Terahertz ambipolar dual-wavelength quantum cascade laser

Terahertz frequency quantum cascade lasers (THz QCLs) are compact solid-state sources of terahertz radiation that were first demonstrated in 2002. They have a broad range of potential applications ranging from gas sensing and non-destructive testing, through to security and medical imaging, with many polycrystalline compounds having distinct fingerprint spectra in the terahertz frequency range. In this article, we demonstrate an electrically-switchable dual-wavelength THz QCL which will enable spectroscopic information to be obtained within a THz QCL-based imaging system. The device uses the same active region for both emission wavelengths: in forward bias, the laser emits at 2.3 THz; in reverse bias, it emits at 4 THz. The corresponding threshold current densities are 490 A/cm(2) and 330 A/cm(2), respectively, with maximum operating temperatures of 98K and 120 K.

Recruitment in retractor bulbi muscle during eyeblink conditioning: EMG analysis and common-drive model

To analyze properly the role of the cerebellum in classical conditioning of the eyeblink and nictitating membrane (NM) response, the control of conditioned response dynamics must be better understood. Previous studies have suggested that the control signal is linearly related to the CR as a result of recruitment within the accessory abducens motoneuron pool, which acts to linearize retractor bulbi muscle and NM response mechanics. Here we investigate possible recruitment mechanisms. Data came from simultaneous recordings of NM position and multiunit electromyographic (EMG) activity from the retractor bulbi muscle of rabbits during eyeblink conditioning, in which tone and periocular shock act as conditional and unconditional stimuli, respectively. Action potentials (spikes) were extracted and classified by amplitude. Firing rates of spikes with different amplitudes were analyzed with respect to NM response temporal profiles and total EMG spike firing rate. Four main regularities were revealed and quantified: 1) spike amplitude increased with response amplitude; 2) smaller spikes always appeared before larger spikes; 3) subsequent firing rates covaried for spikes of different amplitude, with smaller spikes always firing at higher rates than larger ones; and 4) firing-rate profiles were approximately Gaussian for all amplitudes. These regularities suggest that recruitment does take place in the retractor bulbi muscle during conditioned NM responses and that all motoneurons receive the same command signal (common-drive hypothesis). To test this hypothesis, a model of the motoneuron pool was constructed in which motoneurons had a range of intrinsic thresholds distributed exponentially, with threshold linearly related to EMG spike amplitude. Each neuron received the same input signal as required by the common-drive assumption. This simple model reproduced the main features of the data, suggesting that conditioned NM responses are controlled by a common-drive mechanism that enables simple commands to determine response topography in a linear fashion.

Generation of Bessel beams using a terahertz quantum cascade laser

We report the generation of Bessel beams using polytetrafluoroethene conical lenses and a quantum cascade laser emitting at 2.8 THz. The formation of a central beam spot that retains its size over distances exceeding the characteristic Rayleigh range is demonstrated, and the power transport properties of these beams are compared with those obtained using parabolic reflectors. These lenses could provide an attractive alternative to parabolic reflectors for terahertz imaging applications where a large depth of focus and/or efficient and controllable coupling of radiation onto a small target are desirable.

Deliberate overdose with Epsom salts

Epsom salts contains the active compound magnesium sulfate and is used most commonly as a laxative. There are potential serious toxic effects, including cardiac arrest, when the serum concentration rises above therapeutic values. We present a case of deliberate self poisoning with a large quantity of Epsom salts, resulting in a toxic serum magnesium concentration of 9.7 mmol/l (0.70-1.0 mmol/l). Clinical features included limb weakness, vomiting and confusion, with a subsequent rapid deterioration in level of consciousness and bradydysrhythmia. There was no significant response to calcium gluconate, so haemodialysis was urgently arranged. The patient made a full recovery. Hypermagnesaemia is unusual in patients with normal renal function. Although clinical severity does not always correlate with serum magnesium values, risk of cardiac arrest occurs with concentrations >6 mmol/l. Initial treatment is supportive. Dialysis should be considered when life threatening features or renal impairment are present.

Incomplete resection of focal cortical dysplasia is the main predictor of poor postsurgical outcome

BACKGROUND

Focal cortical dysplasia (FCD) is recognized as the major cause of focal intractable epilepsy in childhood. Various factors influencing postsurgical seizure outcome in pediatric patients with FCD have been reported.

