gms | German Medical Science

Objective: Outcome after subarachnoid hemorrhage (SAH) is significantly determined by early brain injury (EBI) and delayed cerebral ischemia (DCI). Experimental data identfied impairment of neurovascular coupling (NVC) as an important contributor to both EBI and DCI, but clinical proof of its existence could not be provided so far. Retinal vessel analysis (RVA) allows non-invasive assessment of the neurovascular unit. Using RVA, we aimed to assess the integrity of NVC in patients with SAH.

Methods: In a prospective study, we performed RVA in 24 patients with acute SAH (group A: day 5-14) and eleven patients at the time of follow-up (group B: mean 90±35ds after SAH), and included 35 age-matched healthy controls (group C). Data was acquired using a Dynamic Vessel Analyzer (Imedos Systems UG, Jena) for examination of retinal vessel dimension and neurovascular coupling (NVC) using flicker-light excitation (FLE).

Results: Diameter of retinal arteries were comparable for all groups, while veins were significantly dilated after SAH compared to the control group (p<0.001). NVC of retinal arteries was significantly impaired early after SAH (A) as characterised by attenuated dilatation (p<0.001) and reduced area-under-the-curve (p<0.01) after FLE when compared to the control group (C). Partial recovery over time was observed for group B, though arterial dilatation was delayed (p<0.05). Venous response to FLE was significantly delayed after SAH (A: p<0.001; B: p<0.05), but not diminished. Vessel response to FLE was not influenced by treatment with nimodipine.

Conclusion: To our knowledge, this is the first clinical study to document impairment of neurovascular coupling in patients with SAH. Using retinal vessel analysis, distinct differences of compromise were detected for the arterial and venous compartment of the neurovascular unit. Recruitment will continue to facilitate a correlation analysis with clinical course and outcome.