A method of two-dimensional mapping of cortical perfusion by cylindrical transformation of HMPAO SPET data.

In order to synthesize three-dimensional information on relative regional blood flow (rCBF) from the cortical grey matter in 99Tcm-hexamethylpropyleneamine oxime (HMPAO) single photon emission tomographic (SPET) images into a single two-dimensional 'cortical peel' (CP) image, we developed a program that performs cylindrical transformation of SPET data. A sub-routine of this program performs measurements of cortex-to-cerebellum rCBF ratios for 54 cortical regions in the CP image. This program was used to establish a normative database derived from 30 young normal control subjects aged 28.7 +/- 6.9 years. The database was then used to express cortex-to-cerebellum rCBF ratios in four colour-coded ranges of normal standard deviation of the mean rCBF ratio across the cortical regions in the CP image. This CP method was implemented for 30 clinical HMPAO SPET studies in patients (n = 30, aged 71.8 +/- 4.2 years) with suspected dementia as well as several studies in aged healthy subjects (n = 8, aged 67 +/- 9.8 years). In 25/30 (83%) patients, all abnormalities seen on the tomographic display were evident on the corresponding CP image. No aged healthy subjects showed abnormalities on either the tomographic display or the corresponding CP image. An advantage of this technique is that the extent and severity of rCBF abnormalities are readily appreciated in one single image. This technique, in conjunction with the conventional multi-slice tomographic display, was a useful tool in identifying various patterns of rCBF abnormalities in the patients with clinically suspected dementia.

Spontaneous meningocele, a rare middle ear mass.

This report describes the CT and MR findings in one patient with a spontaneous middle ear meningocele and a second patient with a middle ear meningoencephalocele possibly related to a large intracranial mass. High-resolution CT defined anatomic relation and bone destruction, and MR aided in tissue characterization.

Scintigraphic flare in skeletal lymphoma.

The authors describe the bone scan flare phenomenon in a patient with treated skeletal lymphoma. This was confirmed by both gallium scanning and computed tomography. If serial bone scintigraphy is used for assessing the treatment response of lymphoma, the flare phenomenon must be recognized.

Technetium-99m-HMPAO SPECT, CT and MRI in the evaluation of patients with chronic traumatic brain injury: a correlation with neuropsychological performance.

UNLABELLED: The purposes of this study were: (1) to compare 99mTc-hexamethylpropyleneamineoxime (HMPAO) SPECT with CT and MRI in chronic traumatic brain injury (TBI) patients and (2) to correlate both functional and structural neuroimaging measurements of brain damage with neuropsychological (NP) performance. METHODS: Twenty-nine patients (minor TBI, n = 15 and major TBI, n = 14) and 17 normal controls (NC) underwent HMPAO SPECT, CT, MRI and NP testing. Imaging data were analyzed both visually and quantitatively. RESULTS: Nineteen (66%) patients showed 42 abnormalities on SPECT images, whereas 13 (45%) and 10 (34%) patients showed 29 abnormalities on MRI and 24 abnormalities on CT. SPECT detected relatively more abnormalities than CT or MRI in the minor TBI subgroup. The TBI group showed impairment on 11 tests for memory, attention and executive function. Of these, the anterior-posterior ratio (APR) correlated with six tests, whereas the ventricle-to-brain ratio (VBR), a known structural index of a poor NP outcome, correlated with only two tests. CONCLUSION: In evaluating chronic TBI patients, HMPAO SPECT, as a complement to CT or MRI, may play a useful role by demonstrating brain dysfunction in morphologically intact brain regions and providing objective evidence for some of the impaired NP performance.

Technetium-99m-HMPAO SPECT in the evaluation of patients with a remote history of traumatic brain injury: a comparison with x-ray computed tomography.

