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Biomedical subjects

D G Thomas

Publications and source records attributed to D G Thomas.

At least 109 records · Page 6Linked to original sources
PubMed1994

Accurate frameless registration of MR and CT images of the head: applications in planning surgery and radiation therapy.

PURPOSE: To evaluate the feasibility and efficacy of a three-dimensional image registration technique for planning skull base surgery, performing frameless image registration for stereotaxic neurosurgery, and staging nasopharyngeal carcinoma. MATERIALS AND METHODS: Computed tomographic (CT) and magnetic resonance (MR) images from 35 patients were registered by identifying 12-16 homologous landmarks with each modality. Images were displayed as overlaid sections or rendered three-dimensional scenes. The clarity of the combined images from 15 patients undergoing skull base surgery was compared with that of the conventional displays. RESULTS: Images were combined for three applications, with an accuracy of 1-2 mm. For the 15 patients undergoing skull base surgery, the combined images were significantly better at depicting the relationship between bone and lesion than conventional display (P < .01). CONCLUSION: MR and CT images of the head can be accurately registered without using external markers or substantially altering image acquisition protocols. The resulting images can show the radiologic information more clearly than conventional viewing.

Adult↗
PubMed1993

Multimodal imaging integration and stereotactic intracerebral electrode insertion in the investigation of drug resistant epilepsy.

Insertion of intracerebral electrodes for EEG recording is sometimes necessary during the pre-operative evaluation of patients with drug resistant epilepsy to define the site of seizure onsets. The precise and accurate placement of the electrodes requires a stereotactic technique of insertion based on correlated information derived from computerised imaging and stereotactic angiography. Described methods of multimodal stereotactic image integration present limitations in terms of satisfactory relocation and ability to spread data acquisition over a period of time. An alternative method of stereotactic acquisition of multimodal image information using the Gill-Thomas stereotactic repeat localiser is presented. Digital Angiographic (DSA), Computerised (CT) and Magnetic Resonance Imaging (MRI) data were correlated and used for target selection. The positional accuracy of the electrodes was confirmed repeatedly during the recording period with standard radiographic and MRI means and found to be satisfactory. There were no permanent complications in any of the patients included in the study. Stereoangiography correlative to computerised neuro-imaging offered a high degree of safety during the operation. Non-invasive relocation was an important feature of the combined system which was particularly helpful and duly appreciated by the patients. The temporal freedom provided during the investigative and operative period offers the advantage of an unhurried multi-image integration and targeting combined with less discomfort for the patient. The positional accuracy of the electrodes was easily verified during the post-operative period and this information added to the electroence-phalographic localising value of the technique.

Brain↗
PubMed1993

Patient's assessment of outcome after three surgical procedures for the management of trigeminal neuralgia.

Four hundred and seventy five patients with trigeminal neuralgia underwent cryotherapy (145), radiofrequency thermocoagulation (265) or microvascular decompression 65) and were then followed up for mean time of 45 months. Outcome of treatment was assessed not only by the clinicians but also by a postal questionnaire. The presence of anxiety and depression was determined and compared to 51 patients due to undergo surgery. The median time to recurrence for the cryotherapy patients and the radiofrequency thermocoagulation patients were 6 and 24 months, respectively. At 5 years 38% of the microvascular decompression patients had had a recurrence of neuralgia. There was one operative death in the radiofrequency thermocoagulation group. Patients in all three groups were satisfied with their treatment but the questionnaires showed that clinicians under-report the recurrence of pain and post operative complications. Pre-operatively depression and anxiety are high but post-operatively only 15% were depressed. Patients need careful pre-operative assessment which includes the McGill Pain Questionnaire and they should be given a choice about which surgical method would be most suitable in their case. Printed information should be available to supplement the consultation. This would ensure the patients' expectations matched up with the results as they would be aware of possible outcomes.

Adult↗
PubMed1993

Open stereotactic amygdalohippocampectomy--clinical, psychometric, and MRI follow-up.

The clinical results of six cases of open stereotactic amygdalohippocampectomy for medically intractable epilepsy are presented. Outcome in terms of seizure control (highly satisfactory in five patients) and neuropsychological sequelae (all cases had poor functioning of the contralateral temporal lobe pre-operatively) are detailed. In addition the use of post-operative Magnetic Resonance Imaging (MRI) is demonstrated and shown to be a valuable tool in providing the crucially accurate baseline that is required for more meaningful follow-up outcome studies.

Adult↗
PubMed1993

Reliability of histological diagnosis including grading in gliomas biopsied by image-guided stereotactic technique.

