Prediction of acute embolic stroke outcome after local intraarterial thrombolysis: value of pretreatment and posttreatment 99mTc-ethyl cysteinate dimer single photon emission computed tomography

Early dynamic SPECT imaging in acute viral encephalitis

BACKGROUND AND PURPOSE

Several cases have reported that dynamic single-photon emission computed tomography (SPECT) shows increased tracer uptake in acute herpes simplex viral encephalitis (HSVE). The purpose of this study was to evaluate the clinical usefulness of dynamic Tc-ECD SPECT in patients with acute viral encephalitis.

METHOD

We performed the dynamic SPECT in 9 patients with acute viral encephalitis (4 women, 5 men, 49.5 +/- 17.4 years of age at onset). SPECT and magnetic resonance imaging (MRI) were performed within 2 weeks after acute clinical onset and at the time of resolution of acute symptoms.

RESULTS

Cranial MRI showed high intensities in all patients (7 medial temporal and 2 lateral temporal lobes, 1 inferior temporal lobe, 2 insula and adjacent regions, 1 thalamus, 1 putamen). The initial dynamic SPECT showed increased accumulation of tracer, corresponding to the lesions on MRI in 3 patients with HSVE. Resolution of acute symptoms was associated with a reduction in increased tracer uptake. Six patients with non-HSVE showed no increased accumulation of tracer.

CONCLUSIONS

Dynamic SPECT may be a new optional neuroradiologic technique that may help to establish a diagnosis in patients with suspected HSVE.

Early Revascularization in a Patient With Perfusion Computed Tomography/Diffusion-Weighted Magnetic Resonance Imaging Mismatch Secondary to Acute Vertebral Artery Occlusion-Case Report-

A 67-year-old woman with a recent history of recurrent ischemic stroke secondary to right vertebral artery stenosis suffered acute onset of left homonymous hemianopsia and the medial longitudinal fasciculus syndrome, which resolved with hyperdynamic therapy. However, consciousness deteriorated 6 hours later. Perfusion computed tomography (CT) revealed regions of prolonged mean transit time in the bilateral cerebellar hemispheres, vermis, brainstem, and right occipital lobe, which were more extensive than the ischemic lesions demonstrated by diffusion-weighted magnetic resonance (MR) imaging. Subsequent cerebral angiography showed occlusion of the right vertebral artery. The patient underwent emergent left superficial temporal artery to left superior cerebellar artery bypass. Postoperatively she demonstrated resolution of the preoperative perfusion CT/diffusion-weighted MR imaging mismatch and improved neurological deficits. Early revascularization in a patient with perfusion CT/diffusion-weighted MR imaging mismatch following acute vertebrobasilar stroke can lead to improvement in cerebral perfusion and neurological function.

Atypical finding of brain Tc-99m-ECD SPECT imaging in herpes simplex encephalitis

Lesions in acute herpes simplex encephalitis (HSE) have been reported to show decreased uptake of Tc-99m ethyl cysteinate dimer (ECD). A patient with acute HSE displaying a lesion in the left temporal lobe was evaluated by means of Tc-99m ECD single-photon emission computed tomography (SPECT). Dynamic SPECT images indicated regionally increased uptake of tracer in the ipsilateral temporal lobe in early phases, followed by slight washout of Tc-99m ECD from the lesion. Static SPECT images revealed increased tracer uptake in the same region. MRI later demonstrated that the HSE lesion involved the whole cortex of the temporal lobe on the affected side. These findings suggest that acute HSE lesions do not always exhibit hypoactivity on static Tc-99m ECD SPECT, and that dynamic Tc-99m ECD SPECT may help physicians diagnose acute HSE.