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Marked agita- tion may necessitate arm and leg restraints to avoid home within 24 hr of an uneventful discharge (post- self-injury purchase mentax cheap fungus documentary, particularly in children buy mentax in india anti yeast antifungal diet. When serious discharge nausea and vomiting) in a signifcant physiological disturbances have been excluded in number of ambulatory surgery patients order mentax cheap fungal sinus. Other contributory factors include of surgical procedure purchase generic mentax online antifungal vitamins, and intrinsic patient factors, marked preoperative anxiety and fear, as well as such as a history of motion sickness. It is also impor- adverse drug efects (large doses of central anticho- tant to recognize that nausea is a common complaint linergic agents, phenothiazines, or ketamine). Phy- reported at the onset of hypotension, particularly sostigmine 1–2 mg intravenously (0. An increased incidence of nausea disturbances and pain are excluded, persistent agita- and vomiting is reported following opioid adminis- tion may require sedation with intermittent intrave- tration and intraperitoneal (especially laparoscopic), nous doses of midazolam 0. An orally disintegrating agents, and it is also common in the immediate post- tablet preparation of ondansetron (8 mg) may be partum period. The most important cause of hypo- useful for treatment and prophylaxis against post- thermia is a redistribution of heat from the body core discharge nausea and vomiting. Transdermal scopolamine is agents and spinal and epidural anesthesia, decrease efective, but can be associated with side efects, such the normal vasoconstrictive response to hypother- as sedation, dysphoria, blurred vision, dry mouth, mia by decreasing sympathetic tone. Although anes- urinary retention, and exacerbation of glaucoma, thetic agents also decrease the shivering threshold, particularly in elderly patients. Emergence from even brief gen- tive for up to 24 hr, and, thus, may be useful for eral anesthesia is sometimes also associated with postdischarge nausea and vomiting. Oral aprepitant shivering, and although the shivering can be one (Emend®) 40 mg may be administered within 3 hr of several nonspecifc neurological signs (postur- prior to anesthesia induction. Other causes of shivering should be excluded, adequate hydration (20 mL/kg) afer fasting, and such as bacteremia and sepsis, drug allergy, or trans- stimulation of the P6 acupuncture point (wrist). Small intravenous Color Oxygenation doses of meperidine (10–25 mg) can dramatically Pink SpO2 >92% on room air 2 reduce or even stop shivering. Intubated and mechan- Pale or dusky SpO >90% on oxygen 1 2 ically ventilated patients can also be sedated and Cyanotic SpO2 <90% on oxygen 0 given a muscle relaxant until normothermia is rees- Respiration tablished by active rewarming and the efects of anes- Can breathe deeply Breathes deeply and 2 thesia have dissipated. Criteria can vary according to whether oriented Arousable but readily Arousable on calling 1 the patient is going to be discharged to an intensive drifts back to sleep care unit, a regular ward, the outpatient department No response Not responsive 0 (phase 2 recovery), or directly home. Activity Before discharge, patients should have been Moves all extremities Same 2 observed for respiratory depression for at least Moves two extremities Same 1 20–30 min afer the last dose of parenteral opioid. S t able vital signs for at least 15–30 min meet discharge criteria within 60 min from the time 5. Patients to be transferred to other intensive care areas need not meet all requirements. No obvious surgical complications (such as I n addition to the above criteria, patients receiv- active bleeding) ing regional anesthesia should also be assessed P ostoperative pain and nausea and vomiting for regression of both sensory and motor block- must be controlled, and normothermia should be ade. Documenting regression of a block is impor- Within 20% to 40% of preoperative baseline 1 tant. Failure of a spinal or epidural block to resolve >40% of preoperative baseline 0 6 hr afer the last dose of local anesthetic raises the possibility of spinal subdural or epidural hematoma, Activity level Steady gait, no dizziness, at preoperative level 2 which should be excluded by prompt radiological Requires assistance 1 imaging and neurologic evaluation. Similarly, inpatients who meet the same Pain: minimal or none, acceptable to patient, criteria may be transferred directly from the operat- controlled with oral medication ing room to their ward, if appropriate stafng and Yes 2 monitoring is present. A scoring system has been developed to help assess home readiness discharge (Table 56–3). Recovery of proprioception, sympathetic tone, blad- home can be delegated to a nurse, if approved dis- der function, and motor strengthare additional crite- charge criteria are applied. For example, intact