Acute peripheral facial palsy: Is there a trigeminal nerve involvement?

The aim of this study was to investigate trigeminal nerve involvement in patients with peripheral facial palsy. In total, 25 patients with facial nerve palsy and 19 controls were tested by electrophysiological methods regarding their facial and trigeminal nerve functions within 1 month after disease onset. The presence of an abnormal blink reflex was determined in patients with peripheral facial palsy by comparing paralytic and non-paralytic sides (12.3 ± 1.1 and 10.8 ± 1.3, respectively; p = 0.001). However, the average masseter inhibitory reflex difference between the paretic and non-paralytic sides of patients compared with the corresponding side-to-side comparison for controls was not statistically significant. The masseter inhibitory reflex response was abnormal in some cases. These findings suggest that the masseter inhibitory reflex, a trigemino–trigeminal reflex, was normal in most of our patients with peripheral facial palsy, but may be abnormal in individual cases. Our study showed that subclinical disorders affecting the trigeminal pathways occur in individual patients with idiopathic facial palsy, while the majority of patients have no trigeminal nerve involvement.     

Significant Differences in Sympathetic Nerve Fiber Density Among the Facial Skin Nerves: A Histologic Study Using Human Cadaveric Specimens

Sympathetic nerve fibers in the skin nerves are connected with vasomotor, thermoregulatory, sensory input modulatory, and immunologic events; however, to our knowledge, no histological information is available for skin nerves in the human face. Using specimens from 17 donated cadavers (mean age, 86 years), we measured a sectional area of tyrosine hydroxylase (TH)‐positive fibers in (1) the frontal nerve (V1), (2) the infraorbital nerve (V2), (3) the mental nerve (V3), (4) the greater auricular nerve (C2), (5) the auriculotemporal nerve (ATN), and (6) the zygomatic branch of the facial nerve (VII). The V1, V2, and V3 were obtained at their entrances to the subcutaneous tissue from the bony canal or notch. The V1, C2, ATN, and/or VII usually contained abundant TH‐positive fibers (almost 3%–8% of the nerve sectional area), whereas the V2 and V3 consistently carried few TH‐positive fibers (<1%). The difference between these two groups was quite significant (P < 0.001). Thus, from the superior cervical ganglion, the sympathetic nerve fibers reached the forehead through the frontal nerve trunk, whereas artery‐bounded fibers came to the cheek, nose, and mouth. The sympathetic palsy caused by trigeminal nerve involvement is mainly characterized by the symptoms seen in the distribution of the ophthalmic division of the trigeminal nerve, such as in Horner's syndrome. It suggests that the forehead and the other facial areas are representative parts of those different sympathetic innervations that could be useful for evaluating the sympathetic function of the face in various diseases. Anat Rec, 299:1054–1059, 2016. © 2016 Wiley Periodicals, Inc.     

Experimental skin pain and muscle pain induce distinct changes in human trigeminal motoneuronal excitability

Seeking information on the physiological properties of the trigeminal motoneuronal pool we investigated changes in the excitability of trigeminal motor system induced by two types of experimental pain (muscle and skin). In one session, we studied the effect of muscle pain induced by hypertonic saline infusion into the masseter muscle on the recovery cycle of the heteronymous H-reflex in the temporalis muscle and the homonymous silent period (SP) in the masseter muscle, both elicited by stimulation of the masseteric nerve in ten-healthy subjects. In another session, we studied the effect of laser stimuli applied to the perioral region, at conditioning intervals from 20 to 160 ms, on the temporalis H-reflex and masseter SP in nine healthy subjects. Whereas laser-induced skin pain significantly inhibited the temporalis H-reflex and facilitated the masseter SP (P < 0.01), muscle pain left the time course of the temporalis H-reflex and masseter SP unchanged (P > 0.05). The timing of temporalis H-reflex suppression and masseter-SP enhancement induced by laser stimuli indicates that facial skin nociceptors inhibit trigeminal motoneurones via multysynaptic reflex pathways. Hypertonic saline, a stimulus that predominantly activates group III and IV afferents, left both variables reflecting trigeminal motoneuron excitability unchanged. Due to the differences between the two experimental models, we cannot conclude that such inhibitory reflex pathway does not exist from muscle nociceptors to trigeminal motoneurones.     

