Complicated giant colonic diverticulum: imaging-based diagnosis

A 66-year-old male from Venezuela with history of high blood pressure and diverticulosis is being studied on an outpatient basis for abdominal pain and weight loss of several months of evolution. He presented to the emergency department due to worsening abdominal pain in the last 48 hours and fever. His abdomen was mildly tender to palpation in the left hypochondrium but did not exhibit signs of peritonitis. An abdominal x-ray was performed, revealing an oval, smooth-walled mass located in the left upper quadrant that contained a gas-fluid level. An outpatient abdominal CT scan performed two months earlier showed an intraabdominal, 14.8x10x16cm air cystic lesion, proposing giant colonic diverticulum as first diagnostic possibility. Given the findings of the abdominal x-ray, urgent abdominal CT was requested (image 3) with results suggestive of sigmoid-dependent giant diverticulum, complicated by probable superinfection and torsion of the sigma at its base. Considering the suspected diagnosis, the patient underwent diverticulectomy, demonstrating purulent content inside. Histopathology confirmed the diagnosis. Evolution after surgery was favourable and the patient was discharged on the sixth postoperative day. (AU)

Complicated giant colonic diverticulum: imaging-based diagnosis.

A 66-year-old male from Venezuela with history of high blood pressure and diverticulosis is being studied on an outpatient basis for abdominal pain and weight loss of several months of evolution. He presented to the emergency department due to worsening abdominal pain in the last 48 hours and fever. His abdomen was mildly tender to palpation in the left hypochondrium but did not exhibit signs of peritonitis. An abdominal x-ray was performed, revealing an oval, smooth-walled mass located in the left upper quadrant that contained a gas-fluid level. An outpatient abdominal CT scan performed two months earlier showed an intraabdominal, 14.8x10x16cm air cystic lesion, proposing giant colonic diverticulum as first diagnostic possibility. Given the findings of the abdominal x-ray, urgent abdominal CT was requested (image 3) with results suggestive of sigmoid-dependent giant diverticulum, complicated by probable superinfection and torsion of the sigma at its base. Considering the suspected diagnosis, the patient underwent diverticulectomy, demonstrating purulent content inside. Histopathology confirmed the diagnosis. Evolution after surgery was favourable and the patient was discharged on the sixth postoperative day.

Síndrome de desmielinización osmótica, a propósito de un caso / Osmotic demyelination syndrome, a case report

El síndrome de desmielinización osmótica, antes conocido como mielinólisis central pontina, es una enfermedad que ocurre en pacientes con hiponatremia grave en los cuales se realiza una corrección rápida del sodio. Clínicamente, se presenta como una parálisis seudobulbar que consiste en tetraparesia, encefalopatía, rigidez, ataxia y movimientos anormales. El síndrome de desmielinización osmótica es una enfermedad desmielinizante no inflamatoria, secundaria a edema neuronal intenso que se produce en la protuberancia y otras regiones fuera de la protuberancia. Es una patología muy poco frecuente. Sin embargo, tiene muy mal pronóstico, y la rehabilitación es el único tratamiento eficaz. Se presenta el caso de un paciente de 51 años de edad con cuadro de déficit neurológico altamente progresivo después de la corrección rápida de una hiponatremia, con tetraparesia, encefalopatía y rigidez en los días siguientes. El paciente requirió intubación orotraqueal debido al deterioro clínico. Fue diagnosticado mediante una tomografía axial computarizada (TAC) cerebral y se confirmó el diagnóstico mediante resonancia magnética (RM).

Osmotic demyelination syndrome, previously known as central pontine myelinolysis, is a known disorder in patients with severe hyponatremia in whom rapid sodium correction is performed. It is clinically described as a pseudobulbar palsy, comprised of tetraparesis, encephalopathy, rigidity, ataxia and abnormal movements. It consists of a non-inflammatory demyelination secondary to severe neuronal edema at the pons and other extrapontine locations. It is a very rare pathology, with a poor prognosis and whose only treatment is rehabilitation. A case of a 51-year-old man with fast progressive neurological deficit following rapid correction of severe hyponatremia is presented. The patient required orotracheal intubation due to clinical deteroriation and was diagnosed by computed tomography (CT) and confirmed by magnetic resonance imaging (MRI)

The potential role of serotonergic mechanisms in the spinal oxytocin-induced antinociception.