Home readiness does not imply that the patient proprioception of the big toe, minimal orthostatic has the ability to make important decisions, to blood pressure and heart rate changes, and normal drive, or to return to work. Tese activities require plantar fexion of the foot are important signals of complete psychomotor recovery, which is ofen not recovery following spinal anesthesia. All outpa- drinking or eating before discharge are usually no tient centers must use some system of postoperative longer required; exceptions include patients with a follow-up, preferably phone contact the day afer history of urinary retention and those with diabetes. All outpatients must be discharged home in the company of a responsible adult who will stay with them overnight (the latter is required if they have Management of Complications received an anesthetic). Endotracheal intu- ognition of these complications and fewer adverse bation may occasionally be necessary to reestablish outcomes. G lottic edema following airway instrumenta- Airway obstruction in unconscious patients is most tion is an important cause of airway obstruction in commonly due to the tongue falling back against the infants and young children because of the relatively posterior pharynx (see Chapter 19). Intravenous corticosteroids include laryngospasm, glottic edema, secretions, (dexamethasone, 0. Postoperative wound hemato- obstruction usually presents as sonorous respira- mas following thyroid, carotid artery, and other neck tion. Near-total or total obstruction causes cessa- procedures can quickly compromise the airway, and tion of airfow and an absence of breath sounds and opening the wound immediately relieves tracheal may be accompanied by paradoxic (rocking) move- compression in most cases. The abdomen and chest should may be unintentionally lef in the hypopharynx normally rise together during inspiration; however, following oral surgery and can cause immediate or with airway obstruction, the chest descends as the delayed complete airway obstruction, especially in abdomen rises during each inspiration (paradoxic patients with intermaxillary fxation. Patients with airway obstruc- Accidental or intentional decannulation of a tion should receive supplemental oxygen while fresh tracheostomy is hazardous because the vari- corrective measures are undertaken. A combined ous tissue planes have not yet organized into a well- jaw-thrust and head-tilt maneuver pulls the tongue formed track, thereby ofen making recannulation forward and opens the airway, and insertion of an very difcult or impossible. Laryngospasm is usually characterized by high- pitched crowing noises, but may be silent with com- Hypoventilation plete glottic closure. Spasm of the vocal cords is Hypoventilation, which is generally defned as a more apt to occur following airway trauma, repeated Pa co 2 >45 mm Hg, is common following general instrumentation, or stimulation from secretions or anesthesia. Signif- ticularly when combined with gentle positive airway cant hypoventilation is usually clinically apparent pressure via a tight-ftting face mask, usually breaks when the Paco2 is >60 mm Hg or arterial blood pH laryngospasm. Signs are varied and include excessive is also helpful in ensuring a patent airway down to somnolence, airway obstruction, slow respiratory the level of the vocal cords. Any secretions or blood rate, tachypnea with shallow breathing, or labored in the hypopharynx should be suctioned to prevent breathing. If signifcant hypoventilation is requires assisted or controlled ventilation until causal suspected, assessment and management is facili- factors are identifed and corrected. Obtunda- 6 tated by capnography and/or arterial blood gas tion, circulatory depression, and severe acido- measurement. Antagonism of opioid-induced respiratory depression characteristically produces a depression with large doses of naloxone ofen results slow respiratory rate, ofen with large tidal volumes. The latter can precipitate a hypertensive crisis, is ofen responsive and able to breathe on com- pulmonary edema, and myocardial ischemia or mand. Proposed induced respiratory depression, titration in small mechanisms include variations in the intensity of increments (80 mcg in adults) usually avoids compli- stimulation during recovery and delayed release of cations by reversal of hypoventilation without sig- the opioid from peripheral compartments, such as nifcant reversal of analgesia. F ollowing 7 skeletal muscle (or possibly the lungs with fentanyl), naloxone administration, patients should be as the patient rewarms or begins to move.
