Radiation tolerance of the cochlear nerve at the γ-knife in rabbits

Since the first treatment of acoustic neurinoma using the γ-knife by Leksell, a series of cases have been reported with good control rates. However, the most frequent complication is delayed hearing loss which occurs in more than 50% of patients. The purpose of this study was to define a safe dose by analyzing the radiosurgical dose-response relationship and histological effects on the normal cochlear nerve in rabbit. The rabbits had computed tomography (CT)-guided stereotactic radiosurgery on their cochlear nerves in the internal auditory canal with a 4 mm collimator focusing of a γ-unit. Maximum doses of 10, 20, 30, 40, 60, 80, 100, 200 and 500 Gy were administered. After the radiosurgery, auditory brain stem responses (ABR) and the behavior of the rabbits were evaluated periodically. At the conclusion, histological investigations were performed. No physiological or histological findings were observed from doses of 30 Gy or below during the 12 month period after the radiosurgery. A dose of 100 Gy caused a severe ABR threshold elevation, vestibular dysfunction and facial palsy. Necrosis and demyelination of nerves were observed pathologically. In this study, we determined that the safe dose to the normal cochlear nerve during radiosurgery was under 40 Gy in rabbits, and complications seemed to vary due to individual differences in radiation tolerance.     

The influence of human T lymphotropic virus type I infection on the outcome of cardiovascular surgery

OBJECTIVE: Human T lymphotropic virus type I infects CD4(+) T cells and affects cell-mediated immunity. Cardiopulmonary bypass transiently alters lymphocyte subsets, resulting in a reduction in CD4(+) T cells and an increase in CD8(+) T cells. We proposed that cardiovascular operations and human T lymphotropic virus type I infection may act synergistically, resulting in serious damage to cell-mediated immunity. METHODS: A total of 517 consecutive patients who were preoperatively screened for anti-human T lymphotropic virus type I antibody and underwent cardiovascular operations with cardiopulmonary bypass were enrolled in this study. Of the 517 patients, 82 (16%) had positive test results for anti-human T lymphotropic virus type I antibody. The surgical outcome of patients with positive and negative results for anti-human T lymphotropic virus type I antibody was analyzed retrospectively. RESULTS: There was no difference between the 2 groups with respect to early mortality. Distribution of survival curve was also not significantly different (P =.5; mean follow-up duration, 2.4 +/- 1.8 years [range, 0-9.4 years] and 3.2 +/- 2.8 years [range, 0-9.8 years]) in the groups with positive and negative antibody results, respectively). In particular, long-term follow-up did not reveal adult T-cell leukemia or human T lymphotropic virus type I-associated myelopathy, and occurrence of neoplasm did not differ between groups. Early infectious complication was, however, significantly higher in the group with positive antibody results than in the group with negative results (P =.02). Logistic regression analysis revealed human T lymphotropic virus type I infection as a significant risk for this complication (P =.04; odds ratio, 2.5; 95% confidence interval, 1. 0-5.8). CONCLUSION: A combination of human T lymphotropic virus type I infection and cardiovascular operation is believed to increase the potential risk of infectious complications shortly after the operation. However, this synergistic effect seems to be transient and has little influence on long-term prognosis.     

Pre-emptive analgesia with intravenous ketamine reduces postoperative pain in young patients after appendicectomy: a randomized control study

Thirty-six young patients (12-17 years old) for appendicectomy were randomly allocated to receive ketamine 0.5 mg.kg-1 (K 0.5 group; n = 12), ketamine 1.0 mg.kg-1 (K 1.0 group; n = 12), or lactated Ringer's solution 5 ml (control group; n = 12), which was administered intravenously before incision. After the surgery, all patients received a nonsteroidal anti-inflammatory drug (NSAID) without limitation as requested by the patient. Pain scores at rest and on movement were assessed at 6-10 hr, 24 hr, and 48 hr post-operatively using a visual analogue scale. The frequency at which NSAID was given for postoperative analgesia in the first 48 hr after the surgery was recorded. The patients in the K 0.5 and K 1.0 groups had significantly lower pain scores at rest 6-10 hr postoperatively than the patients in the control group (P < 0.05). Additionally, the patients in the K 1.0 group had a significantly lower pain score on movement 6-10 and 48 hr postoperatively than those in the control group (P < 0.05). The K 0.5 and K 1.0 groups each used significantly less NSAID during the 48-hr postoperative period than the control group (P < 0.05). Intravenous administration of ketamine before incision was associated with decreases in pain at rest 6-10 hr postoperatively and a reduction in NSAID requirement after appendicectomy. Administration of ketamine 1.0 mg.kg-1 prior to incision was superior to administration of 0.5 mg.kg-1 in relief of pain on movement after the surgical procedure.     

