The authors evaluate the usefulness of transcranial Doppler (TCD) examination in Intracranial hypertension and brain death, on the basis of an experiment using a feline intracranial hypertension model and, on clinical studies.
The vanishing end-diastolic pattern of TCD is believed to show the critical point of intracranial hypertension. Experimentally, the vanishing end-diastolic pattern was observed at a cerebral perfusion pressure of approximately 50mmHg, accompanied by severe suppression in electroencephalography. In severe head injury patients, the absence of end-diastolic flow in TCD gives a forewarning of a potential fatal prognosis.
In eleven brain death cases, which satisfied the criteria of Japanese Health and Welfare Ministry's committee, TCD examination demonstrated one of the classical patterns of virtual cessation of cerebral blood flow (zero, systolic spike, or to and fro) with a sensitivity response of 91%. Doppler signals from the superficial temporal artery and internal maxillary artery, which resemble signals of the middle cerebral artery, must be differentiated, in order to avoid the danger of misinterpretation.

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We assessed the hemodynamic changes of AVM by calculating the blood flow (BF) of the middle cerebral artery (MCA) and the common carotid artery (CCA) in 16 supratentorial arteriovenous malformations (AVMs) and 7 in controls. Flow velocity (FV) was measured by transcranial Doppler sonography (TCD) and the diameter of the artery (R) was measured from the carotid angiography. The blood flow (BF) in MCA and CCA was calculated from the equation FV×πR². Sequential changes of blood flow volume and flow velocity were evaluated before operation and after surgery in 6 patients. FV and BF of MCA were increased proportionally to the size of AVM, but BF of MCA showed greater increase than flow velocity, especialy in large AVMs, because the feeding artery of MCA was still dilated after excision of AVM. FV and BF of CCA showed the same tendency, but their increase was much less than that of MCA. In large AVMs, FV of MCA was increased 7 times and FV of CCA, 3 times as much as the controls. From the above findings, it may be concluded that the measurement of BF in the feeding artery can give more information on the hemodynamic changes in AVM than FV.

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Is it possible for the estimation of MCA flow velosity (FV) and regional cerebral blood flow to predic delayed Ischemic Neuronal Deficits (DIND) following ruputured cerebral aneurysm?
This series consists of 41 patients with ruptured cerebral aneurysms who received emergency operations within 48 hours after onset. 26 rCBF measurements were performed and 16 were carried out within 7days after onset. TCD was measured everyday until 25th day after onset. All patients had CT scan, cerebral angiogram and neurological assessment upon admission. To clarify morphological changes of cerebral vessels due to sabarachnoid hemorrhage, the second angiogram was performed about lOdays after operation.
Results : DIND appeared when mean rCBF decreased below 50 ml/100gbrain/min. There was no correlation between mean rCBF within 7days after onset and Hunt-Kosnik grade on admission, however, there was a good correlation of mean rCBF and CT classification on admission.
15 patients with DIND had a rapid increase of FV from the 3rd to 5th day after onset and continued high flow velosity more than 150cm/s during 6days on average after rapid increase of FV. On the other hand, 26 patients without DIND showed only small increase of FV, less than 11Ocm/s There was a correlation between % changesof FV increase during 3rd to 5th days and morphological types of cerebral vasospasm. More than 30 % FV increase were maintained 2days in the patients with diffuse severe-type spasm.
There was a good relationship between mean rCBF and FV of MCA, and also MCA diameter (ratio of vasospasm) and MCAFV.
Conclusion : The prediction of DIND could be done 51 % on CT findings of admission and 88 % on serial measurements of MACFV.) The predictability of the rCBF value was not dependent on the reversibility of the vasospasm symptons.

