Spinal cord monitoring.

Spinal cord surgery carries the risk of spinal cord or nerve root injury. Neurophysiologic monitoring decreases risk of injury by continuous assessment of spinal cord and nerve root function throughout surgery. Techniques include somatosensory evoked potentials (SEPs), transcranial electrical motor evoked potentials (MEPs), and electromyography (EMG). Baseline neurophysiologic data are obtained prior to incision. Real-time signal changes are identified in time to correct compromised neural function. Such monitoring improves postoperative neurologic functional outcomes. Challenges in neurophysiologic intraoperative monitoring (NIOM) include effects of anesthetics, neuromuscular blockade, hypotension, hypothermia, and preexisting neurological conditions, e.g., neuropathy or myelopathy. Technical factors causing poor quality data must be overcome in the electrically noisy operating room environment. Experienced monitoring teams understand tactics to obtain quality recordings and consider confounding variables before raising alarms when change occurs. Once an alert is raised, surgeons and anesthesiologists respond with a variety of actions, such as raising blood pressure or adjusting retractors. In experienced hands, NIOM significantly reduces postoperative neurological deficits, e.g., 60% reduction in risk of paraplegia and paraparesis. A technologist in the operating room sets up the NIOM procedure. An experienced clinical neurophysiologist supervises the case, either in the operating room or remotely on-line continuously in real time.

Trigeminal nerve stimulation in major depressive disorder: acute outcomes in an open pilot study.

Most patients with major depressive disorder (MDD) do not recover with initial pharmacotherapy, and many pursue combination treatments. Combining a medication with neuromodulation offers an alternative to purely pharmacologic strategies. In prior open and double-blind controlled trials for drug-resistant epilepsy, adjunctive external trigeminal nerve stimulation (eTNS) was found to be safe and well tolerated, to significantly reduce seizures, and to be associated with an improvement in depressive symptoms. Here, we present a comprehensive description of the first open pilot investigation in MDD. In this 8-week trial, eleven adults with unipolar MDD received nightly stimulation (V(1) branch). All entered with moderate to severe symptom levels despite at least two antidepressant medication trials in this episode. All the eleven adults completed the acute trial, without serious adverse events. Symptoms of depression improved significantly, whether assessed with clinician- or self-rated scales (all p < 0.01; effect sizes d 1.0-1.8), as did quality of life (p < 0.02). Four of the 11 achieved remission. These improvements from nightly adjunctive eTNS in treatment-resistant depression merit replication under double-blind conditions.

Trigeminal nerve stimulation: seminal animal and human studies for epilepsy and depression.

The unique ability to stimulate bilaterally, extracranially, and non-invasively may represent a significant advantage to invasive neuromodulation therapies. In humans thus far the technique has been applied noninvasively, and is termed external trigeminal nerve stimulation (eTNSTM).

Trigeminal nerve stimulation in major depressive disorder: first proof of concept in an open pilot trial.

Modulation of brain activity via trigeminal nerve stimulation is an emerging therapy in drug-resistant epilepsy. This cranial nerve also projects to structures implicated in depression (such as the nucleus tractus solitarius and locus coeruleus). We examined the effects of external trigeminal nerve stimulation in major depressive disorder as an adjunct to pharmacotherapy. Five adults (mean age 49.6, SD 10.9, three females and two males) participated in an 8-week open-label outpatient trial; all had persistent symptoms despite adequate pharmacotherapy, with a mean score on the 28-item Hamilton Depression Rating Scale of 25.4 (SD=3.9) at entry. Nightly stimulation over the V(1) branch was well tolerated. Both the clinician-rated 28-item Hamilton Depression Rating Scale (P=0.006) and the self-rated Beck Depression Inventory (P=0.0004) detected significant symptomatic improvement. This novel neuromodulation approach may have use as an adjunct to pharmacotherapy in major depressive disorder. Additional larger trials are needed to delineate efficacy and tolerability with greater reliability.

Safety and tolerability of repetitive transcranial magnetic stimulation in patients with epilepsy: a review of the literature.

