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By Z. Vigo. Globe Institute of Technology.

This is an exam ple of 68 ASSESSIN G M ETH OD OLOG ICAL QU ALITY performance bias which generic lady era 100 mg with mastercard pregnancy over 40, along with other pitfalls for the unblinded assessor lady era 100mg for sale women's health center roseville ca, is listed in Figure 4. An excellent exam ple of controlling for bias by adequate "blinding" was published in the Lancet a few years ago. The discrepancy between this trial and its predecessors m ay have been due to M ajeed and colleagues’ m eticulous attem pt to reduce bias (see Figure 4. N either the patients nor their carers were aware of which operation had been done, since all patients left the operating theatre with identical dressings (com plete with blood stains! These findings challenge previous authors to ask them selves whether it was expectation bias (see section 7. As a non-statistician, I tend only to look for three num bers in the m ethods section of a paper: 1. Sample size One crucial prerequisite before em barking on a clinical trial is to perform a sam ple size ("power") calculation. In the words of statistician D ouglas Altm an, a trial should be big enough to have a high chance of detecting, as statistically significant, a worthwhile effect if it exists and thus to be reasonably sure that no benefit exists if it is not found in the trial. You could adm inister a new drug which lowered blood pressure by around 10 m m H g and the effect would be a statistically significant lowering of the chances of developing stroke (i. If the outcom e in question is an event (such as hysterectom y) rather than a quantity (such as blood pressure), the item s of data required are the proportion of people experiencing the event in the population and an estim ate of what m ight constitute a clinically significant change in that proportion. Once these item s of data have been ascertained, the m inim um sam ple size can be easily com puted using standard form ulae, nom ogram s or tables, which m ay be obtained from published papers,15, 18 textbooks,19 or com m ercial statistical software packages. H ence, when reading a paper about a RCT, you should look for a sentence which reads som ething like this (which is taken from M ajeed and colleagues’ cholecystectom y paper described above): "For a 90% chance of detecting a difference of one night’s stay in hospital using the M ann-W hitney U -test [see Chapter 5, Table 1], 100 patients were needed in each group (assum ing SD of 2 nights). This 70 ASSESSIN G M ETH OD OLOG ICAL QU ALITY gives a power greater than 90% for detecting a difference in operating tim es of 15 m inutes, assum ing a SD of 20 m inutes. U nderpowered studies are ubiquitous in the m edical literature, usually because the authors found it harder than they anticipated to recruit their subjects. If the authors were looking at the effect of a new painkiller on the degree of postoperative pain, their study m ay only have needed a follow up period of 48 hours. On the other hand, if they were looking at the effect of nutritional supplem entation in the preschool years on final adult height, follow up should have been m easured in decades. Even if the intervention has dem onstrated a significant difference between the groups after, say, six m onths, that difference m ay not be sustained. As m any dieters know from bitter experience, strategies to reduce obesity often show dram atic results after two or three weeks but if follow up is continued for a year or m ore, the unfortunate subjects have (m ore often than not) put m ost of the weight back on. Completeness of follow up It has been shown repeatedly that subjects who withdraw from ("drop out of") research studies are less likely to have taken their tablets as directed, m ore likely to have m issed their interim check ups, and m ore likely to have experienced side effects on any m edication than those who do not withdraw. People on a weight reducing program m e are m ore likely to continue com ing back if they are actually losing weight. N ote that you should never look at the "adverse reaction" rate in the intervention group without com paring it with that on placebo. Clearly, patients who die will not attend for their outpatient appointm ents, so unless specifically accounted for they m ight be m isclassified as "dropouts". This is one reason why studies with a low follow up rate (say below 70% ) are generally considered invalid. Sim ply ignoring everyone who has withdrawn from a clinical trial will bias the results, usually in favour of the intervention. It is therefore standard practice to analyse the results of com parative studies on an intent to treat basis. Conversely, withdrawals from the placebo arm of the study should be analysed with those who faithfully took their placebo. If you look hard enough in a paper, you will usually find the sentence "Results were analysed on an intent to treat basis", 72 ASSESSIN G M ETH OD OLOG ICAL QU ALITY but you should not be reassured until you have checked and confirm ed the figures yourself. There are, in fact, a few situations when intent to treat analysis is, rightly, not used.

