Also called pons, it is a part of brain cadres.It is located between the medulla oblongata and the midbrain, with transverse sulcus dividing the anterior and posterior edges.The ventral area of the pons is the base of the pons. There are a large number of transverse fibers connecting the cerebellar hemisphere, and there are also some longitudinal nerve fibers.
The ventral side of the pons is wide and distended, called the pontine base.Its upper edge is connected with the brain foot of the midbrain;The lower edge is connected with the medulla oblongata by the pons medullary sulcus.In the pons medullary sulcus, abducens nerve, facial nerve and vestibulocochlear nerve root come out of the brain from inside to outside.There is a longitudinal shallow groove in the middle of the ventral surface, called the basilar groove, which contains the basilar artery.There are a lot of transverse fibers on the ventral side, which gradually narrow to both sides, move to the middle cerebellar peduncle or pontine arm, and turn to the dorsal side to enter the cerebellum.There is a large trigeminal nerve root attached to the migration site, which is usually regarded as the boundary between the ventral side of the pons and the middle cerebellar peduncle.The basal part of pons is a relay station connecting the cerebellar cortex and the greater cortex.
The intersection of the medulla oblongata, pons and the posterior cerebellum is clinically called the pons cerebellum triangle, where the vestibulocochlear nerve is located, which is of great clinical significance. When there is a tumor pressing the vestibulocochlear nerve fibers, hearing impairment and cerebellar damage may occur. At the same time, the tumor may also compress the facial nerve, trigeminal nerve, glossopharyngeal nerve and vagus nerve, resulting in corresponding symptoms.The front end of the pons is narrow and thin, which is the transitional part between the pons and the midbrain, called the rhombocephalic isthmus. Here we can see the left and right upper cerebellar feet, or the combined arms, running forward and down from the cerebellum.There is an anterior medullary velum between the left and right combined arms. After the trochlear nerve crosses in the anterior medullary velum, it exits the brain on both sides of the midline, bypasses the brain foot, and then reaches the ventral side of the brain stem.The trochlear nerve is the only pair of nerves that exit from the back of the brain stem.
The cranial nerves coming in and out of the pons include trigeminal nerve, abducent nerve, facial nerve and vestibulocochlear nerve.The trigeminal nerve roots enter and exit the pons at the junction between the base of the pons and the middle cerebellar peduncle. The roots of the abducent nerve, facial nerve and vestibulocochlear nerve are located in the pons sulcus of the medulla oblongata from the inside out.The abducent nerve is on the medial side, 4-5cm away from the midline, and the vestibulocochlear nerve is on the outermost side, just at the cerebellopontine triangle.The facial nerve is on the medial side of the vestibulocochlear nerve, and there is a small intermediate nerve between it and the vestibulocochlear nerve.
Pontine hemorrhage
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It often occurs suddenly, with severe headache, dizziness, vomiting, falling to the ground, and loss of consciousness within a few minutes, leading to a deep coma.Hemorrhage often starts from one side of the pons and presents as cross paralysis, that is, paralysis of the bleeding side and flaccid paralysis of the opposite upper and lower limbs.The head and eyes turned to the non bleeding side in the shape of "staring paralyzed limbs".A few patients (about 20%) can be limited to such small area bleeding;Most of them quickly spread to the opposite side, with paralysis on both sides of the face and limbs, positive pathological signs on both sides, head and eyes returning to the center, and pupil on both sides extremely narrowed, showing needle like appearance (this is a characteristic performance, caused by the damage of sympathetic nerve fibers in the pons);Frequently persistent high fever can affect the medullary respiratory center and cause early dyspnea.The critically ill patients quickly developed irregular breathing, decreased blood pressure, dilated bilateral pupils, and disappeared light reflex, leading to high mortality.
Diagnostic points of pontine hemorrhage:
1) Middle aged and elderly patients, with acute onset and rapid progress, have risk factors for cerebrovascular disease, such as hypertension, atherosclerosis, etc;
2) The characteristic clinical manifestations of severe pontine hemorrhage: at the onset of the disease and within 24 hours, there may be disturbance of consciousness, central high fever, respiratory disorder, quadriplegia or cross paralysis, pinprick like pupil reduction, ocular floating, etc. The clinical symptoms are complex, and most of them are complicated with stress gastrointestinal bleeding, infection, multiple organ failure and other complications;
3) The diagnosis mainly depends on imaging examination, such as brain CT and MRI. The location and volume of bleeding are the main factors affecting the prognosis.
