Aa
The Cranial Nerves and What They Are About
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear (also Auditory)
Glossopharyngeal
Vagus
Accessory/Spinal
Hypoglossal
A little bit on the Cranial Nerves: These are a twelve sets of nerves that sprout directly off the brain and brainstem. Thus, even though they go out into the body, (like peripheral nerves do) their origins are in the white matter of the Central Nervous System. So these 12 nerves (actually 24 nerves, one on each side) are considered white matter. A lot of the common MS sites of demyelination involve the Cranial nerves. If you have read many of my posts, you'll remember that I am always mentioning that this that or the other symptom are from lesions in the Cranial nerves.
The Cranial Nerves have an wide interaction with each other to give the brain far more information and control than the nerves do alone. They interact within the brainstem through a series of nerve hubs called nuclei (plural of nucleus). Through these nuclei we have greater understanding of what we see, can move our eyes in complex ways, have greater balance and coordination.
CN I - is the Olffactory Nerve -
What it does - this nerve comes directly off the brain and handles the entire job of the sense of smell.
What happens when MS attacks it - Changes in sense of smell can occur in MS, from partial or complete loss of smell to alterations in smell like smelling weird things that aren't there.
CN II - the Optic Nerve -
What it does - Yep, handles the whole process of sight and vision. As a sensory nerve, the Optic Nerve picks up the image in light and color and carries it backwards to the brain where the information is processed by several parts of the brain. This forms the images we see, and adds to the information that keeps us upright in space and helps us keep our balance. The information is also used in the cerebellum to help us with fine motor and coordination.
Lesions on this nerve from MS cause the condition Optic Neuritis, symptoms include decreased vision, pain behind the eye, pain with eye movements, loss of color saturation (vivid colors become paler or more grayed out), flashes of light, loss of parts of the field of vision
CN III - the Oculomotor (eye movement) Nerve
What it does - It's a motor nerve. This nerve handles 4 of the six muscles that allow the eyeball to move around, instead of staring straight ahead.
It also raises one of the major muscles of the upper eyelid on the same side. Alesion will cause the eyelid on the same side to droop.
It also has the function of working to control the pupil constriction to light and to close/far vision. Lesion can change our ability to bring objects at different distances into focus.
When there is a lesion on it it can cause double vision because the affected eye cannot move in coordination with the normal eye.
The eyelid on the same side can droop
The pupil on that side may not respond as promptly to light.
CN IV - the Trochlear Nerve
This nerve handles the muscle that allows the "opposite" eye to rotate using the supeior oblique muscle. This allows fine tuning of the eye movements other than just up/down and side-to-side. It is the only cranial nerve that crosses over to direct something on the OPPOSITE side of the face.
Lesion - double vision
CN V - the Trigeminal Nerve
This is the major sensory nerve for sensation to the face and the motor nerve for chewing. The Trigeminal Nerve also handles the sensation from the sinuses, from the outside surface of the eardrum, and from the meninges. This nerve has three main branches. ( It's name means "three roots) V1 brings sensation from the upper part of the face and eyelid, the temple and the forehead. It may reach as far as the top of the scalp. V2 is the mid-part of the face, cheek, nose. Also the upper teeth, gums,upper lip and inner cheek. V3 handles the sensation from the lower face, lower teeth and gums, and lower lip. It extends down to and slightly beyond the jawline.
Lesion - It is responsible for the sensations of numbness, tingling and PAIN (as in Trigeminal Neuralgia) seen in MS. There can be an alteration of sensation noted both preceeding and following an episode of TN. A lesion may cause inability to chew effectively or fatigue with chewing.
CN VI - the Abducens Nerve - This motor nerve handles the same side eye muscle attached to the outside eyeball and allow the eye to turn laterally to the side.
CN VII - The Facial Nerve - This nerve handles most of the muscles of the face and lips and around the eye. But it is not only a motor nerve. It is also a sensory nerve and a visceral nerve. (A visceral nerve causes actions in an organ of the body like causing a gland to secrete or causing the bowles to have peristalsis). It handles part of the control of the glands of the face. It also carries sensation from the ear, the middle ear and the interior of the eardrum. It handles taste for the anterior 2/3's of the tongue on the same side. When this nerve goes wonky you get a Bell's Palsy - Drooping of the side of the face, droopy eye, etc.