Magnetic Resonance Imaging Unlike CT and conventional MR order 100mg lady era amex womens health 8 week workout, new functional MR techniques such as diffusion-weighted imaging (DWI) allow detection of the earliest phy- siologic changes of cerebral ischemia cheap lady era 100mg women's health center of grants pass. Diffusion-weighted imaging, a sequence sensitive to the random brownian motion of water, is capable of demonstrating changes within minutes of ischemia in rodent stroke models (53–55). Moreover, the sequence is sensitive, detecting lesions as small as 4mm in diameter (56). Although the in vivo mechanism of signal alteration observed in DWI after acute ischemia is unclear, it is believed that ischemia-induced energy depletion increases the influx of water from the extracellular to the intracellular space, thereby restricting water motion, resulting in a bright signal on DW images (57,58). Diffusion-weighted imaging has become widely employed for clinical applications due to improvements in gradient capability, and it is now possible to acquire DW images free from artifacts with an echo planar approach. Because DW images are affected by T1 and T2 contrast, stroke lesions becomes pro- gressively brighter due to concurrent increases in brain water content, leading to the added contribution of hyperintense T2W signal known as "T2 shine-through. For stroke lesions in adults, although there is wide individual vari- ability, ADC signal remains decreased for 4 days, pseudo-normalizes at 5 168 K. This temporal evolution of DWI signal allows one to determine the age of a stroke. The high sensitivity and specificity of DWI for the detection of ischemia make it an ideal sequence for positive identification of hyperacute stroke, thereby excluding stroke mimics. Two studies evaluating DWI for the detection of ischemia within 6 hours of stroke onset reported an 88% to 100% sensitivity and 95% to 100% specificity with a positive predictive value (PPV) of 98. In another study, 50 patients were randomized to DWI or CT within 6 hours of stroke onset, and subsequently received the other imaging modality with a mean delay of 30 minutes. Sensitivity and speci- ficity of infarct detection among blinded expert readers was significantly better when based on DWI (91% and 95%, respectively) compared to CT (61% and 65%) (moderate evidence) (61). The presence of restricted diffu- sion is highly correlated with ischemia, but its absence does not rule out ischemia: false negatives have been reported in transient ischemic attacks and small subcortical infarctions (moderate evidence) (60,62–64). False- positive DWI signals have been reported in brain abscesses (65), herpes encephalitis (66,67), Creutzfeldt-Jacob disease (68), highly cellular tumors such as lymphoma or meningioma (69), epidermoid cysts (70), seizures (71), and hypoglycemia (72) (limited evidence). However, the clinical history and the appearance of these lesions on conventional MR should allow for exclusion of these stroke mimics. Within the first 8 hours of onset, the stroke lesion should be seen only on DWI, and its presence on conventional MR sequences suggests an older stroke or a nonstroke lesion. The DWI images, therefore, should not be interpreted alone but in con- junction with conventional MR sequences and within the proper clinical context. Acute DWI lesion volume has been correlated with long-term clinical outcome, using various assessment scales including the National In- stitutes of Health Stroke Scale (NIHSS), the Canadian Neurologic Scale, the Barthel Index, and the Rankin Scale (moderate evidence) (73–77). This correlation was stronger for strokes involving the cortex and weaker for subcortical strokes (73,74), which is likely explained by a discordance between infarct size and severity of neurologic deficit for small subcorti- cal strokes. In addition to DWI, MR perfusion-weighted imaging (PWI) approaches have been employed to depict brain regions of hypoperfusion. They involve the repeated and rapid acquisition of images prior to and follow- ing the injection of contrast agent using a two-dimensional (2D) gradient echo or spin echo EPI sequence (78,79). Signal changes induced by the first passage of contrast in the brain can be used to obtain estimates of a variety of hemodynamic parameters, including cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT, the mean time for the bolus of contrast agent to pass through each pixel) (79–81). These parame- ters are often reported as relative values since accurate measurement of the input function cannot be determined. Thus, hypoperfused brain tissue result- ing from ischemia demonstrates signal changes in perfusion-weighted images, and may provide information regarding regional hemodynamic status during acute ischemia (insufficient evidence). What Imaging Modality Should Be Used for the Determination of Tissue Viability—the Ischemic Penumbra? Summary of Evidence: Determination of tissue viability using functional imaging has tremendous potential to individualize therapy and extend the therapeutic time window for some. Several imaging modalities, including MRI, CT, PET, and SPECT, have been examined in this role. Operational hurdles may limit the use of some of these modalities in the acute setting of stroke (e. Rigorous testing in large randomized controlled trials that can clearly demonstrate that reestablishment of perfusion to regions "at risk" prevents progression to infarction is needed prior to their use in routine clinical decision making. Magnetic Resonance Imaging The combination of DWI and PWI techniques holds promise in identify- ing brain tissue at risk for infarction. It has been postulated that brain tissue dies over a period of minutes to hours following arterial occlusion.

