Comparison of regional vasomotor responses to acetazolamide and CO2 in rabbit cerebrum and cerebellum, measured by a hydrogen clearance method

AIM

Many investigators have proved the usefulness of acetazolamide provocation and the carbon dioxide test for assessment of the local cerebrovascular reactivity by measurement of the regional cerebral blood flow in patients with occlusive cerebrovascular disease. Data originating from a comparison of these two different vasomotor stimuli as concerns the differences in sensitivity to them in various parts of the central nervous system are scarce. Our aim was to compare the cerebral blood flow responses to hypercapnic and acetazolamide stimuli in different brain regions.

METHODS

The cerebral blood flow was measured in the cerebrum (cortex and caudate nucleus) and cerebellum (cortex), as measured by a hydrogen clearance method in anaesthetized, artificially ventilated rabbits.

RESULTS

In normocapnia, the cerebral blood flow values in the cerebrum and the cerebellum differed significantly. The cerebral blood flow responses to both vasodilatory stimuli were to be significantly higher in the cerebrum than in the cerebellum, but the relative increases, i.e. the mean relative reactivities, were similar in the different regions measured.

CONCLUSION

The regional dissimilarity might explain to some extent the different sensitivities of the various brain areas to sudden blood pressure changes (infarction or haemorrhage). The results further suggest that heterogeneity in cerebrovascular reactivity should be considered in the assessment of vasoreactivity in patients with occlusive cerebrovascular disease. Since the comparison of the carbon dioxide and acetazolamide-induced cerebrovascular reactivities revealed a strong linear relationship, it was concluded that acetazolamide provocation is equivalent to the carbon dioxide test in the evaluation of cerebrovascular reactivity.

Dynamics and regional distribution of c-fos protein expression in rat brain after a closed head injury

The objective of this study was to define the time- and brain-area-related distribution of c-fos expression in the brain during the first 24 h following a closed head injury in rats. In the control groups (n = 32), only a few c-fos positive nuclei were observed in the brain and the c-fos staining did not change during the next 24 h. In the closed head injury group c-fos-positive cells were rare in the brain regions during the first 30 min. During the next 2 h, the number of c-fos-positive cells increased rapidly in the basal ganglions, the ventricular ependyma cells the corticospinal tract, the area postrema, the cerebral neocortex, and the corpus callosum. The increase was highest in the corpus callosum (317 +/- 44.5 mm(-2)), in the thalamic reticular nucleus (474.8 +/- 49.2 mm(-2)), in the dentate hilus (1090 +/- 187 mm(-2)) and in the cerebral neocortex (992 +/- 93 mm(-2)). Thereafter, the elevated c-fos expression gradually decreased and at 6 h post-closed head injury no significant differences were observed between the controls and the trauma group. We conclude that a closed head injury induces a large, transient increase of c-fos expression in the brain. Since the observed time course and regional differences in c-fos expression are in good agreement with the cognitive and memory deficits observed after human TBI it can be utilized in further investigations, especially to test the effects of various forms of pharmacological or cellular therapy.

[Odontoidectomy in the treatment of medically refractory, neurogenic hypertension]

The authors present a case of medically refractory, neurogenic hypertension where the MR examination revealed an odontoid compression of the anterior medulla as a consequence of a basilar impression. Following transoral odontoidectomy and craniocervical fixation, the blood pressure in the 24-year-old woman returned to normal, and 1 year postoperatively she remains normotensive and off all medication. This reported case provides further support to the theory that there is a subgroup of patients who may have a vascular compression of the medulla with no neurological symptoms other than hypertension.

[Cerebral edema and changes of cerebral blood volume in patients with head injuries]

AIM

The pathogenesis of traumatic brain swelling remains unclear. The generally held view is that brain swelling is caused primarily by vascular engorgement and that edema plays a relatively minor role in the swelling process. The goal of this study was to examine the roles of cerebral blood volume (CBV) and edema in traumatic brain swelling.

