Coexistent End-stage Nonalcoholic Steatohepatitis and Colon Cancer: Should We Do Liver Transplantation?

BACKGROUND: Colon cancer accompanying decompensated liver cirrhosis is a rare clinical condition. Usually, treatment of colon cancer is prioritized, with cirrhosis dealt with later. CASE REPORT: We present a case of end-stage liver disease due to nonalcoholic steatohepatitis evaluated for living donor liver transplant. During the pretransplant examination, an ascending colon cancer was detected. Liver function was too poor to perform colon resection first. Simultaneous living donor liver transplant and colonic resection were carried out. The patient developed left lung metastasis at 2 different times during the first postoperative year, and both of them were resected. The patient received the standard chemoradiotherapy. Now, the patient is alive at 42 months postprocedure and recurrence-free at 31 months postoperatively. CONCLUSION: Simultaneous liver transplantation and colon resection are possible with acceptable long-term outcomes. Immunosuppressive therapy after transplantation increases the risk for cancer recurrence. So the patient should undergo close surveillance.

Liver-Regenerative Transplantation: Regrow and Reset.

Liver transplantation, either a partial liver from a living or deceased donor or a whole liver from a deceased donor, is the only curative therapy for severe end-stage liver disease. Only one-third of those on the liver transplant waiting list will be transplanted, and the demand for livers is projected to increase 23% in the next 20 years. Consequently, organ availability is an absolute constraint on the number of liver transplants that can be performed. Regenerative therapies aim to enhance liver tissue repair and regeneration by any means available (cell repopulation, tissue engineering, biomaterials, proteins, small molecules, and genes). Recent experimental work suggests that liver repopulation and engineered liver tissue are best suited to the task if an unlimited availability of functional induced pluripotent stem (iPS)-derived liver cells can be achieved. The derivation of iPS cells by reprogramming cell fate has opened up new lines of investigation, for instance, the generation of iPS-derived xenogeneic organs or the possibility of simply inducing the liver to reprogram its own hepatocyte function after injury. We reviewed current knowledge about liver repopulation, generation of engineered livers and reprogramming of liver function. We also discussed the numerous barriers that have to be overcome for clinical implementation.

Bioengineering in organ transplantation: targeting the liver.

About 27,000 deaths are registered annually in the United States due to liver disease. At this time, the only definitive treatment of hepatic failure is orthotopic transplantation. However, there is a critical shortage of organs with the total waiting list for all organs currently at 100,000 requests. The number is increasing by 5% every year. Given that only organs in pristine condition are transplantable and that the hidden demand for organs as an anti-aging solution will be many times the current figures, orthotopic transplantation will always remain a limited pool. The increasing donor organ shortage requires consideration of alternative emerging technologies. Regenerative medicine may offer novel strategies to treat patients with end-stage organ failure. The ultimate aim of cell transplantation, tissue engineering, and stem cells is to regenerate tissues and organs. With the development of whole organ decellularization methods, the equation of organ shortage may dramatically change in the near future. Decellularized organs provide the ideal transplantable scaffold with all the necessary microstructure and extracellular cues for cell attachment, differentiation, vascularization, and function. New techniques to re-engineer organs may have major implications for the fields of drug discovery, regeneration biology, and ultimately organ transplantation. In this review we have provided an overview of complementary approaches to study and enhance the success of organ repopulation strategies creating new grafts/organs for transplantation.

Cholecystokinin-1 receptor protein up-regulation during pancreatic regeneration after acute haemorrhagic pancreatitis in rats.