Repetitive transcranial magnetic stimulation (rTMS) is emerging as a new therapeutic tool in epilepsy, where it can be used to suppress seizures or treat comorbid conditions such as mood disorder. However, as rTMS carries a risk of inducing seizures among other adverse events, its safety and tolerability in the population with epilepsy warrant distinct consideration, as this group is especially seizure-prone. Accordingly, we performed a review of the literature to estimate the risk of seizures and other adverse events associated with rTMS in patients with epilepsy. We performed an English-language literature search, and reviewed all studies published from January 1990 to February 2007 in which patients with epilepsy were treated with rTMS, and complemented the literature search with personal correspondence with authors when necessary. We identified 30 publications that described patients with epilepsy who underwent rTMS, and noted total number of relevant subjects, medication usage, incidence of adverse events, and rTMS parameters including stimulus frequency, number of stimuli, train duration, intertrain interval, coil type, and stimulation sites. The data were analyzed for adverse events related to rTMS. Crude per-subject risk, as well as per-subject mean risk weighted by sample size and risk per 1000 stimuli weighted by number of stimuli in each study, were computed for seizures and for other adverse events. Adverse events or lack thereof was reported in 26 studies (n=280 subjects). Adverse events attributed to rTMS were generally mild and occurred in 17.1% of subjects. Headache was most common, occurring in 9.6%. The most serious adverse event was seizure during treatment, which occurred in four patients (1.4% crude per-subject risk). All but one case were the patients' typical seizures with respect to duration and semiology, and were associated with low-frequency rTMS. A single case of an atypical seizure appearing to arise from the region of stimulation during high-frequency rTMS is reported. No rTMS-related episodes of status epilepticus were reported. We cautiously conclude that the risk of seizure in patients with epilepsy undergoing rTMS is small, and the risk of other mild adverse events is comparable to that seen when rTMS is used to treat other diseases. Status epilepticus or life-threatening seizures have not been reported in patients undergoing rTMS treatment. rTMS thus appears to be nearly as safe in patients with epilepsy as in nonepileptic individuals, and warrants further investigation as a therapy in this population.

Low frequency electrical stimulation through subdural electrodes in a case of refractory status epilepticus.

OBJECTIVE: We delivered low frequency stimulation through subdural electrodes to suppress seizures in a case of refractory status epilepticus (RSE). METHODS: A 26-year-old female developed RSE after several days of febrile illness. Seizure control required continuous infusion of two anesthetics plus high doses of 2-4 enteral antiepileptic drugs. After 3 months of RSE, subdural strips were placed to determine surgical candidacy. Five independent ictal onset zones were identified. Because she was a poor candidate for epilepsy surgery and had a poor prognosis, the implanted subdural electrodes were used to administer 0.5 Hz stimulations to the ictal onset zones in 30 min trains daily for 7 consecutive days in an attempt to suppress seizures. RESULTS: After 1 day of stimulation, one anesthetic agent was successfully discontinued. Seizures only returned by the 4th day when the second anesthetic had been reduced by 60%. Upon returning, seizures arose from only one of the 5 original ictal onset zones. Unfortunately, RSE persisted, and she eventually died. CONCLUSIONS: In this case of RSE, low frequency stimulation through subdural electrodes transiently suppressed seizures from all but one ictal onset zone and allowed significant reduction in seizure medication. SIGNIFICANCE: Low frequency cortical stimulation may be useful in suppressing seizures.

A lack of effect from transcranial magnetic stimulation (TMS) on the vagus nerve stimulator (VNS).

OBJECTIVE: The effects of transcranial magnetic stimulation (TMS) on vagus nerve stimulation (VNS) are unknown. Understanding these effects is important before exposing individuals with an implanted VNS to TMS, as could occur in epilepsy or depression TMS research. To explore this issue, the TMS-induced current in VNS leads and whether TMS has an effect on the VNS pulse generator was assessed. METHODS: Ex vivo measurement of current in VNS leads during single-pulse TMS and pulse generator function before, during, and after single-pulse TMS was assessed. RESULTS: At the highest intensity and with the TMS coil held approximately 5 mm from the VNS wires, a 200 nA, 1.0 ms current was induced by TMS. This translates to an induced charge density of 3.3 nC/cm2/phase. The function of the pulse generator was unaffected by single-pulse TMS, even when its case was directly stimulated by the coil. CONCLUSIONS: TMS-induced current in VNS electrodes was not only well outside of the range known to be injurious to peripheral nerve, but also below the activation threshold of nerve fibers. SIGNIFICANCE: Using single-pulse TMS in individuals with VNS should not result in nerve stimulation or damage. Furthermore, single-pulse TMS does not affect the VNS pulse generator's function.

Normative data on changes in transcranial magnetic stimulation measures over a ten hour period.

