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(Stroke. 2001;32:2042.)
© 2001 American Heart Association, Inc.

Original Contributions

Parenchymal Hyperdensity on Computed Tomography After Intra-Arterial Reperfusion Therapy for Acute Middle Cerebral Artery Occlusion

Incidence and Clinical Significance

Shinichi Nakano, MD; Tsutomu Iseda, MD; Hirokazu Kawano, MD; Takumi Yoneyama, MD; Tokuro Ikeda, MD Shinichiro Wakisaka, MD

From the Departments of Neurosurgery, Miyazaki Medical College (S.N., T. Iseda, S.W.) and Junwakai Memorial Hospital (H.K., Y.Y., T. Ikeda), Miyazaki, Japan.

Correspondence to Shinichi Nakano, MD, Department of Neurosurgery, Miyazaki Medical College, 5200, Kihara, Kiyotake, Miyazaki 889-1692, Japan. E-mail snakano{at}fc.miyazaki-med.ac.jp

	Abstract

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Background and Purpose—— The purpose of the present study was to assess the incidence and clinical significance of the intraparenchymal hyperdense areas on the posttherapeutic CT scan just after intra-arterial reperfusion therapy.

Methods—— Seventy-seven patients with acute middle cerebral artery occlusion were studied prospectively with post-therapeutic CT. Hyperdense areas were classified into three groups: those in the lentiform nucleus, insular cortex and cerebral cortex. We investigated the incidence of hyperdense areas and hemorrhagic transformations and assessed whether location of hyperdense areas may play a role in the incidence of hemorrhagic transformations. We also evaluated correlation between early CT signs and hyperdense areas.

Results—— Forty-five hyperdense areas were seen in 37 of the 77 patients (48.1%): 19 of the 45 (42.2%) were confirmed to be hematomas themselves, 6 (13.4%) showed later conversion to petechial hemorrhages, and 20 (44.4%) showed rapid disappearance without hemorrhagic transformations. Eleven of the 37 patients (29.7%) had neurological worsening due to massive hematoma (symptomatic hemorrhage), whereas none of the 40 patients without hyperdense areas had symptomatic hemorrhage. The incidence of hemorrhage among hyperdense areas was significantly lower in the insular cortex than in the other 2 regions (P<0.01). On the other hand, hyperdense areas in the lentiform nucleus had a significantly higher incidence of neurological worsening (P<0.05). There was a significant correlation between early CT signs and hyperdense areas (P<0.0001).

Conclusions—— The presence of hyperdense areas was a significant risk factor for severe hemorrhagic transformations, although only 29.7% of patients with hyperdense areas had symptomatic hemorrhage. On the contrary, the absence of hyperdense areas was a reliable negative predictor for symptomatic hemorrhage.

Key Words: cerebral cortex • cerebral ischemia • corpus striatum • middle cerebral artery

	Introduction

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Intraparenchymal hyperdense areas may be commonly seen on posttherapeutic CT scans after intra-arterial reperfusion therapy for acute ischemic stroke.^1,2 These areas are not always hemorrhages; they may be extravasation of contrast medium.^1–3 These hyperdense areas may suggest some degree of microvascular damage and may be a useful finding to predict the occurrence of hemorrhagic complications. Hornig et al⁴ reported that contrast-enhanced CT with intravenous infusion of contrast medium showed extravasation in 86% of patients with hemorrhagic transformations. When contrast medium is administered intravenously before recanalization, it may be unable to reach the ischemic core without collateral blood flow, resulting in the absence of extravasation on postcontrast CT scans. On the other hand, when contrast medium is infused intra-arterially into the ischemic core after therapeutic recanalization, a disrupted blood-brain barrier may be detected with greater sensitivity than with conventional intravenous contrast–enhanced CT scans. Yokogami et al⁵ reported that all patients with posttherapeutic hemorrhagic complications had extravasation on CT scans obtained just after intra-arterial thrombolytic therapy. However, extravasation does not always indicate hemorrhagic transformations or clinical deterioration, and rapid clearance of the contrast medium on posttherapeutic CT has been reported to be a good prognostic sign.^1,2

On the basis of these considerations, we investigated the incidence and clinical significance of the intraparenchymal hyperdense areas on the posttherapeutic CT scans just after intra-arterial reperfusion therapy.

