Mild traumatic brain injury affects visual, neurocognitive function

Eye movement dysfunction is one consequence of mild traumatic brain injury (MTBI) in pediatric patients. Emerging data from studies using functional magnetic resonance imaging (MRI) shows new information about neurocognitive impairment. 

This article was reviewed by Mitchell B. Strominger, MD

Mild traumatic brain injury (TBI) in pediatric patients can result in a variety of visual function deficits, according to Mitchell B. Strominger, MD.

Dr. Strominger, a pediatric ophthalmologist and neuro-ophthalmologist at Renown Medical Center, Reno, NV, and professor of Surgery, Ophthalmology, and Pediatrics, University of Nevada Reno School of Medicine, focused on abnormalities involving control of eye movement that can be seen after mild TBI and discussed new information from studies using functional magnetic resonance imaging (fMRI) to investigate the neurocognitive consequences of these events.

Impairment of saccadic eye movements is one type of visual dysfunction that can occur after mild TBI. Another is self-paced saccades. 

“With bedside evaluation of saccadic eye movements, most patients with mild TBI test will test normal, needing just one saccade to acquire the target,” Dr. Strominger said.

Smooth pursuit eye movements can also be affected after mild TBI. In testing of smooth pursuit, patients with TBI have been shown to have decreased target position, increased eye position error, and variability of eye position. 

Vergence eye movements can also be affected after mild TBI. Convergence insufficiency is common. Signs and symptoms include impaired near point of convergence, double vision, and loss of place while reading. It may also be accompanied by accommodative insufficiency with a decrease in accommodative amplitude. 

Testing for vergence dysfunction should be done using an accommodative target.

Vestibulo-ocular reflex dysfunction also occurs in mild TBI. Affected patients complain about vertigo and oscillopsia. Spontaneous nystagmus is possible, although Dr. Strominger said he has only seen that in a single case.

“The child was evaluated 15 minutes after suffering a concussion,” he noted. “Most patients are not seen for days after the injury.”

Emerging concerns
MRI scans will be normal in patients with mild TBI, but investigations using fMRI are generating concerning findings about the functional consequences of mild TBI in the pediatric population, Dr. Strominger said.

One study evaluated college athletes 10 to 15 days after a concussive event. Although neurocognitive assessments across six domains showed no evidence of impairment, fMRI demonstrated that compared with normal subjects, the concussed athletes demonstrated increased connections between areas of the brain that underlie executive function.

The findings were different in a study that included younger patients (mean age 14 ± 2 years) who had sustained mild TBI. The athletes in this study showed reduced working memory accuracy than controls that was associated with reduced activity in the dorsolateral prefrontal cortex, which is the area of the brain underlying executive function.

“The findings in this study suggest that these younger individuals may be unable to engage compensatory strategies to maintain cognitive performance following mild TBI and might explain why some youths appear to have long term problems with cognitive function following a concussion,” Dr. Strominger concluded. “Importantly, the study also indicates that the immature brain is not more plastic to diffuse injury as has been believed but instead is more vulnerable.

Mitchell B. Strominger, MD
E: mstrominger@renown.org
This article is adapted from Dr. Strominger's presentation at the American Academy of Ophthalmology 2019 annual meeting. He has no financial disclosures related to this content.