BACKGROUND: Cholecystokinin (CCK) plays an important role in regeneration after acute pancreatitis in rats. The present study was aimed to elucidate the role of CCK-1 receptor (CCK-1R) in acute pancreatitis. We investigated the serial changes in CCK-1R mRNA and protein levels and their immunolocalization after acute haemorrhagic pancreatitis induced in male Wistar rats by retrograde intraductal infusion of 4% sodium taurocholate (100 micro L 100 g(-1) body weight). METHODS: Histological changes were evaluated by haematoxylin and eosin staining. Pancreatic CCK-1R mRNA was determined by Northern blot analysis. Pancreatic CCK-1R protein was evaluated by immunoblot analysis and immunohistochemistry with a polyclonal antibody against rat CCK-1R protein. RESULTS: Histological findings revealed that newly formed acinar cells were detected at the periphery of tubular complexes on day 14, and normal architecture of lobules was observed focally on day 21. Pancreatic CCK-1R mRNA peaked on day 3 and thereafter gradually decreased. Cholecystokinin-1R protein rapidly increased after induction of pancreatitits, reaching a maximal level on day 3. On day 3, intense immunoreactivity for CCK-1R protein was observed in both the cytoplasm of vacuolized acinar cells and the tubular complexes. In the regenerative process after acute haemorrhagic pancreatitis in rats, the expression of pancreatic CCK-1R mRNA and protein increased, and intense immunoreactivity for CCK-1R protein was observed in tubular complexes in the cytoplasm of regenerated acinar cells. CONCLUSION: These results suggest that CCK-1R contributes to pancreatic regeneration after acute haemorrhagic pancreatitis and that tubular complexes are involved in the process of acinar cell regeneration following pancreatic injury.

[An extremely low birth weight infant with pulmonary atresia complicated with necrotizing enterocolitis].

We experienced an extremely low birth weight (ELBW) infant complicated with pulmonary atresia and necrotizing enterocolitis. She was born at 25 weeks of gestation with a birth weight of 752 g. Five hours after birth, she manifested cyanosis and was diagnosed as having pulmonary atresia with intact ventricular septum (PAIVS). Infusion of lipo-prostaglandin E1 (PGE1) was started to keep the ductus open along with infusion of dopamine and dobutamine. At 8 days of life she developed hypotension and metabolic acidosis, and the diagnosis of intestinal perforation was made by free air in the abdomen. The excessive shunt flow to the pulmonary vasculature via the ductus was suspected to have caused an inadequate systemic flow leading to the intestinal ischemia and necrotizing enterocolitis. Lipo-PGE1 was discontinued to decrease the shunt flow through the ductus. Brock's operation (closed transventricular pulmonary valvotomy) was performed at the age of 8 and 11 days and the ligation of the ductus arteriosus was performed at the age of 13 days. Propranolol was administered to inhibit the pulmonary outflow tract constriction along with catecholamines to stabilize hemodynamics. She recovered slowly and her trachea was extubated at 58 days of life.

[Recovery characteristics of propofol anesthesia in pediatric outpatients; comparison with sevoflurane anesthesia].

We compared recovery characteristics of propofol anesthesia with those of sevoflurane anesthesia in pediatric outpatients. One hundred and four children, 3 months to 6 years of age, ASA physical status 1 or 2, were randomly assigned to following four groups; sevoflurane (group S), propofol (group P), sevoflurane with premedication (group MS), or propofol with premedication (group MP). Midazolam 0.5 mg.kg-1 and famotidine 1 mg.kg-1 were administered orally 30 min before the induction in the MS and MP group. Recovery from anesthesia, agitation, and postoperative pain were evaluated. The time intervals from the end of surgery to extubation and to discharge from the hospital were recorded. The incidence of vomiting and use of analgesic drugs were also checked. The emergence from anesthesia was slower with propofol anesthesia than with sevoflurane anesthesia, but the time to discharge from the hospital was not significantly different among the four groups. Incidence of agitation was higher in S group compared with P group, but there were no differences between MS and MP. Postoperative pain was similar among the four groups. There were no differences in the incidence of vomiting. Propofol anesthesia provided slower emergence and less agitation compared with sevoflurane anesthesia.

[Perioperative management of twins with prenatally diagnosed congenital diaphragmatic hernia].

Congenital Diaphragmatic Hernia (CDH) occurs in one of every 2000-3000 births, and most of them are sporadic, and therefore recognized as a circumstantial event. But its occurrence in 85 children among the 40 families is also reported, and some reports suggest that an autosomal recessive gene may be responsible for this disease. We experienced identical twins (babies A and B) both with prenatally diagnosed CDH. They were delivered by emergent cesarean section at 33 weeks of gestation with birth weight of 1857 g and 1561 g, respectively. They were intubated immediately after birth, and ventilated with high frequency oscillation. Baby A presented persistent pulmonary hypertension of newborn, and received nitric oxide inhalation. At the age of 2 days, both of them were stabilized and underwent repair of CDH. After the repair, baby A developed perforation of ileum, airway bleeding and retinopathy of prematurity (ROP), and needed 28 days before extubation. Baby B also developed ROP, but had no other problem, and the trachea was extubated at the age of 12 days. They are the seventh pair reported in the world literature.