PATIENTS AND METHODS

Both brain-tissue water and CBV were measured in 76 head-injured patients, and the relative contribution of edema and blood to total brain swelling was determined. Comparable measures of brain-tissue water were obtained in 30 healthy volunteers and CBV in seven volunteers. Brain edema was measured using magnetic resonance imaging, implementing a new technique for accurate measurement of total tissue water. Measurements of CBV in subgroup of 31 head-injured patients were based on consecutive measures of cerebral blood flow (CBF) obtained using stable xenon and calculation of mean transit time by dynamic computerized tomography scanning after a rapid bolus injection of iodinated contrast material.

RESULTS

The mean (+/- standard deviation) percentage of swelling due to water was 9.37 +/- 8.7%, whereas that due to blood was -0.8 +/- 1.32%.

CONCLUSION

The results of this study showed that brain edema is the major fluid component contributing to traumatic brain swelling. Moreover, CBV is reduced in proportion to CBF reduction following severe brain injury.

Decreased cutaneous vasodilatation to isometric handgrip exercise in Alzheimer's disease

BACKGROUND

Cutaneous active vasodilatation is a cholinergic nerve mediated function of the sympathetic nervous system and the disturbed function of cholinergic neurotransmission is known as a prominent feature of Alzheimer's disease (AD).

METHODS

To assess this relationship, skin blood flow (SkBF) and other haemodynamic parameters were determined by a simple vasodilatory test, isometric handgrip exercise (IHG), in 22 late-onset sporadic type AD and 20 aged control persons (AC).

RESULTS

Significantly higher cutaneous vascular resistance and decreased SkBF were found after the stimulus in the AD group. A smaller reduction (p < 0.03) of R wave intervals on the electrocardiogram was observed in the AD group compared to the AC one. After IHG, change in systolic blood pressure was less in the AD (p < 0.01) than in the AC group.

CONCLUSION

Our results suggest that autonomic dysfunction affecting active vasodilator sympathetic, as well as parasympathetic functions is present in AD.

[Surgical treatment of giant basilar artery aneurysm with induced hypothermia and circulatory arrest]

Surgical management of giant and complex posterior circulation aneurysms continues to be a technically difficult task with high operative morbidity. To minimize morbidity we have used cardiopulmonary bypass and circulatory arrest for the treatment of a giant basilar aneurysm. A 48-year-old woman presented with sudden headache. Magnetic resonance angiography revealed a giant basilar aneurysm. On the 2nd hospital day she developed right sided hemiparesis and cranial nerve deficits as a result of the second rupture of the aneurysm. The aneurysm was successfully treated and no significant neurological complications were related to this technique. This initial experience indicates that patients with giant posterior circulation aneurysm that cannot be treated using conventional techniques might benefit from a surgical approach that included the use of deep hypothermic circulatory arrest.

[Results of surgical treatment in hemifacial spasm--the role of MR-angiography in detecting microvascular compression]

The authors evaluated the follow-up results of microvascular decompression (sec. Janetta) in 8 patients with hemifacial spasm (HFS). Indication was based on there dimensional time of flight magnetic resonance angiography with 0.5T Elscint Gyrex V Dix equipment. Contrast material was administered in every case and maximum intensity projection and thin slice reconstruction were performed in three standard directions. Vascular contact with the facial nerve in the entry zone was identified on the symptomatic side in 10 patients. No contact was detected in 2 cases. Microvascular decompression was performed in 8 cases. The surgical and neuroradiological findings were identical in every cases. Five patients were completely free of HFS immediately after surgery, and another 2 patients became free of HFS during the next few weeks. Only 1 patient had uncured symptoms. In conclusion, the authors suggest that microvascular decompression of the facial nerve may evolve as the method of choice if vascular contact is proved by 3D TOF MRA.

