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 * __ALTERATIONS IN NEUROLOGIC FUNCTION__**

Alterations in central nervious system function are caused by traumatic injury, vascular disorders, tumor growth, infectious and inflammatory processes, metabolic derangements and degenerative processes.

__**CENTRAL NERVOUS SYSTEM DISORDERS:**__

__Brain trauma__ is defined as a traumatic insult to the brain capable of producing physical, intellectual, emotional, social, and vocational changes. Head injuries are broadly categorized into blunt and open trauma.
 * //Trauma//**:

__Blunt trauma__ involves the head striking a hard surface or a rapidly moving object striking the head. It may result in both focal brain injuries and diffuse axonal injuries. __Open trauma__ occurs when a break in the dura mater results in exposure of the cranial contents to the environment. Most traumatic brain injuries are caused by motor vehicle accidents and falls. Objects striking the back of the head usually result in both **coup** (directly below the point of impact) and **contrecoup** (on the pole opposite the site of impact) injuries because of the irregularity of the inner surface of the frontal bones (ie: shaken baby syndrome).

__Compound fractures__ are caused by objects striking the head with great force or by the head striking an object forcefully. __Basilar skull fractures__ result from the cervical vertebrae upwardly impacting the base of the skull. __Focal brain injury__ is specific, grossly observable brain lesions - cortical contusions, epidural hemorrhage, subdural hematoma, and intracerebral hematoma. __Epidural hematomas__ represent 1-2% of major head injuries and occur in all age groups. An artery is the source of bleeding in 85% of these incidents. __Subdural hematomas__ arise in 10-20% of persons with traumatic brain injury. Acute subdural hematomas rapidly develop and usually are located at the top of the skull. __Intracerebral hematomas__ occur in 2-3% of persons with head injuries, may be single or multiple and are associated with contusions. Diffuse brain injury results from a shaking effect. Rotational acceleration is the primary mechanism of injury. __Mild concussion__ involves temporary axonal disturbances. They are graded as: Grade I, II or III. __Classic cerebral concussion__ involves diffuse cerebral disconnection from the brain stem reticular activating system and is a phenomenon of many aspects.

In __mild diffuse axonal injury__, posttraumatic coma lasts 6 to 24 hours. In __moderate diffuse axonal injury__, widespread phsiologic impairment exists throughout the cerebral cortex and diencephalon. __Severe diffuse axonal injury__ involves severe mechanical disruption of many axons in both cerebral hemispheres and those extending to the diencephalon and brain stem.

__Spinal cord trauma__ most commonly occur because of vertebral injuries, which are the result of acceleration, deceleration, or deformation forces most frequently applied at a distance. //Mechanisms of vertebral injuries//: hyperextension, hyperflexion, vertical compression and rotational forces. //Spinal cord injuries// are: cord concussion, cord contusion, cord compression, laceration, transection complete or incomplete, hemorrhage and damage or obstruction of spinal blood supply.

__Autonomic hyperreflexia__ is a syndrome that may occur at any time after spinal shock resolves. It is characterized by paroxysmal hypertension, pounding headache, blurred vision, sweating above the level of the lesion with flushing of the skin, nasal congestion, nausea, piloerection caused by pilo motor spasm, and bradycardia.


 * __DEGENERATIVE DISORDERS OF THE SPINE__**

__Degenerative disk disease__ is a common finding in individuals 30 years of age and older. Symptoms result from either (1) disk or annulus protrusion or (2) narrowing of the spinal canal or intervertebral forame by osteophytes. __Spondylolysis__ is a degenerative porcess of the vertebral column and associated soft tissue. Characterized by a structural defect of the spine involving the lamina or neural arch of the vertebrae. __Spondylolisthesis__ is a stress factor allowing vertebrae to slide forward in relation to the vertebrae below, commonly occurring at L5-S1. __Spinal stenosis__ - the canal may be congenitally narrowed or narrowed by a bulging annulus, a facet hypertrophy, or a thick/ossified posterior longitudinal ligament entrapping a single nerve involving many roots. __Low back pain__ affects the area between the lower rib cage and gluteal muscles and often radiates into the thighs. __Herniated intervertebral disk__ is a protrusion of part of the nucleus pulposus through a tear in the posterior rim of the annulus fibrosus.


 * __CEREBROVASCULAR DISORDERS__**

Cerebrovascular disease is the most frequently occurring neurologic disorder. The brain abnormalities induced by cerebrovascular disease are of two types: (1) ischemia with or without infarction and (2) hemorrhage. The common clinical manifestation of cerebrovascular disease is a CVA. A CVA is a sudden, nonconvulsive focal neurologic deficit.

__Risk factors__ for stroke include the following: arterial hypertension, smoking, diabetes, insulin resistance, polycythemia and thrombocythemia, elevated lipoprotein, impaired cardiac function, hyperhomocysteinemia, nonrheumatic atrial fibrillation and chlamydia pneumoniae.

