By O. Gamal. Syracuse University.
The diffusion- weighted SSFP sequence allows for a reliable differenti- ation of acute benign and neoplastic vertebral compres- sion fractures metoclopramide 10 mg low cost. On the diffusion-weighted SSFP sequence the benign fractures exhibited isointense or low signal in- tensity as compared to surrounding normal bone marrow 10 mg metoclopramide for sale, whereas metastatic vertebral compression fractures Fig buy 10mg metoclopramide overnight delivery. This probably reflects a of uninvolved bone marrow is decreased on unenhanced T1-w im- higher diffusion of water protons in acute benign frac- age (a) buy 10mg metoclopramide free shipping. Following Gadolinium application strong enhancement is tures with bone marrow edema in comparison to verte- visible at the level of the spondylitis as well in the not involved bral bodies filled with tumor cells. This reactive change represents marrow stimulation in chronic infection Reactive Changes of Bone Marrow Cellularity A replacement of fat cells by tumor cells or non-neo- plastic cells in hemolytic disorders with stimulation of Imaging focal Bone Marrow Abnormalities the bone marrow cells, increases the amount of water and Metastasis bound protons. This is accompanied by a diffuse decrease of bone marrow signal intensity (SI) on T1-weighted im- In the spine, a large field-of-view (500 mm) can only ages and an increased SI on STIR images, which can be be achieved using a spine phased array coil (Fig. At the spine, axial images are marrow cellularity may also be influenced by smoking, important for treatment planning because they show menstruation, hemolytic anemia, various drug therapies, the exact location in the vertebra and the relationship such as hematopoetic growth factor during chemotherapy to the pedicles, spinal canal and surrounding soft tis- or enzyme therapy e. Hematopoetic activity induced by As tumor nodules on T1-weighted spin-echo images growth factors can produce changes in bone marrow SI become obscured following Gadolinium application, fre- that may simulate bone marrow involvement by muscu- quency selective fat-suppressed sequences are necessary loskeletal tumors. Hematopoietic bone marrow hyperpla- to disclose focal lesions, especially when diffuse bone sia or reconversion has also been recognized in endurance marrow infiltration is also present (Fig. Cellularity may Signal intensity of GRE sequences is also dependent also be increased in patients suffering from chronic bac- upon magnetic susceptibility, allowing for differentiating terial infectious spondylitis (Fig. In these cases, tumor infiltration with and without trabecular destruc- MR imaging signal intensity alterations are probably due tion. This situation can be found in tumor infiltration of to reactive bone marrow stimulation. The subtraction placed by non-neoplastic stimulated, bone marrow cells, of fat and water signal on opposed GRE sequences pro- which are necessary for the production of white blood vides a perfect background with low signal intensity to cells in chronic infection. Stäbler Imaging Diffuse Bone Marrow Abnormalities When there are diffuse abnormalities of the bone marrow signal in hematologic neoplasias and myeloproliferative diseases but no focal disease is present, a pathologic sig- nal intensity of the bone marrow can be overlooked. In this situation, a homogenous diffuse decrease of signal intensity over all vertebral bodies on T1-weighted spin- echo images results from a homogenous replacement of fat cells by cellular marrow or an accumulation of iron in the bone marrow in hemolytic disorders. In the presence of diffuse neoplastic bone marrow in- filtration or bone marrow stimulation, low homogenous SI on T1-weighted images is seen, in addition to increased SI on STIR-images. The percentage enhancement following Gadolinium injection is increased (Fig. On the STIR-image multiple metastasis are outlined with high signal intensity. The lo- cation of the metastasis, which is of risk for a neuro- logic complication by com- pressing the spinal cord, is easily recognized a b Fig. Diffuse neoplastic bone marrow infitration in a patient enhanced T1-weighted image (a). On unenhanced T1-weighted image a diffuse quency selective fat suppression creates a low intensity back- low SI is present in all vertebrae (a). Gadolinium enhancement is ground to highlight the enhancing metastasis (b) heavily increased indicating the diffuse tumor infiltration (b) Bone Marrow Disorders 79 Multiple Myeloma The “salt-and-pepper” pattern is characterized by an irregular bone marrow structure with irregular areas of Multiple myeloma is characterized by bone marrow infil- high and low signal intensity on T1-weighted spin-echo tration with neoplastic plasma cells. Hyperintense areas cretory and Bence Jones plasmacytoma, these cells pro- on T1-weighted spin-echo images represent focal fat de- duce monoclonal immunglobulins, recognizable in serum posits, whereas hypointense areas correlate with electrophoresis. The “salt-and-pepper” pattern correlates up to ten years in cases of smoldering myeloma. Bone marrow biopsy is essential for diagnosis of mul- When minimal plasma cell infiltration is present, this tiple myeloma and gives direct proof for atypical plasma is usually accompanied by a normal or even increased cells. Because of the small size of the biopsy sample, amount of marrow fat cells. In malignant tumors with dif- however, the result is not always representative of the en- fuse bone marrow infiltration, there is rapid displacement tire bone marrow, especially in cases of nodular involve- of fat cells by tumor cells.
