GOLOVNOGO MOZGA BRIDGE [pons (PNA, JNA), pons Varolii (BNA); synonym varoliyev bridge] — the part of a brain trunk which is a part of a metencephal (metencephalon).
The bridge between a medulla and legs of a brain is located, and on each side passes into average cerebellar legs (fig. 1). From the basis of a brain the bridge represents a dense white shaft the sizes of 30 X 36 X 25 mm. The front surface of the bridge convex, is turned forward and down and prilezhit on a base of skull to a slope. In the middle of a front surface there passes the basilar furrow (sulcus basilaris), in a cut the basilar artery (a. basilaris) which is the main source of blood supply of M. of of m lies.
Behind the bridge of a brain a furrow between a myelencephalon, on the one hand, roots of the taking-away, facial, intermediate and preddverno-cochlear nerves leave the bridge and an average cerebellar leg — with another, consistently.
The back surface of the bridge is turned up and kzad, into a cavity of the fourth ventricle, and outside is not visible since it is covered with a cerebellum. It forms an upper half of a bottom of a rhomboid pole.
On cross (frontal) sections of M. of of m (fig. 2) distinguish more massive front (ventral) part (pars ant. pontis), or basis (basis pontis, BNA), and small back (dorsal) part (pars post, pontis), or tire (tegmentum, BNA). As border between them serves the trapezoid body (corpus trapezoideum) formed preferential by shoots of cells of a front cochlear kernel (nucleus cochlearis ant.). Accumulations of nervous cells form front and back kernels of a trapezoid body (Gudden's kernel). The forefront of the bridge contains hl. obr. nerve fibrils, between to-rymi are scattered numerous small accumulations of gray matter — a kernel of the bridge (nuclei pontis). In kernels of the bridge fibers of a cortical and bridge way (tractus corticopontini) and a collateral from the passing pyramidal ways reach a limit. Shoots of cells of kernels of the bridge form a mostomozzhechkovy way, fibers to-rogo come over preferential to the opposite side and are cross fibers of the bridge (fibrae pontis transversae). The last form average cerebellar legs (pedunculi cerebellares medii).
The tail of the bridge (tire) is much thinner. It contains a reticular formation (formatio reticularis) and kernels V, VI, VII, VIII pairs of cranial nerves. At the level of the middle of the bridge the motive kernel of a trifacial is located (nucleus motorius n. trigemini), and a little lateralny — an upper sensitive kernel (nucleus sensorius sup.). Fibers from sensory cells of a trigeminal node approach the last, to-rye as a part of a sensitive root join substance of the bridge on border him with an average cerebellar leg. To a sensitive root prilezhit the motive root representing shoots of cells of a motive kernel of a trifacial.
At the level of a front hillock the kernel of the taking-away nerve is located; nearby, in a reticular formation, there is a motive kernel of a facial nerve, shoots of cells to-rogo create the knee which is bending around a kernel of the taking-away nerve. Behind a motive kernel of a facial nerve there is an upper slyunootdelitelny kernel (nucleus salivatorius sup.) and knaruzh from the last — a kernel of a single way (nucleus tractus solitarii). In nizhnelateralny department of a tire of the bridge kernels of an eighth cranial nerve (item vestibulocochlearis) are located. On sides of a trapezoid body there are upper olives. Shoots of cells of an upper olive (oliva sup.) make a lateral loop (lemniscus lat.), between fibers of the last the kernel of a lateral loop is located. (nucleus lemnisci lat.). Also shoots of cells of a back kernel of a cochlear nerve are a part of a lateral loop (nuci, cochlearis post.), kernels of a trapezoid body and kernel of a lateral loop.
Knutri from an upper olive over a trapezoid body is located a medial loop (lemniscus med.), representing a yarn of proprioceptive sensitivity, and a spinal loop (lemniscus spinalis) — a yarn of a way painful and a thermoesthesia.
Important funkts, value M. of of m is caused, on the one hand, by an arrangement of kernels of cranial nerves in it (V, VI, VII, VIII couples), a reticular formation, kernels of the bridge, with another — passing through M. of efferent pathways (korkovospinnomozgovy and cortical and nuclear, pokryshechno-spinal, krasnoyaderno-spinal, reticular and spinal, etc.) and the afferent ways (spinotalamichesky, conduction paths proprioceptive — deep — sensitivity, etc.) having the vital value for an organism and which are carrying out a two-way communication between a brain (see) and a spinal cord (see).
Depending on localization of the center of defeat at M.'s pathology of of m various wedge, syndromes develop. Loeb and Maier (S. Loeb. J. S. Meyer, 1968) ventral, tegmental and lateral pontinny syndromes, and also their various combinations allocate (e.g., a bilateral ventral syndrome, ventral and lateral syndromes, ventral and tegmental syndromes, a bilateral tegmental syndrome).