Three-dimensional time-of-flight MR angiography in trigeminal neuralgia on a 0.5-T system

The goal of this study was to analyze the diagnostic value of three-dimensional time-of-flight magnetic resonance angiography (3D TOF MRA), performed on a 0.5-T system in the detection of neurovascular compression in patients with trigeminal neuralgia (TN). One hundred seventy-two TN patients were examined using plain and contrast-enhanced 3D TOF MRA on a 0.5-T system. Maximum intensity projection (MIP) reconstruction was performed in three standard planes. Both the original and the reconstructed images were studied to search for vascular compression shown by close neurovascular contact and/or dislocation of the trigeminal nerve. Forty-two TN patients underwent surgical exploration of the posterior fossa. Results of MRA were compared with clinical data in all cases and to result of surgery in the surgically treated cases. Neurovascular contact at the root entry zone of the trigeminal nerve was detected on the symptomatic side in 94 patients, and on the asymptomatic side in 12 patients. Sensitivity, specificity, accuracy, as well as positive and negative predictive value of 3D TOF MRA in the detection of neurovascular compression in the patient group undergoing surgery, were 97.6, 92.5, 95.0, 93.0, and 97.4%, respectively. Three-dimensional TOF MRA performed on a 0.5-T system appears to be not less effective than similar examinations by higher field strength devices in the detection of neurovascular contact. This sequence accurately demonstrates the presence of neurovascular compression, and in this way valuable information may be achieved for the planning of surgical therapy of patients with trigeminal neuralgia.

Influence of nitrovasodilators and cyclooxygenase inhibitors on cerebral vasoreactivity in conscious rabbits

Since the nitric oxide (NO) and cyclooxygenase pathways have been suggested to have important roles in most vasodilations, our aim was to study the influence of cyclooxygenase inhibitors and nitrovasodilators on cerebrovascular reserve capacity. Corticocerebral blood flow was measured by hydrogen polarography during hypercapnia and acetazolamide stimuli in conscious rabbits. The measurements were repeated in the presence of N(omega)-nitro-L-arginine methyl ester (L-NAME) and indomethacin as nitric oxide synthase (NOS) and cyclooxygenase inhibitors. The effects of nitroglycerin and isosorbide-5-nitrate were also tested. L-NAME completely, while indomethacin markedly inhibited the hypercapnic corticocerebral blood flow response. Nitroglycerin and isosorbide-5-nitrate significantly attenuated hypercapnia elicited corticocerebral blood flow increase. The different treatments reduced only moderately the acetazolamide-induced corticocerebral blood flow response. These results lend support to the hypothesis that antithrombotic and antiinflammatory medication (cyclooxygenase inhibitors) and nitrovasodilator treatments could interfere with the measurement of cerebrovascular reactivity resulting in underestimation of the cerebrovascular reserve capacity in patients taking these drugs.

Contribution of edema and cerebral blood volume to traumatic brain swelling in head-injured patients

OBJECT

The pathogenesis of traumatic brain swelling remains unclear. The generally held view is that brain swelling is caused primarily by vascular engorgement and that edema plays a relatively minor role in the swelling process. The goal of this study was to examine the roles of cerebral blood volume (CBV) and edema in traumatic brain swelling.

METHODS

Both brain-tissue water and CBV were measured in 76 head-injured patients, and the relative contribution of edema and blood to total brain swelling was determined. Comparable measures of brain-tissue water were obtained in 30 healthy volunteers and CBV in seven volunteers. Brain edema was measured using magnetic resonance imaging, implementing a new technique for accurate measurement of total tissue water. Measurements of CBV in a subgroup of 31 head-injured patients were based on consecutive measures of cerebral blood flow (CBF) obtained using stable xenon and calculation of mean transit time by dynamic computerized tomography scanning after a rapid bolus injection of iodinated contrast material. The mean (+/- standard deviation) percentage of swelling due to water was 9.37+/-8.7%, whereas that due to blood was -0.8+/-1.32%.

CONCLUSIONS

The results of this study showed that brain edema is the major fluid component contributing to traumatic brain swelling. Moreover, CBV is reduced in proportion to CBF reduction following severe brain injury.

