We'll proceed with the next presenter. That's Jennifer Kwon talking about optic nerve diffusion tensor abnormality in children presenting acutely with hydrocephalus. Thank you. I'm Jennifer Kwon. I'm one of the neurosurgery residents at Stanford. And today I'm going to be talking about optic nerve diffusion tensor imaging abnormalities in children presenting with hydrocephalus. I have no disclosures. Everyone here is very familiar with hydrocephalus, especially its symptoms. But in brief, children, like adults, can often present with headaches, nausea, and vomiting. And even though it's harder to assess, especially in younger children, patients can also have visual changes in papilledema. Papilledema can resolve over time after the treatment of elevated ICPs. And in some cases, it can be used as a marker of surgical success. In cases of delayed treatment, patients can have long-lasting visual deficits. Evidence of optic nerve swelling and compression can actually even be visualized on standard MR imaging. On the left, we have imaging from a 21-month-old with hydrocephalus and a visibly swollen T2 hyper-intense optic chiasm. On the right, we have a 10-year-old with ventriculomegaly. And you can see visible bowing of the optic chiasm. And it's well-established that hydrocephalus can damage the brain, especially the developing brain. Previous studies have shown that diffusing tensor imaging can be used to assess white matter changes in the setting of hydrocephalus, as well as used in other disease processes. Thus far, no studies have examined DTI-based microstructural changes in the optic nerves of children with hydrocephalus. We hypothesize that these metrics, specifically mean diffusivity and fractional anisotropy, would be negatively impacted. Our study included 21 children presenting with acute hydrocephalus. The mean age was about seven years old. We had about two-thirds boys and one-third girls. And we also included 21 age-matched controls. We included patients who presented with symptomatic hydrocephalus from an obstructive posterior fossa mass. All the patients had pre-intervention MRIs performed on a 3T magnet. And all the patients had DTI imaging. We used a standard DTI protocol for image acquisition used at our institution. And for our DTI analysis, we needed to identify the optic nerves as a region of interest. So the reviewer selected the mid-segment of the intracronal optic nerve with the optimal signal to noise ratio on DTI imaging. Where it was incompletely visualized, the region slightly either anterior or posterior to the mid-portion was selected. The ROI was adjusted based on the size of the optic nerves, which range from 10 to 15 square millimeters. And a second blinded board-certified neuroradiologist independently assessed the data set for proper ROI placement. DTI metrics were compared against age-matched healthy controls, as well as after neurosurgical intervention. So we had two follow-up imaging groups, either early follow-up, meaning within three months of the intervention, or late follow-up, meaning greater than two years after the intervention. Twenty patients underwent tumor resections. Seven patients had EVD placements. And six patients had VP shunts placed. The medium follow-up time in the short follow-up imaging group was about 12 days. And the long-term follow-up group was about greater than three years. What we found was that preoperative bilateral mean diffusivity and fractional anisotropy values significantly differed from age-matched healthy controls, essentially indicating that these patients already had evidence of white matter damage in their optic nerves. Surgical intervention resulted in significant improvements in the bilateral optic nerve MD and in the right optic nerve FA. The left optic nerve FA trended toward significance, but this was not statistically significant. Here's a graph showing the same findings. You can see the pre- and immediate post-op intervention comparison. The mean diffusivities on the left, which decreased after intervention, and the FA on the right increased. How does this compare to healthy controls? Well, what we found was that in long-term follow-up, bilateral MD and left FA values actually restored to near-normal levels, whereas the right FA values remained abnormal. Again, here's a graph depicting the MD values in short and long-term follow-up. You can see the colored lines on the right. That represents about the level of the healthy controls. And again, MD significantly differed immediately after intervention, and that long-term follow-up was near-normal levels. The FA significantly increased in the right optic nerve and appeared to nearly normalize in the left. So in our study, we found significant diffusion tensor changes as a result of acute hydrocephalus. The restoration of values to near-normal levels after neurosurgical intervention suggests that these may be reversible changes. So we think that there may be a future role for optic nerve DTI, and it may be valuable for assessing surgical success or, you know, in converse, permanent neurologic deficit. Thank you.

Jennifer Kwon

neurosurgery resident

Stanford University

optic nerve diffusion tensor imaging abnormalities

children with hydrocephalus