Neuroradiolegv
Neuroradiology 11, 41--48 (1976)
© by Springer-Verlag 1976
The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow A. Ryttman Department of Neuroradiology,Karolinska Sjukhuset, Stockholm,Sweden
Summary.Of 65 patients with neurological disorders examined with rapid serial angiography of the carotid artery, 24 had normal cerebral arteries, 17 atherosclerosis, 11 arterial ectasia and 13 both kinds of vascular changes. These patients were examined for hemispherical rCBF determination on the same occasion, using the 133Xenon clearance method. Primarily, the patients were examined without general anaesthesia, and they did not have acute illness, trauma, or angiographic evidence of a focal intracranial lesion. In addition, other parameters such as arterial size, ventricular size, cerebral circulation time, age, and sex were determined. All these data were studied statistically in a series of multiple regression analyses with a computer. No significant differences in rCBF could be found between cases with ectasia, atherosclerosis and without any kind of vascular changes. However, the mean value of rCBF in patients with atherosclerosis and in patients with intracranial ectasia was below the normal mean value, although it did not differ significantly from this value. Nor was any influence on the rCBF found in patients with marked stenosis of the internal carotid artery and those with slight stenosis. Key words: Atherosclerosis, Cerebral blood flow, Carotid angiography, rCBF.
Stenotic lesions, such as atherosclerotic plaques, may be the cause of a reduction in blood flow to the brain. Several investigations have been carried out in order to study the influence of a reduction of the diameter of the large conducting arteries to the brain on the flow within these arteries [7, 11, 28, 29, 35]. There has also been some debate on the influence of pronounced dilatation, ectasia, of the cerebral arteries on regional
cerebral blood flow (CBF). Hultrn-Gyllensten et al., [20] claimed ectasia to be independent of atherosclerosis and to produce a reduction in CBF. Stenotic lesions are generally considered to produce a change in the pressure gradient and in the local flow in the constricted vessel only when its lumen is reduced to 25 % of the normal size [11, 28]. However, a reduced flow within a supplying vessel does not necessarily imply a reduced rCBF in the brain, since compensation may occur by way of collateral circulation [5, 31]. CBF has been studied by Boysen [4] in patients with occlusive disease by means of the 133Xenon clearance method during vascular surgery under general anaesthesia. Boysen used this method to study the intracranial collateral circulation during a test occlusion of the carotid artery. When the carotid artery was clamped, a 41% (average) reduction was found in the rCBF. At the beginning of the examination the rCBF was 51 ml/100 g brain tissue/min, which corresponds to a normal mean value. However, as Boysen points out, cerebral blood flow may be influenced by several factors when the examination is carried out under general anaesthesia. Halothane, which was used in Boysen's study, often increases cerebral blood flow [6, 30]. The pCO 2 values were high (mean 49.4 mmHg) which may explain to some degree the relatively high value of rCBF. Engell et al., [13] found, however, that during carotid surgery, with halothane anaesthesia, patients had a low or normal cerebral blood flow when the anaesthesia had been maintained for 2-4 h. Some of the patients in Boysen's material still had neurological symptoms at the time of operation. It would appear to be of great interest to study the influence of different degrees of stenosis of the carotid artery on the CBF in patients without acute illness, trauma, hydrocephalus or angiographic evidence of a focal intracranial lesion and not influenced by general
A. Ryttman: The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow
42
anaesthesia. No investigation of the influence of aterial ectasia on rCBF under similar conditions has yet been carried out. Hult6n-Gyllensten et al., [20] claimed ectasia of the cerebral arteries to be independent of atherosclerosis and to produce a reduction in cerebral blood flow. These findings could not be confirmed by Ryttman [32] who found the CBF to be more closely related to the dilatation of the cerebral ventricles than to the degree of ectasia. However, this material was small and included patients with hydrocephalus in whom the reduction in CBF might have been secondary to mental deterioration [18].