正中神经前臂段运动传导与腕管综合征严重程度的相关性研究

目的：探讨正中神经前臂段运动传导（fMCV）与腕管综合征（CTS）疾病严重程度的相关性,并初步探讨其发生机制。方法：以符合纳入标准的CTS患者66例（126只患手）为病例组,年龄、性别匹配的96例健康志愿者的非利手为对照组,均行神经电生理检测。采用正中神经末端运动潜伏期（DML）和复合肌肉动作电位（CMAP）作为CTS严重程度指标,并研究其与fMCV的相关性。结果：①尺神经：病例组与对照组的各电生理参数间比较差异均无显著意义（t检验,P〉0．05）;②正中神经：在病例组（n=126）和对照组（n=96）,DML（ms）分别为5．0±1．3、3．0±0．3,腕-掌段正中神经运动传导速度（m／s）分别为22．2±7．3、56．9±8．3,fMCV（m／s）分别为53．7±5．5、59．2±3．6,拇短展肌CMAP波幅（mV）分别为7．3±2．9、10．1±1．9。以上所有参数的值均经t检验,P〈0．05,差异有显著意义;③相关性：在病例组,fMCV与DML呈负相关（r=-0．35,P〈0．05）,与拇短展肌CMAP呈正相关（r=0．18,P〈0．05）。结论：fMCV的异常与CTS患者的严重程度相关,且正中神经逆行性变为其可能的发生机制。     

Electrophysiological study (EEG, VEPs, BAEPs) in patients with Charcot Marie Tooth (type HMSN I) disease

A laboratory investigation consisting of EEG recordings, BAEPs and VEPs evaluation as well as estimation of the facial nerve distal latency was performed in 9 patients who had Charcot Marie Tooth (type HMSN I) disease. 3 patients showed VEP's abnormalities (2 of them had prolonged P100 latency and one had an abnormal interocular latency difference). Another patient showed an upper normal limit value in the interocular latency difference. Abnormal BAEPs were found in 8 patients (one had I-III/IPLD prolonged, 2 of them had the latency of wave I prolonged and the remaining 6 had no readable or repeatable responses unilaterely or bilaterally). 7 out of 9 patients had the facial nerve distal latency prolonged, without any evident clinical facial weakness. Abnormal EEG recordings were found in 2 of all tested patients. Our results provide some evidence that in Charcot Marie Tooth disease the involvement of the II, VII and VIII nerves is more frequent than clinically expected and is probably related to a demyelinated process.     

Distribution of the galectin-1 mRNA in the rat nervous system: its transient upregulation in rat facial motor neurons after facial nerve axotomy

Galectin-1 is a member of the animal lectin family that displays conserved consensus sequences and similar carbohydrate binding specificities. Recent analyses revealed that galectin-1 plays an important role in the process of nerve regeneration. We analyzed the topological expression of galectin-1 mRNA in adult rat nervous system. Galectin-1 mRNA was predominantly observed in the cell bodies of neurons such as oculomotor nucleus (III), trochlear nucleus (IV), trigeminal motor nucleus (V), abducens nucleus (VI), facial nucleus (VII), hypoglossal nucleus (XII), red nucleus, and locus ceruleus. Neurons in pineal gland and dorsal root ganglia expressed galectin-1 mRNA. We next tested whether the axotomy of facial nerve altered the expression of galectin-1 mRNA in motor neurons. In the adult rats, the axotomy of facial nerve induced transient upregulation of galectin-1 mRNA around 6 h after axotomy. These results indicate that galectin-1 may play roles in the early event of the nerve injury and regeneration through the transient change of its expression level.     

