Risk of recurrence in patients with an unprovoked tonic-clonic seizure and generalized epileptiform discharges on EEG

OBJECTIVE

The decision to initiate treatment in patients with a first unprovoked seizure remains controversial. Studies have reported a recurrence rate ranging from 21%-50%, but most have included patients with different etiologies, electroencephalography (EEG) findings, and seizure types. This study aimed to determine the risk of recurrence in patients with a first unprovoked generalized tonic-clonic (GTC) seizure with evidence of generalized spike-wave discharges (GSWDs) on EEG and compare the efficacy of antiseizure medications (ASMs) in preventing recurrence.

METHODS

This prospective study included consecutive patients who presented with a single GTC seizure, evidence of GSWDs on EEG, and a follow-up period of at least 1 year. All patients underwent extensive evaluation, including a 3-hour sleep-deprived video-EEG recording and an epilepsy protocol brain magnetic resonance imaging (MRI). Treatment with ASMs was recommended for all patients. The decision regarding the specific ASM to be used was left to the treating physician's discretion.

RESULTS

A total of 57 patients with a median age of 19 years were included. A total of 41 patients agreed to be started on an ASM while 16 declined. Seizure recurred in 6 of 41 patients (14.6%) in the treated group compared to 11 of 16 (68.8%) in the untreated group (p = .00006). Valproate was significantly more efficacious than levetiracetam or lamotrigine (p = .04). Of the 15 patients who discontinued ASM treatment after remaining seizure-free for an average of 30 months, 6 (40%) experienced a seizure recurrence.

SIGNIFICANCE

Patients with a first unprovoked GTC seizure and evidence of GSWDs on EEG have a high risk of recurrence if left untreated. Valproate is the most efficacious ASM for preventing recurrence in this population. A sizeable proportion of patients can be successfully tapered off medication after a period of seizure freedom. This study provides valuable information for guiding treatment decisions in this patient population.

When Should a Brain MRI Be Performed in Children with New-Onset Seizures? Results of a Large Prospective Trial

BACKGROUND AND PURPOSE

There is a paucity of data regarding the incidence of structural brain lesions in children with new-onset unprovoked seizures. Our aim was to determine the frequencies and types of epileptogenic lesions detected on a dedicated epilepsy protocol MR imaging according to age group, the presence of developmental delay, and the number and types of seizures.

MATERIALS AND METHODS

Consecutive children between 6 months and 18 years of age with new-onset unprovoked seizures were included. The frequencies and types of epileptogenic lesions were determined and then stratified according to sex, age groups, the presence of developmental delay, and the number and types of seizures at presentation. Multivariate analysis was used to identify variables significantly associated with the presence of epileptogenic lesions.

RESULTS

One thousand children were included. An epileptogenic lesion was identified in 26%, with malformations of cortical development being the most common lesion (32%), followed by hypoxic-ischemic injury (20%) and vascular etiologies (16%). Univariate analysis showed a significant increase in the frequency of epileptogenic lesions with decreasing age, the presence of developmental delay, and the number and types of seizures at presentation. The presence of developmental delay and seizure type at presentation remained significant in a multivariate analysis.

CONCLUSIONS

We documented a relatively high rate of epileptogenic lesions in children with new-onset seizures, with the presence of developmental delay and specific seizure types being associated with a higher likelihood of detecting an epileptogenic lesion on neuroimaging. This study fulfills the requirements of the study design recommended by the Practice Committee of the American Academy of Neurology, and we hope that our results will assist the relevant societies and committees in formulating neuroimaging guidelines for children with new-onset seizures.

Depression and anxiety in patients from Lebanon with new onset functional seizures

OBJECTIVES

To prospectively compare the frequencies of depression and anxiety in patients with new onset functional seizures versus two age and gender-matched control groups consisting of patients with new onset epileptic seizures and normal individuals.

METHODS

Consecutive patients, 16 years and older, enrolled in a prospective study for suspected new onset epileptic seizures and diagnosed with documented functional seizures were included. We compared the depression and state and trait anxiety scores using the Beck Depression Inventory (BDI) and the State Trait Anxiety Inventory (STAI) between patients with functional seizures and the other two control groups.

RESULTS

The 33 patients with functional seizures had significantly higher depression and anxiety scores compared to those with epileptic seizures and normal controls. Twenty patients (60.6%) in the functional seizures group scored in the "depression" range compared to 5/33 (15.2%) in the epileptic seizures and 1/33 (3%) in the control groups. In the functional seizures group, 14/33 (42.4%) had scores in the "state anxiety" range compared to 6/33 (18.2%) and 2/33 (6.1%) in the epileptic seizures and normal control groups, respectively. Similarly, 15/33 (51.5%) of patients in the functional seizures group had scores in the "trait anxiety" range compared to 4/33 (12.1%) and 1/33 (3%) in the epileptic seizures and normal control groups, respectively.

CONCLUSIONS

Our results indicate that patients with new onset functional seizures frequently suffer from depression and anxiety at the time of their initial evaluation. These findings underscore the importance of screening for depression and anxiety in that patient population.

IRMPD spectroscopy and quantum chemistry calculations on mono- and bi-metallic complexes of acetylacetonate ligands with aluminum, iron, and ruthenium ions

Metal-ligand cluster ions are structurally characterized by means of gas-phase infrared multiple photon dissociation spectroscopy. The mass-selected complexes consist of one or two metal cations M³⁺ (M = Al, Fe, or Ru) and two to five anionic bidentate acetylacetonate ligands. Experimental IR spectra are compared with different density functional theory calculations, namely, PBE/TZVP, B3LYP/6-31G^*, and M06/6-31+G^**. Frequency analysis was also performed at different levels, namely, scaled static harmonic and unscaled static anharmonic, or with ab initio molecular dynamics simulations at the PBE/TZVP level. All methods lead to simulated spectra that fit rather well with experimental data, and the spectral red shifts of several main bands, in the 1200 cm^-1-1800 cm^-1 range, are sensitive to the strength of the metal-ligand interaction and to the spin state of the ion. Due to the rigidity of those complexes, first principles molecular dynamics calculations provide spectra similar to that produced by static calculations that are already able to catch the main spectral signatures using harmonic calculations at the B3LYP/6-31G^* level.

Correlation of Continuous EEG Monitoring with [O-15]H2O Positron Emission Tomography Determination of Cerebral Blood Flow during Balloon Test Occlusion of the Internal Carotid Artery

The purpose of this paper was to evaluate the utility of continuous electroencephalography (EEG) during balloon test occlusion (BTO) of the internal carotid artery (ICA). Continuous EEG monitoring and [O-15] H2O PET cerebral blood flow (CBF) studies were completed in 34 patients undergoing BTO of the ICA. CBF determinations were obtained as a baseline without carotid occlusion, and following balloon occlusion, with continuous EEG monitoring. Patients were divided into three groups based on clinical and CBF response to BTO.

Group I had no clinical signs or symptoms and had a CBF decrease less than 10 ml/100 g/min ipsilateral to the occlusion. Group II had no symptoms but CBF fell to 35 to 25 ml/100 g/min on the occluded side. Group III were clinically unable to tolerate occlusion or CBF fell to less than 25 ml/100 g/min on the occluded side.

The results of continuous 21 channel EEG monitoring were assessed at the time of the examination and retrospectively reviewed for changes in the EEG pattern indicative of ischaemia. On the basis of PET CBF, eighteen patients were classified as Group I, four as Group II, and twelve as Group III. EEG evidence of ischaemia was seen in three patients, all members of Group III. Of the three patients, only one patient had clinical signs or symptoms of ischaemia. All four patients in Group II had PET quantitated CBF levels indicating carotid sacrifice should be done with caution or following a presacrifice by-pass procedure, and nine patients in Group III with PET quantitated CBFs below eligibility for carotid sacrifice, were not identified by EEG monitoring.