Allografts are derived from strength and a substrate for bone formation buy mentax 15mg amex anti fungal immune response, while cadavers and are available as bone chips or cylin- the collagen contributes tensile strength and pro- ders from fbula or rib and retain some bony motes hemostasis at the surgical site purchase cheap mentax on line antifungal ointment for lips. Ultimately buy mentax 15mg lowest price antifungal bathroom cleaner, an uninter- such materials appear as grainy foci of heteroge- rupted bony bridge should form across the verte- neous attenuation (Fig buy mentax 15 mg visa fungus gnats jump. This substance promotes tutes that are used during spine surgery include bone resorption or osteolysis. Despite this fnd- ceramics, demineralized bone matrix, and com- ing, fusion typically progresses and matures posite materials. A lag screw is used in order to help tioned in contact with the site of spinal fusion and reduce the fracture. Complications of this a small power source that is implanted in the sub- procedure include hematomas, dysphagia, hoarse- cutaneous tissues (Fig. The role of imag- ness, and vascular, spinal cord, or nerve root inju- ing is to confrm proper positioning of the ries. The tip of the screw can often safely project beyond the posterosuperior edge of the dens by several millimeters. Other options for treating odontoid fractures include posterior spinal fusion or halo-vest immobilization. Lateral radiograph shows the leads in contact with the fusion masses and the battery pack (arrow) implanted in the subcutaneous tissues b Fig. Sublaminar wires have the poten- Indications for occipitocervical fusion include tial to unravel, resulting in recurrent malalign- anterior and posterior bifd C1 arches with insta- ment and instability (Fig. In basilar invagination, unstable dystopic os odon- addition, wire fracture can lacerate the spinal toideum, unilateral atlas assimilation, traumatic cord. The occipital screws can sometimes pene- occipitocervical dislocation, complex craniover- trate the inner table of the occipital bone tebral junction fractures of C1 and C2, transoral (Fig. Photograph of an occipital plate (b) (arrow) attached to the occipital bone via plate (arrow) a Fig. The screws should Subsidence of the hardware or graft material not transgress the adjacent disc space. The plates is a chronic process in which the materials pene- and screws are most often metallic, although trate into the adjacent vertebral bodies or disc some biodegradable devices have been devel- spaces. For example, Dysphagia and dysphonia are common following Zero P is a Synthes device used as a stand-alone anterior cervical fusion due to injury to the pha- implant in cervical interbody fusion and incorpo- ryngeal plexus and recurrent laryngeal nerve. Otolaryngology consultation should Zero P and all similar devices are designed to be obtained for patients with postoperative dys- reduce adjacent level ossifcation, since the plate phagia or dysphonia, particularly if that persists does not irritate the adjacent disc. Axial fat-suppressed sion into the anterior epidural space (arrow) 11 Imaging of Postoperative Spine 549 Fig. The adjustable devices that can provide rigid fxation device is inserted by using an anterior approach. Pedicle screws through lateral mass screws, which are situated attach posteriorly to rods or plates via clamps or between the superior and inferior articular pro- bolts and have shallow cancellous threads that cesses, thereby lowering the likelihood of the pass through the pedicle and into the vertebral types of malpositioning associated with pedicle body. The screws can pro- the vertebrae via sublaminar wires or cables duce considerable beam-hardening artifacts on (Fig. Hooks that pass below the lamina are obscure adjacent structures, which is more pro- termed up-going, while those that pass above the nounced at higher magnetic feld strength lamina are termed down-going (Fig. Medial malposition- are connected to the rods via screws, bolts, or ing is a potentially devastating complication that washers. Facet screw fxation is an alternative to can result in spinal cord or nerve injury. Laterally pedicle screw fxation whereby the articular fac- malpositioned screws can injure exiting nerve ets are fused. Pedicle screws can also potentially cause but may be used in conjunction with interbody vascular injury, such as the aorta or inferior vena fusion or anterior plating (Fig. In contrast to threaded Knodt tion and screw pullout, which can be predisposed rods, Harrington rods feature fanged ends, which by the high torque inherent to the length of the can attach to laminar hooks. The usually paired and interconnected by segmental thoracolumbar fxation hardware may also lead wires for added stability. Luque rods are spino- to “fat-back” syndrome, in which there is loss of pelvic fxation devices that can be used to treat lumbar lordosis (Fig. Frontal radiograph shows a metallic rod with fanged end (arrow) spanning the thora- columbar spine in a patient with scoliosis 11 Imaging of Postoperative Spine 557 Fig. Frontal radiograph shows instru- mentation with pelvic fxation using the Galveston tech- nique (arrow) Fig. Lateral scout images show posterior displacement of the inferior end of the Harrington rod (encircled) with