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Central Nervous System
Central Nervous System
Central nervous system (CNS)– includes the brain and spinal cord
Peripheral nervous system (PNS)–composed of the cranial and spinal nerves
Autonomic system – comprises the sympathetic and parasympathetic system (controls smooth muscle action)
Central nervous system
Comprised of the brain and the spinal cord together with the nerve trunks and fibers connected to them.
Referred to as the cerebrospinal system.
Divisions of the Brain
Forebrain –cerebrum and diencephalon
Midbrain –mesencephalon
Hindbrain –cerebellum,pons and the medulla oblongata (sometimes called the brain stem)
Forebrain
Divided into two hemispheres
Each hemisphere is divided into four lobes
Midbrain
The upper part of the brain stem
Connects the lower brain centers to the higher brain centers
Hindbrain
Cerebellum (called little brain)
Pons
Medulla oblongata (Brain stem) –
The most posterior portion of the brain
Extension of the spinal canal
Peripheral Nervous System
31 pairs of spinal nerves
Attached to spinal cord
8 cervical
12 thoracic
5 lumbar
1 coccygeal
The rest control the lower extremities and extend below the level of the spinal cord
12 pairs of cranial nerves
Attached to brain
Autonomic Nervous System
Sympathetic system
Arises from all the thoracic and first 3 lumbar segments of the spinal cord
Parasympathetic system
Arises from the 3rd, 7th, 9th, and 10th cranial nerves and from the 2nd, 3rd, and 4th sacral segments of the spinal cord.
Special Imaging Procedures
CT – best demonstrates ventricular size or infarcts as well as the presence of blood. It is also good for bony abnormalities.
MRI – best demonstrates soft tissue abnormalities such as ruptured disk or spinal cord defects
Special Imaging Procedures Cont.
Nuclear Medicine – best demonstrates pathologic processes which involve the blood brain barrier.
Angiography – locates and evaluates aneurysms, intracranial mass, abnormal cranial vessels, hemorrhages and malformations.
Special Imaging ProceduresCont.
Myelography – confirms or excludes the presence of an intraspinal lesion such as a herniated disc.
Discography – demonstrates individual disc by injecting contrast.
Congenital Abnormalities
Anencephaly – the cranial vault is absent and the cerebral hemispheres are either missing or markedly reduce in size.
Congenital Abnormalities
Microcephaly – the infant is born with an exceedingly small head.
Usually related with the cerebrum failing to develop properly
Congenital Abnormalities
Hydrocephaly – (water brain) –the ventricles enlarge as a result of a block in the flow of cerebrospinal fluid at some level.
Usually diagnosed with ultrasound or MRI
Congenital Abnormalities
Spina Bifita – characterized by an opening in the spine, the result of a defect in the neural tube in which the posterior arches and spines of some vertebrae fail to close or are absent.
Inflammatory Processes
Abscesses – an accumulation of puss on the brain
Epidural abscess – collection of puss is between the skull and the underlying dura
Brain abscess – all other abscesses
Inflammatory Processes
Aneurysms – a weakening of the vessel wall which allows that wall to protrude outward and eventually rupture.
The most common type is a “berry aneurysm.
Inflammatory Processes
Cerebrovascular accidents (CVA)– also called strokes
Possible causes are thrombosis (blood clot), embolism (moving blood clot) and hemorrhage.
Inflammatory Processes
Transient Ischemic Attacks (TIAs) –often called “mini strokes” because they proceed CVAs.
They are the warning sign that a stroke is eminent
Inflammatory Processes
Subdural empyema – a pus forming process in the space between the dura mater and the arachnoid space.
Most commonly caused by spread of infection from the frontal or ethmoid sinuses.
Inflammatory Processes
Encephalitis – inflammation of the brain
Caused from a virus usually but can be caused from a hemorrhage.
Inflammatory Processes
Cerebral hemorrhage – (also known as hematoma) is the escape of blood from the vessels into the cerebrum. Subarachnoid hemorrhage – caused from a
ruptured berry aneurysm in the circle of Willis
Intracerebral or intraparenchymal –hypertensive vascular disease is the main cause
Inflammatory Processes
Meningitis – inflammation of the leptomeniges
Streptococcal meningitis – arises from the nose or throat area
Pneumococcal meningitis – arises from the lungs.
Head injuries
Concussion – when the brain strikes the opposite side of the head during a violent blow or jar.
Contusion – bruises on the surface of the brain
Head injuries cont
Fractures – break in the skull
Linear – irregular or jagged radiolucent line
Comminuted – a break of three or more pieces
Depressed – when the fragments are depressed into the cranial cavity.
Basilar skull fractures – breaks into the base of the skull
Head injuries
Epidural hemorrhage (extradural hematoma) – caused by a tear in the middle menigeal vessels, which causes bleeding between the bone and the dura mater.
Head injuries
Subdural hematoma – a tear of the veins between the dura mater and the arachnoid.
*Head injuries*
Intracerebral Hematoma – traumatic hemorrhage into the brain parenchyma
*Degenerative Diseases*
Alzheimer’s Disease (pre-senile dementia) – progressive cerebral atrophy that develops at an earlier age than the senile period.
*Degenerative Diseases*
Huntington’s Disease – an inherited condition that predominantly involves men in early to middle age. It presents as dementia and choreiform movements (involuntary movements that are rapid, jerky, and without stop.)
*Degenerative Diseases*
Parkinson’s Disease (shaky palsy) –progressive degenerative disease characterized by stooped posture, stiffness and slowness of movement, fixed facial expression, and involuntary rhythmic tremor of the limbs that disappears with voluntary movement.
Neoplasms
Glioma – originate in the cerebral hemispheres and the posterior fossa
Astrocytomas – benign form
Glioblastoma multiforme – malignant form
Neoplasms
Medulloblastoma – occurs in the roof of the fourth ventricle in the midline of the cerebellum.
Effects children between ages 9 and 12
Rapidly growing and usually result in death.
Neoplasms
Meningiomas – slow growing benign tumor arising in the meninges particularly the arachnoid and dura mater.
The most common brain tumor.
Neoplasms
Pituitary adenomas – a tumor that grows within the sellae turcica where the pituitary gland is located
Neoplasms
Craniopharyngioma – originates above the sellae turcica
Found in children between ages of 5 and 18
Neoplasms
Tumors of the pineal gland – cause a compression of the ventricular system causing hydrocephalus and an enlarged ventricular system.
Teratomas
Germinomas
Metastatic tumors
Chordoma – located at the clivus of the skull
Radiographically – reveals destruction of the dorsum sellae and clivus along with cloud like calcifications.
Metastatic Tumors
Acoustic neuromas – the origin at the 8th cranial nerve causes the tumor to destroy the internal auditory meatus
Usually associated with deafness.
Spinal Cord Disease
Neurofibromas – may occur any where in the spinal canal and are hallmarked by a foraminal widening
Spinal Cord Disease
Slipped disc – the most common abnormality of the spinal
When an intervertebral ;disc protrudes or herniates into the vertebral canal and presses on the spinal cord or stretch the nerves.
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