Biomedical subjects
Publications and source records attributed to C Teo.
A sciatic nerve lesion is uncommon. We report the utility of the endoscope in an 18-year-old female with multiple lesions of her sciatic nerve. Somatosensory evoked potentials and MRI were indicative of a sciatic nerve lesion. We describe a simple technique of endoscopic exploration of the sciatic nerve to assist intraoperative decision making.
Schwannomas are rare benign tumours of nerve sheath cells of neural crest origin. Often these tumours are solitary and encapsulated. Multiple schwannomas can arise from the peripheral nervous system including cranial nerves, spinal roots, the brachial and lumbar-sacral plexus or major peripheral nerves. We report an extremely rare case of schwannomatosis of the sciatic nerve in a young female and include a comprehensive literature review. Treatment options are discussed.
Technical advances in neurosurgery follow a general philosophy favouring less invasive means of managing surgical disease. We describe a patient with a symptomatic type I Chiari malformation managed by posterior fossa decompression using endoscopic techniques. Technical considerations, including drawbacks of the procedure, are discussed.
This article reviews the range of hydrodynamic disorders affecting the CSF circulation. Initially consideration is given to questions of definition and classification. A scheme for the practical, clinical analysis for the diagnosis of such disorders is then presented. The physiology and pathophysiology of the CSF circulation is reviewed, with particular emphasis on issues that remain unresolved. This provides a background to consideration of the adverse consequences of abnormal CSF hydrodynamics, again focusing on areas where further information is required. Methods of clinical investigation of CSF hydrodynamics are reviewed, followed by general considerations of treatment. Finally, each of the main, clinically important, forms of disordered CSF hydrodynamics is briefly considered, with particular emphasis, again, on areas where current knowledge is deficient. The conditions considered include hydrocephalus of various forms (childhood, adult, arrested, multi-compartment), infantile macrocephaly, arachnoid and glioependymal cysts, syringo- and hydromyelia, pseudotumour cerebri, impaired cranial venous outflow, altered CSF composition, shunt obstruction without ventricular enlargement and low-CSF-pressure states.
Cefpodoxime is an oral third-generation cephalosporin used for the treatment of acute upper-respiratory tract infections caused by susceptible bacteria in children. Although not indicated for the treatment of bacterial meningitis, it is used to treat other infections produced by organisms associated with meningitis and may obscure the result of cerebrospinal fluid (CSF) cultures in children who develop meningitis while receiving oral antibiotics if sufficient concentrations are achieved in the CSF. This study evaluated the disposition of cefpodoxime and penetration into CSF in piglets. Fifteen Landacre-Camborough cross piglets (10-20 days old) received cefpodoxime proxetil oral suspension (10 mg/kg). Repeated plasma and CSF samples were collected over 24 hours for quantitation of cefpodoxime by HPLC. Pharmacokinetic analysis was performed on both plasma and CSF data. The plasma concentration versus time data for cefpodoxime were best characterized using a one-compartment model with first-order absorption. The mean (+/- SD) pharmacokinetic parameters for Cmax, tmax, and AUC0-infinity were 23.3 +/- 12.9 mg/L, 3.9 +/- 1.4 h, and 237 +/- 129 mg/L.h, respectively. CSF/plasma ratios for AUC0-infinity demonstrated a mean cefpodoxime penetration of approximately 5%. CSF penetration of cefpodoxime was evident following a single oral dose of cefpodoxime proxetil suspension. Despite the small percentage of total cefpodoxime dose distributing into the CSF, the resultant concentrations approached or exceeded the MIC90 for many bacterial pathogens considered susceptible to cefpodoxime. Accordingly, clinicians should use caution in the interpretation of CSF cultures in patients who develop clinical signs and symptoms consistent with meningitis and who have been previously treated with cefpodoxime.
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Techniques for skull base surgery have become well established over the last 10 years. Most of these techniques are used in adult patients for skull base tumors and neurovascular diseases. There are very few large series of pediatric patients in whom skull base approaches have been used, because of the rarity of these conditions. The authors would like to present a relatively large series of 26 pediatric patients who underwent skull base approaches for tumor resection. These tumors involved the anterior cranial base in 5 patients, the medial cranial skull base in 4 patients, and the posterior cranial base in 12 cases. Five patients had tumors that involved two or more fossae. The overall complication rate was 57%, which included temporary cranial nerve palsies, CSF leak and infection. Patients with permanent complications were 8 in number (37%). There was 1 postoperative death from pneumonia approximately 6 weeks after surgery. Complete tumor removal was achieved in 24 of the 26 patients. Skull base tumors in children are often extensive and present significant surgical challenges. Although complete tumor extirpation is the goal in most pediatric patients, this is often achieved only with some morbidity. This paper demonstrates the effectiveness of skull base approaches for these tumors and underscores the high stakes involved.
