Neurolocalization of taste disorders

Neurolocalization of taste disorders requires a knowledge of the functional anatomy involved in mediating taste information from the peripheral mucosal surfaces through numerous peripheral cranial nerves to complex subcortical and cortical brain regions. Our understanding of this functional anatomy has advanced in recent years. Taste is an experience that is both innate and learned, and the "taste" experience involves the integration of information from other sensory modalities, such as olfaction and somatosensation. Normal taste perception is influenced by different neurophysiologic states, which involve endocrine function, emotions, and even attitudes and expectations toward eating. At its core, the normal effective ability to taste is a reflection of the proper function of many organ systems within the body and may be considered a marker for good health. Clinical taste disorders, on the other hand, involve the dysfunction of the normal neural taste pathways and/or aberrant influences on multisensory integration and cortical taste processing. The number of disease processes, which can adversely affect taste, are numerous and quite varied in their presentation. There may be contributory involvement of other organ systems within the body, and the appropriate management of taste disorders often requires a multidisciplinary approach to fully understand the disorder. Depending on the underlying cause, taste disorders can be effectively managed when identified. Treatments may include correcting underlying metabolic disturbances, eliminating infections, changing offending medications, replenishing nutritional deficiencies, operating on structural impairments, calming autoimmune processes, and even stabilizing electrochemical interactions.

The greater occipital nerve and its spinal and brainstem afferent projections: A stereological and tract-tracing study in the rat

The neuromodulation of the greater occipital nerve (GON) has proved effective to treat chronic refractory neurovascular headaches, in particular migraine and cluster headache. Moreover, animal studies have shown convergence of cervical and trigeminal afferents on the same territories of the upper cervical and lower medullary dorsal horn (DH), the so-called trigeminocervical complex (TCC), and recent studies in rat models of migraine and craniofacial neuropathy have shown that GON block or stimulation alter nociceptive processing in TCC. The present study examines in detail the anatomy of GON and its central projections in the rat applying different tracers to the nerve and quantifying its ultrastructure, the ganglion neurons subserving GON, and their innervation territories in the spinal cord and brainstem. With considerable intersubject variability in size, GON contains on average 900 myelinated and 3,300 unmyelinated axons, more than 90% of which emerge from C₂ ganglion neurons. Unmyelinated afferents from GON innervates exclusively laminae I-II of the lateral DH, mostly extending along segments C_2-3 . Myelinated fibers distribute mainly in laminae I and III-V of the lateral DH between C₁ and C₆ and, with different terminal patterns, in medial parts of the DH at upper cervical segments, and ventrolateral rostral cuneate, paratrigeminal, and marginal part of the spinal caudal and interpolar nuclei. Sparse projections also appear in other locations nearby. These findings will help to better understand the bases of sensory convergence on spinomedullary systems, a critical pathophysiological factor for pain referral and spread in severe painful craniofacial disorders.

Temperature differentially facilitates spontaneous but not evoked glutamate release from cranial visceral primary afferents

Temperature is fundamentally important to all biological functions including synaptic glutamate release. Vagal afferents from the solitary tract (ST) synapse on second order neurons in the nucleus of the solitary tract, and glutamate release at this first central synapse controls autonomic reflex function. Expression of the temperature-sensitive Transient Receptor Potential Vanilloid Type 1 receptor separates ST afferents into C-fibers (TRPV1+) and A-fibers (TRPV1-). Action potential-evoked glutamate release is similar between C- and A-fiber afferents, but TRPV1 expression facilitates a second form of synaptic glutamate release in C-fibers by promoting substantially more spontaneous glutamate release. The influence of temperature on different forms of glutamate release is not well understood. Here we tested how temperature impacts the generation of evoked and spontaneous release of glutamate and its relation to TRPV1 expression. In horizontal brainstem slices of rats, activation of ST primary afferents generated synchronous evoked glutamate release (ST-eEPSCs) at constant latency whose amplitude reflects the probability of evoked glutamate release. The frequency of spontaneous EPSCs in these same neurons measured the probability of spontaneous glutamate release. We measured both forms of glutamate from each neuron during ramp changes in bath temperature of 4-5 °C. Spontaneous glutamate release from TRPV1+ closely tracked with these thermal changes indicating changes in the probability of spontaneous glutamate release. In the same neurons, temperature changed axon conduction registered as latency shifts but ST-eEPSC amplitudes were constant and independent of TRPV1 expression. These data indicate that TRPV1-operated glutamate release is independent of action potential-evoked glutamate release in the same neurons. Together, these support the hypothesis that evoked and spontaneous glutamate release originate from two pools of vesicles that are independently modulated and are distinct processes.

The sensory innervation of the calvarial periosteum is nociceptive and contributes to headache-like behavior

Headaches are thought to result from the activation and sensitization of nociceptors that innervate deep cephalic tissues. A large body of evidence supports the view that some types of headaches originate intracranially, from activation of sensory neurons that innervate the cranial meninges. However, the notion of an extracranial origin of headaches continues to be entertained, although the identity of deep extracranial cephalic tissues that might contribute to headaches remains elusive. Here we employed anatomical, electrophysiological, and behavioral approaches in rats to test the hypothesis that the sensory innervation of the calvarial periosteum is nociceptive. Neural tracing indicated that the calvarial periosteum overlying the frontal and parietal bones is innervated primarily by small and medium-sized neurons in the trigeminal ganglion's ophthalmic division. In vivo single-unit recording in the trigeminal ganglion revealed that calvarial periosteal afferents have slowly conducting axons, are mechanosensitive, and respond to inflammatory mediators, consistent with a nociceptive function. Two distinct neuronal populations were distinguished based on their peripheral axonal trajectory: one that reached the periosteum through extracranial branches of the trigeminal nerve, and another that took an intracranial trajectory, innervating the cranial dura and apparently reaching the periosteum via the calvarial sutures. In behavioral studies, inflammatory stimulation of these afferents promoted periorbital tactile hypersensitivity, a sensory change linked to primary headaches. Activation and sensitization of calvarial periosteal afferents could play a role in mediating primary headaches of extracranial and perhaps also intracranial origin, as well as secondary headaches such as postcraniotomy and posttraumatic headaches. Targeting calvarial periosteal afferents may be effective in ameliorating these headaches.

Variation, variability, and the origin of the avian endocranium: insights from the anatomy of Alioramus altai (Theropoda: Tyrannosauroidea)

The internal braincase anatomy of the holotype of Alioramus altai, a relatively small-bodied tyrannosauroid from the Late Cretaceous of Mongolia, was studied using high-resolution computed tomography. A number of derived characters strengthen the diagnosis of this taxon as both a tyrannosauroid and a unique, new species (e.g., endocranial position of the gasserian ganglion, internal ramification of the facial nerve). Also present are features intermediate between the basal theropod and avialan conditions that optimize as the ancestral condition for Coelurosauria—a diverse group of derived theropods that includes modern birds. The expression of several primitive theropod features as derived character states within Tyrannosauroidea establishes previously unrecognized evolutionary complexity and morphological plasticity at the base of Coelurosauria. It also demonstrates the critical role heterochrony may have played in driving patterns of endocranial variability within the group and potentially reveals stages in the evolution of neuroanatomical development that could not be inferred based solely on developmental observations of the major archosaurian crown clades. We discuss the integration of paleontology with variability studies, especially as applied to the nature of morphological transformations along the phylogenetically long branches that tend to separate the crown clades of major vertebrate groups.