	Subjects and Methods

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Patients
Since 1994, we have treated 108 patients with acute carotid territory stroke. An initial CT scan was obtained just after admission for all patients with a Quantex RX (Yokogawa Medical Systems) with a section thickness of 10 mm. Recent patient selection was performed according to the "early CT signs of <1/3 of the MCA [middle cerebral artery] territory" criterion used in the ECASS (European Cooperative Acute Stroke Study).⁶ The initial pretherapeutic CT reading was performed by 2 or 3 neurosurgeons on duty, and 31 patients were excluded from this study. In total, we enrolled 77 consecutive patients treated with intra-arterial reperfusion therapy for acute MCA occlusion. Site of occlusion and the presence of involvement of the lenticulostriate arteries were confirmed by cerebral angiography with nonionic contrast medium. All patients underwent intra-arterial reperfusion therapy, either thrombolytic therapy or percutaneous transluminal angioplasty (PTA), or both. Before the initiation of reperfusion therapy, a microcatheter was introduced beyond the thrombus and local angiography was performed to assess the size of thrombus or the precise site of occlusion. Therefore, contrast medium may be injected to the ischemic core even without recanalization. As for treatments, we had no prospective protocol. As for CT examinations, however, there was a prospective protocol. Informed consent for CT examinations and treatments was obtained from the patients or their family members.

Definition of Hyperdense Area
To assess the presence of intraparenchymal hyperdense areas, which were defined as newly appeared hyperdensities exhibited on a CT scan just after reperfusion therapy, all patients were moved to the CT room immediately after the completion or discontinuance of reperfusion therapy with the catheter sheath kept in the femoral artery. During reperfusion therapy, repeated angiography was performed using 50 to 100 mL contrast medium for 1 hour or longer. Therefore, posttherapeutic CT was performed without any additional infusion of the contrast medium.

Treatment Procedure
Before 1996, all patients were treated with intra-arterial thrombolytic therapy. Our recent therapeutic protocol since 1996 has been reported previously.^7,8 In brief, when early CT signs were present and/or lenticulostriate arteries were involved in ischemia, we preferred direct PTA to thrombolytic therapy as the first choice of the treatment. For patients with MCA trunk occlusion with neither lenticulostriate artery involvement nor early CT signs, intra-arterial thrombolytic therapy was selected. For patients with M2 occlusion, intravenous infusion of native tissue plasminogen activator (tPA [tisokinase]) was selected in case without early CT signs and intra-arterial thrombolysis was performed only when early CT signs were present.

Direct PTA was performed with a Stealth angioplasty balloon catheter with a maximum diameter of 2.0 to 2.5 mm. The balloon catheter was advanced into the occlusion site and inflated to 2 atm initially and subsequently up to 3 atm. Several inflations of 30 seconds each were performed until recanalization of the MCA trunk was established. After each inflation, repeated angiography was obtained to assess the degree of recanalization and the presence or absence of distal embolic occlusions.

Doses of urokinase ranged from 60 000 to 600 000 U, with 10 mL saline/60 000 U, in boluses. Doses of native tPA ranged from 3.6 to 14.4 mg, with 10 mL saline/1.8 mg tPA, in boluses. Just before the initiation of reperfusion therapy, 5000 U heparin was administered intravenously. An additional 1000 U intravenous heparin was administered at 1-hour intervals during the procedure of the reperfusion therapy. For incomplete recanalization or residual severe stenosis without intraparenchymal hyperdense areas on posttherapeutic CT only, an intravenous continuous infusion of 10 000 to 15 000 U heparin/d was administered for 7 days. When complete recanalization was achieved or intraparenchymal hyperdense areas were seen, we performed strict blood pressure to <160/90 mm Hg with neither anticoagulation nor antiplatelet treatment after reperfusion therapy. The degree of recanalization was classified into 3 grades: complete, partial, and no recanalization.

Follow-Up Evaluation
To investigate the acute effect of hyperdense areas or hemorrhagic transformations, the neurological status was evaluated just before and 1 week after treatment according to the National Institute of Health Stroke Scale (NIHSS). Major neurological improvement or worsening was defined as a decrease or an increase in the stroke score by 4 points, respectively. The clinical course during the first week after onset was divided into 3 types: (1) improved, (2) no change, or (3) worsened.