OBJECTIVE

To analyze different variables in relation to seizure outcome in order to identify prognostic factors for selection of pediatric patients with FCD for epilepsy surgery.

METHODS

A cohort of 149 patients with histologically confirmed mild malformations of cortical development or FCD with at least 2 years of postoperative follow-up was retrospectively studied; 113 subjects had at least 5 years of postoperative follow-up. Twenty-eight clinical, EEG, MRI, neuropsychological, surgical, and histopathologic parameters were evaluated.

RESULTS

The only significant predictor of surgical success was completeness of surgical resection, defined as complete removal of the structural MRI lesion (if present) and the cortical region exhibiting prominent ictal and interictal abnormalities on intracranial EEG. Unfavorable surgical outcomes are mostly caused by overlap of dysplastic and eloquent cortical regions. There were nonsignificant trends toward better outcomes in patients with normal intelligence, after hemispherectomy and with FCD type II. Other factors such as age at seizure onset, duration of epilepsy, seizure frequency, associated pathologies including hippocampal sclerosis, extent of EEG and MRI abnormalities, as well as extent and localization of resections did not influence outcome. Twenty-five percent of patients changed Engel's class of seizure outcome after the second postoperative year.

CONCLUSIONS

The ability to define and fully excise the entire region of dysplastic cortex is the most powerful variable influencing outcome in pediatric patients with focal cortical dysplasia.

A prospective pilot trial of ablation of Barrett's esophagus with low-grade dysplasia using stepwise circumferential and focal ablation (HALO system)

BACKGROUND AND STUDY AIMS

Yearly surveillance endoscopy is carried out for Barrett's esophagus with low-grade dysplasia (LGD) so that progression to high-grade dysplasia and adenocarcinoma can be detected at the earliest stage. The aim of the study was to assess the long-term safety and effectiveness of circumferential ablation followed by focal ablation (HALO system) for eliminating Barrett's esophagus and LGD.

PATIENTS AND METHODS

Patients with 2 - 6 cm of Barrett's esophagus with histology demonstrating LGD on their last two sequential endoscopies over the previous 2 years and confirmed by two pathologists were enrolled in this prospective, single-center trial. Circumferential ablation was carried out at baseline and at 4 months (if residual Barrett's esophagus present). Endoscopy with 4-quadrant biopsies every 1 cm was performed at 1, 3, 6, 12, and 24 months. After 1 year, focal ablation was applied to any visible Barrett's esophagus or irregularity of the squamocolumnar junction. Patients received lansoprazole 30 mg bid. Complete responses for dysplasia (CR-dysplasia) and intestinal metaplasia (CR-IM) at 2-year follow-up, with complete response defined as "all biopsies negative for dysplasia or intestinal metaplasia" were the main outcomes.

RESULTS

Ten patients (nine men, mean age 66.9 years, range 48 - 79) with confirmed LGD (median 4.4 cm, range 3 - 6) underwent circumferential ablation with focal ablation after 1 year as necessary. At 2 years, CR-dysplasia was 100 % and CR-IM was 90 %. There were no strictures or buried intestinal metaplasia at follow-up.

CONCLUSION

A stepwise regimen of circumferential ablation followed by focal ablation appears to eradicate intestinal metaplasia (90 % CR-IM) and dysplasia (100 % CR-dysplasia) at 2-year follow-up in this trial, without stricture formation or buried intestinal metaplasia.

Evidence from retractor bulbi EMG for linearized motor control of conditioned nictitating membrane responses

Classical conditioning of nictitating membrane (NM) responses in rabbits is a robust model learning system, and experimental evidence indicates that conditioned responses (CRs) are controlled by the cerebellum. It is unknown whether cerebellar control signals deal directly with the complex nonlinearities of the plant (blink-related muscles and peripheral tissues) or whether the plant is linearized to ensure a simple relation between cerebellar neuronal firing and CR profile. To study this question, the retractor bulbi muscle EMG was recorded with implanted electrodes during NM conditioning. Pooled activity in accessory abducens motoneurons was estimated from spike trains extracted from the EMG traces, and its temporal profile was found to have an approximately Gaussian shape with peak amplitude linearly related to CR amplitude. The relation between motoneuron activity and CR profiles was accurately fitted by a first-order linear filter, with each spike input producing an exponentially decaying impulse response with time constant of order 0.1 s. Application of this first-order plant model to CR data from other laboratories suggested that, in these cases also, motoneuron activity had a Gaussian profile, with time-of-peak close to unconditioned stimulus (US) onset and SD proportional to the interval between conditioned stimulus and US onsets. These results suggest that for conditioned NM responses the cerebellum is presented with a simplified "virtual" plant that is a linearized version of the underlying nonlinear biological system. Analysis of a detailed plant model suggests that one method for linearising the plant would be appropriate recruitment of motor units.