__Thrombotic strokes__ arise from arterial occlusions caused by thrombi formed in the arteries supplying the brain or in the intracranial vessels. __Transient ischemic attacks__ (TIA) represent thrombotic particles causing an intermittent blockage of circulation or spasm. __Embolic strokes__ involve fragments that break from a thrombus formed outside the brain or in the heart, aorta, common carotid, or thorax. __Hemorrhagic stroke__ is the thrid most common cause of CVA and the most common causes are hypertension, ruptured aneurysms, vascular malformations, bleeding into a tumor, hemorrhage associated with bleeding disorders or anticoagulation, head trauma, and illicit drug use. __Lacunar strokes__ are microinfarcts smaller than 1cm in diameter and involve the small perforating arteries, predominantly in the basal ganglia, internal capsules, and pons. __Cerebral infarction__ results when an area of the brain oses blood supply because of vascular occlusion. __Cerebral hemorrhage__ primary cause is hypertension. A mass of blood is formed as bleeding continues into the brain tissue. Adjacent brain tissue is displaced and compressed, producing ischemia and subsequent vasogenic edema. __Intracranial aneurysm__ may result from arteriosclerosis, congenital abnormality, trauma, inflammation, or infection. __Vascular malformations__ are 1/10 as common as aneurysms. Four types exist: arteriovenous malformation, cavernous angioma, capillary telangiectasis and venous angioma. __Subarachnoid hemorrhage__ is when blood escapes from a defective or injured vasculature into the subarachnoid space. __Headache__ is a common neurologic disorder and is usually a benign symptom. Often reoccurring and provoked by a trigger factor. //Cluster headaches// occur primarily in men between 20 & 50 years of age. These are known as such because several headaches can occur during the day for a period of days followed by a long period of spontaneous remission. //Chronic paroxysmal hemicrania// is a cluster type of headache that occurs with more daily frequency but with shorter duration. //Tension type headache// is the most common type of headache. It is a mild to moderate bilateral headache with a sensation of a tight band or pressure around the head.
 * //cavernous angiomas// are sinusoidal collections of blood vessels without interspersed normal brain tissue.
 * //capillary telangiectasis// is dilated capillaries with interspersed normal brain tissue found deep in the brain, particularly in the brain stem.
 * //venous angioma// is the most common vascular malformation found; is considered a subset of developmental venous anomalies that occur secondary to arrested development.
 * //arteriovenous malformation// - arteries feed directly into veins through a vascular tangle of malformed vessels.


 * __TUMORS OF THE CENTRAL NERVOUS SYSTEM__**

//**Cranial tumors**// are tumors within the crainium and can be either primary or metastatic. Primary tumors are either intracerebral tumors or primary extracerebral tumors. //Primary intracerebral tumors// originate from brain substance, neuroglia, neurons, cells of the blood vessels, and connective tissue. //Primary extracerebral tumors// originate outside the substance of the brain and include meningiomas, acoustic nerve tumors, and tumors of the pituitary and pineal glands. //Metastatic tumors// or secondary tumors, can be found inside or outside the brain substance.

//Primary Intracerebral tumors//, also called gliomas, comprise 50-60% of all adult brain tumors and are both encapsulated and nonencapsulated or invasive tumors. //Astrocytomas// are the most common primary CNS tumors. Oligodendroglioma, comprises 2% of all brain tumors. They are typically slow-growing, well-differentiated tumors, often with cysts and calcification present. //Ependymomas// are gliomas that arise from ependymal cells that form the walls of the ventricles and grow either into the ventricle or into adjacent brain tissue; they are not encapsulated.

//Primary Extracerebral tumors// //Meningioma// are considered benign because they are encapsulated and usually do not invade the surrounding brain. They originate from the dura mater or arachnoid cells of the choroid plexus of the ventricles. //Nerve sheath tumors// are eigher neurofibroma or schwannoma. //Metastatic carcinoma// - an estimated 25% of persons with cancer develop metastasis to the brain. One half of these tumors arise from the lung.

//**Spinal Cord tumors**// are relatively rare. They are named to reflect their cell type, growth rate, and structure of origin. They are classified as intramedullary or extramedullary tumors.


 * __INFECTION AND INFLAMMATION OF THE CENTRAL NERVOUS SYSTEM__**

The CNS may be affected directly by bacteria, viruses, fungi, protozoans, and rickettsiae. The //cardinal signs// of CNS infection are fever, head or spine pain, and generalized or focal neurological dysfunction.

//Meningitis// may be caused by bacteria, viruses, fungi, parasites, or other toxins. They are classified as acute, subacute, or chronic processes. //Bacterial meningitis// is primarily an infection of the pia mater and arachnoid, the subarachnoid space, the ventricular system, and the CSF. //Aseptic meningitis// (viral meningitis) is an inflammation believed to be limited to the meninges. //Fungal meningitis// is a chronic, much less common condition than bacterial or viral meningitis. //Tubercular meningitis//, the most common and serious form of CNS tuberculosis, is again on the rise in the US, especially in persons with acquired immunodeficiency syndrome.