OBJECTIVE: To propose endoscopic treatment as an effective initial alternative for patients with a trapped fourth ventricle. METHODS: We reviewed the records of the last 16 consecutive patients with a symptomatic trapped fourth ventricle seen at the Arkansas Children's Hospital. The first eight patients underwent a shunt procedure; the next eight had endoscopic procedures. The shunt procedures consisted of either separate shunts or combined supra- and infratentorial shunts with shared distal catheters. The endoscopic procedures consisted of either fenestration into the lateral ventricle or aqueductal plasty with or without a stent. RESULTS: All patients underwent successful procedures with good outcomes, although the patients with shunts appeared to have a higher-than-expected rate of revision (50%). Seven revisions were performed on four patients, with a complication rate of 25%. Of the patients who had endoscopic procedures, one eventually required a shunt. The overall complication rate for patients who had endoscopic procedures was also 25%. CONCLUSION: Endoscopic treatment of the trapped fourth ventricle is effective in most cases. In view of the higher-than-expected revision rate with fourth ventricular shunts and an equivalent complication rate, endoscopic treatment is a reasonable initial treatment option for patients with a trapped fourth ventricle.
We previously reported that the P1 or P50 midlatency evoked potential underwent decreased habituation or disinhibition in patients with Parkinson's Disease. This sleep state-dependent response appears to be generated by cholinergic elements of the reticular activating system. We attempted to determine if the decreased habituation or disinhibition of the P1 potential would be altered by bilateral pallidotomy. Twenty-three patients who met inclusion criteria for surgery underwent pre- and post-operative evaluation using a Modified United Parkinson's Disease Rating Scale (UPDRS) and P1 potential recordings. Decreased habituation of the P1 potential was determined using a paired stimulus paradigm in which click stimuli were presented at 250, 500 and 1000 msec interstimulus intervals (ISI). Pre-operatively, patients showed disinhibition of the P1 potential at the 250 msec ISI (60 37% vs. 21 20%) and 500 msec ISI (78 47% vs. 43 31%) compared to age-matched control subjects. Post-operatively, the same patients showed a significant improvement in habituation of the P1 potential at the same ISIs (250 msec 37 21%; 500 msec 43 32%). UPDRS scores for these patients pre-operatively were 59 18 and 24 11 post-operatively, resulting in a significant reduction in symptom severity. We conclude that bilateral pallidotomy resulted in a significant improvement in symptom ratings and reduced the disinhibition of the P1 midlatency evoked response.
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The P1 midlatency auditory evoked potential was studied in patients with Parkinson's disease and compared to that in age-matched controls. Habituation of the potential was determined by using a two-click stimulus paradigm in which the stimuli were presented at 250-, 500-, and 1,000-ms interstimulus intervals. Results showed that habituation of the P1 potential had a statistically significant decrease at the 250-ms and 500-ms interstimulus intervals in patients with Parkinson's disease compared to normal controls. The degree of decreased habituation was found to increase with severity of the disease such that stage 5 patients showed greater decreases in habituation compared to stage 4, as did stage 4 compared to stage 3. These findings may be explained by the presence of a dysregulation of sensory processing, possibly by elements of the reticular activating system, including the pedunculopontine nucleus, in Parkinson's disease.
Fluoride exposure in early life has an effect on dental caries experience, but does it affect tooth wear in later life? Ninety-six South East Queensland subjects were studied. Their histories revealed three groups; a fluoride (F-) in water supply, a F- by supplement, and a non-fluoridated (non F-) group. Significantly higher caries experience was found in the non-F- group compared with F- in water group and the F- supplement group. No statistically significant difference in caries experience was found between the F- in water and F- supplement groups. Overall, tooth wear affected more sextants of the dentitions of non-fluoridated, high-caries subjects than of fluoridated low-caries subjects. Comparisons of wear patterns on sextants of the dentitions, between the fluoridated and non-fluoridated groups, revealed that in sextants where attrition was present no marked differences were discernible between the two groups. However, in most sextants where incisal, palatal, occlusal or non-occlusal erosion was found, this type of wear was commoner in non-fluoridated subjects. The exceptions were the mandibular molar sextants, where prior fluoride-exposure did not appear to protect against occlusal erosion patterns. This study showed that fluoride exposure during the first 12 years of life, which reduced dental caries in this population, may also protect teeth from wear to some extent.