Even when CBF falls below 25 ml/100 g/minute continuous EEG monitoring is insensitive to reduction in perfusion. Reliance upon EEG for detection of cerebral hypoperfusion in interventionl neuroradiological procedures will significantly underestimate ischaemic risk.

Asymptomatic brain magnetic resonance imaging abnormalities in splenectomized adults with thalassemia intermedia

BACKGROUND

A high incidence of thrombotic events in thalassemia intermedia (TI) patients led to the identification of a hypercoagulable state. Brain involvement has not been widely studied in TI, although limited reports confirm a low incidence of overt stroke and high incidence of silent brain infarcts.

PATIENTS/METHODS

This was a prospective study conducted on 30 adult, splenectomized TI patients. Patients were screened for absence of neurological signs or symptoms, and stroke-related risk factors. Patient charts were reviewed for demographics, duration since splenectomy, and any history of transfusion therapy. Blood samples were obtained for complete blood counts and serum ferritin. Direct determination of liver iron concentration (LIC) was performed by R2 magnetic resonance imaging (MRI). Brain MRI was performed on all patients, looking for ischemic lesions and/or atrophy.

RESULTS

The mean age of patients was 32.1 +/- 11 years (range, 18-54 years), with a male to female ratio of 13:17. Eighteen patients (60%) had evidence of one or more white matter lesions (WMLs) on brain MRI, all involving the subcortical white matter. Fourteen patients had evidence of multiple WMLs, with a mean of 5 +/- 10 lesions (range, 2 to > 40 lesions). The vast majority of patients (94%) had small (< 0.5 cm) to medium (0.5-1.5 cm) WMLs, with only one patient showing evidence of a large (> 1.5 cm) WML. Eleven patients (37%) had mild cerebral atrophy. On multivariate analysis only age and transfusion history were independently and significantly associated with the occurrence of zero, single or multiple WMLs.

CONCLUSION

WMLs and brain atrophy are a common finding in adult, splenectomized, TI patients. Increasing age and transfusion naivety are associated with a higher incidence and multiplicity of lesions.

Childhood stroke in a child with familial Mediterranean fever carrying several prothrombotic risk factors

Familial Mediterranean fever (FMF) was recently associated with a hypercoagulable state. However, clinically overt thrombosis remains a rare event limited to patients with other predisposing factors. We herein present a child with FMF who experienced a stroke. An extensive thrombophilia work-up revealed multiple inherited and acquired risk factors. In areas with high prevalence of prothrombotic mutations and in children who are products of consanguineous marriages, early screening for concurrent thrombotic risk factors is warranted; as this may help design an optimal management plan and prevent unfavourable outcomes.

Oxcarbazepine in painful diabetic neuropathy: results of a dose-ranging study

OBJECTIVES

To evaluate the efficacy and safety of oxcarbazepine in patients with diabetic neuropathy in a multicenter, double-blind, placebo-controlled, dose-ranging 16-week study.

METHODS

A total of 347 patients were randomized to oxcarbazepine 600 mg/day (n = 83), 1,200 mg/day (n = 87), 1,800 mg/day (n = 88), or placebo (n = 89). The primary efficacy variable was change in mean visual analog scale (VAS) score from baseline to the last week of the study.

RESULTS

No difference between any oxcarbazepine group and the placebo group was noted for the primary efficacy variable. Both the 1,200- and 1,800-mg/day groups showed a trend toward statistical significance (P = 0.101, P = 0.096, respectively). Statistically significant differences were found between the oxcarbazepine 1,200-mg/day (P = 0.038) and 1,800-mg/day (P = 0.005) groups and placebo in the overall mean weekly VAS scores for the entire double-blind treatment phase.

CONCLUSIONS

Although the primary efficacy variable did not reach statistical significance, patients taking oxcarbazepine 1,200 and 1,800 mg/day showed improvements in VAS scores compared with placebo. Oxcarbazepine may provide clinically meaningful pain relief in patients with painful diabetic neuropathy.

Safety and efficacy of two pregabalin regimens for add-on treatment of partial epilepsy

OBJECTIVE

To evaluate the efficacy, tolerability, and safety of two pregabalin regimens administered as adjunctive therapy to that of placebo in patients with medically refractory partial epilepsy.

METHODS

A multicenter, double-blind, randomized, parallel-group, placebo-controlled trial was performed. Following a prospective 8-week baseline phase, patients were randomized to 12 weeks of double-blind treatment with placebo or pregabalin 600 mg/day administered twice daily (BID) or three times daily (TID). Primary efficacy was measured as change in seizure frequency from baseline of either pregabalin regimen compared with placebo. Secondary efficacy comparisons included the proportion of patients experiencing > or =50% reduction in seizure frequency (responder rate) and median percentage change from baseline in seizure frequency. Safety/tolerability assessments included adverse events (AEs), physical and neurologic examinations, and clinical laboratory evaluation. Efficacy and safety analyses were performed on the intent-to-treat (ITT) population.

RESULTS

Pregabalin treatment resulted in seizure frequency reductions: 53% for pregabalin TID (p < or = 0.0001) and 44% for pregabalin BID (p < or = 0.0001) compared with a 1% increase for placebo. Responder rates were 49% for pregabalin TID and 43% for pregabalin BID compared with 9% for placebo (p < or = 0.001). Both pregabalin regimens were similar in efficacy and tolerability. The most common AEs were dizziness, somnolence, and ataxia.

CONCLUSIONS

Pregabalin administered at 600 mg/day is safe, generally well tolerated, and efficacious as adjunctive therapy for the treatment of patients with partial seizures, with or without secondary generalizations. This dose can be administered on a twice daily or three times daily schedule with similar efficacy and tolerability results.

Efficacy and tolerability of the new antiepileptic drugs I: treatment of new onset epilepsy: report of the Therapeutics and Technology Assessment Subcommittee and Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society

OBJECTIVE

To assess the evidence demonstrating efficacy, tolerability, and safety of seven new antiepileptic drugs (AEDs) (gabapentin, lamotrigine, topiramate, tiagabine, oxcarbazepine, levetiracetam, and zonisamide-reviewed in the order in which these agents received approval by the US Food and Drug Administration) in the treatment of children and adults with newly diagnosed partial and generalized epilepsies.

METHODS

A 23-member committee, including general neurologists, pediatric neurologists, epileptologists, and doctors in pharmacy, evaluated the available evidence based on a structured literature review including MEDLINE, Current Contents, and Cochrane library for relevant articles from 1987 until September 2002, with selected manual searches up until 2003.

RESULTS

There is evidence either from comparative or dose-controlled trials that gabapentin, lamotrigine, topiramate, and oxcarbazepine have efficacy as monotherapy in newly diagnosed adolescents and adults with either partial or mixed seizure disorders. There is also evidence that lamotrigine is effective for newly diagnosed absence seizures in children. Evidence for effectiveness of the new AEDs in newly diagnosed patients with other generalized epilepsy syndromes is lacking.

CONCLUSIONS

The results of this evidence-based assessment provide guidelines for the prescription of AEDs for patients with newly diagnosed epilepsy and identify those seizure types and syndromes where more evidence is necessary.