separation from the hook Fig. A tho- Vertebral body stapling is a minimally inva- racoscopic approach can be used for thoracic sive, fusionless alternative to reduce curvature curves and a mini-open retroperitoneal progression in patients with mild idiopathic approach for lumbar curves. Vertebral staples are composed of rates are high and with few associated compli- shape memory alloys that can be custom ft to cations, although long-term follow-up is not the size of the vertebral body. Frontal (a) and lateral (b) radiographs show the C-shaped staples positioned in multiple contiguous vertebral bodies along the convex side of the thoracic scoliosis 560 D. Complications include device migration, patients, with repeated lengthening sessions. These materi- The goal of lumbar interbody fusion with pros- als are radiolucent, which facilitates visualization of thetic devices is to provide stability while pro- the bone graft-vertebral body endplate interface. Many materials and The devices also contain press-ft titanium markers devices have been used for this purpose, includ- in order to demarcate the boundaries of the device ing bone threaded bone graft dowels or femoral on radiographs. Femoral ally are rectangular with grooves in order to pro- ring grafts are cylindrically shaped and inserted mote vertebral body attachment. There are a variety into the intervertebral disc space via anterior of approaches that can be used for interbody fusion lumbar interbody fusion, posterior lumbar inter- (Figs. A major disadvan- Imaging can be used to assess the position of tage of such allograft device is the risk of dis- the implants, which should be located at least ease transmission. Wide varieties of metal cages 2 mm anterior to the posterior wall of the verte- have been and continue to be developed. Radiographs with lateral fexion are cylindrical, hollow, porous, threaded, tita- and extension views can be used for this purpose, nium alloy cages that can be screwed into posi- although the accuracy is highly dependent upon tion in the intervertebral disc space (Fig. Early bone healing can often facilitates restoration of lumbar lordosis be appreciated at 3 months and is usually nearly (Fig. Lateral radiograph shows a Synfx device implanted in the L5–S1 anterior disc space (arrow). Posterior stabilization hardware is also present 11 Imaging of Postoperative Spine 565 a Fig. Note the image (b) show that the device composed of both radiolu- absence of additional hardware.
Moreover order discount mentax on line fungi reproduction, not way that extended-duration epidural morphine is all local anesthetics exist in a charged form (eg order genuine mentax line antifungal usmle, being used for single-shot purchase discount mentax on-line fungus parasite, prolonged epidural benzocaine) cheap mentax online mastercard anti fungal oil for scalp. The importance of the ionized and nonion- Diferential block of sensory rather than motor ized forms has many clinical implications, at least function would be desirable. Local bupivacaine and ropivacaine display some selectively anesthetic solutions are prepared commercially (mostly during onset and ofset of block) for sen- as water-soluble hydrochloride salts (pH 6–7). As a direct conse- quence, these commercially formulated, epineph- Pharmacokinetics rine-containing preparations may have a lower In regional anesthesia local anesthetics are 6 concentration of free base and a slower onset than typically injected or applied very close to their when the epinephrine is added by the clinician at intended site of action; thus their pharmacokinetic the time of use. Similarly, the extracellular base- profiles are much more important determinants of to-cation ratio is decreased and onset is delayed elimination and toxicity than of their desired clinical when local anesthetics are injected into acidic (eg, effect. Local anesthetic agent —More lipid-soluble local base to ensure permeation and analgesia. The agents also vary in their and 5% prilocaine bases in an oil-in-water emul- intrinsic vasodilator properties. Dermal analgesia sufficient for beginning an intravenous line requires a contact time of at least B. Depth of penetra- Distribution depends on organ uptake, which is tion (usually 3–5 mm), duration of action (usually determined by the following factors. Tissue perfusion —The highly perfused organs application time, dermal blood flow, keratin thick- (brain, lung, liver, kidney, and heart) are respon- ness, and total dose administered. Typically, 1–2 g sible for the initial rapid uptake (α phase), which of cream is applied per 10-cm2 area of skin, with a is followed by a slower redistribution (β phase) to maximum application area of 2000 cm2 in an adult moderately perfused tissues (muscle and gut). Tissue/blood partition coefcient—Increasing tion to methemoglobinemia (see Biotransformation lipid solubility is associated with greater plasma pro- and Excretion, below). Biotransformation and