家兔脑干三叉神经诱发电位监测方法的研究

目的建立稳定可靠的家兔脑干三叉神经诱发电位的监测方法。方法 20只家兔随机分为两组,每组各10只。两组均使用针形刺激电极,一组穿刺鼻唇沟(穿刺鼻唇沟组),另一组穿刺眶下孔(穿刺眶下孔组),均以Cz-Cv7导联记录家兔三叉神经诱发电位。结果两组刺激阈值和最大刺激强度均无明显差别;穿刺眶下孔组三叉神经诱发电位波形检出率明显高于穿刺鼻唇沟组(χ2=6.6667,P0.01),但刺激产生的肌电伪迹较明显。结论穿刺眶下孔直接刺激眶下神经能够较恒定地监测出三叉神经诱发电位,尽管伪迹较明显,但不影响对波形特征的判断,应用价值较大。     

采用经皮热凝神经术辅助经皮热凝三叉神经节根治疗三叉神经痛

目的总结采用经皮热凝上颚神经以辅助标准的经皮热凝三叉神经节根治疗三叉神经痛的经验.方法第一组：13例有三叉神经第二支与第三支疼痛的典型三叉神经痛病人,接受标准神经节根热凝术,同时辅助以经皮热凝眶下上颚神经.第二组：12例过去接受热凝神经节根治疗的病人,复发疼痛于V2,但V3未复发.采用经皮热凝眶下神经做为权宜的缓解疗法,而不必再施行神经节根热凝术.结果第一组病人经合并两法治疗后,获得满意的疗效,在V2区获得无痛,而V3区仅轻度麻木,且几乎没有咀嚼功能障碍,疗效维持3年,未见复发.第二组病人,仅施行简单的神经热凝术,不需重做神经节根的热凝术,即可获得满意的缓解复发疼痛,疗效可维持1年.结论针对某些病例,热凝三叉神经节根辅助以经皮热凝上颚神经,比起只做三叉神经节根热凝术的结果优越,可避免脸部过度麻木与咀嚼功能的障碍,不会产生痛性麻木.对于仅限于V2复发疼痛的病人,采用权宜简单的经皮热凝眶下神经,可有效解除其复发,而不需重做神经节根的热凝治疗,避免恶化其副作用.     

136例三叉神经痛微血管减压术临床报道

目的探讨三叉神经痛微血管减压术的疗效与责任血管的解剖特点。方法通过对136例三叉神经痛患者行微血管减压手术治疗，术中观察和判定责任血管的来源、压迫三叉神经根部的位置，探讨责任血管的解剖特点及疗效。结果责任血管以小脑上动脉的外侧支的分支压迫三叉神经的上表面最常见，共80侧（58．8％）；小脑前下动脉的分支压迫三叉神经的下表面较少，共20侧（14．7％）；两支血管分别压迫三叉神经的上、下表面的有18侧（13．2％）；单纯静脉压迫三叉神经根部的有12侧（8．8％）；附近无任何血管压迫但术中发现三叉神经覆盖的蛛网膜明显增厚者6侧（4．4％）。136例病人中，术后疼痛消失134例，治愈率为98．5％，无效2例。术后随访112例，平均4．3年．102例疼痛完全消失，4例部分缓解，6例复发或无效。结论邻近血管的压迫是三叉神经痛的主要病因，微血管减压术是治疗三叉神经痛最有效的方法，其疗效取决于熟练的显微解剖知识和显微操作技巧。仔细寻找所有的责任血管并隔离确实，保护好邻近区域的神经和血管，是增加疗效、减少术后并发症的关键。     