Troglitazone stimulates pancreatic growth in congenitally CCK-A receptor-deficient OLETF rats.

We examined the effect of troglitazone treatment on pancreatic growth in the CCK-A receptor-deficient Otsuka Long-Evans Tokushima fatty (OLETF) rat, an animal model for type 2 diabetes mellitus. A troglitazone-rich diet (0.2%) was given from 12 to 28 wk of age or from 12 or 28 wk of age to 72 wk of age. Fasting serum glucose concentrations in control OLETF rats increased progressively with age, which was almost completely prevented by troglitazone treatment. Insulin levels in serum and pancreatic content in the control rat markedly increased at 28 wk of age but significantly decreased at 72 wk of age compared with those at 12 wk of age, whereas those in troglitazone-treated rats were nearly the same at all ages and were similar to those in control rats at 12 wk of age. Pancreatic wet weight in control rats decreased with age irrespective of whether they were hyperinsulinemic (28 wk old) or hypoinsulinemic (72 wk old). Troglitazone treatment significantly increased pancreatic wet weight and protein, DNA, and enzyme contents compared with those in the control rats. Moreover, troglitazone treatment completely prevented or reversed histological alterations such as fibrosis, fatty replacement, and inflammatory cell infiltration. Our results indicate that troglitazone stimulates pancreatic growth in the congenitally CCK-A receptor-deficient OLETF rat not only by reducing insulin resistance and potentiating insulin action but also by suppressing inflammatory changes in the pancreas.

[Perioperative management of a child with congenital nephrogenic diabetes insipidus].

The key point in perioperative management of a patient with congenital nephrogenic diabetes insipidus is fluid and electrolytes management. Since the urine of these patients consists mainly of solute free water, replacement fluids should be fluids which provide free water. A 2-year-old girl with congenital nephrogenic diabetes insipidus was scheduled for dental extraction. Her daily fluid intake was 10 liter. She had a history of recurrent fever, polyuria and polydipsia since 2 months of age. Her previous perioperative course for gastric volvulus at another hospital was complicated with postoperative hyponatremia and convulsion. A venous line was secured the day before surgery and 5% dextrose in water was infused at a rate of 12 ml.kg-1.hr-1. Intraoperative infusion was mainly with 5% dextrose in water combined with maintenance fluid. Five hours after surgery oral intake was started. Her intraoperative electrolytes levels were low (Na 133 mEq.l-1, K 2.8 mEq.l-1), but otherwise her perioperative course was uneventful.

Chronic oral administration of protease inhibitor decreases CCK-A receptor mRNA expression but increases pancreatic growth in rats.

It is well-known that chronic oral administration of trypsin inhibitors induces pancreatic hypertrophy and hyperplasia via stimulation of endogenous cholecystokinin (CCK) release. Because the growth-promoting effect of CCK on the pancreas is specifically mediated by the CCK-A receptor, we examined the plasma CCK concentrations, the expression of CCK mRNA in the intestine and CCK-A receptor mRNA in the pancreas, and pancreatic growth in rats after chronic oral administration of synthetic protease inhibitor (PI). PI at a dose of 100 mg/kg body weight was administered via an orogastric tube once daily for 20 days. Plasma CCK concentrations at 24 hours after the first PI administration were significantly higher than those in randomly fed rats (6.57 +/- 0.67 pmol/L vs 4.31 +/- 0.51 pmol/L; p < 0.001), and further increased to 14.24 +/- 1.63 pmol/L after PI for 10 days and decreased to 10.05 +/- 0.72 pmol/L after 15 days of PI administration. Treatment with PI for 20 days significantly increased the pancreatic weight, and the total pancreatic protein and DNA content by 190%, 290%, and 170%, respectively, when compared to the control rats. Chronic oral administration of PI, however, reduced CCK-A receptor mRNA expression in the pancreas by 60%. These findings suggest that chronic oral administration of PI induces an elevation of endogenous CCK release and stimulates pancreatic growth, but down-regulates the biosynthesis of CCK-A receptor at the transcriptional level in the pancreas.

[Anesthetic management for the correction of pectus excavatum using pectus bar under video-assistance].