The ventral syndrome of the bridge developing at hemilesion of a middle and upper (rostral) part of foundation of the bridge (fig. 3 — IV, in — VII), is characterized by a contralateral hemiparesis or a hemiplegia, at bilateral defeat — kvadriparezy or a quadriplegia, occasionally lower paraparesis; quite often the pseudobulbar syndrome develops (see. Pseudobulbar paralysis); in nek-ry cases disorder of pelvic functions is observed. Miyyar's syndrome — Gyublera is characteristic of defeat of a caudal part of foundation of the bridge (fig. 3, and — II) (see. Alternating syndromes). The tegmental pontinny syndrome arises at defeat of the tail (tire) of the bridge. The center in a caudal third of a tire (fig. 3, and — I) is followed by development of the lower syndrome of Fovill (Fovill's syndrome — Miyyara — Gyublera), at Krom Goma lateralno takes place defeat VI and VII cranial nerves, paralysis of a look towards the center. At defeat of a caudal part of a tire also Gasperini's syndrome is described, to-ry V, VI and VII cranial nerves and a contralateral hemianaesthesia are characterized by gomolateralny defeat. The syndrome to the Silk-worm eggs (a cross sensitive syndrome) is characteristic of defeat of an average third of a tire (fig. 3 — III): gomolateralny disturbance of sensitivity on a face, sometimes paralysis of masseters, kontralateralno — a gemigipesteziya; the ataxy and an intentsionny tremor in gomolateralny extremities due to damage of an upper cerebellar leg is sometimes noted. The center in a rostral third of a tire (fig. 3, in — VI) quite often causes Raymond's syndrome — Sestan (see. Alternating a syndrome y), called by also upper syndrome of Fovill. Defeat of a tire in this third of the bridge, in particular damage of an upper cerebellar leg (fig. 3, in — V), can lead also to development of a myoclonia of a soft palate («nystagmus» of a soft palate), and sometimes and muscles of a throat and a throat. At sharply arising defeat of a tire of the bridge also heavy disturbance of consciousness can be observed. The lateral pontinny syndrome (Mari's syndrome — Fua) connected with damage of average cerebellar legs (fig. 3, in — VIII), is characterized by existence of gomolateralny cerebellar symptoms; sometimes at more extensive defeat the cross gemigipesteziya and a hemiparesis are observed.
At total defeat of the bridge there is a combination of signs of bilateral ventral and tegmental syndromes which sometimes is followed by a so-called syndrome of the person locked when the patient cannot move extremities and speak, however its consciousness and the movements of eyes are kept. This syndrome is a consequence of true paralysis of extremities and anarthrias as a result of bilateral defeat of motive and cortical and nuclear ways. The syndrome resembles an akinetic mutism superficially (see the Movements, pathology), to-ry is caused by disturbance of motivation to action at absence at sick paralysis.
From patol, processes most often in the area M. of of m there are heart attacks as a result of okklyuziruyushchy, usually atherosclerotic, defeats of vessels of vertebralno-basilar system; the hemorrhages developing owing to arterial hypertension are less frequent. The syndromes which are observed in these cases differ in big polymorphism, however existence of classical alternating syndromes is a little characteristic. The clinic of heart attacks varies depending on the level of defeat of vessels of vertebralno-basilar system and opportunities of collateral circulation. A wedge, displays of hemorrhages to the bridge depend from topics of defeat, rate of their development and existence or lack of break of blood in the fourth ventricle. Occasionally found arteriovenous malformation (aneurisms) in the field of the bridge differ in the progressing increase nevrol, the symptomatology connected with defeat of the bridge, an epileptiform neuralgia; their sudden gap with subarachnoidal and parenchymatous hemorrhage is possible. Also meshotchaty aneurisms can be the cause of hemorrhages.
In the field of the bridge tumors (glioma) and tuberculomas meet (see the Brain). For early stages of gliomas when defeat is unilateral, as well as existence of alternating pontinny syndromes is characteristic of the tuberculomas which are localized usually in a tire; further, at distribution patol, process, defeat of a number of kernels of cranial nerves, and also pyramidal and cerebellar ways (in connection with effective antitubercular therapy of a tuberculoma began to meet seldom) is observed. The wedge, signs of involvement of M. of of m can appear in process of growth of a tumor of a mostomozzhechkovy corner.
M.'s defeat of m is quite often observed at acute poliomyelitis that is clinically usually shown by «nuclear» paralysis of mimic muscles.
The most frequent type of traumatic defeat of the bridge is the hemorrhage in its parenchyma developing along with hemorrhages in other departments of a brain.
Wedge, a picture of the central pontinny miyelinoliz, to-rogo is the cornerstone acute death of myelin covers in the central part M. of of m, is characterized by quickly progressing pyramidal frustration up to a quadriplegia, pseudobulbar paralysis, a tremor, rigidity, disturbance of mentality and intelligence, a lethal outcome within several weeks or months. The etiology of a disease is not clear, however its communication with hron, alcoholism and disturbance of food is noted.
Treatment of defeats of M. of of m is carried out taking into account character patol. process and its stage.
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D. K. Lunev; V. V. Turygin (An.).