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.

THE END