RESUMO
O Tronco encefálico (TE) é uma estrutura singular do sistema nervoso central, pois nele passam tratos sensoriais ascendentes da medula espinal, tratos sensoriais da cabeça e do pescoço, os tratos descendentes motores originados no prosencéfalo (divisão mais rostral do encéfalo), e as vias ligadas aos centros de movimento dos olhos. Contém ainda os núcleos dos nervos cranianos e está envolvido na regulação do nível de consciência através de projeções ao prosencéfalo oriundas da formação reticular. Todas essas estruturas coexistem em um espaço muito exíguo, o que faz com que o TE seja um local muito sensível às alterações patológicas, sendo que os pacientes apresentam muitos sinais neurológicos mesmo com lesões muito pequenas nesse local. Compreender a anatomia interna do TE é essencial para o diagnóstico neurológico e a prática da medicina clínica. Outros profissionais da saúde também se beneficiam desse conhecimento para melhor manejo dos seus pacientes neurológicos. Essa revisão apresenta detalhes da anatomia macroscópica e microscópica do bulbo, bem como seus correlatos clínicos frente às lesões mais comuns dessa divisão particular do TE, conhecidas como síndromes bulbares.
The brainstem is a unique structure in the central nervous system, since it gives way to ascending sensory tracts from the spinal cord, sensory tracts from the head and neck, motor descending tracts originating from the forebrain, and the pathways connected to the eye movement centers. It also contains the cranial nerve nuclei and is involved in the regulation of consciousness levels through projections to the forebrain originating in the reticular formation. All these structures coexist in a very small space, which makes the brainstem very sensitive to pathological changes, with patients presenting several neurological symptoms even with very small brainstem lesions. Understanding the internal anatomy of the brainstem is essential for neurological diagnosis and the practice of clinical medicine. Other health professionals also benefit from this knowledge to better manage their neurological patients. This review presents detailed information on the macroscopic and microscopic anatomy of the medulla, as well as its clinical correlates in the face of the most common lesions of this particular division of the brainstem, known as medullary syndromes.
Assuntos
Humanos , Síndrome Medular Lateral/diagnóstico , Bulbo/anatomia & histologia , Tratos Piramidais/anatomia & histologia , Formação Reticular/anatomia & histologia , Núcleo Espinal do Trigêmeo/anatomia & histologia , Área Postrema/anatomia & histologia , Pedúnculo Cerebral/anatomia & histologiaRESUMO
Located in the lower brainstem, the paratrigeminal nucleus (Pa5) is related to cardiorespiratory autonomic reflex functions. To characterize the structures' role in blood pressure regulation and the cardiovascular reflex responses Pa5 unit activity was evaluated during a phenylephrine-produced pressor response in non-anaesthetized rats by means of simultaneous many-unit recording. Ninety five percent of the identified Pa5 responded to baroreceptor stimulation, 77% increasing and 23% decreasing firing rates. Cross-correlation analysis of neuron electrical behavior referenced to the heart beat event revealed that 65% of the featured cardiac cycle-locked rhythmic activity. The identification of neurons that change firing rates in response to increases of arterial pressure with cardiac cycle-locked rhythmic activity, further supports for a role for the nucleus in moment to moment control of blood pressure. The largest changes in firing rate occurred in the units with low resting firing rates in response to the ascending phase of the pressor event. Thus, the group displaying both cardiac cycle-locked and other rhythmic activities within the ranges of cardiac and respiratory rates or arterial pressure low frequencies, is probably the most influential regarding homoeostatic reflex responses. The findings advance the notion that the dynamic control of blood pressure involves lower brainstem integration of cardiac and respiratory reflexes.
Assuntos
Sistema Nervoso Autônomo/fisiologia , Pressão Sanguínea/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Bulbo/fisiologia , Neurônios/fisiologia , Fenômenos Fisiológicos Respiratórios , Potenciais de Ação/fisiologia , Anestésicos/farmacologia , Animais , Sistema Nervoso Autônomo/anatomia & histologia , Vias Autônomas/anatomia & histologia , Vias Autônomas/fisiologia , Frequência Cardíaca/fisiologia , Masculino , Bulbo/anatomia & histologia , Ratos , Ratos Wistar , Reflexo/fisiologia , Núcleo Espinal do Trigêmeo/anatomia & histologiaRESUMO
Located in the lower brainstem, the paratrigeminal nucleus (Pa5) is related to cardiorespiratory autonomic reflex functions. To characterize the structures' role in blood pressure regulation and baroreflex response, both resting cardiovascular parameters and reflex responses were evaluated during phenylephrine-produced pressor responses in non-anaesthetized rats with or without bilateral chemical Pa5 ablation. The Pa5-ablated animals, in contrast to the Pa5-intact control animals, presented increased resting arterial pressure (115+/-4 vs. 100+/-3 mm Hg), decreased heart (293+/-10 vs. 315+/-7 bpm) and increase of the respiratory (104+/-3 vs. 94+/-5 rpm) rates, larger pressor responses and reduced baroreflex index (1.6+/-0.2 vs. 2.8+/-0.2, p<0.05). The cardiovascular changes, compatible to those produced by nucleus of the solitary tract (NTS) lesions in non-anaesthetized rats, indicate a reduction of both the sympathetic and cardiac components of the baroreflex response. Further analyses showed the Pa5 mediates reflex responses to smaller blood pressure increases, while the NTS would be predominantly active in surges over 40 mm Hg. Thus, the integrity of the Pa5 is important for resting blood pressure maintenance as for a full baroreceptor response.