The role of oxytocin (OXT) in pain modulation has been suggested. Indeed, hypothalamic paraventricular nuclei (PVN) electrical stimuli reduce the nociceptive neuronal activity (i.e., neuronal discharge associated with activation of Aδ- and C-fibers) of the spinal dorsal horn wide dynamic range (WDR) cells and nociceptive behavior. Furthermore, raphe magnus nuclei lesion reduces the PVN-induced antinociception, suggesting a functional interaction between the OXT and the serotoninergic system. The present study investigated in Wistar rats the potential role of spinal serotonergic mechanisms in the OXT- and PVN-induced antinociception. In long-term secondary mechanical allodynia and hyperalgesia induced by formalin or extracellular unitary recordings of the WDR cells we evaluated the role of 5-hydroxytryptamine (5-HT) effect on the OXT-induced antinociception. All drugs were given intrathecally (i.t.). OXT (1×10-5-1×10-4nmol) or 5-HT (1×10-3-1×10-1nmol) prevented the formalin-induced sensitization, an effect mimicked by PVN stimulation. Moreover, administration of OXT (1×10-5nmol) plus 5-HT (1×10-3nmol) at ineffective doses, produced antinociception. This effect was antagonized by: (i) d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH29]OVT (oxytocin receptor antagonist; 2×10-2nmol); or (ii) methiothepin (a non-specific 5-HT1/2/5/6/7 receptor antagonist; 80nmol). Similar results were obtained with PVN stimulation plus 5-HT (5×10-5nmol). In WDR cell recordings, the PVN-induced antinociception was enhanced by i.t. 5-HT and partly blocked when the spinal cord was pre-treated with methiothepin (80nmol). Taken together, these results suggest that serotonergic mechanisms at the spinal cord level are partly involved in the OXT-induced antinociception.

Hypothalamic paraventricular nucleus stimulation enhances c-Fos expression in spinal and supraspinal structures related to pain modulation.

The hypothalamic paraventricular nuclei (PVN) inhibits spinal nociception. Furthermore, projections from the PVN to other structures related to pain modulation exist, but a functional interaction has not yet been fully demonstrated. As an initial approach, we show here that PVN electric stimulation with the same parameters used to induce analgesia in rats enhances c-Fos expression not only in the dorsal horn of the spinal cord but also in the nucleus raphe magnus, locus coeruleus and the periaqueductal gray area. These results suggest that a functional interaction between these structures could occur, possibly to assure a mechanism of endogenous analgesia.

Intracisternal injection of palmitoylethanolamide inhibits the peripheral nociceptive evoked responses of dorsal horn wide dynamic range neurons.

Endogenous palmitoylethanolamide (PEA) has a key role in pain modulation. Central or peripheral PEA can reduce nociceptive behavior, but no study has yet reported a descending inhibitory effect on the neuronal nociceptive activity of Aδ- and C-fibers. This study shows that intracisternal PEA inhibits the peripheral nociceptive responses of dorsal horn wide dynamic range cells (i.e., inhibition of Aδ- and C-fibers), an effect blocked by spinal methiothepin. These results suggest that a descending analgesic mechanism mediated by the serotonergic system could be activated by central PEA.

Dorsal horn antinociception mediated by the paraventricular hypothalamic nucleus and locus coeruleous: a comparative study.

The noradrenergic descending projection originating in the locus coeruleous (LC), as well as the oxytocinergic descending projection originating in the paraventricular hypothalamic nucleus (PVN), plays a pivotal role in nociception. The mechanisms used by these two systems to modulate synaptic nociceptive transmission in the dorsal horn have been well studied independently. However, little is known about interactions between them. Here, it is shown that both PVN and LC electric stimulation inhibit A-delta, C-fiber, and postdischarge nociceptive neuronal responses in the same dorsal horn wide dynamic range neurons. Moreover, simultaneous stimulation of both the PVN and LC produces synergic inhibitory effects. In addition, LC electrolytic lesion or intrathecal administration of the alpha-2-adrenoceptor antagonist yohimbine (YOH) blocks the inhibitory effect produced by PVN stimulation in A-delta and the postdischarge, without affecting the inhibition of C-fiber responses. The results suggest that the PVN could inhibit dorsal horn nociceptive responses directly or indirectly by modulating the LC descending noradrenergic system.

Direct sensorimotor corticospinal modulation of dorsal horn neuronal C-fiber responses in the rat.

