[Assessing the localization and extension of brainstem lesions with the orbicularis oculi reflex (author's transl)].

The electrically evoked Orbicularis Oculi Reflex (OOR) consists of two separate components (R1 and R2). Within the last years the central pathways of R1 in pontine and R2 in medullary brainstem areas could be further elucitated. We have investigated the OOR in 66 patients with signs of a brainstem affection, obtaining pathological results in 67% of the cases. Five characteristic types of OOR-alterations could be differentiated. Type A with an isolated R1- and type B with an additional R2-Alteration point to pontine lesions. Type C, D, E with different R2-Alterations are indicative for medullary lesions. Disorders of the spinal trigeminal complex or the lateral bulbar reticular formation only can be distinguished from a combined lesion of these structures. Careful analysis of the alterations of the OOR-components and correlation with the known anatomical data provide a means to localize brainstem affections and to assess their extension.