A case of thalamic hemorrhage-induced diaschisis

Diaschisis refers to a disturbance （inhibition or facilitation） of function in an area remote from the site of a primary brain lesion. Previous studies have confirmed that regional cerebral blood flow and metabolism are noticeably decreased in an infarct region. Transient excessive perfusion appears in the ischemic penumbra, and diaschisis occurs in an area remote from the lesion site, showing decreased regional cerebral blood flow and metabolism. Mirror diaschisis refers to a decrease in oxygen metabolism and blood flow in the ＂mirror image area＂ to the infarct regions in the contralateral hemisphere. In this study, a patient with right thalamic hemorrhage was affected with right arm and leg numbness. At 4 months before onset, magnetic resonance imaging of the head demonstrated lacunar infarcts in the left thalamus; therefore the right arm and leg numbness was not associated with lacunar infarcts in the left thalamus. At 8 days following onset, magnetic resonance imaging reexamination did not reveal the focus that could induce right arm and leg numbness and weakness. Thus, it is suggested in this study that the onset of this disease can be explained by mirror diaschisis. That is, right thalamic hemorrhage leads to decreased blood flow and metabolic disturbance in the contralateral thalamus, resulting in right arm and leg numbness.

Apparent diffusion coefficient evaluation for secondary changes in the cerebellum of rats after middle cerebral artery occlusion

Supratentorial cerebral infarction can cause functional inhibition of remote regions such as the cerebellum, which may be relevant to diaschisis. This phenomenon is often analyzed using positron emission tomography and single photon emission CT. However, these methods are expensive and radioactive. Thus, the present study quantified the changes of infarction core and remote regions after unilateral middle cerebral artery occlusion using apparent diffusion coefficient values. Diffu- sion-weighted imaging showed that the area of infarction core gradually increased to involve the cerebral cortex with increasing infarction time. Diffusion weighted imaging signals were initially in- creased and then stabilized by 24 hours. With increasing infarction time, the apparent diffusion co- efficient value in the infarction core and remote bilateral cerebellum both gradually decreased, and then slightly increased 3-24 hours after infarction. Apparent diffusion coefficient values at remote regions （cerebellum） varied along with the change of supratentorial infarction core, suggesting that the phenomenon of diaschisis existed at the remote regions. Thus, apparent diffusion coefficient values and diffusion weighted imaging can be used to detect early diaschisis.

Reversible posterior leukoencephalopathy syndrome: single photon emission computerized tomography observations

The authors report clinical correlations of single photon emission computerized tomography (SPECT) findings in reversible posterior leukoencephalopathy (RPL). These are observations that have not received wide attention in literature. A 31-year-old hypertensive gentleman, on discontinuing antihypertensive medications, presented with vomiting, headache, focal motor to bilateral tonic-clonic seizures, altered sensorium, right gaze palsy and right hemiparesis. Accelerated hypertension was noted and he improved well with antihypertensive and anticonvulsant therapy. While cranial magnetic resonance imaging (MRI) revealed extensive bilateral lesions, SPECT imaging revealed perfusion defects involving bilateral basal ganglia, left parieto-occipital, right cerebellar and right occipital regions, which corresponded with clinical deficits on examination. While MRI is the standard of care for the evaluation of RPL, this case suggests that SPECT abnormalities may be better localized to the pathogenic lesions. Furthermore, this may begin to explain the pathophysiology of injury in RPL.