DISCUSSION

The midbrain (mesencephalon) lies between the pons and the diencephalon.

Ventral view. The ventral view reveals two prominent bundles of fibers converging onto the pons. These are the cerebral peduncles, or, as they are alternatively called, the cruracerebri (singular: crus cerebri). The groove between the peduncles, known as the interpeduncular fossa, is the site of emergence of the two oculomotor nerves (CN III) from the brainstem. The cerebral peduncles disappear caudally as they enter the pons; rostrally, they are encircled by the optic tracts before entering the cerebral hemispheres.

Dorsal view. The dorsal aspect of the midbrain (the midbrain tectum, i.e., “roof”) contains four protrusions collectively termed the quadrigeminal plate. Visual information is processed in the upper two protrusions (the superior colliculi), while auditory information is processed in the lower two protrusions (the inferior colliculi), which are somewhat smaller. The trochlear nerve (CN IV) emerges from the brainstem just below the inferior colliculus on either side and then courses ventrally around the cerebral peduncle. It is the only cranial nerve that emerges from the dorsal aspect of the brainstem.

Lateral view. The two small protrusions lying lateral to the quadrigeminal plate are the medial geniculate body (an auditory relay area) and the lateral geniculate body (a visual relay area). The geniculate bodies are components of the thalamus and thus belong not to the brainstem but to the diencephalon.

Mesencephlon supplied by

Lesions in midbrain had several syndromes, which is presentated in table below.

In this case, a male patient aged 66 years old with a diagnosis established from history, physical

examination and investigation at admission and during daily follow ups. He suffers from

weakness of the right limbs, which he can barely move the right arm and leg. From Physical

examination found hemiparesis dextra and paresis cranial nerve VII and XII dextra central type

and paresis cranial nerve III sinistra partial. According to patient’s signs and symptoms are

closed enough to webber syndrome which is causing alternans hemiparesis and left

occulomotorius nerve palsy (ptosis), but there is no involve extraooccular muscle and pupils.

Patient’s diagnose before and after brain CT-scan was not the same, where from the CTscan

shows multiple lacunar infarct on bilateral ganglia basalis and bilateral lateral periventricle. But

its doesn’t fit the symptoms from this patient. Two days later patient had MRI examination and

we found hyperintense lesion in left ventromedial mid-brain (DWi) which is fit with patient

symptoms.This lesion caused by vascular event to basilary artery branch (posterior cerebral

arteries).

Management in acute phase of mesencephalon infarction were the same with

other brain infarction. In brain infarctionwe give anti platelets aggregationandmetabolit

activator. For antihypertensionin acute ischaemic stroke lowering the blood pressureis 15

% (systolic and diastolic) in first 24 hours if Sistolic Pressure (SBP) >220 mmHg or

systolic pressure (DBP) > 120 mmHg. Drug of choice antihypertension for stroke are

labetalol, nitropaste, nitroprusside, nicardipine, or Diltiazem.

In this patient we give aspilet 2 x 80 mg (po) and citicholin 2 x 1000 mg (po) and we

don’t give any antihypertension in first 5 day.

Conclusion

A 66 years old male has been diagnosed hemiparesis alternans which has clinical

manifestations due to lesion in the left ventromedial mid-brain.Characterized by

hemiparesis contralateral, ipsilateral CN III palsy. Result from a lesion of the posterior

cerebral arteries that supply the area of ventromedial mesencephalon. Management in this

patient were similar with others brain infarction.