Presurgical evaluation of epilepsy patients.

Epilepsy surgery has been established as an effective treatment in pharmacoresistant focal epilepsies. Most candidates for epilepsy surgery are patients with partial epilepsy syndromes refractory to medical treatment. The curative surgery procedure is resection of the epileptogenic zone; therefore, precise detection of the site responsible for seizure generation is necessary. Modern structural and functional imaging techniques have made presurgical evaluation less invasive and available for a higher number of patients. Video electroencephalography (EEG) monitoring, high-resolution structural and functional imaging techniques are used widely for presurgical evaluation. When noninvasive evaluation is not sufficient for the detection of the epileptogenic zone, invasive EEG monitoring and intracarotid amobarbital test are used. A classical example of a surgically curable epilepsy syndrome is mesial temporal lobe epilepsy with about 70-80% of patients becoming free of seizures after surgery. Results in extratemporal epilepsies are also satisfactory. Despite worldwide expansion during the recent decade, epilepsy surgery remains underutilized. Better understanding of advances in presurgical evaluation should reduce fears of epilepsy surgery and help to select patients who could achieve complete seizure control or significant amelioration after surgery.

Intravenous lacosamide as replacement for oral lacosamide in patients with partial-onset seizures.

PURPOSE: This multicenter, double-blind, double-dummy, randomized, inpatient trial evaluated the safety, tolerability, and pharmacokinetics of intravenous lacosamide as replacement for oral lacosamide in patients with partial-onset seizures. METHODS: Patients were enrolled from an ongoing open-label extension trial of oral lacosamide and randomized (2:1) to either intravenous lacosamide and oral placebo or intravenous placebo and oral lacosamide. During the 2-day inpatient treatment period, patients received twice-daily doses of lacosamide equivalent to their current daily dose of oral lacosamide. The first 30 patients enrolled received infusions with 60-min durations and the next 30 received infusions with 30-min durations. RESULTS: Of 60 patients randomized, 59 completed the trial. Treatment-emergent adverse events (AEs) were reported by 16 patients and included dizziness, headache, back pain, somnolence, and injection site pain. The tolerability profile of intravenous lacosamide was consistent with that of oral lacosamide. All AEs were considered mild or moderate in intensity, and no serious AEs or AEs leading to withdrawal were reported. CONCLUSIONS: Intravenous lacosamide, administered as 60- or 30-min twice-daily infusions, showed a similar safety and tolerability profile to oral lacosamide when used as replacement therapy. Results from this trial support further investigation of intravenous lacosamide at shorter infusion durations.

A clinical study of corticospinal and peripheral conductions to proximal lower limb muscles.

OBJECTIVE: To investigate the clinical utility of the newly developed "quadriceps combined technique" (QCT), which provides a global evaluation of the central and peripheral conduction to the proximal muscles of lower limbs, in a variety of central and peripheral neurological disorders. METHODS: Using surface recordings from the vastus medialis of the quadriceps muscle, we analyzed amplitudes and latencies of M response, patellar T reflex and motor evoked potentials (MEPs) after transcranial magnetic stimulation. We studied 180 patients with disorders impairing proximal strength of one or both lower limbs and compared them with 100 controls reported previously. RESULTS: The best parameters to detect central motor disorders were the central motor conduction time, MEP/M amplitude, T/MEP amplitude and latency ratios, whereas peripheral motor conduction time (PMCT) was best to assess peripheral disorders. The best parameter to identify proximal peripheral disorder was PMCTprox, whereas for distal peripheral disorders M amplitude and T/MEP amplitude ratio were most discriminative. CONCLUSIONS: We report a simple, rapidly performed and well-tolerated method that improves proximal lower limbs evaluation, helps distinguishing pathologic from physiological brisk reflexes and provides clues for etiologic diagnosis. SIGNIFICANCE: The QCT is a sensitive and specific tool to investigate central and peripheral neurological disorders.

Electrophysiological evaluation of motor pathways to proximal lower limb muscles: a combined method and reference values.

