Content Flashcards
What does skew deviation indicate?
Vertical deviations are more concerning for central pathology
Define tropia.
Ocular malalignment that is always present, Cannot correct misalignment when focusing on target.
Define phoria.
Ocular malalignment only evident when binocular viewing/fusion is blocked. Becomes more appararent with fatigue. Best elicited with cross-cover test
What types of nystagmus are considered central signs?
Pure vertical, pure torsional, or direction-changing nystagmus
What is spontaneous nystagmus associated with?
Acute peripheral vestibular lesions; it is direction-fixed and follows Alexander’s Law
What does impaired saccades indicate?
A central sign
What does saccadic/cogwheel pursuit indicate?
A central sign
What is dysconjugate gaze?
A central sign indicating misalignment of the eyes during gaze
What does VOR cancellation refer to?
The ability to suppress the vestibulo-ocular reflex
What does an inability to suppress VOR indicate?
A central sign
What is the role of the paramedian pontine reticular formation in eye movement?
It sends signals to the abducens nucleus.
When the connection between the abducens nucleus and the oculomotor nucleus is interrupted, what happens to the eye ipsilateral to the lesion?
It cannot adduct past the midline when the contralateral eye moves laterally.
What is the effect on the eye contralateral to the lesion when there is an interruption between the abducens nucleus and the oculomotor nucleus?
The eye contralateral to the lesion moves normally.
How can you distinguish between internuclear ophthalmoplegia and 3rd cranial nerve palsy?
Internuclear ophthalmoplegia impairs adduction only, while 3rd cranial nerve palsy impairs both adduction and convergence.
What does Alexander’s Law state about nystagmus?
The amplitude of the nystagmus increases when the eye moves in the direction of the fast phase
This law explains the behavior of nystagmus in relation to eye movement.
What happens to nystagmus when visual fixation is blocked?
Nystagmus increases
Nystagmus is an involuntary eye movement that can be affected by visual fixation.
What does the term ‘ampullopetal’ refer to?
Displacement ‘toward’ the ampulla
The ampulla is a structure located at the base of each semicircular canal.
What does the term ‘ampullofugal’ refer to?
Displacement ‘away’ from the ampulla
This term describes the direction of fluid movement in the semicircular canals.
What does Ewald’s law say?
A stimulation of the semicircular canal causes a movement of the eyes in the plane of the stimulated canal
What is the function of the cerebellar flocculus?
Required to adapt the gain of the VOR
VOR stands for vestibulo-ocular reflex, which helps stabilize gaze during head movements.
What does the cerebellar flocculus respond to in order to improve gaze stability?
Retinal slip
Retinal slip refers to the movement of the image across the retina due to head motion.
What role does the cerebellar nodulus play in VOR responses?
Adjusts the duration of VOR responses
The nodulus also processes otolith input related to balance and spatial orientation.
What are common effects of lesions in the cerebellar areas discussed?
Gait ataxia and nystagmus
Gait ataxia refers to a lack of voluntary coordination of muscle movements, while nystagmus is characterized by involuntary eye movement.
What does the cerebellar vermis respond to?
Vestibular stimulation
The cerebellar vermis has an inhibitory influence on the vestibular nuclear complex.