A multimodal account of visual impairments in post-coma patients

Conclusions and Relevance: Visual impairments were present in 70% of patients. This high frequency calls for systematic screening of visual disturbances among severely brain-injured patients, especially those with altered consciousness where deficits may mask covert awareness. UWS/VS patients had greater visual network hypometabolism compared to MCS and eMCS/LIS, with no differences between the latter groups. Increased VEP amplitude and [ ¹⁸ F] FDG-PET metabolism were linked to fewer ophthalmological impairments, highlighting the role of visual pathways in consciousness recovery and the potential of VEP and [ ¹⁸ F]FDG-PET in predicting outcomes. Importance: Post-coma patients typically present disorders of consciousness of varying degrees, which limit their ability to self-report visual disturbances. An early identification of visual impairments is crucial in these patients, as deficits may bias the diagnostic evaluations, with dramatic consequences on therapeutic decisions. Objective: To examine the relationship between ophthalmological impairments, visual evoked potentials (VEPs), cerebral metabolism, and consciousness levels in post-coma patients with severe brain injuries. Design: Observational cross-sectional study between 2009 and 2020. Setting: Study conducted in a referral center for disorders of consciousness in Belgium. Participants: Referred sample of 74 adult patients with a history of prolonged acquired severe brain injury resulting in coma (at least 28 days since brain injury), with a diagnosis of unresponsive wakefulness syndrome/vegetative state (UWS/VS), minimally conscious state (MCS), emergence from the MCS (eMCS) or locked-in syndrome (LIS). Thirteen patients were further excluded after initial screening. Main Outcomes and Measures: Ophthalmology reports, VEP and [ ¹⁸ F]fluorodeoxyglucose-positron emission tomography ([ ¹⁸ F] FDG-PET) data were analyzed. Frequency of visual impairments was used as primary outcome measurement using ten ophthalmological features: eyelid, cornea, fundus, eye alignment, gaze deviation, pupillary reflex, ocular motility, visual pursuit and fixation. Secondary outcome measurements included VEP amplitudes (normal versus abnormal) and hypometabolic voxel count in visual regions using [ ¹⁸ F] FDG-PET. Patients were stratified by diagnostic groups based on the Coma Recovery Scale - Revised. Results: The final sample included 61 patients (27 female; mean age, 42.3 years), including 11 with UWS/VS, 29 with MCS, 17 with eMCS, and 4 with LIS (median time since injury, 12 months). Seventy percent of patients exhibited at least one ophthalmological impairment (100% UWS/VS, 69% MCS, 53% eMCS, and 75% LIS), with ocular motility impairment being the most frequent (31%). Abnormal VEPs were more common in UWS/VS (40%) than in MCS (5%; P = .03). UWS/VS patients had greater visual network hypometabolism compared with MCS (P = .02) and eMCS/LIS (P = .02), with no significant difference between MCS and eMCS/LIS (P = .86). The right occipital lobe showed a similar pattern, with UWS/VS differing from MCS (P = .02) and eMCS/LIS (P = .03), but no difference between MCS and eMCS/LIS (P = .64).