Absence seizures may disappear spontaneously with age buy 10mg metoclopramide mastercard, although some Diagnosis of Epilepsy individuals who have had absence seizures later go on to develop tonic-clonic seizures generic 10 mg metoclopramide. Individuals who are having a seizure for the ﬁrst time usually undergo medical Partial Seizures evaluation by a neurologist to determine whether the seizure is a symptom of an When nerve cells discharge in an isolat- acute medical or neurological illness that ed part of the brain trusted metoclopramide 10mg, partial seizures occur buy discount metoclopramide 10mg. Exten- and symptoms are very localized, depend- sive physical examination and blood tests ing on the part of the brain affected. One are usually part of initial screening, as well type of focal seizure, a Jacksonian (simple- as a detailed history of the precipitating partial) seizure, begins with convulsive factors that appeared to trigger the seizure. The convulsive muscle seizure, or when other symptoms or his- Conditions Affecting the Brain 63 tory indicate that epilepsy may be the nausea, dizziness, clumsiness, visual difﬁ- cause of seizure activity, a more extensive culty, or fatigue. A pri- Once medication for treatment of mary diagnostic tool for evaluating indi- seizures has begun, it is generally main- viduals after seizures is electroencephalo- tained for at least two years, regardless of graphy (EEG), a noninvasive procedure in whether the individual has remained which the electrical activity of the brain seizure free (Browne & Holmes, 2001). Magnetic resonance there have been no recurrent seizures after imaging (MRI), a noninvasive procedure in this time, the physician may consider which rapid detailed pictures of body withdrawing the medication. Individuals structures are produced, may also be used who have had no additional seizures after to identify structural anomalies in the beginning the medication, or who have brain that may be related to seizures. Treatment and Management of Epilepsy The consequences could be dangerous and at times life-threatening. Consequently, Treatment of epilepsy is dependent on the individuals should never attempt to alter cause of the seizure activity and the types or discontinue their medication without of seizures experienced. Al- the type of seizure and on whether more though they may be thoroughly evaluat- than one type of seizure is experienced. Based tion to remove or repair the abnormality on medication blood level and its effec- may be indicated. In most instances, how- tiveness in controlling seizure activity, the ever, when epilepsy is diagnosed, the stan- physician may alter medication dosages dard treatment of most types of seizures accordingly. Measuring the blood levels of is the regular use of one or more anticon- the anticonvulsant also helps the physi- vulsant or antiepileptic medications. Successful con- compliant with taking anticonvulsant med- trol of seizures, however, requires the indi- ications, seizures remain uncontrolled. The anticonvul- several seizures a month or, at times, sev- sant medications used to treat epilepsy are eral seizures a day, despite following a also not without side effects, and toxic strict treatment regimen of medication. Depending on the medication, cannot be controlled by medication, sur- side effects can include gum overgrowth, gery may be recommended to treat epilep- 64 CHAPTER 2 CONDITIONS OF THE NERVOUS SYSTEM: PART I sy. Under these circumstances, surgery well controlled seizures are, individuals may involve removing a portion of the live with the possibility, even if remote, brain structure, resecting a portion of the that another seizure will occur. The time, brain, or disconnecting the affected por- place, and social circumstances under tion from the rest of the brain. The amount If individuals experience a seizure in pub- of disability experienced, if any, after this lic, they risk feelings of embarrassment type of surgery depends on individual cir- and onlookers’ potential misperception of cumstances. Alcohol can lower the seizure threshold At times, even when seizures are adequate- and therefore precipitate seizures. Alcohol ly controlled, anxiety over the possibility and antiepileptic medications may also of having a seizure or other psychosocial interact and cause untoward effects. Con- dysfunction may be the most disabling sequently, individuals with epilepsy should factor associated with the condition. A medical ment and emotional development depend identiﬁcation bracelet should be worn by on when the diagnosis of epilepsy is made individuals with epilepsy at all times. When epilepsy is diagnosed in child- with epilepsy depends on the type of hood, parental feelings of fear, anxiety, seizure, the underlying cause, the admin- guilt, overprotectiveness, or mourning istration of appropriate treatment, and the can affect not only the child’s ability to individual’s willingness and ability to fol- accept his or her disability but also his or low the prescribed treatment regimen. Children may learn als with epilepsy can live active, produc- to use their condition as an excuse for in- tive lives. When medical intervention can greatly improve they are teenagers, concerns related to the ability to control seizures and enhance whether they will drive a car, participate in the general quality of life for the individ- sports, or engage in dating may cause addi- ual with epilepsy. Diagnosis of epilepsy in adulthood can Psychosocial Issues in Epilepsy also disrupt interpersonal and family rela- tionships. The impact on individuals’ Individuals with epilepsy may face social identity may be threatened, so that many psychological and psychosocial they go to great lengths to conceal their challenges. They must learn to deal with disability in order to avoid potential the uncertainty of whether and when rejection.