//Suppurative cerebral masses// are localized pus-filled masses; they may be an abscess within the brain or spinal cord, a subdural empyema with the infection between the dura and the subarachnoid space, or an epidural abscess with the infection between the dura and skull or vertebrae. //Abscesses// are localized collections of pus within the parenchyma of the brain and spinal cord. Spinal cord abscesses are classified as eipdural or intramedullary. //Encephalitis// is an acute febrile illness, usually of viral origin, with nervous system involvement. The most common encephalitides are caused by arthropod-borne viruses and herpes simplex (type I).

//Neurologic complications of AIDS//: //Human Immunodeficiency-Associated Cognitive Dysfunction// may affect both adults and children and is characterized by progressive cognitive dysfunction in conjunction with motor and behavioral alterations. //HIV myelopathy// may occur in persons with AIDS. //Vacuolar myelopathy// is believed to be a direct consequence of HIV. //HIV neuropathy// may have one or a combination of several presentations: predominantly sensory neuropathy, an autonomic neuropathy, a mononeuritis multiplex, a Guillian-Barre' like syndrome, and a myopathy. //Aseptic viral meningitis// - this may well respresent the initial infection of the nervous system by the HIV. Opportunistic infections may be bacterial, fungal, protozoan, or viral in origin and produce nervous system disease. //Cytomegaloviris infection// - encephalitis is common in persons with AIDS but often not diagnosed while the person is alive. //Parasitic infection// - toxoplasmosis is the most common opportunistic infection. It typically manifests as focal encephalitis. //Central nervous system neoplasms// associated with AIDS include primary CNS lymphoma, systemic non-Hodgkin lymphoma, and metastatic Kaposi sarcoma. //Other CNS complications// - persons with AIDS may develop multifocal ischemic infarctions, hemorrhagic infarctions, hemorrhage into tumors, subdural hematomas, and eipdural hemorrhage.

//Lyme disease//, a tick-borne spirochette bacterial infection, is a common arthropod-borne infection. http://www.lib.uiowa.edu/hardin/md/pictures22/dermnet/lyme_disease_06.jpg

//Multiple sclerosis// is a relative common dysimmune dieorder diffusely involving the CNS myelin. The major classifications of MS are relapsing-remitting, primary progressive, secondary progressive, and progressive-relapsing. Usually persons with late MS have predominantly one of the established syndromes - mixed, spinal or cerebellar. //Mixed (general) type// - 25% of persons initially experience retrobulbar or optic neuritis, the manifestations of optic nerve demyelination. //Spinal type// is the second most common type, chiefly involving the spinal tracts and dorsal column. //Cerebellar type// - a nystagmus and ataxia presentation initially is not uncommon and reflects cerebellar and cortiocospinal involvement.
 * //Demyelinating disorders://**


 * __PERIPHERAL NERVOUS SYSTEM AND NEUROMUSCULAR JUNCTION DISORDERS__**

//Peripheral nervous system disorders:// //__Neuropathies__// - generalized neuropathies affect the cell body of only one type of peripheral neuron. The dorsal root ganglion cell is affected in sensory neuropathies producing numbness that may begin in a focal or asymmetric distribution or in a distal symmetric pattern. //Sensory neuropathies// are seen in leprosy, some industrial solvent poisonings, some hereditary disorders, and chloramphenicol toxicity. //Focal or multifocal neuropathies// affect sensory and motor fibers in one or more nerves as is seen in common compression neuropathies such as carpal tunnell, ulnar nerve compression, peroneal nerve compression, or sciatic nerve compression. //Guillain-Barre' syndrome// is an acquired inflammatory disease that results in demyelination of the peripheral nerves with relative sparing of axons. Characterized by the acute onset of a motor paralysis, usually of an ascending nature. //Amyotrophic lateral sclerosis// (ALS) is a worlwide degenerative disorder diffusely involving lower and upper motor neurons resulting in progressive muscle weakness leading to respiratory failure and death. //Classic ALS (Lou Gehrig disease)// may begin at any time from the fourth decade of life; it peaks in the 50's. //Radiculopathies// are disorders of roots of spinal nerves. Radiculitis refers to an inflammatory disorder of the spinal nerve roots. //Plexus injuries// involve the nerve plexus distal to the spinal roots but proximal to the formation of the peripheral nerves.

//Neuromuscular Junction disorders: Myasthenia gravis// is a chronic autoimmune disease mediated by antiacetylcholine receptor antibodies that act at the neuromuscular junction. There are three classifications: //Myastenic crisis// occurs when severe muscle weakness causes extreme quadriparesis or quadriplegia, resp. insufficiency with shortness of breath and markedly decreased tidal volume and vital capacity, and extreme difficulty in swallowing. //Cholinergic crisis// may arise secondary to drug overdose. //Myopathies// is the term applied to a primary muscle disorder.
 * neonatal myasthenia - onset of signs is 1 to 3 days after birth and persist for a few days to a few weeks.
 * congenital myasthenia presents in infancy and continues into adulthood.
 * juvenile myasthenia is an autoimmune disorder with a childhood onset usually about 10 years of age
 * ocular myasthenia is more common in males and includes muscle weakness of the eye muscles and eyelids and may include swallowing difficulties and slurred speech.
 * generalized autoimmune myasthenia involves the proximal musculature throughout the body and has several courses.

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