Neuromuscular status of thyroid diseases: a prospective clinical and electrodiagnostic study

With this study, it has been intended to evaluate the neuromuscular symptoms and findings observed in patients with the diagnoses of hyperthyroidism and hypothyroidism. This study included 21 patients with hyperthyroidism, 19 patients with hypothyroidism and a control group comprised of 29 healthy persons. In the patient group with hypothyroidism, the increase in the median motor distal latency and the median sensorial distal latency (p < 0.0001), the reduction in the median sensory action potential amplitude (p < 0.01) and the slowing in the velocity of nerve conduction (p < 0.01) were found significantly different when compared to the control group. H-reflex latencies were determined to be significantly longer bilaterally (p < 0.01). In the patient group with hyperthyroidism, only the reduction in the median sensory action potential amplitude and the prolongation in the distal latency (p < 0.05) were significant. As for the lower extremities, the slowing in the velocity of the nerve conduction of bilateral peroneal (p < 0.0001), the prolongation in the peroneal F-wave latency (p < 0.01), the slowing in the velocity of the nerve conduction of bilateral tibial nerve (p < 0.05), the prolongation in the tibial F-wave latency (p < 0.01), the prolongation in the sural nerve distal latency (p < 0.0001) and the reduction in the sensory action potential amplitude (p < 0.05) were determined to be significantly different compared to the control group. Among the thyroid patients, 17 (42.5%) patients were diagnosed with mononeuropathy and polyneuropathy. Entrapment neuropathy was observed in 30% and diffuse neuropathy in 10% of the patients. Mypopathy findings were observed in 2 patients.     

Peripheral facial nerve communications and their clinical implications

The facial nerve (CN VII) nerve follows a torturous and complex path from its emergence at the pontomedullary junction to its various destinations. It exhibits a highly variable and complicated branching pattern and forms communications with several other cranial nerves. The facial nerve forms most of these neural intercommunications with branches of all three divisions of the trigeminal nerve (CN V), including branches of the auriculotemporal, buccal, mental, lingual, infraorbital, zygomatic, and ophthalmic nerves. Furthermore, CN VII also communicates with branches of the vestibulocochlear nerve (CN VIII), glossopharyngeal nerve (CN IX), and vagus nerve (CN X) as well as with branches of the cervical plexus such as the great auricular, greater, and lesser occipital, and transverse cervical nerves. This review intends to explore the many communications between the facial nerve and other nerves along its course from the brainstem to its peripheral branches on the human face. Such connections may have importance during clinical examination and surgical procedures of the facial nerve. Knowledge of the anatomy of these neural connections may be particularly important in facial reconstructive surgery, neck dissection, and various nerve transfer procedures as well as for understanding the pathophysiology of various cranial, skull base, and neck disorders.     

Asymptomatic electrophysiologic carpal tunnel syndrome in diabetics: entrapment or polyneuropathy

Electrophysiologic carpal tunnel syndrome (CTS) is common and is frequently asymptomatic in diabetics. In order to evaluate the clinical significance of asymptomatic electrophysiologic CTS, the nerve conduction studies (NCS) of 48 diabetics with asymptomatic electrophysiologic CTS were compared with those of 56 age and gender-matched controls, as well as 50 patients with symptomatic CTS without diabetes. Nerve conduction velocities of the ulnar, peroneal, and posterior tibial nerves were significantly slower in diabetics with asymptomatic electrophysiologic CTS than in normal controls. Compared to symptomatic non-diabetic CTS, there was also significant slowing of the median and ulnar nerve conduction velocities in asymptomatic diabetic CTS. However, in diabetics with asymptomatic CTS, abnormalities of the distal segment of the median NCS were more prominent compared with those of all the other tested nerves. These findings suggested that asymptomatic electrophysiologic CTS in diabetics is a manifestation of increased vulnerability to the entrapment of the peripheral nerve.     