Efficacy and tolerability of the new antiepileptic drugs II: Treatment of refractory epilepsy: Report of the Therapeutics and Technology Assessment Subcommittee and Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society

OBJECTIVE

To assess the evidence demonstrating efficacy, tolerability, and safety of seven new antiepileptic drugs (AEDs) (gabapentin, lamotrigine, topiramate, tiagabine, oxcarbazepine, levetiracetam, and zonisamide) in the treatment of children and adults with refractory partial and generalized epilepsies.

METHODS

A 23-member committee including general neurologists, pediatric neurologists, epileptologists, and doctors in pharmacy evaluated the available evidence based on a structured literature review including MEDLINE, Current Contents, and Cochrane library for relevant articles from 1987 until March 2003.

RESULTS

All of the new AEDs were found to be appropriate for adjunctive treatment of refractory partial seizures in adults. Gabapentin can be effective for the treatment of mixed seizure disorders, and gabapentin, lamotrigine, oxcarbazepine, and topiramate for the treatment of refractory partial seizures in children. Limited evidence suggests that lamotrigine and topiramate are also effective for adjunctive treatment of idiopathic generalized epilepsy in adults and children, as well as treatment of the Lennox Gastaut syndrome.

CONCLUSIONS

The choice of AED depends upon seizure and/or syndrome type, patient age, concomitant medications, AED tolerability, safety, and efficacy. The results of this evidence-based assessment provide guidelines for the prescription of AEDs for patients with refractory epilepsy and identify those seizure types and syndromes where more evidence is necessary.

Seizure semiology and neuroimaging findings in patients with midline spikes

PURPOSE

Midline epileptiform discharges are rare compared with discharges at other scalp locations. Neuroimaging results and semiologic seizure characteristics of patients with midline spikes are not adequately described. The aim of this study was to describe the neuroimaging findings and detailed seizure semiologies in patients with midline spikes.

METHODS

We reviewed the EEG database of the University of Michigan Medical Center and identified 35 patients with midline spikes. Information about seizure types and neuroimaging results was obtained from a review of medical records. The seizures were classified according to the International League Against Epilepsy (ILAE) criteria and semiologic classification.

RESULTS

Twenty-nine (83%) patients had a history of seizures. Complex partial seizures and simple partial seizures were the most common seizure types, experienced by 66% of patients. The age at seizure onset was within the first 10 years in 90% of patients. According to the semiologic seizure classification, automotor seizures and tonic seizures were the most common seizure types. Neuroimaging studies were abnormal in 45% of patients. When focal abnormalities were detected, they were lateralized to one of the frontal lobes in all cases.

CONCLUSIONS

Our results indicate that in the majority of patients, midline spikes represent focal epileptiform activity rather than fragments of generalized discharges, and are most commonly associated with seizures of partial onset. Automotor seizures and tonic seizures are the most common semiologies. Focal radiologic abnormalities tend to be lateralized to one of the frontal lobes.

Oxcarbazepine (Trileptal) as monotherapy in patients with partial seizures

OBJECTIVE

To evaluate the efficacy and safety of oxcarbazepine (OXC) as monotherapy for patients with uncontrolled partial seizures.

METHODS

A multicenter, double-blind, randomized, parallel-group, dose-controlled monotherapy trial compared OXC at 2400 mg/day with OXC at 300 mg/day in patients with uncontrolled partial-onset seizures previously receiving carbamazepine (CBZ) monotherapy. During a 28-day open-label conversion phase, patients were tapered off CBZ and titrated to OXC 2400 mg/day. After a 56-day open-label baseline phase on OXC 2400 mg/day, patients entered a 126-day double-blind treatment phase in which they were randomized to continue OXC at 2400 mg/day or were down titrated over 6 weeks to OXC at 300 mg/day. Patients met the efficacy endpoint by completing the double-blind treatment phase or by meeting one of four predefined exit criteria. The primary efficacy variable was time to meeting one of the exit criteria. The secondary efficacy variable was the percentage of patients meeting one of the exit criteria in each of the two treatment groups.

RESULTS

Of the 143 patients enrolled, 96 were randomized in the double-blind treatment phase. Time to meeting an exit criterion was significantly in favor of the OXC 2400 mg/day group (p = 0.0001). The median time to meeting an exit criterion was 68 days for the OXC 2400 mg/day Group and 28 days for the OXC 300 mg/day Group. In addition, the percentage of patients meeting one of the exit criteria was significantly lower for the OXC 2400 mg/day Group (p = 0.0001). Overall, OXC was well tolerated with the most common adverse events consisting of fatigue, nausea, ataxia, and headache.

CONCLUSION

This trial demonstrated that OXC at 2400 mg/day is well tolerated and efficacious when administered as monotherapy in patients with uncontrolled partial onset seizures.

Safety and efficacy of oxcarbazepine: results of randomized, double-blind trials

Oxcarbazepine is approved as monotherapy and adjunctive therapy for partial seizures with and without secondarily generalized seizures in adults and as adjunctive therapy for partial-onset seizures in children aged 4-16 years. The clinical development of oxcarbazepine is different from the newer antiepileptic drugs (AEDs) in the extent and concordance of results across clinical trials. The safety and efficacy of oxcarbazepine was evaluated in adjunctive therapy trials, in comparative monotherapy trials with classic AEDs in adults and children with newly diagnosed epilepsy, in monotherapy therapeutic failure design trials in patients with refractory partial seizures, and in trigeminal neuralgia and affective disorder. The results of oxcarbazepine in treating epilepsy are discussed.

Oxcarbazepine monotherapy for partial-onset seizures: a multicenter, double-blind, clinical trial

OBJECTIVE

To evaluate the safety and efficacy of oxcarbazepine (OXC) 2,400 mg/day versus OXC 300 mg/day monotherapy in patients with medically refractory partial epilepsy.

BACKGROUND

OXC is primarily metabolized by reductase enzymes and, consequently, has a low propensity to inhibit or induce oxidative enzymes and a minimal potential for drug-drug interactions. The efficacy of OXC as monotherapy was shown in several comparative trials in patients with newly diagnosed epilepsy and in hospitalized patients undergoing evaluation for epilepsy surgery.

METHODS

A multicenter, double-blind, randomized, parallel-group trial design was chosen to assess the antiepileptic efficacy of OXC as monotherapy in a refractory epilepsy patient population. Outpatients aged 12 years or older with inadequately controlled partial seizures, with or without secondarily generalized seizures, were enrolled. Patients finished the trial by completing the double-blind phase or by meeting one of four predefined exit criteria: a twofold increase in partial seizure frequency in any 28-day period relative to baseline; a twofold increase in the highest consecutive 2-day partial seizure frequency relative to baseline; occurrence of a single generalized seizure if none occurred during the 6 months prior to randomization; or prolongation or worsening of generalized seizure duration or frequency requiring intervention. Adverse events (AEs), vital signs, and clinical laboratory tests were evaluated.

RESULTS

The percentage of patients meeting one of the exit criteria was significantly lower (p < 0.0001) for the OXC 2400 mg/day group (14/34; 41%) than the OXC 300 mg/day group (42/45; 93%). In addition, there was a significant difference in time to exit in favor of the OXC 2400 mg/day group (p = 0.0001). In the intent-to-treat analysis, 12% of patients in the OXC 2400 mg/day group were seizure-free compared with none in the 300 mg/day group. OXC was well-tolerated, with dizziness, fatigue, somnolence, and nausea being the most frequent AEs. Most of these AEs were transient and rated as mild to moderate in intensity.

CONCLUSION

OXC is safe and effective in the treatment of patients with partial epilepsy previously receiving treatment with other antiepileptic drugs. The results of this trial are consistent with previous monotherapy trials with OXC.