The effects of intravenous anesthetics, propofol, fentanyl and ketamine on the excitability of spinal motoneuron in human: an F-wave study

We have investigated the effects of various intravenous anesthetics, propofol, fentanyl and ketamine on the excitability of spinal motoneuron using an F-wave analysis in a total of 28 patients. All patients were divided randomly into three groups as follows; 2 mg.kg-1 intravenous bolus injection followed by 6 mg.kg-1.h-1 infusion of propofol (P group), 1 mg.kg-1 intravenous bolus injection followed by 1 mg.kg-1.h-1 infusion of ketamine (K group), and 5 micrograms.kg-1 injection of fentanyl (F group). The F-wave was determined after supramaximal electrostimulation of the median nerve in distal point. After establishing stable baseline values, intravenous injection of one of the three anesthetics was applied. The F-wave was recorded 3 minutes after the time of bolus administration. We found a significant (P = 0.018) reduction of the persistence from 77.5 +/- 15.2 to 40.9 +/- 16.8% in the propofol group. On the other hand, no significant changes in F-wave parameters were found in ketamine, or fentanyl group. These results suggested that motoneuron excitability in spinal cord could be inhibited by anesthetic dose of propofol, but not by ketamine or fentanyl.     

Contrast Enhancement of the Normal Infundibular Recess Using Heavily T2-weighted 3D FLAIR

Purpose: The purpose of the present study was to evaluate contrast enhancement of the infundibular recess in the normal state using heavily T2-weighted 3D fluid-attenuated inversion recovery (FLAIR) (HT2-FLAIR).Methods: Twenty-six patients were retrospectively recruited. We subjectively assessed overall contrast enhancement of the infundibular recess between postcontrast, 4-hour (4-h) delayed postcontrast, and precontrast HT2-FLAIR images. We also objectively conducted chronological and spatial comparisons by measuring the signal intensity (SI) ratio (SIR). Chronological comparisons were performed by comparing SI of the infundibular recess/SI of the midbrain (SIR_IR-MB). Spatial comparisons were conducted by comparing SI on postcontrast HT2-FLAIR/SI on precontrast HT2-FLAIR (SIR_Post-Pre) of the infundibular recess with that of other cerebrospinal fluid (CSF) spaces, including the superior part of the third ventricle, lateral ventricles, fourth ventricle, and interpeduncular cistern.Results: In the subjective analysis, all cases showed contrast enhancement of the infundibular recess on both postcontrast and 4-h delayed postcontrast HT2-FLAIR, and showed weaker contrast enhancement of the infundibular recess on 4-h delayed postcontrast HT2-FLAIR than on postcontrast HT2-FLAIR. In the objective analysis, SIR_IR-MB was the highest on postcontrast images, followed by 4-h delayed postcontrast images. SIR_Post-Pre was significantly higher in the infundibular recess than in the other CSF spaces.Conclusion: The present results demonstrated that the infundibular recess was enhanced on HT2-FLAIR after an intravenous gadolinium injection. The infundibular recess may be a potential source of the leakage of intravenously administered gadolinium into the CSF.     

Successful Surgical and Endovascular Multidisciplinary Therapy for Mid-aortic Syndrome with Complicated Atherosclerotic Comorbidities in an Older Patient

Mid-aortic syndrome (MAS) is a rare vascular disorder that causes refractory hypertension. A 76-year-old woman was hospitalized for acute heart failure (HF) with drug-resistant hypertension; other comorbidities included epigastric artery rupture, old myocardial infarction, an intraventricular thrombus, and a cerebral artery aneurysm. Angiography revealed severe narrowing of the descending aorta, which led to the diagnosis of MAS. Although intensive medical treatment improved her HF, optimal blood pressure (BP) could not be achieved. Percutaneous coronary intervention and surgical bypass for diseased aorta was then performed in two stages, resulting in the achievement of optimal BP and alleviation of HF.