Alessandro Stefani

Deep Brain Stimulation for Parkinson Disease: An Expert Consensus and Review of Key Issues

OBJECTIVE To provide recommendations to patients, physicians, and other health care providers on several issues involving deep brain stimulation (DBS) for Parkinson disease (PD). DATA SOURCES AND STUDY SELECTION An international consortium of experts organized, reviewed the literature, and attended the workshop. Topics were introduced at the workshop, followed by group discussion. DATA EXTRACTION AND SYNTHESIS A draft of a consensus statement was presented and further edited after plenary debate. The final statements were agreed on by all members. CONCLUSIONS (1) Patients with PD without significant active cognitive or psychiatric problems who have medically intractable motor fluctuations, intractable tremor, or intolerance of medication adverse effects are good candidates for DBS. (2) Deep brain stimulation surgery is best performed by an experienced neurosurgeon with expertise in stereotactic neurosurgery who is working as part of a interprofessional team. (3) Surgical complication rates are extremely variable, with infection being the most commonly reported complication of DBS. (4) Deep brain stimulation programming is best accomplished by a highly trained clinician and can take 3 to 6 months to obtain optimal results. (5) Deep brain stimulation improves levodopa-responsive symptoms, dyskinesia, and tremor; benefits seem to be long-lasting in many motor domains. (6) Subthalamic nuclei DBS may be complicated by increased depression, apathy, impulsivity, worsened verbal fluency, and executive dysfunction in a subset of patients. (7) Both globus pallidus pars interna and subthalamic nuclei DBS have been shown to be effective in addressing the motor symptoms of PD. (8) Ablative therapy is still an effective alternative and should be considered in a select group of appropriate patients.

Magnetic resonance imaging markers of Parkinson's disease nigrostriatal signature

One objective of modern neuroimaging is to identify markers that can aid in diagnosis, disease progression monitoring and long-term drug impact analysis. In this study, Parkinson-associated physiopathological modifications were characterized in six subcortical structures by simultaneously measuring quantitative magnetic resonance parameters sensitive to complementary tissue characteristics (i.e. volume atrophy, iron deposition and microstructural damage). Thirty patients with Parkinsons disease and 22 control subjects underwent 3-T magnetic resonance imaging with T₂*-weighted, whole-brain T₁-weighted and diffusion tensor imaging scans. The mean R₂* value, mean diffusivity and fractional anisotropy in the pallidum, putamen, caudate nucleus, thalamus, substantia nigra and red nucleus were compared between patients with Parkinsons disease and control subjects. Comparisons were also performed using voxel-based analysis of R₂*, mean diffusivity and fractional anisotropy maps to determine which subregion of the basal ganglia showed the greater difference for each parameter. Averages of each subregion were then used in a logistic regression analysis. Compared with control subjects, patients with Parkinsons disease displayed significantly higher R₂* values in the substantia nigra, lower fractional anisotropy values in the substantia nigra and thalamus, and higher mean diffusivity values in the thalamus. Voxel-based analyses confirmed these results and, in addition, showed a significant difference in the mean diffusivity in the striatum. The combination of three markers was sufficient to obtain a 95% global accuracy (area under the receiver operating characteristic curve) for discriminating patients with Parkinsons disease from controls. The markers comprising discriminating combinations were R₂* in the substantia nigra, fractional anisotropy in the substantia nigra and mean diffusivity in the putamen or caudate nucleus. Remarkably, the predictive markers involved the nigrostriatal structures that characterize Parkinsons physiopathology. Furthermore, highly discriminating combinations included markers from three different magnetic resonance parameters (R₂*, mean diffusivity and fractional anisotropy). These findings demonstrate that multimodal magnetic resonance imaging of subcortical grey matter structures is useful for the evaluation of Parkinsons disease and, possibly, of other subcortical pathologies.