Excretion tracheal > intercostal > paracervical > epidural > The biotransformation and excretion of local anes- brachial plexus > sciatic > subcutaneous. E s t e r s — Ester local anesthetics are predom- nephrine—or less commonly phenylephrine— 8 inantly metabolized by pseudocholinesterase causes vasoconstriction at the site of administration. The consequent decreased absorption reduces Ester hydrolysis is very rapid, and the water-soluble the peak local anesthetic concentration in blood, metabolites are excreted in the urine. Patients with genetically more pronounced efects on shorter-acting than abnormal pseudocholinesterase would theoretically longer-acting agents. For example, addition of epi- be at increased risk for toxic side efects, as metabo- nephrine to lidocaine usually extends the duration lism is slower, but clinical evidence for this is of anesthesia by at least 50%, but epinephrine has lacking. Cerebrospinal fuid lacks esterase enzymes, little or no efect on the duration of bupivacaine so the termination of action of intrathecally injected peripheral nerve blocks. In contrast to other as impulse generation and conduction in the heart, ester anesthetics, cocaine is partially metabolized it is not surprising that local anesthetics in high cir- (N-methylation and ester hydrolysis) in the liver culating concentrations could have the propensity and partially excreted unchanged in the urine. Amides —Amide local anesthetics are metabo- are discussed for these drugs as a group, individual lized (N-dealkylation and hydroxylation) by micro- drugs differ. The rate of amide Potency at most toxic side efects correlates with metabolism depends on the specifc agent (prilo- potency at nerve blocks. Maximum safe doses are caine > lidocaine > mepivacaine > ropivacaine > listed in Table 16–3, but it must be recognized that bupivacaine) but overall is consistently slower than the maximum safe dose depends on the patient, the ester hydrolysis of ester local anesthetics. Decreases specifc nerve block, the rate of injection, and a long in hepatic function (eg, cirrhosis of the liver) or liver list of other factors. In other words, tables of pur- blood fow (eg, congestive heart failure, β blockers, or ported maximal safe doses are nearly nonsensical. H2-receptor blockers) will reduce the metabolic rate Mixtures of local anesthetics should be considered and potentially predispose patients to having greater to have additive toxic efects; therefore, a solution blood concentrations and a greater risk of systemic containing 50% of the toxic dose of lidocaine and toxicity. Very little unmetabolized local anesthetic 50% of the toxic dose of bupivacaine if injected by is excreted by the kidneys, although water-soluble accident intravenously will produce toxic efects. Neurological metabolized to o-toluidine, which produces met- The central nervous system is vulnerable to 9 hemoglobinemia in a dose-dependent fashion. Early symptoms include circumoral cally important methemoglobinemia (in the range numbness, tongue paresthesia, dizziness, tinnitus, of 10 mg/kg); however, recent studies have shown and blurred vision. Excitatory signs include restless- that younger, healthier patients develop medically ness, agitation, nervousness, garrulousness, and a important methemoglobinemia afer lower doses of feeling of “impending doom. Prilocaine is generally not used for blood concentrations may produce central nervous epidural anesthesia during labor or in larger doses system depression (eg, coma and respiratory arrest). The excitatory reactions are thought to be the result Benzocaine, a common ingredient in topical of selective blockade of inhibitory pathways. Potent, local anesthetic sprays, can also cause danger- highly lipid-soluble local anesthetics produce sei- ous levels of methemoglobinemia. For this rea- zures at lower blood concentrations than less potent son, many hospitals no longer permit benzocaine agents. Methylene blue reduces met- and reliably terminates seizure activity (as do com- hemoglobin (Fe3+) to hemoglobin (Fe2+ ). Maintaining a clear airway with adequate ventilation and oxygenation is of key importance. E ﬀ ects on Organ Systems Infused local anesthetics have a variety of Because inhibition of voltage-gated Na channels actions. Systemically administered local anesthetics from circulating local anesthetics might affect action such as lidocaine (1. Generally the shortest duration is with spinal anesthesia and the longest with peripheral nerve blocks. An overdose is heralded by restlessness, of lidocaine and procaine have been used to sup- emesis, tremors, convulsions, arrhythmias, respira- plement general anesthetic techniques, as they are tory failure, and cardiac arrest. Infused lido- of large volumes of chloroprocaine into the sub- caine reduces postoperative opioid requirements arachnoid space (during attempts at epidural sufciently to reduce length of stay afer colorectal anesthesia), produced