Caloric test intent to induce horizontal nystagmus. Nystagmus is characterised by the slow movement of the eyes to one direction followed by fast saccade towards the opposite direction. The direction of nystagmus is usually determined by the direction of this fast saccade (and not by the direction from the initial slow movement). When cold water is inserted into the left ear, the eyes will move slowly to the left, but followed by a fast saccade movement to the right. The reason for COWS is hence because the direction to where the eyes quickly move to (in this case towards the right) to correct for the initial left movement determined the final direction of the nystagmus. Hence Cold - Opposite
Thanks for the video! Very well explained ! NISTAGMUS has 2 components : 1.slow phase and 2. fast phase ❄❄❄ ᙅ〇ᒪᗪ WATER ❄❄❄ when we inject with a syringe some COLD WATER in one ear ----the EYES will move SLOWLY to the SAME side as the syringe. (phase1) Then , the FAST phase will happen which will move the eyes in the OPPOSITE side of the syringe.(phase 2) So for COLD water, we get slow phase on tha same side , and fast phase on the opposite side, this is why the mnemonic says "CO" ,...cold-opposite actually refers to phase 2, to the fast phase of the nistagmus! (which is usually more easily observed when you look at the patient,because well it's sudden and it's fast and you say woaaa ! ) -------------------- ----------------- ------------------ ---------------------- 🔥🔥🔥🔥ᗯᗩᖇᗰ water when we inject warm water, phase 1 - aka the slow phase is moving the eyes OPPOSITE to the syringe with warm water. and phase 2 - the fast -phase is moving the eyes towards the syringe, to the SAME side as the syringe with warm water. So you notice the fast phase, beating to the same side as the syringe. WS- warm -same-refers to the phase 2 , the fast phase. _____________________________________- SO acronym COWS makes you remember in which direction is the PHASE 2 -THE FAST phase ! 🐮 COWS are fast, man ! I tell ya ! __________________________________ But we must always keep in mind that initially there is a slow phase(which is ..well slow, and smooth and not so spectacular and noticeable-, aka phase 1 that is actually remembered by the acronym CSWO.... The fast phase (phase 2) is under the control of the cerebral hemispheres and it requires the patient to be conscious.... .WHY IS THIS IMPORTANT ? I found this : The effect of the cold water in the ear is to fool the hair cells of the ampulla into thinking that the head is being turned to the opposite side. If this test is performed with cold water in an awake patient, the eyes will still tend to drift to the tested ear. The awake patient will try to compensate for this with fast sacchades back to midline, or some other point of fixation. This has given rise to the COWS mnemonic: Cold - Opposite, Warm - Same. COWS refers to the direction of fast nystagmus in the awake patient. In the comatose patient, there will be little or NO nystagmus, and the deviation of the eyes will be completely opposite (Warm- Opposite, Cold - Same). In fact, the presence of nystagmus on cold caloric testing in the apparently unconscious patient suggests that they are in fact conscious, and only pretending to be comatose. TAKEN from :derangedphysiology.com/main/required-reading/neurology-and-neurosurgery/Chapter%204.6.7/oculocephalic-and-cold-caloric-reflexes-cn-iii-iv-vi-and-viii I wrote this to make myself undestand hope it will help others too !𝔾𝕆𝕆𝔻 𝕃𝕌ℂ𝕂 with your studies folks !!!
Thank you, can you do more? A lot of resources/professors just tell us what the test indicates but doesn't explain the circuit like this. This helps a lot.
Thanks a lot this cleared my confusion. In harrison they have not elaborated it properly made me even more confused. COWS is for nystagmus CSWO for eye movement.
Agreed. There's not so much a misconception as a discordance with what people are talking about. COWS is referring to direction of nystagmus, which is opposite to the slow phase drift. Cold inhibits the canal, and causes a drift towards the tested ear and a fast phase saccade (nystagmus) away - or towards the opposite side (CO), whereas warmth causes a stimulation, subsequent slow phase away from the tested ear, but a corrective saccade (nystagmus) back to the same ear (WS). Hence COWS. The author was just referring to the slow phase rather than the saccade, so as long as you have the connection of COWS = nystagmus (or WOCS = slow) , then either way is a correct way to conceptualise it.
This video is really helpful thank you so much. Can you make a video on what will happen if there is a lesion on the Vestibular nuclei or Vestibular nerve.
anyone had this test done and have vertigo for days after? mine isnt severe but ive got a rotating sensation, floor moving, fatigue..... its been 4 days im so scared its permanent
This video is awesome, great explanation. I have one question tho. Cold water sinks and warm water rises, I didnt really get how that affects the movement of endolymph. Can you elaborate please? Does that mean that cold water makes endolymph more dense and dense doesnt move as fast as warm endolymph? even if so, why does it make a change if we dont actually move, because endolymph doesnt move unless acceleration occurs right? How will warm endolymph start to move with no change in heads position. Im sorry if this is a stupid question, Im not good with physics xD
So the initial movement which is CSWO wasnt a Nystagmus, but the second corrective movement is a Nystagmus with COWS mnemonic, and it moves with fast saccadic movement ?
So this is testing the Vestibular Ocular Reflex, and CSWO refers to this, while COWS refers to the nystagmus? How does this relate to the terms "left-beating" and "right-beating nystagmus"?
Can you explain why a physician does this rather than a nurse? Is it simply because a nurse cannot diagnose brain death? Or can you cause harm by doing this on someone? I’m guessing it is the former and not the latter.
Nurses can diagnose brain death. Usually, it's under the supervision of a physician. The diagnosis of brain death can be done by others than just a doctor but the law varies on where you are. This is more of a legal thing.
Shvan Jalal cows basically stands for the nystagmus, the fast component, which means when I use cold water to normal person the eyes will deviate to the side of irrigation , now right after deviation it will go back to midline (NYSTAGMUS) , that’s why they say cold linked with opposite , the opposite is nystagmus , not the initial eye movement keep in mind . So cows for normal person for the NYSTAGMUS
Dear,I understood it ,thank u for repetition, but My question was that (If the COWS is using for testing the normal person to see what happen in nystagmus patient ) or ( COWS is using for nystagmus patient ) ,, I think it must use for normal person 🌹
Shvan Jalal we don’t use cows generally to a normal person but , a person is comatose then this maneuver is performed to see cranial nerve 3-6 , if patient cranial nerves are damaged then it would be CSWO for the nystagmus.
That indicates brainstem lesion as there is a impairment of cranial nerve 3-6 , used for extraoccular muscles. If person is comatose , and this maneuver is showing CSWO for the NYSTAGMUS then you suspect lesion in brainstem :)
