J. Willemse

The effect of intracranial pressure on myelination and the relationship with neurodevelopment in infantile hydrocephalus

The effect of raised intracranial pressure (ICP), due to infantile hydrocephalus, on the process of myelination has been suggested in the literature. In this study 19 hydrocephalic infants were followed‐up with anterior fontanelle pressure (AFP) measurement (assessment of ICP), MRI (assessment of the myelination process and the CSF volume), and neurodevelopmental testing (NDT). There was a high correlation (r=0.80) between the myelination and NDT scores. The size of the CSF volume showed a poor correlation with the mean AFP, the degree of myelination and the NDT scores. There was, however, a significant correlation between the mean AFP and the degree of myelination (r=0.67) and also between the mean AFP and the NDT scores (r=0.70). Longer‐term follow‐up (mean=27 months) showed a significant correlation between the early progress of myelination and later developmental level (r=0.78). Most of the children with a severely delayed myelination, preoperatively, showed a recovery of myelination following CSF drainage. It was concluded that: (1) raised ICP is related to developmental outcome, through the process of myelination; (2) the delay in myelination can be (partially) reversible; and (3) CSF volume is of minor importance regarding neurodevelopment.

Visuomotor performance of normal and clumsy children. I: Fast goal-directed arm-movements with and without visual feedback.

The mechanisms underlying accuracy in fast goal‐directed arm‐movements were investigated in normal and clumsy children in two age‐groups, six to seven and 10 to 11 years. Clumsy children in both age‐groups had a longer movement time than normal children; this difference increased slightly when there was visual feedback. For both normal and clumsy children, the relative variability of the total distance moved was smaller than that of the distance moved during acceleration, indicating a variability reduction mechanism in the course of a movement. In the six‐ to seven‐year‐old group, the relative variability of the distance moved during acceleration and of the total distance was larger for clumsy than for normal children; this did not reach significance in the 10‐ to 11‐year‐old group. It is suggested that motor difficulties are linked to inaccuracy in open‐loop control processes and to less efficient use of visual feedback.

VISUOMOTOR PERFORMANCE OF NORMAL AND CLUMSY CHILDREN. II: ARM-TRACKING WITH AND WITHOUT VISUAL FEEDBACK

Tracking performance was investigated in normal and clumsy children in two age‐groups, six to seven and 10 to 11 years. Target signals moving unpredictably along a straight line had to be tracked, both with and without visual feedback. Performance was described in three ways: (1) performance in the low‐frequency range (LF); (2) the delay between target signal and tracking movement (DL); and (3) a measure of tracking quality or over‐all similarity in the shape of target signal and tracking movement (Q). Clumsy children in both age‐groups had a lower tracking quality (Q) and longer delay (DL) than the normal children. Disturbances in the regulation of attention seemed to affect tracking performance, particularly of the six‐ to seven‐year‐old clumsy children. There was no significant difference between normal and clumsy children in the effect of visual feedback on tracking performance. This suggests that clumsiness is not linked to disturbance of integration of visual feedback information and motor processes.

Value of transcranial Doppler indices in predicting raised ICP in infantile hydrocephalus

Cerebral hemodynamic changes in infants with progressive hydrocephalus have been studied with the transcranial Doppler (TCD) technique. Several authors have referred to the correlation between the hemodynamic changes and increased intracranial pressure (ICP). Despite conflicting conclusions on the value of pulsatility index (PI) measurements for monitoring infantile hydrocephalus, these pulsatility indices are the most commonly used for this purpose. Although clinical signs of raised ICP are highly variable and unreliable in infants, assumptions have been made in most of the studies about the presence of elevated ICP on the basis of the patients clinical state. Few studies have reported on actual ICP values, however, and a direct relationship between ICP and TCD changes has never been adequately demonstrated. In the present study, this relationship was investigated in long-term simultaneous TCD/ICP measurements, in an attempt to develop a noninvasive method of monitoring the effect of ICP on intracranial hemodynamics. Two groups of data sets were established. Group I consisted of pre- and postoperative (shunt implantation) TCD/ICP measurements. Group II were long-term simultaneous TCD/ICP recordings showing significant ICP variations. In most of the postoperative measurements there was a decrease in the average PI and RI values. The correlation between PI or RI and ICP in the long-term simultaneous recordings, however, was generally poor. The risk of obtaining false positive or false negative PI or RI values in short-term measurements was also demonstrated. It can be concluded from our results, besides the wide range of reference values for the Doppler indices and extracranial influences upon them, that the present Doppler indices are inadequate for monitoring the complex intracranial dynamic responses in patients with raised ICP.

Ischaemic stroke in the basal ganglia and internal capsule in childhood

Ischaemic stroke in childhood is rare. In particular, there have only been a few reports of lacunar infarcts in children. In this study, four children with true lacunar infarcts and four with larger subcortical infarcts are described. We compare the clinical features and the possible pathogenesis of ischaemic strokes in the basal ganglia and internal capsule in childhood with those in adults, and discuss diagnostic and therapeutic management.

