteogenesis imperfecta, and Ehler’s-Danlos syndrome may impact upon the CNS especially through brain aneurysm formation.

·  Metabolic: Pertaining to abnormalities of fluids and body ions or electrolytes such as sodium. Fluid and sodium imbalance conditions include the syndrome of inappropriate antidiuretic hormone secretion (SIADH), cerebral salt wasting (CSW), and diabetes insipidus (DI). These conditions can occur as the offshoots of other brain conditions, including TBI, brain tumors, brain surgery, and brain hemorrhage. Certain metabolic problems cause confusion or delirium, and can also cause coma. Metabolic problems causing delirium are said to be part of a metabolic encephalopathy. It should also be noted that abnormalities of hormone producing and releasing areas of the brain such as the hypothalamus and pituitary gland can also cause metabolic abnormalities with disturbance of body system functions. Many of these occur as a consequence of some sort of tumor or inflammatory condition affecting these critical brain areas.

·  Infective: Pertaining to infections of the CNS. Such infections may be viral, bacterial, fungal or parasitic, depending on the bug. Such infections can cause severe inflammation of the brain and its coverings, as part of encephalitis and meningitis, respectively. Islands of pus in the brain are called abscesses, while a collection of pus on the surface of the brain is called an empyema.

·  Neoplastic: Pertaining to tumors of the CNS. Tumors may be primary brain tumors such as gliomas or secondary tumors referred to as metastases that have spread to the CNS. Depending on their cell(s) of origin, primary CNS tumors may be classified as astrocytomas, ependymomas, Schwannomas, oligodendrogliomas, mixed oligoastrocytomas, paragangliomas, meningiomas, hemangioblastomas, germ cell tumors, lymphoma, medulloblastomas, gangliogliomas, and so forth. Such tumors may be benign or malignant, terminology that essentially reflects the speed or rate at which a tumor grows, its degree of brain-invasiveness, its curability or lack thereof, and its tendency to cause death. Examples of metastases include lung cancer and kidney or renal cancer. Interestingly, melanoma and lymphoma are examples of two tumors that can occur within the CNS as a primary tumor or can occur elsewhere in the body and spread secondarily to the CNS. Certain tumors that arise in the brain can spread or metastasize to the spinal cord or, very rarely, even spread outside of the CNS to other body organs.

·  Iatrogenic: These are conditions that are thought to be the result of a treatment or procedure or intervention, and include wound infections, fluid overload, and other treatment-related complications.

·  Miscellaneous: Conditions such as hydrocephalus and epilepsy are included here. Hydrocephalus refers to a relative increase in brain CSF, its accumulation causing a rise in brain pressure or intracranial pressure (ICP). A person may be born with hydrocephalus or it may occur later in life in conditions such as acquired communicating hydrocephalus, say from meningitis, and normal pressure hydrocephalus (NPH). Alternatively, obstructive or noncommunicating hydrocephalus is generally acquired in that it occurs as a consequence of some other disease process, such as a brain tumor that obstructs the normal flow of CSF in the CNS. Epilepsy refers to a seizure or “fit” disorder of one kind or another. Epilepsy may certainly occur as part of a congenital abnormality, or it may somehow be acquired, say in mesial temporal sclerosis, or a seizure-generating brain tumor or AVM.