Loss of ATF2 function leads to cranial motoneuron degeneration during embryonic mouse development

The AP-1 family transcription factor ATF2 is essential for development and tissue maintenance in mammals. In particular, ATF2 is highly expressed and activated in the brain and previous studies using mouse knockouts have confirmed its requirement in the cerebellum as well as in vestibular sense organs. Here we present the analysis of the requirement for ATF2 in CNS development in mouse embryos, specifically in the brainstem. We discovered that neuron-specific inactivation of ATF2 leads to significant loss of motoneurons of the hypoglossal, abducens and facial nuclei. While the generation of ATF2 mutant motoneurons appears normal during early development, they undergo caspase-dependent and independent cell death during later embryonic and foetal stages. The loss of these motoneurons correlates with increased levels of stress activated MAP kinases, JNK and p38, as well as aberrant accumulation of phosphorylated neurofilament proteins, NF-H and NF-M, known substrates for these kinases. This, together with other neuropathological phenotypes, including aberrant vacuolisation and lipid accumulation, indicates that deficiency in ATF2 leads to neurodegeneration of subsets of somatic and visceral motoneurons of the brainstem. It also confirms that ATF2 has a critical role in limiting the activities of stress kinases JNK and p38 which are potent inducers of cell death in the CNS.

[Rare observation of hyperostotic cranial lesions in osteogenesis imperfecta]

A rare case of hyperostotic skull deformity in a patient with congenital bone defect--osteogenesis imperfecta--is described. In this case typical symptoms encountered in adults were observed: decreased body length caused by shortened extremities due to multiple pathological fractures in childhood, deformities of thorax, spine, facial bones and teeth, skull lesions with craniobasal and brainstem symptoms, bluish hue of sclera, hypoacusis etc.). In this patient non-typical abnormalities were found: visual deficit due to optic nerve atrophy caused by bilateral optic canal stenosis on the background of densitometrically proven hyperostotic skull base deformity.

Sensory innervation of the calvarial bones of the mouse

Migraine sufferers frequently testify that their headache feels as if the calvarial bones are deformed, crushed, or broken (Jakubowski et al. [2006] Pain 125:286-295). This has lead us to postulate that the calvarial bones are supplied by sensory fibers. We studied sensory innervation of the calvaria in coronal and horizontal sections of whole-head preparations of postnatal and adult mice, via immunostaining of peripherin (a marker of thinly myelinated and unmyelinated fibers) or calcitonin gene-related peptide (CGRP; a marker more typical of unmyelinated nerve fibers). In pups, we observed nerve bundles coursing between the galea aponeurotica and the periosteum, between the periosteum and the bone, and between the bone and the meninges; as well as fibers that run inside the diploë in different orientations. Some dural fibers issued collateral branches to the pia at the frontal part of the brain. In the adult calvaria, the highest concentration of peripherin- and CGRP-labeled fibers was found in sutures, where they appeared to emerge from the dura. Labeled fibers were also observed in emissary canals, bone marrow, and periosteum. In contrast to the case in pups, no labeled fibers were found in the diploë of the adult calvaria. Meningeal nerves that infiltrate the periosteum through the calvarial sutures may be positioned to mediate migraine headache triggered by pathophysiology of extracranial tissues, such as muscle tenderness and mild trauma to the skull. In view of the concentration of sensory fibers in the sutures, it may be useful to avoid drilling the sutures in patients undergoing craniotomies for a variety of neurosurgical procedures.

Krox-20 gene expression: influencing hindbrain-craniofacial developmental interactions

Krox-20 is a C(2)H(2)-type zinc-finger transcription factor that plays an essential role in hindbrain development. The Krox-20 null mutation results in hindbrain anomalies that result in neonatal death due to respiratory and feeding deficits. Here we review our studies of how the Krox- 20 null mutation impacts the development of motor and sensory systems critical for the production of consummatory behaviors (suckling/chewing). First, we demonstrated that Krox-20 null mutants suffer a selective loss of primary jaw-opening muscles during prenatal development. In vivo and in vitro studies are reviewed that highlight intrinsic defects in mutant jaw-opener muscles that contribute to muscle degeneration. Next we focus on the impact of the mutation on proprioceptive neurons activated during consummatory behaviors. Mesencephalic trigeminal (Me5) neurons are primary sensory neurons that relay jaw proprioception to the central nervous system. These cells are unique because their cell bodies are located in the central as opposed to the peripheral nervous system. Data are reviewed that demonstrate the impact of the mutation on Me5 neurons, a cell group traditionally thought to emerge from the mesencephalon. We show that Krox-20 null mutants have twice as many Me5 neurons relative to wildtypes at E15, but by birth have half the number of Me5 cells as wildtypes. TUNEL assays performed in each set of studies reveal that Krox-20 expression acts to protect both muscle and mesencephalic trigeminal neurons against apoptosis, suggesting that Krox-20, in addition to its role in hindbrain patterning, has a broader, long-lasting role in development.

Effectiveness of osteopathy in the cranial field and myofascial release versus acupuncture as complementary treatment for children with spastic cerebral palsy: a pilot study

CONTEXT

Case reports and clinical trials have indicated that osteopathic manipulative treatment (OMT) may improve motor function and quality of life for children with cerebral palsy.

OBJECTIVE

To assess the effectiveness of osteopathy in the cranial field, myofascial release, or both versus acupuncture in children with moderate to severe spastic cerebral palsy, as measured by several outcomes instruments in a randomized controlled trial.

METHODS

Children between the ages of 20 months and 12 years with moderate to severe spastic cerebral palsy were enrolled in a single-blind, randomized wait-list control pilot study. There were three arms in the study: OMT (ie, osteopathy in the cranial field, myofascial release, or both, using direct or indirect methods), acupuncture, and control (ie, nontherapeutic attention). Children who were initially randomly assigned to the control arm were subsequently randomly reassigned to the intervention arms, increasing the sample size. Outcome measures included standard instruments used in the evaluation of children with cerebral palsy. Less traditional measures were also used, including serial evaluations by an independent blind osteopathic physician and visual analog scale assessments by an independent osteopathic physician and the parents or guardians. A total of 11 outcome variables were analyzed.

RESULTS

Fifty-five patients were included in the study. Individual analyses of the 11 outcome variables revealed statistically significant improvement in two mobility measures for patients who received OMT--the total score of Gross Motor Function Measurement and the mobility domain of Functional Independence Measure for Children (P<.05). No statistically significant improvements were seen among patients in the acupuncture treatment arm.

