Case 1
Question 3
Name four common or important variants of the persistent carotid-vertebrobasilar anastomoses. (4)
1. Persistent trigeminal artery
• arises from proximal cavernous ICA
• most common persistent carotid-vertebrobasilar anastomosis
• two types – lateral and medial
Saltzman classification
type I: absent ipsilateral posterior communicating artery
type II: fetal origin of ipsilateral posterior communicating artery
2. Persistent otic (acoustic) artery
• arises from petrous ICA
• rare, as it is the first anastomosis to regress
3. Persistent hypoglossal artery
• arises from cervical ICA at C1 to C3 levels
4. Persistent proatlantal artery
• type I arises from internal carotid artery
• type II arises from external carotid artery
Case 2
Question 2 – Internal auditory canal
Transverse MRI T2 SPACE of the internal auditory canals.
c) What other structures pass through the internal auditory canal? (3)
• Facial nerve (CN VII): nervus intermedius branch and motor root
• Vestibulocochlear (CN VIII): cochlear, inferior and superior vestibular nerve
• Labyrinthine artery (branch of AICA or basilar)
• Vestibular ganglion
d) What structures form the horizontal and vertical divisions of the lateral portion of the internal auditory canal? (2)
Falciform ligament
Bills bar
e) Describe the position of the structures in the lateral portion of the internal auditory canal? (4)
Anterosuperiorly: Facial nerve (including nervus intermedius)
Anteroinferiorly: Cochlear branch of vestibulocochlear
Posterosuperiorly: Superior vestibular branch of vestibulocochlear
Posteroinferiorly: Inferior vestibular branch of vestibulocochlear
Question 3 – Thyroid Gland
Name five common or important variants of the thyroid gland excluding vascular variants. (5)
• Ectopic thyroid tissue
• Pyramidal lobe extending to base of tongue
• Thyroglossal cyst or fistula
• Tubercle of Zuckerkandl
• Recurrent laryngeal nerves may pass medial, lateral or through thyroid ligaments
Normal variant answers not accepted:
• Thyroid ima artery
• Absent inferior thyroid arteries
Case 3
Question 3
a) List the vertebral levels of the conus medullaris in the fetus, neonate and adult. (3)
Neonate: L5 and sacrum
Feotus (term): L2 – L3
Adult: L1 – L2
Read more: https://pubmed.ncbi.nlm.nih.gov/7933017/
b) Which side and level does the artery of Adamkiewicz most commonly arise? (2)
Most commonly arises on the left (80%)
Most commonly arises at the 9th – 12th intercostal artery (70%)
Case 4
Question 2 – Lung
e) Name the segments of the left upper lobe. (4)
Apicoposterior segment
Anterior segment
Superior lingular segment
Inferior lingular segment
f) Name the segments of the left lower lobe. (4)
Superior segment
Anteromedial segment
Lateral segment
Posterior segment
Question 3
Name five common or important variants of the coronary arteries. (5)
• Left dominant variant, large left circumflex supplies posterior interventricular artery
• Left coronary artery supplying SA nodal branch (40%)
• LCx supplying AV node
• Coronary artery arising from non-coronary sinus
• Co-dominance of the arteries
• Ramus intermedius – an additional artery arising at the bifurcation of the left main artery
Case 5
Question 3
Name five common or important variants of the inferior vena cava. (5)
• Absence of IVC (entire or only the infrarenal segment)
• IVC duplication
• Azygos continuation of the IVC
• Left-sided IVC
• Persistent left-sided IVC – may join left renal vein
• Circumcaval ureter
• Circumaortic venous collar/left renal vein
• IVC webs
• Extrahepatic portocaval shunt (Abernethy malformation)
• Marsupial cava
• Preaortic IVC/iliac vein confluence
Case 6
Question 3
Name five common or important variants of the inferior mesenteric artery. (5)
• doubled IMA
• absent IMA
• common trunks (e.g. left colic and rectosigmoid, rectal and colosigmoid)
• absent left colic branch
• Arc of Riolan (SMA/IMA connection)
Case 7
Question 3
Name five common or important variants of the carpal bones. (5)
• Carpal coalition (may be osseous, fibrous or cartilaginous)
– Luno-triquetral (most common)
– Capitohamate
• Bipartite carpals (carpus divided into two separate bones)
– Scaphoid most common
– Scaphoid > triquetrum > pisiform
• Aplasia/absence of a carpus
• Accessory ossicles (1%)
– Lunula – between TFCC and triquetrum
– Os styloideum – dorsal surface of 2nd and 3rd metacarpal bases
– Os triangulare – distal to ulnar fovea
– Os trapezium secondarium – medial to trapezius
– Os pilunate – dorsal to lunate
– Os hamuli proprium
Case 8
Question 2 – Pelvis
e) Describe the blood supply to the femoral head. (3)
• Medial femoral circumflex artery – from deep femoral artery
• Lateral femoral circumflex artery – from deep femoral artery
• Artery to ligamentum teres – branch from obturator artery (branch of internal iliac artery)
• Ascending cervical branches giving rise to retinacular arteries
Question 3 – Sciatic nerve
List five common or important variants of the sciatic nerve. (5)
Variations in the common peroneal and tibial branches:
• Common peroneal nerve piercing piriformis muscle and tibial nerve exiting below
• Common peroneal nerve travelling above piriformis muscle and tibial nerve below
• Common peroneal nerve travelling above piriformis muscle and tibial nerve piercing piriformis muscle
• Both common peroneal nerve and tibial nerve travelling below piriformis muscle separately
• Sciatic nerve courses over the piriformis muscle
• Sciatic nerve pierces piriformis muscle