Laterality of the Olfactory Event-Related Potential Response

In experimental practice, odors are commonly applied to only one nostril for recordings of olfactory event-related potentials (OERPs), but the lateralization aspect of the OERP response is unclear regarding both stimulated nostril and cortical topography. The purpose of the present study was to investigate whether stimulated-nostril side affects OERP amplitudes and latencies and whether these potentials indicate lateralization of brain response in healthy, right-handed, young adults. OERPs were recorded from nine electrode sites in response to monorhinal stimulation with amyl acetate in 28 participants. The results showed a general increase in amplitude from frontal to parietal electrode sites (in particular for N1/P3) and generally larger amplitudes on the left hemisphere and midline than on the right hemisphere. There was no main effect of stimulated-nostril side on amplitude. Interactions indicated that N1/P2 amplitude was larger for left- than right-nostril stimulation and larger on the left hemisphere and midline than on the right hemisphere in left-nostril stimulation. No main effect or interactions of stimulated-nostril side over latencies were found and no effects on latencies of sagittal or coronal sites. These findings suggest a general parietal, left-hemisphere predominance in response amplitude to odorous stimulation and imply that either the left or the right nostril may be sufficient for accurate assessment of OERP latency in right-handed, young adults.

Using magnetic forces to enhance non-viral gene transfer to airway epithelium in vivo

We have assessed whether magnetic forces (magnetofection) can enhance non-viral gene transfer to the airways. TransMAG(PEI), a superparamagnetic particle was coupled to Lipofectamine 2000 or cationic lipid 67 (GL67)/plasmid DNA (pDNA) liposome complexes. In vitro transfection with these formulations resulted in approximately 300- and 30-fold increase in reporter gene expression, respectively, after exposure to a magnetic field, but only at suboptimal pDNA concentrations. Because GL67 has been formulated for in vivo use, we next assessed TransMAG(PEI) in the murine nasal epithelium in vivo, and compared this to naked pDNA. At the concentrations required for in vivo experiments, precipitation of magnetic complexes was seen. After extensive optimization, addition of non-precipitated magnetic particles resulted in approximately seven- and 90-fold decrease in gene expression for naked pDNA and GL67/pDNA liposome complexes, respectively, compared to non-magnetic particles. Thus, whereas exposure to a magnetic field improved in vitro transfection efficiency, translation to the in vivo setting remains difficult.

Long Time-Constant Behavior of the Oculomotor Plant in Barbiturate-Anesthetized Primate

The mechanics of the extraocular muscles and orbital tissue (“oculomotor plant”) can be approximated by a small number of viscoelastic (Voigt) elements in series. Recent analysis of the eye's return from displacement in lightly anesthetized rhesus monkeys has suggested a four-element plant model with time constants (TCs) of ∼0.01, 0.1, 1, and 10 s. To demonstrate directly the presence of long (1,10 s) TC elements and to assess their contribution quantitatively, horizontal eye displacement was induced in Cynomolgus monkeys under deep barbiturate anesthesia that prevented interference from spontaneous eye movements. The displacement was maintained for either a prolonged (30 s) or brief (0.2 s) period before release. Return to resting position took 20–30 s after prolonged displacement but only 1–2 s after brief displacement, consistent with the presence of long TC elements that would only be substantially stretched in the former condition. Quantitative fitting of the release curves after prolonged displacement indicated that the two long TC elements contribute a substantial proportion (∼30%) of the total plant compliance. A model based on the estimated compliance values is shown to account quantitatively both for our release data and for Goldstein and Robinson's data on hysteresis of ocular motoneuron firing rates measured after centripetal saccades following prolonged eccentric fixation. Long time-constant elements in the plant thus make a substantial contribution to some types of eye movement, and their inclusion in plant models can help interpret the firing patterns of single units in the oculomotor system.