CONCLUSIONS

A series of treatments using osteopathy in the cranial field, myofascial release, or both improved motor function in children with moderate to severe spastic cerebral palsy. These results can be used to guide future research into the effectiveness of OMT or acupuncture in treating children with spastic cerebral palsy.

The BMP antagonist Noggin promotes cranial and spinal neurulation by distinct mechanisms

Here we characterize the consequences of elevated bone morphogenetic protein (BMP) signaling on neural tube morphogenesis by analyzing mice lacking the BMP antagonist, Noggin. Noggin is expressed dorsally in the closing neural folds and ventrally in the notochord and somites. All Noggin-/- pups are born with lumbar spina bifida; depending on genetic background, they may also have exencephaly. The exencephaly is due to a primary failure of neurulation, resulting from a lack of mid/hindbrain dorsolateral hinge point (DLHP) formation. Thus, as previously shown for Shh signaling at spinal levels, BMP activity may inhibit cranial DLHP morphogenesis. However, the increased BMP signaling observed in the Noggin-/- dorsal neural tube is not sufficient to cause exencephaly; it appears to also depend on the action of a genetic modifier, which may act to increase dorsal Shh signaling. The spinal neural tube defect results from a different mechanism: increased BMP signaling in the mesoderm between the limb buds leads to abnormal somite differentiation and axial skeletal malformation. The resulting lack of mechanical support for the neural tube causes spina bifida. We show that this defect is due to elevated BMP4 signaling. Thus, Noggin is required for mammalian neurulation in two contexts, dependent on position along the rostrocaudal axis.

Bony anomaly of Meckel's cave

This study describes the seemingly rare occurrence of bone formation within the proximal superior aspect of Meckel's cave thus forming a bony foramen for the proximal trigeminal nerve to traverse. The anatomy of Meckel's cave is reviewed and the clinical potential for nerve compression from this bony anomaly discussed.

Acute and chronic pain following craniotomy: a review

Postoperative pain is an important clinical problem that has received increasing attention in recent years. However, pain following craniotomy has been a comparatively neglected topic; this review seeks to redress this imbalance. A brief overview of the anatomy of the skull and its linings is given, with particular reference to innervation. The various approaches for craniotomies are classified, with their association with acute and long-term effects on analgesic requirements. A comprehensive search of the literature was undertaken to ascertain the incidence of acute pain post craniotomy and current thoughts on pharmacological management, touching briefly on pre-emptive treatment. Also discussed is the much neglected but nevertheless real incidence of chronic pain following craniotomy and its underlying pathogenesis, prevention and treatment.

Craniofacial inputs to upper cervical dorsal horn: implications for somatosensory information processing

The aim of this study was to characterize the properties of somatosensory neurons in the first 2 cervical spinal dorsal horns (C1 and C2 DHs) and compare them with those previously described for the rostral subnucleus caudalis (rVc). A total of 74 nociceptive neurons classified as wide-dynamic-range (WDR) or nociceptive-specific (NS), as well as 72 low-threshold mechanoreceptive (LTM) neurons, was studied in urethane/chloralose-anesthetized rats. The majority of LTM neurons were located in laminae III/IV and had a small mechanoreceptive field (RF) that included the posterior face and cervical tissues. In contrast, the nociceptive neurons were located in laminae I/II or V/VI, and the RF of each C1 and C2 DH nociceptive neuron included a part of the face and in 47% of them the RF included a region supplied by upper cervical afferents. There was a gradual caudal shift in the neuronal RF from nasal/intraoral tissues towards the neck as recording sites progressed from rVc to C1 and C2 DHs. In contrast to LTM neurons, many C1 and C2 DH nociceptive neurons received mechanosensitive convergent afferent inputs from cervical and craniofacial deep tissues (e.g., tongue muscles or temporomandibular joint), and over 50% could be activated by hypoglossal (XII) nerve electrical stimulation. We propose that C1 and C2 DHs represent part of the caudal extension of the Vc, and that Vc and C1 and C2 DHs may act together as one functional unit to process nociceptive information from craniofacial and cervical tissues, including that from deep craniofacial tissues.

In vivo stimulation of sympathetic nervous system modulates osteoblastic activity in mouse calvaria

Previously, we demonstrated that epinephrine induced the expression of interleukin (IL)-6 mRNA via beta-adrenoceptors in cultured human osteoblastic cells. IL-6 is well known to modulate bone metabolism by regulating the development and function of osteoclasts and osteoblasts. Recently, restraint stress and intracerebroventricular injection of lipopolysaccharide (LPS) have been reported to induce the expression of IL-6 mRNA in peripheral organs in mice in which expression is mediated by the activation of the sympathetic nervous system. To prove the physiological role of sympathetic nerves in bone metabolism in vivo, we examined by RT-PCR analysis the effects of restraint stress and intracerebroventricular injection of LPS on IL-6 mRNA expression in mouse calvaria. The expression of IL-6 mRNA in mouse calvaria was stimulated by either restraint stress (30 min) or intracerebroventricular injection of LPS (50 ng/mouse, 60 min). The treatment of mice with the neurotoxin 6-hydroxydopamine (6-OHDA, 100 mg x kg-1 x day-1 ip for 3 days) inhibited LPS (icv)-induced expression of IL-6 mRNA in their calvaria. The expression of IL-6 mRNA induced by the restraint stress was not influenced by 6-OHDA, which destroys noradrenergic nerve terminals. Furthermore, pretreatment with a beta-blocker, propranolol (15 or 25 mg/kg ip), inhibited both stress- and LPS-induced increases in the level of IL-6 mRNA, but pretreatment with an alpha-blocker, phentolamine (5 mg/kg sc), did not inhibit them in mouse calvaria. In addition, treatment of calvaria with isoprenaline or norepinephrine increased IL-6 synthesis in the organ culture system. These results indicate that in vivo adrenergic stimulation modulates the osteoblastic activity in mouse calvaria via noradrenergic nerve terminals.

Making headway: the roles of Hox genes and neural crest cells in craniofacial development

Craniofacial development is an extraordinarily complex process requiring the orchestrated integration of multiple specialized tissues such as the surface ectoderm, neural crest, mesoderm, and pharyngeal endoderm in order to generate the central and peripheral nervous systems, axial skeleton, musculature, and connective tissues of the head and face. How do the characteristic facial structures develop in the appropriate locations with their correct shapes and sizes, given the widely divergent patterns of cell movements that occur during head development? The patterning information could depend upon localized interactions between the epithelial and mesenchymal tissues or alternatively, the developmental program for the characteristic facial structures could be intrinsic to each individual tissue precursor. Understanding the mechanisms that control vertebrate head development is an important issue since craniofacial anomalies constitute nearly one third of all human congenital defects. This review discusses recent advances in our understanding of neural crest cell patterning and the dynamic nature of the tissue interactions that are required for normal craniofacial development.