氦氖激光照射蝶腭神经节治疗三叉神经痛和蝶腭节神经痛

头面部植物神经系统,对面、眶、腭的营养和血循环的调节起重大作用,所以和三叉神经痛与蝶腭节神经痛的发病机制有密切的关系.蝶腭神经节位于翼腭窝内,直径3～5mm.含有副交感纤维(岩浅大神经)、交感纤维(岩深神经)和感觉纤维(三叉神经第Ⅱ支的分支).岩浅大神经和岩深神经合并形成翼管神经,穿翼管进入蝶腭神经节;节后纤维分布到眼、咽、鼻和腭.蝶腭神经节从面部定位较     

MRI探讨颅神经疾病的发生机制及其对微血管减压手术的指导意义

目的 利用MRI检查探讨颅神经疾病的发生机理以及对微血管减压手术的指导价值.方法 观察手术治疗251例颅神经疾病患者与60例正常对照组核磁共振检查结果,评价异位血管压迫在颅神经疾病发生发展中的作用,观察脑池段三叉神经、面神经长度及蛛网膜下腔宽度,以及面神经和脑干位置关系对手术难易程度的影响.结果 颅神经疾病患者患侧与健侧,患者患侧与健康人群血管神经接触关系有显著差异;三叉神经、面神经长度,蛛网膜下腔宽度以及面神经与与脑干位置关系都对手术的难度产生影响.结论 MRI-3DFFE序列检查能清晰显示生理状态下神经血管关系.神经血管压迫与颅神经疾病发生发展有密切关系.术前MRI检查对指导微血管减压手术及预测手术难度有重要的指导意义.     

三叉神经痛责任血管部位和MVD手术短期疗效

目的探讨三叉神经责任血管的部位和微血管减压手术(MVD)短期疗效之间的关系。方法回顾性分析50例原发性典型三叉神经痛患者MVD手术中责任血管的部位和手术后短期疗效。结果 40例单纯背侧血管压迫患者MVD手术后全部缓解。6例单纯腹侧血管压迫患者MVD手术后,1例缓解。4例需服药1 w左右缓解。1例出院后需继续服药。结论三叉神经痛责任血管部位不同(背侧和腹侧),缓解率存在显著差异。     

内镜经上颌窦入路眶下/上颌神经解剖

目的探讨眶下/上颌神经在内镜经上颌窦入路中的定位引导作用,为临床手术提供解剖学资料。方法对8例成人头颅标本通过模拟内镜下经上颌窦入路对眶下/上颌神经进行解剖,并测量和采集相关数据图片。结果 8例标本16侧上颌神经从三叉神经半月节分出后,均从圆孔出颅,在眶下裂处移行为眶下神经,行走于眶下管内从眶下孔出眼眶。利用圆孔、眶下裂、眶下孔,眶下/下颌神经可分成四段:终末段,眶下神经出眶下孔之后;眼眶-上颌窦段,位于眶下管内,眶下神经进眶下裂至出眶下孔之前,长度为(11.7±2.5)mm,该段在上颌窦内即可清晰辨认;翼腭段,上颌神经出圆孔至入眶下裂之前,长度为(13.4±2.1)mm;颅内段,下颌神经从三叉神经节分出后至出圆孔之前,长度为(15.2±3.9)mm。结论在内镜经上颌窦入路中,利用眶下神经/上颌神经的走形可引导进入颞下窝、翼腭窝、三叉神经节及海绵窦外侧壁。     