Gabapentin inhibits calcium currents in isolated rat brain neurons

Gabapentin (1(aminomethyl) cyclohexane acetic acid; GBP) is a recently developed anticonvulsant, for which the mechanism of action remains quite elusive. Besides its possible interaction with glutamate synthesis and/or GABA release, in cerebral membranes gabapentin has been shown to bind directly to the alpha2delta subunit of the calcium channel. Therefore, we have tested the possibility that gabapentin affects high threshold calcium currents in central neurons. Calcium currents were recorded in whole-cell patch-clamp mode in neurons isolated from neocortex, striatum and external globus pallidus of the adult rat brain. A large inhibition of calcium currents by gabapentin was observed in pyramidal neocortical cells (up to 34%). Significantly, the gabapentin-mediated inhibition of calcium currents saturated at particularly low concentrations (around 10 microM), at least in neocortical neurons (IC50 about 4 microM). A less significant inhibition was seen in medium spiny neurons isolated from striatum (-12.4%) and in large globus pallidus cells (-10.4%). In all these areas, however, the GBP-induced block was fast and largely voltage-independent. Dihydropyridines (nimodipine, nifedipine) prevented the gabapentin response. Omega-conotoxin GVIA and omega-conotoxin MVIIC, known to interfere with the currents driven by alpha1b and alpha1a calcium channels, did not prevent but partially reduced the response. These findings imply that voltage-gated calcium channels, predominately the L-type channel, are a direct target of gabapentin and may support its use in different clinical conditions, in which intracellular calcium accumulation plays a central role in neuronal excitability and the development of cellular damage.

Lamotrigine inhibits Ca2+ currents in cortical neurons : functional implications

In pyramidal cortical cells, high-voltage-activated Ca2+ currents affect seizure propagation and the release of excitatory amino acids at the corticostriatal axon terminals. The new antiepileptic drug lamotrigine (Lamictal) produced a large and dose-dependent inhibition of high-voltage-activated Ca2+ currents (IC50 = 12.3 microM) in rat cortical neurons. This action was not blocked by the dihydropyridine receptor antagonist nifedipine; instead, the response was blocked by the concomitant application of the N-type Ca2+ channel blocker, omega-conotoxin GVIA (1-3 microM) and the P-type Ca2+ channel blocker, omega-agatoxin-IVA (20-100 nM). These findings demonstrate that lamotrigine, at therapeutic doses, is capable of modulating the Ca2+ conductances involved in excitatory amino acid release in the corticostriatal pathway, partially explaining lamotrigine usefulness in the therapy of epilepsy as well as in the treatment of excitatory amino acid-induced neurotoxicity.

Dermoscopy in general dermatology

Dermoscopy improves the diagnostic accuracy in the clinical evaluation of pigmented skin lesions, but it is also useful for the assessment of vascular structures that are not visible to the naked eye. As a consequence, dermoscopy has been employed more and more for the differential diagnosis of nonpigmented skin disorders, including tumors but also inflammatory and infectious diseases. This article provides a review of the dermoscopic features seen in various nonpigmented tumoral and nontumoral skin lesions as well as the dermoscopic criteria used for monitoring skin reactions to various treatments.

Differential inhibition by riluzole, lamotrigine, and phenytoin of sodium and calcium currents in cortical neurons: implications for neuroprotective strategies.

Among the several classes of drugs currently studied as neuroprotective agents, glutamate release blockers have been indicated as being rather effective. In particular, lamotrigine and riluzole have shown promise in the treatment of either acutely developing cellular damages (stroke, posttraumatic lesions) or slowly progressing neurodegenerative diseases as amyotrophic lateral sclerosis. These drugs are supposed to interfere with the release of endogenous glutamate in situ, yet the mechanisms underlying this effect are not fully defined. One possibility is that lamotrigine and riluzole act by inhibiting voltage-dependent inward conductances active in the soma and/or in the axon terminal region. Therefore, we have investigated the effects of lamotrigine and riluzole on the voltage-gated sodium and calcium currents of acutely isolated neurons from the adult rat neocortex. In addition, since phenytoin is a well-known blocker of the sodium channel, we have compared lamotrigine and riluzole responses with the peak current inhibition produced by phenytoin in the same cells. Lamotrigine produced a large reduction of the high-voltage-activated calcium currents and a smaller; use-dependent inhibition of the sodium conductance. Riluzole inhibited significantly the sodium current at surprisingly low concentrations (nanomolar range) and by up to 80% at saturating doses (1-10 microM). Furthermore, riluzole inhibited both high- and low-voltage-activated calcium currents in neocortical neurons isolated from adult and young animals. By contrast, phenytoin caused only a slight reduction of high-voltage-activated calcium currents even at supratherapeutic doses (by < 12% at 10 microM). Taken together, the different pharmacological profiles of the tested agents might indicate that glutamate release blockers do not represent a homogenous class of drugs. Conversely, our findings could support their selective utilization in different disease status.

