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At least 1,315 records · Page 73Linked to original sources
PubMed2005

Radiosurgery for basal ganglia, internal capsule, and thalamus arteriovenous malformation: clinical outcome.

OBJECTIVE: Radiosurgery is accepted as the first option for treating deep arteriovenous malformations (AVMs), although the clinical outcome in this subgroup of brain AVMs is not well studied. The objective of this study is to review our experience with radiosurgical treatment for these AVMs. METHODS: Between October 1989 and December 2000, 45 patients with deep AVMs (including basal ganglia, internal capsule, and thalamus) underwent stereotactic radiosurgery. Three patients were lost to follow-up and therefore were excluded from this study. Patient characteristics and outcomes were collected and analyzed. The obliteration prediction index and the radiosurgery-based AVM score were calculated and tested. RESULTS: Forty-two patients were followed up for a median of 39 months (range, 25-90 mo; mean, 45.8 mo). The median maximum AVM diameter during the radiosurgery was 1.8 cm (range, 0.9-4.0 cm; mean, 2.07 cm), and the median AVM volume was 2.8 cm(3) (range, 0.2-18.3 cm(3); mean, 4.74 cm(3)). The mean marginal dose was 16.2 Gy (median, 15 Gy), and the median maximum dose was 22.4 Gy (range, 16.6-30 Gy). The AVM cure rate after the first radiosurgical treatment, using angiography- and magnetic resonance imaging-confirmed obliteration, was 61.9%. The predicted obliteration using the obliteration prediction index was 60%. Eight patients developed radiation-induced complications (19%). The deficit was transient in three patients (7.1%) and permanent in five patients (11.9%). The risk of postradiosurgical hemorrhage in this cohort was 9.5% for the first year, 4.7% for the second year, and 0% thereafter. Excellent outcome (obliteration plus no new deficit) was achieved in 70% of the patients in the group with radiosurgery-based AVM score less than 1.5 compared with 40.9% in the group with radiosurgery-based AVM score greater than 1.5% (P = 0.059). CONCLUSION: Radiosurgery for deep AVMs has a satisfactory obliteration rate and acceptable morbidity, considering the risk of hemorrhage without treatment and the risk of morbidity associated with other treatment modalities.

Adolescent↗
PubMed1980

Excitatory effects of dihydrocapsaicin on nociceptive neurons in the medial thalamus.

Effects of capsaicin and dihydrocapsaicin, which are pungent substances contained in Capsicum annuum L., were studied in 32 gallamine triethiodide immobilized cats. Single units were recorded from the medial thalamus using stainless steel microelectrodes. Of the 56 neurons recorded, 28 were responsive to both noxious (pinching) and non-noxious (hair and/or tapping) stimuli, while 16 were activated only by non-noxious stimuli. The remaining 12 neurons did not respond to any natural stimulus. Somatic receptive fields of nociceptive and non-nociceptive neurons were found to be widely distributed over the whole body. Twenty-six of 28 nociceptive neurons were activated by an intra-arterial administration of bradykinin, capsaicin and dihydrocapsaicin. Fourteen of 16 non-nociceptive neurons were not activated by these substances. The mean latency and duration of bradykinin were 8.7 and 12.5 sec, those of capsaicin were 1.2 and 6.1 sec and those of dihydrocapsaicin were 1.3 and 5.0 sec, respectively. The increase of firing frequency produced by capsaicin and dihydrocapsaicin was inhibited by morphine and this inhibition was antagonized by naloxone. However, the activity of medial thalamic neurons with non-noxious stimuli was not affected by these drugs. These results suggest that the pain-conducting fibers were selectively activated by capsaicinoids as well as by bradykinin.

Action Potentials↗
PubMed2003

Ganglioglioma in the thalamus of a puppy.

A solitary brain mass of a 4-month-old miniature dachshund showing seizure-like neurological signs was examined histopathologically. At necropsy a white tumor mass, replacing the thalamus, approximately 1.5 cm in diameter, was found. There was cystic space filled with yellowish pale fluid in the central area of the tumor mass. Histopathological examination revealed that the mass consisted of irregularly arranged well-differentiated neuronal and glial cells, and multifocal mineral deposits. The neuronal cells had a large clear nucleus and various amount of Nissl substances in the cytoplasm. Some neural cells were bi-nucleated. Neither mitotic figures nor proliferating cell nuclear antigen (PCNA)-positive nuclei was found in the neuronal cells. Immunostaining for glial fibrillary acidic protein (GFAP) revealed diffuse proliferation of GFAP-positive glial cells and their processes, while these glial cells did not show apparent cellular atypism, mitotic activity, or PCNA-immunoreactivity. Accordingly, the present tumor was diagnosed as ganglioglioma, and hamartomatous histogenesis might be possible.