Clinically, the stimulation of motor cortical areas has been used to alleviate certain pain conditions. However, the attempts to understand the mechanisms of cortical nociceptive modulation at the spinal cord level have yielded controversial results. The objectives of the present work were to: 1) determine the effects of activating and suppressing the activity of sensorimotor cortical neurons on the nociceptive electrophysiological responses of the segmental C-fibers, and 2) evaluate the contribution of direct and indirect corticospinal projections in segmental nociceptive modulation. By means of a bipolar matrix of stimulation electrodes we mapped the stimulation of cortical areas that modulate C-fiber evoked field potentials in the dorsal horn. In addition, suppressing the cortical activity by means of cortical spreading depression, we observed that the C-fiber evoked field potentials in the dorsal horn are facilitated when cortical activity is suppressed specifically in sensorimotor cortex. Moreover, the C-fiber evoked field potentials were inhibited during spontaneous activation of cortical projecting neurons. Furthermore, after a lesion of the pyramidal tract contralateral to the spinal cord recording sites, the cortical action was suppressed. Our results show that corticospinal tract fibers arising from the sensorimotor cortex modulate directly the nociceptive C-fiber evoked responses of the dorsal horn.

Paraventricular hypothalamic oxytocinergic cells responding to noxious stimulation and projecting to the spinal dorsal horn represent a homeostatic analgesic mechanism.

The participation of the hypothalamic paraventricular nucleus (PVN) in an endogenous central mechanism of analgesia has been observed using rats in various experimental procedures including electrophysiological and behavioral tests. However, little is known about the PVN neuronal responses to noxious stimulation. The only data available indicate a c-fos increase after noxious visceral stimulations. Our electrophysiological recordings of single PVN cells showed that, out of 223 cells, 79 responded to noxious mechanical and/or thermal stimuli, and another 10 responsive cells were found in the Reuniers thalamic nucleus. These cells responded only to noxious stimuli mainly in the ipsilateral hind limb but we also observed cells responding to stimulation of both hind limbs and also the tail. Mechanical stimulation was most effective but some cells could respond to both mechanical and thermal noxious stimuli. Some of the responding PVN cells were identified by antidromic stimulation in the ipsilateral lumbar dorsal horn spinal cord. Finally, in order to document the nature of the neurotransmitter and the projection to the spinal cord of the PVN cells that responded to noxious stimulation, we used a juxtacellular approach to record and stain some neurons and found them to be oxytocinergic by immunofluorescence procedures. The PVN cells activated by noxious stimuli may suppress the peripheral incoming afferent A-delta and C fibers, completing a circuit involved in diffuse endogenous analgesia. This mechanism strongly suggests that the PVN participates in a homeostatic mechanism involved in pain and analgesia.

Paraventricular oxytocinergic hypothalamic prevention or interruption of long-term potentiation in dorsal horn nociceptive neurons: electrophysiological and behavioral evidence.

Spinal long-term potentiation (LTP) elicited by noxious stimulation enhances the responsiveness of dorsal horn nociceptive neurons to their normal input, and may represent a key mechanism of central sensitization by which acute pain could turn into a chronic pain state. This study investigated the electrophysiological and behavioral consequences of the interactions between LTP and descending oxytocinergic antinociceptive mechanisms mediated by the hypothalamic paraventricular nucleus (PVN). PVN stimulation or intrathecal oxytocin (OT) reduced or prevented the ability of spinal LTP to facilitate selectively nociceptive-evoked responses of spinal wide dynamic range (WDR) neurons recorded in anesthetized rats. In a behavioral model developed to study the effects of spinal LTP on mechanical withdrawal thresholds in freely moving rats, the long-lasting LTP-mediated mechanical hyperalgesia was transiently interrupted or prevented by either PVN stimulation or intrathecal OT. LTP mediates long-lasting pain hypersensitivity that is strongly modulated by endogenous hypothalamic oxytocinergic descending controls.

Hypothalamospinal oxytocinergic antinociception is mediated by GABAergic and opiate neurons that reduce A-delta and C fiber primary afferent excitation of spinal cord cells.

