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Biomedical subjects

D G Thomas

Publications and source records attributed to D G Thomas.

At least 91 records · Page 5Linked to original sources
PubMed1995

Stereotactically-guided craniotomy for cavernous angiomas presenting wit epilepsy.

With the wider availability of magnetic resonance imaging cavernous malformations are being recognised with increasing frequency in those patients presenting with intractable epilepsy. Surgical resection is the treatment of choice. However, because these lesions are usually small and may be located in eloquent areas stereotactic resection should be considered. Stereotactically-guided resection of pathologically verified cavernous angiograms was performed in 10 patients in this series presenting with epilepsy (8 males, 2 females, mean age 32 years). Eight patients presented with medically intractable epilepsy (5 complex partial seizures, 3 grand mal seizures). Of the remaining patients one experienced multiple episodes of haemorrhage and the other headaches (with a non-diagnostic scan) both in association with epilepsy. Pre-operative localisation of the motor strip was determined in one case by functional MRI. Following resection of these lesions all patients experienced improved seizure control with a mean follow-up period of 22 months. The mean postoperative hospital stay was 5.1 days with no surgical complications recorded. We conclude that stereotactically-guided resection offers significant advantages in the management of cavernous malformations. Surgical indications for operative resection would include medically refractory epilepsy, repeated haemorrhage and those cases where there is diagnostic uncertainty.

Adolescent↗
PubMed1995

Anorectal function in patients with complete spinal transection before and after sacral posterior rhizotomy.

BACKGROUND/AIMS: The implantation of spinal stimulators to facilitate defecation in patients with complete spinal transection involves division of the posterior sacral nerve roots. The aim of this study was to investigate the role of spinal reflexes in anorectal function. METHODS: Anorectal manometry and electromyography were performed in 14 patients with supraconal spinal cord transection (C6-T12) before and after complete sacral posterior rhizotomy and in 30 normal controls. RESULTS: Patients with spinal transection lost conscious control of the external anal sphincter. Reflex responses to intra-abdominal pressure and to rectal distention were eliminated after rhizotomy, indicating that they are spinal reflexes. Rhizotomy also eliminated giant rectal contractions induced by rectal distention in these patients. In contrast, the exaggerated sphincter relaxation induced by rectal distention was not influenced by rhizotomy. Discriminant rectal sensation was lost, but patients with thoracic cord lesions perceived a dull pelvic sensation during rectal distention even after rhizotomy. CONCLUSIONS: The exaggerated anorectal smooth muscle responses and absent conscious control of the anorectum may explain why patients with complete spinal transection experience uncontrollable reflex defecation, and the persistence of external anal sphincter contraction during straining may impair fecal expulsion. The elimination of these responses after posterior rhizotomy prevented reflex defecation while facilitating manual evacuation.

Adult↗
PubMed1995

Intermittent catheterization following enterocystoplasty.

OBJECTIVE: To assess the segment of bowel used in enterocystoplasty and the need to perform intermittent self-catheterization (ISC) after enterocystoplasty for the treatment of incontinence. PATIENTS AND METHODS: Of 123 patients undergoing enterocystoplasty, 77 (mean age 29.5 years, range 13-61) had neurogenic disease (NB group) and 46 (mean age 45.7 years, range 16-74) had non-neuropathic bladders (NNB group). The success of enterocystoplasty, with respect to the segment of bowel used and the need for ISC, was assessed during a follow-up of 6-125 months. RESULTS: Ileum was used in 84 (63.8%), ileum and caecum in 19 (15.4%) and sigmoid in 20 (16.3%) patients. In the NB group, more patients had a sigmoid cystoplasty (24.7 vs 2.2%) and less (67 vs 80%) had an ileo-cystoplasty than in the NNB group. A total of 87 (71%) patients required ISC; 63 (82%) of the NB group and 24 (52%) of the NNB group. The influence of the intestinal segment was conspicuous in the NB group, with 82% and 95% of patients with ileocaecal and sigmoid cystoplasty needing ISC against 77% of those patients with ileal cystoplasty. The difference was not so evident in the NNB group. CONCLUSIONS: A social continence rate of 93.6% in the NB and 84.8% in the NNB patients was achieved, partly due to the patients' success with ISC, a necessary skill to be mastered by all patients before undergoing enterocystoplasty.

Adolescent↗
PubMed1995

Loss of heterozygosity for DNA polymorphisms mapping to chromosomes 10 and 17 and prognosis in patients with gliomas.

Twenty nine patients with gliomas were investigated for loss of heterozygosity for 40 DNA polymorphisms in tumour DNA, particularly concentrating on those mapping to chromosomes 10 and 17. Eight of 18 grade IV gliomas showed loss of sequences from chromosomes 10, 17, or both. The data suggested total loss of one copy of chromosome 10, but there were interstitial deletions of the short arm of chromosome 17 in three of five tumours. Heterogeneous interstitial deletions of chromosome 17 were also found in two lower grade astrocytomas and one benign oligodendroglioma. The striking finding of this study was that patients with high grade gliomas whose tumours exhibited loss of heterozygosity for chromosomes 10, 17, or both survived significantly longer after surgery (median 17.4 months) than those whose tumours did not show loss of these chromosomes (median 6.7 months). These findings suggest that there is a subset of particularly aggressive high grade gliomas with no currently known molecular genetic abnormalities.