[Red cell phospholipid composition in children with neurological pathology]

Changes of red cell membrane phospholipid composition were studied in children with different neurological disorders--cerebral palsy, organic CNS damages and perinatal encephalopathy. The percentages of phosphatidylcholin and, in some cases, of phosphoglycerides increase depending on the disease type. The above changes were determined by craniocerebral innervation disturbances and concerned mainly the content of phosphatidylcholin, phosphatidylserine and phosphatidylethanolamin. The determination analysis established that the changes of erythrocytes phospholipid content correlated with clinical state severity and intellectual development of children, and to depend on the disease type and may affect directly development/disturbance of craniocerebral innervation and intellectual development. The age changes were shown to influence phosphatid acid percentage in the patients.

Topographic microsurgical anatomy of the paraclinoid carotid artery

In this publication, the authors describe the microanatomic topography of the entire paraclinoid area with respect to the paraclinoid segment of the internal carotid artery and its surrounding anatomical structures. Special attention was given to the borders of the paraclinoid area, cavernous sinus, arterial vessels, and cranial nerves passing through the region. The paraclinoid region was defined as a pyramid-formed space formed by the dural covering of the anterior clinoid process. The superior border is formed by the continuity of the anterior petroclinoid fold, anteriorly on the superior surface of the anterior clinoid process and medially in the direction of the diaphragma sellae. This dural sheet encircles the internal carotid artery and forms the so-called distal dural ring of the internal carotid artery. The medial border of the paraclinoid region is formed by the body of the sphenoid bone and the adjacent periosteal sheet. The inferior border is formed by a fibrous plate between the middle and anterior clinoid processes. This so-called proximal dural ring separates the venous compartments of the cavernous area from the paraclinoid area. The lateral border is formed by the lateral surface of the anterior clinoid process with its dural covering. The arterial supply of this region is provided by branches of the intracavernous carotid segment and the ophthalmic artery. The important nerves in close vicinity to the paraclinoidal area are the optic and the oculomotor nerves. Understanding and knowledge of the topographic anatomy of the paraclinoid area is essential for microsurgical exposure of this region.

Expression of immunoreactivity to neurokinin-1 receptor by subsets of cranial parasympathetic neurons: correlation with neuropeptides, nitric oxide synthase, and pathways

We examined the patterns of coexistence of immunoreactivity to the neurokinin-1 (NK(1)) tachykinin receptor, nitric oxide synthase, and neuropeptides in the sphenopalatine and otic ganglia of guinea pigs using a combination of multiple-labeling immunohistochemistry and pathway tracing in vitro. Most neurons had immunoreactivity to vasoactive intestinal peptide (85-96%) and neuropeptide Y (60%). Subpopulations of vasoactive intestinal peptide-immunoreactive neurons also had immunoreactivity to nitric oxide synthase (37-48%) or enkephalin (25-35%), but these formed mutually exclusive populations. Almost all neurons expressing NK(1) receptor immunoreactivity contained immunoreactivity to enkephalin, vasoactive intestinal peptide, and neuropeptide Y, but not nitric oxide synthase. Using a combination of retrograde axonal tracing and axonal crushing, we found that most neurons with immunoreactivity to nitric oxide synthase projected along the nasopalatine and ethmoidal nerves to the nasal mucosa. In contrast, most neurons with immunoreactivity to enkephalin followed the zygomatic nerve to the facial skin and lacrimal gland. Based on their peptide content, we conclude that the neurons with immunoreactivity to enkephalin and NK(1) receptor projected selectively to the skin. In both the sphenopalatine and the otic ganglia, about half of the neurons with NK(1) receptor immunoreactivity were surrounded by varicose nerve fibers with substance P immunoreactivity. Many of these fibers are likely to have originated in the trigeminal ganglion. Taken together, these observations establish a strong anatomical basis for a range of interactions between trigeminal and cranial parasympathetic pathways that may underlie pathophysiological conditions such as trigeminal neuralgia.

Frequency variations of discrete cranial traits in major human populations. IV. Vessel and nerve related variations

This concludes a series of descriptive statistical reports on discrete cranial traits in 81 human populations from around the world. Four variants classified as vessel and nerve related characters were investigated: patent condylar canal, supraorbital foramen; accessory infraorbital foramen; and accessory mental foramen. A significant asymmetric occurrence without any side preference was detected for the accessory mental foramen. Significant intertrait associations were found between the accessory infraorbital and supraorbital foramina in the panPacific region and Subsaharan African samples. The intertrait associations between the accessory infraorbital foramen and some traits classified as hypostotic were found mainly in the samples from the western part of the Old World, and those as hyperostotic traits in the samples from eastern Asian and the related population samples. With a few exceptions. the occurrence of a patent condylar canal and a supraorbital foramen was predominant in females, but the accessory infraorbital and accessory mental foramina were predominant in males. The frequency distributions of the traits showed interregional clinality and intraregional discontinuity. A temporal trend was found in the Northeast Asian region in the frequencies of the accessory infraorbital and accessory mental foramina. The diversity of modern human discrete cranial traits may at least in part be attributable to differential retention or intensification from an ancestral pattern.

Effects of catecholamines on calvarial bone resorption in vitro

Many important diseases in otolaryngology manifest through abnormal bone remodeling or destruction. The mechanisms for such pathological remodeling remain poorly understood. Bone is known to be innervated by norepinephrine-containing sympathetic nerves, and sympathectomy is known to induce bone resorption. The role, however, of norepinephrine as a potential bone-modulatory substance is unknown. Using the calvarial calcium release assay, we conducted the following experiment to evaluate the bone-modulatory activity of norepinephrine, the alpha-agonist octopamine, and the beta-agonist isoproterenol. Each agent was tested at 2 concentrations with and without parathyroid hormone. Norepinephrine was found to have no effect on calcium release. In contrast, octopamine at 10(-8) mol/L exerted a significant stimulatory effect on calcium release, and isoproterenol at 10(-6) mol/L exerted a significant inhibitory effect on parathyroid hormone-induced calcium release. The investigation suggests that a bimodal, concentration-dependent, receptor-specific model for catecholamine-mediated modulation of bone resorption may operate in calvarial bone.

Neurogenic inflammation in the context of migraine

Despite considerable research into the pathogenesis of idiopathic headaches, such as migraine, the pathophysiological mechanisms underlying them remain poorly understood. Although it is well established that the trigeminal nerve becomes activated during migraine, the consequences of this activation remain controversial. One theory, based on preclinical observations, is that activation of trigeminal sensory fibers leads to a painful neurogenic inflammation within the meningeal (dural) vasculature mediated by neuropeptide release from trigeminal sensory fibres and characterized by plasma protein extravasation, vasodilation, and mast cell degranulation. Effective antimigraine agents such as ergots, triptans, opioids, and valproate inhibit preclinical neurogenic dural extravasation, suggesting that this activity may be a predictor of potential clinical efficacy of novel agents. However, several clinical trials with other agents that inhibit this process preclinically have failed to show efficacy in the acute treatment of migraine in man. Alternatively, it has been proposed that painful neurogenic vasodilation of meningeal blood vessels could be a key component of the inflammatory process during migraine headache. This view is supported by the observation that jugular plasma levels of the potent vasodilator, calcitonin gene-related peptide (CGRP) are elevated during the headache and normalized by successful sumatriptan treatment. Preclinically, activation of trigeminal sensory fibers evokes a CGRP-mediated neurogenic dural vasodilation, which is blocked by dihydroergotamine, triptans, and opioids but unaffected by NK1 receptor antagonists that failed in clinical trials. These observations suggest that CGRP release with associated neurogenic dural vasodilation may be important in the generation of migraine pain, a theory that would ultimately be tested by the clinical testing of a CGRP receptor antagonist.