CN VIII - The Auditory Nerve - This is a sensory nerve responsible for Hearing and Balance (peripheral balance) Damage to this nerve can cause hearing loss and vertigo, and tinnitus.
I'll do the last 5 nerves later. Also some neuroanatomists claim there is a Nerve #0 which is responsible for the production of pheromones.
There are uncounted mnemonics for remembering the cranial nerves and there order. These range from odd to silly to downright slutty.
On Occasion Our Trusty Truck Acts Funny. Very Good Vehicle Any How.
On Old Olympus' Towering Tops A Friendly Viking Grew Vines and Hops
Only On Occasion, Touching The Amorous Female Virgin Goat Vacillates A Hand
OLympic OPium OCcupies TRoubled TRiathletes After Finishing VEgas Gambling VAcations Still High
Orange orangutans often try to avoid feeding angry gorillas very ancient hotdogs.
On Old Olympus' Tufted Top A Fat Armed German Viewed An Hop
Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly
Only Older Octogenarians That Take A Free Viagra Get Very Aroused Here
Oh, Oh, Onward Through The Airy Facade Viewing Gorgeous Vixens Acessorizing Hedgehogs
Another set of mnemonics helps to remember the nerves' purposes and to remember the types of information these nerves carry (Sensory, Motor, or Both) is thus:
Some Say Money Matters, But My Brother Says Big Brains Matter More.
Some Say Money Matters, But My Brother Says Big Boobs Matter More.
Small Ships Make Money, But My Brother Says Big Boats Make More.
Some Say Marilyn Monroe, But My Brother Says Bridgette Bardot Mmmm Mmmmm
I had been waiting to finish this, but decided a little was better than nothing.
Quix
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear (also Auditory)
Glossopharyngeal
Vagus
Accessory/Spinal
Hypoglossal
A little bit on the Cranial Nerves: These are a twelve sets of nerves that sprout directly off the brain and brainstem. Thus, even though they go out into the body, (like peripheral nerves do) their origins are in the white matter of the Central Nervous System. So these 12 nerves (actually 24 nerves, one on each side) are considered white matter. A lot of the common MS sites of demyelination involve the Cranial nerves. If you have read many of my posts, you'll remember that I am always mentioning that this that or the other symptom are from lesions in the Cranial nerves.
The Cranial Nerves have an wide interaction with each other to give the brain far more information and control than the nerves do alone. They interact within the brainstem through a series of nerve hubs called nuclei (plural of nucleus). Through these nuclei we have greater understanding of what we see, can move our eyes in complex ways, have greater balance and coordination.
CN I - is the Olffactory Nerve -
What it does - this nerve comes directly off the brain and handles the entire job of the sense of smell.
What happens when MS attacks it - Changes in sense of smell can occur in MS, from partial or complete loss of smell to alterations in smell like smelling weird things that aren't there.
CN II - the Optic Nerve -
What it does - Yep, handles the whole process of sight and vision. As a sensory nerve, the Optic Nerve picks up the image in light and color and carries it backwards to the brain where the information is processed by several parts of the brain. This forms the images we see, and adds to the information that keeps us upright in space and helps us keep our balance. The information is also used in the cerebellum to help us with fine motor and coordination.
Lesions on this nerve from MS cause the condition Optic Neuritis, symptoms include decreased vision, pain behind the eye, pain with eye movements, loss of color saturation (vivid colors become paler or more grayed out), flashes of light, loss of parts of the field of vision
CN III - the Oculomotor (eye movement) Nerve
What it does - It's a motor nerve. This nerve handles 4 of the six muscles that allow the eyeball to move around, instead of staring straight ahead.
It also raises one of the major muscles of the upper eyelid on the same side. Alesion will cause the eyelid on the same side to droop.
It also has the function of working to control the pupil constriction to light and to close/far vision. Lesion can change our ability to bring objects at different distances into focus.
When there is a lesion on it it can cause double vision because the affected eye cannot move in coordination with the normal eye.
The eyelid on the same side can droop
The pupil on that side may not respond as promptly to light.
CN IV - the Trochlear Nerve
This nerve handles the muscle that allows the "opposite" eye to rotate using the supeior oblique muscle. This allows fine tuning of the eye movements other than just up/down and side-to-side. It is the only cranial nerve that crosses over to direct something on the OPPOSITE side of the face.