The functional imaging modality has potential for demonstrating parenchymal abnormalities not detectable by traditional morphological imaging. Fifty-three patients with a remote history of traumatic brain injury (TBI) were studied with SPECT using 99mTc-hexamethylpropyleneamineoxime (HMPAO) and x-ray computed tomography (CT). Overall, 42 patients (80%) showed regional cerebral blood flow (rCBF) deficits by HMPAO SPECT, whereas 29 patients (55%) showed morphological abnormalities by CT. Out of 20 patients with minor head injury, 12 patients (60%) showed rCBF deficits and 5 patients (25%) showed CT abnormalities. Of 33 patients with major head injury, 30 patients (90%) showed rCBF deficits and 24 patients (72%) showed CT abnormalities. Thus, HMPAO SPECT was more sensitive than CT in detecting abnormalities in patients with a history of TBI, particularly in the minor head injury group. In the major head injury group, three patients showed localized cortical atrophy by CT and normal rCBF by HMPAO SPECT. In the evaluation of TBI patients, HMPAO SPECT is a useful technique to demonstrate regional brain dysfunction in the presence of morphological integrity as assessed by CT.

Inhibition of feline spinal cord dorsal horn neurons following electrical stimulation of nucleus paragigantocellularis lateralis. A comparison with nucleus raphe magnus.

The effect of electrical stimulation applied to the nucleus paragigantocellularis lateralis (PGL) was assessed on the somatosensory responses of functionally identified spinal cord dorsal horn neurons in the cat. Neurons were classified as low threshold mechanoreceptive, wide dynamic range or nociceptive specific. The responses of over 95% of all neurons tested were inhibited by a conditioning stimulus to the PGL. For each cell the threshold current intensity necessary to produce inhibition from the PGL (inhibitory threshold) was determined. Analysis of the incidence of inhibition and the inhibitory thresholds showed that the PGL-induced inhibition was not selective for a particular class of neuron. Due to the many similarities between the PGL and the nucleus raphe magnus (NRM), a comparison was made between each region's potency in inhibiting the responses of spinal cord neurons. Based on an analysis of inhibitory thresholds, the PGL was found to be significantly more potent than the NRM. These results indicate the PGL to be an important site from which descending modulation of spinal cord somesthetic information emanates.

Red nucleus modulation of somatosensory responses of cat spinal cord dorsal horn neurons.

Single unit extracellular recordings were obtained from cat lumbar spinal cord dorsal horn neurons activated by cutaneous inputs. The effect of electrical conditioning stimuli applied to the red nucleus (RN) was predominantly that of inhibition although in some cases excitation was seen. All the neurons that projected to the lateral cervical nucleus were inhibited; none of these were excited. These findings suggest that the RN may exert a dynamic modulatory action on the transmission of cutaneous information during the execution of a motor program.

Inhibition of rat spinal cord dorsal horn neurons by non-segmental, noxious cutaneous stimuli.

Extracellular single unit recordings were obtained from spinal cord dorsal horn neurons in halothane-anesthetized rats. Inhibitory effects induced by noxious mechanical or electrical stimuli applied to a remote area of the body surface were assessed on the spontaneous or evoked activity of these cells. Noxious mechanical stimulation inhibited 59% of the cells receiving nociceptive inputs (wide dynamic range and nociceptive specific) but only 5% of the other cell types. Inhibition produced by mechanical stimulation lasted for the full duration of stimulus application (up to 30 s) whereas inhibition produced by electrical stimulation lasted less than 500 ms. Increasing the depth of anesthesia was found to depress or abolish the inhibition.

Descending inhibitory influences from periaqueductal gray, nucleus raphe magnus, and adjacent reticular formation. I. Effects on lumbar spinal cord nociceptive and nonnociceptive neurons.