Depth-resolved holographic imaging through scattering media by use of a photorefractive polymer composite device in the near infrared

We report full-field depth-resolved holographic imaging through scattering media by use of a photorefractive polymer device in the near infrared. Real-time images through seven scattering mean free paths are acquired in a few seconds with a broadband superluminescent diode at 794 nm. A depth resolution of 15 microm and a transverse resolution of better than 42 microm are achieved. The photorefractive devices used are based on a poly(N-vinylcarbazole):2,4,7-trinitro-9-fluorenone dimalenitrile charge-transport network doped with the electro-optic chromophore 1-(2'-ethylhexyloxy)-2,5-dimethyl-4-(4"-nitrophenylazo)benzene.

Distinct clinicopathologic subtypes of cortical dysplasia of Taylor

BACKGROUND

Two pathologic subtypes based on the presence or absence of balloon cells have been described in cortical dysplasia of Taylor (CDT).

OBJECTIVE

To determine whether the pathologic subtype has any distinct clinical or MRI features that are relevant to management.

METHODS

The histopathologic, clinical, and MRI features of 34 children with CDT who underwent epilepsy surgery at Miami Children's Hospital from 1990 to 2001 were investigated.

RESULTS

Bizarre neuronal cytomegaly was the primary pathologic feature of 15 patients with the dysplasia-only subtype, and 19 cases showed additional characteristics including balloon cells and marked white matter abnormalities. Both groups presented with severe intractable epilepsy of very-early-onset, multiple daily seizures, cognitive disability, and focal neurologic deficits. The dysplasia-only subtype had higher rates of neonatal onset, hemiparesis, and severe mental retardation (p < 0.05). The MRI features of focal cortical thickening with associated cortical T2 signal change showed excellent sensitivity (94%) and reasonable specificity (73%) for the diagnosis of the balloon cell subtype. The overall surgical outcome was 59% seizure freedom at 2 years.

CONCLUSIONS

Children with cortical dysplasia of Taylor type have in common a very-early-onset, severe epilepsy with neurologic co-morbidity. Patients with the non-balloon cell pathologic subtype have a more severe phenotype. A trend toward a better outcome in the balloon cell group suggests that preoperative identification of these subtypes may impact surgical planning.

Hyperphagocytic haemocytes in Manduca sexta

We have discovered a new type of haemocyte in the larval stage of the tobacco hornworm moth Manduca sexta that has extreme phagocytic ability; each cell can engulf up to 500 bacteria. This level of phagocytosis may be unprecedented among animal cells. Although these hyperphagocytic cells (HP) only represent about 1% of the circulating haemocytes, they are responsible for sequestering the majority of the bacteria by circulating haemocytes when non-pathogenic, heat-killed Escherichia coli are injected into the haemolymph. Extreme phagocytosis by HP is not limited to Gram-negative bacteria since heat-killed Staphylococcus aureus as well as positively and negatively charged microspheres are also highly phagocytosed. Evidence is presented to show that phagocytosis by HP is involved in the early stages of nodule formation in infected insects. In addition, HP are also present in non-infected insects, characterised by their distinctive spreading morphology, which becomes impaired following hyperphagocytosis of bacteria. This is the first time that a dedicated "professional" phagocytic class of haemocyte has been reported for an invertebrate. The importance of these specialised cell types in the M. sexta immune response and their role in nodule formation is discussed.

Effect of the insect pathogenic bacterium Photorhabdus on insect phagocytes

Photorhabdus are insect pathogenic bacteria that replicate within the insect haemocoel following release from their entomopathogenic nematode symbionts. To investigate how they escape the cellular immune response we examined the effects of two strains of Photorhabdus, W14 and K122, on Manduca sexta phagocytes (haemocytes), in vitro and in vivo. Following injection of Esherichia coli into Manduca larvae, these non-pathogenic bacteria are rapidly cleared from the haemolymph and the number of free haemocytes transiently increases. In contrast, following injection of either strain of pathogenic Photorhabdus, the bacteria grow rapidly while the number of haemocytes decreases dramatically. In vitro incubation of haemocytes with either Photorhabdus supernatant reduced haemocyte viability, and the W14 supernatant caused distinct changes in the actin cytoskeleton morphology of different haemocyte cell types. In phagocytosis assays both Photorhabdus strains can inhibit their own phagocytosis whether the bacterial cells are alive or dead. Further, the supernatant of W14 also contains a factor capable of inhibiting the phagocytosis of labelled E. coli. Together these results suggest that Photorhabdus evades the cellular immune response by killing haemocytes and suppressing phagocytosis by mechanisms that differ between strains.