Intraventricular hemorrhage as a false localizing sign of a thoracolumbar arteriovenous malformation: case report

BACKGROUND

Spinal arteriovenous malformation (SAVM) is a relatively rare disease characterized by a high incidence of intramedullary and subarachnoid haemorrhage. When the hemorrhage is profuse and the SAVM is in the cervical region the symptoms (disturbance of consciousness, papilledema, cranial nerve palsies, and convulsions) may be so severe and rapid in their onset that they may be mistaken for intracranial hemorrhage. We report here on a patient with a SAVM at T10-12, which bled intracranially, mainly intraventricularly, and resulted first in respiratory arrest and unconsciousness.

CASE DESCRIPTION

The patient had been well until he was 28 years old when, during intercourse, he suffered a terrible headache and suddenly lost consciousness, with a transient respiratory arrest. He was also noted to have right hemiparesis. A computed tomography scan demonstrated intraventricular hemorrhage. After a 24-hour period of artificial ventilation the patient regained consciousness and the right arm paresis completely recovered, but a gradual worsening of the motor function of the left leg developed. Digital subtraction angiography did not demonstrate any intracranial source of bleeding, whereas spinal angiography revealed a SAVM located at the medullary cone, which was totally removed by surgery.

CONCLUSION

The case reported here raises several important issues. First, the advisability of spinal magnetic resonance imaging in the investigation of intraventricular (and subarachnoid) hemorrhage in patients with no demonstrable intracranial source. Secondly, the benefits of early diagnosis and reestablishment of the spinal cord circulation before the onset of thrombosis and the progressive phase of myelopathy. Finally, the necessity of complete obliteration and treatment of SAVMs even in patients with fixed neurologic deficits, because rebleeding of lower thoracic or lumbar SAVMs can lead to impairment at a higher level with severe or lethal consequences.

[Giant cell interstitial pneumonia]

GIP is a rarely occurring disorder. There is only few literature from its first description. Authors observed the course of GIP in the case of a 54 year old female patient in the form of bilateral disseminated microfocal pulmonary shadows, increased reticular outline with associated respiratory insufficiency. Open fine needle pulmonary biopsy proved giant cell desquamative alveolitis with help of light- and electronmicroscopical and histochemical examinations. Although possibility of exogenic, inhalative factor or/and infectious origin arose in causing the disease, disposition from the patient's actual immunological status could had helped the evolution of the disease. This fact seemed to be supported by the histologically proven associated dermatitis purpurica pigmentosa (Schamberg disease). With methylprednisolon therapy full radiological recovery occurred, while Schamberg disease was little influenced by the above mentioned therapy. The patient is pulmonologically symptom-free and without complaint after 1 year without any steroid-medication.

[Löfgren syndrome after silicone breast prosthesis implantation]

The authors review the case of a 30-year old female hair-dresser, into the breasts of whom silicone-gel implants have been implanted for cosmetic reasons. Ten months after the operation Löfgren-syndrome evolved, which improved only temporarily after the removal of the implants. The present symptom-free state, existing for 6 months now, required a 17-month corticoid therapy. The authors share the view that in rare cases silicon-gel implants might induce an autoimmune reaction, which is unforeseeable. When it is rightly presumed that human adjuvant disease or some other specified systemic disease is evolving, it is advisable that the implants should be removed and the patient should be treated with immunological therapy.

Biphasic pathophysiological response of vasogenic and cellular edema in traumatic brain swelling

The objective of this study was to quantify the temporal water content changes and document the type of edema (cellular versus vasogenic) that is occurring during both the acute and the late stages of edema development following closed head injury. Adult Sprague rats (n = 50) were separated into two groups: Group I: Sham (n = 8), Group II: Trauma (n = 42). The measurement of brain water content (BWC) was based on T1, whereas the differentiation of edema on the measurement of the random, translational motion of water protons (apparent diffusion coefficients-ADC) by MRI. In trauma animals, we found a significant increase in ADC (105%) as well as in BWC (0.7 +/- 0.3%) during the first 60 minutes post injury indicating vasogenic edema formation. This transient increase; however, was followed by a continuing decrease in ADC beginning at 45 minutes post injury and reaching a minimum at days 7-14 (-103%). Since the BWC continued to increase during the next day (10.3%), it is suggested cellular edema formation started to develop soon after injury and became dominant between 1-2 weeks post injury. In conclusion we may consider, that there is a predominantly vasogenic edema formation immediately after injury and later a more widespread and slower edema formation due to a predominantly cellular swelling.