Neuroimaging in headache

Neuroimaging of primary headache syndromes, such as cluster headache and migraine, has begun to provide a glimpse of the neuroanatomical and physiological basis of the conditions. Although these headache types have been widely described as vascular, there is now considerable imaging and clinical evidence to suggest that they are primarily driven from the brain. The shared anatomical and physiological substrate for both of these clinical problems is the neural innervation of the cranial circulation. Functional imaging with positron emission tomography (PET) has shed light on the genesis of both syndromes, documenting activation in the midbrain and pons in migraine, and in the hypothalamic grey in cluster headache. These areas are involved not simply as a response to first division nociceptive pain impulses but specifically in each syndrome, probably in some permissive or dysfunctional role. In a recent PET study in cluster headache, as well as brain activation, tracer pooled in the region of the major basal arteries. This is likely to be due to vasodilatation of these vessels during the acute pain-attack and represents the first convincing activation of neural vasodilator mechanisms in humans. The author takes the view that the known physiology and pathophysiology of the systems involved dictate that these disorders should be collectively regarded as neurovascular headaches to place emphasis on the interaction between nerves and vessels, which is the underlying characteristic of these syndromes. Understanding this neurovascular relationship facilitates an understanding of the pain mechanisms, while characterising the CNS dysfunction will ultimately allow us to dissect out the basic pathogenesis of these disorders.

Catecholaminergic and acetylcholine esterase containing nerves of cranial and spinal dura mater in humans and rodents

The innervation of cranial and spinal dura mater in humans and rodents was studied by examining several dural zones (vascular, perivascular, intervascular) in different regions. Characterization and distribution of dural acetylcholinesterase-positive nerve fibers, catecholaminergic nerve fibers, and mast cells are analyzed and discussed. The results of chemical and surgical sympathectomy as well as the relationships between catecholaminergic nerve fibers and mast cells are studied. Our results are discussed in the light of possible implications in the physiopathology of dural algic syndromes including cephalalgia and spinal pain.

Nerve fibers innervating the cranial and spinal meninges: morphology of nerve fiber terminals and their structural integration

Pachymeninx and leptomeninx of cranial cavity and spine are considerably different in their collagenous fiber texture, cellular composition, vascularization, and innervation. The majority of meningeal nerve fibers terminate as free nerve endings whereas encapsulated and lamellated nerve terminals additionally occur in higher vertebrates including man. With respect to nerve fiber classification, arborization pattern, topography, and organization of the microenvironment at the termination site afferent and efferent nerve terminals are differentiated. Only the dura mater and the pial subcompartment of the leptomeninx possess the morphological prerequisites for neurogenic inflammation. In the current review, the results of morphological studies regarding the meningeal innervation including the sites of CSF (cerebrospinal fluid) production and absorption are discussed with emphasis on their structure-function relationships.

Somatic (craniocervical) tinnitus and the dorsal cochlear nucleus hypothesis

PURPOSE

Of all nonauditory sensory systems, only the somatosensory system seems to be related to tinnitus (eg, temporomandibular joint syndrome and whiplash). The purpose of this study is to describe the distinguishing characteristics of tinnitus associated with somatic events and to use these characteristics to develop a neurological model of somatic tinnitus.

MATERIALS AND METHODS

Case series.

RESULTS

Some patients with tinnitus, but no other hearing complaints, share several clinical features including (1) an associated somatic disorder of the head or upper neck, (2) localization of the tinnitus to the ear ipsilateral to the somatic disorder, (3) no vestibular complaints, and (4) no abnormalities on neurological examination. Pure tone and speech audiometry of the 2 ears is always symmetric and usually within normal limits. Based on these clinical features, it is proposed that somatic (craniocervical) tinnitus, like otic tinnitus, is caused by disinhibition of the ipsilateral dorsal cochlear nucleus. Nerve fibers whose cell bodies lie in the ipsilateral medullary somatosensory nuclei mediate this effect. These neurons receive inputs from nearby spinal trigeminal tract, fasciculus cuneatus, and facial, vagal, and glossopharyngeal nerve fibers innervating the middle and external ear.

CONCLUSIONS

Somatic (craniocervical) modulation of the dorsal cochlear nucleus may account for many previously poorly understood aspects of tinnitus and suggests novel tinnitus treatments.

Involvement of trigeminal subnucleus caudalis (medullary dorsal horn) in craniofacial nociceptive reflex activity

We have previously shown that an increase in electromyographic (EMG) activity of digastric (DIG) and masseter (MASS) muscles can be reflexly evoked by injection into the rat's temporomandibular joint (TMJ) region of the small-fibre excitant and inflammatory irritant mustard oil (MO). Since the trigeminal (V) subnucleus caudalis (Vc, i.e. medullary dorsal horn) has traditionally been viewed as an essential brainstem relay site of nociceptive information from craniofacial tissues, an EMG study was carried out in 45 anaesthetized rats to determine if Vc is involved in the MO-evoked increases in jaw muscle EMG activity. The effects of histologically confirmed surgical or chemical lesions of Vc on this evoked EMG activity were tested in different groups of rats. MO injection into the left TMJ region of intact rats evoked bilateral increases in EMG activity of DIG and MASS which could be significantly reduced by surgical transection of the left caudal brainstem at the obex level; MO injection into the right TMJ region in these same rats still readily evoked increases in EMG activity. A sagittal section medial to Vc or transection at the level of the second cervical spinal segment did not produce any significant reduction in the reflexly evoked EMG activity. Neurones in Vc, as opposed to fibres of passage, appear to be important for the MO-evoked EMG activity, since injection into Vc of the neurotoxic chemical ibotenic acid significantly reduced the mustard oil-evoked EMG activity. The Vc also appears to play a role in the activation of contralateral V motoneurons, as evidenced by the activation of the contralateral DIG and MASS muscles by the injection of MO into the left TMJ region of intact rats and by the reduction of this evoked EMG activity in the contralateral DIG and MASS of rats with a surgical transection or ibotenic acid lesion of the left Vc. These findings suggest that Vc may be a critical element in the neural pathways underlying the reflex responses evoked bilaterally in DIG and MASS muscles by noxious stimulation of the TMJ region.

Chronic treatment with repetitive transcranial magnetic stimulation inhibits seizure induction by electroconvulsive shock in rats

BACKGROUND

Studies in laboratory animals suggest that repetitive transcranial magnetic stimulation (rTMS) and electroconvulsive shock (ECS) increase seizure inhibition acutely. This study was designed to explore whether chronic rTMS would also have seizure inhibition properties.