total spinal anesthesia or open prostate surgery. These Administration of 5% lidocaine has been asso- effects result from direct cardiac muscle membrane ciated with neurotoxicity (cauda equina syndrome) changes (ie, cardiac Na channel blockade) and in following infusion through small-bore catheters intact organisms from inhibition of the autonomic used in continuous spinal anesthesia. All local anesthetics except cocaine due to pooling of drug around the cauda equina, produce smooth muscle relaxation at higher con- resulting in high concentrations and permanent centrations, which may cause some degree of arte- neuronal damage. At low concentrations all local extent of histological evidence of neurotoxicity fol- anesthetics inhibit nitric oxide, causing vasocon- lowing repeat intrathecal injection is lidocaine = striction. Major car- 10 lower extremities and buttocks, have been reported diovascular toxicity usually requires about following spinal anesthesia with a variety of local three times the local anesthetic concentration in anesthetic agents, most commonly afer use of blood as that required to produce seizures. Cardiac lidocaine for outpatient spinal anesthesia in men arrhythmias or circulatory collapse are the usual undergoing surgery in the lithotomy position. Tese presenting signs of local anesthetic overdose dur- symptoms have been attributed to radicular irrita- ing general anesthesia. Many jects, signs of transient cardiovascular stimulation clinicians have substituted 2-chloroprocaine, mepi- (tachycardia and hypertension) may occur with vacaine, or small doses of bupivacaine for lidocaine central nervous system excitation at local anes- in spinal anesthesia in the hope of avoiding these thetic concentrations producing central nervous transient symptoms. Respiratory treatment for some forms of ventricular arrhyth- Lidocaine depresses hypoxic drive (the ventila- mias.
This patient has symptoms concerning for Wernicke enceph- In addition to afecting the cardiovascular and gastro- alopathy (cognitive changes buy mentax from india fungus games, ataxia order mentax 15 mg on line anti fungal anti itch, disturbances in extra- intestinal systems mentax 15 mg low cost fungus eyelid, alcohol suppresses the immune system buy on line mentax anti viral fungal fighter. Patients who abuse alcohol are at risk for thiamine pneumoniae, which can cause endocarditis, pneumonia, defciency. Alcohol is also a risk factor for Listeria who might be at risk for the condition, thiamine should be monocytogenes meningitis. Children 240 with fetal alcohol syndrome ofen have microcephaly as well Opioid intoxication is treated with naloxone. Naloxone as short palpebral fssures, a smooth philtrum, and a thin can precipitate opioid withdrawal in patients who are upper lip. It also is accompanied by euphoria, hypo- Beta-blockers should be avoided in patients with acute thermia, vomiting, constipation, and postural hypoten- cocaine intoxication because they can cause paradoxical sion. Injection of heroin increases the patient’s those of an amphetamine and a hallucinogen. Normeperidine, which is the metabolite of meperidine, can cause altered mental status, seizures, myoclonus, and tremor. The combination of dextromethorphan and quinidine has been used to treat pseudobulbar palsy. In addition, it can cause myoclonus, hypertensive encepha- lopathy, and ischemic and hemorrhagic stroke. D It can cause paranoia, hallucinations, fat afect, and Tobacco ingestion can cause cholinergic symptoms such catatonic posturing. Before using an antipsychotic Anticholinergic poisoning may be treated with physo- agent, it should be remembered that neuroleptics can stigmine. Neuroleptics have anticholinergic properties lower the seizure threshold, can worsen myoglobin- and should be avoided in anticholinergic poisoning. The combination of dementia with diarrhea and a scaly- patient has impaired vibration and position sense, a rash is concerning for defciency of which vitamin? She also reports a tingling sensation from her neck down her back with neck fexion. Fill in the blank: Excess intake of examination, she has decreased refexes and decreased causes myeloneuropathy due to copper defciency. C pyridoxine defciency, which is associated with a sen- Wernicke encephalopathy is associated with a triad of oph- sory polyneuropathy (see Box 29. There is a neonatal form is caused by thiamine (vitamin B1) defciency and is classi- of pyridoxine defciency characterized by refractory cally seen in alcoholics. If there is a chronic problem with memory, the patient This patient has vitamin B12 deficiency, which pre- has Wernicke-Korsakof syndrome. Classically, Korsakof dominantly affects the posterior columns and cortico- psychosis has been associated with confabulation. The regions of the spinal cord that are first affected are the posterior columns 2. A Nitrous oxide toxicity causes symptoms similar to Pyridoxine causes an axonal sensory neuropathy and those