1. A Mesencephalon Decathlon
Jim Thorpe won decathlon during 1912 olympics in Stockholm when King Gustav V of sweden calle dhim the world’s greatest athlete.
Jim Thorpe
Gold medal in the 1912 Olympic decathlon

2. Questions What are the 3 primary brain vesicles?
What are the corpora quadrigemina?
Which anatomic structures comprise the basis pedunculi?
What is Claude syndrome?
What is a rubral tremor?

3. Outline Internal anatomy Embryology External anatomy Vascular supply
Stroke syndromes
Herniation syndromes

4. Embryology

5. 1 of 3 primary brain vesicles
Prosencephalon
Mesencephalon
Rhombencephalon

6. Intermediate zone gives rise to alar and basal plates
Alar = colliculi, red nucleus and substantia nigra
Basal = general somatic efferent (CN III & IV) and general visceral efferent (E-W nucleus)
Crus cerebri arise from cells outside the mesencephalon

7. External Anatomy

8. Crus cerebri
Bordered anteriorly by optic tract
CN III exit medial edge of crus cerebri and pass through interpeduncular fossa

9. Corpora quadrigemina = 4 colliculi CN IV marks midbrain/pons junction
SC brachium leads to pulvinar nucleus
IC brachium leads to MGB
Corpora quadrigemina = quadruplet bodies

10. Anterior subarachnoid space = interpeduncular cistern
Posterior subarachnoid space = quadrigeminal cistern

11. Internal Anatomy

12. Cerebral peduncle = crus +basis pedunculi
3 divisions
Tectum (roof)
Tegmentum (floor)
Basis pedunculi (crus cerebri + substantia nigra)
Cerebral peduncle = crus +basis pedunculi

13. Ascending and descending pathways

14. Caudal Midbrain
Inf Colliculi receive auditory input from lateral lemniscus
PAG involved in pain modulation (connections to thalamus, hypothalamus and somatosensory input)
Fronto-, parieto-, occipito- & temporopontine fibres project to pons and enter MCP
Lat lemniscus ascends from cochlear nuclei in rostral medulla
SCP cerebellar output to RN, thalamus, but also pons and medulla

15. Caudal Midbrain
CN IV axons pass postero-lateral, crossing midline

16. Somatotopographic organization of the medial lemniscus

17. Rostral Midbrain SN Pars compacta = output to corpus striatum
Pars reticulata = output to thalamus
SN=dopaminergic soma have melanin
RN=dnese vascularity, so pink
Retiucara = also sup colliculus & pontine reticular formation

18. Rostral Midbrain RN Input from contra cerebellum & ipsi cortex
Rubrospinal and rubro-olivary tracts

19. Diencephalon-mesencephalon junction
Edinger-Westphal nucleus
Output to ciliary ganglion
Input from pretectal neuclei

20. Diencephalon-mesencephalon junction

21. Reticular nuclei Raphe nuclei
Part of ascending reticular activating system
Responsible for alert, wakeful state
Raphe nuclei
Modulate activity in sleep/dream cycles

22. Vascular Supply
Stroke Syndromes
Herniation Syndromes

23. Vascular supply Branches of SCA and PCA
Lateral midbrain also supplied by anterior choroidal artery (branch of ICA)

24. Weber Claude Benedikt Ipsi CN III, contra bulbar motor
Ipsi CN III, contra tremor, ataxia and incoordination
Benedikt
Weber + Claude
Claude takes out RN and cerebellothalamic fibers as well

25. Central/transtentorial herniation Upward cerebellar herniation
May lead to
Cerebellar stroke from SCA occlusion
Hydrocephalus from aqueduct compression

26. Uncal herniation Lesion most often in temporal lobe
Ipsi CN III is often earliest sign

27. Questions What are the 3 primary brain vesicles?
What are the corpora quadrigemina?
What anatomic structures comprise the basis pedunculi?
What is Claude syndrome?
What is a rubral tremor?

28. Rubral tremor (aka Holme’s tremor)
A coarse, slow (4Hz) tremor, especially present in the upper extremities, that is found at rest, postural and intention.

29. The End