Recent results implicate a new original mechanism involving oxytocin (OT), as a mediator via descending fibers of the paraventricular hypothalamic nucleus (PVN), in antinociception and analgesia. In rats electrical stimulation of the PVN or topical application of OT selectively inhibits A-delta and C fiber responses in superficial dorsal horn neurons, and this inhibition is reversed by a selective OT antagonist. However, little is known about the mechanisms and the spinal elements participating in this phenomenon. Here we show that topical application of bicuculline blocks the effects produced by PVN electrical stimulation or OT application. PVN electrical stimulation also activates a subpopulation of neurons in lamina II. These PVN-On cells are responsible for the amplification of local GABAergic inhibition. This result reinforces the suggestion that a supraspinal descending control of pain processing uses a specific neuronal pathway in the spinal cord in order to produce antinociception involving a GABAergic interneuron. Moreover, the topical administration of naloxone or a mu-opiate receptor antagonist beta-funaltrexamine only partially blocks the inhibitory effects produced by OT application or PVN electrical stimulation. Thus, this OT mechanism only involves opiate participation to a minor extent. The OT-specific, endogenous descending pathway represents an interesting mechanism to resolve chronic pain problems in special the neuropathic pain.

Paraventricular hypothalamic nucleus stimulation modulates nociceptive responses in dorsal horn wide dynamic range neurons.

Effects of different parameters of hypothalamic paraventricular nucleus (PVN) electrical stimulation on somatic responses, in dorsal horn neurons were examined. In anaesthetized rats, single-unit extracellular recordings were made from dorsal horn lumbar segments, which receive afferent input from the toe and hind paw regions. We compared the neuronal responses evoked by electrical stimulation of the receptive field (RF) with the responses preceded by ipsilateral PVN stimulation. Only the responses corresponding to Adelta and C-fiber activation were inhibited when PVN stimulation was delivered. Fast-evoked responses corresponding to Abeta fibers were not modified. The magnitude of inhibition depends on the intensity and duration of the PVN stimulation train and gradually decreases as the time interval between the PVN and RF stimulations increases. The results indicate that PVN modulates nociceptive, but not non-nociceptive neuronal responses at the spinal cord level, and this modulation depends on the parameters of the stimulus utilized to activate PVN neurons.

Branched oxytocinergic innervations from the paraventricular hypothalamic nuclei to superficial layers in the spinal cord.

The paraventricular nucleus (PVN) of the hypothalamus is an interesting structure with diverse functions due to its different neuronal populations, neurotransmitters, and projections to other central nervous system structures. The PVN is a primary source of oxytocin (OT) in the central nervous system. In fact, a direct PVN projection to the spinal cord has been demonstrated by retrograde and anterograde tracers, and more than the 50% of this projection is oxytocinergic. This OT descending projection is proposed to be an endogenous system that controls the nociceptive information arriving at the spinal cord. However, we have no information about the specific organization of the OT descending innervations to the different spinal cord segments. The aim of the present study was to determine whether the projecting PVN neurons arrive at cervical regions and then continue to lumbar regions. That is, we sought to establish if the OT projecting cells have a topic or a diffuse projection in order to obtain histological data to support the endogenous OT diffuse mechanism of analgesia described elsewhere. With this purpose in mind we combined the OT immunohistochemistry technique with retrograde neuronal tracers in the spinal cord. We applied Diamidino Yellow (DY) for the superficial dorsal horn cervical segments and True Blue (TB) for the lumbar segments. Data were collected from eight rats with well-placed injections. We only used the animals in which the tracer deposits were confined to superficial layers I and II of the dorsal horn. A mainly ipsilateral projection was observed, but stained neurons were also observed in the contralateral PVN. A large fraction of the stained PVN cells was doubled labeled but some were single labeled. Combining the retrograde tracer techniques and the OT detection procedure, we observed triple-labeled neurons. The present results demonstrate that PVN neurons send collaterals at least to the superficial cervical and lumbar segments of the dorsal horn of the spinal cord. Moreover, some of these stained cells use OT as a neurotransmitter. These results are of great relevance since they demonstrate that the PVN plays an important role in the somatosensorial system, and they support anatomic evidence of an endogenous mechanism involved in analgesia. Finally, we also describe median raphe nucleus double-labeled cells (DY+TB) signaling diffuse descending projections for this largely studied nucleus that are involved in endogenous analgesia.

GABA-mediated oxytocinergic inhibition in dorsal horn neurons by hypothalamic paraventricular nucleus stimulation.

