Dolls eye Flashcards
For a complete test and a maximal stimulus, the following manoeuvres must be performed: Rotate the head to one direction. The eyes should deviate in the opposite direction. This deviation should be smooth and conjugate. Keep the head in that position. The eyes should slowly return to midline. Rotate the head to the opposite direction; i.e. if facing to the right, turn the head to face the left. This is the maximal stimulus for this test. Again, the eyes should move smoothly in the opposite direction.
A normal response is the conjugate deviation of gaze, and an abnormal response is a persistent fixed gaze, with no eye movement. If you grab the head of a conscious person and give it a good twist, their eyes will remain facing midline because the voluntary control of eye movement overcomes this reflex. Thus, the oculocephalic reflex is only testable in the unconscious patient.
A lateral pontine lesion has taken out the vestibular nuclei on the right side. Neither eye will respond to stimulus on that side
The pathways which command this reflex involve vestibular nuclei, lower pontine tegmentum, the upper pontine tegmentum, the midbrain paramedian tegmentum, and the medial longitudinal fasciculus. These are large, central brainstem regions, which overlap with the ascending arousal system. The oculocephalic reflex is intact, the coma is unlikely due to a structural brainstem lesion.
This is a syndrome where both the MLFs are taken out, and one of the abducens nuclei. The result is a situation where only the unaffected side will behave normally in response to cold caloric testing (that’s the “half”).
The result resembles a complete lesion in the midbrain (i.e. destruction of the CN III and IV nuclei)- but in a bilateral MLF lesion, the pupillary light reflex would be spookily preserved, and that is how you would discriminate between them.
CN III and IV are not talking to each other. The result resembles a complete lesion in the midbrain (i.e. destruction of the CN III and IV nuclei)- but in a bilateral MLF lesion, the pupillary light reflex would be spookily preserved, and that is how you would discriminate between them.