Material
The material consisted of 65 patients, mean age 48.6 years (range 19-73), 33 were males, mean age 47.3 years (range 19-72), and 32 females, mean age 49.9 years (range 19-73) (Table 1). The material was selected from a routine series of patients with neurological disorders judged according to the follwing principles. Patients with atherosclerosis, with ectasia, and with normal vessels, as revealed by cerebral angiography, were primarily se-
Table 1. T h e distribution of the material in sex and age
Females
~.
Males
~ ~
**
.~
*~
g¢
20
~*~ ~ * ~
~ ** *~
¢¢
30
40
50
60
70
lected. Patients with acute illness, trauma, or angiographic evidence of a focal intracranial lesion were not included. 24 patients had neither atherosclerosis nor ectasia and were considered to be normal, 11 patients had ectasia but no atherosclerosis, and 17 patients had atherosclerosis without ectasia. 13 patients had both kinds of vascular changes. The 24 "normal" patients were included as a reference groupi In all these patients a film of the area of the carotid bifurcation in the neck was taken in order to comfirm or exclude atherosclerosis. 13 had epilepsy, 4 cranial nerve palsy, 10 headache or neuralgia, 19 had transitory ischemic attacks without any persistent symptoms, 3 hemianopia, 3 vertigo or syncope, 9 had slight disturbances of mental function but no evidence of communicating hydrocephalus. The remaining 4 patients had various extracranial lesions such as spindleshaped pulsating tumour in the neck, murmur over the carotid artery in the neck and arteriovenous malformation supplied by the external carotid artery only (Table 2).
Methods
All patients were examined with rapid serial angiography of the carotid artery. On the same occasion hemispheric rCBF determination using the 133Xenon clearance method [21, 24, 25, 26, 27] was carried out. The interval between the CBF determination and the angiography was at least 10 min. Angiography was performed either by direct puncture of the common carotid artery using a polyethylene cannula which was advanced into the internal carotid artery, or by puncture of the femoral artery using a 160 PA polyethylene catheter which was introduced into the internal carotid artery under fluoroscopic control. One lateral and two frontal projections (orbital and supraorbital) were taken and, with the catheter in the same position, 133Xenon was injected. In addition, a lateral projec-
Table 2. T h e distribution of the diagnosis in patients with different vascular changes
Epilepsy Cranial nerve paresis Headache or neuralgia TIA Hemianopia Syncope or vertigo Disturbances of m e m o r y O t h e r diagnoses
Normal vessel
Atherosclerotic vessel
4 2 3 6 1 1 5 2
4
Internal
Ectasia External
Internal and external
1
1
1 1
3
1 2 5 1 1 3 1
1 1 1
Ectasia and atherosclerosis
3 1 1 7 1
A. Ryttman: The Influence of Atherosclelosis and Ectasia on Cerebral Blood Flow
43
Fig. 1, Typical signs are folds located in iLhe concavity of the kink (see arrow) together with widening and tortuosity in ectasia of the internal carotid artery
Fig, 2. The "umbrella appearance" of the carotid siphon and the anterior and middle cerebral arteries in AP projection in cases with ectasia
tion centred over the carotid bifurcation was taken after the catheter had been pulled down into the common carotid artery. The arterial size was established partly by inspection and partly by direct measurement. Ectasia was defined as dilatation, tortuosity, and kinking of the arteries. A distinction was made between changes occurring in the extracranial part at the internal carotid artery and those occurring in its intracranial part. Typical signs of ectasia in the extracranial carotid artery (Fig. 1) are the folds in the wall of the vessel located in the concavity of the kink [1, 3]. Intracranially, the "umbrella appearance" (Fig. 2) of the carotid siphon, and the anterior and middle cerebral arteries in the AP projection, is characteristic of ectasia [15, 20, 37]. From these criteria the diagnosis of ectasia in the present selected material was made in 24 out of 65 patients. The size of the extra- and intracranial parts of the internal carotid artery was also determined by measurement of their diameters. The internal carotid and middle cerebral arteries were measured according to the method of Gabrielsen and Greitz [14] at the levels M, C and C5. Each single observation was registered as the difference between the measured size and the expected mean normal value at the same level calculated according to the formula of Gabrielsen and Greitz. The lumen diameters of the internal and common carotid arteries were measured about 2 cm from the bifurcation in each direction. Measurements of the