Treatment of intact familial intracranial aneurysms: a decision-analytical approach

Clinical decision analysis is applied to the treatment decisions for four patients with unruptured familial aneurysms. The surgical treatment was uneventful in all patients except one with mild mixed aphasia and facial weakness postoperatively; these deficits disappeared in less than 2 years. In the decision analysis, discounted Quality Adjusted Life Years are used as an outcome measure. Probability estimates are extracted from the literature when available. It is concluded that the decision to treat the aneurysm neurosurgically in three of the four patients was correct. In two of these three patients, the decision cannot be altered by plausible changes in estimated data. For the third patient, only the combination of a low probability of rupture, a high surgical mortality and morbidity, and high discount favors conservative treatment. In the fourth patient, a toss-up situation exists. More knowledge of the probability of rupture, the probability of the development of other aneurysms, and the results of operation on intact intracranial aneurysms would have made the analysis more accurate. Clinical research should address these issues.

INTRACRANIAL SPACES IN CHILDHOOD MACROCEPHALY: COMPARISON OF LENGTH MEASUREMENTS AND VOLUME CALCULATIONS

CT scanning was done to calculate the volume of intracranial spaces in children with the purpose of developing a reliable method of differentiating the various causes of macrocephaly. The technique has been applied to the CT scans of 60 apparently normal children, and the resulting graphs show the normal relationship between intracranial volumes and age from birth to 15 years. The measurements for 25 children with macrocephaly and normal rate of growth of head circumference were then compared with the reference values. It was possible to make accurate differentiations between megalencephaly, extraventricular hydrocephalus and communicating hydrocephalus. The advantage of this technique in relation to length measurements on CT scans is discussed. The authors advocate the estimation of the product of head circumference and head height as a much more reliable indication of normal and deviant head‐size than head circumference alone.

Megalencephaly: definition and classification.

The various definitions and classifications of megalencephaly are reviewed, and numerous diseases and syndromes associated with megalencephaly are listed. A new definition of megalencephaly based on quantitative radiographic features is proposed. We define megalencephaly as a brain volume which exceeds the mean by more than twice the standard deviation. Furthermore, a modified etiopathogenic classification of megalencephaly results in three main groups, viz anatomic, metabolic and dynamic megalencephaly. The clinical pictures in these main groups of megalencephaly, and the largest subgroup of anatomic megalencephaly, familial anatomic megalencephaly, appear to be quite different.

Monitoring intracranial dynamics by transcranial Doppler—a new Doppler index: Trans systolic time

Since the introduction of transcranial Doppler sonography (TCD) several investigators have described the relationship between raised intracranial pressure (ICP) and Doppler waveform. This waveform has been expressed by several indices, such as the pulsatility index (PI) and the resistance index (RI). These indices are used to demonstrate the presence of raised ICP. In childhood hydrocephalus this information can be used to indicate the need for shunt implantation. However, PI and RI do prove to have certain disadvantages as both are strongly influenced by the heart rate. Moreover, both indices have a broad range of reference values, especially in children. Therefore, they are not very reliable for detecting insidious changes in the ICP. These drawbacks are due to the fact that these indices are composed of blood flow velocity measurements and do not embody the slope of the TCD waveform itself. An ideal TCD waveform analysis should be performed concerning the time-related changes of the velocities. We present a hydrodynamic model, with its electrical analogue, which shows the effects of raised ICP on the intracranial hemodynamic system. Based on these physical findings we define a new Doppler index, the Trans Systolic Time, reflecting specific changes in the TCD waveform induced by changes in the mean ICP. The applicability of this index, compared with PI and RI, is illustrated by consecutive simultaneous TCD and AFP measurements in three children with hydrocephalus.

Unruptured intracranial arteriovenous malformations with hereditary haemorrhagic telangiectasia. Neurosurgical treatment or not

SummaryClinical decision analysis is applied to treatment decisions for three patients with unruptured familial intracranial arteriovenous malformations (AVMs) in association with hereditary haemorrhagic telangiectasia (HHT). The grades of the AVMs—according to Spetzler—were 1-0-0 (two patients aged 12 and 14) and 2-0-1 (one patient aged 43). The AVM in one patient (graded 1-0-0) was operated on without sequelae. In the decision analysis, life expectancy is used as an outcome measure, with and without quality of life adjustment and discounting for time preference. It is concluded that neurosurgical treatment is the optimal strategy for all three patients.Because no conclusive data are available concerning the natural history and neurosurgical treatment of unruptured AVMs, we recommend the prospective application and testing of AVM grading systems. General treatment guidelines balancing the lifetime risk of haemorrhage, risk of incomplete extirpation and surgical mortality and morbidity are given. The analysis suggests that patients with low-graded AVMs which have not bled should be treated surgically, unless they are older than 60 years and have an increased risk of incomplete extirpation.