Here is a super important but very challenging question.
A 43 year old female walks into the neurology clinic looking very irritated.
She complains about feeling sharp, stabbing, electric pain on the right side of her face.
The pain suddenly started two weeks ago.
The pain is so excruciating that she can no longer laugh, speak or eat her meals.
She had to miss her work last week as a result. Her attacks last about 3 minutes and go away when she goes to sleep.
She typically has 2-3 attacks per day now.
A neurological physical examination shows no loss of crude touch, tactile touch or pain sensations on the left side of the face.
A light and accommodation reflexes are normal.
There is no drooping of the mouth, ptosis or anhidrosis noted.
Which of the following is the likely diagnosis for this patient's condition.
Answer choice A. Bell's palsy
Answer choice B. Cluster headache
Answer choice C. Trigeminal neuralgia
Answer choice D. Trigeminal cephalalgia
Or Answer choice E. Basilar migraine
Now take a moment to come to the answer by yourself before we go through it together.
Okay, this is a very important question.
Now, we know the patient's coming into a neurology clinic, endorsing some type of focal deficit and we did a neuro-exam.
So this is a neurology question.
This is really a 1-step question where you just have to take the consultation symptoms and just come to the diagnosis.
But even though, it's just a 1-step question, you absolutely need the question stem
because we have to pull all the information run and figure out the differentials to come to the correct answer.
So let's do that together now, well, looking at the question stem, we have a female patient.
And she's coming in with the chief complaint of having right sided face pain but the description of this pain is rather unique.
It is sharp, stabbing electric-like and it's isolated to just the right side of her face.
Now, with just that description, we have a pretty wild deferential diagnosis.
We could think about migraine, we could think about cluster headache, we could think about infection, etc.
So we really have to pay meticulous attention to the question stem and the details to come to the correct diagnosis.
And this is very important in USMLE exams.
When you have a 1-step question and they're simply asking you the diagnosis, you better double down and pay attention
because there is no easy question on USMLE, a 1-step question is when you really wanna pay attention to.
Now, let's try to look at the characteristic of the patient’s pain and try to help us narrow our diagnosis.
Now we can use the Socrates mnemonic to be able to understand what are the characteristics of the pain.
Now, the site it is the right side of the face.
The onset is two weeks and sudden.
The character is sharp, stabbing electric pain. There is no radiation.
No other associations.
The timing seems to be intermittent with two to three attacks a day, each one lasting about three minutes
and it seems that for exacerbating and relieving factors, sleep seems to relieve the pain
and for severity they describe it as excruciating which can be calculated as roughly ten out of ten pain.
Now, we need to see what answer we can actually come to base on this analysis of the patient symptoms.
Now, let's do this actually by trying to eliminate answer choices while going to the symptoms that we have.
Now, answer choice A here is Bell's palsy.
Now Bell's palsy is in which you have a cranial nerve seven deficit in which you could have a central or peripheral
but Bell's being a peripheral lesion in which you would have ptosis, forehead impairment and facial droop.
But the question says that there is no droop of her mouth and no ptosis, making Bell's Palsy unlikely.
Now in addition to Bell's palsy, ptosis can also be seen in cluster headache and trigeminal cephalagia
but this patient also does not have ptosis so it also as unlikely that the patient can have cluster headache,
answer choice B or Trigeminal cephalalgia, answer choice D.
Now, this patient characteristic of her pain is that it is sudden onset, intermittent and short time.
Now that's inconsistent with many of the other answer choices.
Now looking at answer choice E, basilar migraine.
These kind of patient actually have a gradual onset of their migraine with the prodrome and aura faces,
and the overall migraine for these patients last anywhere between 2 to 72 hours.
So that really doesn’t sound like what this patient having, so definitely makes answer choice E unlikely.
Now, let's try to even reinforce that you can eliminate the previously eliminated answer choices even more.
Now, Bell's palsy is a constant thing, it doesn’t come and go
so again the fact that it is intermittent makes Bell's palsy even more unlikely.
So answer choice A is even more unlikely and longtime of duration of symptoms
is more consistent with the cluster headache or trigeminal cephalalgia
and you can eliminate those even more now because these patients having short duration of pain.
Thus if by just eliminating all the other question and answers,
we can come to the conclusion that this patient has trigeminal neuralgia, answer choice C as the correct answer
and in many cases, USMLE wants you to do what we just did together
which is come to the correct answer by eliminating all the other answer choices.
Now, we can even support this by knowing that trigeminal neuralgia, often has relief of symptoms
with sleep and we can feel then confident with picking this answer choice.
Now, if you look at the image provided, we have the trigeminal nerve which is cranial nerve 5, V1, V2 and V3.
And you can see the three branches of the trigeminal nerve and the three dermatomal distributions of sensory for the trigeminal nerve.
Now, a few words on trigeminal neuralgia. Now, trigeminal neuralgia is a debilitating condition.
Patients with trigeminal neuralgia , the question stem says, the patient comes in looking very irritated,
they do, they are upset, they are angry, they're not happy patients
because this is a really challenging and painful condition and they describe the neuralgia
as sudden shock like or throbbing excruciating pain in the regions of the trigeminal nerve.
And interestingly, trigeminal neuralgia usually affects women and is often idiopathic.
Now, there are some cases and you should know this, in which you can have trigeminal neuralgia
from compression of the trigeminal nerve by the nearby superior cerebral artery or SCA
As this artery is exiting the pons in the brain stem.
Now there are other more rare causes of trigeminal neuralgia
including viral infections, multiple sclerosis, and even cerebellopontine angle tumors.
Now, the path of physiology of trigeminal neuralgia can be explained by compression of the trigeminal nerve
which can lead to focal demyelination and then subsequent hyper stimulation and excitability of the nerve fibers
which will lead to episodic episodes of severe pain.
Now again remember this, trigeminal neuralgia is usually unilateral, meaning on just one side of the face and often idiopathic and ideology.
Now, you may get this question, what is the first line treatment for trigeminal neuralgia
and the answer is carbamazepine or oxcarbazepine which are of course anti-epileptic drugs
but also used for controlling the symptoms of trigeminal neuralgia.
If you're ask if narcotics are appropriate, they are usually not recommended
because they don't treat the underlying condition they just masked it and of course if medical treatment fails,
you can get imaging and see if you have support for performing surgical approach of doing a SCA scaffold surgery to relieve the patients symptoms.