stenotic lesionswere also carried out where the stenosis was most pronounced. These values were compared with the normal diameter of the lumen adjacent to the stenotic lesion. The atherosclerotic changes were also determined by inspection and divided into two groups. Patients with atherosclerotic lesions with a reduction of more than 50% in the diameter of the stenosis were included in the first group. The remaining patients with atherosclerotic lesions were allotted to a second group. The ventricular size was estimated by angiography according to the method of Bergvall and Galera [2] as the quotient between ventricular width as seen in the venous phase in the AP projection, and skull width. The cerebral circulation time (CCT) was estimated according to Greitz [16, 17]. CBF was determined by the 133Xenon clearance method by using a large, single detector with a 2 inch crystal [26]. In 17 cases the two compartmental analysis was applied [22, 26, 34]. In the remaining patients the "initial slope" method [23] was used and the flow values were converted to the corresponding expected mean values by the two compartmental method according to the formula of Wilkinson et al., [38]. All CBF values were corrected for arterial p C O 2. The data were subjected to statistical study in a series of multiple regression analyses performed with a computer. CBF was used as dependent variable. An investigation was then made of the manner in which
44
A. Ryttman: The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow
Table 3. Mean value of rCBF (pCO 2 corrected), mean age and mean ventricular index in patients with and without ectasia or atherosclerosis Number
Mean value Diff. from of CBF normal CBF (pCO 2 corrected) value and its SD
Mean age Mean ventricular index
Patients without vessel changes Men Women Men and women
13 11 24
45.9 + 5.9 49.0 + 8.9 47.3 _+ 7.4
-6.2 + 8.6 -3.1 + 10.7 -4.8 ___9.7
39.5 42.4 40.8
27.3 + 3.9 27.2 + 3.4 27.3 + 3.6
46.8 55.7 51.6
28.4 + 5.1 24.8 + 2.6 26.5 + 4.2
48.4 50.5 49.6
27.5 + 1.2 29.2 _+ 3.0 28.5 + 2.5
Patients with ectasia Men Women Men and women
5 6 11
46.9 + 9.1 48.1 + 5.1 47.5 + 6.8
-5.2 + 10.9 -4.0 + 8.1 -4.6 + 9.3
Patients with atherosclerosis Men Women Men and women
7 10 17
39.1 + 5.1 48.2 + 8.2 44.2 + 8.2
-13.0 + 8.1 - 3.9 + 10.3 - 7.9 _+ 10.3
Patients with ectasia and atherosclerosis Men Women Men and women
8 5 13
42.0 + 5.7 47.3 + 4.6 43.1 + 5.7
-10.1 + 8.5 - 4.8 +_ 7.8 - 9.1 + 8.5
59.5 54.2 57.5
30.0 + 4.2 27.2 + 1.8 28.9 _+ 3.6
Table 4. Mean value of rCBF (pCO 2 corrected), mean age and mean ventricular index in patients with different kinds of ectasia and different degrees of atherosclerosis Number of patients Internal ectasia External ectasia Internal and external ectasia Atherosclerosis with more than 50% reduction of the lumen diameter Atherosclerosis with less than 50% reduction of the lumen diameter
4 3 4 5 25
rCBF
Age
Ventricular index
+ 2.9 __+1.6 + 9.4 -4- 4.5
59.8 47.0 47.0 56.0
26.3 28.3 25.3 27.2
43.8 + 7.5
53.2
29.0 + 2.8
43.6 53.5 47.0 44.4
S.D.
this dependent variable was affected by the simultaneous variation of independent background variables s u c h as a g e , sex, a t h e r o s c l e r o s i s , e c t a s i a a n d v e n t r i c u l a r size a n d t h e d i a m e t e r s o f t h e v e s s e l s . T h e d e pendent variable was also studied in relation to each background independent variable in order to judge the degree of dependence when other independent variables were held constant.