We report anesthetic management for a child undergoing Nuss operation, a minimally invasive operation which requires neither cartilage incision nor its resection for correction of pectus excavatum. The patient was a 7-year-old boy with the funnel index 5 and the mediastinal shift to the left. General anesthesia with endotracheal intubation was induced and maintained with nitrous oxide, sevoflurane and fentanyl. Thoracic epidural anesthesia was used with 0.125% bupivacaine to supplement analgesia. When the curved bar was passed under the sternum with the aid of an endoscope, sinus tachycardia occurred and continued for 5 minutes but subsided without medication. Otherwise operative course was uneventful with negligible blood loss. After surgery, the patient was kept at bed rest for 2 days, receiving epidural patient-controlled analgesia combined with sedation with midazolam with good results. He was allowed to sit 3 days, to walk 5 days and discharged 10 days postoperatively.

Respiratory system compliance and postoperative ventilator dependence in neonates with left-sided congenital diaphragmatic hernia.

PURPOSE: The purpose of this prospective consecutive patient study was to test if perioperative respiratory system compliance of patients undergoing surgical repair of congenital diaphragmatic hernia (CDH) can predict the need for prolonged postoperative mechanical ventilation. METHODS: All neonates over 35 weeks of gestation who had surgical repair of left-sided CDH between July 1994 and December 1996 ( n = 10) were included in this study. Static respiratory system compliance (C(rs)) was measured by the passive occlusion method with muscle relaxation before (C(pre)) and after (C(post)) surgical repair of left-sided CDH. We examined the relationship between respiratory system compliance and postoperative ventilator-dependent duration. RESULTS: The mean birthweight-corrected C(post) was lower than that of birthweight-corrected C(pre) (0.41 +/- 0.18 vs 0.54 +/- 0.18 ml.cm H(2)O(-1).kg(-1), P = 0.04). One neonate died on postoperative day 31 from intraventricular hemorrhage, and the other nine neonates survived. The patient who died was excluded from the rest of our calculations. The ventilator-dependent duration was 16.7 +/- 12.3 days. The postoperative ventilator-dependent duration was longer when the birthweight-corrected C(post) was smaller, with a significant correlation between these parameters ( P = 0.006). CONCLUSION: C(post), but not C(pre), may be useful to predict the need for prolonged postoperative mechanical ventilation in neonates with left-sided CDH.

[Two pediatric cases of malignant hyperthermia caused by sevoflurane].

We experienced two cases of malignant hyperthermia (MH) triggered by sevoflurane. Case 1 was a six-year-old girl, 15.8 kg, undergoing strabismus repair. She had flat back, elevated diaphragm and high arched palate. Anesthesia was induced and maintained with sevoflurane and nitrous oxide in oxygen. Her trachea was intubated without the use of muscle relaxant. Thirty minutes after the induction of anesthesia, ETco2 was over 60 mmHg despite hyperventilation. Muscle rigidity of legs and the rise in temperature were noted. MH was diagnosed and dantrolene i.v. was administered. Her maximum esophageal temperature was 40.2 degrees C. ETco2 and temperature returned to baseline values after dantrolene administration. Creatine phosphokinase (CK) level was 252 U.l-1 preoperatively, and 1690 U.l-1 next day. Case 2 was a year-and-9-month-old boy undergoing accessory ear resection. Anesthesia was induced with sevoflurane and nitrous oxide in oxygen. His trachea was intubated with an aid of vecuronium. Forty minutes after administration of sevoflurane his temperature rose to 38.6 degrees C with heart rate 191 bpm and Spo2 93%, and muscle rigidity of legs. MH was diagnosed and dantrolene was administered. His highest temperature was 39.3 degrees C and was reduced promptly after dantrolene. Postoperatively he was noted to have downslanting palpebral fissures, micrognathia, low set ears, and a single crease of the fifth finger and diagnosed as King syndrome which is reported to have association with MH. Both patients had no history of anesthesia nor abnormal family history. Both of them were rescued with dantrolene and recovered without sequelae.

Troglitazone prevents and reverses dyslipidemia, insulin secretory defects, and histologic abnormalities in a rat model of naturally occurring obese diabetes.

