Noninvasive detection of the distinction between progressive and compensated hydrocephalus in infants: is it possible?

OBJECT: Clinical signs and symptoms of hydrocephalus can be clear and specific, but also subtle, nonspecific, or even absent. It may be difficult to decide whether shunt placement is indicated, especially in infants. Therefore, there is a need for the development of better noninvasive detection methods to distinguish between compensated and (slowly) progressive hydrocephalus. Early interference can reverse the cerebral damage, whereas the detection of a nonpathological state in infants with compensated hydrocephalus avoids the complications of unnecessary shunt procedures. Using MR imaging, the authors investigated cerebral blood flow (CBF) and apparent diffusion coefficients (ADCs) measured in infants with clinically compensated hydrocephalus. METHODS: The diagnosis of compensated hydrocephalus was made on the basis of clinical criteria, consisting of no signs or symptoms of increased intracranial pressure (ICP), measurement of a normal ICP, and standard MR imaging showing enlarged ventricles. Flow measurements through both internal carotid arteries and the basilar artery were considered to represent the total CBF. In addition, ADC values were assessed in 5 different regions of interest in the brain parenchyma using diffusion weighted imaging. Brain volumetric measurement was performed to express CBF in ml/100 cm(3) brain/min, thus compensating for physiological CBF growth over time. Mean arterial blood pressure was manually measured to exclude this factor as a cause of a possible change in CBF. Intracranial pressure measurement was performed noninvasively using the Rotterdam Teletransducer. RESULTS: Eighteen infants with clinically compensated hydrocephalus were included. The mean CBF was 53.5 ml/100 cm(3) of brain/min. The individual CBF values were graphically compared with age-related normal CBF values and fell in the normal range. Mean ADC value was 890.0 x10(-6) mm(2)/sec. Apparent diffusion coefficient values per region of interest were graphically compared with normal ADC values per region of interest and fell within the normal range. CONCLUSIONS: In infants with hydrocephalus, normal CBF and low ADC values, as measured using MR imaging, are associated with compensated hydrocephalus and may support a conservative approach with respect to the decision on whether to place a shunt.

New transcranial Doppler index in infants with hydrocephalus: transsystolic time in clinical practice.

Raised intracranial pressure (ICP) in infants with hydrocephalus may cause (ir)reversible damage to the brain parenchyma but can be present without clinical signs and/or symptoms. Therefore, new, favorably noninvasive, detection methods are needed to distinguish between compensated hydrocephalus with normal intracranial pressure and slowly progressive hydrocephalus with increased intracranial pressure. Because early ischemic changes in the brain parenchyma are associated with increased intracranial pressure, transcranial Doppler (TCD) indices may be useful to detect increased intracranial pressure in infants with hydrocephalus. Twenty-four infants with hydrocephalus underwent noninvasive ICP measurement, magnetic resonance imaging and TCD before and after cerebrospinal fluid (CSF) diversion. The TCD indices were paired to the anterior fontanelle pressure findings and compared for correlation. After CSF diversion, ICP decreased significantly from 21.8 cm H(2)O to 7.7 cm H(2)O (p<0.005). The transsystolic time (TST) as measured with TCD increased significantly from 176 to 221 ms (p<0.005), whereas the pulsatility index (PI) decreased significantly from 1.3 to 1.0 (p<0.05). The resistance index (RI) decreased significantly from 0.73 to 0.63 (p<0.05). Mean bloodflow velocity through the middle cerebral artery increased significantly from 55.5 to 75.8 cm/s (p<0.005). TST has a strong correlation with the ICP (p<0.005). Measuring TST with TCD can be helpful in the decision-making process about whether to perform CSF diversion in infants with hydrocephalus. Because TST is related solely to the relative changes in the flow velocity caused by intracranial physical properties, it has a closer relation to ICP than the PI and the RI.

Longitudinal diffusion-weighted imaging in infants with hydrocephalus: decrease in tissue water diffusion after cerebrospinal fluid diversion.

