life_in_mono
Forum Junior
Topics: 16
Posts: 28
|
JUst remeber COWS of fast component ie Cold opposite , warm same side ... cold representing lesion , so nystagmus (fast) wud be opposite to lesion. warm representing eye deviates slowly towards the lesion first then a fast eye moovement to opposite side.
now how to understand this ,since nystagmus caused by lesion on the vestibulo occular reflex (meaning involves vestibular nerve + nuclie) during conjugate eye moovement ( merdial rectus (CN 3 and lateral rectus CN 6) .Turning our head to the right ( ie horizontal head mooovement ) stimulates hair cells in semicircular ducts . that stimulates vestibular nuclie thru Viii nerve , that sends signal to (since horizontal moovement )left VI nerve (for lat rectus ) and right III nerve (for med rectus) thru MLF nuclie. so if theres a lesion in vestibular nuclie or nerve of the right these two won't work,but the left one wud work and cause a slow deviation to the right (ie warm same side of lesion) but since horizontal conjugate gaze is working fine ie left cerebral cortex sends signal to PPRF then VI nucleus (right lat rectus ) and MLF --> III --> Medial rectus thus eyes make a fast (nystagmus) change to the left . hope this helps
|
| Dr.Papez
Forum Senior
Topics: 0
Posts: 152
|
Cold stimuli inhibits semicircular canal and warm activates...
each canal when activated will push the eyes to the opposite side and when inhibited keeps quite...this makes the opposite canal relatively excited and does its job (ie to push to opposite side)-so dientify to whish sise the eye moves.
The nystagmus-which is a carrective component to bring back the drifting eyes (from cortex) is opposite to the side of initial eye deviation.
Lesion behaves like a cold stimuli.
Leen...ask specific questions...I will try to answer. Good luck
|
|
| |
| | |