1. This study examined the inhibitory effects of conditioning stimuli delivered to the periaqueductal gray (PAG), nucleus cuneiformis (CU), nucleus raphe magnus (NRM), nucleus reticularis gigantocellularis (NGC), and nucleus reticularis magnocellularis (NMC) on functionally identified neurons of the lumbar spinal cord dorsal horn in chloralose-anesthetized or decerebrate cats. 2. Neurons were classified according to their responses to a variety of cutaneous stimuli as low-threshold mechanoreceptive (LTM), wide dynamic range (WDR), or nociceptive specific (NS). The major aim of this study was to determine whether there was a difference in the effectiveness of the brain stem stimulation-produced inhibition of nociceptive (noci) neurons (consisting of both WDR and NS neurons) and the LTM non-nociceptive (nonnoci) neurons. There were no statistical differences in the susceptibility of WDR and NS neurons to brain stem-induced inhibition. 3. Most neurons tested could be inhibited by stimulation of any of the brain stem regions tested. In all cases the percentage of noci neurons inhibited from a given region was higher than the percentage of nonnoci neurons; however, this difference was only statistically significant in the case of NMC stimulation. 4. Threshold current intensities necessary to produce inhibition were determined for each neuron from each stimulation site. Although there was a trend for noci neurons to require slightly lower current intensities, there was in fact no statistically significant difference in the inhibitory thresholds between noci and nonnoci neurons for any of the regions tested. 5. A comparison of the mean threshold currents for the five regions studied revealed that the lowest stimulation currents were obtained in NMC with NRM, CU, NGC, and PAG, each requiring progressively higher current intensities in order to produce inhibition. 6. These results indicate that stimulation in PAG and NRM not only inhibits the responses of noci neurons but also those of nonnoci neurons. Moreover, stimulation in reticular regions adjacent to these two regions is effective in inhibiting the responses of both noci and nonnoci neurons.

Descending inhibitory influences from periaqueductal gray, nucleus raphe magnus, and adjacent reticular formation. II. Effects on medullary dorsal horn nociceptive and nonnociceptive neurons.

1. This study examined the inhibitory effects elicited by brain stem stimulation on the somatosensory responses of trigeminal medullary dorsal horn (subnucleus caudalis of the spinal trigeminal nucleus) neurons. Single-unit extracellular recordings were obtained in chloralose-anesthetized cats. Neurons were classified as wide dynamic range (WDR), nociceptive specific (NS), or low-threshold mechanoreceptive (LTM). Conditioning stimuli were delivered to the periaqueductal gray (PAG), nucleus cuneiformis (CU), nucleus raphe magnus (NRM), nucleus reticularis gigantocellularis (NGC), and nucleus reticularis magnocellularis (NMC). 2. Over 97% of the neurons tested could be inhibited by stimulation in all regions except PAG. Stimulation in the PAG inhibited 91% of the neurons tested. There was no statistically significant difference in the incidence of inhibition of WDR and NS nociceptive (noci) neurons and the LTM nonnociceptive (nonnoci) neurons. 3. Mean stimulation intensities necessary to produce inhibition were determined for each neuron from each stimulation site. The current thresholds necessary to inhibit the responses of noci neurons were found to be significantly lower, on the average, than those of nonnoci neurons at stimulation sites in the PAG, CU, and NGC. 4. Inhibition of the responses of WDR neurons required a lower mean current than for NS neurons but was statistically significant only for PAG and NGC. Thresholds for inhibiting the responses of NS neurons were similar to those for inhibiting the responses of LTM neurons for all regions except CU, where LTM thresholds were markedly but not significantly higher. 5. Stimulation thresholds were found to be lowest in NMC, while in NGC, NRM, and CU they were all similar and slightly higher. Stimulation in the PAG required the highest currents to produce inhibition. 6. These results indicate that stimulation in NRM and PAG not only inhibits the responses of noci neurons but also those of nonnoci neurons. Furthermore, stimulation in reticular regions adjacent to NRM and PAG is frequently even more effective in inhibiting the responses of both noci and nonnoci neurons. In addition, WDR neurons are more effectively inhibited than NS or LTM neurons. These results are compared with those obtained using similar methods in cat lumbar dorsal horn.