Acute blood-brain barrier changes in experimental closed head injury as measured by MRI and Gd-DTPA

The objective of this study was to determine the early time course of blood-brain barrier (BBB) changes in diffuse closed head injury (CHI) and to what extent BBB is affected by secondary insult. The BBB disruption was quantified using T1-weighted MRI following administration of Gd-DTPA. The maximal signal intensity (SI) enhancement was used to calculate BBB disruption. A new CHI model was used to induce injury. Adult SD rats were separated into four groups: Group I: Sham (n = 4), II: Hypoxia and Hypotension (HH, n = 4), III: Trauma alone (n = 23), and IV: Trauma coupled with HH (THH, n = 14). Following trauma, a 30 minute insult of hypoxia (PaO2 = 40 mmHg) and hypotension (MABP = 30 mmHg) were imposed. In trauma animals, SI increased dramatically immediately following impact. By 15 minutes, permeability decreased exponentially and by 30 minutes was equal to that of control. In THH animals, SI enhancement was lower after the trauma, consistent with reduced blood pressure and blood flow. However, the SI increased dramatically upon reperfusion and was equal to that of control after 60 minutes. In conclusion we may consider, that CHI is associated with a rapid and transient BBB opening which begins at the time of the trauma and lasts not more than 30 minutes. It has been also shown that addition of hypoxia and hypotension prolongs the time of BBB breakdown.

MRI diffusion-weighted spectroscopy of reversible and irreversible ischemic injury following closed head injury

The objective of this study was to detect the threshold between reversible and irreversible secondary insult of hypoxia and hypotension following closed head injury as measured by MRI. Adult Sprague rats were separated into 3 groups: I: Sham (n = 6), II: Trauma and hypoxia coupled with mild hypotension of 40-50 mmHg (n = 6), III: Trauma and hypoxia coupled with severe hypotension of 30-40 mmHg (n = 6). The measurement of brain water content (BWC) was based on T1, whereas the differentiation between reversible and irreversible secondary insult on the measurement apparent diffusion coefficient (ADC). The ADCs in both trauma and secondary insult groups decreased rapidly from a control level of 0.68 +/- 0.5 x 10(-3) to significantly different minimum levels of 0.52 +/- 0.5 x 10(-3) in Group II and 0.42 +/- 0.5 x 10(-3) mm2/second in Group III at 30 minutes. In Group II rats there was a complete recovery in ADC as well as in their clinical conditions, whereas ADC in Group III rats remained at the minimum level and the animals were brain dead. The BWC was also significantly different at four hours post injury (Group II: 80.3 +/- 0.7%, Group III: 81.8 +/- 0.8%). The data lead the authors to suggest that the threshold between reversible and irreversible posttraumatic secondary insult is very narrow, and the measurement of ADC can provide information that will enable the clinician to identify critical threshold beyond which recovery is not possible.

Detection of brain atrophy following traumatic brain injury using gravimetric techniques