Monotherapy trials with gabapentin for partial epilepsy

The efficacy and safety of gabapentin as monotherapy for treatment of partial onset seizures were evaluated in three large multicenter, double-blind, parallel-group, dose-controlled trials. In the first trial, 275 outpatients with refractory partial epilepsy maintained on stable doses of one or two antiepileptic drugs (AEDs) were switched to gabapentin (GBP) monotherapy at 600 mg, 1200 mg, or 2400 mg daily. Patients were required to exit the 26-week double-blind phase of the study if they experienced worsening of seizure frequency. With respect to time to exit, there was no statistically significant difference among the three groups; only 3% of patients withdrew from the trial because of adverse events. In the second study, 82 hospitalized patients with medically refractory epilepsy were tapered off baseline AEDs and randomly assigned to GBP monotherapy at 300 mg/day or 3600 mg/day. Patients remained in the trial for a maximum of 8 days but had to exit the trial if they experienced one or more exit events. Time to exit was significantly longer in patients in the 3600-mg group (151 h) compared with those in the 300-mg group (85 h) (p = 0.0001). None of the patients withdrew from the trial because of side effects. In the third study, 292 patients with newly diagnosed partial seizures were randomized to GBP 300, 900, or 1800 mg/day or to carbamazepine (CBZ) 600 mg/day. Patients remained in the trial for up to 6 months or until they experienced an exit event. Mean time to exit was significantly longer for patients who received GBP 900 mg/day (p = 0.02) or 1800 mg/day (p = 0.04) compared with those who received 300 mg/day. The completion rate for the CBZ group (37%) was similar to that of the GBP 900-mg (39%) and 1800-mg (38%) groups. Patients receiving CBZ had a higher withdrawal rate because of adverse events compared with the GBP 900-mg and 1800-mg groups. The results of these trials provide good evidence of the efficacy and safety of GBP as monotherapy for the treatment of partial-onset seizures.

Postherpetic neuralgia: role of gabapentin and other treatment modalities

Postherpetic neuralgia (PHN) is a chronic and painful condition that may occur after a herpes zoster infection. The frequency of PHN after untreated zoster varies widely. Age is the most important risk factor for development of PHN. The condition occurs in an estimated 50% of patients older than 50 years. The pain of PHN can be severe and debilitating and is frequently associated with allodynia. Although in most patients pain remits within the first year, it may persist for a lifetime. Tricyclic antidepressants (TCAs), topical agents, opioids, and gabapentin, a structural gamma-amino butyric acid (GABA) analogue, are the only agents that have demonstrated efficacy in randomized clinical trials for treatment of both the shooting and the burning form of pain associated with PHN. TCAs are among the most commonly used classes of agents for treating PHN and are effective in a significant proportion of patients. However, various adverse events can limit treatment. These side effects tend to be more acute in the elderly, the population most likely to suffer from PHN. Topical agents have led to mild to moderate improvement in patients with PHN but are usually ineffective as monotherapy for this condition. Until recently, carbamazepine was the only antiepileptic drug evaluated for the treatment of PHN. Over the past few years, however, gabapentin has received increasing attention as a useful treatment for neuropathic pain. Gabapentin lacks significant drug-drug interactions and has a favorable safety profile, which makes it particularly useful for treatment of PHN.

Measuring the coherence of intracranial electroencephalograms

OBJECTIVE

Previous coherence studies of human intracranial electroencephalograms (EEGs) can be faulted on two methodological issues: (1) coherence estimates in a majority were formed from a very small number of independent sample spectra, and (2) the statistical significance of coherence estimates was either not reported or was poorly evaluated. Coherence estimator performance may be poor when a small number of independent sample spectra are employed, and the coupling of poor estimation and statistical testing can result in inaccuracy in the measurement of coherence. The performance characteristics of the coherence estimator and statistical testing of coherence estimates are described in this manuscript.

METHODS

The bias, variance, probability density functions, and confidence intervals of the estimate of magnitude squared coherence (MSC); and power analysis for the test of zero MSC were developed from the exact analytic form of the probability density function of the estimate of MSC for Gaussian random processes. The coherence of a single epoch of background EEG, recorded from a patient with intractable seizures, was evaluated with different parameter values to aid in the exposition of the concepts developed here.

RESULTS

The statistical characteristics of WOSA coherence estimates are a function of a single estimator parameter, the number of independent sample spectra employed in the estimation. Bias and variance are high, confidence intervals may be large, and the probability of Type II errors is high if a small number of independent sample spectra are employed. A considerable improvement in measurement accuracy is possible with careful selection of estimator parameter values.

CONCLUSIONS

Coherence measurement accuracy can be improved over previous applications by attention to estimator performance and accurate statistical testing of coherence estimates.

Value of inpatient diagnostic CCTV-EEG monitoring in the elderly

PURPOSE

To examine the outcome of inpatient diagnostic closed circuit TV-EEG (CCTV-EEG) monitoring in a consecutive series of elderly patients admitted to an adult epilepsy-monitoring unit (EMU) over a continuous 6-year period.

METHODS

Retrospective review of all admissions to a university hospital adult EMU. Those older than 60 years were identified. Patients who were monitored for status epilepticus were excluded. Data on duration of events, frequency of events, physical examination, medications, preadmission EEG, brain imaging, length of stay, and interictal and ictal EEG were obtained.

RESULTS

Of the 18 patients admitted for monitoring only, mean age was 69.5 years (range, 60-90 years). Mean length of stay was 4.3 days (range, 2-9 days). Five patients had complex partial seizures recorded. Three patients, all treated with anti-epileptic drugs (AEDs), had no spells recorded, and no additional diagnostic information was gained from the admission. The other 10 patients, eight of whom had been treated with AEDs, were symptomatic during their admission, leading to a variety of neurologic but not epileptic, psychiatric, or other medical disorders, and allowing tapering of AEDs.

CONCLUSIONS

In elderly patients with suspected epilepsy, CCTV-EEG is a very useful diagnostic tool. In this series of 18, 10 patients were diagnosed with potentially treatable medical illnesses not responsive to AEDs.

Gabapentin for the symptomatic treatment of painful neuropathy in patients with diabetes mellitus: a randomized controlled trial

CONTEXT

Pain is the most disturbing symptom of diabetic peripheral neuropathy. As many as 45% of patients with diabetes mellitus develop peripheral neuropathies.

OBJECTIVE

To evaluate the effect of gabapentin monotherapy on pain associated with diabetic peripheral neuropathy.

DESIGN

Randomized, double-blind, placebo-controlled, 8-week trial conducted between July 1996 and March 1997.

SETTING

Outpatient clinics at 20 sites.

PATIENTS

The 165 patients enrolled had a 1- to 5-year history of pain attributed to diabetic neuropathy and a minimum 40-mm pain score on the Short-Form McGill Pain Questionnaire visual analogue scale.

INTERVENTION

Gabapentin (titrated from 900 to 3600 mg/d or maximum tolerated dosage) or placebo.

MAIN OUTCOME MEASURES

The primary efficacy measure was daily pain severity as measured on an 11-point Likert scale (0, no pain; 10, worst possible pain). Secondary measures included sleep interference scores, the Short-Form McGill Pain Questionnaire scores, Patient Global Impression of Change and Clinical Global Impression of Change, the Short Form-36 Quality of Life Questionnaire scores, and the Profile of Mood States results.