Lesion - double vision
CN V - the Trigeminal Nerve
This is the major sensory nerve for sensation to the face and the motor nerve for chewing. The Trigeminal Nerve also handles the sensation from the sinuses, from the outside surface of the eardrum, and from the meninges. This nerve has three main branches. ( It's name means "three roots) V1 brings sensation from the upper part of the face and eyelid, the temple and the forehead. It may reach as far as the top of the scalp. V2 is the mid-part of the face, cheek, nose. Also the upper teeth, gums,upper lip and inner cheek. V3 handles the sensation from the lower face, lower teeth and gums, and lower lip. It extends down to and slightly beyond the jawline.
Lesion - It is responsible for the sensations of numbness, tingling and PAIN (as in Trigeminal Neuralgia) seen in MS. There can be an alteration of sensation noted both preceeding and following an episode of TN. A lesion may cause inability to chew effectively or fatigue with chewing.
CN VI - the Abducens Nerve - This motor nerve handles the same side eye muscle attached to the outside eyeball and allow the eye to turn laterally to the side.
CN VII - The Facial Nerve - This nerve handles most of the muscles of the face and lips and around the eye. But it is not only a motor nerve. It is also a sensory nerve and a visceral nerve. (A visceral nerve causes actions in an organ of the body like causing a gland to secrete or causing the bowles to have peristalsis). It handles part of the control of the glands of the face. It also carries sensation from the ear, the middle ear and the interior of the eardrum. It handles taste for the anterior 2/3's of the tongue on the same side. When this nerve goes wonky you get a Bell's Palsy - Drooping of the side of the face, droopy eye, etc.
CN VIII - The Auditory Nerve - This is a sensory nerve responsible for Hearing and Balance (peripheral balance) Damage to this nerve can cause hearing loss and vertigo, and tinnitus.
I'll do the last 5 nerves later. Also some neuroanatomists claim there is a Nerve #0 which is responsible for the production of pheromones.
There are uncounted mnemonics for remembering the cranial nerves and there order. These range from odd to silly to downright slutty.
On Occasion Our Trusty Truck Acts Funny. Very Good Vehicle Any How.
On Old Olympus' Towering Tops A Friendly Viking Grew Vines and Hops
Only On Occasion, Touching The Amorous Female Virgin Goat Vacillates A Hand
OLympic OPium OCcupies TRoubled TRiathletes After Finishing VEgas Gambling VAcations Still High
Orange orangutans often try to avoid feeding angry gorillas very ancient hotdogs.
On Old Olympus' Tufted Top A Fat Armed German Viewed An Hop
Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly
Only Older Octogenarians That Take A Free Viagra Get Very Aroused Here
Oh, Oh, Onward Through The Airy Facade Viewing Gorgeous Vixens Acessorizing Hedgehogs
Another set of mnemonics helps to remember the nerves' purposes and to remember the types of information these nerves carry (Sensory, Motor, or Both) is thus:
Some Say Money Matters, But My Brother Says Big Brains Matter More.
Some Say Money Matters, But My Brother Says Big Boobs Matter More.
Small Ships Make Money, But My Brother Says Big Boats Make More.
Some Say Marilyn Monroe, But My Brother Says Bridgette Bardot Mmmm Mmmmm
I had been waiting to finish this, but decided a little was better than nothing.
Quix
Quix,
Great Stuff!! I honestly only read a tiny bit because I have eye pain and am waiting for my IV steroids but I know that I am going to be coming back to this when the pain/vision gets better.
Maybe you will have part #2 done by then ? No pressure the first half could last for weeks of reading.
Thanks again Erin :)
Great Stuff!! I honestly only read a tiny bit because I have eye pain and am waiting for my IV steroids but I know that I am going to be coming back to this when the pain/vision gets better.
Maybe you will have part #2 done by then ? No pressure the first half could last for weeks of reading.
Thanks again Erin :)
I misspoke in the second paragraph about the Swinging Light Test.
"In a test called the "Swinging Light test" this is what happens. The doctor slowly swings the penlight first into one eye. This should cause both pupils to constrict the same amount. Right? Then, the light is swung to the other eye. As it leaves the first eye and before it arrives at the other eye both pupils will start to dilate again. So when the light arrives at the second eye you will again see constriction. That is the normal response when everything is working correctly.
In optic neuritis the sick eye (one with ON) will not register as much light as a healthy eye. This is because the Optic Nerve (CN II) is damaged and not able to perfectly carry all of the light signal. So, when the light is shown in the good eye, both pupils will constrict, "maximally. When the light is moved to the affected eye (the one with ON) not so much light is signalled and the constriction is less marked and the eye may appear to "paradoxically" dilate. This is called the Marcus-Gunn pupil and is an afferent pupillary problem."