OBJECTIVE: To establish normative data on the single-subject variation of resting motor thresholds and silent periods over 10 h using transcranial magnetic stimulation (TMS). METHODS: Seventeen neurologically normal volunteers aged 18-36 underwent a series of seven TMS sessions conducted over the course of a single 10-h period. During each session, resting motor threshold and cortical silent period were recorded for the first dorsal interosseus muscle of each hand during focal TMS of the contralateral motor area. RESULTS: We provide data on the normal limits of variability in these measures for averaged group data and for single subjects. Specifically, we report intersession, intrasession, and interhemispheric variability of data for each subject individually. CONCLUSIONS: Although group averages are highly reliable, individual subjects showed substantial variability over time, especially for silent periods. Interhemispheric asymmetry was a less stable indicator than previously reported. SIGNIFICANCE: These norms may guide the interpretation of changes in TMS measures within groups or within an individual patient over brief periods of time or as an immediate response to intervention.

Routine and quantitative EEG in mild traumatic brain injury.

This article reviews the pathophysiology of mild traumatic brain injury, and the findings from EEG and quantitative EEG (QEEG) testing after such an injury. Research on the clinical presentation and pathophysiology of mild traumatic brain injury is reviewed with an emphasis on details that may pertain to EEG or QEEG and their interpretation. Research reports on EEG and QEEG in mild traumatic brain injury are reviewed in this setting, and conclusions are drawn about general diagnostic results that can be determined using these tests. QEEG strengths and weaknesses are reviewed in the context of factors used to determine the clinical usefulness of proposed diagnostic tests. Clinical signs, symptoms, and the pathophysiologic axonal injury and cytotoxicity tend to clear over weeks or months after a mild head injury. Loss of consciousness might be similar to a non-convulsive seizure and accompanied subsequently by postictal-like symptoms. EEG shows slowing of the posterior dominant rhythm and increased diffuse theta slowing, which may revert to normal within hours or may clear more slowly over many weeks. There are no clear EEG or QEEG features unique to mild traumatic brain injury. Late after head injury, the correspondence is poor between electrophysiologic findings and clinical symptoms. Complicating factors are reviewed for the proposed commercial uses of QEEG as a diagnostic test for brain injury after concussion or mild traumatic brain injury. The pathophysiology, clinical symptoms and electrophysiological features tend to clear over time after mild traumatic brain injury. There are no proven pathognomonic signatures useful for identifying head injury as the cause of signs and symptoms, especially late after the injury.

Reduced anesthetization during the intracarotid amobarbital (Wada) test in patients taking carbonic anhydrase-inhibiting medications.

PURPOSE: Failure to show adequate anesthetization during the intracarotid amobarbital procedure (IAP or "Wada test") is a rare complication. After an unusually high rate of recent anesthetization failures, we sought to determine the frequency of reduced anesthetization and any common factors underlying these failures. METHODS: We reviewed the records of all patients who underwent IAP tests through the UCLA Seizure Disorder Center between September 1999 and May 2002. Age, date, epileptogenic focus, radiologist, and current medications were all considered. RESULTS: Of a total of 56 patients who underwent our intracarotid amobarbital examination, 11 (19.6%) showed either very rapid recovery (/=8 weeks after discontinuation of such medications.

Seizure incidence during single- and paired-pulse transcranial magnetic stimulation (TMS) in individuals with epilepsy.

OBJECTIVE: We reviewed published data and our own data to determine a quantitative incidence of seizure in subjects with epilepsy undergoing single- and paired-pulse transcranial magnetic stimulation (spTMS and ppTMS) and to explore conditions that may increase this risk. METHODS: A PubMed literature search was performed, and articles from this search were reviewed. Subjects from our institution also were included. RESULTS: The crude risk of a TMS-associated seizure ranges from 0.0 to 2.8% for spTMS and 0.0-3.6% for ppTMS. Medically intractable epilepsy and lowering antiepileptic drugs were associated with increased incidence. There was significant center-to-center variability that could not be explained by differences in patient population or by differences in reported stimulation parameters. In all cases, seizures were similar to each subject's typical seizure and without long-term adverse outcome. In most cases, doubt was expressed in the original reports as to whether the seizures were induced by TMS or merely coincidental. CONCLUSIONS: The incidence of seizure in a subject with epilepsy during spTMS and ppTMS appears to be small and not associated with long-term adverse outcome. The incidence is higher under the specific conditions mentioned above. SIGNIFICANCE: These findings may enable researchers to more accurately inform subjects of seizure risk during TMS.