Hypoglossal nuclei participation in rat mystacial pad control

Recently, we showed that extra-trigeminal axons, originating from the hypoglossal nucleus, travel with the infraorbital division of the trigeminal nerve (ION), which is known to innervate the rat mystacial pad. Dil was monolaterally injected into the rat XII nucleus to analyse the peripheral distribution of hypoglossal axons to the mystacial pad, to evaluate their involvement in facial sensory-motor control. Electromyographic responses of mystacial pad motor units to electrical stimulation of the ION were recorded, along with the evoked responses to electrical stimulation of the ipsilateral XII nucleus. The results showed that hypoglossal axon terminals target the ipsilateral extrinsic musculature of the mystacial pad, but they do not have any contact with the intrinsic muscles. ION electrical stimulation increased electromyographic activity in the ipsilateral pad extrinsic muscles, even following VII nerve transection. Hypoglossal nucleus electrical stimulation induced field potentials and monosynaptic responses in the same motor units that persisted even following VII nerve transection, these disappearing after cooling the ION. We suggest that the small hypoglossal neurons projecting to the extrinsic musculature of the mystacial pad are part of a hypoglossal-trigeminal loop that participates in the sensory-motor control of the rat vibrissae system.     

Masseteric nerve: A possible donor for facial nerve anastomosis?

In the medical treatment of facial nerve paralysis a large number of different techniques have been developed to restore the function of the facial nerve. These include (a) the ipsilateral nerve grafting (e.g., partial hypoglossal-facial, spinal accessory-facial, partial glossopharyngeal-facial), (b) crossfacial nerve grafting and (c) temporal muscle flaps or even free muscle transfers. None of these techniques uses the masseteric nerve as a graft for reconstruction of the facial nerve. This preliminary report deals with the anatomical basis, which could lead to a new technique. The masseteric nerve leaves the infratemporal fossa through the mandibular notch, accompanied by the masseteric artery. At this level the nerve consists in nine of 36 cases studied of only one branch (25.0%), in 17 cases of two branches (47.0%), in nine cases of three (25.0%), and in the remaining case of four branches (2.8%). There are three main reasons for considering the masseteric nerve as a possible donor for at least the orbicular branch of the facial nerve: (1) The approach to the mandibular notch is quite simple; (2) since the nerve consists of two or more branches in 75.0% of the cases, severe dysfunction of the masseter muscle should not occur; (3) if there is complete denervation of the masseter muscle, its function may be taken over by the temporalis muscle. Clin. Anat. 11:396–400, 1998. © 1998 Wiley-Liss, Inc.     

Presurgical electrophysiological findings in acoustic nerve tumours.

The clinical involvement of the facial nerve is a rare finding among the initial symptoms of acoustic neurinomas. However, compression of the facial nerve is a common intraoperative finding. Blink reflex was recorded in 20 patients affected by cerebellar-pontine angle tumor confirmed at surgery. Recordings were also made of the M-response of the facial nerve from the naso-labial folds. In 6 cases jaw reflex was also recorded. In summary, these electrophysiological studies revealed a facial nerve damage in 13 and a trigeminal nerve dysfunction in 2 out of 18 clinically unaffected patients. The combined study of the 3 tests proved to be useful when the blink reflex showed an isolated R1 delay, that is, in cases in which the level of damage along the trigemino-facial reflex arc cannot be defined by the recording of the blink reflex alone.     

Mesencephalic trigeminal nucleus neurons with collaterals to both the masseter and the inferior alveolar nerves. A fluorescent double-labeling study in the rat.

After fluorescent tracers were applied to the inferior alveolar nerve and the masseter nerve on the same side of the rat, double-labeled neurons were observed in the caudal part of the mesencephalic trigeminal nucleus (Vme), reflecting simultaneous innervation of both the periodontal ligaments and masseter muscle spindles by collaterals of peripheral processes of single Vme neurons.     

The value of neurophysiological and MRI assessment in demyelinating optic neuritis (DON).

