1/ “You don’t get points for having your needle in the right place if you don’t get a diagnosis.” When we biopsy the skullbase we work to get a diagnosis.
A sort of #tweetorial but more like a 🧵about our skullbase biopsy system. #FOAMed#medtwitter#neurosurgery#neurotwitter
2/ Unless the lesion is difficult to diagnosis w/FNA (ie, schwannoma), we begin by FNA w/an 18g draw needle & a 22g Quincke needle. We do not aspirate, b/c the skullbase is very vascular, & too much blood will be drawn up, making it difficult to tell if the sample is diagnostic.
3/ However, if we are not getting a diagnosis with FNA, we will move to a core. If it is a deep lesion, we will use the Biopince system, beginning with a 17g, 7 cm introducer. This is an example of IgG4 disease of the trigeminal nerve that failed FNA and required a core
4/ Through the 17g introducer, the 18g Biopince needle is inserted for biopsy. You need about 3.5cm of tissue depth to the lesion to support this system. If there is less tissue, there is not enough purchase to hold the introducer in place and it will sag.
5/ For superficial lesions, we change the introducer to a 16g Angiocath IV needle. It has a internal metal stylet, making it easy to steer. This a deep parotid lesion invading the masticator space requiring a core, but was too superficial to support the normal Biopince system.
6/ The Biopince needle fits perfectly into the 16g Angiocath. The tip of the Angiocath stops the Biopince from advancing further, so you will begin the throw for your core immediately from end of your introducer.
7/ The most important thing is to get the patient a diagnosis. I tell the pathologist "I can do this all day." We biopsy lesions until we are told samples are diagnostic. To prove a negative (ie infection not tumor), we sample at least 10 times to avoid undersampling.
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2/ fMRI is based on a principle called “neurovascular coupling.” This is the principle if there is increased neuronal activity in a region, there will be increased blood flow to that region to meet the increased demand
3/ Think of it like a baby crying because it is hungry—parents immediately rush to feed it. The increased oxygen demand of the neurons immediately brings increased fuel to feed it.
1/
Why is cranial nerve 6 uniquely affected by⬆️ intracranial pressure? Why is it special? A common question after the CN6 tweetorial.
Here is a maybe #tweetorial, but maybe a🧵about why CN6 is alone affected by ⬆️ pressure. #FOAMed#medtwitter#Medstudenttwitter#neurotwitter
2/ Think of the intracranial CSF space like a balloon, distended by CSF instead of air. Cranial nerves begin inside the balloon, and then they exit as they begin their extradural portion
3/ Most cranial nerves move immediately away from the CSF space after they exit—usually going out through their respective foramina. However, CN6 uniquely runs along the outside of the “balloon” in Dorello canal
1/ It is rare a patient tells you where their pathology is—but they do when they tell you they have a cranial nerve palsy—you just have to know where to look!
A #tweetorial about the Six Syndromes of the Sixth Cranial Nerve. #FOAMed#medtwitter#Medstudenttwitter@medtweetorials
2/ To understand the six syndromes, you have to know the anatomy of the 6th nerve. It starts in the brainstem, at the facial colliculus—what looks like the butt of the brainstem. It then travels anteriorly through the brainstem to exit out the ventral surface of the pons.
3/ It exits the brainstem at the inferior aspect of the pons—under what looks like pot belly of the pons and then travels anteriorly in the subarachnoid space towards the clivus
1/
My fellows complained they hate memorizing classifications, like LeFort. I thought, “There must be a better way—maybe understanding instead of memorizing.”
2/ To understand LeFort, you need to understand facial buttresses.
These are not true anatomic structures but a way of understanding facial structure.
Facial bones support facial structures like a table supports food, with legs (vertical buttresses) and table top (horizontal)
3/ In the face, the two main structures the buttresses are supporting are the orbits and the alveolar ridges of the maxilla and mandible supporting the teeth