We report clinical and pathological data of 419 image-guided stereotactic biopsies. In the present series the diagnostic yield, estimated by comparing the original histological diagnoses with follow-up data, was found to be approximately 94% in gliomas. As it has been suggested that malignancy of astrocytic gliomas may be considerably underestimated in the small tissue samples obtained by stereotactic biopsy, we have reviewed 160 adult, diffuse supratentorial astrocytic tumours, correlating the original Kernohan tumour grades with survival. In this grading system, although there was generally a good correlation between histological grade and survival probability (P < 0.0001), no distinction could be made between the grade 3 (anaplastic astrocytoma) and grade 4 (glioblastoma) groups. Tumour grades obtained by applying the criteria of the more recent Daumas-Duport grading system were also determined and correlated with survival. These latter tumour grades not only correlated well with survival (P < 0.0001), but also enabled us to identify a group of patients with intermediate grade malignancy (grade 3, anaplastic astrocytoma), surviving longer than those with grade 4 tumours. Image-guided stereotactic biopsy is a useful means of providing tissue samples for histological diagnosis of brain neoplasms, including gliomas. Histological grading of adult, diffuse supratentorial astrocytic gliomas diagnosed by this technique is possible and should be carried out using an appropriate grading system.

Adolescent↗
PubMed1993

Proliferating cell nuclear antigen (PCNA): expression in samples of human astrocytic gliomas.

In this retrospective study, 55 astrocytic tumours were stained with monoclonal antibody PC10 which recognizes the proliferating cell nuclear antigen (PCNA) in formalin fixed, paraffin-wax embedded sections. All the cases were graded using the Daumas-Duport system and the PCNA labelling indices (LIs) were correlated with tumour grades. Mean PCNA LI was 4.1% in the grade II, 8.1% in the grade III and 26.1% in the grade IV group. Six juvenile and cerebellar (grade I) astrocytomas had a mean PCNA LI of 5.6%. In general PCNA LI increased with tumour grade, but there was considerable variation of LIs especially in grade IV tumours which often had very high PCNA LIs (up to 72.7%). PC10 may be a useful complementary technique in surgical neuropathology, but the significance of the high LIs, seen in a proportion of glioblastomas, needs to be further determined.

Adolescent↗
PubMed1993

Infant botulism: a review in South Australia (1980-89).

Between March 1980 and March 1989 there were six identified cases of infant botulism. The presenting symptoms were predominantly poor feeding, lethargy and constipation, and the presenting signs were predominantly hypotonia, weak gag reflex and respiratory difficulty. All required intensive care and prolonged hospital stays. Recovery was eventually complete in all cases. Infant botulism is an uncommon condition but early recognition with adequate intensive care usually results in complete recovery.

Botulism↗
PubMed1993

Intravesical instillation of oxybutynin hydrochloride for detrusor hyper-reflexia.

The effect of intravesical oxybutynin hydrochloride on detrusor behaviour was studied in 15 patients with urinary incontinence due to detrusor hyper-reflexia by ambulatory bladder monitoring. Twelve patients had a reduction in the frequency and amplitude of hyper-reflexic contractions and incontinence episodes following oxybutynin administration. Intravesical oxybutynin may have a role in the management of patients on intermittent self-catheterisation with detrusor hyper-reflexia who cannot tolerate the side effects of anticholinergic agents, including oxybutynin.

Administration, Intravesical↗
PubMed1993

Accuracy in frame-based and frameless stereotaxy.

Stereotactic surgery is currently undergoing great changes with a large number of frameless methodologies being developed alongside traditional frame-based systems. As a result, there is considerable uncertainty over the future clinical roles of the numerous stereotactic options now offered. We have reviewed the current scientific issues regarding accuracy in both frame-based and frameless stereotaxy. Frame-based systems have the advantage of proven clinical utility and instrument carriage with a high degree of mechanical stability and accuracy. Frameless methods are more complex, but also more flexible, and may have wide applications in general neurosurgery if clinical efficacy is confirmed.

Humans↗
PubMed1993

Stereotactic insertion of intracerebral electrodes in the investigation of epilepsy.

Intracerebral electroencephalography is sometimes necessary in the pre-surgical evaluation of patients with drug-resistant epilepsy, in order to define the site(s) of seizure onset. Accurate depth electrode insertion would ideally require multimodal image integration, repetitive and non-invasive localization, assessment of positional accuracy and freedom in target and entry point selection. A method for the acquisition of the multimodal image stereotactic information, necessary for the precise targeting of the mesial temporal structures, and the operative technique used for the accurate placement of the intracerebral electrodes is described. The use of the Gill-Thomas (G-T) stereotactic repeat localizer offers the degree of temporal freedom during the data acquisition period of the electrode implantation procedure which leads to the advantage of an unhurried multi-image integration and targeting in any individual case combined with less discomfort for the patient. The integration of the G-T repeat localizing system with the existing components of the Cosman-Roberts-Wells (CRW-3) stereotactic system offers additional advantages. The target-centered arc-radius design allows complete freedom in the selection of the entry point, offers the possibility of multiple trajectories through the same entry point and permits a choice of either oblique or orthogonal lateral approaches, that are particularly useful for the electroencephalographic sampling of the posterior mesial temporal structures. The satisfactory localizing value of the technique and the additional advantage of easy confirmation of the positional accuracy of the electrodes during the postoperative period, using standard radiographic and magnetic resonance imaging studies, increases the potential of the technique for precise placement of depth electrodes during the pre-surgical evaluation of patients with epilepsy.