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The mass is eroding the apex of the petrous bone and is extending to the cerebellopontine angle of the same side generic lady era 100mg on line breast cancer young women. Axial CT shows a space-occupying lesion of the right CP angle that occupies the right jugular foramen and demonstrates intense buy cheap lady era 100mg online womens health questionnaire, heterogeneous postcontrast enhancement. Axial CT shows a marked thickening of all bones of the skull base with reduction of the size of the posterior fossa. Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme All rights reserved. Eosinophilic granuloma Primary benign neoplasms – Pituitary adenoma May extend superiorly through the diaphragma sellae and laterally into the cavernous sinus – Meningioma Located alongside the sphenoid wing, diaphragma sellae, clivus, and cavernous sinus – Nerve sheath tumors! Plexiform neurofi- Diffusely infiltrating masses originating primarily bromas along the ophthalmic and the maxillary and mandibu- lar divisions of the trigeminal nerve! Schwannomas Cause one-third of primary trigeminal nerve and Meckel’s cavity tumors. Neurinomas of the third, fourth and sixth cranial nerves are rare – Juvenile angiofi- The most common benign nasopharyngeal tumor; broma highly vascular – Chordoma – Enchondroma The most common benign osteocartilaginous tumor in this area – Epidermoid tumors – Lipomas – Cavernous hemangi- omas Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme All rights reserved. Skull Base 127 Primary malignant neo- plasms – Nasopharyngeal carci- noma – Rhabdomyosarcoma – Multiple myeloma The most common primary bone tumor originating in the central skull base – Solitary plasmacy- toma – Osteosarcoma The second most common primary bone tumor after multiple myeloma – Chondrosarcomas Posterior skull base, Includes the clivus below the spheno-occipital syn- clivus chondrosis, the petrous temporal bone, the pars lat- eralis and squamae of the occipital bones, and sur- rounds the foramen magnum Lesions in the temporal bone Lesions in the foramen magnum Clival and paraclival le- sions – Chordoma Chordomas or chondrosarcomas usually originate from the sacrococcygeal region, the spheno-occipital region (40%), or the vertebrae. Both these tumors represent 6–7% of primitive skull base lesions, and they are very rare, representing only 0. Diagram of the cavernous sinus and its contents; the sellar, suprasellar, and parasellar structures Jugular foramen lesions – Neoplastic masses! Paragangliomas Chemodectomas or glomus tumors; parasympathetic paraganglia located in the jugular bulb adventitia and in various sites of the head and neck, especially the carotid body, glomus jugulare, and glomus tympani- cum! Nerve sheath Uncommon location tumors – Schwannomas of cranial nerves IX and XI – Neurofibromas – Epidermoid tumor Chondroid, chordo- ma lesions! Meningioma Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme All rights reserved. Skull Base 129 Nonneoplastic masses – Prominent jugular "Pseudomass"—normal variant bulb – Jugular vein thrombo- sis – Osteomyelitis Diffuse skull base le- sions Neoplastic masses – Metastases – Multiple myeloma, plasmacytoma – Meningioma – Lymphoma Primary or secondary; uncommon, but increasing in incidence, causing leptomeningeal disease and multi- ple cranial nerve palsies Nonneoplastic masses – Fibrous dysplasia The most common benign skeletal disorder in adoles- cents and young adults. In the most common monos- totic type, 25% of skull and facial bones are involved, compared with 40–60% in the polyostotic type, caus- ing facial deformities and cranial nerve palsies – Paget’s disease – Eosinophilic granulo- ma Cavernous sinus lesions (Fig. Choroid Plexus Disease Differential diagnosis: Tumors Choroid plexus papil- loma Choroid plexus carci- noma Meningioma Ependymoma, sub- ependymoma Neurofibroma Glioblastoma, astrocy- toma Oligodendroglioma Tuberous sclerosis, sub- ependymal giant-cell astrocytoma CNS lymphoma PNET E. Gliomatosis Cerebri 131 Nonneoplastic cysts Colloid cyst Rathke’s cleft cyst Neuroglial (neuroepi- thelial) cyst Vascular malforma- tions Choroid plexus angio- mas Phakomatosis E. Gliomatosis Cerebri This is a diffusely infiltrative neoplasm, with variably undifferentiated astrocytes