Intracranial spaces in childhood macrocephaly: comparison of length measurements and volume calculations

Imaging in the study of macrocephaly: Why?, when?, how?

Macrocephaly is a clinical term defined as an occipitofrontal circumference more than two standard deviations above the mean. It is present in 5% of children and is a common indication for imaging studies. There are multiple causes of macrocephaly; most of them are benign. Nevertheless, in some cases, macrocephaly is the clinical manifestation of a condition that requires timely medical and/or surgical treatment. The importance of imaging studies lies in identifying the patients who would benefit from treatment. Children with macrocephaly associated with neurologic alterations, neurocutaneous stigmata, delayed development, or rapid increase of the circumference have a greater risk of having disease. By contrast, parental macrocephaly is predictive of a benign condition. Limiting imaging studies to patients with increased risk makes it possible to optimize resources and reduce unnecessary exposure to tests.

The test characteristics of head circumference measurements for pathology associated with head enlargement: a retrospective cohort study

Background

The test characteristics of head circumference (HC) measurement percentile criteria for the identification of previously undetected pathology associated with head enlargement in primary care are unknown.

Methods

Electronic patient records were reviewed to identify children age 3 days to 3 years with new diagnoses of intracranial expansive conditions (IEC) and metabolic and genetic conditions associated with macrocephaly (MGCM). We tested the following HC percentile threshold criteria: ever above the 95^th, 97^th, or 99.6^th percentile and ever crossing 2, 4, or 6 increasing major percentile lines. The Centers for Disease Control and World Health Organization growth curves were used, as well as the primary care network (PCN) curves previously derived from this cohort.

Results

Among 74,428 subjects, 85 (0.11%) had a new diagnosis of IEC (n = 56) or MGCM (n = 29), and between these 2 groups, 24 received intervention. The 99.6^th percentile of the PCN curve was the only threshold with a PPV over 1% (PPV 1.8%); the sensitivity of this threshold was only 15%. Test characteristics for the 95th percentiles were: sensitivity (CDC: 46%; WHO: 55%; PCN: 40%), positive predictive value (PPV: CDC: 0.3%; WHO: 0.3%; PCN: 0.4%), and likelihood ratios positive (LR+: CDC: 2.8; WHO: 2.2; PCN: 3.9). Test characteristics for the 97th percentiles were: sensitivity (CDC: 40%; WHO: 48%; PCN: 34%), PPV (CDC: 0.4%; WHO: 0.3%; PCN: 0.6%), and LR+ (CDC: 3.6; WHO: 2.7; PCN: 5.6). Test characteristics for crossing 2 increasing major percentile lines were: sensitivity (CDC: 60%; WHO: 40%; PCN: 31%), PPV (CDC: 0.2%; WHO: 0.1%; PCN: 0.2%), and LR+ (CDC: 1.3; WHO: 1.1; PCN: 1.5).

Conclusions

Commonly used HC percentile thresholds had low sensitivity and low positive predictive value for diagnosing new pathology associated with head enlargement in children in a primary care network.

MRI, volumetry,1H spectroscopy, and cerebropetal blood flowmetry in childhood idiopathic anatomic megalencephaly

PURPOSE

To evaluate cerebral abnormalities in childhood idiopathic anatomic megalencephaly (MC) by means of different magnetic resonance (MR) modalities.

MATERIALS AND METHODS

MRI, volumetry, spectroscopy, and cerebropetal blood flowmetry were performed in six children with idiopathic anatomic MC, and seven volunteers.

RESULTS

MRI revealed an increased ventricular system in five of six patients. A thalamic hamartoma was found in one patient and a Chiari I malformation was found in two. Volumetric analysis showed a disproportional increase of ventricular volume but normal subarachnoid cerebrospinal fluid (CSF) volume. Supratentorial volume was disproportionally increased compared to cerebellar volume. Intracranial volume correlated significantly with skull circumference. MR spectroscopy (MRS) N-acetyl aspartate/choline (NAA/Cho) peak ratios in WM were significantly higher in patients than in controls. Choline/creatine (Cho/Cr) peak ratios in WM were significantly lower in patients. Cortical gray matter (GM) MRS ratios were unaltered. Cerebropetal flow was increased in MC, possibly related to increased brain volume.

CONCLUSION

This study reveals associated developmental anomalies for idiopathic anatomic MC. A relative ventriculomegaly was found, which should not be misinterpreted as true hydrocephalus. In contrast to metabolic MC, MRS showed no severe disturbances. Total intracranial volume is correlated to skull circumference and cerebropetal blood flow.