RESULTS

Eighty-four patients received gabapentin and 70 (83%) completed the study; 81 received placebo and 65 (80%) completed the study. By intent-to-treat analysis, gabapentin-treated patients' mean daily pain score at the study end point (baseline, 6.4; end point, 3.9; n = 82) was significantly lower (P<.001) compared with the placebo-treated patients' end-point score (baseline, 6.5; end point, 5.1; n = 80). All secondary outcome measures of pain were significantly better in the gabapentin group than in the placebo group. Additional statistically significant differences favoring gabapentin treatment were observed in measures of quality of life (Short Form-36 Quality of Life Questionnaire and Profile of Mood States). Adverse events experienced significantly more frequently in the gabapentin group were dizziness (20 [24%] in the gabapentin group vs 4 [4.9%] in the control group; P<.001) and somnolence (19 [23%] in the gabapentin group vs 5 [6%] in the control group; P = .003). Confusion was also more frequent in the gabapentin group (7 [8%] vs 1 [1.2%]; P = .06).

CONCLUSION

Gabapentin monotherapy appears to be efficacious for the treatment of pain and sleep interference associated with diabetic peripheral neuropathy and exhibits positive effects on mood and quality of life.

Responses to photic stimulation in patients with occipital spikes

OBJECTIVE

To determine the effect of intermittent photic stimulation (IPS) and frequency of asymmetric driving responses in patients with occipital spikes.

METHODS

The amplitude of the driving response at 4 flash frequencies was measured from a referential montage in 60 patients with occipital spikes and in 60 normal EEG records from age-matched patients. Responses were classified as asymmetric if the amplitude at one occipital area was less than 50% of the amplitude at the other.

RESULTS

A measurable photic response occurred significantly less frequently in patients with occipital spikes (48%) compared to the control group (70%; Fisher's test P < 0.05). The driving response was asymmetric in 7/36 patients (37%) with unilateral spike foci versus none in the control group (Fisher's test, P < 0.001). The amplitude was suppressed ipsilateral to the focus in 5 patients, all of whom had an ipsilateral structural lesion or focal slowing. In two cases the amplitude was higher ipsilateral to the focus, neither having slowing or a structural lesion.

CONCLUSIONS

Patients with occipital spikes have an increased frequency of asymmetric driving response. An attenuated response ipsilateral to the focus seems to be related to an underlying lesion while the presence of an epileptiform focus in some cases with no slowing on EEG and normal imaging studies may lead to an accentuation of this response.

Monotherapy trials of new antiepileptic drugs

A number of clinical trials that test the efficacy and safety of the newer antiepileptic drugs (AEDs) have recently been concluded. Two dose-response trials in inpatients with refractory partial seizures and outpatients with newly diagnosed partial epilepsy established the efficacy of gabapentin as monotherapy. Lamotrigine was found to have efficacy similar to that of phenytoin and carbamazepine (CBZ) and to be better tolerated than CBZ in patients with newly diagnosed epilepsy. It was also shown to have efficacy as monotherapy in partial seizures, based on the results of an active controlled trial, and in the treatment of absence seizures, based on the results of a responder-enriched study. Topiramate as monotherapy was found to be efficacious for treatment of partial-onset seizures, based on the results of a single-center dose-response trial. A dose-response trial that tested the efficacy of tiagabine monotherapy in patients with refractory partial epilepsy was uninformative. Oxcarbazepine was found to be safe and efficacious in four comparative trials in patients with newly diagnosed epilepsy as well as in one placebo-controlled inpatient trial in patients with refractory partial seizures.

Interictal epileptiform activity in elderly patients with epilepsy

OBJECTIVE

To examine the frequency of interictal epileptiform activity (IEA) in elderly patients with epilepsy.

DESIGN AND METHODS

From a consecutive 13,905 EEGs recorded over 5 years at a university hospital EEG laboratory, 558 studies were performed on outpatients aged 60 years or more. Medical record review identified 125 patients in whom a confident clinical diagnosis of epilepsy was made by a board-certified neurologist. The EEG findings in these patients were reviewed. The effects of various variables on the likelihood of detecting IEA were calculated using Fisher's test and chi-square analysis.

RESULTS

IEA were present on the first EEG in 35% of 55 patients (mean age 65 years) with pre-existing epilepsy, and 26% of 70 patients (mean age 70 years) with seizure onset after 60 years. There were no significant differences in the frequency of IEA in patients with late onset epilepsy in the 7th or in the 8th decades of life. Most IEA were focal. Activation procedures added little additional information. Patients with more than one seizure per month were significantly more likely to have IEA (P = 0.016). There were no major differences in likelihood of IEA detection depending on the underlying cause of the seizures.

CONCLUSIONS

The frequency of IEA in elderly patients with epilepsy is substantially lower than that reported in epileptic populations as a whole. This low rate of IEA in routine EEG studies must be recognized when considering the diagnosis of an epileptic syndrome for episodic events happening in the elderly.

Conversion to high dose gabapentin monotherapy in patients with medically refractory partial epilepsy

PURPOSE

To evaluate the safety and efficacy of high dose gabapentin (GBP) monotherapy (3,000-4,800 mg/day) in patients with medically refractory partial epilepsy.

METHODS

GBP monotherapy at daily doses up to 4,800 mg was attempted in patients participating in the open-label phase of a double-blind, dose-controlled, GBP monotherapy trial. For those who achieved monotherapy, the types and severity of adverse events were assessed and the average seizure frequency per 28 days while maintained on the highest daily GBP dose was compared to the seizure frequency during the baseline phase of the double blind trial. Correlation analysis between GBP serum level, total daily dose, and percentage of seizure change from baseline was performed.

RESULTS

A total of 45 patients participated in the open-label phase of the trial and 23 (51%) were converted successfully to GBP monotherapy. In those patients, the average daily gabapentin dose was 3,900 mg and the mean length of follow-up was 252 days. Compared to baseline, there was a mean reduction of 54%, 43%, and 14% for simple partial, complex partial and secondarily generalized seizures respectively, while maintained on high-dose GBP monotherapy. A significant linear correlation between daily GBP dosage (2,400-4,800 mg) and resultant mean serum levels was found (r = 0.51; p < 0.01). There was no significant correlation between seizure frequency and total daily GBP dose or with serum levels. High-dose GBP monotherapy was well tolerated; only one patient exited the trial because of adverse events. The most common adverse event was tiredness/sleepiness and was not dose-related.

CONCLUSIONS

GBP monotherapy is well tolerated in daily doses of up to 4,800 mg and is effective in a subgroup of patients with medically refractory partial epilepsy.

Comparative psychophysical characteristics of cutaneous CO2 laser and contact heat stimulation

Psychophysical visual analog scaling can be used to reveal critical determinants of the neural processing underlying non-painful and painful heat sensations produced by radiant and contact heat stimulation. This study determined the stimulus-response (S-R) functions of cutaneous non-painful and painful heat stimuli delivered by an infra-red CO2 laser or by a contact thermode in a series of experiments in healthy volunteers. In experiments 1 (n = 12), with the rating scale anchored at pain threshold, the S-R curve for brief (60 ms) laser pulse stimulation with a beam diameter of 10 mm was a negatively accelerating function. Transformation of laser stimulus intensity (W) into temperatures (degree C) did not change the form of the S-R curve. In experiment 2 (n = 9), using the same laser stimulus parameters as in experiment 1, but without an anchored rating scale, the form of the S-R relationship did not change. In experiment 3 (n = 9), increases of the laser pulse duration up to 5 s and the beam diameter up to 18 mm produced linear S-R curves. In contrast, in experiment 4 (n = 21), the S-R curve for cutaneous contact heat stimuli applied for 5 s with an 18 mm diameter probe was best described by a positively accelerating power function with an exponent greater than 2.0. These experiments have (1) characterized the S-R functions for different parameters of infra-red laser stimulation of the skin, and (2) have shown that the form of the S-R function for innocuous and noxious heat sensation is influenced strongly by the physical conditions of heat stimulus application, including mechanical contact with the skin.