METHODS

To this purpose we administered rTMS (Magstim Rapid) and sham rTMS twice daily (2.5 T, 4-sec train duration, 20 Hz) to two groups of 10 rats for 16 days. The rTMS coil was a 50-mm figure-8 coil held directly over the rat's head. Raters were blind to experimental groups. On days 11, 17, and 21 (5 days after the last rTMS) ECS was administered with a Siemens convulsator using three electrical charge levels. Variables examined were the presence or absence of seizures and seizure length (measured from the initiation of the tonic contraction until the end of the limb movement).

RESULTS

At day 11 rTMS had no effect on seizures, and both rTMS and sham rTMS animals convulsed equally. At day 17, however, rTMS-treated animals convulsed significantly less (both at presence/absence of seizures, and at seizure length) than sham rTMS animals. At day 21 the effects of rTMS had disappeared.

CONCLUSIONS

These findings suggest that rTMS administered chronically leads to changes in seizure threshold similar to those reported for ECS and ECT; however, these effects were short-lived.

[Reference values for the central motor conduction time and silent period obtained by the transcranial magnetic stimulation]

INTRODUCTION

Normal values of reference to transcranial magnetic stimulation for the motor central conduction time (CCT) and silent period (SP) is recorded in 30 healthy control subjects over abductor pollicis brevis.

MATERIAL AND METHODS

We get for the CCT four measurements: two with low intensity of stimulus, 5% plus the motor threshold, with and without facilitation (CCT1 and CCT1 fac.); and two with high intensities of stimulus, elevating the magnetic stimulation intensity to 1.5 times the threshold (CCT2 and CCT2 fac.).

RESULTS AND CONCLUSIONS

The mean and standard deviation of each measurement are: CCT1: 9.34 +/- 1.19, CCT1 fac.: 7.12 +/- 1.1. CCT2: 8.84 +/- 1.05 and CCT2 fac.: 6.57 +/- 1.05. Given that the CCT and SP doesn't follow a normal distribution, the medium and the 5-95% percentiles for the normal values of reference are calculated; there are: CCT1: 7.15-11.32, CCT1 fac: 5.27-9.42. CCT2: 7.05-10.73 and CCT2 fac: 4.91-9.14. For the silent period gets only one measurement employing high intensities. These last measurement were recorded in two localizations: on vertex and on motor area, selecting the greater duration. Given the great individual variability of this period in normal population absolute and ratio for the difference duration of SP between both sides are calculated. The latency of the SP is 50.2 +/- 5.99, 95 percentiles 39.1-64.63, the duration 151 +/- 32.51, 95 percentiles 102.63-239.55. The total SP measured from the discharge of the stimulus to the end of the silent period is 201.71 +/- 33.27; 95 percentiles: 151.39-296.4. The comparison of both hemispheres would give us pathological security for the 99.99% of the population for more than 14.94 ms of absolute difference, and for less of the 79.81% of ratio difference. A summary of the discoveries of the silent period in different pathologies is contributed in the discussion.

Neuro-osteology

Neuro-osteology stresses the biological connection during development between nerve and hard tissues. It is a perspective that has developed since associations were first described between pre-natal peripheral nerve tissue and initial osseous bone formation in the craniofacial skeleton (Kjaer, 1990a). In this review, the normal connection between the central nervous system and the axial skeleton and between the peripheral nervous system and jaw formation are first discussed. The early central nervous system (the neural tube) and the axial skeleton from the lumbosacral region to the sella turcica forms a unit, since both types of tissue are developmentally dependent upon the notochord. In different neurological disorders, the axial skeleton, including the pituitary gland, is malformed in different ways along the original course of the notochord. Anterior to the pituitary gland/sella turcica region, the craniofacial skeleton develops from prechordal cartilage, invading mesoderm and neural crest cells. Also, abnormal development in the craniofacial region, such as tooth agenesis, is analyzed neuro-osteologically. Results from pre-natal investigations provide information on the post-natal diagnosis of children with congenital developmental disorders in the central nervous system. Examples of these are myelomeningocele and holoprosencephaly. Three steps are important in clinical neuro-osteology: (1) clinical definition of the region of an osseous or dental malformation, (2) embryological determination of the origin of that region and recollection of which neurological structure has developed from the same region, and (3) clinical diagnosis of this neurological structure. If neurological malformation is the first symptom, step 2 results in the determination of the osseous region involved, which in step 3 is analyzed clinically. The relevance of future neuro-osteological diagnostics is emphasized.

Anterior facial nerve rerouting in cranial base surgery: a comparison of three techniques

Anterior rerouting of the facial nerve is a maneuver designed to enhance exposure of the jugular foramen and carotid canal during resection of cranial base tumors. Our clinical impression is that the degree of additional exposure afforded by moving the facial nerve varies considerably according to both anatomic variations and the technique used. Three possible techniques exist based on the extent of facial nerve mobilization and point of rotation: canal wall up-second genu pivot point (CWU-2G); canal wall down-second genu pivot point (CWD-2G); and canal wall down-first genu pivot point (CWD-IG). We anatomically studied 20 human cadaver heads to establish clinically relevant guidelines for the selective use of these techniques. At the level of the dome of the jugular bulb, the facial nerve mobilized anteriorly a mean of 4.2 mm for CWU-2G, 10 mm for CWD-2G, and 14 mm for CWD-1G. Detailed analysis of numerous measurements and rotation angles suggests that the typical exposure afforded by the various rerouting techniques is as follows: CWU-2G, complete exposure of the jugular bulb; CWD-2G, exposure of the jugular bulb and a mean of 6 mm of the posterior aspect of the carotid artery; and CWD-IG, exposure of the jugular bulb and entire carotid genu. Minimizing the amount of facial nerve manipulation needed to achieve sufficient surgical exposure helps optimize postoperative functional status.

Human palatal growth evaluated on medieval crania using nerve canal openings as references

The purpose of this investigation was to measure postnatal lengthening and widening of the hard palate by use of nerve canal openings as references. The relationship of the dentition to the greater palatine foramina was also investigated. Thirty-nine medieval dry skulls were examined, 22 from children and 17 from adults. All crania were photographed at a 1.1 scale. The dimensions of the maxilla and the location of the dentition were determined from the photographs. The study showed that palatal growth in length in the sagittal plane takes place anterior to the greater palatine foramen. The growth increment in the area between the incisive foramen and the transverse palatine suture is more pronounced than the growth increment in the area between the transverse palatine suture and the greater palatine foramen. The distance from the greater palatine foramina to the posterior margin of the palate did not increase significantly with age. The growth in width seems to continue into adult life. The first permanent molars and the surrounding bone are moved forwards in relation to the greater palatine foramina during growth. The space for the developing maxillary premolars and molars therefore has to be obtained by growth in the transverse palatine suture.

Morphometric investigations of the connections between the posterior C-1 root and the accessory nerve in the human cranial cervical region

The anastomosis of the spinal section of the accessory nerve and the posterior C-1 root was examined in eight human corpses at the light-microscopical level by image analysis. The numbers of nerve fibers caudal and cranial to the anastomosis were compared. The morphometric data suggest that somatic efferent fibers of the spinal accessory nerve extend to proprioceptors in the sternocleido-mastoideus and trapezius muscles.