PURPOSE: To study, by neurophysiological means, the possible involvement of the retina, in demyelinating optic neuritis (DON). MATERIAL AND METHODS: Thirty-five patients fulfilling strict criteria of unilateral DON were investigated with a battery of neurophysiological tests and MRI within 3 weeks of the onset of their symptoms. Flash-ERG (F-ERG) in photopic conditions, Flash-VEPs and PR-VEPs were recorded. MRI of the brain and the optic nerve were performed. RESULTS: The amplitude of b-wave of F-ERG in photopic conditions was statistically significantly lower in the affected eye (p < 0.001) compared to normal controls, whereas in the unaffected eye, it was also statistically significantly lower than normal controls (p < 0.01). All patients had statistically significant prolongation of P100 latency in PR-VEPs of the affected eye (p < 0.001) in comparison to normal controls. The P100 wave of the unaffected eye was also delayed (p < 0.01). In MRI, Gd-DTPA enhancement was observed in 7 symptomatic nerves with only minimal enhancement of the optic nerve between optic chiasm and optic canal, whereas 11 patients were presented with intracranial associated plaques. Five of the above patients had optic nerve enhancement and diffused demyelinating findings simultaneously. CONCLUSION: These results are a neurophysiological indication of involvement of the retina in DON, probably of vascular origin.     

正中和尺掌-腕混合神经潜伏期差在腕管综合征诊断中的应用

目的:评估正中和尺掌-腕混合神经潜伏期差在腕管综合征(CTS)诊断中的应用价值。方法:选取2019年1月至2019年12月在常熟市中医院门诊诊断为CTS的患者47例(77只手掌)作为研究组,同时收集同时段在体检中心健康检查的志愿者46名(69只手掌)作为对照组,分别记录正中神经腕-拇短展肌的远端运动潜伏期(DML)、腕-中指的感觉神经传导速度(SCV)、感觉神经动作电位(SNAP)波幅及正中和尺掌-腕混合神经潜伏期差(ΔDSL)。结果:研究组与对照组比较,腕-拇短展肌DML延长[(4.49±0.97)ms比(3.16±0.42)ms],腕-中指SCV减慢[(42.62±7.35)m/s比(60.65±6.70)m/s],SNAP波幅下降[(11.89±8.05)μV比(22.07±7.22)μV],正中和尺掌-腕混合神经ΔDSL延长[(0.84±0.34)ms比(0.23±0.10)ms],差异均具有统计学意义(P<0.05)。腕-拇短展肌DML、腕-中指SCV、正中和尺掌-腕混合神经ΔDSL诊断特异度分别为97.1%、100%、98.6%(P>0.05),诊断敏感度分别为66.2%、59.2%、90.1%(P<0.05)。结论:正中和尺掌-腕混合神经ΔDSL用于诊断CTS是比较敏感的,尤其可以提高早期CTS的阳性检出率。     

颞骨原发性恶性肿瘤颅神经侵犯的CT与MR影像学评估

目的 探讨颞骨原发恶性肿瘤颅神经侵犯的CT与MR影像学表现。方法 回顾性分析2010年1月-2018年12月中山大学附属第一医院颞骨原发性恶性肿瘤中合并颅神经侵犯的23例患者的CT、MR影像学资料。其中男15例、女8例,年龄3~80岁;出现颅神经功能障碍17例,包括面神经受累症状者15例,外展神经功能障碍者2例。观察颞骨恶性肿瘤神经侵犯的部位、神经根穿行孔道及神经根的形态、信号及强化等颅神经受侵的CT、MR表现,及其与临床症状、手术病理结果的关系。结果 CT、MRI显示颅神经受侵23例,其中面神经受侵22例,三叉神经受侵5例,展神经、舌咽神经、迷走神经受侵各2例,听神经、副神经、舌下神经受侵各1例。颅神经受侵征象:CT显示面神经管扩大破坏22例,圆孔、卵圆孔骨壁、岩尖三叉神经压迹破坏各2例,颈静脉孔、舌下神经管破坏各1例;MRI显示颅神经增粗、强化8例,神经根干与周围软组织强化影紧贴但未完全包绕3例,神经被肿瘤包绕14例。23例CT、MRI显示的神经受侵患者中出现相应神经症状者17例,占73.9%。同时行CT及MRI检查的16例患者中,CT和MRI影像显示的受累神经分别为19、23根,CT、MRI诊断与临床手术病理一致分别为18、22根,其诊断符合率分别为81.8%(18/22)、95.7%(22/23)。结论 颞骨恶性肿瘤容易出现颅神经侵犯,且以面神经受侵最常见。颅神经受侵CT表现为神经穿行孔道破坏,MRI可直接显示神经增粗、异常强化,神经紧贴软组织影或神经直接被肿瘤包绕。结合CT和MRI的影像评估可以全面精准显示颅神经浸润情况,且MR较CT更为灵敏。     