Results A s s h o w n i n T a b l e 3, n o s i g n i f i c a n t d i f f e r e n c e s i n mean rCBF was found between the reference group on the one hand and any one of the three groups of
+ 5.6 __+4.9 + 2.4 + 3.8
patients with vascular changes on the other, nor between these latter groups. Men with atherosclerosis when studied separately had, however, a significantly r e d u c e d m e a n C B F o r 3 9 . 1 + 5.1 m l / 1 0 0 g b r a i n t i s s u e / m i n as c o m p a r e d w i t h 4 8 . 2 + 8 . 2 m l / 1 0 0 g / r a i n i n w o m e n w i t h a t h e r o s c l e r o s i s a n d w i t h 4 7 . 3 _+ 7 . 4 ml/100 g/min in the reference group. No differences were found between men and women in patients with ectasia. Patients with intracranial ectasia had a mean flow of 43.6 + 2.9 ml/100 g/rain; those with extracran i a l e c t a s i a h a d a m e a n C B F o f 5 3 . 5 + 1.6 m l / 1 0 0 g/min, a difference which was not significant. In the 5 cases with severe atherosclerotic stenosis and a lumen diameter reduced by more than 50%, the
A. Ryttman: The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow Table 5. T values and significances obtained in regression analysis when relating mean value of rCBF (pCO 2 corrected) as dependent variable to sex, age and ventricular index as independent variables. These variables are singly introduced into the analysis. (Degree of freedom = 64)
Independent variables
Dependent variable Mean value of rCBF (pCO 2 corr.)
Sex Age Ventricular index
t value -2.24 -2.60 -1.75
p < 0.05
Neuroradiology 11, 41--48 (1976)
© by Springer-Verlag 1976
The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow A. Ryttman Department of Neuroradiology,Karolinska Sjukhuset, Stockholm,Sweden
Summary.Of 65 patients with neurological disorders examined with rapid serial angiography of the carotid artery, 24 had normal cerebral arteries, 17 atherosclerosis, 11 arterial ectasia and 13 both kinds of vascular changes. These patients were examined for hemispherical rCBF determination on the same occasion, using the 133Xenon clearance method. Primarily, the patients were examined without general anaesthesia, and they did not have acute illness, trauma, or angiographic evidence of a focal intracranial lesion. In addition, other parameters such as arterial size, ventricular size, cerebral circulation time, age, and sex were determined. All these data were studied statistically in a series of multiple regression analyses with a computer. No significant differences in rCBF could be found between cases with ectasia, atherosclerosis and without any kind of vascular changes. However, the mean value of rCBF in patients with atherosclerosis and in patients with intracranial ectasia was below the normal mean value, although it did not differ significantly from this value. Nor was any influence on the rCBF found in patients with marked stenosis of the internal carotid artery and those with slight stenosis. Key words: Atherosclerosis, Cerebral blood flow, Carotid angiography, rCBF.