Adult↗
PubMed1995

Intramedullary spinal cord abscess: case report.

Intramedullary spinal cord abscesses are rare lesions with a poor prognosis unless diagnosed and treated promptly. We report a case of a Nigerian man with tuberculous meningitis that was complicated by an intraspinal cord abscess and was treated surgically. The literature regarding this uncommon clinical entity is reviewed.

Abscess↗
PubMed1995

Computer planning of stereotactic iodine-125 seed brachytherapy for recurrent malignant gliomas.

At St Thomas' Hospital, we have developed a computer program on a Titan graphics supercomputer to plan the stereotactic implantation of iodine-125 seeds for the palliative treatment of recurrent malignant gliomas. Use of the Gill-Thomas-Cosman relocatable frame allows planning and surgery to be carried out at different hospitals on different days. Stereotactic computed tomography (CT) and positron emission tomography (PET) scans are performed and the images transferred to the planning computer. The head, tumour and frame fiducials are outlined on the relevant images, and a three-dimensional model generated. Structures which could interfere with the surgery or radiotherapy, such as major vessels, shunt tubing etc., can also be outlined and included in the display. Catheter target and entry points are set using a three-dimensional cursor controlled by a set of dials attached to the computer. The program calculates and displays the radiation dose distribution within the target volume for various catheter and seed arrangements. The CT co-ordinates of the fiducial rods are used to convert catheter co-ordinates from CT space to frame space and to calculate the catheter insertion angles and depths. The surgically implanted catheters are after-loaded the next day and the seeds left in place for between 4 and 6 days, giving a nominal dose of 50 Gy to the edge of the target volume. 25 patients have been treated so far.

Brachytherapy↗
PubMed1995

Estimation of resection volumes in lesional epilepsy surgery.

An MR-based method for measuring resection volumes in lesional epilepsy surgery is described. The volume of the preoperative lesion, the resection cavity and, as a result, the volume of the brain surrounding the lesion resected during surgery have been calculated in 13 patients.

Adolescent↗
PubMed1994

Minimally invasive surgery. Neurosurgery.

The introduction of minimally invasive techniques has greatly improved results for intracranial neurosurgery. Stereotaxy and improved imaging techniques have reduced surgical trauma by allowing surgeons to plan the least damaging route to operative sites and by increasing surgical precision. Stereotaxy has also allowed brain biopsies to be taken from sites such as the brain stem, which were rarely sampled before because free hand biopsy was so dangerous. Brain tumours can now be treated by interstitial radiotherapy--stereotactic insertion of catheters into the lesion for loading of radioactive iodine--or radiosurgery--focusing of intense beams of radiation on lesions without needing surgical incisions. Endoscopic neurosurgery can be used to reach cavities such as the ventricular system or cystic tumours. With interventional neuroradiology fine catheters can be introduced into most vessels in the cranium for embolisation or dilatation. The development of augmentative functional neurosurgery means that movement disorders, epilepsy, and intractable pain can be treated with implanted neurostimulating electrodes. Future developments will probably include frameless stereotaxy, when the rigid attachment of stereotactic apparatus to the patient's head can be dispensed with, and at least partial automation of procedures such brain biopsy.

Craniotomy↗
PubMed1994

Survival following interstitial brachytherapy for recurrent malignant glioma.

The treatment of recurrent malignant glioma is difficult and at present largely disappointing. Furthermore the results of any treatment modality need to be interpreted with knowledge regarding patient selection and timing of treatment. The results of interstitial brachytherapy using iodine-125 in 23 patients are presented. There were no operative complications. Median survival time from tumour recurrence and implantation was 36 and 25 weeks respectively. Karnofsky Performance Status (KPS) was significantly associated with survival, though patient age, original tumour histology, prior chemotherapy, and time to recurrence were not. Treatment does confer modest survival benefit as compared to controls, but our results are not as impressive as others. Reasons for this finding are discussed.

Adult↗
PubMed1994

Minimally invasive stereotaxy: clinical use of the Gill-Thomas-Cosman (GTC) repeat stereotactic localiser.

The Gill-Thomas-Cosman (GTC) repeat stereotactic localiser allows frame-based stereotaxy to be performed in a minimally invasive manner by using dental fixation rather than traditional skull pins. The GTC enables accurate relocation in the same stereotactic space so that image acquisition and surgery can be separated if necessary. The device is especially suitable for fractionated stereotactic radiotherapy where it conveniently provides both patient-frame and frame-couch fixation on a repeatable basis.

Biopsy↗
PubMed1994

Combined bladder neck suspension and augmentation cystoplasty for neuropathic incontinence in female patients.