and without a necrotic center. Gliomatosis cerebri presents as a diffuse involvement of the cerebral hemispheres, leading to progres- sive changes in personality, headaches, and impaired mental status. Positron-emission tomography (PET) scanning with methionine shows isotope accumulation in the diffusely infiltrative tumorous area, with greater accuracy than computed tomography or magnetic resonance imaging. Differential diagnosis: Low-grade glioma Oligodendroglioma Gliomatosis cerebri Leptomeningeal gliomatosis Encephalitis Diffuse and demyelinating disease Pseudotumor cerebri Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme All rights reserved. Sarcoidosis Meningioma Lymphoma Metastatic and neurotropic spread of tumor into the cavernous sinus Infections (e. In the differential diagnosis of an enlarging lesion at the site of a previously eradicated malignant glioma, the clinician should consider the follow- ing possibilities. Development of a dis- In cases of genetic predisposition to tumor develop- tinct new tumor ment shared by cells in the area: – Multiple gliomas in patients with tuberous sclerosis – Multiple neurofibromas developing along the same nerve root in patients with neurofibromatosis Growth of a tumor A tumor with related histopathology may supplant the with related pathology original tumor. Congenital Posterior Fossa Cysts and Anomalies 133 Nonneoplastic lesions Nonneoplastic lesions can mimic tumor growth: – Radiation necrosis after focal high-dose irradiation – Abscess formation at the site of the tumor resection Congenital Posterior Fossa Cysts and Anomalies Dandy–Walker com- In 70% of cases, the syndrome has a number of as- plex sociated anomalies, such as hydrocephalus, agenesis of the corpus callosum, nuclear dysplasia of the brain stem, and other cerebrocerebellar heterotopias Dandy–Walker malfor- Large posterior fossa and CSF cyst, high transverse mation sinuses and tentorial insertion, vermian, cerebellar hemispheric and brain stem hypoplasia in 25% of cases Dandy–Walker variant Mild vermian hypoplasia, moderately enlarged fourth ventricle although the posterior fossa is typically of normal size, the brain stem is normal, and there is a variable degree of vermian hypoplasia Other posterior fossa cysts Arachnoid and neuro- Arachnoid cysts are formed by a splitting of the epithelial cysts arachnoid membrane with layers of thickened fibrous connective tissue, whereas neuroepithelial or glio- ependymal cysts are lined with a low cuboidal-colum- nar epithelium Megacisterna magna The fourth ventricle appears normal and the vermis and cerebellar hemispheres are normal, but occa- sionally the posterior fossa can be enlarged, with prominent scalloping of the occipital bones Isolated fourth ventricle After ventriculoperitoneal shunt, leading to secondary aqueductal stenosis, but in addition the CSF outflow from the fourth ventricle is prevented, or its absorp- tion is prevented, e. SagittalT1WIshowingdilatationofthe4th ventricle and isodense signal with the cerebrospinal fluid. Coronal T1WI demonstrates a cystic space-occuping le- sion with a small postcontrast enhancing mural nodule. Axial T1WI with a solid extrinsic space-occupying mass with smooth margins and a relative heterogeneity, which causes smooth erosion of the occipital bone and exerts mild compression on the left cerebellar hemi- sphere. Coronal T1WI shows a solid extrinsic space-occupying mass with well-defined margins, it is non-contrast enhancing and causes erosion of the occipital bone. Miscellaneous cerebel- lar hypoplasias Chiari type IV malfor- Absent or severely hypoplastic cerebellum and small mation brain stem Joubert’s syndrome Split or segmented vermis, transmitted by autosomal recessive genes Rhombencephalo- Agenesis of the vermis and midline fusion of the cere- synapsis bellar hemispheres and peduncles Tectocerebellar dys- Vermian hypoplasia, occipito-encephalocele, and dor- raphia sal brain stem traction Lhermitte–Duclos dis- Gross thickening of the cerebellar folia, hypertrophy of ease or dysplastic cere- the granular cell layer, and axonal hypermyelination of bellar gangliocytoma the molecular cell layer CSF: cerebrospinal fluid. Proton density axial MRI T2WI presenting a cystic dilata- tion of the cisterna magna that communicates with the 4th ventricle.

