J. Vandevivere

Technetium-99m hexamethylpropylene amine oxime single photon emission tomography in febrile convulsions.

We report our initial experience with technetium-99m hexamethyl propylene amine oxime (99mTC-HMPAO) brain single photon emission tomography (SPET) in the investigation of 19 children presenting with febrile convulsions. Two patients with complex febrile convulsions showed focal SPET lesions contralateral to the neurological deficit. However, in 9 out of 17 patients with simple febrile convulsions, focally disturbed perfusion was shown. In 4 out of 6 patients with electroencephalogram (EEG) abnormalities on admittance, SPET revealed at least 2 focal lesions. The temporofrontal region was the one most commonly involved. The SPET findings presented here also suggest a temporal relationship with the febrile convulsions, with markedly fewer lesions if examined after 12 days. In our initial experience, perfusion SPET did not show any particular pattern helpful in the differential diagnosis of the child presenting with febrile convulsions. Physiopathologically, our findings may support the hypothesis that brain tissue is regionally more vulnerable to fever, in patients presenting with febrile convulsions.

Technetium-99m HMPAO SPET in acute supratentorial ischaemic infarction, expressing deficits as millilitre of zero perfusion.

A comparative interim analysis was performed of clinical parameters, computed tomographic (CT) scan results and technetium-99m hexamethylpropylene amine oxime single-photon emission tomography (SPET) findings obtained within 12 h of acute supratentorial ischaemic infarction. First, the applicability for SPET semiquantification in this study of the “method of Mountz”, simultaneously accounting for extent and degrees of hypoperfusion by expressing deficits as millilitre of zero perfusion, was considered. Next, the relative contributions of perfusion SPET and CT scan in the acute stage of ischaemic infarction were compared in 27 patients (mean age 68.8 years). Finally, the correlation of SPET lesions with clinical parameters at onset was evaluated. The method of Mountz represents a workable, accurate virtual parameter, with the assumption that the contralateral brain region remains uninvolved. Interobserver reproducibility in 12 SPET studies, with lesions varying between 6 and 369 cc, showed a correlation coefficentr of 0.99. In practice, because of inconstant distribution of activities in the brain, the method can only be applied slice by slice and not on the total global volume. While the mean delay since the onset of symptomatology was approximately 7 h for both SPET and CT scan, SPET showed lesions concordant with the clinical neurological findings in 100% and CT scan in only 48%. One could hypothesize that SPET examinations performed later would show larger functional defects, because of the development of additional functional changes secondary to biochemical alterations. However, in this regard no statistically significant differences were found between two subproups, taking the median of delay before SPET examination as cut-off. Finally, when comparing the volumes of SPET lesions during the acute stage with clinical parameters, a statistically significant correlation (P<0.01) was found with the Orgogozo Scale scores describing the neurological deficit, but not with the Glasgow Coma Scale or Frenchay Aphasia Screening Test scores obtained on admittance.

Single photon emission computed tomography using perfusion tracers in seizure disorders

Single photon emission computed tomography (SPECT) using perfusion tracers makes it possible to estimate regional cerebral blood flow (rCBF) and, indirectly, local brain metabolism. It may be possible to detect and follow physiopathological alterations, such as may be seen in seizure disorders. The authors review the principles of and some data on perfusion SPECT in seizure disorders, stress advantages as well as major drawbacks and add their initial experience with Tc-99m hexamethylpropyleneamine oxime (HMPAO) SPECT in febrile convulsions.

High spatial resolution Tc-99m HMPAO brain SPECT in cerebellar embolic infarction

Oblique Tc-99m HMPAO brain SPECT images of a 54-year-old man with brainstem and cerebellar infarcts are presented. Features of particular interest include the high spatial resolution, the embolic nature and the wedge-shaped appearance of the cerebellar infarct, and the presence of reversed cerebral diaschisis without neuropsychologic impairment