NIMAL models of ICH have shown that blood pro- duces ischemia in the parenchyma and that sur- rounding this an area of edema, oligemia, and hem- orrhagic necrosis develops. 3,4,23,32 Hypoperfusion has been demonstrated around human ICH in the acute state with SPECT 9,18,25,31 and PET scanning. 40,41 Whether any of this perilesional hypoperfused tissue survives in the long term is not known. A zone of reversible perilesional oligemia (the penumbra) has been demonstrated in ischemic stroke in humans. 2,10,42 If there is a penumbra around an ICH, it is possible that the neurons in it, as in the penumbra in isch- emic stroke, may be electrically silent but retain membrane integrity, and they may be potentially recoverable if perfu- sion is restored. Indeed, animal experiments have shown that medical, 1,26,32 radiological, 14 or surgical interventions 1,6,23 may reduce the neurological damage after ICH. We studied the changes in CBF that accompany human ICH, with particular reference to the serial changes that oc- cur in the region surrounding the hematoma, by using 99m Tc- HMPAO SPECT scanning (Amersham International plc.). Clinical Material and Methods Patient Population Patients with spontaneous supratentorial ICH were stud- ied using 99m Tc-HMPAO SPECT scanning. This study was approved by the local ethics committee, and informed con- sent (or relatives’ assent) was obtained either from the pa- tients or their relatives if the patients were not well enough to give it. Prospectively collected data from 11 consecutive patients are presented (Table 1); all patients were treated J Neurosurg 96:736–741, 2002 736 Reversible ischemia around intracerebral hemorrhage: a single-photon emission computerized tomography study M. SHAHID SIDDIQUE, F.R.C.S., HELEN M. FERNANDES, M.D., THOMAS D. WOOLDRIDGE, R.G.N., JOHN D. FENWICK, PH.D., PIOTR SLOMKA, PH.D., AND A. DAVID MENDELOW, PH.D. Department of Neurosurgery, University of Newcastle; Regional Medical Physics Department, Newcastle General Hospital, Newcastle-upon-Tyne, United Kingdom; and Department of Diagnostic Radiology and Nuclear Medicine, University of Western Ontario, Toronto, Canada Object. A zone of perilesional ischemia has been demonstrated around intracerebral hemorrhage (ICH) in numerous experimental models and in human studies. There is potential for perfusion recovery in the zone of perilesional oligemia around ICH. The authors sought to demonstrate, quantify, and study the chronological evolution of perilesional isch- emic change in ICH in humans by measuring cerebral blood flow. Methods. Eleven patients with spontaneous supratentorial ICH underwent two technetium-99m hexamethylpropyl- eneamine oxime single-photon emission computerized tomography (SPECT) scanning, one in the acute stage (within days of ictus) and the other in the late stage (6–9 months postictus). All patients in this study were treated nonsurgical- ly. Methods of SPECT data analysis based on count differences in regions of interest can be difficult to apply to images with large space-occupying lesions such as ICH, because of the distortion of intracranial anatomy, midline shift, and al- terations in the three-dimensional (3D) characteristics of the lesion over time (that is, absorption of the hematoma on the later studies). The authors used the following method: the late and early images were registered and aligned to a common 3D orientation and were normalized to maximal counts. The late images were then compared voxel by voxel with the early ones. The region-growing algorithm was used to discern the difference between the two images, outlin- ing voxels in the perihematoma region, with a signal improvement of at least 15% on the late image. Discrete brain regions around the hematoma with at least a 15% improvement in radiotracer uptake (and hence perfu- sion) in the late images were observed in all cases. The mean volume of brain with a greater than 15% improvement in perfusion between the two studies was 34.8 cm 3 (range 7.2–71.3 cm 3 ). These volumes represent regions of the brain that were poorly perfused in the initial studies. This may represent a zone of reversible perilesional oligemia (penumbra) in ICH in humans. Conclusions. This is the first study in which it is documented that some of the perilesional hypoperfused tissue around human ICH regains its perfusion in the long term, leading the authors to suggest that there may be a penumbra in human ICH. Medical or surgical therapeutic interventions could increase the volume of perilesional brain that recov- ers after the initial insult. The results of this study therefore support the concept that intervention in ICH has the poten- tial to reduce the ultimate neurological deficit and improve outcome. KEY WORDS • intracerebral hemorrhage • single-photon emission computerized tomography A J. Neurosurg. / Volume 96 / April, 2002 Abbreviations used in this paper: CBF = cerebral blood flow; CSF = cerebrospinal fluid; ICH = intracerebral hemorrhage; ROI = region of interest; SPECT = single-photon emission computerized tomography; 99m Tc-HMPAO = technetium-99m hexamethylpropyl- eneamine oxime.