EXPERIMENTAL
107,178-186
NEUROLOGY
(1990)
Corrugation of Cerebral Vessels following Subarachnoid Hemorrhage: Comparison of Two Experimental Models of Chronic Cerebral Vasospasm E. RICKELS,* *Neurosurgical
Clinic
V. SEIFERT,* M. ZUMKELLER,*
and TDepartment
of Electron
Microscopy
and Cell Biology,
The occurrence of delayed ischemic deficits due to the development of chronic cerebral vasospasm following subarachnoid hemorrhage is thought to be responsible for about 15% of the mortality and permanent morbidity of patients with ruptured intracranial aneurysms (1, 7, 16-18). Despite extensive laboratory and clinical investigations the pathogenesis of cerebral vasospasm could not be elucidated. However necropsy studies as well as experimental studies of cerebral vessels in spasm have shown that the vessel wall undergoes severe ultrastructural changes which are thought to form the morphological basis of delayed cerebral spasm (2, 4-6, 10, 19). On the basis of two different models of cerebral vasospasm we present a comparison of the morphological changes of the basilar artery in the dog and of peripheral cerebral vessels in the rat after experimental subarachnoid hemorrhage. AND
METHODS
Dog Model The experiments were performed with 20 mongrel dogs of both sexes weighting between 20 and 25 kg according to the “two hemorrhage model” of chronic vasospasm (20). After induction of anesthesia and endotracheal intubation the dogs were put on controlled ventilation. Using the femoral artery route an angiographic catheter was advanced to the vertebral artery. Angiography of the basilar artery was performed with 5 ml of Iopromit. Following angiography subarachnoid hemorrhage was simulated by injection of 4 ml of autologous blood into the cisterna magna (Fig. 1). Following injection the head of the dog was lowered for 30 min to allow distribution of the blood within the subarachnoid space. A second volume of blood was injected on Day 3 of the experiment. On Day 8 a control angiogram of the basilar artery was performed to angiographically demonstrate the presence and severity of the vessel narrowing (Fig. 2). Following intravital perfusion-fixation of the cerebral vessels with cacodylate-buffered glutaraldehyde, the 0014-4666/90 $3.00 Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
Medical
E. REALEt School,
Hannover,
West Germany
brain of the dog was removed and the basilar artery was dissected with the aid of a surgical microscope. Angiographical changes in the diameter of the basilar artery on Day 8 versus Day 1 were examined with a Zeiss stereo microscope and a lo-fold magnification. After measuring the diameter of the basilar artery at seven corresponding locations along the course of the vessel, the accumulated values were averaged and the mean reduction of the vessel diameter was calculated. Morphological changes in the arterial wall were demonstrated using light microscopic, scanning electron, and transmission electron microscopic examinations.
INTRODUCTION
MATERIAL
U. KUNZ,*AND
Rat Model A total number of 30 male Wistar rats weighting between 200 and 300 g were anesthesized with an intraperitoneal injection of 0.15 ml Rompun and 0.1 ml Ketanest per 100 mg body wt. Following microsurgical dissection of the atlantooccipital membrane the cisterna magna was punctured and 0.1 ml of CSF was withdrawn. After withdrawal of blood from the retrobulbar venous plexus, CSF and blood were mixed to prevent premature clotting and 0.1 ml of the mixture was injected into the cisterna magna. The procedure described above was repeated after 24 h. When the animals developed clinical signs of vasospasm with drowsiness and rigidity of the neck they were anesthesized again on Day 8. The thorax was opened and following exposure of the heart a canula was inserted into the ascending aorta and secured with ligation. The descending aorta was clamped and the right atrium was cut. Blood from the cerebral circulation was washed out with perfusion of Ringer’s solution at body temperature. Thereafter the vascular cerebral system was fixated by perfusion with Karnovsky’s solution containing 2.5% glutaraldehyde and 2.5% formaldehyde buffered in 0.04% sodium cacodylate. After fixation, Mercox resin prepared according to the manufacturer’s instruction was injected into the cerebral circulation. Following decapitation of the animal and removal of the soft tissue of the head, the skull was placed in 10% KOH solution containing 3% of detergent. The acquired clean cast was mounted and sputtered in an ion-coater (POALARON
178
CHRONIC
CEREBRAL
179
VASOSPASM
in the outer adventitia layer loose accumulation of inflammatory cells can be observed. In the transmission electron microscopic examination pathological changes can be demonstrated, especially at the endothelial vessel surface. The homogeneous layer of endothelial cells closely interconnected and with direct contact with the lamina elastica which can be observed in normal vessels has undergone severe ultrastructural changes with corrugation and desquamation of the endothelial cells which are lifted away from the underlying lamina. Additional vacuolation between the endothelial and muscularis layer can be demonstrated as well as ingrowth of fibrous tissue (Figs. 5 and 6). In the scanning electron microscopic examination the normal appearance of the endothelial layer with welldemarcated cell borders and homogeneous covering of the vessel lumen is replaced by an irregular-shaped appearance with partly extreme folding and corrugation of the endothelium. Due to the fact that the endothelial cells have become partly separated, the regular appear-
FIG.