Mutual information analysis and detection of interictal morphological differences in interictal epileptiform discharges of patients with partial epilepsies

The purpose of this paper is to compare the morphological features of interictal epileptiform discharges (IED) in patients with benign epilepsy of childhood with centrotemporal spikes to IED of those with symptomatic localization related epilepsies using information theory. Three patients from each clinical group were selected. Two-second epochs centered at the peak negativity of the sharp waves were analyzed from a referential montage during stage I sleep. The epochs from the two groups were compared using parametric and information theory analysis. Information analysis determined the likelihood of correctly identifying the clinical group based on the IED. Standard parametric, morphological and spectral analyses were also performed. We found no significant difference in the morphology of the sharp wave between the two groups. The after-going slow wave contained the greatest information that separated the two groups. This result was supported by morphological and spectral differences in the after-going slow wave. Greater distinguishing information is held in the after-going slow wave than the sharp wave for the identification of clinical groups. Information analysis may assist in differentiating clinical syndromes from EEG signals.

Gabapentin monotherapy: II. A 26-week, double-blind, dose-controlled, multicenter study of conversion from polytherapy in outpatients with refractory complex partial or secondarily generalized seizures. The US Gabapentin Study Group 82/83

This study evaluated gabapentin monotherapy in 275 patients with medically refractory complex partial or secondarily generalized seizures who were taking one or two antiepileptic drugs (AEDs). Following an 8-week baseline, patients received randomized dosages of gabapentin (600, 1,200, or 2,400 mg/d) during a 26-week double-blind phase comprising 2 weeks gabapentin add-on therapy, an 8-week AED taper, and a 16-week gabapentin monotherapy period. Patients exited the study if they experienced a protocol-defined exit event. Results of outcome measures, including time to exit, completion rate, and mean time on monotherapy, showed no significant differences among dosage groups. Possible reasons for this lack of a dose-response relationship include withdrawal seizures and the limited range of gabapentin dosages studied. Overall, 20% of patients completed the study. Completion rates were higher among patients who had discontinued one AED (23%) than two AEDs (14%), and higher among patients who were not withdrawn from carbamazepine (27%) than among those who were (16%).

Pain-related laser-evoked potentials in awake monkeys: identification of components, behavioral correlates and drug effects

Cutaneous stimulation with CO2 laser pulses activates small diameter sensory afferents and evokes a pain-related potential best recorded from the vertex (Cz) of humans. We report here the first successful recording of pain-related laser evoked potentials (LEPs) from awake monkeys. Laser pulses with stimulus intensities adjusted to the lowest level giving reproducible cerebral responses were delivered to the shaved tail of three awake African green monkeys. The proximal and distal tail were stimulated to calculate the conduction velocity of the activated fibers. The effects of subcutaneous injections of morphine and cocaine on the LEPs were evaluated. The results indicate that reproducible LEPs, with a morphology similar to those obtained from humans, can be recorded from the awake monkey. The calculated conduction velocity of the activated fibers averaged 8.7 m/s, which is in the range of A delta fibers. Following subcutaneous morphine injections, the LEPs disappeared and were quickly restored to their baseline amplitude following administration of naloxone. Cocaine administered subcutaneously led to a significant attenuation of LEP amplitudes without producing behavioral sedation. These findings suggest that the LEPs recorded from monkeys represent analgesic-sensitive, nociceptive-related potentials similar to those recorded from humans.

Collet-Sicard syndrome mimicking neuralgic amyotrophy

A man with shoulder pain, wasting, and weakness had ipsilateral cranial nerve abnormalities. Electrodiagnostic studies supported a diagnosis of neuralgic amyotrophy, but we later demonstrated a spinal accessory mononeuropathy with ipsilateral hypoglossal weakness (Collet-Sicard syndrome). Magnetic resonance imaging demonstrated an inaccessible occipital condyle mass, and disseminated adenocarcinoma was subsequently diagnosed. Although cranial mononeuropathies can occur in neuralgic amyotrophy, this case illustrates the importance of identifying a focal lesion, and highlights the localizing value of electrodiagnosis.

Non-painful and painful stimulation of human skin and muscle: analysis of cerebral evoked potentials

The present study compared the cerebral processing of non-painful and painful cutaneous CO2 laser stimulation and intramuscular electrical stimulation in 11 normal subjects. The overall wave form morphology of the long-latency evoked potentials (EPs) at the central vertex (Cz) was identical and surface topographic mappings of the 21-channel recordings showed similar distributions, suggesting involvement of common neural generators. However, the EPs caused by intramuscular stimulation differed from cutaneous stimulation in several distinct ways. First, the latency of the major positive and negative components were significantly shorter with intramuscular stimulation (N 128-145 ms; P 274-298 ms) compared to cutaneous stimulation (N 235-286 ms; P 371-383 ms) (P < 0.001). Second, the peak-to-peak amplitude and root-mean-square values of intramuscular EPs recorded at Cz showed a ceiling effect in the painful range, whereas the laser EPs continued to increase in this range. Third, painful intramuscular, but not non-painful, stimulation caused a frontal activity which not was observed with cutaneous laser stimulation at any intensity. Conduction velocity measurements indicated activation of nociceptive A-delta afferents with cutaneous laser stimulation (10.2 +/- 0.2 m/s) and activation of a mixed nerve fiber population with intramuscular electrical stimulation (65.8 +/- 25.8 m/s). Differences between laser and intramuscular EPs may be due to different types and origins of activated afferent fibers. Laser EPs can be used specifically to assess cutaneous A-delta fiber function, whereas intramuscular EPs reflect the cerebral processing of a mixed afferent input from muscle tissue.

Cerebral processing of acute skin and muscle pain in humans

The human cerebral processing of noxious input from skin and muscle was compared with the use of positron emission tomography with intravenous H2(15)O to detect changes in regional cerebral blood flow (rCBF) as an indicator of neuronal activity. During each of eight scans, 11 normal subjects rated the intensity of stimuli delivered to the nondominant (left) forearm on a scale ranging from 0 to 100 with 70 as pain threshold. Cutaneous pain was produced with a high-energy CO2 laser stimulator. Muscle pain was elicited with high-intensity intramuscular electrical stimulation. The mean ratings of perceived intensity for innocuous and noxious stimulation were 32.6 +/- 4.5 (SE) and 78.4 +/- 1.7 for cutaneous stimulation and 15.4 +/- 4.2 and 73.5 +/- 1.4 for intramuscular stimulation. The pain intensity ratings and the differences between noxious and innocuous ratings were similar for cutaneous and intramuscular stimuli (P > 0.05). After stereotactic registration, statistical pixel-by-pixel summation (Z score) and volumes-of-interest (VOI) analyses of subtraction images were performed. Significant increases in rCBF to both noxious cutaneous and intramuscular stimulation were found in the contralateral secondary somatosensory cortex (SII) and inferior parietal lobule [Brodmann area (BA) 40]. Comparable levels of rCBF increase were found in the contralateral anterior insular cortex, thalamus, and ipsilateral cerebellum. Noxious cutaneous stimulation caused significant activation in the contralateral lateral prefrontal cortex (BA 10/46) and ipsilateral premotor cortex (BA 4/6). Noxious intramuscular stimulation evoked rCBF increases in the contralateral anterior cingulate cortex (BA 24) and subsignificant responses in the contralateral primary sensorimotor cortex (MI/SI) and lenticular nucleus. These activated cerebral structures may represent those recruited early in nociceptive processing because both forms of stimuli were near pain threshold. Correlation analyses showed a negative relationship between changes in rCBF for thalamus and MI/SI for cutaneous stimulation, and positive relationships between thalamus and anterior insula for both stimulus modalities. Direct statistical comparisons between innocuous cutaneous and intramuscular stimulation with the use of Z scores and VOI analyses showed no reliable differences between these two forms of noxious stimulation, indicating a substantial overlap in brain activation pattern. The comparison of noxious cutaneous and intramuscular stimulation indicated more activation in the premotor cortex, SII, and prefrontal cortex with cutaneous stimulation, but these differences did not reach statistical significance. The similar cerebral activation patterns suggest that the perceived differences between acute skin and muscle pain are mediated by differences in the intensity and temporospatial pattern of neuronal activity within similar sets of forebrain structures.