Animals↗
PubMed2005

Auditory fear conditioning and long-term potentiation in the lateral amygdala require ERK/MAP kinase signaling in the auditory thalamus: a role for presynaptic plasticity in the fear system.

In the present study, we examined the role of the auditory thalamus [medial division of the medial geniculate nucleus and the adjacent posterior intralaminar nucleus (MGm/PIN)] in auditory pavlovian fear conditioning using pharmacological manipulation of intracellular signaling pathways. In the first experiment, rats were given intrathalamic infusions of the MEK (mitogen-activated protein kinase-kinase) inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto) butadiene (U0126) before fear conditioning. Findings revealed that long-term memory (assessed at 24 h) was impaired, whereas short-term memory (assessed at 1-3 h) of fear conditioning was intact. In the second experiment, rats received immediate posttraining intrathalamic infusion of U0126, the mRNA synthesis inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), or infusion of the protein synthesis inhibitor anisomycin. Posttraining infusion of either U0126 or DRB significantly impaired long-term retention of fear conditioning, whereas infusion of anisomycin had no effect. In the final experiment, rats received intrathalamic infusion of U0126 before long-term potentiation (LTP)-inducing stimulation of thalamic inputs to the lateral nucleus of the amygdala (LA). Findings revealed that thalamic infusion of U0126 impaired LTP in the LA. Together, these results suggest the possibility that MGm/PIN cells that project to the LA contribute to memory formation via ERK (extracellular signal-regulated kinase)-mediated transcription, but that they do so by promoting protein synthesis-dependent plasticity locally in the LA.

Acoustic Stimulation↗
PubMed2005

Excitatory effects of thyrotropin-releasing hormone in the thalamus.

The activity of the thalamus is state dependent. During slow-wave sleep, rhythmic burst firing is prominent, whereas during waking or rapid eye movement sleep, tonic, single-spike activity dominates. These state-dependent changes result from the actions of modulatory neurotransmitters. In the present study, we investigated the functional and cellular effects of the neuropeptide thyrotropin-releasing hormone (TRH) on the spontaneously active ferret geniculate slice. This peptide and its receptors are prominently expressed in the thalamic network, yet the role of thalamic TRH remains obscure. Bath application of TRH resulted in a transient cessation of both spindle waves and the epileptiform slow oscillation induced by application of bicuculline. With intracellular recordings, TRH application to the GABAergic neurons of the perigeniculate (PGN) or thalamocortical cells in the lateral geniculate nucleus resulted in depolarization and increased membrane resistance. In perigeniculate neurons, this effect reversed near the reversal potential for K+, suggesting that it is mediated by a decrease in K+ conductance. In thalamocortical cells, the TRH-induced depolarization was of sufficient amplitude to block the generation of rebound Ca2+ spikes, whereas the even larger direct depolarization of PGN neurons transformed these cells from the burst to tonic, single-spike mode of action potential generation. Furthermore, application of TRH prominently enhanced the afterdepolarization that follows rebound Ca2+ spikes, suggesting that this transmitter may also enhance Ca2+-activated nonspecific currents. These data suggest a novel role for TRH in the brain as an intrinsic regulator of thalamocortical network activity and provide a potential mechanism for the wake-promoting and anti-epileptic effects of this peptide.

Action Potentials↗
PubMed2007

Cortical modulation of spatial and angular tuning maps in the rat thalamus.

The massive feedback projections from cortex to the thalamus modulate sensory information transmission in many ways. We investigated the role of corticothalamic feedback projections on the directional selectivity (angular tuning) of neurons in the rat ventral posterior medial (VPM) nucleus to stimulation of their principal whisker. The angular tuning properties of single VPM neurons were compared before and after epochs of electrical stimulation of layer VI feedback neurons in the ipsilateral cortex under urethane anesthesia. Microstimulation of layer VI in "matched" (homologous) barrel columns sharpens the angular tuning curves of single VPM neurons that are tuned to the same direction as the stimulation site in the cortex. Further, microstimulation rotates the angular preference of VPM neurons initially tuned to a different direction toward the direction that cortical neurons prefer. Stimulation in "mismatched" (nonhomologous) barrel columns suppresses responses without consistent effects on angular tuning. We conclude that the primary sensory cortex exerts a significant influence on both spatial and angular tuning maps in the relay nuclei that project to it. The results suggest that the tuning properties of VPM cells in the behaving animal are continually modified to optimize perception of the most salient incoming messages.