1.
Angiogram
of the basal
artery
of the dog before
SAH.
E 5400) and examined using a Cambridge Stereo Scan 600 scanning electron microscope. In a control group (10 animals) the whole preparation of the corrosion cast was done in the described way without previous injection of blood in the cisterna magna. RESULTS
Dog Model Following experimental subarachnoid hemorrhage all animals developed severe angiographic vasospasm with a mean reduction of the basilar artery diameter on Day 8 as compared to that on Day 1 of more than 50% (Figs. 1 and 2). When the light microscopic appearance of the spastic basilar artery is compared to the normal appearance of the vessel, considerable narrowing of the vessel lumen as well as folding and corrugation of the intima and lamina elastica is demonstrable (Figs. 3 and 4). The muscularis layer does not show any severe ultrastructural changes in the light microscopic picture, whereas
FIG.
2.
Angiogram
of the same basilar
artery
8 days after
SAH.
FIG.
FIG lamina
. 4.
Light elastica.
microscopy
3.
Light
microscopy
(magnification,
160X).
(magnification,
Basilar
artery
130X).
Normal
of dog: reduction
180
basilar
artery
of lumen
of dog without
and folding
SAH.
and corrugation
of the intima
and
CHRONIC
FIG.
FIG.
6.
Transmission
5.
electron
Transmission
microscopy
electron
CEREBRAL
microscopy
(magnification,
(magnification,
3250X).
Basilar
181
VASOSPASM
4300X).
artery
Normal
of dog after
basilar
SAH:
artery
desquamation
of dog.
of the endothelial
cells.
FIG. surface.
7.
Scanning
electron
microscopy
(magnification,
134X).
Normal
FIG. thicken
8. Scanning electron microscopy ing of the vessel wall (arrows).
(magnification,
200X).
Basilar 182
basilar
artery
artery
of dog without
of dog with
vasospasm;
SAH:
smooth
severe
folding
fokling
of the il nner
of the inner
SUI
FIG.
9.
Scanning
electron
FIG. 10. Scanning electron cell scores are closer together.
microscopy
microscopy
(magnification,
(magnification,
470X).
630X).
Normal
Cerebral 183
cerebral
artery
artery
of rat: paralleled
of dog with
vasospasm:
cell cores slight
intensive
foldings.
of the inner
surface,
the
FIG.
FIG.
11.
12.
Very
Normal
small
cast of a very
vasospastic
artery
small
artery
of a rat’s brain
in the periphery 184
(magnification,
of the rat’s brain
1300X).