Follow-up CT scans were obtained on the next day (24 hours later) and again 3 to 7 days after the termination of the reperfusion therapy. All patients who were still alive were examined with 4 CT scans (baseline, posttreatment, day 1, and days 3 to 7). Follow-up CT scans were evaluated by 2 or 3 neurosurgeons in charge of the reperfusion therapy. Intraparenchymal hyperdense areas were defined as hemorrhages when they did not resolve until >24 hours later. Hemorrhagic transformations were subdivided into 3 types: (1) petechial hemorrhage with spotty and scattered hyperdense areas, (2) small hematoma with a homogeneous hyperdense area <3 cm in diameter, and (3) massive hematoma with neurological worsening (symptomatic hemorrhage). When hyperdense areas disappeared by the next day, they were considered to be extravasation of the contrast medium. According to the location of hyperdense areas, they were classified into 3 groups: in the lentiform nucleus, in the insular cortex, and in the cerebral cortex.

We prospectively investigated the incidence of hyperdense areas, hemorrhagic transformations, and associated complications and assessed whether location of hyperdense areas may play a role in the incidence of hemorrhagic transformations and associated complications. Furthermore, we evaluated correlation between pretherapeutic early CT signs and posttherapeutic hyperdense areas. Intraparenchymal early CT signs were defined according to the following characteristics: obscuration of the margin of the lentiform nucleus, loss of the insular ribbon, and cortical effacement.^5,9,10 Initial CT images were retrospectively analyzed by 3 neurosurgeons (S.N., T. Iseda, and T.Y.) together. They knew only the side of hemiparesis, and CT images were read in an unblinded fashion. The purpose of the present study was not to evaluate the detection rate of early CT signs by blinded reading but rather to investigate the correlation of pretherapeutic early CT signs and posttherapeutic intraparenchymal hyperdense areas. To minimize false-negative or false-positive interpretations, the presence of early CT signs was considered when all 3 neurosurgeons were in accord after discussion.¹¹

Statistical Analysis
Statistical analyses were performed using univariate tests (Mann-Whitney U and Kruskal-Wallis tests) and a logistic regression analysis. We chose a value of P=0.05 as a level of statistical significance. ORs and 95% CIs were used to evaluate the association of hyperdense areas with the risk of hemorrhagic transformations and to evaluate whether the site of hyperdense areas was associated with the incidence of hemorrhagic transformations.

	Results

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Among 77 patients, 37 (48.1%) had intraparenchymal hyperdense areas, whereas the other 40 patients (51.9%) had no hyperdense areas. Seventy-three patients had a defined time of onset, and average intervals from onset to the termination of the treatment were 3.79±1.34 and 3.92±1.76 hours in patients with and without hyperdense areas, respectively. The baseline characteristics of the 2 groups are shown in Table 1. There were no significant differences in age, sex, angiographic occlusive site, pretherapeutic NIHSS, degree of recanalization, methods of reperfusion therapy, doses of thrombolytic agents, and duration of ischemia between these 2 groups. On the other hand, there were significant differences in the incidence of early CT signs (P<0.0001), the clinical outcome at 1 week (P<0.01), and the incidence of symptomatic hemorrhage between these 2 groups (P<0.001, Mann-Whitney U test). In view of the prediction of symptomatic hemorrhage, the predictive values of hyperdense areas were as follows: sensitivity 11 of 11 (100%, 95% CI 74% to 100%), specificity 40 of 66 (61%, 95% CI 49% to 72%), positive predictive value 11 of 37 (30%, 95% CI 17% to 46%), negative predictive value 40 of 40 (100%, 95% CI 91% to 100%), and overall accuracy 51 of 77 (66%, 95% CI 55% to 76%).

View this table: [in this window] [in a new window]   Table 1. Baseline Characteristics of the 2 Groups With and Without Hyperdense Areas

Hyperdense Areas and Hemorrhagic Transformations
The correlation between hyperdense areas and hemorrhagic transformations is shown in Table 2. The rates of total hemorrhagic transformations and symptomatic hemorrhage were 41.6% (32 of 77) and 14.3% (11 of 77), respectively. Among the 37 patients with hyperdense areas, 19 were considered to have hemorrhagic components on the next day. In 11 of them, the hyperdense areas developed into massive hematoma, and 7 of them died within 1 week. In the other 8 patients, hyperdense areas remained the same size without clearance and were considered to be small hematomas; none of the patients had neurological change. In the remaining 18 patients, hyperdense areas disappeared by the next day and were considered to be extravasation of the contrast medium. All of these patients showed neurological improvement. In 6 of them, follow-up CT disclosed petechial hemorrhage a few days later. However, in 7 (17.5%) of the 40 patients without any hyperdense areas, follow-up CT disclosed petechial hemorrhage without neurological change. These 40 patients had neither small nor massive hematomas. Twenty-seven patients showed neurological improvement, and the other 13 had no neurological change. There was a significant difference in the incidence of hemorrhagic transformations between these 2 groups with and without hyperdense areas (Table 2, P<0.0001, Mann-Whitney U test). Compared with patients without hyperdense areas, patients with hyperdense areas had an increased risk of hemorrhagic transformations (OR 9.82, 95% CI, 3.38 to 28.56).