We hypothesized, that with atrophy, the correlation between water content and specific gravity of brain solids would break down signifying the onset of the atrophic process. The correlation between tissue water content, specific gravity of solids and ventricular size was studied in an impact acceleration model of closed head injury of the rat. Adult Sprague Dawley rats weighing 350 to 375 grams (n = 63) were separated into two groups: Group 1: Sham (n = 21), Group II: Trauma (n = 42). Water content was assessed using both gravimetric method and drying-weighing method at 1 hour, on days 1, 3, 7, 14, 28, and 42 in the trauma group as well as in the control group. Ventricular size was measured in cm2 on the MRI computer console in the coronal section at the coronal suture at the same time points. In the trauma group we found a significant increase (p < 0.01) in water content during the first week except on day 3 and there was a good correlation between the results of water content using both methods (p < 0.001). However, this relationship was poorly correlated after day 14 (p = 0.25). Although the ventricular size was the smallest at 1 hour post trauma, it significantly increased over the next 3 days (p < 0.001). On day 7 and 14 ventricular size decreased to normal size, yet gradually increased and then reached a significantly larger size on 42 days post trauma again (p < 0.01). We may consider, that brain edema following CHI begins immediately following trauma and resolves within 2 weeks. After 14 days degenerative change occurs in the cortex, as detected by specific gravity measurements which signifies the onset of the atrophic process and subsequent post traumatic ventricular dilatation.

Contribution of vasogenic and cellular edema to traumatic brain swelling measured by diffusion-weighted imaging

The contribution of brain edema to brain swelling in cases of traumatic brain injury remains a critical problem. The authors believe that cellular edema, the result of complex neurotoxic events, is the major contributor to brain swelling and that vasogenic edema, secondary to blood-brain barrier compromise, may be overemphasized. The objective of this study, therefore, was to quantify temporal water content changes and document the type of edema that forms during the acute and late stages of edema development following closed head injury (CHI). The measurement of brain water content was based on magnetic resonance imaging-determined values of tissue longitudinal relaxation time (T1-weighted imaging) and their subsequent conversion to percentage of water, whereas the differentiation of edema formation (cellular vs. vasogenic) was based on the measurement of the apparent diffusion coefficient (ADC) by diffusion-weighted imaging. A new impact-acceleration model was used to induce CHI. Thirty-six adult Sprague-Dawley rats were separated into two groups: Group I, control (six animals); and Group II, trauma (30 animals). Fast ADC measurements (localized, single-voxel) were obtained sequentially (every minute) up to 1 hour postinjury. The T1-weighted images, used for water content determination, and the diffusion-weighted images (ADC measurement with conventional diffusion-weighted imaging) were obtained at the end of the 1st hour postinjury and on Days 1, 3, 7, 14, 28, and 42 in animals from the trauma and control groups. In the animals subjected to trauma, the authors found a significant increase in ADC (10 +/- 5%) and brain water content (1.3 +/- 0.9%) during the first 60 minutes postinjury. This is consistent with an increase in the volume of extracellular fluid and vasogenic edema formation as a result of blood-brain barrier compromise. This transient increase, however, was followed by a continuing decrease in ADC that began 40 to 60 minutes postinjury and reached a minimum value on Days 7 to 14 (10 +/- 3% reduction). Because the water content of the brain continued to increase during the first 24 hours postinjury (1.9 +/- 0.9%), it is suggested that the decreased ADC indicated cellular edema formation, which started to develop soon after injury and became dominant between 1 and 2 weeks postinjury. The study provides supportive evidence that cellular edema is the major contributor to posttraumatic swelling in diffuse CHI and defines the onset and duration of the increase in cellular volume.

Magnetic resonance imaging-monitored acute blood-brain barrier changes in experimental traumatic brain injury