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Capability and limitation of transcranial Doppler (TCD) in assessing cerebral collateral flow were evaluated in 25 patients. Changes in velocities and flow directions in basal cerebral arteries were assessed with compressive maneuvers of the common carotid artery and plotted on the three dimensional zero-float computer graphic display. Preoperative TCD examinations were combined with angiographic examinations. 16 of the 25 patients who required temporary or permanent occlusion of the internal carotid artery for treatment of their cerebrovascular and neoplastic lesions were evaluated for the feasibility of carotid clamp or ligation. In 13 of the 16 patients whose neurological function and intracranial vessel flow velocities were maintained adequately, temporary or permanent ligation of the carotid artery could safely be undertaken. In 3 of the 16 patients whose flow velocities decreased to zero, EC-IC bypass was performed prior to the carotid occlusion. TCD findings demonstrated angiographic findings of cross-filling. Collateral capacities of the extracranial-intracranial bypass were examined in the remgining 9 of the 25 patients including 6 patients who underwent vein graft (VG) bypass and 3 patients who underwent STA-MCA anastomosis. Bypass compression tests demonstrated the degree of contribution of the bypass to the cerebral circulation, with the VG bypass surpassing the efficiency of the STA-MCA bypass. In conclusion, TCD provides a better understanding of the hemodynamics of circulation in the brain prior to surgery for cerebrovascular and neoplastic diseases.

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The measurement of cerebrovascular CO₂ reactivity is very important to assess the pathophysiology of cerebrovascular disease. However, the conventional methods for measurement of CO₂ reactivity are invasive and need radioisotope or other tracers. Transcranial Doppler (TCD) is a new method to evaluate the mean flow velocity of the middle cerebral artery (MCA) non-invasively. Cerebral blood flow (CBF) and MCA flow velocity have been measured simultaneously using laser Doppler and TCD, respectively in our department. This study showed changes of CBF measured by laser Doppler and velocity measured by TCD relatively. Therefore, the vasodilatory capacity to increase in PaCO₂ can be tested by measurement of MCA flow velocity using TCD. The elevation of end-tidal PCO₂ was achieved by re-breathing the alr expired air from a respiratory bag. The CO₂ reactivity was easily calculated by a personal computer using en equation obtained from the mean flow velocoty and end-tidal PCO₂ within a range of 3060 mmHg. We have studied the CO₂ reactivity in patients suffering from rarious neurosurgical diseases. The reduction of CO₂ reactivity was detected in patients with symptomatic vasospasm, normal pressure hydrocephalus, cerebral infarction, Moyamoya disease and chronic subdural hematoma.

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In three patients with ectatic disorders of vertebrobasilar systems, intracranial hemodynamics was investigated by Transcranial Doppler (TCD) . On measurements by TCD, combined midline and lateral approach were used for accurate evaluation of the circulation system.
In two patients with dolichoectasia, flow velocities (FVs) of the basilar and bilateral vertebral arteries were low, but pulsatility indicies (PIs) were in normal range. ¹²³I IMP SPECT of the patients revealed normal regional CBF of the posterior circulation.
In the other patient with vertebrobasilar ectasia due to agenesis of bilateral internal carotid arteries, FVs and PIs of the basilar and bilateral vertebral arteries were almost normal. ¹²³I IMP SPECT of the patient revealed normal CBF of both of anterior and posterior circulation. The difference of blood flow of the basilar and vertebral arteries between the two ectatic disorders demonstrated the difference of FVs between the two patients.

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It is generally believed that TCD is not helpful in detecting intracranial aneurysms smaller than 15mm in diameter, to despite great improvement in technology of transcranial Doppler (TCD) in transcranial Doppler angiography (TCDA), three dimentional transcranial Doppler (3D-TCD) and transcranial color flow image (TCFI) . So far there haven't been any reports to challenge this theory. In this study, we examined a 50-yearold female with diffuse subarachnoid hemorrhage. We were able to detect four aneurysms in this patient. The size of aneurysms ranged from 2mm to 9mm in diameter using TCFI under the following criteria before cerebral angiography. We conducted the experiment as follow:
1) Set up sample volume from 1.5 × 1.0mm to 3.0 × 1.0mm.
2) Carefully scanned the captured artery.
3) Detected an appendage structure with pathological blood flow near the normal cerebral artery using axial and coronal view in B-mode scan.
4) Detected a pathlogical color-flow image with Doppler sonogram, which indicates a turbulent flow.
5) Found normal flow pattern at the proximal and distal portions of the turbulent flow region.
This is the first report showing the turbulent flow of small cerebral aneurysms using B-mode scan and Doppler son ogram.
We believe that our report indicates the reliability of TCFI for screening unruptured cerebral aneurysms.

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