Vision changes prior to DBS surgery may risk delirium in patients

Delirium after DBS temporary, but could promote disease worsening

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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Changes in vision and eye health prior to deep brain stimulation (DBS) surgery can be a significant predictor of delirium in the hours after this Parkinson’s disease surgery, a study suggests.

A post-operative risk of the psychiatric condition was found to be greater in older patients and those with a diminished sense of smell.

Researchers used study findings to develop a predictive too that could help doctors in evaluating patients at risk of delirium after undergoing DBS.

The study, “Visual Dysfunction is a Risk Factor of Post-operation Delirium in Parkinson’s Disease,” was published in World Neurosurgery.

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DBS given to treat Parkinson’s motor symptoms

DBS is a surgical treatment of Parkinson’s aimed at interrupting the abnormal nerve signaling patterns that drive the disease’s motor symptoms.

During the surgery, fine wires are implanted in target brain regions, where they deliver electrical stimulation that’s controlled by a stimulator device placed elsewhere, usually under the collarbone.

Post-operative delirium is a psychiatric condition more common in elderly adults who have undergone DBS surgery. It is marked by symptoms such as hallucinations and changes in attention, cognition, consciousness, and sleep.

While delirium usually emerges shortly after surgery and its symptoms are temporary, its presence has been associated with a general clinical worsening for patients, the research team in China noted.

“Therefore, it is important for neurosurgeons to evaluate the risk of POD [post-operative delirium] prior to DBS,” they wrote, adding that few studies have focused on factors that might contribute to such risk.

The scientists retrospectively analyzed data covering 272 Parkinson’s patients who underwent the surgery at a university hospital in Jinan between June 2019 and August 2021.

They looked for potential POD risk factors, with a particular focus on vision issues. Visual problems are predictive of cognitive decline in Parkinson’s patients, and cognitive impairments have been linked to a risk of post-DBS delirium.

Among the patients — 144 men and 128 women —  65 or 23.9% of them experienced POD in the hours after their surgery, with delirium symptoms generally clearing within 12 hours and without complications.

These patients tended to be older than those without post-operative delirium (an average age of 64.52 versus 60.81) and showed some evidence of greater cognitive difficulties than the other patients, who served as a control group.

Vision issues, thinner retinal nerves found in patients with delirium

More significant visual dysfunction and a greater prevalence of eye-related symptoms also were reported in the group with delirium following DBS, as assessed by the Visual Impairment in Parkinson’s Disease Questionnaire (VIPD-Q).

In particular, problems related to the oculomotor domain, which includes double vision, were common in patients with post-operative delirium, occurring in 72.3% of these people compared with 44% of controls. This category was followed by symptoms related to the intraocular and optic nerve domains, which covers problems like changes in color and contrast vision.

Overall, patients who met the VIPD-Q cutoff for visual impairment had a significantly higher delirium prevalence than patients who did not meet that cutoff value.

Imaging of the eye’s retina — the back part of the eyeball that contains light-sensing cells — showed that patients with POD had a thinner layer of retinal nerves and a lower blood vessel density on the back surface of the eye.

Hyposmia, or a diminished sense of smell — a Parkinson’s non-motor symptom — also linked with a higher rate of post-operative delirium.

Surgical factors, including the location of the DBS stimulation, surgery time, and anesthesia were not found to influence a patient’s risk.

The effectiveness of DBS at easing motor symptoms also was not influenced by POD’s presence.

Using their findings, the researchers generated a point-based prediction system that could help doctors in determining those patients likely to experience POD after surgery.

“This tool is easy to use and can assist physicians in therapeutic decision-making,” the researchers wrote.

Study findings, they noted, are limited by the retrospective nature of the analysis and the inclusion of patients from a single center in China.

Still, data indicate that “neurosurgeons should closely monitor and screen patients with [Parkinson’s] who have ophthalmic problems before DBS,” the researchers concluded.