The authors posit that cellular edema is the major contributor to brain swelling in diffuse head injury and that the contribution of vasogenic edema may be overemphasized. The objective of this study was to determine the early time course of blood-brain barrier (BBB) changes in diffuse closed head injury and to what extent barrier permeability is affected by the secondary insults of hypoxia and hypotension. The BBB disruption was quantified and visualized using T1-weighted magnetic resonance (MR) imaging following intravenous administration of the MR contrast agent gadolinium-diethylenetriamine pentaacetic acid. To avoid the effect of blood volume changes, the maximum signal intensity (SI) enhancement was used to calculate the difference in BBB disruption. A new impact-acceleration model was used to induce closed head injury. Forty-five adult Sprague-Dawley rats were separated into four groups: Group I, sham operated (four animals), Group II, hypoxia and hypotension (four animals), Group III, trauma only (23 animals), and Group IV, trauma coupled with hypoxia and hypotension (14 animals). After trauma was induced, a 30-minute insult of hypoxia (PaO2 40 mm Hg) and hypotension (mean arterial blood pressure 30 mm Hg) was imposed, after which the animals were resuscitated. In the trauma-induced animals, the SI increased dramatically immediately after impact. By 15 minutes permeability decreased exponentially and by 30 minutes it was equal to that of control animals. When trauma was coupled with secondary insult, the SI enhancement was lower after the trauma, consistent with reduced blood pressure and blood flow. However, the SI increased dramatically on reperfusion and was equal to that of control by 60 minutes after the combined insult. In conclusion, the authors suggest that closed head injury is associated with a rapid and transient BBB opening that begins at the time of the trauma and lasts no more than 30 minutes. It has also been shown that addition of posttraumatic secondary insult-hypoxia and hypotension-prolongs the time of BBB breakdown after closed head injury. The authors further conclude that MR imaging is an excellent technique to follow (time resolution 1-1.5 minutes) the evolution of trauma-induced BBB damage noninvasively from as early as a few minutes up to hours or even longer after the trauma occurs.

[Cerebral blood flow studied by SPECT and transcranial Doppler sonography in subarachnoid hemorrhage]

The detection of vasospasm plays an important role for the definition of the strategy of treatment in patients with subarachnoid hemorrhage (SAH). Besides the invasive contrast angiography, the non-invasive 99m-Tc-HMPAO brain perfusion SPECT and transcranial Doppler sonography (TCD) are recently used for this purpose. For the investigation of the possibilities of the last two methods, comparative studies were performed in 29 SAH patients in the subacute phase of the disease. In the detection of regional brain ischaemia the sensitivity of the SPECT study was 90%, the specificity was 28% and the accuracy was 50%, the corresponding values of TCD were 82%, 71% and 75%. In patients, in whom chronic neurological symptoms, or morphological abnormalities could be excluded, the specificity of the SPECT study was 67% at unchanged sensitivity. Based on the results it is concluded, that the brain perfusion SPECT and the TCD investigation are useful methods for the detection of vasospasm after SAH. The combination of the two methods is recommended for the correct diagnosis of vasospasm in SAH. Further investigations are necessary to clarify the prognostic impact of the result of these investigations.

Use of transcranial Doppler sonography and acetazolamide test to demonstrate changes in cerebrovascular reserve capacity following carotid endarterectomy

OBJECTIVES

To assess the effect of carotid endarterectomy on cerebrovascular reserve capacity.

METHODS

Cerebral blood flow velocity (CBFV) and cerebrovascular reserve capacity (CVRC) were measured by transcranial Doppler sonography (TCD) and acetazolamide test in 40 patients who underwent uncomplicated unilateral carotid endarterectomy (CEA). Indication for operation was limited to stenoses > 70% as documented by angiography and/or Duplex scanning. The TCD studies were carried out 6 days (range 1-14 days) before and 8 days (range 5-12 days) after endarterectomy.

RESULTS

Before endarterectomy, resting CBFV values and CVRC in the 40 patients were significantly different between the operated (51 +/- 19 cm/s; 20 +/- 16%) and the non-operated (60 +/- 19 cm/s; 34 +/- 24%) hemisphere (p < 0.05;p < 0.01). After CEA the overall increase of resting CBFV of the operated side was highly significant with preoperative CBFV values of 51 +/- 19cm/s and postoperative values of 62 +/- 15 cm/s (p < 0.01). Cerebrovascular reserve capacity after operation was increased on both sides significantly (non-operated side: from 34 +/- 24% to 43 +/- 19%, p < 0.05; operated side: from 20 +/- 16% to 51 +/- 18%, p < 0.001), and the preoperative asymmetry was no longer present.

CONCLUSIONS

CEA has a beneficial effect on the cerebral circulation in most patients, even those who presented with asymptomatic carotid artery stenosis. Since CVRC has been assessed in the early postoperative period, our findings also suggest that cerebral vascular adaption occurs within 2 weeks after CEA.