Base of peduncle
Basis pedunculi
The front part of each cerebral peduncle of the midbrain, a thick band of descending fibres from the cerebral cortex.
At a glance
- English
- Base of peduncle
- Latin (TA2)
- Basis pedunculi
- System
- Brain and spinal cord
- Region
- Head
- Side
- Paired, left and right
About the base of peduncle
Each half of the midbrain has a cerebral peduncle, and the base of the peduncle (basis pedunculi), often called the crus cerebri, is its most anterior part. Seen from below, the two bases form large rope-like columns that emerge from the underside of the cerebral hemispheres and converge as they pass down into the pons. The deep notch between them is the interpeduncular fossa.
Behind each base lies the substantia nigra, a sheet of pigmented grey matter that separates it from the tegmentum. The base itself is white matter, made of fibres that have come down from the cortex through the internal capsule. The corticospinal and corticonuclear fibres occupy roughly its middle part, with the face represented medially and the leg laterally. Medial to them run frontopontine fibres, and lateral to them fibres from the parietal, temporal and occipital lobes to the pontine nuclei.
Its surroundings are important. The oculomotor nerve emerges from the medial side of the peduncle into the interpeduncular fossa. The optic tract winds round its lateral side, and the posterior cerebral artery curves around it on the way to the back of the brain.
A lesion of the base on one side causes weakness of the opposite side of the body. If it also involves the oculomotor fibres passing through, it gives Weber's syndrome: an oculomotor palsy on the same side with paralysis of the opposite limbs. When the medial temporal lobe herniates under the tentorium, the opposite peduncle may be pushed against the tentorial edge, producing weakness on the same side as the lesion, a classic false localising sign.
Function and supply
- Function
- Carries descending fibres from the cerebral cortex to the brainstem, the spinal cord and the pontine nuclei.
- Blood supply
- Mainly branches of the posterior cerebral artery and the posterior communicating artery, with a contribution from the anterior choroidal artery.
Anthromica
See the base of peduncle where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