Stenotic lesions, such as atherosclerotic plaques, may be the cause of a reduction in blood flow to the brain. Several investigations have been carried out in order to study the influence of a reduction of the diameter of the large conducting arteries to the brain on the flow within these arteries [7, 11, 28, 29, 35]. There has also been some debate on the influence of pronounced dilatation, ectasia, of the cerebral arteries on regional
cerebral blood flow (CBF). Hultrn-Gyllensten et al., [20] claimed ectasia to be independent of atherosclerosis and to produce a reduction in CBF. Stenotic lesions are generally considered to produce a change in the pressure gradient and in the local flow in the constricted vessel only when its lumen is reduced to 25 % of the normal size [11, 28]. However, a reduced flow within a supplying vessel does not necessarily imply a reduced rCBF in the brain, since compensation may occur by way of collateral circulation [5, 31]. CBF has been studied by Boysen [4] in patients with occlusive disease by means of the 133Xenon clearance method during vascular surgery under general anaesthesia. Boysen used this method to study the intracranial collateral circulation during a test occlusion of the carotid artery. When the carotid artery was clamped, a 41% (average) reduction was found in the rCBF. At the beginning of the examination the rCBF was 51 ml/100 g brain tissue/min, which corresponds to a normal mean value. However, as Boysen points out, cerebral blood flow may be influenced by several factors when the examination is carried out under general anaesthesia. Halothane, which was used in Boysen's study, often increases cerebral blood flow [6, 30]. The pCO 2 values were high (mean 49.4 mmHg) which may explain to some degree the relatively high value of rCBF. Engell et al., [13] found, however, that during carotid surgery, with halothane anaesthesia, patients had a low or normal cerebral blood flow when the anaesthesia had been maintained for 2-4 h. Some of the patients in Boysen's material still had neurological symptoms at the time of operation. It would appear to be of great interest to study the influence of different degrees of stenosis of the carotid artery on the CBF in patients without acute illness, trauma, hydrocephalus or angiographic evidence of a focal intracranial lesion and not influenced by general
A. Ryttman: The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow
42
anaesthesia. No investigation of the influence of aterial ectasia on rCBF under similar conditions has yet been carried out. Hult6n-Gyllensten et al., [20] claimed ectasia of the cerebral arteries to be independent of atherosclerosis and to produce a reduction in cerebral blood flow. These findings could not be confirmed by Ryttman [32] who found the CBF to be more closely related to the dilatation of the cerebral ventricles than to the degree of ectasia. However, this material was small and included patients with hydrocephalus in whom the reduction in CBF might have been secondary to mental deterioration [18].
Material
The material consisted of 65 patients, mean age 48.6 years (range 19-73), 33 were males, mean age 47.3 years (range 19-72), and 32 females, mean age 49.9 years (range 19-73) (Table 1). The material was selected from a routine series of patients with neurological disorders judged according to the follwing principles. Patients with atherosclerosis, with ectasia, and with normal vessels, as revealed by cerebral angiography, were primarily se-
Table 1. T h e distribution of the material in sex and age
Females
~.
Males
~ ~
**
.~
*~
g¢
20
~*~ ~ * ~
~ ** *~
¢¢
30
40
50
60
70
lected. Patients with acute illness, trauma, or angiographic evidence of a focal intracranial lesion were not included. 24 patients had neither atherosclerosis nor ectasia and were considered to be normal, 11 patients had ectasia but no atherosclerosis, and 17 patients had atherosclerosis without ectasia. 13 patients had both kinds of vascular changes. The 24 "normal" patients were included as a reference groupi In all these patients a film of the area of the carotid bifurcation in the neck was taken in order to comfirm or exclude atherosclerosis. 13 had epilepsy, 4 cranial nerve palsy, 10 headache or neuralgia, 19 had transitory ischemic attacks without any persistent symptoms, 3 hemianopia, 3 vertigo or syncope, 9 had slight disturbances of mental function but no evidence of communicating hydrocephalus. The remaining 4 patients had various extracranial lesions such as spindleshaped pulsating tumour in the neck, murmur over the carotid artery in the neck and arteriovenous malformation supplied by the external carotid artery only (Table 2).