Troglitazone has been shown to improve insulin sensitivity and thereby exert hypoglycemic effects in various animal models and humans with insulin resistance and diabetes. The recently established animal model of naturally occurring obese diabetes, the Otsuka Long-Evans Tokushima fatty (OLETF) rat, has many similarities with human type 2 diabetes mellitus and is characterized by a high degree of insulin resistance. In the present study, we examined the effect of pharmacologic intervention with troglitazone on metabolic and histopathologic changes in OLETF rats. Two groups of rats received a troglitazone-rich diet (200 mg/100 g normal chow) from age 12 weeks (ie, before the onset of diabetes) or 28 weeks (ie, after the onset of diabetes) to age 70 weeks, while a third group received standard rat chow. The addition of troglitazone to the diet did not alter food intake or body weight gain. Troglitazone had no influence on visceral adipose depots, but it significantly reduced fasting glucose, insulin, cholesterol, triglyceride (TG), and free fatty acid (FFA) levels. Troglitazone reduced the insulin resistance and maintained the postglycemic insulin response at a normal level, and thus inhibited the development of insulin insensitivity and frank diabetes in OLETF rats up to 70 weeks of age. The pancreatic wet weight and insulin content were significantly higher in the treated rat groups versus the control rats. The morphologic changes observed in the control rats, such as fibrosis and structural disarrangement of islets, were minimal in the troglitazone-treated rats. Our study demonstrates that troglitazone, albeit at a dosage 10 to 15 times higher than that in humans, not only prevents but also reverses the metabolic derangement and histopathologic changes in genetically determined obese diabetes.

[Cesarean section in a pregnant patient with placenta percreta involving the urinary bladder].

Placenta percreta involving adjacent structures is serious complication of pregnancy with a high mortality rate. A 32-year-old woman, gravida 4, para 3, who had previously undergone a cesarean section, was admitted to our hospital at 31 weeks' gestation for placenta previa. At 33 weeks' gestation, the diagnosis of placenta percreta with involvement of the urinary bladder was made by ultrasonography and magnetic resonance imaging. At 34 weeks' gestation, an elective cesarean section was scheduled. Anesthesia was maintained with sevoflurane in oxygen before delivery, and with nitrous oxide in oxygen, fentanyl and midazolam after delivery. During the operation, attempts to remove the placenta resulted in massive hemorrhage. Blood loss for the procedure was 13,800 g. Because of the extreme hemorrhage, we encountered hemorrhagic shock and postoperative complications despite the preoperative preparation. In case of placenta percreta, it is essential to prepare adequate volume of blood for transfusion at the start of surgery and secure large bore intravenous lines. A rapid transfusion device may be recommended. Regarding the anesthetic management, general anesthesia is preferable in consideration of the risk of hemorrhagic shock and the length of operation time. Furthermore, we need team approach and preoperative management to prevent the uncontrolled hemorrhage in such a severe case.

Postbypass pulmonary artery pressure influences respiratory system compliance after ventricular septal defect closure.

It is reported that surgical correction of left-to-right shunt improves respiratory function in paediatric cardiac patients. However, such correction sometimes does not result in an improvement of respiratory compliance. The purpose of this study was to look for factors determining changes in respiratory system compliance (Crs) in patients who underwent closure of ventricular septal defect (VSD closure). In a prospective study, 17 children (< 10 kg) who underwent VSD closure were enrolled. They were divided into two groups, according to postbypass mean pulmonary artery pressure (mPAP). The patients were allocated to Group C if mPAP was < or = 18 mmHg (n=12) and to Group PH if > 18 mmHg (n=5). We compared the ratio of postoperative Crs to preoperative Crs (Cpost/Cpre) between the groups. A multiple occlusion technique was used to measure Crs. The Cpost/Cpre in group C was larger than that in group PH (1.11+/-0.17 vs. 0.81+/-0.12, P<0.01). There was a correlation between postbypass mPAP and Cpost/Cpre (r(s)=0.49, P<0.05), but no correlation was noted between preoperative mPAP, Qp/Qs or Rp/Rs and Cpost/Cpre. We concluded that high postbypass mPAP was associated with a perioperative decrease in Crs after VSD closure.

[Perioperative management of two neonates with severe Ebstein's anomaly with pulmonary atresia].