(magnification,
1700X)
CHRONIC
CEREBRAL
ante of the endothelial cell borders can no longer be demonstrated (Figs. 6-8). Rat Model Clinical signs of cerebral vasospasm were present in all of the experimental animals. The scanning electron microscope appearance of the control group demonstrates the well-known differentiation between arteries and veins as described by Miodonsky et al. (11). These consist of arteries having cell-nucleus depressions of ovoid shape which are paralleled by the outer border (Fig. 9). Veins show round depressions. The cell-nucleus depressions are surrounded by borderlines of irregular shape (11,9). In general the vessels of the control group demonstrate a smooth luminal surface with slight longitudinal folds. In the animals which had suffered from a SAH the luminal surface of the cast had distinct longitudinal folds with irregularities over wide parts of the vessels (Fig. 10). There was no stretching of vessels for fixation in our experiments. With regard to the corrosion cast it should be stated that the vessels were fixated while still in their anatomical location in the skull. Changes in the luminal diameter are therefore only possible by intimal folding, which will cause the smaller slit-like appearance of the cell nuclei. These folds could even be found in very small vessels in the cerebral periphery and remote from the experimental bleeding (Figs. 11 and 12). Additionally the nuclei impressions were pressed together so that it was impossible to differentiate the normal cell borders. DISCUSSION
In 1979, Kassell et al. summarizing the experimental and clinical data of different research groups as well as the results of their own investigations proposed the term “proliferative vasculopathy” for the morphological changes of the cerebral vessel wall during hemorrhageinduced vasospasm, due to their observation of proliferative fibrous tissue interposed between endothelium and lamina elastica (8). The assumption of severe ultrastructural changes of the arterial wall as the morphological basis of the angiographic narrowing seen after hemorrhage-induced spasm has been confirmed by recent experimental studies (5,10,15,19). The aim of our investigation was not only to demonstrate morphological changes of the cerebral vessels following SAH but also to compare the ultrastructural features of delayed vasospasm in larger vessels like the basilar artery and in small peripheral vessels of the rat, demonstrating that cerebral spasm not only affects the vasculature at the cranial base as demonstrated by angiography but also is propagated into the cerebral periphery. The general morphological picture of this chronic form of cerebral spasm can best be demonstrated experi-
185
VASOSPASM
mentally when investigating the basilar artery of the dog. These ultrastructural changes consist of severe folding of the endothelium with corrugation and denudation of the lamina elastica. The endothelium is often lifted away from the thickened intimal layer. Additional severe changes consist of intimal cellular proliferation with rupture and splitting of the internal elastic membrane. Necrosis of the muscular layer (myonecrosis) has been described but could not be observed in our experimental study. These changes at the endothelial and lamina elastica level are routinely accompanied by infiltration of inflammatory cells in the adventitia. However, the corrosion cast technique which is the method of choice for demonstrating morphological changes during vasospasm of the peripheral vessels can be regarded as being a form of blueprint of the above-described ultrastructural changes at the luminal surface of the basilar artery. In both models the inner surface of the spastic arteries showed distinct longitudinal folds, which were more prominent than those in normal arteries. Slight intimal folding can be found in normal animals too and these folds are not artifacts of the fixation procedure (9, 10, 12,19). However, in animals with experimental SAH the extensive intimal folding has to be regarded as the result of the luminal narrowing observed during cerebral vasospasm. Additionally in the vasospastic arteries in both animal models the normal cell borders of the endothelial cells can no longer be demonstrated. It is an important feature that experimental SAH induced by different techniques and in different animal species causes the identical morphological patterns. This is in contrast to a recent observation by Clower et al. (3) who did not find morphological signs of vasospasm in cats after injecting blood into the cisterna magna for simulation of SAH. Additionally it should be noted that the same ultrastructural changes can be observed not only in the vascular region close to the point of blood injection but also in the vascular periphery, a fact which is consistent with the concept of a proliferative vasculopathy as the major underlying cause of delayed vasospasm. As vessels demonstrated in the corrosion cast technique show signs of vasospasm in arteries which are usually too small to be visualized by angiography, it seems justified to assume that cerebral vasospasm not only affects the arteries at the base of the brain but also the vessels in the cerebral periphery with consequent negative impact on the cerebral microcirculation. REFERENCES 1. ALLEN, G. S. 1984. Cerebral 70-80.
arterial
spasm.
Clin.
Neurosurg.
32:
186
RICKELS ET .'AL.
2. AUSMANN, J. L., F. G. DIAZ, G. M. MALIK, A. S. FIELDING, AND 3. 4. 5.
6. 7. 8.
9. 10. 11.