脑池段三叉神经周围结构的显微解剖

目的 显微解剖观察三叉神经、小脑上动脉与岩静脉之间的解剖关系,以为微血管减压术提供解剖学参考.方法 模拟经乙状窦后锁孔入路手术对15 例(30 侧)成人尸头标本进行解剖,骨窗范围设计为2.00 cm × 2.50 cm,于4 ~ 24 倍手术显微镜下观察显露范围和解剖结构,打开颅盖骨、剔除硬脑膜和大脑组织,显露小脑幕和脑干,通过显微镜解剖三叉神经、小脑上动脉和岩静脉,观察分析相关解剖学变异.结果 经乙状窦后锁孔入路行微血管减压术可较好地显露三叉神经、滑车神经、岩静脉和小脑上动脉.约36.67%(11/30)标本小脑上动脉与三叉神经接触或压迫,15 例标本内听道上结节形态变异较大,阻挡了对Meckel憩室的显露.其中单干型岩静脉24 侧,双干型岩静脉6 侧;约22.22%(8/36)岩静脉在内听道内侧缘外侧部汇入岩上窦,63.89%(23/36)在内听道内侧缘与Meckel 憩室处三叉神经外侧缘之间汇入岩上窦,13.89%(5/36)于三叉神经外侧缘以内汇入岩上窦.三叉神经与岩静脉相对位置关系分为无接触型、接触型、属支"骑跨"型、蛛网膜粘连型和贯穿神经型.结论 小脑上动脉和岩静脉与三叉神经解剖关系密切,是三叉神经痛的主要责任血管.岩静脉是微血管减压术中必须显露的血管结构,其位置、形态、分支和静脉回流区域存在明显变异,个体化处理岩静脉,有助于手术视野的显露,减少静脉系统并发症.     

磁共振三维成像技术研究岩静脉影像解剖学特征

目的 联合应用MRI的双激发式稳态自由进动(BTFE)序列与增强T1高分辨率各向同性容积激发(e-THRIVE)成像序列分析岩静脉的正常解剖结构及其与同侧三又神经的空间毗邻关系.方法 选取41例面肌痉挛及气叉神经痛患者.采用飞利浦公司ACHIEVA NOVA DUAL A-serial 1.5T磁共振扫描仪对患者进行成像.成像序列为BTFE与e-THRIVE序列,主要观察脑桥小脑角区岩静脉及其与三叉神经的窄间毗邻关系.结果41例共82侧岩静脉及同侧三叉神经均显示清晰;岩静脉位于蛛网膜下腔,呈局部游离状态.岩静脉主干支数为1、2、3支者分别为70侧(86%)、10侧(12%)、2侧(2%).37例共74侧岩静脉(91%,BTFE、e-THRIVE序列)位于三叉神经根的背外方,3例共6侧岩静脉(7%,e-THRIVE序列)位于神经根的腹外方,1例共2侧岩静脉(2%,BTFE 序列)位于神经根的正上方.结论 联合应用BTFE与e-THRIVE序列可以清晰显示岩静脉及三叉神经,并可以准确评估两者间的空间毗邻关系,为三叉神经痛患者行微血管减压术术前提供局部影像学解剖信息.     

枕骨大孔区肠源性囊肿1例报道

肠源性囊肿是指在胚胎发育时由神经肠管的残存组织发育而成的囊肿,可发生在中枢神经系统的各个部位。颅内肠源性囊肿在第四脑室、桥小脑角、眶上裂等处均见报道。脊髓肠源性囊肿可发生在脊髓的腹侧、背侧或脊髓内,大多位于胸段,在颈段、腰段、圆锥部也可见到,位于枕骨大孔区尚未见报道。     

Oral and facial representation within the medullary and upper cervical dorsal horns in the cat