In anaesthetized rats, we tested whether the unit activity of dorsal horn neurons that receive nociceptive input is modulated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN). An electrophysiological mapping of dorsal horn neurons at L3-L4 let us choose cells responding to a receptive field located in the toes region of the left hindpaw. Dorsal horn neurons were classified according to their response properties to peripheral stimulation. Wide Dynamic Range (WDR) cells responding to electrical stimulation of the peripheral receptive field and presenting synaptic input of Adelta, Abeta, and C-fibers were studied. Suspected interneurons that are typically silent and lack peripheral receptive field responses were also analyzed. PVN electrical stimulation inhibits Adelta (-55.0+/-10.2%), C-fiber (-73.1+/-6.7%), and post-discharge (-75.0+/-8.9%) peripheral activation in WDR cells, and silent interneurons were activated. So, this last type of interneuron was called a PVN-ON cell. In WDR cells, the inhibition of peripheral responses caused by PVN stimulation was blocked by intrathecal administration of a specific oxytocin antagonist or bicuculline. However, PVN-ON cell activation was blocked by the same specific oxytocin antagonist, but not by bicuculline. Our results suggest that PVN stimulation inhibits nociceptive peripheral-evoked responses in WDR neurons by a descending oxytocinergic pathway mediated by GABAergic PVN-ON cells. We discuss our observation that the PVN electrical stimulation selectively inhibits Adelta and C-fiber activity without affecting Abeta fibers. We conclude that Adelta and C-fibers receive a presynaptic inhibition mediated by GABA.

Oxytocin and electrical stimulation of the paraventricular hypothalamic nucleus produce antinociceptive effects that are reversed by an oxytocin antagonist.

In recent years, oxytocin has been implicated in a wide diversity of functions. The role of oxytocin in analgesia and pain modulation represents an important new function of an endogenous system controlling sensorial information. The paraventricular (PV) nucleus of the hypothalamus is one of the most important sources of oxytocin, and it has a very well-defined projection to the spinal cord. The location of this PV spinal cord projection correlates well with oxytocin binding sites at the dorsal horn of the spinal cord. In this work, we used rats with a chronic (46 days) sciatic loose ligature, an electrical stimulating electrode, and an intrathecal cannula, which reached the L4-L5 levels of the spinal cord. We compared the oxytocin effects with electrical stimulation of the PV and observed a significant reduction of the withdrawal responses to mechanical and cold stimulation applied to the ipsilateral and contralateral hind paws. An oxytocin antagonist administered intrathecally blocked the PV effects. Naloxone was also intrathecally injected 2 min before the PV stimulation, and we also observed a significant reduction of the withdrawal responses; however, this reduction was less pronounced. Our results support the hypothesis that oxytocin is part of the descending inhibitory control mechanisms having an important antinociceptive action. We cannot exclude a minor opiate participation in the OT action.

Paraventricular hypothalamic influences on spinal nociceptive processing.

Oxytocin properties have been studied in different experimental models in order to obtain evidence for its analgesic properties. The analgesic effect of an oxytocinergic pathway descending from the hypothalamus reaching the dorsal horn of the spinal cord has been studied. In anesthetized rats, we recorded single units at the L4-L5 spinal dorsal horn level and stimulated the peripheral receptive field. The evoked responses were classified according to their latencies in A-beta, A-delta, C fibers, and postdischarge. We used these responses to evaluate the effects of electrical stimulation of the paraventricular nucleus (PV) of the hypothalamus. We observed a selective blockage of A-delta and C fibers related to the duration of the train stimulus duration. Similar effects were observed when oxytocin (OT) was applied directly on the spinal cord. The effects of OT and of PV electrical stimulation were reversed in a dose-dependent manner by application of the specific OT antagonist (OTA). These effects were observed in cells with reduced wind-up and cells displaying a clear wind-up response to peripheral stimulation. Superficial and deeper cells in the dorsal spinal cord were involved. The recorded cells were marked by pontamine blue iontophoretic injection after each cell recording, and their histological locations were specified. In order to obtain a behavioral correlation, we used rats with a loose ligature of the sciatic nerve and a chronic intrathecal catheter reaching the L4-L5 spinal cord level. We tested the hyperalgesia and allodynia of these animals using von Frey filaments and the application of acetone to the hind paws. Our results show a significant reduction in the mechanical and thermal test after the administration of 15 microl of 10(-6) M OT. Our electrophysiological, pharmacological, and behavioral results point out a clear OT antialgesic effect. The results are discussed on the basis of a previous work showing an OT blockage of glutamate activation. The paraventricular hypothalamic descending OT pathway is proposed as an interesting mechanism producing analgesia.