CH. S. SON. 1985. Current management of cerebral aneurysms: Is it based on facts or myths? Surg. Neural. 24: 625-635. CLOWER, B. R., J. K. KAPP, N. A. MOORE, R. R. SMITH, AND J. L. HAINING. 1986: Intracistemal blood injection failed to produce cerebral angiopathy in cats. Exp. Neural. 94: 292-305. CONWAY, L. W., AND L. W. MCDONALD. 1972. Structural changes of the intradural arteries following subarachnoid hemorrhage. J. Neurosurg. 37: 715-723. FEIN, J. M., W. J. FLOR, S. L. COHEN, AND J. PARKHURST. 1974. Sequential changes of vascular ultrastructure in experimental cerebral vasospasm: Myonecrosis of subarachnoid arteries. J. Neurosurg. 64: 49-58. HUGHES, J. T., AND P. M. SCHIANCHI. 1978. Cerebral arterial spasm. A histological study of necropsy of the blood vessels in cases of subarachnoid hemorrhage. J. Neurosurg. 48: 93-100. KASSELL, N. F., T. SASAKI, A. R. T. COLOHAN, AND G. NAZAR. 1985. Cerebral vasospasm following aneurysmal subarachnoid hemorrhage. Stroke 16: 562-572. KASSELL, N. F., S. J. PEERLESS, AND CH G. DRAKE. 1980. Cerebral vasospasm: Acute proliferative vasculopathy? I. Hypothesis. Pages 85-87. in R. H. Wilkins, Ed., Cerebral Arterial Spasm: 2nd Workshop. Baltimore, Williams &Wilkins. KOJIMAHARA, M., AND G. DONEDA. 1980. Ultrastructural observations on bifurcations in rat cerebral arteries. Virchows Arch. (Cell Pathol.) 34: 21-32. KURGAN, G., D. GERTZ, AND R. S. WAINBERG. 1987. Intimal changes associated with arterial spasm induced by periarterial application of calcium chloride. Ezp. Mol. Pa&l. 39: 176-193. MIODONSKI, A., K. C. HODDE, AND C. BAKKER. 1976. Rasterelektronenmikroskopie von Plasik-Korrosionspraparaten Morpho-
12.
13.
14.
15.
16. 17.
18.
19.
20.
logische Unterschiede xwischen Arterien und Venen. Beitr. Elektronenmikroskap. Direktabb. OberfiL 9: 435-442. MURAKAMI, T. 1971. Application of the scanning electron microscope to the study of the fine distribution of the blood vessels. Arch. Histol. Jpn. 32: 445-454. NAKAI, K., H. IE~~AI,I. K-L, T. ITAKURO, N. KOMARI, K. KIMURA, T. NAGI, AND T. MAEDA. 1981. Microangioarchitecture of rat parietal cortex with special reference to vascular “sphincters.” Stroke 12: 653-659. RICHARDSON, M., M. W. C. HATI‘ON, M. R. BUCHANAN, AND S. MOORE. 1985. Scanning electron microscopy of normal rabbit aorta-Injury or artifact? J. Ultra&u& Res. 91: 159-173. RICKELS, E., S. HUSSEIN, H. WIEGAND, AND M. ZUMKELLER. 1987. Rasterelektronenmikroskopische Untersuchungen von HimgefX+en nach experimentell induzierter Subarachnoidalblutung. Verh. Anut. Ges. 81: 841-842. SANO, K. 1986. Cerebral vasospasm and aneurysm surgery. Clin. Neurosurg. 30: 13-58. SEIFERT, V., D. STOLKE, AND H.-A. TROST. 1988. Timing of aneurysm surgery: Comparison of operative results of early and delayed intervention. Eur. Arch. Psych&r. Neurol. Sci. 237: 291297. TANABE, T., P. J. BRANSON, AND J. F. ALKSNE. 1984. Intimal proliferation of cerebral arteries after subarachnoid blood injections in pigs. J. Neurosurg. 61: 494-500. TINDALL, A. R., AND E. SVENDSON. 1982. Intimal folds of the rabbit aorta. ActaAnut. 113: 169-177. VARSOS, V. G., T. M. LISCZAK, J. P. KISTLER, AND J. VIELMA. 1983. Delayed cerebral vasospasm is not reversible by aminophylline, nimodipine or papaverine in a “two hemorrhage” canine model. J. Neurosurg. 68: 11-17.