of vitamin B12 defciency. The structure of isotretinoin Vitamin B12 is also a cofactor for methylmalonyl– (Accutane) resembles that of vitamin A, so it can cause coenzyme A mutase. If vitamin B12 defciency is sus- Hypervitaminosis E can cause increased bleeding pected but the B12 level is normal, determination of the (because of its efect on vitamin K). Intracellular calcium increases caus- hypointense and T2 hyperintense, predominantly ing release of lipase and protease, ultimately lead- within the white matter. Accordingly, excitotoxic injury related to dural venous sinuses, cortical veins, or deep glutamate is associated with the pathophysiologi- 5,12 cerebral veins. In adults, the basal ganglia (especially the globus Herpes Encephalitis pallidus), thalamus, hippocampus, corpus callos- Excitotoxic injury in herpes encephalitis is attrib- um, and perirolandic cortex are disproportionally aﬀected due to their high metabolic demand and uted to abnormally increased concentrations of arterial watershed territories of the basal ganglia. Limbic Encephalitis Osmotic Myelinolysis Limbic encephalitis is the most common inflam- Both central pontine and extrapontine forms of matory disease that aﬀects the hippocampus. Damage these principles can enrich the interpretation by to the axon occurs at the node of Ranvier, allowing the radiologist. This finding was found incidentally on a magnetic resonance imaging scan for evaluation of epilepsy. Neuropathological aspects of toxic oligodendroglial death and demyelinating diseases. J Neuropathol Exp Neurol 1967; 26(1): 1–14 Trends Neurosci 2001; 24(4): 224–230  Vajda Z, Nielsen S, Sulyok E, Dóczi T. Neurotransmitters in cerebrospi- Orv Hetil 2001; 142(5): 223–225 nal fluid reflect pathological activity. Importance of protein content in 27(12): 1038–1043 the edema fluid for the resolution of brain edema. Neurology 2002; 58(1): 148–149 1994; 330(9): 613–622  Murata T, Shiga Y, Higano S, Takahashi S, Mugikura S. Pathology and new players in spicuity and evolution of lesions in Creutzfeldt-Jakob dis- the pathogenesis of brain edema. Does water transport in glial cells: high-resolution immunogold glutamate mediate brain damage in acute encephalitis? Slow rewarming: a cool model of posttraumatic Diﬀusion weighted imaging for the diﬀerential diagnosis of hypothermia. Nat Med 2000; 6(2): 159–163 eral temporal lobe hyperintensity: a retrospective review. Status epilepticus: risk factors and complica- stroke: eﬀects ofetiology and patient age on the time course tions. Pictorial review of gluta- 1297–1299 mate excitotoxicity: fundamental concepts for neuroimag-  Star M, Flaster M. Focal lesion in the splenium 31(3): 765–783 of the corpus callosum in epileptic patients: antiepileptic drug toxicity? Johnson neurosurgical interventions in the brain, and to recognize tumors and other diseases that spread Key Points along white matter tracts. The chapter begins by briefly out- defines a supporting network for the eﬃcient lining technical aspects of diﬀusion imaging rele- transfer of information of these regions within vant to the accurate depiction of fiber tracts. Given space con- small group of association (intrahemispheric), straints, the discussion necessarily omits cerebellar commissural (interhemispheric), and projection and brainstem tracts. The reader specifically inter- (aﬀerents or eﬀerents from the periphery to ested in brainstem tractography is referred to a the brain) pathways. Early experiments revealed infiltration and distortion of tracts, and the that brain images vary significantly with changes relationship between lesions and surrounding in the direction of the applied diﬀusion gradient; pathways. In addition to this orientational variability, varying the strength of the gradient (the diﬀusion weight- 3. By systemati- form signal intensity of the white matter on cally varying the magnitude and direction of the conventional anatomical imaging belies a highly applied diﬀusion gradients, it is possible to charac- complex network of pathways interconnecting dif- terize the probability of water movement over var- ferent brain regions and exchanging information ious spatial scales along each direction in space. This intricate archi- cially neuronal and myelin membranes, diﬀusion tecture serves as the scaﬀolding for higher brain preferentially occurs along directions parallel to function and as the target of many neurological axons. An understanding of basic connectional the diﬀusion sensitized image data and the three- neuroanatomy is essential for the radiologist to dimensional white matter architecture depends relate symptoms to lesion location, to guide on the technique that is used to represent the 36 Supratentorial White Matter Tracts and Their Organization underlying diﬀusion probability. Most clinical white matter contains more than a single fiber diﬀusion applications to date use deterministic population.
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