View this table: [in this window] [in a new window]   Table 2. Correlation Between Hyperdense Areas and Hemorrhagic Transformation

Location of Hyperdense Areas
There were 45 hyperdense areas in the 37 patients, including 16 areas in the lentiform nucleus, 10 in the insular cortex, and 19 in the cerebral cortex. The incidence of hemorrhage among hyperdense areas in each location is shown in Table 3. Among these 45 areas, 19 (42.2%) were confirmed to be hematomas themselves on the next day, 6 (13.4%) showed later conversion to petechial hemorrhages after rapid clearance of the contrast medium and the remaining 20 (44.4%) showed rapid disappearance without hemorrhagic transformations. The incidence of total hemorrhagic transformation was significantly higher in the cerebral cortex (OR, 25.20, 95% CI, 2.51 to 252.55) and lentiform nucleus (OR, 15.00, 95% CI, 1.50 to 149.73) compared with the insular cortex (P<0.01, Kruskal-Wallis test). Nine of 16 hyperdense areas (56.3%) in the lentiform nucleus were hematomas, 7 of them developed into massive hematoma (Figure 1). Only one of them changed into petechial hemorrhage after rapid clearance of the contrast medium. Nine of 19 hyperdense areas (47.4%) in the cerebral cortex were hematomas themselves, many of them remained small hematoma (Figure 2). Five of the 19 hyperdense areas changed into petechial hemorrhage after rapid clearance of the contrast medium, and only 4 developed into massive hematoma. On the other hand, only 1 of 10 hyperdense areas (10.0%) in the insular cortex was a small hematoma, and there was no massive hematoma in this region. Most of the hyperdense areas (90.0%) in the insular cortex disappeared by the next day without hemorrhagic transformations (Figure 3). Although there was no significant difference in the incidence of small hematoma and petechial hemorrhage among hyperdense areas in the 3 locations, the incidence of massive hematoma was significantly higher in the lentiform nucleus than in the other 2 regions (Table 3, P<0.05, Kruskal-Wallis test).

View this table: [in this window] [in a new window]   Table 3. Incidence of Hemorrhage Among Hyperdense Areas in Each Location

View larger version (129K): [in this window] [in a new window]   Figure 1. Representative posttherapeutic CT findings in the lentiform nucleus in a 78-year-old man. A, Postcontrast CT scan just after reperfusion therapy showing a hyperdense area in the posterior portion of the left lentiform nucleus. B, Follow-up CT scan obtained 4.5 hours after the completion of reperfusion therapy. The hyperdense area developed into massive hematoma.

View larger version (123K): [in this window] [in a new window]   Figure 2. Representative posttherapeutic CT findings in the cerebral cortex in a 73-year-old woman. A, Postcontrast CT scan just after reperfusion therapy showing a hyperdense area in the right temporal lobe associated with intraventricular hemorrhage. B, Follow-up CT scan obtained 23 hours after the completion of reperfusion therapy. The hyperdense area remained almost the same size, suggesting that it was a small hematoma mixed with contrast medium.

View larger version (119K): [in this window] [in a new window]   Figure 3. Representative posttherapeutic CT findings in the insular cortex in a 58-year-old woman. A, Postcontrast CT scan just after reperfusion therapy showed a hyperdense area in the insular cortex. B, Follow-up CT scan obtained 24 hours after the completion of reperfusion therapy. The hyperdense area had disappeared, suggesting that it represented contrast medium alone.