Adaptation, Physiological↗
PubMed2004

Corticofugal gating of auditory information in the thalamus: an in vivo intracellular recording study.

In the present study, we investigated the auditory responses of the medial geniculate (MGB) neurons, through in vivo intracellular recordings of anesthetized guinea pigs, while the auditory cortex was electrically activated. Of the 63 neurons that received corticofugal modulation of the membrane potential, 30 received potentiation and 33 received hyperpolarization. The corticofugal potentiation of the membrane potential (amplitude, mean +/- SD, 8.6 +/- 5.5 mV; duration, 125.5 +/- 75.4 msec) facilitated the auditory responses and spontaneous firing of the MGB neurons. The hyperpolarization of -11.3 +/- 4.9 mV in amplitude and 210.0 +/- 210.1 msec in duration suppressed the auditory responses and spontaneous firing of the MGB neurons. Four of the five neurons that were histologically confirmed to be located in the lemniscal MGB received corticofugal facilitatory modulation, and all of the four neurons that were confirmed to be located in the non-lemniscal MGB received corticofugal inhibitory modulation. The present intracellular recording provides novel results on how the corticofugal projection gates the sensory information in the thalamus: via the spatially selective depolarization of lemniscal MGB neurons and hyperpolarization of non-lemniscal MGB neurons. It is speculated that the systematic selectivity of facilitation and inhibition over the lemniscal and non-lemniscal MGB is related to the attention shift within the auditory modality and across the sensory modalities.

Acoustic Stimulation↗
PubMed1986

Ascending fibers from the gigantocellular nucleus to the centromedian nucleus of the thalamus in cats.

Centrum medianum (CM) afferent pathways, which are involved in pain sensation, were analyzed using physiological techniques. Thirty-four neurons in the gigantocellular nucleus (nucleus gigantocellularis medullae oblongatae, GC) in cats were recorded intracellularly. Of these, 5 (15%) did not respond to electrical stimulation applied to any of the 4 limbs. Twenty-nine (85%) showed spike potentials that were superimposed on excitatory post-synaptic potentials (EPSPs) with an amplitude of 7.2 mV (n = 101) and a duration of 6.8 ms. The latencies from contra- and ipsilateral forelimb, contra- and ipsilateral hindlimb to the GC were 9.3 (n = 25), 7.2 (n = 23), 12.9 (n = 28), and 10.9 ms (n = 25), respectively. Of these responding neurons, 19 (66%) responded to stimuli to all 4 limbs, 7 (24%) to 3 limbs, 1 (3%) to 2 limbs, and 2 (7%) to 1 limb. These afferent neurons in the GC showed spike potentials without EPSPs after stimulation of the CM in the thalamus. Extracellular activities of 37 CM neurons were also tested. Of these, 4 neurons responded to GC stimulation with a short latency of 1.6 ms. Another 33 responded with a long latency of 6.7, and 11 of them were able to follow GC stimulation of over 200 Hz with a fixed long latency; 22 responded with varying long latencies but were not able to follow stimuli over 15 Hz. Three-quarters of the CM neurons received ipsilateral inputs from the GC, and the other contralateral inputs. Three CM neurons responded to stimulation of the GC in quasi-intracellular records. These findings suggest that some ascending fibers from the GC terminate on CM neurons and play a role in pain sensation.

Animals↗
PubMed1993

Magnetic resonance angiography of arteriovenous malformation in the thalamus.

A comparative study of magnetic resonance angiography and conventional angiography of arteriovenous malformation in the thalamus showed that both methods clearly visualized the feeding arteries: perforating branches of the posterior cerebral artery, posterior choroidal artery and lenticulostriate artery. Draining veins such as the internal cerebral vein were also demonstrated well.

Adolescent↗
PubMedDate not supplied

Vestibular evoked potentials in thalamus and basal ganglia of the squirrel monkey (Saimiri sciureus).

In anesthetized squirrel monkeys vestibular representation in the thalamus and basal ganglia was determined by field potential recording using peripheral electrical vestibular nerve stimulation. Vestibular thalamic regions were investigated for cortical connections. Two relatively large thalamic areas, nucleus ventralis posterolateralis, VPL and the posterior nuclear group (Po) received vestibular inputs with short latencies suggesting direct connections with the vestibular nuclei. Antidromic stimulation of the area 3 a vestibular field did not produce responses in any of the vestibular thalamic fields. The vestibular regions in VPL and Po can be antidromically invaded from SI and the anterior parietal lobe respectively. In the striatum vestibular fields were found in the suprathalamic portion of the nucleus caudatus and dorsomedially in the putamen.