MR imaging and electrophysiological evaluation in carpal tunnel syndrome

The objective of this study was to compare the MRI findings of wrists in patients diagnosed with CTS with those of the healthy controls, and to evaluate the correlation between the MRI differences and the electrophysiological findings in the patient group. This study involved 55 wrists, 30 of which were clinically and electrophysiologically diagnosed with CTS and 25 healthy controls. These 55 wrists were evaluated electrophysiologically, and in terms of median nerve diameter, ratio of median nerve diameter at psiform bone level to distal radio-ulnar joint level, the flexor retinaculum bulging ratio and the median nerve intensity by MRI. When the patient group, which were clinically and electrophysiologically diagnosed with CTS, and the healthy control group were compared, a significant difference (p < 0.001) was observed between the two in terms of median nerve diameters (at psiform bone level: 8.47 +/- 1.41mm and 2.91 +/- 1.01 mm, distal radio-ulnar joint level: 4.04 +/- 1.06 mm and 2.42 +/- 0.95 mm), ratio of median nerve diameter at psiform bone level to distal radio-ulnar joint level (2.17 +/- 0.54 and 1.25 +/- 0.12), their flexor retinaculum bulging ratios (26.21 +/- 5.98% and 7.27 +/- 4.53%) and their median nerve intensities. In the patient group, no significant correlation between MRI and the electrophysiological findings was found (p > 0.05). According to the data obtained from the study, we believe that the MRI examination of structural changes that occur in the carpal tunnel, neighboring structures and the median nerve would be useful in the diagnosis of CTS, especially in cases with suspected clinical and electrophysiological diagnosis.     

Proprioceptive afferents survive in the masseter muscle of trkC knockout mice

Peripheral innervation patterns of proprioceptive afferents from dorsal root ganglia and the mesencephalic trigeminal nucleus were assessed in trkC-deficient mice using immunohistochemistry for protein gene product 9.5 and parvalbumin. In trkC knockout mice, spinal proprioceptive afferents were completely absent in the limb skeletal muscles, M. biceps femoris and M. gastrocnemius, as previously reported. In these same animals, however, proprioceptive afferents from mesencephalic trigeminal nucleus innervated masseter muscles and formed primary endings of muscle spindles. Three wild-type mice averaged 35.7 spindle profiles (range: 31–41), six heterozygotes averaged 32.3 spindles (range: 27–41), and four homozygotes averaged 32.8 spindles (range: 26–42). Parvalbumin and Nissl staining of the brain stem showed approximately 50% surviving mesencephalic trigeminal sensory neurons in trkC-deficient mice. TrkC −/− mice (n=5) had 309.4±15.9 mesencephalic trigeminal sensory cells versus 616.5±26.3 the sensory cells in trkC +/+ mice (n=4).These data indicate that while mesencephalic trigeminal sensory neurons are significantly reduced in number by trkC deletion, they are not completely absent. Furthermore, unlike their spinal counterparts, trigeminal proprioceptive afferents survive and give rise to stretch receptor complexes in masseter muscles of trkC knockout mice. This indicates that spinal and mesencephalic trigeminal proprioceptive afferents have different neurotrophin-supporting system during survival and differentiation. It is likely that one or more other neurotrophin receptors expressed in mesencephalic trigeminal proprioceptive neurons of trkC knockout mice compensate for the lack of normal neurotrophin-3 signaling through trkC.     