Eicosanoid involvement in the regulation of behavioral fever in the desert locust, Schistocerca gregaria

The desert locust Schistocerca gregaria behaviorally thermoregulates in order to try and maintain a favoured "set point" body temperature. Locusts infected with the deuteromycete fungal pathogen Metarhizium anisopliae var acridumchoose a significantly elevated temperature. This "behavioral fever" greatly delays the progress of mycosis. We have confirmed this phenomenon and shown that desert locusts also fever when infected with the bacterial pathogen Serratia marcescens. Elevation in the prefered environmental temperature occurs also upon injection with laminarin and lipopolysaccharide (microbial cell wall components). Since such treatments also stimulate the immune system it would appear that "behavioral fever" is probably a feature of the immune response. The eicosanoid biosynthesis inhibitor dexamethasone prevented laminarin invoked fever. This effect was reversable by arachidonic acid. Therefore in common with the febrile response in mammals behavioral fever in insects may be mediated locally by circulating eicosanoids.

Estimation of premotor synaptic drives to simulated abducens motoneurons for control of eye position

The firing rate of an abducens motoneuron (AbMN) is linearly related to eye position with slope K, above recruitment threshold theta. Within the AbMN population K increases as theta increases. It is possible that these properties depend on the synaptic drives generated by the major premotor inputs to AbMNs, namely position-vestibular-pause (PVP) cells and eye and head velocity (EHV) cells in the medial vestibular nucleus, and eye-position and burst-position cells in the nucleus prepositus hypoglossi (NPH). Premotor inputs to AbMNs were therefore modelled by a two-layer net, in which the output nodes represented the AbMNs (with fixed intrinsic properties) and the input nodes the three classes of premotor units ( n=20/class). Conjugate eye-position commands were used to generate the firing rates in premotor units found experimentally. The output of the net was compared with observed AbMN firing rates, and the resultant error used to adjust the magnitude and sign of the connection weights between premotor units and AbMNs. To provide additional constraints on permitted weights, the net was also trained under simulated smooth pursuit, cancellation of the vestibular-ocular reflex, and the vestibulo-ocular reflex itself (all at 0.5 Hz). Since the projections of EHV cells have not been clearly characterized, two versions of the model were trained, corresponding to different assumptions about these projections. In both versions, position-related AbMN firing rates were derived mainly from an excitatory drive from PVP cells and an inhibitory drive from NPH cells with the opposite ON direction. Variation in AbMN threshold theta and position sensitivity K depended on the strength of the drive from the NPH: the stronger the drive, the higher both K and theta. This arrangement was observed in six variants of the basic model with different parameter values, and in a simplified form (constant PVP drive and varying NPH drive) was able to generate qualitatively the observed relationship between K and theta even in the absence of input from EHV cells. It appears to be a robust mechanism for producing the experimentally observed variation in position-related firing of AbMNs, even without a contribution from their intrinsic properties, and predicts that local blocking of the inhibitory drive from cells in the NPH should lower both the position threshold and sensitivity of an individual AbMN. The model also indicates that if EHV cells have ipsilateral inhibitory projections, as has been proposed on the basis of their similarity with cells receiving input from the flocculus, then their role in eye-position control would reinforce that of cells in the NPH.

Site-specific molecular design and its relevance to pharmacogenomics and chemical biology

The emergence of the new discipline of pharmacogenomics reflects the growing convergence of chemical and genomic space. The massive information-driven growth in both computational chemistry and structural biology is leading to unprecedented opportunities in both chemical and biological design. In this paper we relate current opinion in structural biology to recent developments in computational drug design. Sequence information now permits protein structure prediction and, together with experimental protein structure determination, a complete database of ligand-binding sites and protein-protein interactions can be assembled. When aligned with site exploration and virtual screening, this information provides a foundation for structure-based pharmacogenomics. In association with chemical genomics, structure-based design will allow major new insights into a compound's biological and pharmaceutical properties.