Biosynthetic processing of preprovasoactive intestinal polypeptide in parasympathetic neurons of the sphenopalatine ganglion

The precursor for rat vasoactive intestinal polypeptide (preproVIP) is processed by proteolytic cleavage into a signal peptide and five further functional domains: preproVIP 22-79, peptide histidine isoleucine (PHI), preproVIP 111-122, VIP, and preproVIP 156-170. To investigate the biosynthetic processing of preproVIP in peripheral parasympathetic neurons, the sphenopalatine ganglion and one of its projection areas, the nasal mucosa, were used. By immunohistochemistry it was shown that in the sphenopalatine ganglion, preproVIP-derived peptides are localized mainly in neuronal cell bodies, whereas in the nasal mucosa immunoreactivity was found only in nerve fibers and terminals. The peptides were quantified and characterized by radioimmunoassay, HPLC, and gel chromatography using antisera specific for the different precursor products. In the rat sphenopalatine ganglion, the different peptides were found in approximately equimolar amounts, with the exception of PHI and its C-terminally extended variant, PHV, which were present at considerably lower concentrations. However, in the nasal mucosa there was a preferential accumulation of VIP to at least three times the concentration of any of the other peptides. Our results suggest that all preproVIP-derived peptides are present and processed in the sphenopalatine ganglion but that there is a selective accumulation of VIP in the nerve terminals. This indicates that VIP is physiologically the most important transmitter among the preproVIP-derived peptides in parasympathetic nerves originating in the sphenopalatine ganglion.

Which structures are sensitive to painful transcranial electric stimulation?

Electric transcranial stimulation (TCS) is useful for clinical studies. It is, however, painful and not generally used for awake subjects. By means of topical anaesthesia and nerve blockades we wanted to find out which structures of the scalp and cranium are sensitive to electric TCS. Altogether 21 subjects participated in the present study. Our data show that pain experienced by the subjects during electric TCS is brought about by activation of the pain receptors in the scalp under the stimulating electrodes. Topical anaesthetic cream is incapable of attenuating this pain. The periosteum does not seem to be much more sensitive electric stimulation than rest of the scalp. Furthermore, contractions of facial and neck muscles do not seem to have a significant role in pain generation in electric TCS. Pain can be prevented if sufficiently large areas of the scalp are properly anaesthetized before stimulation by e.g. blockade of the major nerves responsible for the sensation of the stimulus area.

Effects of unilateral cranial sympathectomy either alone or with sensory nerve sectioning on pedicle growth in red deer (Cervus elaphus)

In a previous study (Li et al. [1993], J. Exp. Zool., 267:188-197) sensory nerve sectioning had no effect on the timing of pedicle growth. The aim of the present study was to determine whether sensory nerve sectioning in conjunction with sympathectomy would influence pedicle growth. Twelve intact male red deer calves were allocated to treatment before any pedicle growth as follows: 1) unilateral sensory nerve removal (USX, n = 5), 2) unilateral superior cervical ganglionectomy (SGX, n = 4), or 3) both USX and SGX (SG/USX, n = 3). The calves were observed weekly. In all cases the untreated side was the control. Pedicle initiation was measured with a pedicle detector and after initiation, growth was measured with a ruler. When the treated pedicles reached a length of 60 mm the calves were killed and tissues from the pedicle were examined immunohistochemically for nerves. No large bundles of nerves were observed in the treated pedicle although a few fine fibres were present. All calves grew pedicles. There were no significant differences in the timing of pedicle initiation either within treatment or between treatments. All denervated pedicles grew faster than controls and were consequently higher at examination. The fact that pedicle growth took place despite reduced innervation indicates that a continuous neural connection is not a pre-requisite for normal pedicle growth.

The anatomy of the inferior petrosal sinus, glossopharyngeal nerve, vagus nerve, and accessory nerve in the jugular foramen

PURPOSE

To define the variations of the courses of the cranial nerves and the inferior petrosal sinuses as they enter and traverse the jugular foramen.

METHODS

Thirty-nine cadaveric specimens containing the jugular foramen were scanned with 1-mm contiguous axial and coronal CT sections. Each specimen was dissected to evaluate the position of the cranial nerves and inferior petrosal sinus as they entered the jugular foramen.

RESULTS

The glossopharyngeal nerve entered the most superior, anterior, and medial aspect of the jugular foramen and descended in the anterior portion of the jugular foramen, often within a groove. The vagus and accessory nerves could not be separated by CT. They entered the jugular foramen most often anterior or anterior and inferior to the jugular spine of the temporal bone and descended in a position ranging from medial to anterior to the jugular vein. The inferior petrosal sinus most often coursed inferior to the horizontal portion of the glossopharyngeal nerve and entered the jugular system in the jugular foramen, at the exocranial opening or below the skull base. A pars nervosa and pars venosa could be identified only at the endocranial opening, where the jugular spine separated the pars nervosa containing the inferior petrosal sinus and three cranial nerves from the pars venosa containing the jugular vein.

CONCLUSION

Our evaluation demonstrated anatomic variation in the area of the jugular foramen.

Facial nerve management in cranial base surgery

This study reviewed 124 patients who required facial nerve manipulation during cranial base surgery. Most of them underwent only nerve displacement or selective transection for improved surgical access to the cranial base (70 and 34, respectively). Fourteen patients had the facial nerve resected for oncologic reasons and repaired with primary nerve grafting. Most patients regained quite satisfactory facial function with quality correlating with the degree of nerve injury. Six patients had facial nerve resected as part of oncologic palliation and had the facial deficit rehabilitated with regional tissue. A correlation between preoperative facial nerve weakness and the quality of nerve graft function was not found. An oncologic correlation, however, is suggested (patients with preoperative weakness had less favorable prognosis). Overall, patients who require facial nerve resection for oncologic reasons do not do as well as those with normal preoperative function.

Extracranial blood flow, pain and tenderness in migraine. Clinical and experimental studies

Migraine pain has traditionally been ascribed to dilatation of primarily extracranial arteries. Such dilatation has, however, not been demonstrated so far. Studies of microcirculation reveal no major hyperperfusion or ischemia in the temporal muscle or the subcutaneous tissue in the temporal region during attacks of migraine. However, a reduction in the orthostatic reactivity of the subcutaneous arterioles was observed on the side of the headache. Increased tenderness of the pericranial myofascial tissues is observed during migraine attacks, particularly on the side of the headache. Increased tension of pericranial muscles on the other hand is not a constant finding and migraine attacks are not induced by experimentally increased tension of the temporal and masseter muscles. Extracranial pain and tenderness may, however, be induced experimentally by intramuscular injections of hypertonic saline and potassium chloride as well as of endogenous substances like bradykinin with 5-hydroxytryptamine and bradykinin with substance P. The extracranial arteries and myofascial structures are both supplied by unmyelinated trigeminal sensory nerve fibers containing a variety of neuropeptides which are released during migraine attacks. Axonal reflexes between extracranial arteries and neighbouring myofascial tissues as well as referred pain mechanisms may account for the observed tenderness during migraine attacks.