Transganglionic transport of HRP was used to study the patterns of termination of somatic afferent fibers innervating oral and facial structures within the trigeminal nucleus caudalis and upper cervical dorsal horn of the cat. In separate animals, the superior alveolar, pterygopalatine, buccal, inferior alveolar, lingual, frontal, corneal, zygomatic, infraorbital, mental, mylohyoid, and auriculotemporal branches of the trigeminal nerve were traced in this experiment. The organization of the primary afferents innervating the oral structures is not uniform across laminae and at different rostrocaudal levels of the nucleus caudalis. The superior alveolar and pterygopalatine nerves mainly terminate in laminae I, II, and V at the level of the rostral one-third of the caudalis. By contrast, the lingual, inferior alveolar, and buccal nerve terminate in laminae I-V of, respectively, the rostral third, the entire length, and caudal two-thirds of the caudalis. In addition, the lingual, buccal, and pterygopalatine nerves terminate in the dorsal and middle parts of the interstitial islands or pockets of lamina I neuropil extending to the rostral levels parallel to the nucleus interpolaris. Mediolaterally, in laminae I, II, and V of the rostral third an extensive overlap of projections was found between the branches from each trigeminal division, and some overlap was observed between projections from the mandibular and maxillary divisions. On the other hand, the projections of primary afferents innervating the facial structures are arranged in a somatotopic fashion in rostrocaudal and mediolateral axes over the laminae (I-IV) through the nucleus caudalis and upper cervical dorsal horn. Fibers from the perioral and perinasal regions terminate most rostrally in caudalis, and fibers from progressively more posterior facial regions terminate at successively lower levels. A mediolateral somatotopic arrangement was observed, with fibers from the ventral parts of face ending in the medial regions and fibers from the progressively more dorsal parts of the face ending in successively more lateral regions of the medullary and upper cervical dorsal horns. Corneal afferent terminals are concentrated in the outer parts of lamina II at the levels of the rostral parts of the caudal two-thirds of the caudalis and the interstitial islands of lamina I. The maxillary division terminates first at the most caudal level of the caudalis, followed by the ophthalmic division descending as far as the C2 segment and the mandibular division reaching the most caudal level of the C2 segment.(ABSTRACT TRUNCATED AT 400 WORDS)     

The motor complex and primary projections of the trigeminal nerve in the monitor lizard, Varanus exanthematicus

The sensory projections and the motor complex of the trigeminal nerve of the reptile Varanus exanthematicus were studied with the methods of anterograde degeneration and anterograde and retrograde axonal transport. The primary afferent fibers diverge in the brainstem into a short ascending and a long descending tract. The former distributes its fibers to the principal sensory trigeminal nucleus, where nerves V1, V2, and V3 are represented along a lateromedial axis. The fibers of the descending tract enter the nucleus of this tract and the reticular formation. Both in the tract and its nucleus, nerves V1, V2 and V3 occupy successively more dorsal positions. A small contingent of nerve V1 fibers course to the accessory abducens nucleus. The descending tract extends caudally into the first and second cervical segments of the spinal cord. The trigeminal motor complex consists of dorsal, ventral, and dorsomedial nuclei. The m. adductor mandibulae externus (the main jaw closer) is represented in the dorsal nucleus, predominantly in its rostral part. The muscles innervated by nerve V3 are represented in the ventral nucleus, mainly in its caudal part. All three divisions of the trigeminal nerve contain peripheral branches of the mesencephalic trigeminal system. Collaterals of the central branches of this system were traced to the ventral motor and the principal sensory trigeminal nuclei.     

Peripheral and central distribution of major branches of the facial taste nerve in the carp

The major pathways of the peripheral facial taste system in the carp, Cyprinus carpio, are the maxillary (Max), mandibular (Mand), palatine (Pal) and recurrent nerve rami. The peripheral distribution of the sensory fibers of these branches (B) was determined by means of electrophysiological techniques. Max.B., Mand.B. and Pal.B., each of which arises from the gasserian-geniculate ganglionic complexes, were found to innervate respectively, the upper lip and the adjacent skin, the internal and external surface of the lower lip region, and the upper lip and the anterior palate, ipsilaterally. The recurrent nerve sends fibers mainly via dorsal and ventral branches of the posterior lateral line nerve (NPLL), and a pectoral branch of the occipito-spinal nerve. The dorsal and ventral branches of NPLL innervate respectively, the dorsal fin and the adjacent body surface, and the remainder of the body surface. The pectoral branch supplies the pectoral fin. The central connections of the above branches were also examined by using the techniques of transganglionic tracing with horseradish peroxidase (HRP). HRP was applied to each of the branches, and its penetration of the brainstem was carefully followed. Labeled fibers were observed only in the ipsilateral region of the brainstem. When Max.B or Mand.B. was treated with HRP, labeled fibers were observed in the facial sensory root and in the descending trigeminal root. When Pal.B. was treated, however, they were traced only to the facial sensory root; thus indicating that the former two branches are trigeminofacial complexes and the latter is a pure facial nerve. Labeled fibers for NPLL were found in the facial sensory root as well as in bundles projecting to the lateral line areas. The facial fibers of Max.B. and Mand.B. innervate respectively in the dorsal-intermediate portion of the rostral half of the facial lobe, and in the ventral portion of the caudal half of the lobe. Those of Pal.B. however, cover a large area of the lobe anteroposteriorly except for the dorsal and ventral portions. The recurrent fibers of NPLL and the pectoral B. end in the dorsal-medial portion of the caudal half of the lobe. Thus the results of this study show that there is a topographical relation between the receptive field of the 6 peripheral nerve branches and their locus of representation in the facial lobe. Similarly, that the gustatory system through Pal.B. is represented on the facial lobe in a disproportionately large area compared to that of the other 5 branches.     