Quantitative analysis of cerebrospinal fluid spaces in children with occipital plagiocephaly

The etiology of occipital plagiocephaly (OP) is not fully understood. The authors have observed that many infants with this condition have external hydrocephalus. This study was undertaken to quantify cerebrospinal fluid (CSF) space caliber in children with OP and to compare these measurements to those derived from normal age-matched controls to further elucidate the pathogenesis of this condition. Thirty-one infants with isolated unilateral OP (mean age 6 months) were studied. Infants with multiple cranial suture abnormalities, impaired neurological function, developmental delay, and associated craniofacial anomalies were excluded. Twenty normal infants were evaluated as controls. The volumes of the sylvian fissures, frontal and occipital subarachnoid spaces, as well as the cross-sectional areas of the suprasellar and perimesencephalic cisterns, were calculated from computerized tomography (CT) studies. Ventricular size was also assessed. Generalized subarachnoid space dilation was observed in 29 (93.5%) of the 31 children with OP. Head circumference was significantly greater in the case group (71.4 vs. 50.8 percentile; p = 0.0002 by analysis of variance). The sylvian fissure volume was significantly larger in the case group (5.8 ml vs. 0.7 ml in controls, p < 0.0001). The volume of the contralateral sylvian fissure was greater than that ipsilateral to the side of OP (7.1 ml vs. 4.5 ml, p = 0.001). Frontal subarachnoid space volume was greater in infants with OP (27.5 ml vs. 0.6 ml in controls, p < 0.0001). Both the suprasellar and perimesencephalic cisterns were of greater caliber in the case group (p = 0.007 and p < 0.0001, respectively). No difference in ventricular size or occipital subarachnoid space volume was noted between groups. The extraventricular CSF spaces in neurologically unimpaired infants with OP are significantly larger than those in age- and sex-matched controls. Enlarged subarachnoid spaces may increase the compliance and malleability of the calvaria and sutures, predisposing to positional deformity. External hydrocephalus may be a fundamental etiological factor in OP.

Infantile hydrocephalus: management using CT assessment

When determining a management plan for infantile hydrocephalus, the determining factor for or against the implantation of a shunt is the degree of ventricular dilatation. The author has devised a standardised method of estimating this, the use of which has been shown to achieve consistently successful results. Dilatation was determined using the ventricular/biparietal (V/BP) ratio from the axial CT scan at the mid-portion of the bodies of the lateral ventricles, showing the greatest ventricular dilatation. According to this method, hydrocephalus was classified into four grades. These were mild (V/BP ratio 0.26-0.40), moderate (V/BP ratio 0.41-0.60), severe (V/BP ratio 0.61-0.90) and extreme (V/BP ratio 0.91-1). A V/BP ratio of less than 0.26 was considered normal. This method appeared to be accurate and reproducible in infants with hydrocephalus including those with asymmetrical and multiloculated ventricular dilatation. In all the patients with mild hydrocephalus, spontaneous regression or stabilisation occurred and their developmental outcome was normal. Patients with moderate and severe hydrocephalus needed a ventricular shunt and the developmental outcome was satisfactory in 87% of the cases. They were functionally normal although 18 had some abnormal neurological signs. In patients with extreme hydrocephalus the developmental outcome following shunting was satisfactory in 31% of the cases. They were functionally normal although four had abnormal neurological signs. This plan of management was used in a total of 144 infants and it proved to be highly successful.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study of linear measurement of the brain and three-dimensional measurement of brain volume using CT scans

Parameters of linear measurement were compared with actual brain volume to assess the significance of linear measurements as indices of atrophy in 31 neurologically normal children and 22 neurologically abnormal children. Brain volume was established by means of an image-analyzing system using contiguous CT scans. The parameters or indices estimated were: (1) the maximum transverse width of both hemispheres, (2) the maximum longitudinal length of both hemispheres, (3) the maximum frontal subarachnoid space, (4) the maximum width of the interhemispheric fissure, (5) the maximum width of the Sylvian fissure, (6) Evans' ratio, (7) the maximum width of the third ventricle, (8) the cella media index, (9) the maximum width of the fourth ventricle. In neurologically normal children, the maximum transverse width of both hemispheres, the maximum longitudinal length of both hemispheres, the maximum width of the interhemispheric fissure and the maximum width of the Sylvian fissure correlated significantly with the combined volume (CV) of both hemispheres and basal ganglia. In particular, the maximum transverse width of both hemispheres and the maximum longitudinal length of both hemispheres had a high correlation. In neurologically abnormal children the maximum transverse width of both hemispheres and the maximum width of the interhemispheric fissure were significantly correlated with the CV of both hemispheres and basal ganglia.