107,178-186
NEUROLOGY
(1990)
Corrugation of Cerebral Vessels following Subarachnoid Hemorrhage: Comparison of Two Experimental Models of Chronic Cerebral Vasospasm E. RICKELS,* *Neurosurgical
Clinic
V. SEIFERT,* M. ZUMKELLER,*
and TDepartment
of Electron
Microscopy
and Cell Biology,
The occurrence of delayed ischemic deficits due to the development of chronic cerebral vasospasm following subarachnoid hemorrhage is thought to be responsible for about 15% of the mortality and permanent morbidity of patients with ruptured intracranial aneurysms (1, 7, 16-18). Despite extensive laboratory and clinical investigations the pathogenesis of cerebral vasospasm could not be elucidated. However necropsy studies as well as experimental studies of cerebral vessels in spasm have shown that the vessel wall undergoes severe ultrastructural changes which are thought to form the morphological basis of delayed cerebral spasm (2, 4-6, 10, 19). On the basis of two different models of cerebral vasospasm we present a comparison of the morphological changes of the basilar artery in the dog and of peripheral cerebral vessels in the rat after experimental subarachnoid hemorrhage. AND
METHODS
Dog Model The experiments were performed with 20 mongrel dogs of both sexes weighting between 20 and 25 kg according to the “two hemorrhage model” of chronic vasospasm (20). After induction of anesthesia and endotracheal intubation the dogs were put on controlled ventilation. Using the femoral artery route an angiographic catheter was advanced to the vertebral artery. Angiography of the basilar artery was performed with 5 ml of Iopromit. Following angiography subarachnoid hemorrhage was simulated by injection of 4 ml of autologous blood into the cisterna magna (Fig. 1). Following injection the head of the dog was lowered for 30 min to allow distribution of the blood within the subarachnoid space. A second volume of blood was injected on Day 3 of the experiment. On Day 8 a control angiogram of the basilar artery was performed to angiographically demonstrate the presence and severity of the vessel narrowing (Fig. 2). Following intravital perfusion-fixation of the cerebral vessels with cacodylate-buffered glutaraldehyde, the 0014-4666/90 $3.00 Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
Medical
E. REALEt School,
Hannover,
West Germany
brain of the dog was removed and the basilar artery was dissected with the aid of a surgical microscope. Angiographical changes in the diameter of the basilar artery on Day 8 versus Day 1 were examined with a Zeiss stereo microscope and a lo-fold magnification. After measuring the diameter of the basilar artery at seven corresponding locations along the course of the vessel, the accumulated values were averaged and the mean reduction of the vessel diameter was calculated. Morphological changes in the arterial wall were demonstrated using light microscopic, scanning electron, and transmission electron microscopic examinations.
INTRODUCTION
MATERIAL
U. KUNZ,*AND
Rat Model A total number of 30 male Wistar rats weighting between 200 and 300 g were anesthesized with an intraperitoneal injection of 0.15 ml Rompun and 0.1 ml Ketanest per 100 mg body wt. Following microsurgical dissection of the atlantooccipital membrane the cisterna magna was punctured and 0.1 ml of CSF was withdrawn. After withdrawal of blood from the retrobulbar venous plexus, CSF and blood were mixed to prevent premature clotting and 0.1 ml of the mixture was injected into the cisterna magna. The procedure described above was repeated after 24 h. When the animals developed clinical signs of vasospasm with drowsiness and rigidity of the neck they were anesthesized again on Day 8. The thorax was opened and following exposure of the heart a canula was inserted into the ascending aorta and secured with ligation. The descending aorta was clamped and the right atrium was cut. Blood from the cerebral circulation was washed out with perfusion of Ringer’s solution at body temperature. Thereafter the vascular cerebral system was fixated by perfusion with Karnovsky’s solution containing 2.5% glutaraldehyde and 2.5% formaldehyde buffered in 0.04% sodium cacodylate. After fixation, Mercox resin prepared according to the manufacturer’s instruction was injected into the cerebral circulation. Following decapitation of the animal and removal of the soft tissue of the head, the skull was placed in 10% KOH solution containing 3% of detergent. The acquired clean cast was mounted and sputtered in an ion-coater (POALARON
178
CHRONIC
CEREBRAL
179
VASOSPASM
in the outer adventitia layer loose accumulation of inflammatory cells can be observed. In the transmission electron microscopic examination pathological changes can be demonstrated, especially at the endothelial vessel surface. The homogeneous layer of endothelial cells closely interconnected and with direct contact with the lamina elastica which can be observed in normal vessels has undergone severe ultrastructural changes with corrugation and desquamation of the endothelial cells which are lifted away from the underlying lamina. Additional vacuolation between the endothelial and muscularis layer can be demonstrated as well as ingrowth of fibrous tissue (Figs. 5 and 6). In the scanning electron microscopic examination the normal appearance of the endothelial layer with welldemarcated cell borders and homogeneous covering of the vessel lumen is replaced by an irregular-shaped appearance with partly extreme folding and corrugation of the endothelium. Due to the fact that the endothelial cells have become partly separated, the regular appear-
FIG.