Electrophysiological evidence for afferent nerve fibers in human ventral roots

This study was designed to test the hypothesis that ventral roots in humans contain afferent nerve fibers. We made direct electrophysiological recordings of compound nerve action potentials in dorsal and ventral roots in children undergoing selective dorsal rhizotomy for spastic cerebral palsy. We stimulated the saphenous or sural nerves, which are pure sensory nerves, with electrical stimuli while systematically recording from ventral and dorsal roots from L3 to S2. In addition to the dorsal root nerve action potentials which we expected, we found smaller compound nerve action potentials, which were clearly afferent, in the ventral roots. This confirms the limited amount of experimental evidence that ventral roots do contain some afferent nerve fibers. The functional significance of these observations is not yet clear.     

The central projections of the trigeminal,facial and anterior lateral line nerves in the carp (Cyprinus carpio L.)

The central projections of the trigeminal, facial and anterior lateral line nerves were studied in the carp (Cyprinus carpio) by the Nauta and Fink-Heimer silver techniques following rhizotomy. Degenerating trigeminal fibers were found projecting on the nucleus of the descending trigeminal root and on the medial funicular nucleus. The former can be subdivided in five portions lying dorsal to the various cranial motor nuclei. The afferent facial fibers could be traced into the facial, glossopharyngeal and vagal lobes, while the anterior lateral line nerve projects on rostral, medial and caudal parts of the medial nucleus and on the eminetia granularis. The anterior lateral line nerve can be divided into a dorsal and a ventral root, each following the same course. The role trigeminal and facial nerves play in proprioception of respiratory muscles is discussed.     

Electrophysiological evidence for an increase in the number of ventral root afferent fibers after neonatal peripheral neurectomy in the rat

Our recent study has shown that many afferent fibers in the ventral root are third branches of dorsal root ganglion cells in addition to their processes in the peripheral nerve and the dorsal root. From results of this study, we hypothesized that most of the afferent fibers in the normal ventral root are extra processes of certain dorsal root ganglion cells. To accommodate experimental findings by others, we formulated several working hypotheses in the present study as an extension of our previous hypothesis: these afferent processes in the ventral root are of varying length; they end bluntly along the length of the root; and in an event such as peripheral neurectomy in the neonatal stage, these fibers sprout at the blunt endings along the length of the ventral root. We tested the above hypotheses using electrophysiological methods. The sciatic nerve on one side in neonatal rats was cut. After the rat was fully grown, volleys of neural activity were recorded along the length of the ventral root while stimulating the dorsal root of the same segment. There was a great increase in the size of compound action potentials in the ventral root on the sciatic nerve-lesioned side. Various lines of evidence suggest that this enhancement of the evoked potentials is likely to be due to an increase in the number of afferent fibers in the ventral root in response to neonatal peripheral nerve injury. The results are consistent with our hypotheses.     