Jess - the perception of flashing lights is called photopsis or photopsia. Maybe that is what you heard.
The test where they cover one eye at a time might not use enough light (if they are depending on regular room illumination) to detect a Marcus Gunn pupil. I always used the cover test to detect a lazy eye. So it could be used for that I suppose. Not sure what he was doing.
A weird thing about optic neuritis is that, though it makes things seem blurry, it often does not affect the visual acuity. So, the sight might be normal on the Snellen Chart. Also, if there is blurriness it is not treatable with new glasses.
It sounds like the neuro sees all this as evidence of optic neuritis.
Wish I could say more.
Quix
"In a test called the "Swinging Light test" this is what happens. The doctor slowly swings the penlight first into one eye. This should cause both pupils to constrict the same amount. Right? Then, the light is swung to the other eye. As it leaves the first eye and before it arrives at the other eye both pupils will start to dilate again. So when the light arrives at the second eye you will again see constriction. That is the normal response when everything is working correctly.
In optic neuritis the sick eye (one with ON) will not register as much light as a healthy eye. This is because the Optic Nerve (CN II) is damaged and not able to perfectly carry all of the light signal. So, when the light is shown in the good eye, both pupils will constrict, "maximally. When the light is moved to the affected eye (the one with ON) not so much light is signalled and the constriction is less marked and the eye may appear to "paradoxically" dilate. This is called the Marcus-Gunn pupil and is an afferent pupillary problem."
Jess - the perception of flashing lights is called photopsis or photopsia. Maybe that is what you heard.
The test where they cover one eye at a time might not use enough light (if they are depending on regular room illumination) to detect a Marcus Gunn pupil. I always used the cover test to detect a lazy eye. So it could be used for that I suppose. Not sure what he was doing.
A weird thing about optic neuritis is that, though it makes things seem blurry, it often does not affect the visual acuity. So, the sight might be normal on the Snellen Chart. Also, if there is blurriness it is not treatable with new glasses.
It sounds like the neuro sees all this as evidence of optic neuritis.
Wish I could say more.
Quix
Thank you Quix!! This is a wonderful post!
Do you mind if I ask for your 2 cents? My neuro (an neuro-ophthalmologist) is pretty closed lipped during the exam and I find out most my info as he dictates to the PA at the end of the exam.
I had been telling my neuro about 2 eye issues:
1- about 3 weeks ago my husband noticed my pupils were huge, basically fully dilated, while in a well-lit room. This lasted over an hour, and was still there when I went to sleep, but was gone in the morning. I had complained of a headache, maybe from the extra light my pupils were letting in?
Then last Friday afternoon I was outside in the bright sunny day for a few minutes. When I went back inside, where it is much dimmer (we get morning sun in the house), I thought I was going blind! Everything was very blurry where I could only make out shapes. It was very dark and there was a blue tint to everything (I have blue eyes, if that means anything.) It lasted 5 minutes and then suddenly snapped back to normal. When I told my husband he thought it was my pupils not dilating when I went back inside.
And 2) For 3 days last week I would see flashes in my peripheral vision if I looked to the side, like camera flashes going off on either side of me. This went away after 3 days.
My neuro did repeat OCT and VER tests on me. My OCT was unchanged from April, showing slight optic nerve thinning on my left, but still within normal limits. The VEP in April showed an 8 millisecond delay in my left eye. The one on Monday showed a 10 millisecond delay.
He did not do the flashlight test, but he did put his hands up to cover one eye and switched back and forth, is that kind of the same test or something different?
My fundus exam has always been normal. When he was dictating to the PA, the PA mentioned something that sounded like "phototopis". I've tried looking online, and can't find anything. My neuro also said "Acute optic neuritis" and he has never said those words before, though I have seen him for eye issues the last few visits. My eyes just don't seem right, but they also did a regular "read the chart" eye exam on Monday and it was 20/20!
I'm sorry this is so long! I'm wondering, would what I have experienced the last few weeks be why my neuro said optic neuritis? I had gone to see him because the vertigo started back up last thursday, luckily it is mostly a low-level dizziness with the full vertigo flaring up 4-6 times a day & lasting 1-3 hours, so my neuro did not suggest steroids (whew! I'm not looking forward to doing those again!) but he did say he is 80% sure I have MS, up from 70% at my last visit. And he has suggested I start Copaxone, which I will be.