Developmental dyslexia: the cerebellar deficit hypothesis

Surprisingly, the problems faced by many dyslexic children are by no means confined to reading and spelling. There appears to be a general impairment in the ability to perform skills automatically, an ability thought to be dependent upon the cerebellum. Specific behavioural and neuroimaging tests reviewed here indicate that dyslexia is indeed associated with cerebellar impairment in about 80% of cases. We propose that disorders of cerebellar development can in fact cause the impairments in reading and writing characteristic of dyslexia, a view consistent with the recently appreciated role of the cerebellum in language-related skills. This proposal has implications for early remedial treatment.

Audit in general practice: how much and how complete? Frequency of audit in general practice

The aim of this study was to determine the frequency of audit and the proportion completed in a group of practices. Data obtained by interviewing a member of each practice and inspecting practice records were independently coded by researchers. Practices initiated an average of 3.5 (range 1-7) audits in 2 years, of which an average of 0.9 (range 0-3) were completed. Ten of 16 completed audits were externally funded or facilitated. Few audits are completed in general practice and practices require continuing support for audit.

A simple control law generates Listing's positions in a detailed model of the extraocular muscle system

The neural commands for maintaining static Listing's positions were identified using a detailed model of extraocular muscle based on Miller and Shamaeva (Orbit 1.5 gaze mechanics simulation 1995). The commands were approximately separable, suggesting a simple control law whereby independent horizontal and vertical commands are combined to generate tertiary positions. Tests showed that this control law (i) generated Listing' s positions to reasonable accuracy over+/-30 deg, provided pulleys were represented in the model; (ii) if driven by retinal coordinates, produced errors close to the theoretical minimum for a commutative system. The proposed commands appear consistent with electrophysiological evidence.

Building relationships between academia and the pharmaceutical industry

'The climate is perfect for a proactive search for partners between industry and academia.'

Acid phosphatases in the haemolymph of the desert locust, Schistocerca gregaria, infected with the entomopathogenic fungus Metarhizium anisopliae

A comparison has been made between the effects of wounding, chemical stimulation of the immune system and fungal infection on acid phosphatase (AcP) activity in the haemolymph of the desert locust, Schistocerca gregaria. Untreated control locusts had constitutive levels of AcP. As a lysosomal enzyme, AcP may have a role in autophagy and cell turn over as well as defence. Injection of saline and beta-1,3-glucan caused significant increases in haemocyte and plasma AcP. AcP activity also increased in the haemolymph on the 3rd day after inoculation with the entomopathogenic fungus M. anisopliae var acridum. This coincided with a decline in the total haemocyte count and a marked reduction in the proportion of plasmatocytes and coagulocytes that stained positive for AcP. Therefore a priori it seemed unlikely that the extra AcP in infected insects came from the host. A fungal origin for the enzyme was suggested by the identification of AcP isoforms from haemolymph of different treatments. Control inoculated (oil only) insects had an AcP at a pI of 4.3 that was stimulated further by the injection of laminarin. Additional isoforms appeared at around 7.3-7.5 in the laminarin treatment. However, the 4.3 isoform appeared to be suppressed in the insects infected with M. anisopliae var acridum. The band intensity was more like that of the control than the laminarin-injected insects. Two new isoforms appeared later on in infection. These enzymes had pIs that corresponded to some of the AcPs produced in vitro by the fungus. The results are discussed in the light of the possible benefits of secreted fungal acid phosphatases to the pathogen.

Epilepsy surgery in children with tuberous sclerosis complex: presurgical evaluation and outcome

PURPOSE

Children with tuberous sclerosis complex (TSC) benefit from excisional surgery if seizures can be localized to a single tuber. We evaluated the role of noninvasive studies to localize the epileptogenic tuber/region (ET/R) and the outcome of focal resection.

METHODS

We identified 21 children with TSC, ages 3 months to 15 years (mean 4.8 years). All had video-(electroencephalogram) EEG and magnetic resonance imaging (MRI) scans, and 18 also had ictal single photon emission-computed tomography (SPECT) studies. An ET/R was localized in 17 patients. Thirteen patients underwent resection guided by intraoperative electrocorticography (n = 7) or subdural monitoring (n = 6).

RESULTS

Interictal EEG revealed a principal spike focus (PSF) that corresponded to the ET/R in 14 children. In seven, PSFs occurred in rhythmic runs. PSFs were not observed remote from the ET/R. Focal polymorphic slowing and attenuation occurred in the region of the PSF in 11 patients. Sixteen patients demonstrated an ictal focus corresponding to the ET/R. Ictal SPECT revealed focal hyperperfusion correlating with the ET/R in 10 patients. Although the MRIs in all children revealed multiple tubers, the ET/R corresponded to a large discrete tuber in 8 patients and a calcified tuber in 13 patients. Patchy calcified tubers were also seen elsewhere in six patients. At a mean follow-up of 26 months, 9 of the 13 children who underwent surgery were seizure-free, one had greater than 75% reduction in seizures, two were unchanged, and one was lost to follow-up. New seizures developed in one child from a contralateral tuber.

