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D M Hadley

Publications and source records attributed to D M Hadley.

At least 19 recordsLinked to original sources
PubMed1998

Associative encoding of pictures activates the medial temporal lobes.

It remains unresolved whether the medial temporal lobe activations found in recent neuroimaging studies are mediated by novelty detection alone, by specific kinds of encoding or consolidation operations, or both. This study attempted to see whether associative encoding or consolidation is sufficient to cause such activation by matching for novelty across conditions. Using single-photon emission computer tomography (SPECT) (with TC99mHMPAO), we compared the activation patterns produced by the associative encoding and the perceptual matching of novel complex scenes in 10 normal subjects using both statistical parametric mapping (SPM) and a regions-of-interest (ROI) approach. During the encoding condition, significant activations were detected in the left hippocampal/parahippocampal region, the left cingulate cortex, and the right prefrontal cortex, using both statistical techniques. Additionally, activation was found in the right cingulate cortex, and a trend towards activation was found in the right hippocampal/parahippocampal region using the ROI approach. In contrast, no medial temporal activations were found during the matching condition, which produced bilateral occipito-parietal and right posterior inferior parietal (supramarginal gyrus) activations. These results no only confirm that the associative encoding and/or consolidation of complex scenes is partially mediated by medial temporal lobe structures, but also demonstrate, for the first time, that associative encoding/consolidation is sufficient to produce such an activation. The implications of the high degree of consistency revealed by the results of the SPM and ROI comparison are discussed.

Adult↗
PubMed1997

Habituation-like effects cause a significant decrease in response in MRI neuroactivation during visual stimulation.

A wide range of rest/stimulus cycle durations (40-360 sec) is reported to have been used by various groups for MRI neuroactivation studies of the visual cortex. In this paper we demonstrate a clear habituation-like response for longer cycle durations which results in a halving of apparent activation between cycle durations of 138 and 276 sec. This has important implications, not only in terms of optimizing the technique, but also in providing an insight into the underlying physiological mechanisms.

Adult↗
PubMed1997

SPECT, CT, and MRI in head injury: acute abnormalities followed up at six months.

Neuroimaging with single photon emission computed tomography (SPECT) using the cerebral blood flow tracer 99Tc(m)-HMPAO has been used to study acute functional alterations after head injury and residual abnormalities at six month follow up in 32 patients. Comparison has been made with anatomical abnormalities defined acutely with CT and on follow up with MRI. SPECT showed slightly more abnormalities than CT in the acute phase (49 regions of abnormally low tracer uptake on SPECT and 45 lesions on CT). Twenty two of the acute SPECT abnormalities were in normal regions on CT. At follow up MRI showed more abnormalities than SPECT (30 on SPECT and 48 on MRI). Ten of the SPECT deficits were in regions with normal MRI. Comparison of the intensity of late and early SPECT deficits showed that only four early deficits deteriorated whereas 28 improved. Only five of 27 lesions seen on both acute SPECT and CT resolved compared with 16 of 22 lesions seen on SPECT but not on CT. Regions of abnormally high tracer uptake were detected in the acute stage in five of the patients. No high focal uptake was evident on follow up. Ten patients with a residual SPECT abnormality and eight with residual MRI lesions were graded clinically in the upper band of good recovery.

Adolescent↗
PubMed1997

Solid localization marker for MR imaging.

A solid, stable material that can be easily cut into unique, identifiable shapes was compared with other localization markers used in magnetic resonance imaging to determine relaxation characteristics and chemical shift. The solid marker and the conventional oil-based markers caused substantial chemical shift artifacts and so should never be used when high levels of spatial accuracy are necessary, such as in stereotaxy. Although it had the lowest T2 of all the substances tested, the solid marker was useful in identifying structures when different coils, sequences, and fields of view were used.

Artifacts↗
PubMed1997

Homonymous quadrantanopia respecting the horizontal meridian. A feature of striate and extrastriate cortical disease.

It has been proposed that homonymous quadrantanopic visual field loss that respects the horizontal meridian is a pathognomonic sign of extrastriate cortical disease. However, two patients with this sign are reported--one with a rare striate and the other with an extrastriatal lesion of the visual cortex. It is therefore hypothesized that a homonymous quadrantanopia respecting the horizontal meridian may indicate striate and/or extrastriate cortical disease.

Adult↗
PubMed1995

Neuropsychological consequences of two patterns of brain damage shown by MRI in survivors of severe head injury.

Two subgroups of patients were identified from 48 patients with traumatic head injury who had MRI during the acute stage: (a) those with severe diffuse injury--six patients with lesions in both the corpus callosum and the brain stem; (b) those with severe focal injury--16 patients with extensive frontotemporal lesions. Most patients with diffuse injury were in a coma on admission to hospital, whereas most patients with focal injury were out of coma. Duration of post-traumatic amnesia was prolonged in both groups. Patients were followed up at six months after injury, when a battery of neuropsychological tests was given. Patients with both diffuse and focal patterns of injury were impaired by comparison with controls on a range of measures, including tests of memory and attention. The findings contrast with the view that diffuse injury is of much greater importance than focal injury in determining outcome after head injury.

Adolescent↗
PubMed1995

Radiation dose to the lens from computed tomography scanning in a neuroradiology department.

