Brainstem Reflexes
Oculo-cephalic reflex
The presence of this reflex is usually pathologic and it is connected with both-side hemispheral or nuclear (brainstem nuclei) lesions. When we move head of a patient passively, eyes look like if they stay in the midline, but in fact they move on the opposite side than head. In healthy man, who is conscious, eyes follow the direction of movement (reflex is not present). We usually examinate horizontal and vertical rotation.
A lesion of cranial nerves has its specific clinical look. Lesion of n. oculomotorius (III.) leads to problem with vertical movement of eye or its adduction. A damage of n. abducens (VI.) is connected with disability of eye abduction. A brainstem damages are different in this way and affect movement ability of both eyes (their conjugation).
There is one very important contraindication of this examination - trauma of a cervical spine - because we could seriously injured patient. Sometimes a result can be false-positive thanks to influence of some medication (anesthesia).
Vestibulo-ocular reflex
Also sometimes called caloric reflex, because a stimulation is based on pouring of cold or warm water into the ear. It is better to put patient´s head a slight reclining, because we want to influent especially lateral semicircular tubule of an inner ear. A small amount of water flow induces movement of endolymph.
Test can be sometimes false-positive if there is any other diasease of inner ear. Normally we react just a little bit, because nystagmus in healthy people corrects the eyes movements. There is one special rule for direction of nystagmus: "Cold opposite, warm same (COWS)", which means that cold water pouring into the left ear leads to eye movement to the left and a direction of the nystagmus is on the right (opposite side). It is the same for the second side – pouring of warm water into the left ear leads to eye movement to the right and a direction of the nystagmus is on the left (same side).
Attention! Do not confuse the direction of nystagmus (COWS rule) and the direction of motion of eyes.
Links
Related articles
Bibliography
- AMBLER, Zdeněk, et al. Klinická neurologie : část obecná. 1st edition. 2008. ISBN 978-80-7387-157-4.