Relative value of the inion and mid-parietal locations as additional recording sites in pattern reversal visual evoked potentials

Although the P100 response of pattern reversal visual evoked potentials (PRVEPs) is most commonly recorded from the midline occipital site (MO), the response at this location can occasionally be absent or poorly defined due to anatomical variability of the visual cortex. In these cases, the American Electroencephalographic Society Evoked Potential Guidelines recommends recording from the mid-parietal (MP) and Inion electrode sites. In this study, we compared the amplitude of the P100 component recorded simultaneously from MO, MP and the Inion. PRVEPs obtained following stimulation with 30' check sizes from 155 consecutive patients (310 eyes) over a 2 year period were analyzed. At each of the 3 recording sites, the peak amplitude of P100 was calculated as N75-P100, P100-N145, and the sum of N75-P100 and P100-N145. There was a statistically significant difference between the electrode sites for all 3 methods of amplitude measurement (one-way ANOVA; P < 0.0001). For each method of measurement, there was no significant difference between P100 amplitude at MO or the Inon, but a significantly reduced amplitude at MP compared to both the MO and Inion electrode sites (post hoc Scheffe, P < 0.05). The P100 amplitude was highest at the Inion in 18% of responses, including cases where the amplitude at that site was at least twice that at MO. In no case was the amplitude highest at MP. Our results indicate that the Inion is a better recording site compared to MP when acquiring PRVEPs, is often complementary to MO, and should be the first additional site to be used when extra channels are available.

Human intramuscular and cutaneous pain: psychophysical comparisons

We used psychophysical methods to compare the central processing of nociceptive inputs from skin and muscle in ten normal humans. Both intramuscular electrical and infrared CO2 laser cutaneous stimulation showed increasing but decelerating (downward concave) stimulus-response curves and similar temporal summation characteristics. Intramuscular stimulation was rated significantly more unpleasant than cutaneous stimulation. The results are consistent with a common mode of central nociceptive processing for skin and muscle pain intensity but suggest a relatively larger activation of affective mechanisms by muscle afferents.

Safety and efficacy of divalproex sodium monotherapy in partial epilepsy: a double-blind, concentration-response design clinical trial. Depakote Monotherapy for Partial Seizures Study Group

This is the first randomized, double-blind, parallel-group, multicenter trial that evaluated the efficacy of divalproex sodium monotherapy by comparing seizure frequency in 143 patients with poorly controlled partial epilepsy randomly assigned to high (80 to 150 micrograms/mL; 555 to 1,040 mumol/L) or low (25 to 50 micrograms/mL; 175 to 345 mumol/L) plasma valproate groups. There was a statistically significant reduction from baseline in the 8-week frequency of complex partial (p = 0.001) and secondarily generalized tonic-clonic seizures (p = 0.018) for patients in the high, compared with the low, plasma valproate group. Compared with baseline, there was a 30% median reduction in complex partial seizures for patients in the high group and a 19% increase for those in the low group. The median reduction for secondarily generalized tonic-clonic seizures was 70% for patients in the high group compared with a 22% increase in the low group. Adverse events that occurred significantly more frequently in the high group included tremors, thrombocytopenia, alopecia, asthenia, diarrhea, vomiting, and anorexia. This study demonstrates the efficacy of divalproex sodium as monotherapy for the treatment of partial-onset seizures and supports its role as one of the first-line antiepileptic drug treatments for patients with partial epilepsy.

Topical capsaicin selectively attenuates heat pain and A delta fiber-mediated laser-evoked potentials

Cutaneous stimulation with CO2 laser pulses activates A delta of nociceptive afferents and evokes late cerebral potentials (LEPs), the amplitude of which correlates parametrically with the perceived magnitude estimation of laser pulses. Capsaicin is known to desensitize the nociceptive terminals of C fibers. In this double-blind, vehicle-controlled experiment, we tested the hypothesis that topical capsaicin would inactivate A delta afferents and lead to an attenuation of the LEPs. Subjects applied capsaicin cream to the dorsum of one hand and vehicle cream to the other 3 times daily for a period of 5 weeks. At weekly intervals before starting, during administration and after discontinuation of capsaicin, LEPs were recorded and psychophysical thresholds and magnitude estimation for several sensory modalities were determined. The results of this study showed that topical capsaicin significantly and reversibly decreased the magnitude estimation of suprathreshold heat pain, laser pulses and amplitude of the LEPs. There was no statistically significant difference in light touch, deep pain and mechanical pain detection thresholds between the capsaicin- and vehicle-treated hands. It indicated that topical capsaicin caused a definite functional and reversible inactivation of A delta nociceptive afferent transmission. The decline in the magnitude estimation of laser pulses concomitantly with the attenuation of LEP amplitudes supports the hypothesis that some A delta afferents mediate noxious heat in humans. These findings demonstrate the usefulness of LEP in the physiological evaluation of nociceptive pathways and its potential usefulness in objectively documenting the effect of pharmacological treatment on pain perception.

Laser-evoked cerebral potentials and sensory function in patients with central pain

Central pain syndromes (CPS) could be caused by disinhibition of spinothalamic excitability or by other central nervous system (CNS) changes caused by reduced spinothalamic function. To examine these possibilities, we studied 11 patients (ages 51-82 years) with unilateral central pain and with reproducible cerebral evoked vertex potentials in response to cutaneous stimulation of the normal side with pulses from an infra-red CO2 laser. All patients had normal tactile and kinesthetic sensation; one had slightly decreased vibratory sense bilaterally. All showed, from the unaffected (asymptomatic) side, laser evoked potentials (LEPs) with negative (N) components ranging from 208 to 280 msec peak latency (av: 240 +/- 6 SE msec) and peak amplitudes of 1-7 microV (av: 2.9 +/- 0.5 SE microV), followed, in all but 1 patient, by positive (P) potentials ranging from 288 to 370 msec peak latency (av: 319 +/- 7.7 SE msec) with peak amplitudes of 1-7 microV (2.8 +/- 0.5 SE microV). Laser stimulation of the affected (symptomatic) side in 5 patients evoked LEPs with N-P interpeak amplitudes that were within 20% of those evoked from the normal side. All but one of these patients had thresholds for warm, heat pain, and deep pain that were normal in comparison with the unaffected side. The excepted patient had the largest N-P interpeak amplitude asymmetry (18.5%) of this group. Ratings of laser pulse intensity were either symmetrical (n = 2) or increased on the affected side (n = 3) in these patients. In contrast, laser stimulation of the affected side failed to evoke either N or P potentials in 6 patients, all of whom had lateralized increased thresholds for warm, heat pain, or deep pain, or reduced ratings of laser pulse sensation. Although 1 patient had increased ratings of laser pulse sensation, the amplitude of the LEP was always reduced on the side of increased pain or heat threshold in these CPS patients (Fisher exact test: P = 0.015). These results reflect primarily a deficit in spinothalamic tract function and do not suggest excessive CNS responses to synchronous activation of cutaneous heat nociceptors in patients with CPS.