OBJECTIVE: To perform bladder neck suspension simultaneously with augmentation cystoplasty in female patients where sphincteric incompetence was not the sole cause of impaired functional bladder capacity. PATIENTS AND METHODS: During an 8-year-period, 26 female patients (mean age 14, range 5-39) were treated with a Marshall-Marchetti plus cystoplasty (Liverpool) or a colposuspension plus clam cystoplasty (Sheffield). All had marked sphincteric incompetence compounded by detrusor hyper-reflexia and/or non-compliance. The patients were followed up for a mean period of 30 months (range 8-80). RESULTS: There were no major complications. At follow-up 23 (88%) were dry by day on a regime of intermittent self-catheterization. Nine patients were taking adjuvant medication, usually for prevention of nocturnal enuresis. CONCLUSION: The results compare tolerably with those of all alternative procedures, including the more elaborate reconstructions (e.g. Kropp procedure) and the expensive artificial urinary sphincter.

Adolescent↗
PubMed1994

Reiter's syndrome in an adolescent girl.

This report describes a 14-year-old girl who presented with an Escherichia coli urinary tract infection followed by diarrhoea, arthritis and iritis. She had continuing symptoms intermittently for six months, but was HLA-B27 antigen negative. The occurrence of Reiter's syndrome is unusual in young females and we are not aware of any reports of reactive arthritis following E. coli urinary tract infection in children.

Adolescent↗
PubMed1994

A patient-to-computed-tomography image registration method based on digitally reconstructed radiographs.

An automatic method for the accurate registration of computed tomography (CT) data with two camera-calibrated radiographs is presented. The registration is based on the skull as visualized both in the plain radiographs and in radiographs digitally reconstructed from CT. A reference coordinate system is established based on the radiographic projection parameters obtained using an angiographic stereotactic localizer. The CT-derived reconstructed radiographs are aligned iteratively at multiple resolutions until a best match is found by adjusting the position and orientation of the CT data set relative to the reference coordinate system. The results of experiments with a skull phantom performed under stereotactic control which show that reliable registration is possible with an accuracy better than 1 mm are presented. Possible applications include intraoperative patient-to-CT frameless registration and registration of radiographic data with frameless CT for depth electroencephalogram electrode position confirmation.

Algorithms↗
PubMed1994

Voxel-based localization in frame-based and frameless stereotaxy and its accuracy.

The problem of accurate stereotactic localization and registration of targets in computed tomography (CT) data sets is addressed, in particular the effect of using a single transformation matrix to map voxel coordinates onto stereotactic coordinates. An algebraic approach to the calculation of stereotactic target coordinates in tomographic data acquired with conventional stereotactic localizers is presented. The volume transformation matrix (VTM) is discussed, which is useful for the registration of volumetric data sets, and also corresponds to the rigid body transformation matrix used in many so-called frameless registration methods. The VTM can lead to accuracy degradation, in particular due to patient movement during scanning. Simulations were performed and CT data sets acquired with patients fitted with the CRW or the GTC stereotactic localizer were analyzed. Comparison of STM- and VTM-derived stereotactic coordinates shows an average overall registration error of 0.1 mm for anesthetized patients and in the range 0.6-1.4 mm for nonanesthetized patient. Accuracy maps are described that enable the user to visualize the registration error in relation to the data. It is shown that the effect of fiducial point localization error and patient movement for VTM-based localization is minimized when all available fiducials in the region of interest are used. The significance of these results is discussed, and methods are proposed to minimize these effects for frame-based and frameless registration methods.

Humans↗
PubMed1994

Image guided audit of surgery for temporal lobe epilepsy.

Studies on surgery for temporal lobe epilepsy are hampered by lack of information about the actual surgery that has taken place. A method is described for accurately measuring the volumes of resection by MRI after surgery. Ten cases of surgically treated temporal lobe epilepsy (nine non-tailored resections, one selective amygdalohippocampectomy) are presented to show the technique. Indices of extent of resection in both the mesiobasal and lateral temporal lobe compartments have been measured, compared, and evaluated. By comparison with identical preoperative volumetric MRI the hippocampal resections have been correlated with the demonstrated hippocampal volume loss, thought to be of relevance in the aetiology of temporal lobe epilepsy. Detailed postoperative audit in this manner is vital in providing a rational basis for follow up studies of outcome.

Adolescent↗
PubMed1994

Long-term follow up of dorsal root entry zone lesions in brachial plexus avulsion.

The long-term results of 44 patients who underwent dorsal route entry zone (DREZ) lesioning for pain secondary to brachial plexus avulsion are reported with a mean clinical follow up period of 63 months. The postoperative analgesic effect was judged by the patients as being good (greater than 75% pain reduction), fair (25-75% pain reduction), or poor (0-25% pain reduction). With these criteria 35 patients (77%) had continuing good (30 cases, 68%) or fair (five cases, 11%) pain relief at the time of final follow up. Eight cases (18%) had persisting neurological deficits, although these were generally mild. DREZ thermocoagulation is an effective procedure for relieving deafferentation pain. The analgesic effect which is produced in the early postoperative period seems to be maintained in the long-term.

Adult↗