Amygdala↗
PubMed1993

Volumetric analysis of epilepsy surgery resections using high resolution magnetic imaging: technical report.

A method is described for accurately measuring the volume and site of epilepsy surgery resections utilizing magnetic resonance imaging. Accuracy has been assessed using post-mortem studies, and both the intra- and interobserver variability is consistently less than 5%. The technique has so far been applied to 25 patients following a variety of operations for medically intractable epilepsy. It provides the crucially accurate baseline required for meaningful follow-up outcome studies of epilepsy surgery. Consequently, it should allow the development of more precise prognostic indices for such operations.

Brain↗
PubMed1993

The role of image-directed biopsy in the diagnosis and management of brainstem lesions.

The appreciation that brainstem tumours do not comprise a homogeneous pathological group and that up to 20% of the preoperative radiological diagnoses of brainstem lesions prove at operation to be wrong, has established the need for a firm histological diagnosis prior to treatment. Current neuro-imaging modalities may have increased the diagnostic accuracy and the detection rate of intrinsic brainstem lesions, but open exploration in cases without an exophytic component is still associated with a low diagnostic yield and considerable morbidity. A series of 72 brainstem lesions approached stereotactically with CT or MRI guidance is presented. A transcortical frontal precoronal trajectory was used in 58 and a suboccipital transcerebellar route in 14. Haematoma was diagnosed preoperatively in 16 cases and therapeutic aspiration was planned. In 56 cases the diagnosis was uncertain, although intrinsic tumour was suspected. A histological diagnosis was established in 52 cases, although in the remaining four cases a tumour was excluded. Unexpected findings occurred in over 15% of the cases. There were no operative deaths and the morbidity was low. In no case was there a permanent neurological deterioration directly related to the procedure, although there was a transient deterioration in two patients and another patient required early re-aspiration of a haematoma.

Adolescent↗
PubMed1993

Stereotactic management of intrinsic brain stem lesions.

Between 1981 and 1991, seventy-two cases of brain stem lesions have undergone CT or MRI-directed stereotactic surgery using the Brown-Roberts-Wells or Cosman-Roberts-Wells stereotactic systems. In 16 cases, the pre-operative diagnosis of haematoma had been made and the procedure was for therapeutic aspiration. In fifty-six cases, the pre-operative diagnosis was uncertain although intrinsic tumour was suspected. Histological diagnosis was obtained in fifty-four of these and unexpected findings of haematomas, granulomas, leucoencephalopathy, demyelinating disease, vasculitis and radiation necrosis occurred in over 15% of the cases. There were no operative deaths and morbidity was low. Advances in neuroradiological imaging with CT and MRI have increased the detection rate of brain stem lesions and image-directed stereotactic biopsy makes it possible in most cases to obtain histological diagnosis with relatively low morbidity which is important for treatment and prognosis. MRI-directed biopsies can compliment CT-guided biopsies in most cases where the lesion is not adequately delineated on the CT image.

Adolescent↗
PubMed1992

Outcome of paediatric bacterial meningitis 1979-1989.

OBJECTIVE: To determine the outcome of all cases of paediatric bacterial meningitis over the 11-year period 1979-1989 and discuss the role of adjunctive therapy with dexamethasone. DESIGN AND SETTING: The study was performed by retrospective case review at Flinders Medical Centre, a general teaching hospital. RESULTS: There were 80 episodes in 79 patients. The age range was 2 days to 15 years (mean, 1.7 years). Haemophilus influenzae type b was the commonest organism (60 of 80 cases; 75%). There were five deaths (6.3%). Sensorineural hearing loss was found in six of 71 children (8.5%) and was bilateral and severe in four (5.6%). Other problems included learning difficulties (12.7%), motor problems (7%), speech delay (7%), hyperactivity (4.2%), blindness (2.8%), obstructive hydrocephalus (2.8%) and recurrent seizures (2.8%). CONCLUSIONS: Bacterial meningitis remains a disease with significant morbidity and mortality. Adjunctive therapy with dexamethasone should be considered, and vaccination against Haemophilus influenzae type b should be routine.

Adolescent↗