Mid brain anatomy and vascular syndromes

Mid brain anatomy and vascular syndromes- Dr Pallav Jain

1. Mid brain Syndromes PRESENTER- DR.PALLAV JAIN DM RESIDENT(NEUROLOGY) GMC,KOTA

2. Introduction The midbrain is the proximal brainstem B ound rostrally by the diencephalon (thalamus and hypothalamus) and adjoined by the pons along its caudal aspect O culomotor and trochlear nerves originate from this level of the brainstem.

3. Anatomy of the Mesencephalon Rostral boundary -superior colliculi Caudal boundary is the plane just caudal to the inferior colliculi . M idbrain Dorsal tectum Central tegmentum Ventral midbrain

4. D orsal tectum - quadrigeminal plate as well as additional gray matter and fiber tracts residing dorsal to the cerebral aqueduct Tegmentum- ascending and descending tracts, reticular nuclei,cranial nerve nuclei. Ventral- cerebral peduncles, substantia nigra , crus cerebri , and corticobulbar fibers

5. LEVEL OF INFERIOR COLLICULUS Inferior colliculus -Role in the auditory pathway White matter tracts-sensory fibers within the medial lemniscus, trigeminal lemniscus,and spinothalamic tracts Brachium conjunctivum – decussation of cerebellar axons arising from the superior cerebellar peduncles MLF- eye movement(CN-3,CN-4,CN-6) Trochlear nucleus-residing midline and ventral to the Cerebral aqueduct

6. Level of the Superior Colliculus. The superior colliculus nuclei reside within the tectum The tegmentum-several nuclear bodies, with the red nucleus and oculomotor complex Continuations of the previously described white matter tracts within the tegmentum at the level of the inferior colliculus

7. Ventral Midbrain The ventral midbrain appears similar at both the level of the superior and inferior colliculi. Principle structures within this region include the cerebral peduncle and the substantia nigra

8. Vascular Supply of the Mesencephalon Basilar Posterior cerebral Superior cerebellar Three Zones Inferior colliculus Superior colliculus Pretectal levels Medial and lateral zones

9. Medial zone B asilar artery and its paramedian branches . Lateral Zone I nferior colliculus-superior cerebellar artery. Superior colliculus-posterior cerebral artery. Superior colliculus and adjacent tectum- superior cerebellar artery. Pretectal level- posterior cerebral artery.

10. Vascular supply of the midbrain at the level of the superior colliculus

11. Midbrain Syndromes Lesions within the midbrain may result in distinct syndromes G iven the close proximity of these vital nuclei and fiber tracts D istinct syndromes often result in overlapping symptomatology

12. Parinaud’s Syndrome( D orsal midbrain syndrome) C ompression of the rostral midbrain and pretectum near the level of the superior colliculus U sually due to mass effect from an adjacent pineal tumor Limited upward gaze is the distinguishing symptom. Downward gaze is often preserved. Patients may have a downgaze at rest, known as the “setting sun” sign. P seudo Argyl Robertson pupil L id retraction and convergence-retraction nystagmus

13. Claude’s Syndrome. Result of dorsal tegmentum infarction Ipsilateral oculomotor nerve palsy with contralateral cerebellar ataxia Involvement of the cranial nerve III nucleus and/or nerve fibers leads to oculomotor nerve palsy. Insult to the red nucleus, brachium conjunctivum , or fibers of the superior cerebellar peduncle results in incoordination and cerebellar hemiataxia

14. Benedikt’s Syndrome. Lesion within the tegmentum of the midbrain Incoordination and oculomotor nerve palsy due to involvement of the superior cerebellar peduncle and/or red nucleus, as well as the oculomotor nucleus. D amage to the corticospinal tract resulting in contralateral hemiparesis is the distinct finding. I nfarcted branches of the posterior cerebral artery

15. Weber’s Syndrome. Infarction of the ventromedial midbrain P aramedian branches of either the basilar artery or the posterior cerebral artery Oculomotor nucleus and/or fibers,cerebral peduncle I nvolvement of cranial nerve III- eye deviation (down and out), diplopia, ptosis, and afferent pupillary defect . Contralateral hemiparesis and lower facial weakness

16. Other possible findings When the midbrain infarct involves the short circumflex branches and is ventrolateral in the midbrain involving only the cerebral peduncle, there can be sparing of the 3 rd nerve Contralateral parkinsonian rigidity from involvement of the substantia nigra .

17. Nothnagel’s Syndrome. They result from extension of the lesion to the oculomotor nuclear complex and superior cerebellar peduncles. unilateral or bilateral oculomotor nerve paralysis and ipsilateral cerebellar ataxia [2, 13]. These symptoms are due to a lesion within the midbrain tectum involving the quadrageminal plate. Pathologically , Nothnagel’s syndome has been associated with mass occupying lesions of the midbrain

18. Nothnagel Syndrome.

19. Question & Answers

20. Claude syndrome This patient presented with downward abduction of the left eye and right leg incoordination with poor gait

21. Benedikt Syndome Patient presented with 3 rd nerve palsy + C/L ataxia + C/l Hemiparesis

22. Weber Syndrome

23. Inferior and superior colliculi are present in which part of the mid brain? Tectum Tegmentum Ventral midbarain Substantia Nigra

24. Thank You

25. PARAMEDIAN VESSELS A rise from the origins of the posterior cerebral arteries T halamoperforating arteries (supplying the thalamus) P eduncular arteries (supplying the medial peduncles and the midbrain tegmentum, including the oculomotor nucleus, the red nucleus, and the substantia nigra ).

26. CIRCUMFERENTIAL ARTERIE The posterior choroidal arteries, which supply the cerebral peduncles, the lateral superior colliculi, the thalamus, and the choroid plexus of the third ventricle. The anterior choroidal arteries- which in some cases help supply the cerebral peduncles as well as supramesencephalic structures. The posterior cerebral arteries, which also give rise to some mesencephalic branches