Assuntos
Sistema Nervoso Autônomo/fisiologia , Barorreflexo/fisiologia , Pressão Sanguínea/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Bulbo/fisiologia , Neurônios/fisiologia , Anestésicos/farmacologia , Animais , Sistema Nervoso Autônomo/anatomia & histologia , Denervação , Frequência Cardíaca/fisiologia , Ácido Ibotênico , Masculino , Bulbo/anatomia & histologia , Neurotoxinas , Ratos , Ratos Wistar , Núcleo Solitário/fisiologia , Sistema Nervoso Simpático/anatomia & histologia , Sistema Nervoso Simpático/fisiologia , Núcleo Espinal do Trigêmeo/anatomia & histologiaRESUMO
A correlation between pain sensation and neuronal c-fos expression has been analyzed following experimental rapid maxillar expansion (RME). Adult male Wistar rats were anaesthetized and divided into three groups: animals that received an orthodontic apparatus, which was immediately removed after the insertion (control), animals that received an inactivated orthodontic apparatus (without force), and animals that received an orthodontic apparatus previously activated (140 g force). After 6, 24, 48, or 72 h, the animals were re-anaesthetized, and perfused with 4% paraformaldehyde. The brains were removed, fixed, and sections containing brain structures related to nociception were processed for Fos protein immunohistochemistry (IHC). The insertion of the orthodontic apparatus with 140 g was able to cause RME that could be seen by radiography. The IHC results showed that the number of activated neurons in the different nuclei changed according to the duration of appliance insertion and followed a temporal pattern similar to that of sensations described in clinics. The animals that received the orthodontic apparatus without force did not show RME but a smaller c-fos expression in the same brain structures. In conclusion, we demonstrate that orthodontic force used for palate disjunction activates brain structures that are related to nociception, and that this activation is related to the pain sensation described during orthodontic treatment.
Assuntos
Vias Aferentes/metabolismo , Encéfalo/metabolismo , Maxila/inervação , Neurônios Aferentes/metabolismo , Nociceptores/metabolismo , Dor/fisiopatologia , Vias Aferentes/anatomia & histologia , Animais , Biomarcadores/metabolismo , Encéfalo/anatomia & histologia , Mapeamento Encefálico , Imuno-Histoquímica , Masculino , Maxila/lesões , Maxila/cirurgia , Aparelhos Ortodônticos/efeitos adversos , Dor/etiologia , Dor/metabolismo , Substância Cinzenta Periaquedutal/anatomia & histologia , Substância Cinzenta Periaquedutal/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Wistar , Fatores de Tempo , Núcleo Espinal do Trigêmeo/anatomia & histologia , Núcleo Espinal do Trigêmeo/metabolismoRESUMO
The paratrigeminal nucleus (Pa5), an input site for spinal, trigeminal, vagus and glossopharyngeal afferents, is a recognized site for orofacial nociceptive sensory processing. It has efferent connections to brain structures associated with nociception and cardiorespiratory functions. This study aimed at determining the function of the Pa5 on the cardiovascular component of the somatosensory reflex (SSR) to sciatic nerve stimulation (SNS) in paralyzed and artificially-ventilated rats following Pa5 chemical lesions (ibotenic acid), synaptic transmission blockade (CoCl(2)), local anaesthetics (lidocaine) or desensitization of primary afferent fibers (capsaicin). The pressor response to sciatic nerve stimulation at 0.6 mA and 20 Hz (14+/-1 mm Hg) was strongly attenuated by contra- (-80%) or bilateral (-50%) paratrigeminal nucleus lesions. Ipsilateral Pa5 lesions only attenuated the response to 0.1 mA, 20 Hz SNS (-55%). Cobalt chloride or lidocaine injected in the contralateral paratrigeminal nucleus also attenuated the SSR. In capsaicin-treated animals, the pressor responses to 0.1 mA were abolished, whereas the responses to SNS at 0.6 mA were increased from 65 to 100% depending on the stimulus frequency. The paratrigeminal nucleus receives both, excitatory and inhibitory components; the later apparently involving capsaicin-sensitive fiber inputs mostly to the ipsilateral site whereas the capsaicin insensitive excitatory components that respond to high or low frequency stimulation, respectively, target the contralateral and ipsilateral sites. Thus, the paratrigeminal nucleus mediates excitatory and inhibitory components of the somatosensory reflex, representing a primary synapse site in the brain for nociceptive inputs from the sciatic innervation field.
Assuntos
Vias Aferentes/fisiologia , Pressão Sanguínea/fisiologia , Bulbo/fisiologia , Nociceptores/fisiologia , Nervo Isquiático/fisiologia , Núcleo Espinal do Trigêmeo/fisiologia , Animais , Capsaicina/farmacologia , Denervação , Estimulação Elétrica , Potenciais Pós-Sinápticos Excitadores/fisiologia , Lateralidade Funcional/fisiologia , Mediadores da Inflamação/farmacologia , Masculino , Bulbo/anatomia & histologia , Inibição Neural/fisiologia , Dor/fisiopatologia , Terminações Pré-Sinápticas/fisiologia , Ratos , Ratos Wistar , Reflexo/fisiologia , Transmissão Sináptica/fisiologia , Núcleo Espinal do Trigêmeo/anatomia & histologia , Vasoconstrição/fisiologiaRESUMO
Many pharmacological and surgical treatments are available for the treatment of chronic facial pain. However, many of them are expensive and often very ineffective. Past publications suggested that bulbar trigeminal stereotactic nucleotractotomy is a very useful procedure for the treatment of neuropathic or oncologic facial pain. The authors describe the results of treatment with stereotactic nucleotractotomy in 58 patients with chronic facial pain. The intensity of the pain was evaluated according to the visual analogue scale, and daily life activities were also evaluated. The conclusion was that this procedure is a safe and effective method for treatment of postherpetic neuralgia, Wallenberg's syndrome and oncologic facial pain but not of trigeminal neuralgia.