Methods
All patients were examined with rapid serial angiography of the carotid artery. On the same occasion hemispheric rCBF determination using the 133Xenon clearance method [21, 24, 25, 26, 27] was carried out. The interval between the CBF determination and the angiography was at least 10 min. Angiography was performed either by direct puncture of the common carotid artery using a polyethylene cannula which was advanced into the internal carotid artery, or by puncture of the femoral artery using a 160 PA polyethylene catheter which was introduced into the internal carotid artery under fluoroscopic control. One lateral and two frontal projections (orbital and supraorbital) were taken and, with the catheter in the same position, 133Xenon was injected. In addition, a lateral projec-
Table 2. T h e distribution of the diagnosis in patients with different vascular changes
Epilepsy Cranial nerve paresis Headache or neuralgia TIA Hemianopia Syncope or vertigo Disturbances of m e m o r y O t h e r diagnoses
Normal vessel
Atherosclerotic vessel
4 2 3 6 1 1 5 2
4
Internal
Ectasia External
Internal and external
1
1
1 1
3
1 2 5 1 1 3 1
1 1 1
Ectasia and atherosclerosis
3 1 1 7 1
A. Ryttman: The Influence of Atherosclelosis and Ectasia on Cerebral Blood Flow
43
Fig. 1, Typical signs are folds located in iLhe concavity of the kink (see arrow) together with widening and tortuosity in ectasia of the internal carotid artery
Fig, 2. The "umbrella appearance" of the carotid siphon and the anterior and middle cerebral arteries in AP projection in cases with ectasia
tion centred over the carotid bifurcation was taken after the catheter had been pulled down into the common carotid artery. The arterial size was established partly by inspection and partly by direct measurement. Ectasia was defined as dilatation, tortuosity, and kinking of the arteries. A distinction was made between changes occurring in the extracranial part at the internal carotid artery and those occurring in its intracranial part. Typical signs of ectasia in the extracranial carotid artery (Fig. 1) are the folds in the wall of the vessel located in the concavity of the kink [1, 3]. Intracranially, the "umbrella appearance" (Fig. 2) of the carotid siphon, and the anterior and middle cerebral arteries in the AP projection, is characteristic of ectasia [15, 20, 37]. From these criteria the diagnosis of ectasia in the present selected material was made in 24 out of 65 patients. The size of the extra- and intracranial parts of the internal carotid artery was also determined by measurement of their diameters. The internal carotid and middle cerebral arteries were measured according to the method of Gabrielsen and Greitz [14] at the levels M, C and C5. Each single observation was registered as the difference between the measured size and the expected mean normal value at the same level calculated according to the formula of Gabrielsen and Greitz. The lumen diameters of the internal and common carotid arteries were measured about 2 cm from the bifurcation in each direction. Measurements of the
stenotic lesionswere also carried out where the stenosis was most pronounced. These values were compared with the normal diameter of the lumen adjacent to the stenotic lesion. The atherosclerotic changes were also determined by inspection and divided into two groups. Patients with atherosclerotic lesions with a reduction of more than 50% in the diameter of the stenosis were included in the first group. The remaining patients with atherosclerotic lesions were allotted to a second group. The ventricular size was estimated by angiography according to the method of Bergvall and Galera [2] as the quotient between ventricular width as seen in the venous phase in the AP projection, and skull width. The cerebral circulation time (CCT) was estimated according to Greitz [16, 17]. CBF was determined by the 133Xenon clearance method by using a large, single detector with a 2 inch crystal [26]. In 17 cases the two compartmental analysis was applied [22, 26, 34]. In the remaining patients the "initial slope" method [23] was used and the flow values were converted to the corresponding expected mean values by the two compartmental method according to the formula of Wilkinson et al., [38]. All CBF values were corrected for arterial p C O 2. The data were subjected to statistical study in a series of multiple regression analyses performed with a computer. CBF was used as dependent variable. An investigation was then made of the manner in which