Thank you for your thoughts on these questions! And, thank you for the wonderful post!
~Jess
Do you mind if I ask for your 2 cents? My neuro (an neuro-ophthalmologist) is pretty closed lipped during the exam and I find out most my info as he dictates to the PA at the end of the exam.
I had been telling my neuro about 2 eye issues:
1- about 3 weeks ago my husband noticed my pupils were huge, basically fully dilated, while in a well-lit room. This lasted over an hour, and was still there when I went to sleep, but was gone in the morning. I had complained of a headache, maybe from the extra light my pupils were letting in?
Then last Friday afternoon I was outside in the bright sunny day for a few minutes. When I went back inside, where it is much dimmer (we get morning sun in the house), I thought I was going blind! Everything was very blurry where I could only make out shapes. It was very dark and there was a blue tint to everything (I have blue eyes, if that means anything.) It lasted 5 minutes and then suddenly snapped back to normal. When I told my husband he thought it was my pupils not dilating when I went back inside.
And 2) For 3 days last week I would see flashes in my peripheral vision if I looked to the side, like camera flashes going off on either side of me. This went away after 3 days.
My neuro did repeat OCT and VER tests on me. My OCT was unchanged from April, showing slight optic nerve thinning on my left, but still within normal limits. The VEP in April showed an 8 millisecond delay in my left eye. The one on Monday showed a 10 millisecond delay.
He did not do the flashlight test, but he did put his hands up to cover one eye and switched back and forth, is that kind of the same test or something different?
My fundus exam has always been normal. When he was dictating to the PA, the PA mentioned something that sounded like "phototopis". I've tried looking online, and can't find anything. My neuro also said "Acute optic neuritis" and he has never said those words before, though I have seen him for eye issues the last few visits. My eyes just don't seem right, but they also did a regular "read the chart" eye exam on Monday and it was 20/20!
I'm sorry this is so long! I'm wondering, would what I have experienced the last few weeks be why my neuro said optic neuritis? I had gone to see him because the vertigo started back up last thursday, luckily it is mostly a low-level dizziness with the full vertigo flaring up 4-6 times a day & lasting 1-3 hours, so my neuro did not suggest steroids (whew! I'm not looking forward to doing those again!) but he did say he is 80% sure I have MS, up from 70% at my last visit. And he has suggested I start Copaxone, which I will be.
Thank you for your thoughts on these questions! And, thank you for the wonderful post!
~Jess
Thank you, Quix!! That was a perfect explanation. I love understanding these details and having difficulty finding this information. Once again, I'd suggest this be part of a HP on ON. This is really great info and I so appreciate your time in giving such a thorough answer!
Thanks for great info, Quix. I've got symptoms for numbers 5 and 8 (confirmed with very abnormal AEPs for #8). Bilateral!
Anyway, a question--are those nuclei IN the brainstem, or just beside it? For some reason I always assumed the "nuclei" I've seen mentioned in relation to the vestibular nerve, e.g., are at the intersection of the brainstem and nerve, but then I have not really studied this.
And I did have that very weird crossover thing where left-side BPPV triggered what was almost surely a stapedial spasm in the right ear--which I think had to be a crossed wire in the brainstem itself?
Anyway, a question--are those nuclei IN the brainstem, or just beside it? For some reason I always assumed the "nuclei" I've seen mentioned in relation to the vestibular nerve, e.g., are at the intersection of the brainstem and nerve, but then I have not really studied this.
And I did have that very weird crossover thing where left-side BPPV triggered what was almost surely a stapedial spasm in the right ear--which I think had to be a crossed wire in the brainstem itself?
Have an Answer?
You are reading content posted in the Multiple Sclerosis Community
Top Neurology Answerers
Australia
ON
Queensland, Australia
Queen Creek, AZ
Find out how beta-blocker eye drops show promising results for acute migraine relief.
In this special Missouri Medicine report, doctors examine advances in diagnosis and treatment of this devastating and costly neurodegenerative disease.
Here are 12 simple – and fun! – ways to boost your brainpower.
Discover some of the causes of dizziness and how to treat it.
Discover the common causes of headaches and how to treat headache pain.
Two of the largest studies on Alzheimer’s have yielded new clues about the disease