CONCLUSIONS

Surgical resection of an ET/R alleviates seizures in most children with TSC and intractable epilepsy. The scalp EEG and MRI help define the ET/R and improve case selection when ictal SPECT is nonlocalizing.

Predictors of outcome in pediatric epilepsy surgery

OBJECTIVE

To determine the correlation between pre- and perioperative variables on the outcome of children undergoing focal resections for medically intractable partial epilepsy.

METHODS

Retrospective analysis of pre- and perioperative variables in a cohort of 75 patients younger than 12 years of age who underwent excisional surgery and had at least 1 year of follow-up. Outcome, measured by postoperative seizure frequency, was analyzed as a function of age at seizure onset, duration of epilepsy, presence of cognitive impairment, lobe of seizure origin, presence of a lesion, histopathology, and completeness of resection. Completeness of resection was defined on the basis of excising both the entire structural lesion if present and the region revealing prominent interictal and ictal abnormalities on intracranial EEG.

RESULTS

Seventy-seven percent of patients had good outcomes (class 1 or 2), and 59% were seizure-free. Lesional status, site of resection, and pathologic diagnoses were not significant predictors of outcome except for in multilobar resection, for which overall outcome was relatively poor (44% class 3 or 4; 22% seizure-free). Completeness of resection was the only significant predictor of good outcome (p < 0.001), with 92% of patients who underwent complete resection of the epileptogenic zone achieving good outcome compared with 50% of patients who had incomplete resections.

CONCLUSION

In this series of pediatric patients, complete resection of the lesion and the electrographically abnormal region was the main determinant of outcome after focal resections. Except for multilobar resections, other factors examined in this study did not significantly influence postoperative seizure prognosis and should not influence candidate selection for the surgical process.

[Epilepsy treatment by vagal stimulation]

INTRODUCTION

Vagal nerve stimulation is the latest therapeutic modality for the treatment of epilepsy. It consists of a lead implanted in the left vagal nerve which is connected to a subcutaneous stimulator implanted in the left axillary or pectorial region.

DEVELOPMENT

The stimulator is programmed to intermittently stimulate the vagal nerve throughout the day and a magnet also allows the patient to control the stimulation from the outside. This treatment has been used in patients with intractable partial seizures who are not candidates for epilepsy surgery. The results reported have varied but in general the procedure appears promising with at least 50% of the implanted having over 50% improvement in their seizure frequency and many having complete control without significant side effects.

CONCLUSION

Further review of the results are still needed to fully determine the true value of this treatment and to identify the subgroups of patients which will benefit the most.

Association of abnormal cerebellar activation with motor learning difficulties in dyslexic adults

BACKGROUND

In addition to their impairments in literacy-related skills, dyslexic children show characteristic difficulties in phonological skill, motor skill, and balance. There is behavioural and biochemical evidence that these difficulties may be attributable to mild cerebellar dysfunction. We wanted to find out whether there was abnormal brain activation when dyslexic adults undertook tasks known normally to involve cerebellar activation.

METHODS

Brain activation was monitored by positron emission tomography in matched groups of six dyslexic adults and six control adults as they carried out either a prelearned sequence or learned a novel sequence of finger movements.

FINDINGS

Brain activation was significantly lower (p<0.01) for the dyslexic adults than for the controls in the right cerebellar cortex and the left cingulate gyrus when executing the prelearned sequence, and in the right cerebellar cortex when learning the new sequence.

INTERPRETATION

The results provided direct evidence that, for this group of dyslexic adults, the behavioural signs of cerebellar abnormality reflect underlying abnormalities in cerebellar activation.

Bellini duct (collecting duct) carcinoma of the kidney

Carcinoma of the collecting ducts, or Bellini carcinoma, is a rare renal tumour and, unlike most renal cell carcinomas, it derives from distal tubules. It displays highly aggressive behaviour and has a poor prognosis. In this study, the authors present three cases which they observed over the past three years.