Ratios of head circumference to ventricular size vary over time and predict eventual need for CSF diversion in intraventricular hemorrhage of prematurity.

PURPOSE: Intraventricular hemorrhage (IVH) of prematurity can lead to hydrocephalus, sometimes necessitating permanent cerebrospinal fluid (CSF) diversion. We sought to characterize the relationship between head circumference (HC) and ventricular size in IVH over time to evaluate the clinical utility of serial HC measurements as a metric in determining the need for CSF diversion. METHODS: We included preterm infants with IVH born between January 2000 and May 2020. Three measures of ventricular size were obtained: ventricular index (VI), Evan's ratio (ER), and frontal occipital head ratio (FOHR). The Pearson correlations (r) between the initial (at birth) paired measurements of HC and ventricular size were reported. Multivariable longitudinal regression models were fit to examine the HC:ventricle size ratio, adjusting for the age of the infant, IVH grade (I/II vs. III/IV), need for CSF diversion, and sex. RESULTS: A total of 639 patients with an average gestational age of 27.5 weeks were included. IVH grade I/II and grade III/IV patients had a positive correlation between initial HC and VI (r = 0.47, p < 0.001 and r = 0.48, p < 0.001, respectively). In our longitudinal models, patients with a low-grade IVH (I/II) had an HC:VI ratio 0.52 higher than those with a high-grade IVH (p-value < 0.001). Patients with low-grade IVH had an HC:ER ratio 12.94 higher than those with high-grade IVH (p-value < 0.001). Patients with low-grade IVH had a HC:FOHR ratio 12.91 higher than those with high-grade IVH (p-value < 0.001). Infants who did not require CSF diversion had an HC:VI ratio 0.47 higher than those who eventually did (p < 0.001). Infants without CSF diversion had an HC:ER ratio 16.53 higher than those who received CSF diversion (p < 0.001). Infants without CSF diversion had an HC:FOHR ratio 15.45 higher than those who received CSF diversion (95% CI (11.34, 19.56), p < 0.001). CONCLUSIONS: There is a significant difference in the ratio of HC:VI, HC:ER, and HC:FOHR size between patients with high-grade IVH and low-grade IVH. Likewise, there is a significant difference in HC:VI, HC:ER, and HC:FOHR between those who did and did not have CSF diversion. The routine assessments of both head circumference and ventricle size by ultrasound are important clinical tools in infants with IVH of prematurity.

The medial temporal lobe supports the quality of visual short-term memory representation.

The quality of short-term memory (STM) underlies our ability to recall the exact details of a recent event, yet how the human brain enables this core cognitive function remains poorly understood. Here we use multiple experimental approaches to test the hypothesis that the quality of STM, such as its precision or fidelity, relies on the medial temporal lobe (MTL), a region commonly associated with the ability to distinguish similar information remembered in long-term memory. First, with intracranial recordings, we find that delay-period MTL activity retains item-specific STM content that is predictive of subsequent recall precision. Second, STM recall precision is associated with an increase in the strength of intrinsic MTL-to-neocortical functional connections during a brief retention interval. Finally, perturbing the MTL through electrical stimulation or surgical removal can selectively reduce STM precision. Collectively, these findings provide converging evidence that the MTL is critically involved in the quality of STM representation.