	Discussion

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Hyperdense Areas and Symptomatic Hemorrhage
Symptomatic hemorrhage, which is a mixed clinical/CT definition¹² defined as massive hematomas with neurological worsening in our study, is the greatest problem during the performance of reperfusion therapy. In our study, the rates of total hemorrhagic transformation and symptomatic hemorrhage (41.6% and 14.3%) were within the range of those in the recent controlled clinical trials of thrombolytic therapy for acute ischemic stroke.^13–19 Although more than half of the hyperdense areas (55.6%) were associated with some degree of hemorrhages, only 29.7% of patients with hyperdense areas had symptomatic hemorrhage. On the other hand, 44.4% of hyperdense areas disappeared by the next day without any delayed appearance of hemorrhagic transformations. Such hyperdense areas with rapid clearance may be composed of contrast medium alone without hemorrhage. Wildenhain et al¹ reported that the rapid disappearance of hyperdense areas might be a good prognostic sign. Our study has also demonstrated that the rapid disappearance of hyperdense areas on early posttherapeutic CT was never associated with symptomatic hemorrhage. Hyperdense areas are the result of varying degrees of injury to microvascular permeability and integrity. When the ischemic injury is limited to the endothelial cell permeability barrier, hyperdense areas may be composed of contrast medium alone without hemorrhage. On the other hand, when the ischemic injury extends to the degradation of the basal lamina, a structural barrier, hyperdense areas may be associated with some degree of hemorrhage.²⁰ Because symptomatic hemorrhage is the result of severe microvascular damage extended to the basal lamina, the absence of intraparenchymal hyperdense areas suggestive of normal permeability and structural barriers may be a reliable negative predictor for symptomatic hemorrhage. In the present study, we demonstrated that there was neither small nor massive hematomas in patients without hyperdense areas. When hyperdense areas were not seen on posttherapeutic CT just after intra-arterial reperfusion therapy, there may be little or no possibility of symptomatic hemorrhage.

Hyperdense Areas and Early CT Signs
In the present study, there were no significant differences in age, sex, angiographic occlusive site, pretherapeutic NIHSS, degree of recanalization, methods of reperfusion therapy, doses of thrombolytic agents, and duration of ischemia between the 2 groups with and without hyperdense areas. The only pretherapeutic predictive factor for the appearance of hyperdense areas was the presence of early CT signs, although 31.8% of patients with early CT signs had no hyperdense areas. Early CT signs have been reported to be useful in the prediction of hemorrhagic transformations.^5,21–26 Of course, the accurate diagnostic value of early CT signs should be evaluated in a blinded fashion. In daily clinical practice, however, it is a matter of course that CT images are evaluated by plural physicians at the same time who are aware of clinical signs and symptoms. Furthermore, the purpose of the present study was not to evaluate the detection rate of early CT signs by blinded readers but rather to investigate the correlation of pretherapeutic early CT signs and posttherapeutic hyperdense areas. Therefore, although our data were unblinded reading results, they may provide important information. There was a significant correlation between pretherapeutic early CT signs and posttherapeutic hyperdense areas (P<0.0001, Mann-Whitney U test).

Location of Hyperdense Areas
Hyperdense areas in the lentiform nucleus often developed into massive hematoma, probably because of the vulnerability of the lenticulostriate arteries to ischemia, whereas most of those in the insular cortex made a rapid disappearance without hemorrhagic transformations. Although hyperdense areas in the cerebral cortex had the highest incidence of hemorrhages, most of them were small hematoma or petechial hemorrhage instead of massive hematoma. It is likely that petechial hemorrhage may be apt to be detected in the cerebral cortex after clearance of the contrast medium because of its large area. On the contrary, petechial hemorrhage in the insular cortex may be difficult to be detected by CT because of its small area.

Because blood-brain barrier damage is usually pronounced following the restoration of blood flow after ischemia,²⁷ delayed appearance of hemorrhagic transformations may be seen even in patients without hyperdense areas on the posttherapeutic CT scan just after reperfusion therapy. Our study also demonstrated that follow-up CT disclosed petechial hemorrhage in 17.5% of patients without any hyperdense areas on the posttherapeutic CT scan just after reperfusion therapy. However, none of these patients had symptomatic hemorrhage.

In conclusion, hyperdense areas were seen in 48.1% of patients. More than half of the areas (55.6%) were associated with some type of hemorrhages; 29.7% of patients had symptomatic hemorrhage, and 44.4% of the areas disappeared rapidly without hemorrhagic transformations. The absence of hyperdense areas was a reliable negative predictor for symptomatic hemorrhage. Because most of the symptomatic hemorrhages occurred in the lentiform nucleus, patients with hyperdense areas in that location should receive all possible care, including strict blood pressure control and no antiplatelet and anticoagulation treatments.

Received December 13, 2000; revision received May 8, 2001; accepted June 8, 2001.

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