Bannayan-Riley-Ruvalcaba syndrome

Here we report on 12 affected members of a family with Bannayan-Riley-Ruvalcaba syndrome. We present clinical evidence of overlap between Bannayan-Zonana syndrome. Riley-Smith syndrome, and Ruvalcaba-Myhre syndrome in this autosomal dominantly inherited condition. We expand the phenotypic spectrum to include Hashimoto thyroiditis, which occurred in 7 of our cases. Finally, we discuss the relationship between the syndrome and juvenile polyposis of infancy.

Myelination as an expression of the functional maturity of the brain

A prospective cross-sectional study was performed on hydrocephalic infants and children. MRI was used to assess the state of myelination and to quantify the intracranial cerebrospinal fluid (CSF) volume repeatedly in all children. At the same time, neurodevelopmental testing was performed. A positive correlation was found between the progress of myelination and psychomotor development, but there were no significant correlations between CSF volume and myelination or between CSF volume and psychomotor development. This study provides strong evidence in favour of Flechsig's thesis that myelination expresses the functional maturity of the brain. The interdependency of neuronal maturation and progress of myelination are discussed.

Measurement of progressive cerebral ventriculomegaly in infants after grades III and IV intraventricular hemorrhages

To develop guidelines that might help predict prospectively which infants with severe intraventricular hemorrhage (IVH) would require intervention, we obtained serial cranial sonograms to measure the rate of growth of cerebral ventricular volumes in 48 preterm infants with and without IVH. The infants were divided into three groups: (1) those with no IVH (22 infants), (2) those with IVH with acute ventricular dilation (13 infants), and (3) those with IVH with progressive ventricular dilation requiring intervention (13 infants). The decision to intervene because of progressive ventricular dilation was based on clinical criteria and the subjective assessment of increasing ventricular size on weekly cranial sonograms. The rate of cerebral ventricular volume growth in infants with IVH who needed intervention was greater (4.2 +/- 3.3 ml/day) than that in infants without IVH (0.0 +/- 0.1 ml/day; p less than 0.001) and in infants with IVH and acute ventricular dilation (0.0 +/- 0.2 ml/day; p less than 0.001). Using these data, we generated guidelines for predicting prospectively which infants with IVH and ventricular dilation will need intervention for posthemorrhagic hydrocephalus. The guidelines were then confirmed prospectively in 10 infants.

Volumetric quantification of brain volume in children using sequential CT scans

We devised a three dimensional method for the accurate measurement of brain volume and applied it to 32 neurologically normal children, 7 children with only mental retardation and 15 children with both mental retardation and motor disturbance. In the group of neurologically normal children, the total brain volume increased from 723 cm3 to 1407 cm3 in order of age. The correlation ratio between the total brain volume and age was significant (P less than 0.0001). The values of the total brain volume and the developmental curve were similar to those of the total brain weight of normal children previously reported. The combined volume of the cerebellum, the midbrain, the pons and the medulla also increased from 76 cm3 to 200 cm3 in a manner similar to that of the total brain. The correlation between total brain volume and head circumference was significant (P less than 0.0001). In the group of children with mental retardation, the total brain volume was relatively smaller than that of neurologically normal children. In the group of the children with mental retardation and motor disturbance, 10 out of 15 cases showed values below -2 SD of those of neurologically normal children. The values of the total brain volume were each less than -3 SD in 3 cases whose head circumferences were each more than -3 SD. Our method for the direct measurement of brain volume based on serial CT scans may be useful for the accurate examination of brain development.

The value of estimating pressure-volume index in childhood macrocephaly. The relationship between pressure-volume index and the volumes of intracranial structures

In this study on cerebrospinal fluid (CSF) dynamics in childhood macrocephaly, we investigated the relationship between the pressure volume index (PVI) and the volume of various brain structures. The most important variables of CSF dynamics are the outflow resistance (Ro) and the PVI. We applied a constant CSF infusion rate to measure the PVI. The volumes of intracranial structures were calculated by means of computed tomography. Our study revealed no significant correlation between PVI and CSF volume or between PVI and the intracranial volume, as suggested by earlier studies. We did, however, find a significant correlation between PVI and ventricle volume. These results indicate that in order to estimate PVI for clinical purposes, the ventricle volume rather than CSF volume or head circumference should be used.