OBJECT: Progressive hydrocephalus may lead to edema of the periventricular white matter and to damage of the brain parenchyma because of compression, stretching, and ischemia. The aim of the present study was to investigate whether cerebral edema can be quantified using diffusion-weighted imaging in infants with hydrocephalus and whether CSF diversion could decrease cerebral edema. METHODS: Diffusion-weighted MR imaging was performed in 24 infants with progressive hydrocephalus before and after CSF diversion. Parametric images of the trace apparent diffusion coefficients (ADCs) were obtained. The ADCs of 5 different cortical and subcortical regions of interest were calculated pre- and postoperatively in each patient. The ADC values were compared with age-related normal values. Mean arterial blood pressure and anterior fontanel pressure were measured immediately after each MR imaging study. RESULTS: After CSF diversion, the mean ADC decreased from a preoperative value of 1209 +/- 116 x 10(-6) mm(2)/second to a postoperative value of 928 +/- 64 x 10(-6) mm(2)/second (p < 0.005). Differences between pre- and postoperative ADC values were most prominent in the periventricular white matter, supporting the existence of preoperative periventricular edema. Compared with age-related normal values, the preoperative ADC values were higher and the postoperative ADC values were lower, although within normal range. The decrease in ADC after CSF drainage was more rapid than the more gradual physiological decrease that is related to age. The preoperative ICP was elevated in all patients. After CSF diversion the ICP decreased significantly to within the normal range. A linear correlation between ADC values and ICP was found (correlation coefficient 0.496, p < 0.001). In all patients the mean arterial blood pressure was within physiological limits both pre- and postoperatively. CONCLUSIONS: This study shows a rapid and more extensive decrease in ADC values after CSF diversion than is to be expected from physiological ADC decrease solely due to increasing patient age. The preoperative ADC increase can be explained by interstitial edema caused by transependymal CSF leakage or by vasogenic edema caused by capillary compression and stretching of the brain parenchyma. This study population of infants with (early recognized) hydrocephalus did not suffer from cytotoxic edema. These findings may help to detect patients at risk for cerebral damage by differentiating between progressive and compensated hydrocephalus.

Magnetic resonance imaging for quantitative flow measurement in infants with hydrocephalus: a prospective study.

OBJECT: Raised intracranial pressure (ICP) that is associated with hydrocephalus may lead to alterations in cerebral hemodynamics and ischemic changes in the brain. In infants with hydrocephalus, defining the right moment for surgical intervention based on clinical signs alone can sometimes be a difficult task. Clinical signs of raised ICP are known to be unreliable and sometimes even misleading. Furthermore, when sutures are closed, ICP does not always correlate with the size of the ventricles or with the clinical signs or symptoms. In this study the authors investigated whether cerebral blood flow (CBF) can be measured by using quantitative MR angiography in infants with progressive hydrocephalus. In addition, the authors investigated the relationship between CBF and ICP, before and after cerebrospinal fluid (CSF) diversion. METHODS: Fifteen infants with progressive hydrocephalus (age range 1 day-7 months) were examined. All patients underwent anterior fontanel pressure measurement, MR angiography, and mean arterial blood pressure measurements before and after CSF diversion. Brain volume was measured to compensate for the physiological increase in CBF during brain maturation in infants. RESULTS: The mean preoperative ICP was 19.1 +/- 8.4 cm H(2)O (+/- standard deviation). The mean postoperative ICP was 6.7 +/- 4.0 cm H(2)O (p < 0.005). The mean preoperative CBF was 25.7 +/- 11.3 ml/100 cm(3) brain/min. After CSF diversion, CBF increased to 50.1 +/- 12.1 ml/100 cm(3) brain/min (p < 0.005). The mean arterial blood pressure did not change after surgical intervention. CONCLUSIONS: Magnetic resonance imaging can be used to measure CBF in infants with hydrocephalus. Raised ICP was related to a decrease in CBF. After CSF diversion, CBF and ICP improved to values within the normal range.