Primary afferent projections from the upper respiratory tract in the muskrat.

The central projections of the ethmoidal, glossopharyngeal, and superior laryngeal nerves were determined in the muskrat by use of the transganglionic transport of a mixture of horseradish peroxidase (HRP) and wheat germ agglutinin (WGA)-HRP. The ethmoidal nerve projected to discrete areas in all subdivisions of the ipsilateral trigeminal sensory complex. Reaction product was focused in ventromedial portions of the principal nucleus, subnucleus oralis, and subnucleus interpolaris. The subnucleus oralis also contained sparse reaction product in its dorsomedial part. Projections were dense to ventrolateral parts of laminae I and II of the rostral medullary dorsal horn, with sparser projections to lamina V. Label in laminae I and V extended into the cervical dorsal horn. A few labeled fibers were followed to the contralateral dorsal horn. The interstitial neuropil of the ventral paratrigeminal nucleus was densely labeled. Extratrigeminal primary afferent projections in ethmoidal nerve cases involved the K?lliker-Fuse nucleus and ventrolateral part of the parabrachial nucleus, the reticular formation surrounding the rostral ambiguous complex, and the dorsal reticular formation of the closed medulla. Retrograde labeling in the brain was observed in only the mesencephalic trigeminal nucleus in these cases. The cervical trunk of the glossopharyngeal and superior laryngeal nerves also projected to the trigeminal sensory complex, but almost exclusively to its caudal parts. These nerves terminated in the dorsal and ventral paratrigeminal nuclei as well as lamina I of the medullary and cervical dorsal horns. Lamina V received sparse projections. The glossopharyngeal and superior laryngeal nerves projected to the ipsilateral solitary complex at all levels extending from the caudal facial nucleus to the cervical spinal cord. At the level of the obex, these nerves projected densely to ipsilateral areas ventral and ventromedial to the solitary tract. Additional ipsilateral projections were observed along the dorsolateral border of the solitary complex. Near the obex and caudally, the commissural area was labeled bilaterally. Labeled fibers from the solitary tract projected into the caudal reticular formation bilaterally, especially when the cervical trunk of the glossopharyngeal nerve received tracer. Labeled fibers descending further in the solitary tract gradually shifted toward the base of the cervical dorsal horn. The labeled fibers left the solitary tract and entered the spinal trigeminal tract at these levels. Retrogradely labeled cells were observed in the ambiguous complex, especially rostrally, and in the rostral dorsal vagal nucleus after application of HRP and WGA-HRP to either the glossopharyngeal or superior laryngeal nerves. In glossopharyngeal nerve cases, retrogradely labeled neurons also were seen in the inferior salivatory nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)     

Central distribution of the efferent cells and the primary afferent fibers of the trigeminal nerve in Pleurodeles waltlii (Amphibia, Urodela)

As part of a study on the organization of the brainstem in a primitive group of vertebrates, the efferent cells and primary afferent fibers of the urodele amphibian Pleurodeles waltlii were examined by means of retrograde and anterograde axonal transport and anterograde degeneration. The trigeminal motor nucleus is located in the periventricular gray just medial to the sulcus limitans. Its rostral part is a band of pear-shaped cells lying parallel to the wall of the ventricle, whereas its caudal part is a round mass consisting of polygonal cells. In addition, a small group of scattered neurons is situated ventral to the rostral part of the nucleus. The primary afferent fibers enter the brainstem in the dorsal two-thirds of the trigeminal root. They diverge into a short ascending and a long descending tract. The former distributes its axons to the principal sensory trigeminal nucleus, which is an ill-defined cell group located at the ventrolateral edge of the periventricular gray. In the descending tract, the fibers of the ophthalmic nerve are predominantly located ventromedially, and those of the maxillomandibular nerve dorsolaterally. A fascicle of the ophthalmic nerve leaves the descending tract and, apparently, makes contact with the accessory abducens nucleus. The descending tract extends caudally into the three upper cervical segments of the spinal cord. The mesencephalic trigeminal nucleus consists of conspicuous large cells, which are scattered through the tectum of the mesencephalon. The cells with peripheral branches in the ophthalmic nerve are mainly located in the caudal half of the tectum, and those with peripheral branches in the maxillomandibular nerve in the rostral half. Collaterals of the central branches of the mesencephalic trigeminal system were traced to an area of the periventricular gray situated between the motor nucleus and the principal sensory nucleus of the trigeminus.     