Gabapentin: pharmacokinetics, efficacy, and safety

Gabapentin is a new antiepileptic drug (AED) with an attractive pharmacokinetic profile. It is absorbed by an active and saturable transport system, and has a high volume of distribution. Gabapentin is not bound to plasma proteins, does not induce hepatic enzymes and is not metabolized. At steady state, it has a half-life of 6-8 h, and is eliminated unchanged by renal route with a plasma clearance proportional to the creatinine clearance. It is devoid of significant drug-drug interactions when administered with the established AEDs or with oral contraceptives. Gabapentin used as an add-on AED significantly reduced the frequency of partial seizures and secondarily generalized tonic-clonic seizures in three large double-blind, placebo-controlled, parallel-group clinical trails. It is well tolerated, with transient somnolence and dizziness being the most frequent adverse effects. Although the mechanism of action of gabapentin is not fully established, there is strong evidence to suggest a novel mechanism of action. Gabapentin is a unique and promising drug that could improve the quality of life of patients with epilepsy and is a welcome addition to the armamentarium of currently available AEDs for the treatment of patients with seizures of partial onset.

Octreotide reduces perception of rectal electrical stimulation by spinal afferent pathway inhibition

Octreotide reduces perception of rectal distension in normal volunteers and irritable bowel patients. To localize octreotide's site of action, perceptual and evoked potential responses to rectal electrical stimulation were tested in seven normal volunteers after double-blind octreotide (100 micrograms 2) or placebo. After octreotide, the currents needed to elicit threshold perception of square-wave impulses delivered to the rectum were 29% higher than after placebo. When electrical stimulation was delivered at constant currents 50% above threshold, rectal perception scores were significantly reduced after octreotide compared with placebo. Rectal electrical stimulation led to characteristic and reproducible cerebral evoked potentials. Octreotide had no effect on latencies, but reduced peak-to-peak amplitudes by 35% compared with placebo. Rectal electrical stimulation also led to characteristic and reproducible spinal evoked potentials. Octreotide had no effect on spinal latencies, but reduced peak-to-peak amplitudes by 51%. In conclusion, octreotide reduces perception of rectal electrical stimulation, which is associated with inhibition of cerebral and spinal evoked potential amplitude, indicating effects on spinal afferent pathways.

Asymmetric hypsarrhythmia: clinical electroencephalographic and radiological findings

Twenty-six children (16 boys and 10 girls) with hypsarrhythmia and infantile spasms (IS) were studied at the University of Michigan EEG Laboratory in a 4-year period. Six (2 boys, 4 girls), had asymmetric hypsarrhythmia with a preponderance of both slowing and epileptiform activity over one hemisphere. All 6 had the symptomatic form of IS, 4 with dysplastic conditions, 1 with porencephaly from a cerebral infarct, and 1 with hypoxicischemic encephalopathy. Five children had focal abnormalities on either physical examination or imaging studies. Four had the highest amplitude slowing and most epileptiform activity ipsilateral to the lesion, in 1, it was contralateral. Asymmetric hypsarrhythmia constituted 23% of cases with hypsarrhythmia examined at our EEG laboratory. The significant success in surgical therapy for some children with IS indicates the importance of identifying focal hemispheric abnormalities even if they are not apparent clinically. EEG may suggest focal changes not detected clinically or radiologically.

The pattern visual evoked potential. A multicenter study using standardized techniques

The peak latency of the pattern-reversal visual evoked potential is a sensitive measure of conduction delay in the optic nerve caused by demyelination. Despite its clinical utility, the pattern-reversal visual evoked potential has not previously been used in multicenter clinical trials, presumably because of difficulty in standardizing conditions between centers. To establish whether the pattern-reversal visual evoked potential could be adequately standardized for use as a measure in multicenter therapeutic trials for optic neuropathy or multiple sclerosis, stimulus and recording variables were equated at four centers and pattern-reversal visual evoked potentials were recorded from 64 normal subjects and 15 patients with resolved optic neuritis. Results showed equivalent latency and amplitude data from all centers, suggesting that stimulus and recording variables can be satisfactorily standardized for multicenter clinical trials. N70 and P100 peak latencies and N70-P100 interocular amplitude difference were sensitive measures of resolved optic neuritis.

Focal cerebral magnetic resonance changes associated with partial status epilepticus

We report 2 patients with transient abnormalities on magnetic resonance imaging (MRI) associated with partial status epilepticus (SE). A man with a 4-month history of partial seizures had complex partial SE for 9 days, with left temporal maximum on ictal EEG. Left temporal lobe T2 signal was increased on MRI during SE, but cerebral MRI was normal 9 weeks later. A woman with "cryptogenic" temporal lobe epilepsy for 16 years had complex partial SE for 1 week, with right temporal maximum on ictal EEG. T2 Signal was increased over the entire right temporal lobe, extending into the insula, without mass effect, on MRI 1 month after SE ended. Repeat MRI 1 month later showed marked decrease in volume of increased T2 intensity, without gadolinium enhancement, but with mild mass effect over the right anterioinferomesial temporal areas. A gemistocytic astrocytoma was resected. Focal cerebral MRI abnormalities consistent with cerebral edema may be due to partial SE but also may indicate underlying glioma, even in long-standing partial epilepsy. Focal structural imaging changes consistent with neoplasm should be followed to full resolution after partial SE.

Pitfalls of EEG interpretation in epilepsy

Electroencephalogram remains the single most valuable investigation in patients with known or suspected seizure disorders. Errors made in the interpretation of electroencephalogram studies are common and have significant consequences for the patient. This article presents a logical approach to the analysis of electroencephalograms, illustrating the principle pitfalls in each step of this analysis.

Correlation of evoked potential and MRI findings in Wilson's disease

We recorded brainstem auditory evoked potentials (BAEPs) and somatosensory evoked potentials to median nerve stimulation (MSEPs) within 10 days of brain MRI in 20 patients with Wilson's disease (WD). MRI was abnormal in 90% of patients, demonstrating symmetric striatum and brainstem lesions with or without thalamic lesions. MSEPs were abnormal in 65% of patients, usually showing bilaterally prolonged N/P13-N20 latencies. BAEPs were abnormal in 40%, most often with bilateral prolongation of the III-V latency. The III-V and N/P13-N20 interpeak latencies correlated significantly with the severity of MRI lesions in the caudal pons, rostral pons, and caudal midbrain. Our results indicate that subclinical sensory dysfunction is common in WD, and that auditory and somatosensory pathways are most severely affected at the brainstem level. Both the localization and severity of evoked potential abnormalities correspond closely to the morphologic changes in the pons and caudal midbrain shown by MRI.

Seizure disorders of aging: differential diagnosis and patient management

The incidence of seizures increases significantly after age 60, mainly because of an associated rise in the prevalence of such etiologies as stroke, brain tumors, and toxic-metabolic disturbances, including alcohol or drug misuse and diabetes. The differential diagnosis must rule out transient ischemic attacks, syncope, and psychiatric disorders, among other conditions. Treatment is based on the underlying cause. Seizures caused by toxic-metabolic disturbances are treated by correcting the underlying condition. Those with other etiologies require single-drug therapy with an anticonvulsant, such as phenytoin, valproic acid, or carbamazepine.