Neuroradiology has one of the deepest wells for obscure trivia. A lot of neuro is differential diagnosis, which I’ve stated over and over again, makes for a bad multiple-choice question. I think the questions will mainly fall into two categories
(1) Anatomy – Aunt Minnie – What is it? and
(2) Associated syndrome trivia
There is a ton of anatomy that can be asked on a multiple-choice test. My idea is to break it down into three categories:
(1) soft tissue – brain parenchyma (including normal development),
(2) bony anatomy – which is basically foramina, and
(3) vascular anatomy.
Soft Tissue Brain Anatomy:
Central Sulcus –
This anatomic landmark separates the frontal lobe from the parietal lobe. Old school grey-bearded Radiologists (likely the ones who are important enough to write test questions) love to ask how you find this important structure. There are about ten ways to do this, which brings me to the main reason this is a great pimping question.
Even if you can name nine ways to do it; they can still correct you by naming the 10th way. I noticed during my time as a “trainee” that Attendings tend to be excellent at knowing the answers to the Questions they are asking. Practically speaking, this is the strategy I use for findings the central sulcus:
- Pretty high up on the brain, maybe the 3rd or 4th cut, I find the pars marginalis. This is called the “pars bracket sign”
- because the bi-hemispheric symmetric pars marginalis form an anteriorly open bracket. The bracket is immediately behind the central sulcus. This is present about 95% of the time
- it’s pretty reliable
Central Sulcus Trivia – Here are the other less practical ways to do it.
1. Superior frontal sulcus / Pre-central sulcus sign: The posterior end of the superior frontal sulcus, joins the pre-central sulcus.
2. Inverted omega (sigmoid hook) corresponds to the motor hand
3. Bifid posterior central sulcus: Posterior CS has a bifid appearance about 85%
4. Thin post-central gyrus sign – The precentral gyrus is thicker than the postcentral gyrus (ratio 1 : 1.5).
5. Intersection – The intraparietal sulcus intersects the postcentral sulcus (works almost always) Midline sulcus sign – The most prominent sulcus that
6. Midline is the central sulcus (works about 70%)
- The inverted omega (posteriorly directed knob) on the central sulcus / gyrus designates the motor cortex controlling hand function.
- ACA territory gets legs, MCA territory hits the rest.
Normal Cerebral Cortex:
As a point of trivia, the cortex usually is 6 layers thick, and the hippocampus usually is 3 layers thick. I only mention this because the hippocampus can look slightly brighter on FLAIR compared to other cortical areas, and this is the reason why (supposedly).
Dilated Perivascular Spaces (Virchow-Robins):
These are fluid-filled spaces that Accompany perforating vessels. They are a normal variant and very common. They can be enlarged and associated with multiple pathologies; mucopolysaccharidoses (Hurlers and Hunters) ,”gelatinous pseudocysts” in cryptococcal meningitis, and atrophy with advancing age.
They don’t contain CSF but instead have interstitial fluid. The common locations for these are: around the lenticulostriate arteries in the lower third of the basal ganglia, in the centrum semiovale, and in the midbrain.
Just a quick refresher on this. You have two lateral ventricles that communicate with the third ventricle via the interventricular foramen (of Monro), which in turn communicates with the fourth ventricle via the cerebral aqueduct.
The fluid in the fourth ventricle escapes via the median aperture (foramen of Magendie), and the lateral apertures (foramen of Luschka). A small amount of fluid will pass downward into the spinal subarachnoid spaces, but most will rise through the tentorial notch and over the surface of the brain where it is reabsorbed by the arachnoid villi and granulations into the venous sinus system. Blockage at any site will cause a noncommunicating hydrocephalus. Blockage of reabsorption at the villi I granulation will also cause a noncommunicating hydrocephalus
These are regions where the arachnoid projects into the venous system allowing for CSF to be reabsorbed. They are hypodense on CT (similar to CSF), and usually round or oval. This round shape helps distinguish them from clot in a venous sinus (which is going to be linear). On MR they are typically T2 bright (iso to CSF), but can be bright on FLAIR (although this varies a lot therefore probably won’t be tested). These things can scallop the inner table (probably from CSF pulsation)
• Cavum Septum Pellucidum –
Seen in 100% of preterm infants, 80% of term infants, and 15% of adults. Rarely, can dilate and cause obstructive hydrocephalus
• Cavum Vergae –
A posterior continuation of the cavum septum pellucidum (never exists without a cavum septum pellucidum)
• Cavum Velum lnterpositum –
Extension of the quadrigeminal plate cistern to foramen of Monro. Seen on sagittal as above the 3rd ventricle and below the fornice
The basal cisterns are good for two things
(1) looking for mass effect and
(2) Anatomy questions.
Some people say the suprasellar cisterns look like a pentagon. The five comers of the star lend themselves easily to multiple-choice questions: the top of the star is the interhemispheric fissure; the anterior points are the Sylvian cisterns and the posterior points are the ambient cisterns. The quadrigeminal plate looks like a smile.