Takumi Moriyama

Intracranial haemodynamics in diffuse and focal brain injuries. Evaluation with transcranial Doppler (TCD) ultrasound

SummaryIntracranial haemodynamics were studied in 20 patients with diffuse and focal brain injury and experimental animals with acute intracranial hypertension by the use of TCD ultrasound. The mean flow velocity in the middle cerebral artery (MCA) commonly decreased on the side of the haematoma depending on intracranial pressure (ICP) elevation and cerebral perfusion pressure (CPP) reduction in focal injury. The decrease of the MCA flow velocity returned to normal after treatment. The flow velocities decreased bilaterally and there was no difference between the right and left side in diffuse injury. But the velocities increased in spite of ICP elevation when diffuse cerebral swelling developed. Cerebrovascular CO2 reactivity was impaired in two groups of patients with low Glasgow Coma Scale (GCS) scores. The mean velocity of the MCA and blood flow in the internal carotid artery exhibited flow patterns which changed correlatively depending on CPP reduction in experimental animals. Noninvasive study by use of TCD ultrasound can provide valuable information on variant haemodynamic phenomena in patients with diffuse and focal brain injury.

Noninvasive study of critical thresholds of Intracranial pressure and cerebral perfusion pressure for cerebral circulation and brain function

To ascertain the critical thresholds of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) for cerebral circulation and brain function, the extra- and intracranial haemodynamics and electrical brain responses were evaluated noninvasively with Doppler ultrasonography and multimodality evoked potentials (MEPs) in 50 patients with severe head injury. Both extra- and intracranial blood flow velocities changed monotonically depending on the changes in ICP and CPP. They were decreased when ICP increased to 20-30 mmHg and when CPP decreased to 40-50 mmHg. The changes in elasticity index of the pulse wave of the common carotid artery was proportional to those of blood flow velocities. The frequency and degree of abnormalities of MEPs were proportionally increased with the rise of ICP and reduction of CPP. When ICP increased to higher than 31 mmHg, MEPs were classified as moderately or severely abnormal in more than 76% of the recordings. These results indicate that noninvasive study by use of Doppler ultrasonography and MEPs can provide valuable information on critical brain ischaemia and brain dysfunction in patients with acute intracranial hypertension.

Critical Thresholds of ICP and Cerebral Perfusion Pressure (CPP) for Cerebral Blood Flow and Brain Functions — Noninvasive Study

Neuronal damage in intracranial hypertension is closely related to brain ischemia, and therefore, the critical thresholds of ICP and CPP (cerebral perfusion pressure) for cerebral circulatory disturbance and brain dysfunction have important clinical significance. To ascertain these thresholds, extra- and intracranial hemodynamic phenomena and brain function were studied noninvasively in intracranial hypertension.

Evaluation of Medical Management for Severe Head Injury

Barbiturates, hyperosmotic agents, hyperventilation and head elevation have been widely used for the control of ICP in patients with severe head injury. But controversies still exist on the efficacy and limitation of these managements. In the present study, these medical managements were evaluated by analyzing their effects on ICP, cerebral perfusion pressure (CPP), and blood flow velocity in the middle cerebral artery (MCAFV).