Ebstein's anomaly appearing during the neonatal period carries a high mortality rate. We report the perioperative management of two neonates with severe Ebstein's anomaly associated with pulmonary atresia. Their chest radiography revealed massive cardiomegaly, with cardiothoracic ratio of 90% and 100%, respectively. Their tracheas were intubated immediately after birth because of severe respiratory distress. The babies were laid in the prone position and one of them was managed with high frequency oscillatory ventilation (HFO) for prevention of pulmonary barotrauma and extensive atelectasis in the preoperative period. On the 4th and 3rd day after birth, respectively, they underwent Starnes procedure which consists of closure of tricuspid valve, enlargement of atrial septal defect, reduction of right atrium and creation of aortopulmonary shunt reported to be a useful palliative treatment for critically ill neonates with Ebstein's anomaly. Case 1 baby could not be weaned from cardiopulmonary bypass because of low cardiac output. Case 2 could not be weaned from extracorporeal membrane oxygenation due to hypoxia. We consider, however, treatment of respiratory failure and lung protection after birth are important for the prognosis. Perioperative use of HFO may be advantageous for the neonate with severe Ebstein's anomaly with pulmonary atresia.

[Anesthetic management for newborn pharyngeal teratoma].

Epignathus (pharyngeal teratoma) is a rare disease of newborns associated with a high mortality secondary to airway obstruction in the neonatal period. We report anesthetic management of a newborn with epignathus who underwent tumor resection. He was delivered vaginally at 39 weeks of gestation and Apgar scores were 9 at 1 and 5 min. The tumor originated from the palate, almost filled the oral cavity and protruded through the mouth with its external part 6 x 7 cm in size. He could breathe with the head and mass turned to the left. The excision of the tumor was scheduled on the fifth day of life. Mask ventilation and laryngoscopy were considered impossible. Fiberoptic nasal intubation was successfully performed with topical anesthesia without sedation. Tumor was resected with blood loss of 103 gm. The trachea was extubated on the third postoperative day and the postoperative course was uneventful. For safe management of cases of pharyngeal teratoma, careful preoperative assessment of the airway is most important and sufficient preparation and careful intubation are mandatory to keep airway patent. The perioperative bleeding from the tumor and the airway obstruction by the tumor or its remnant after the excision could also be hazardous to the airway.

[A new bite block also serving as an endotracheal tube holder for infants].

We developed a new type of bite block with a combined function as an endotracheal tube (ETT) holder for infants and small children to prevent airway troubles caused by tube kinking, dislodging, extubation and oral membrane trauma. One mm thick plastic plate sized 3.5 x 2 cm was curved to make an open roll. The outer surface of the roll was covered and glued with soft plastic tube (5.0 mm ID endotracheal tube), cut in 3.5 cm length to give an elastic outer surface for the patient's comfort. The rolled ends were diagonally cut to make an oblique slit of 3 mm width. A t-shaped flange made of soft vinyl plate was fixed at a third of the length of the roll to maintain the block's position relative to the lips and to make the fixation of the tube easier. In practical use, after endotracheal intubation is performed as usual, this bite block is put into the mouth and positioned at the oral angle with the flange on the patient's skin. The ETT is fit into the slit of the roll. The skin-facing surface of the flange is pasted to the skin with the double stick material usually used for colostomy stoma. The ETT and the bite block are fixed en bloc with fixing tapes around the mouth. Our bite block has following advantages over other types of bite blocks and tube holders especially for children; 1) the volume of foreign bodies (ETT and bite block) occupying the oral cavity can be reduced and this attenuates the patient's discomfort, 2) good holding of the ETT can prevent its dislodging and decrease the incidence of accidental extubation and 3) suctioning is easier because of wide oral space. The four sizes of the bite block suitable for 4.0, 4.5, 5.0, 5.5 and 6.0 mm ID ETTs are manufactured. We applied this device to several ICU patients and found its use practical and safe.

Brachial plexus birth injuries: anaesthesia for surgical nerve reconstruction and preoperative myelography and computed tomographic myelography.

Surgical nerve reconstruction for brachial plexus birth injuries and preoperative myelography and computed tomographic (CT) myelography require special anaesthetic considerations. Anaesthesia and medical records were retrospectively reviewed for the infants who underwent myelography, CT myelography (n=37) and microsurgical nerve reconstruction (n=34) at our institution from January 1993 to August 1996. Anaesthetic considerations include long duration of operation, perioperative respiratory complications and plaster application which makes reintubation difficult. Myelography for diagnosis requires a specific positioning of the patient with the head fixed in a midline and prone position.