Direct projections from vestibular nuclei to facial nucleus in cats

Postsynaptic potentials were recorded from motoneurons in the facial nucleus in response to stimulation of the vestibular and trigeminal nerves. The motoneurons were identified by antidromic activation from their peripheral axons. Disynaptic excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) and mixed EPSP/IPSPs were recorded in response to vestibular nerve stimulation, ranging in latency from 0.9 to 2.1 ms, with most at 1.5 ms. Activity in secondary vestibular axons recorded within the facial nucleus occurred at a latency of 0.7-1.1 ms. The amplitudes of the vestibular postsynaptic potentials were small, generally less than a millivolt, but double shocks produced marked summation. The average time to peak of ipsilateral vestibular EPSPs, 1.1 ms, was faster than that of either ipsilateral IPSPs, 1.6 ms, or contralateral EPSPs, 1.4 ms. The double-spiked vestibular activity was detectable in double-peaked PSPs. Disynaptic EPSPs, ranging in latency from 2.0 to 3.0 ms, were recorded in response to trigeminal nerve stimulation. The average time to peak was 1.3 ms. The multiple-spiked activity of the trigeminal neurons was detectable in multipeaked EPSPs. Inhibitory ipsilateral effects (Vi IPSPs) were recorded twice as often as excitatory ipsilateral effects (Vi EPSPs), being found in 29% versus 15% of the motoneurons. Contralateral effects were found in 13% of the motoneurons studied, and almost all were excitatory. Analysis of synaptic potential shapes suggested that the excitatory and inhibitory vestibular synapses probably contact distal dendrites preferentially, with the excitatory connections being somewhat closer to the soma. The trigeminal inputs probably contact the facial motoneurons more extensively near the soma. Horseradish peroxidase was injected into the facial nucleus, and retrograde uptake by vestibular neurons was studied. The majority of filled vestibular neurons was ipsilateral to the injection site, especially in the medial vestibular nucleus, ventral y group, and supravestibular nucleus. On the contralateral side, filled vestibular cells were found almost exclusively in the medial nucleus. Filled cells were also noted in the trigeminal nucleus, predominantly ipsilaterally at all rostrocaudal levels. We have demonstrated monosynaptic projections to facial motoneurons from both vestibular and trigeminal nuclei. The trigeminal input is likely to be involved in facial reflexes, especially blinking and grimacing. The afferent vestibular population overlaps that going to the oculomotor and cervical motoneurons; these projections may be collaterals of single vestibular neurons.4+.     

Vanilloid receptor 1-like receptor-immunoreactive primary sensory neurons in the rat trigeminal nervous system

Immunohistochemistry for vanilloid receptor 1-like receptor (VRL-1), a candidate transducer for high-threshold noxious heat, was performed on rat trigeminal primary sensory neurons. The immunoreactivity was detected in 14% of the trigeminal ganglion cell bodies, while the neurons in the mesencephalic trigeminal tract nucleus were almost devoid of it (0.5%). The immunoreactive neurons in the trigeminal ganglion were mostly of medium to large size (mean+/-S.D. of 956+/-376microm(2)). Nerve bundles in the tooth pulp, periodontal ligament, facial skin and oral mucosa contained VRL-1-positive smooth nerve fibers. The immunoreactivity could not be traced to the isolated nerve fibers, except in the tooth pulp. In the brainstem trigeminal nuclear complex, a notable concentration of the immunoreactivity was seen in laminae I and II of the medullary dorsal horn. Thirty-seven per cent of the trigeminal ganglion neurons retrogradely labeled from the tooth pulp exhibited VRL-1 immunoreactivity, while the immunoreactivity was detected in only 9% of those labeled from the skin. Co-expression of calcitonin gene-related peptide was common among the VRL-1-immunoreactive tooth pulp neurons (45%) and cutaneous neurons (25%). Moreover, as many as 41% of the VRL-1-immunoreactive tooth pulp neurons co-expressed parvalbumin immunoreactivity. Parvalbumin immunoreactivity was never detected in the VRL-1-immunoreactive cutaneous neurons.From the findings of the present study, we propose that large primary neurons responding to high-threshold noxious heat are abundant in the tooth pulp, but not in the facial skin.