Researchers Explore Convergence Insufficiency, Cognitive Impairment in Parkinsonian Disorders

Convergence insufficiency (CI) in Parkinsonian disorders causes disabling visual symptoms during close-up work or reading, usually manifesting as double or blurred vision; these vision problems are more common in patients who report cognitive symptoms. The relationship between cognitive impairment and symptomatic convergence insufficiency in Parkinsonian disorders has not been previously investigated. Researchers recently sought to determine if symptomatic CI, as opposed to asymptomatic CI, could serve as a marker of Parkinson cognitive impairment.

Twenty-four patients—18 with Parkinson, 5 with progressive supranuclear palsy, and 1 with multiple system atrophy—were included. Researchers collected objective findings of convergence insufficiency on neuro-ophthalmologic examination and recorded subjective visual symptoms and cognitive complaints. Objective measures included a near point of convergence (NPC) of ≥10 cm or a near/distance disparity of ≥10 prism diopters of an exotropia. The presence of CI, the NPC in centimeters, and subjective reports of visual symptoms were recorded from the medical record. The Self-Administered Gerocognitive Examination was used as a global cognitive screening measure.

Most (70.8%) had visual symptoms attributed to CI (n = 17); the rest (n = 7) had asymptomatic CI with visual complaints due to other causes (eg, exotropia, saccadic deficiency, dry eye). Three-quarters reported subjective cognitive complaints and 54.1% met SAGE criteria for cognitive impairment (total score <17).

Logistic regression models demonstrated no significant relationship between symptomatic CI status and cognitive impairment (P = .29). However, there was a significant relationship between NPC and cognitive impairment, using linear regression, even when controlling for age, education, and disease duration (P = .038). NPC was greater for those with cognitive impairment (x = 18.4 cm), compared to those who were cognitively intact (x = 12.5 cm, P = .003).

The group had lived with the diseases for a mean of 9.1 years at the time of chart review and were at higher risk of cognitive impairment, but the researchers noted there was no significant difference in disease duration between those who were cognitively impaired and those who were not.

The authors wrote that clinicians should suspect cognitive impairment in patients with objective findings of CI, whether symptomatic or not. The severity of CI may serve as an additional marker for cognitive impairment in Parkinsonian conditions, separate from age, and disease duration, and there may be a shared mechanism of dysfunction that deserves further research, they said.

Reference

Holden SK, Van Dok E, Pelak VS. Co-occurrence of convergence insufficiency and cognitive impairment in parkinsonian disorders: A pilot study [published online August 9, 2019]. Front Neurol. doi: 10.3389/fneur.2019.00864