1.
Angiogram
of the basal
artery
of the dog before
SAH.
E 5400) and examined using a Cambridge Stereo Scan 600 scanning electron microscope. In a control group (10 animals) the whole preparation of the corrosion cast was done in the described way without previous injection of blood in the cisterna magna. RESULTS
Dog Model Following experimental subarachnoid hemorrhage all animals developed severe angiographic vasospasm with a mean reduction of the basilar artery diameter on Day 8 as compared to that on Day 1 of more than 50% (Figs. 1 and 2). When the light microscopic appearance of the spastic basilar artery is compared to the normal appearance of the vessel, considerable narrowing of the vessel lumen as well as folding and corrugation of the intima and lamina elastica is demonstrable (Figs. 3 and 4). The muscularis layer does not show any severe ultrastructural changes in the light microscopic picture, whereas
FIG.
2.
Angiogram
of the same basilar
artery
8 days after
SAH.
FIG.
FIG lamina
. 4.
Light elastica.
microscopy
3.
Light
microscopy
(magnification,
160X).
(magnification,
Basilar
artery
130X).
Normal
of dog: reduction
180
basilar
artery
of lumen
of dog without
and folding
SAH.
and corrugation
of the intima
and
CHRONIC
FIG.
FIG.
6.
Transmission
5.
electron
Transmission
microscopy
electron
CEREBRAL
microscopy
(magnification,
(magnification,
3250X).
Basilar
181
VASOSPASM
4300X).
artery
Normal
of dog after
basilar
SAH:
artery
desquamation
of dog.
of the endothelial
cells.
FIG. surface.
7.
Scanning
electron
microscopy
(magnification,
134X).
Normal
FIG. thicken
8. Scanning electron microscopy ing of the vessel wall (arrows).
(magnification,
200X).
Basilar 182
basilar
artery
artery
of dog without
of dog with
vasospasm;
SAH:
smooth
severe
folding
fokling
of the il nner
of the inner
SUI
FIG.
9.
Scanning
electron
FIG. 10. Scanning electron cell scores are closer together.
microscopy
microscopy
(magnification,
(magnification,
470X).
630X).
Normal
Cerebral 183
cerebral
artery
artery
of rat: paralleled
of dog with
vasospasm:
cell cores slight
intensive
foldings.
of the inner
surface,
the
FIG.
FIG.
11.
12.
Very
Normal
small
cast of a very
vasospastic
artery
small
artery
of a rat’s brain
in the periphery 184
(magnification,
of the rat’s brain
1300X).