44
A. Ryttman: The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow
Table 3. Mean value of rCBF (pCO 2 corrected), mean age and mean ventricular index in patients with and without ectasia or atherosclerosis Number
Mean value Diff. from of CBF normal CBF (pCO 2 corrected) value and its SD
Mean age Mean ventricular index
Patients without vessel changes Men Women Men and women
13 11 24
45.9 + 5.9 49.0 + 8.9 47.3 _+ 7.4
-6.2 + 8.6 -3.1 + 10.7 -4.8 ___9.7
39.5 42.4 40.8
27.3 + 3.9 27.2 + 3.4 27.3 + 3.6
46.8 55.7 51.6
28.4 + 5.1 24.8 + 2.6 26.5 + 4.2
48.4 50.5 49.6
27.5 + 1.2 29.2 _+ 3.0 28.5 + 2.5
Patients with ectasia Men Women Men and women
5 6 11
46.9 + 9.1 48.1 + 5.1 47.5 + 6.8
-5.2 + 10.9 -4.0 + 8.1 -4.6 + 9.3
Patients with atherosclerosis Men Women Men and women
7 10 17
39.1 + 5.1 48.2 + 8.2 44.2 + 8.2
-13.0 + 8.1 - 3.9 + 10.3 - 7.9 _+ 10.3
Patients with ectasia and atherosclerosis Men Women Men and women
8 5 13
42.0 + 5.7 47.3 + 4.6 43.1 + 5.7
-10.1 + 8.5 - 4.8 +_ 7.8 - 9.1 + 8.5
59.5 54.2 57.5
30.0 + 4.2 27.2 + 1.8 28.9 _+ 3.6
Table 4. Mean value of rCBF (pCO 2 corrected), mean age and mean ventricular index in patients with different kinds of ectasia and different degrees of atherosclerosis Number of patients Internal ectasia External ectasia Internal and external ectasia Atherosclerosis with more than 50% reduction of the lumen diameter Atherosclerosis with less than 50% reduction of the lumen diameter
4 3 4 5 25
rCBF
Age
Ventricular index
+ 2.9 __+1.6 + 9.4 -4- 4.5
59.8 47.0 47.0 56.0
26.3 28.3 25.3 27.2
43.8 + 7.5
53.2
29.0 + 2.8
43.6 53.5 47.0 44.4
S.D.
this dependent variable was affected by the simultaneous variation of independent background variables s u c h as a g e , sex, a t h e r o s c l e r o s i s , e c t a s i a a n d v e n t r i c u l a r size a n d t h e d i a m e t e r s o f t h e v e s s e l s . T h e d e pendent variable was also studied in relation to each background independent variable in order to judge the degree of dependence when other independent variables were held constant.
Results A s s h o w n i n T a b l e 3, n o s i g n i f i c a n t d i f f e r e n c e s i n mean rCBF was found between the reference group on the one hand and any one of the three groups of
+ 5.6 __+4.9 + 2.4 + 3.8
patients with vascular changes on the other, nor between these latter groups. Men with atherosclerosis when studied separately had, however, a significantly r e d u c e d m e a n C B F o r 3 9 . 1 + 5.1 m l / 1 0 0 g b r a i n t i s s u e / m i n as c o m p a r e d w i t h 4 8 . 2 + 8 . 2 m l / 1 0 0 g / r a i n i n w o m e n w i t h a t h e r o s c l e r o s i s a n d w i t h 4 7 . 3 _+ 7 . 4 ml/100 g/min in the reference group. No differences were found between men and women in patients with ectasia. Patients with intracranial ectasia had a mean flow of 43.6 + 2.9 ml/100 g/rain; those with extracran i a l e c t a s i a h a d a m e a n C B F o f 5 3 . 5 + 1.6 m l / 1 0 0 g/min, a difference which was not significant. In the 5 cases with severe atherosclerotic stenosis and a lumen diameter reduced by more than 50%, the
A. Ryttman: The Influence of Atherosclerosis and Ectasia on Cerebral Blood Flow Table 5. T values and significances obtained in regression analysis when relating mean value of rCBF (pCO 2 corrected) as dependent variable to sex, age and ventricular index as independent variables. These variables are singly introduced into the analysis. (Degree of freedom = 64)
Independent variables
Dependent variable Mean value of rCBF (pCO 2 corr.)
Sex Age Ventricular index
t value -2.24 -2.60 -1.75
p < 0.05