The radiation dose to the lens was measured by thermoluminescent dosimetry on 194 patients undergoing routine head and neck computed tomography scanning in a neuroradiology department. The results are lower than previously reported: brain scans, mean value 5.1 mGy; orbital scans, mean value 18.5 mGy; and direct coronal pituitary scans, mean value 1.9 mGy. These lower values in axial brain scans are due to use of the supraorbital meatal baseline for radiographic positioning.

Brain↗
PubMed1994

Nerve root hypertrophy in chronic inflammatory demyelinating polyneuropathy.

A patient with chronic inflammatory demyelinating polyneuropathy (CIDP) and central demyelinating disease is described in whom striking nodular filling defects on multiple lumbar-sacral nerve roots, mimicking neurofibromata, were observed at myelography and magnetic resonance imaging. We suggest that these lesions are secondary to recurrent segmental demyelination and remyelination and that the differential diagnosis of this radiological feature should include CIDP.

Chronic Disease↗
PubMed1994

Post-traumatic amnesia: still a valuable yardstick.

Records of coma and post-traumatic amnesia (PTA) were collected for a group of 38 patients with closed head injury. The results confirmed earlier studies indicating that patients may have short or negligible coma but report prolonged PTA. Comparison of eight patients with prolonged PTA (> 7 days) and short coma (< 6 hours) with the rest of the group on MRI in the acute stage showed that these patients had significantly more extensive hemispheric damage. In the group as a whole both coma and PTA were related to the number of areas in central brain structures in which lesions were detected, but only PTA was significantly related to the number of hemispheric areas in which lesions were found. It is concluded that although both coma and PTA are related to brain damage they reflect disparate patterns of lesions. Assessment of PTA can thus provide additional information concerning severity of injury.

Adolescent↗
PubMed1993

Ictal/postictal SPECT in the pre-surgical localisation of complex partial seizures.

Single photon emission computed tomography (SPECT) used in conjunction with HM-PAO (Ceretec-Amersham International) was used to image regional cerebral blood flow (rCBF) in 28 patients with medically intractable complex partial seizures during or soon after a seizure, and interictally. Changes from interictal rCBF were seen in 26/28 (93%) patients. The main findings were; 1) During the seizure--hyperperfusion of the whole temporal lobe; 2) Up to 2m postically--hyperperfusion of the hippocampus with hypoperfusion of lateral temporal structures; 3) From 2-15m postically--hypoperfusion of the whole temporal lobe. When compared with EEG and MRI data, correct localisation to one temporal lobe was obtained in 23 patients. In one further patient bilateral temporal foci, and in a further two patients frontal foci, were correctly identified. There were no disagreements between EEG and SPECT localisation. Temporal lobe surgery was successful (by the criterion of at least 90% reduction in seizure frequency) in all but one of the 23 patients operated on. It is concluded that ictal/postictal SPECT is a reliable technique for the presurgical localisation of complex partial seizures. The data indicate a likely sequence of changes in rCBF during and after complex partial seizures of temporal lobe origin.

Adolescent↗
PubMed1993

Spinal cord infarction following meningitis.

A case of delayed onset of paraplegia following minor head injury and meningitis is presented. At operation extensive necrosis of the thoracic spinal cord was demonstrated. The possibility of spinal cord infarction is discussed.

Adult↗
PubMed1992

Indications for and accuracy of magnetic resonance imaging and computed tomography in orbital disease.

All patients referred for orbital imaging to the neuroradiology department of the Institute of Neurological Sciences in Glasgow over a three year period were enrolled in the study and were scheduled to undergo both magnetic resonance imaging and computed tomography. A total of 101 of the 110 referred patients were deemed suitable for analysis. Details of key presenting symptoms, signs, and a pre-imaging diagnosis were recorded prospectively. A final diagnosis was obtained by histology in 65% of cases with an orbital abnormality, by a minimum of one year of clinical review in 19.5%, by response to antibiotic or steroid therapy in 8.5%, or by conclusive investigations such as carotid angiography in in 7% of patients, 29% of the patients had no detectable orbital disease despite a minimum one years' follow-up, and so were regarded as a "normal" group. The images were interpreted prospectively by separate masked observers. The diagnostic accuracies of the two techniques were compared to the final diagnosis. The two imaging methods were shown to be comparable in overall diagnostic accuracy, with a small and statistically non-significant advantage held by magnetic resonance imaging. Interpretation of the two investigations gave more accurate information in different types of disease.

Academies and Institutes↗
PubMed1992

Successful treatment of intracerebral hydatid cysts with albendazole: case report and review of the literature.

Experience with the use of the drug albendazole in the management of cerebral hydatid disease is limited. We report a 33-year-old woman who was harboring multiple cerebral hydatid cysts and who was treated successfully with albendazole. No other treatment was used. The efficacy and the few reversible side effects of the drug are discussed, and the literature is reviewed.

Adult↗
PubMed1991

Gadolinium DTPA enhanced magnetic resonance imaging in acute head injury.

We studied the effect of contrast enhancement on magnetic resonance imaging (Gadolinium DTPA Magnetic Resonance) in 10 patients with a recent head injury. The use of contrast did not increase the number of traumatic lesions identified and we did not detect evidence of altered blood brain barrier permeability in any of the 7 patients, who had a total of 27 lesions, imaged between one and 4 days after injury. Enhancement was found in each of 3 patients imaged 6 or more days after injury. These findings suggest that traumatic cortical and intraparenchymal lesions are not associated with increased cerebrovascular permeability within the first 96 hours of a head injury.

Adult↗