Animals↗
PubMed1980

Contextual organization of unitary information processes in the cortex by the thalamus and basal ganglia and the central control of attention.

Short-term memory experiments suggest the presence within the neocortex of a basic information unit (a data structure plus an algorithm) able to store and return a relatively fixed number of items. Units of a similar format may be involved in all cortical motor and sensory activities of an integrated nature, and may interact to yield higher-order-information units dealing with interrelationships among groups of units. If individual units can reference other similar units, a hierarchical organization of computing is possible that could form the basis for contextual information processing and the hierarchical structuring characteristic of many specifically human forms of behavior. Vertical columns of neurons in the cortex may provide the physical basis for information units of the type suggested. The selection and organizing of activity in groups of columns may be regulated by a neural loop involving the basal ganglia and the thalamus, which would thus implement the central adjustment of attention.

Animals↗
PubMed1980

Conative regulation of cortical activity by the reticular formation, hypothalamus, and thalamus.

Evolution of neural regions suggests the requirement for a common format for information units exchanged among regions. Short-term memory experiments suggest a format of six or seven items. A similar number of configurations of primary cerebral interactions is proposed, associated with arousal, sleep, approach, withdrawal, perseveration, alert scanning, and commanded by the reticular formation. A comparable number of basic states (feeding, mating, grooming, shelter-seeking, fighting, etc.) is proposed as operating within these configurations, under regulation by the hypothalamus. Conative variables from this region are transformed into patterns of regulation for local cortical populations by the thalamus. Elaboration of these configurations and states by higher structures leads to new forms of cortical activity only loosely coupled to brain stem systems.

Adaptation, Physiological↗
PubMed1983

Electrophysiological evidence of concurrent dorsal raphe input to caudate, septum, habenula, thalamus hippocampus, cerebellum and olfactory bulb.

Field potentials evoked by electrical stimulation of the dorsal raphe nucleus (DR) were recorded in eight forebrain structures in the rat. The areas were chosen chiefly for their anatomical connections to the DR and included the olfactory bulb (OB), caudate nucleus (CN), lateral septum (Spt), lateral habenula (Hb), parafascicularis (PF), ventral thalamus (VT), hippocampus-CA1 (Hipp), and cerebellum (CB). DR stimulation evoked an initial biphasic positive-negative wave form at similar latencies in each of the eight structures. A later positive-negative-positive wave was evoked in only six structures: CN, Spt, Hb, PF, VT, and Hipp. The amplitudes and latencies of the peaks of the later wave forms varied among structures. A depth profile recording procedure created by moving the DR stimulating electrode showed that the responses in the remote structures occurred only when the stimulating electrode was located in the DR. Bursting the DR at 20 Hz for 5-20 min caused a decrease in all components of the response. The evoked potential amplitude returned to baseline levels 5-30 min after cessation of stimulation. The results indicates that the dorsal raphe has a concurrent input to many areas of the brain receiving 5HT afferents and that DR stimulation can modulate the neuronal activity in these regions.

Animals↗
PubMed1994

Teaching image-guided stereotactic methodology and functional neuroanatomy of the thalamus and pallidum: a simple ex vivo technique.

A simple and cheap model that enables on site, ex vivo, but very practical, learning of frame-based image-guided stereotactic technique and methodology, and the functional anatomy of the pallidum and thalamus is described. Using a cadaver skull, a specially prepared, formalin-fixed cadaver brain, and a modified stereotactic probe application of a stereotactic frame to the cranium, fiducial point acquisition, target point acquisition, computation of both arc and probe depth settings, and verification of target point accuracy can all be practiced. If diencephalic targets are selected for targeting with ball bearings then section of the cadaver brains, and study of a human thalamic stereotactic atlas provides an excellent and clinically relevant method of learning functionally important thalamic and pallidal anatomy. The method and techniques are described for CT imaging using the Brown-Roberts-Wells frame, but they are equally applicable to other frame types.

Brain Mapping↗
PubMed1995

Infiltrative astrocytomas of the thalamus.