Three-point checklist of dermoscopy

Background: Dermoscopy used by experts has been demonstrated to improve the diagnostic accuracy for melanoma. However, little is known about the diagnostic validity of dermoscopy when used by nonexperts. Objective: To evaluate the diagnostic performance of nonexperts using a new 3-point checklist based on a simplified dermoscopic pattern analysis. Methods: Clinical and dermoscopic images of 231 clinically equivocal and histopathologically proven pigmented skin lesions were examined by 6 nonexperts and 1 expert in dermoscopy. For each lesion the nonexperts assessed 3 dermoscopic criteria (asymmetry, atypical network and blue-white structures) constituting the 3-point method. In addition, all examiners made an overall diagnosis by using standard pattern analysis of dermoscopy. Results: Asymmetry, atypical network and blue-white structures were shown to be reproducible dermoscopic criteria, with a kappa value ranging from 0.52 to 0.55. When making the overall diagnosis, the expert had 89.6% sensitivity for malignant lesions (tested on 68 melanomas and 9 pigmented basal cell carcinomas), compared to 69.7% sensitivity achieved by the nonexperts. Remarkably, the sensitivity of the nonexperts using the 3-point checklist reached 96.3%. The specificity of the expert using overall diagnosis was 94.2% compared to 82.8 and 32.8% achieved by the nonexperts using overall diagnosis and 3-point checklist, respectively. Conclusion: The 3-point checklist is a valid and reproducible dermoscopic algorithm with high sensitivity for the diagnosis of melanoma in the hands of non-experts. Thus it may be applied as a screening procedure for the early detection of melanoma.

Voltage-activated calcium channels : Targets of antiepileptic drug therapy?

Summary: Voltage‐gated calcium currents play important roles in controlling neuronal excitability. They also contribute to the epileptogenic discharge, including seizure maintenance and propagation. In the past decade, selective calcium channel blockers have been synthesized, aiding in the analysis of calcium charinel subtypes by patch‐clamp recordings. It is still a matter of debate whether whether any of the currently available antiepileptic drugs (AEDs) inhibit these conductances as part of their mechanism of action. We tested oxcarbazepine, lamotrigine, and felbamate and found that they consistently inhibited voltage‐activated calcium currents in cortical and striatal neurons at clinically relevant concentrations. Low micro‐molar concentrations of GP 47779 (the active metabolite of oxcarbazepine) and lamotrigine reduced calcium conductances involved in the regulation of transmitter release. In contrast, felbamate blocked nifedipine‐sensitive conductances at concentrations significantly lower than those required to modify N‐methyl‐d‐aspartate (NMDA) responses or sodium currents. Aside from contributing to AED efficacy, this mechanism of action may have profound implications for preventing fast‐developing cellular damage related to ischemic and traumatic brain injuries. Moreover, the effects of AEDs on voltage‐gated calcium signals may lead to new therapeutic strategies for the treatment of neurodegenerative disorders.

Entodermoscopy: A New Tool for Diagnosing Skin Infections and Infestations

Background: There is upcoming evidence that dermoscopy facilitates the in vivo diagnosis of skin infections and infestations. As such, dermoscopy connects the research fields of dermatologists and entomologists, opening a new research field of ‘entodermoscopy’. Objective: To provide an overview on the current applications of entodermoscopy. Methods: Systematic review of the English- and German-language literature by searches of Medline, Medscape and abstracts of the 1st World Congress of the International Dermoscopy Society. Results: Dermoscopic patterns have been described for viral warts, molluscum contagiosum, scabies, pediculosis, tinea nigra, tungiasis, cutaneous larva migrans, ticks and reactions to spider leg spines. Besides the diagnostic role of dermoscopy, there is increasing evidence that it can also assist in the monitoring of treatment efficacy for some of these conditions. Conclusion: Although most of the current available literature is based on single observations and small case studies rather than controlled trials, an increasing interest in this field can be observed.

Subthalamic stimulation activates internal pallidus: Evidence from cGMP microdialysis in PD patients

Parkinsons disease patients benefit from deep brain stimulation (DBS) in subthalamic nucleus (STN), but the basis for this effect is still disputed. In this intraoperative microdialysis study, we found elevated cGMP extracellular concentrations in the internal segment of the globus pallidus, despite negligible changes in glutamate levels, during a clinically effective STN‐DBS. This supports the view that a clinically beneficial effect of STN‐DBS is paralleled by an augmentation (and not an inactivation) of the STN output onto the GPi. Ann Neurol 2005;57:448–452