Central projections of the lateral line nerves in the shovelnose sturgeon

Primary projections of the anterior ( ALLN ) and posterior ( PLLN ) lateral line nerves were traced in the shovelnose sturgeon by means of horseradish peroxidase (HRP) histochemistry and silver degeneration. The trunk of the ALLN divides into dorsal and ventral roots as it enters the medulla. Fibers of the dorsal root form ascending and descending branches that terminate within the ipsilateral dorsal octavolateralis nucleus and the dorsal granular component of the lateral eminentia granularis. Fibers of the ventral root of the ALLN , as well as fibers of the PLLN , enter the medulla ventral to the dorsal root of the ALLN where some of the fibers terminate among the dendrites of the magnocellular octaval nucleus. The bulk of the fibers form ascending and descending branches that terminate within the ipsilateral medial octavolateralis nucleus. A portion of the ascending fibers continue more rostrally and terminate in the ipsilateral eminentia granularis and bilaterally in the cerebellar corpus. Some fibers of the descending rami of both the ALLN and PLLN extend beyond the caudal limit of the medial octavolateralis nucleus to terminate in the caudal octavolateralis nucleus. The HRP cases also revealed retrogradely filled large neurons whose axons course peripherally in the lateral line nerve and are likely efferent to the lateral line organs.     

Anatomy of the gustatory system in the hamster: central projections of the chorda tympani and the lingual nerve

The sensory modalities of taste and touch, for the anterior tongue, are relegated to separate cranial nerves. The lingual branch of the trigeminal nerve mediates touch: the chorda tympani branch of the facial nerve mediates taste. The chorda tympani also contains efferent axons which originate in the superior salivatory nucleus. The central projections of these two nerves have been visualized in the hamster by anterograde labelling with horseradish peroxidase (HRP). Afferent fibers of the chorda tympani distribute to all rostral-caudal levels of the solitary nucleus. They synapse heavily in the dorsal half of the nucleus at its rostral extreme; synaptic endings are sparser and located laterally in caudal regions. These taste afferents travel caudally in the solitary tract and reach different levels by a series of collateral branches which extend medially in the the solitary nucleus, where they exhibit preterminal and terminal swellings. Taste afferent axons range in diameter from 0.2 micrometer to 1.5 micrometers. The thickest axons project exclusively to the rostral and intermediate subdivisions of the solitary nucleus; the find ones may distribute predominantly to the caudal subdivision. Afferent fibers of the lingual nerve terminate heavily in the dorsal one-third of the spinal nucleus of the trigeminal nerve and also as a dense patch in the lateral solitary nucleus at the midpoint between its rostral and caudal poles. This latter projection overlaps that of the chorda tympani. Thus the two sensory nerves which subserve taste and touch from coincident peripheral fields on the tongue converge centrally on the intermediate subdivision of the solitary nucleus. Efferent neurons of the superior salivatory nucleus were labelled retrogradely following application of HRP to the chorda tympani. These cells are located ipsilaterally in the medullary reticular formation ventral to the rostral pole of the solitary nucleus; their dendrites are oriented dorsoventrally. The efferent axons course dorsally, form a genu lateral to the facial somatomotor genu, and course ventrolaterally through the spinal nucleus of the trigeminal nerve to exit the brain ventral to the entering facial afferents.