Brain Stem Strokes

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BRAIN STEM STROKES:

Here's a brief discussion regarding the Ventral Midbrain Syndromes which I've gone through on 9th & 10th of May. Will update regarding the other syndromes in my further posts.


The posterior surface of midbrain has a Tectum portion & a Tegmental portion.
The Tectum portion consists of Corpora Quadrigemina & 4th cranial nerve
where as the Tegmental portion comprises of Floor of the 4th ventricle, Median Sulcus, Facial colliculus & Sulcus Limitans. 






Three important Ventral Midbrain Syndromes are  :
1) Weber syndrome
2) Claude syndrome
3) Benedikt syndrome


These occur due to the involvement of P1 segment of Posterior cerebral artery. 
Posterior Cerebral Artery is divided into P1 & P2 segment ( proximal & distal to Posterior communication artery) 








1) Weber Syndrome: 

 The lesion is at the level of crus cerebri, here you can see the location of the cortico spinal tract which is present in the middle 3/5th of the crus cerebri. 
The corticospinal tract crosses to the opposite side after crossing the pons & medulla leading to 

Contralateral Weakness & Ipsilateral 3rd nerve Palsy.

2) Claude Syndrome:
The lesion is at the Tegmental portion of the midbrain
Here, there is involvement of the dentatorubrothalamic pathway which start from the dentate nucleus in the cerebellus and reach the contralateral thalamus by decussating to the contralateral red nucleus.
Lesion at this area is the reason why these patients end up having contralateral ataxia ( as it involves the cerebellum), you also see the patients having Ipsilateral 3rd nerve palsy and contralateral tremors due to the lesion involving the Red nucleus.

3) Benedikt Syndrome:

They usually say that Benedict is equal to Weber + Claude + thalamic features
In Benedicts Syndrome, the lesion involves both the tegmentum & the peduncle.
The lesion involves the red nuclues and the nigrostriatal pathway.


So here you end up seeing the patients presenting with Ipsilateral 3rd nerve palsy ( as seen in Weber & Claude) + C/L weakness ( As in Weber) + C/L Ataxia ( As seen in Claude) + Extrapyramidal symptoms such as Hemichorea and Hemiathetosis.

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