The venous return curve for right atrial pressures below 0 15 B mm Hg is not sensitive to right atrial pressure (see Fig metoclopramide 10mg fast delivery. Instead of continuing to increase as right atrial pressure falls generic metoclopramide 10 mg line, venous return levels off discount 10mg metoclopramide overnight delivery. Venous return does 10 not increase because buy metoclopramide 10 mg cheap, when right atrial pressure drops be- low zero (atmospheric pressure), the large veins collapse as they enter the chest. This is because the pressure in the A lungs surrounding the veins is close to atmospheric pressure 5 and the transmural pressure gradient favors collapse of the MCFP MCFP = 7 = 16 veins. The suction imposed by further drops in right atrial pressure further collapses the large veins, instead of sucking 0 more blood into the chest. No matter how low right atrial -4 0 +4 +8 +12 +16 pressure gets, venous return hardly increases. The Starling curve relating car- provides a level of ventricular filling adequate to produce diac output to right atrial pressure is shown in black. Note that venous return is zero when right atrial pressure equals the mean circulatory filling pressure (7 mm return, and cardiac output is not fixed. The dashed red line shows the venous return curve af- creased blood volume, and filling of the heart is increased. Filling of the cardiovascular sys- This increases cardiac output from point A to point B, along tem by the extra volume of blood raises mean circulatory filling an unchanged cardiac output curve. The slope of the venous return curve is volume further fills the cardiovascular system and increases also changed by the transfusion. The unique right atrial pressure that gives tionship between right atrial pressure and venous return, as equal venous return and cardiac output (point B) is now 8 mm shown by the dashed line. The transfusion raises cardiac output and venous return from 5 to 13 L/min. It also changes the slope of the venous return curve for reasons not discussed here. The unique right atrial pressure at which tion of the venous return curve for right atrial pressures venous return is equal to cardiac output is now 8 mm Hg. In this example, when right Other factors that influence the relationship between car- atrial pressure reaches 7 mm Hg, venous return stops. Gen- diac output, venous return, and right atrial pressure include erally, when right atrial pressure reaches the mean circula- venous resistance to venous return, changes in sympathetic tory filling pressure, venous return stops. Mean arterial pressure changes if with no change in heart rate items or incomplete statements in this (A) Heart rate increases, with no 3. Blood pressure measured using a section is followed by answers or by changes in cardiac output or systemic sphygmomanometer completions of the statement. Select the vascular resistance (A) May be falsely low with too ONE lettered answer or completion that is (B) Stroke volume changes, with no narrow a cuff BEST in each case. Mean arterial pressure equals (C) Arterial compliance changes, with (C) May be falsely high in obese (A) Arterial compliance times stroke no changes in cardiac output or patients volume systemic vascular resistance (D) Gives a direct reading of mean (B) Heart rate times stroke volume (D) Heart rate doubles and systemic arterial pressure (C) Cardiac output times systemic vascular resistance is halved, with no (E) Depends on the disappearance of vascular resistance change in stroke volume sound to signal systolic pressure (D) Cardiac output times arterial (E) Arterial compliance doubles and 4. In the systemic circulation, vascular compliance systemic vascular resistance is halved, resistance (continued) CHAPTER 15 The Systemic Circulation 261 (A) Changes occur mainly in the aorta pressure of 150/90 mm Hg and a right (A) Less than normal and large arteries atrial pressure of 3 mm Hg develops an (B) Greater than normal (B) Is altered more by changes in blood incompetent tricuspid valve, and right (C) The same as normal viscosity than radius atrial pressure rises to 13 mm Hg with (C) Is altered more by changes in no change in arterial pressure. The SUGGESTED READING vessel radius than length pressure gradient forcing blood Coleman TG, Hall JE. Systemic hemody- (D) Is altered more by changes in through the systemic circulation namics and regional blood flow regula- vessel length than radius (A) Is unchanged tion. Baltimore: Lippincott (A) Decreased diameter of leg veins (C) Increased from 103 to 113 mm Hg Williams & Wilkins, 1999. Systemic hypertension: (E) Decreased central blood volume to an increase in systemic vascular Mechanisms and diagnosis. If a person has an arterial blood resistance) and stroke volume and wald E, Zipes DP, Libby P, eds. Heart pressure of 125/75 mm Hg, heart rate remain constant, the pulse Disease.
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