OBJECTIVE: In contrast with their important functional and clinical role, motor pathways to proximal muscles of lower limbs are rarely investigated in clinical neurophysiology. We describe a method to evaluate central and peripheral pathways to these muscles and report reference values. METHODS: Recording of both quadriceps was performed in 100 subjects. We analyzed the maximal M response after electrical stimulation of the femoral nerve, the patellar T reflex and the motor evoked potential (MEP) after transcranial magnetic stimulation. We defined the central motor conduction time as the difference between the MEP latency and the peripheral motor conduction time, estimated as the half of the T latency minus 0.5ms. RESULTS: The mean MEP latency is 20.6ms (SD 1.99ms), central motor conduction time 10.1ms (SD 1.29ms), MEP/M amplitude ratio 60.0% (SD 15.75%). Normal limits according to height and age are provided for each parameter and for interside asymmetry. CONCLUSIONS: This method to investigate the central and peripheral motor pathways supplying the L2-L4 myotomes is simple, painless and rapidly performed. The T reflex provides additional information on the proximal sensory pathways. SIGNIFICANCE: This method will be useful in many clinical conditions.

Electrophysiology of small peripheral nerve fibers in man. A study using the cutaneous silent period.

UNLABELLED: Methods for assessing small peripheral nerve fiber function objectively are limited. The cutaneous silent period (CuSP), a transient suppression of electromyographic voluntary activity that follows painful stimuli, could serve as an objective functional measure of the A delta fibers. OBJECTIVES: To establish normal values of CuSP, to compare these values to those in the literature and to discuss the yield of the CuSP in pathological conditions. MATERIAL AND METHODS: We investigated the CuSP of the upper and lower limbs of 40 normal subjects. RESULTS: We observed that the spinal circuitry mediating the CuSP is mainly unilateral and restricted to one limb, and that CuSP latency decreases and duration increases with increasing stimulus intensity, then CuSP stabilizes with strong stimuli. In an additional study, we observed that painful cutaneous stimuli are either inhibitory, causing a pause in an ongoing contraction (CuSP), or excitatory, inducing a contraction of a muscle at rest (RIII). Inhibition and excitation have similar timings. CONCLUSION: The method for studying the CuSP is simple and well tolerated; it is useful to study A delta fibers in peripheral neuropathies and the central circuitry of this cutaneous nociceptive response in conditions affecting the spinal cord. Comparison of CuSP studies suggests the need for a standardization of the method.

Cutaneous silent period in carpal tunnel syndrome.

The cutaneous silent period (CuSP), a transient suppression of electromyographic activity that follows painful stimuli, allows an indirect study of the small-diameter A-delta fibers. To assess the function of these fibers in peripheral nerve disorders, we compared the CuSP of 40 controls to that of 40 patients with carpal tunnel syndrome (CTS) and one patient with a traumatic transection of the median nerve. Patients with CTS were divided into three severity groups, based on electrophysiological data. In CTS, digit 2 evoked CuSP onset latency was increased in all groups, and CuSP duration from abductor digiti minimi was reduced in all groups. In our series, although some parameters of the CuSP were altered, only transection of the nerve abolished it. A-delta fibers are robust, probably due to their less vulnerable small diameter. This characteristic may be useful to study various conditions and essential for patients to retain some sensation within the median nerve territory.

Transcranial magnetic stimulation in clinical practice.

Transcranial magnetic stimulation allows a non-invasive and painless stimulation of the human brain and cranial nerves. The method is in use since 1985. Transcranial magnetic stimulation can use single stimuli, pairs of stimuli separated by different intervals (to the same or to several brain areas), or trains of repetitive stimuli at various frequencies. Single stimuli give rise to motor evoked potentials that have clinical use and serve diagnostic and prognostic purposes. Repetitive transcranial magnetic stimulation can modify excitability of cerebral cortex. Repetitive transcranial magnetic stimulation has opened a new field of investigation of the neural circuitry, and is developing into a therapeutic tool. This general review considers basic principles of transcranial magnetic stimulation, discusses methodological aspects and techniques, and analyses their utility in clinical practice.