Study of sympathetic innervation of cranial bones by axonal transport of horseradish peroxidase in the rat: preliminary findings

This study performed by intraneuronal tracing directly demonstrates the presence of sympathetic postganglionic fibers in the cranial vault of the rat. Superior cervical sympathetic ganglia were injected with horseradish peroxidase (HRP), and after a 48-hour period, to permit anterograde axonal transport, the animals were sacrificed after in situ perfusion. An area of the calvaria that included portions of the frontal and parietal bones was fixed, decalcified and sectioned. HRP-containing axons were localized in the developing frontal and parietal bones of the calvaria. Adrenergic innervation was not demonstrated in sutural tissue (superior sagittal, coronal or metopic) by this technique. To our knowledge, this study is the first to trace sympathetic nerve fibers in the rat calvaria by intra-axonal transport of HRP.

Early events in mammalian craniofacial morphogenesis

Head-trunk differences are well established in the most primitive vertebrates, and are clear from early developmental stages of all modern forms. The boundary between the two regions is not constant in all vertebrate classes in terms of the number of occipital somites. The occipital region is in some respects a transitional zone, giving rise to trunk-like somitic derivatives in the head. It is also highly specialised, providing a unique population of neural crest cells that are essential for formation of the aorticopulmonary septum (which divides the outflow tract of the heart) in mammals and birds. In the preoccipital hindbrain, rhombomeres represent a segmental structural pattern that is quite distinct from that of the somites, with a segment-specific pattern of gene expression. Expression of some of these genes in mesenchyme close to the primitive streak at earlier stages suggests that this pattern may be established at the time of neural induction. Mammalian embryos have taken cranial specialization further than other classes of vertebrate, particularly in relation to the pattern of development and eventual structural complexity of the forebrain. Mammalian specialisations of craniofacial development are described through references to studies on cranial neurulation, on cranial neural crest cell migration, and on the possible morphogenetic roles of extracellular matrix components.

Adrenergic innervation of the calvarium of the neonatal rat. Its relationship to the sagittal suture and developing parietal bones

The presence and distribution of adrenergic nerves in the developing calvarium of the newborn rat documented by means of the formaldehyde-induced fluorescence technique in rats aged 2 or 7 days. Nerve fibres exhibiting catecholamine-specific fluorescence were seen within the developing calvarium of all animals. In coronal sections, these fibres could be seen in the developing bone, especially in the lamina interna, while in sagittal sections, they were seen to traverse the tissue to reach the central of the diploë. These fibres originate from a denser plexus within the dura mater. Especially in the younger age group, the fluorescent fibres often exhibited an immature appearance, being coarse and devoid of varicosities. In the older animals the fibres were often varicose. The sutural tissue proper was always found to be devoid of adrenergic innervation. The possible origin and functional significance of the adrenergic innervation in the developing bone in relation to skull growth and sutural closure are discussed.

Response properties of nociceptive and non-nociceptive neurons in the rat's trigeminal subnucleus caudalis (medullary dorsal horn) related to cutaneous and deep craniofacial afferent stimulation and modulation by diffuse noxious inhibitory controls

An electrophysiological study was carried out in anesthetized rats to characterize the properties of single neurons in trigeminal (V) subnucleus caudalis. Each neuron was functionally classified in terms of its cutaneous mechanoreceptive field properties as low-threshold mechanoreceptive (LTM), wide dynamic range (WDR) or nociceptive-specific (NS), and its responsiveness was also tested to electrical stimulation of hypoglossal (XII) nerve muscle afferents. Some neurons were also tested with noxious stimulation of the tail or forepaw for the presence of diffuse noxious inhibitory controls (DNIC) of evoked responses. A mechanoreceptive field localized to the ipsilateral orofacial region was a feature of all the neurons which were located in laminae I-VI; the LTM neurons predominated in laminae III/IV whereas the nociceptive (WDR, NS) were located in the superficial and especially deeper laminae of caudalis. The majority of the WDR and NS neurons were also activated by noxious heating as well as by noxious mechanical and electrical stimulation of their orofacial mechanoreceptive field, and in contrast to our previous studies in cats, most of these caudalis nociceptive neurons received C fiber as well as A fiber cutaneous afferent inputs. In contrast to the LTM neurons, but consistent with our previous data in cats, many of the nociceptive neurons also received convergent excitatory inputs from XII muscle afferents, and the stimulus-response functions of the WDR neurons indicated that they were capable of coding the intensity of A and C fiber craniofacial muscle afferent inputs as well as those from cutaneous afferents. The study has also documented for the first time that muscle afferent-evoked responses as well as those evoked by cutaneous afferent inputs to nociceptive neurons are subject to DNIC. These findings indicate that subnucleus caudalis plays an important role in the transmission of superficial and deep nociceptive information from the craniofacial region of the rat, and also reveal that responses of the nociceptive neurons evoked by deep as well as superficial afferent inputs can be powerfully modulated by other nociceptive influences originating from widespread parts of the body.

Contributions of placodal and neural crest cells to avian cranial peripheral ganglia

The method of embryonic tissue transplantation was used to confirm the dual origin of avian cranial sensory ganglia, to map precise locations of the anlagen of these sensory neurons, and to identify placodal and neural crest-derived neurons within ganglia. Segments of neural crest or strips of presumptive placodal ectoderm were excised from chick embryos and replaced with homologous tissues from quail embryos, whose cells contain a heterochromatin marker. Placode-derived neurons associated with cranial nerves V, VII, IX, and X are located distal to crest-derived neurons. The generally larger, embryonic placodal neurons are found in the distal portions of both lobes of the trigeminal ganglion, and in the geniculate, petrosal and nodose ganglia. Crest-derived neurons are found in the proximal trigeminal ganglion and in the combined proximal ganglion of cranial nerves IX and X. Neurons in the vestibular and acoustic ganglia of cranial nerve VIII derive from placodal ectoderm with the exception of a few neural crest-derived neurons localized to regions within the vestibular ganglion. Schwann sheath cells and satellite cells associated with all these ganglia originate from neural crest. The ganglionic anlagen are arranged in cranial to caudal sequence from the level of the mesencephalon through the third somite. Presumptive placodal ectoderm for the VIIIth, the Vth, and the VIIth, IXth, and Xth ganglia are located in a medial to lateral fashion during early stages of development reflecting, respectively, the dorsolateral, intermediate, and epibranchial positions of these neurogenic placodes.

[Osteolytic and osteoplastic changes in the base of the skull in computerized tomography]

Computerized tomography of the base of the skull has gained importance due to improved spatial resolution. In spite of lesser resolution than with conventional x-rays, it offers a great deal of additional information, based on the axial view and the method of digital image manipulation with subsequent examination at the independent viewing console. With increasing experience, the information gained from CT in these cases has proved superior to the results of conventional tomography.