Clinical characteristics and outcome in 57 patients with infiltrative thalamic astrocytomas were analyzed retrospectively. The median patient age was 22 years (range 1 to 69 years). Fourteen patients had no surgery, 37 had biopsy, and six had subtotal resection. The histological diagnosis was astrocytoma in 14 patients, anaplastic astrocytoma in 25, and glioblastoma multiforme in two; two specimens were nondiagnostic. The initial treatment was conventional radiation therapy (RT) in 20 patients (one also received interstitial brachytherapy), RT followed by chemotherapy in 18, hyperfractionated RT in 17 (one also received chemotherapy), and chemotherapy alone in two. The median time to tumor progression was 47 weeks (range 5 to 388 weeks); median survival was 73 weeks (range 11 to 502 weeks). Actuarial 1-, 2-, 3-, and 5-year survival rates were 67%, 35%, 24%, and 20%, respectively. Tumor progression was usually treated with chemotherapy. The assessed treatment failure was within 2 months after RT in 12 patients in whom the findings of the neurological and radiological examinations did not correspond. This assessment showed false-negative diagnosis of radiation-induced changes in five patients (42%); false-positive diagnosis of tumor progression could not be ascertained. In univariate Cox proportional-hazards analysis, histological diagnosis of astrocytoma, age under 18 years, and open biopsy were prognostically favorable features; in multivariate analysis, only open biopsy was favorable. Infiltrative astrocytomas of the thalamus carry a dismal prognosis, regardless of the type of treatment. Hyperfractionated RT does not increase toxicity but its benefit over conventional RT remains unproven.

Adolescent↗
PubMed2004

Radiosurgery for arteriovenous malformations of the basal ganglia, thalamus, and brainstem.

OBJECT: Although stereotactic radiosurgery is frequently performed for arteriovenous malformations (AVMs) in deep locations, outcomes after radiosurgery for these patients have not been well studied. The goal of this paper was to study these outcomes. METHODS: Between 1990 and 2000, 56 patients underwent radiosurgery for AVMs located in the basal ganglia (10 patients), thalamus (30 patients), or brainstem (16 patients). The median age of these patients was 34.2 years. Thirty-five patients (62%) had experienced previous bleeding. The AVMs were classified Grade IIIB in 62% of patients and Grade IV in 38% according to the modified Spetzler-Martin Scale; the median radiosurgery-based AVM score was 1.83. The median volume of the lesion was 3.8 cm3 and the median radiation dose delivered to its margin was 18 Gy. The median duration of follow-up review after radiosurgery was 45 months (range 3-121 months). In seven patients (12%) hemorrhage occurred at a median of 12 months after radiosurgery; five patients (9%) died and two recovered without any deficit. Permanent radiation-related complications occurred in six (12%) of 51 patients (excluding the five patients who died of hemorrhage) after one procedure and in three (18%) of 17 patients after repeated radiosurgery. Obliteration of the AVM was noted in 24 patients (43%; obliteration was confirmed by angiography in 18 patients and by magnetic resonance [MR] imaging in six patients) after a single procedure and in 32 patients (57%; confirmed by angiography in 25 patients and by MR imaging in seven patients) after one or more procedures. Excellent outcomes (obliteration of the lesion without any new deficit) were obtained in 39% of patients after one radiosurgical procedure and in 48% after one or more procedures. Twelve (67%) of 18 patients with AVM scores lower than 1.5 had excellent outcomes compared with 15 (39%) of 38 patients with AVM scores greater than 1.5 (p = 0.053). CONCLUSIONS: Less than half of the patients with deeply located AVMs were cured of the future risk of hemorrhage without new neurological deficits. This experience emphasizes the difficulty in treating patients with deeply located AVMs; the majority of whom are also poor candidates for resection or embolization.

Adult↗
PubMed2005

Gamma knife surgery for refractory postherpetic trigeminal neuralgia: targeting in one session both the retrogasserian trigeminal nerve and the centromedian nucleus of the thalamus.

OBJECT: The authors tested the hypothesis that two targets are needed to treat postherpetic trigeminal neuralgia (TN): one in the trigeminal nerve for the direct sharp pain and one in the thalamus for the diffuse burning pain. METHODS: Three patients with refractory postherpetic TN were treated with gamma knife surgery (GKS) through a novel two-target approach. In a single treatment session, both the trigeminal nerve and centromedian nucleus were targeted. First, the trigeminal nerve, ipsilateral to the facial pain, was treated with 60 to 80 Gy. Second, the centromedian nucleus was localized using standard coordinates and by comparing magnetic resonance images with a stereotactic atlas. A single dose of 120 to 140 Gy was delivered to the target point with a single 4-mm isocenter. Patients were followed clinically and with neuroimaging studies. Pain relief was scored as excellent (75-100%), good (50-75%), poor (25-50%); or none (0-25%). Follow up ranged from 6 to 53 months. There were no GKS-related complications. Two patients died of unrelated medical illnesses but had good or excellent pain relief until death. One patient continues to survive with 44 months follow up and no decrease in pain intensity, but with a decreased area of pain. CONCLUSIONS: Combined GKS of the centromedian nucleus and trigeminal nerve in a single treatment session is feasible and safe, and the effect was promising. A larger study is required to confirm and expand these results.

Aged↗