(magnification,
1700X)
CHRONIC
CEREBRAL
ante of the endothelial cell borders can no longer be demonstrated (Figs. 6-8). Rat Model Clinical signs of cerebral vasospasm were present in all of the experimental animals. The scanning electron microscope appearance of the control group demonstrates the well-known differentiation between arteries and veins as described by Miodonsky et al. (11). These consist of arteries having cell-nucleus depressions of ovoid shape which are paralleled by the outer border (Fig. 9). Veins show round depressions. The cell-nucleus depressions are surrounded by borderlines of irregular shape (11,9). In general the vessels of the control group demonstrate a smooth luminal surface with slight longitudinal folds. In the animals which had suffered from a SAH the luminal surface of the cast had distinct longitudinal folds with irregularities over wide parts of the vessels (Fig. 10). There was no stretching of vessels for fixation in our experiments. With regard to the corrosion cast it should be stated that the vessels were fixated while still in their anatomical location in the skull. Changes in the luminal diameter are therefore only possible by intimal folding, which will cause the smaller slit-like appearance of the cell nuclei. These folds could even be found in very small vessels in the cerebral periphery and remote from the experimental bleeding (Figs. 11 and 12). Additionally the nuclei impressions were pressed together so that it was impossible to differentiate the normal cell borders. DISCUSSION
In 1979, Kassell et al. summarizing the experimental and clinical data of different research groups as well as the results of their own investigations proposed the term “proliferative vasculopathy” for the morphological changes of the cerebral vessel wall during hemorrhageinduced vasospasm, due to their observation of proliferative fibrous tissue interposed between endothelium and lamina elastica (8). The assumption of severe ultrastructural changes of the arterial wall as the morphological basis of the angiographic narrowing seen after hemorrhage-induced spasm has been confirmed by recent experimental studies (5,10,15,19). The aim of our investigation was not only to demonstrate morphological changes of the cerebral vessels following SAH but also to compare the ultrastructural features of delayed vasospasm in larger vessels like the basilar artery and in small peripheral vessels of the rat, demonstrating that cerebral spasm not only affects the vasculature at the cranial base as demonstrated by angiography but also is propagated into the cerebral periphery. The general morphological picture of this chronic form of cerebral spasm can best be demonstrated experi-
185
VASOSPASM
mentally when investigating the basilar artery of the dog. These ultrastructural changes consist of severe folding of the endothelium with corrugation and denudation of the lamina elastica. The endothelium is often lifted away from the thickened intimal layer. Additional severe changes consist of intimal cellular proliferation with rupture and splitting of the internal elastic membrane. Necrosis of the muscular layer (myonecrosis) has been described but could not be observed in our experimental study. These changes at the endothelial and lamina elastica level are routinely accompanied by infiltration of inflammatory cells in the adventitia. However, the corrosion cast technique which is the method of choice for demonstrating morphological changes during vasospasm of the peripheral vessels can be regarded as being a form of blueprint of the above-described ultrastructural changes at the luminal surface of the basilar artery. In both models the inner surface of the spastic arteries showed distinct longitudinal folds, which were more prominent than those in normal arteries. Slight intimal folding can be found in normal animals too and these folds are not artifacts of the fixation procedure (9, 10, 12,19). However, in animals with experimental SAH the extensive intimal folding has to be regarded as the result of the luminal narrowing observed during cerebral vasospasm. Additionally in the vasospastic arteries in both animal models the normal cell borders of the endothelial cells can no longer be demonstrated. It is an important feature that experimental SAH induced by different techniques and in different animal species causes the identical morphological patterns. This is in contrast to a recent observation by Clower et al. (3) who did not find morphological signs of vasospasm in cats after injecting blood into the cisterna magna for simulation of SAH. Additionally it should be noted that the same ultrastructural changes can be observed not only in the vascular region close to the point of blood injection but also in the vascular periphery, a fact which is consistent with the concept of a proliferative vasculopathy as the major underlying cause of delayed vasospasm. As vessels demonstrated in the corrosion cast technique show signs of vasospasm in arteries which are usually too small to be visualized by angiography, it seems justified to assume that cerebral vasospasm not only affects the arteries at the base of the brain but also the vessels in the cerebral periphery with consequent negative impact on the cerebral microcirculation. REFERENCES 1. ALLEN, G. S. 1984. Cerebral 70-80.
arterial
spasm.
Clin.
Neurosurg.
32:
186
RICKELS ET .'AL.
2. AUSMANN, J. L., F. G. DIAZ, G. M. MALIK, A. S. FIELDING, AND 3. 4. 5.
6. 7. 8.
9. 10. 11.
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