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Other catheters used are C-1 and C-2 catheters buy lady era 100mg lowest price menstruation after menopause, Sidewinder I or II catheters cheap lady era 100mg with amex women's health center mccomb ms, or, by some experts, a steam-shaped 4-Fr catheter with a distal hook- shaped tip. An amount of 2 to 4 mL is injected within a second, and the angiogram is acquired in anterior–posterior projection. To reduce the time involved in placing the catheter and switching the contrast- filled syringe back and forth, it is recommended to have an assistant inject the contrast if an injector pump is not available. If injection by hand is preferred, the small syringe should be attached to a three-way stopcock, while another attached syringe, filled with 20 mL of contrast material, serves as a reservoir. The digitally subtracted angiographic run (acquisition) should be long enough to capture both the arterial and venous phases. If an intervention is planned and a 6-Fr guide catheter is preferred for the coaxial microcatheter placement, it may be helpful to place a 6- Fr femoral sheath or, if the region of interest is located higher, a long femoral sheath bypassing the often tortuous aortic–iliac system. Infre- quently, the guide catheter may require to be changed over an exchange wire for a stable position within the intercostal or lumbar artery. It is easier and less traumatic to use hydrophilic-coated exchange guide wires for straightening the proximal part of the segmental arteries. With the introduction of 5-Fr guide catheters with larger lumina, a larger catheter may not be required. A range of microcatheters, including flow-guided catheters and micro- wires, are available for interventional procedures. The selection must be tailored to the size of the vessel and the embolic material used. Heparin may be given for inter- ventional procedures, but only on rare occasions to prevent inadvertent thrombosis, especially if catheters are navigated within the spinal cord vasculature. In selected cases of high-flow AVMs that have blood supply from anterior or posterior spinal arteries, we put the patient on aspirin and/or Plavix to prevent a retrograde thrombosis after embolization. Niimi Y, Berenstein A (1999) Endovascular treatment of spinal vascular malformations. Oldfield EH, Bennett A III, Chen MY, Doppman JL (2002) Successful man- agement of spinal dural arteriovenous fistulas undetected by arteriogra- phy. Bao Y, Ling F (1997) Classification and therapeutic modalities of spinal vascular malformations in 80 patients. Touho H, Monobe T, Ohnishi H, Karasawa J (1995) Treatment of type II perimedullary arteriovenous fistulas by intraoperative transvenous em- bolization: case report. Spetzler RF, Zabramski JM, Flom RA (1989) Management of juvenile spinal AVMs by embolization and operative excision. Djindjian R (1978): Clinical symptomatology and natural history of arterio- venous malformations of the spinal cord: a study of the clinical aspects and prognosis based on 150 cases. Maraire JN, Awad IA (1997) Cavernous malformations: natural history and indications for treatment. Tampieri D, Leblanc R, Ter Brugge KG (1993) Pre-operative embolization of brain and spinal hemangioblastomas. Doppman, JL, Oldfield EH, Heiss JD (2000) Symptomatic vertebral he- mangiomas: treatment by means of direct intra-lesional injection of ethanol. A pathological entity com- monly mistaken for giant-cell tumor and occasionally for hemangioma and osteogenic carcinoma. Cigala F, Sadile F (1996) Arterial embolization of aneurysmal bone cysts in children. Gellad FE, Sadato N, Numaguchi Y, Levine AM (1990) Vascular metasta- tic lesions of the spine: preoperative embolization. Hilal SK, Michelsen JW (1975) Therapeutic percutaneous embolization for extra-axial vascular lesions of the head, neck, and spine. King GJ, Kostuik JP, McBroom RJ, Richardson W (1991) Surgical man- agement of metastatic renal carcinoma of the spine. Proceedings of the 31st An- nual Meeting of the American Society of Neuroradiology. Gangi A, Kastler BA, Dietemann JL (1994) Percutaneous vertebroplasty guided by a combination of CT and fluoroscopy. Heiss JD, Doppman JL, Oldfield JH (1994) Brief report: relief of spinal cord compression from vertebral hemangioma by intralesional injection of absolute ethanol.

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