Thirty patients between the ages of 7 months and 24 years were treated surgically for symptomatic Chiari II malformation at the Arkansas Children's Hospital. All patients underwent at least bony decompression of the malformation. Assessments of the patients' conditions were made at 6 weeks and 1 year after surgery, and complications of surgery were noted. For a majority of the patients, the presenting symptoms were resolved following treatment (74% at 6 weeks and 80% at 1 year). Partial resolution occurred in several of the patients (17% at 6 weeks and 14% at 1 year). A small number remained the same at 6 weeks (6%) and at 1 year (3%), while 1 patient was worse after surgery. Ten of the patients with complete resolution in the short term required repeat surgery an average of 49 months after their original operation, after which they again attained complete resolution of their symptoms. Scales for clinical, radiographic and operative grading of the patients' conditions as mild, moderate or severe were devised, and these were employed to characterize the condition of each patient. Patients in each grading category had good results, with rates of complete symptomatic resolution ranging from 67 to 100%. Severity in each category was found to be well correlated with eventual recurrence of symptoms and need for reoperation.
Currently available animal models for the study of treatment of aneurysms are either expensive or yield unreliable results. An animal series was devised to address both of these problems by creating a new animal model. Twelve Sprague-Dawley rats were used to demonstrate that a vein-pouch aneurysm could be constructed at a surgically created carotid bifurcation. Patency rates, growth dynamics, and histologic morphology were studied at three time intervals. A 100% patency rate at the aneurysm orifice was achieved with one-third of the aneurysms showing varying degrees of partial apical thrombosis. A growth pattern was established over the study period. Magnetic resonance angiography and digital subtraction angiography were successfully employed to study a small number of additional aneurysms. Our conclusion is that a bifurcation aneurysm can be constructed in the rat with high patency rates and predictable saccular morphology which resembles most human intracranial aneurysms. This inexpensive animal model can be used to study novel modalities for the treatment of aneurysms.
Neuroendoscopy is rapidly becoming an essential part of the neurosurgeon's repertoire. Currently, very few studies have identified the complications of this new technique, yet many have warned of the steep learning curve associated with its practice. We have reviewed the last 173 neuroendoscopic procedures performed by one surgeon and identified two distinct groups of complications: those that have clinically significant sequelae and those that cause concern intraoperatively but no overt clinical problems. The 173 procedures were performed on 152 patients. Of these patients, 11 suffered significant complications (7%). Twenty-two of the procedures were complicated by intraoperative problems (13%). The incidence of insignificant complications appeared to decrease with experience, whereas that of the significant ones did not. These complications occurred in association with a wide variety of operations over a 2-year period. We conclude that neuroendoscopy is a relatively safe technique with an overall 7% complication rate and a steep learning curve, and that, with a few simple guidelines, it can be employed by all neurosurgeons for the betterment of their patients.
Telomeric association (tas) is a cytogenetic phenomenon in which chromosome ends fuse to form dicentric, multicentric, and ring chromosomes. We observed clonal tas in six pediatric solid tumors of various types and histological grades studied using short-term in situ culture and G-banding techniques. These tumors included a neurilemoma, an undifferentiated (embryonal) sarcoma of the liver (UESL), two anaplastic astrocytomas (AA), one case of glioblastoma multiforme (GBM), and a neuroblastoma (NB) of the kidney. Cytogenetic data from all six tumors demonstrated multiple numerical and structural aberrations including tas. The tas appeared to be a secondary aberration in these tumors, however, it was possible to follow the progression of the telomeric chromosome aberrations in several cases. In all but one case (UESL) the loss of chromosome segments occurred. Tas of 11p was observed in three of the six tumors, two of which showed the subsequent loss of 11p (AA and AB). In addition, tas of 4p was seen in three tumors, two of which showed clonal tas of 4p with 22q. Tas of 10p, 21p, and 22q were all observed in at least two different tumors. The clonal telomeric fusions of 4p with 22q, recurring tas of 11p, and the subsequent loss of the short arm of 11 demonstrated here, suggests that some chromosome regions are subject to nonrandom instability and sometimes loss.
Endoscopic third ventriculostomy (ETV) was performed between July 1978 and July 1995 on 69 patients with hydrocephalus and myelomeningocele. Most of the patients had been previously shunted, although in 14 patients ETV was the initial treatment. Patient selection was based on preoperative imaging studies suggesting noncommunicating hydrocephalus. Only 2 patients exhibited transient hypothalamic dysfunction with complete resolution. Patients were assessed by their clinical status, imaging characteristics, and, in some cases, formal psychometric studies. The overall success rate was 72%, although selecting only patients who have been previously shunted or who were over 6 months of age at the time of endoscopy increases this to 80%. Our results indicate that ETV is a safe and effective means of treating hydrocephalus in the older spina bifida population and offers the hope of long-term, shunt-independent life for selected patients.