Zoltan Mari

Identifying true brain interaction from EEG data using the imaginary part of coherency.

OBJECTIVEnThe main obstacle in interpreting EEG/MEG data in terms of brain connectivity is the fact that because of volume conduction, the activity of a single brain source can be observed in many channels. Here, we present an approach which is insensitive to false connectivity arising from volume conduction.nnnMETHODSnWe show that the (complex) coherency of non-interacting sources is necessarily real and, hence, the imaginary part of coherency provides an excellent candidate to study brain interactions. Although the usual magnitude and phase of coherency contain the same information as the real and imaginary parts, we argue that the Cartesian representation is far superior for studying brain interactions. The method is demonstrated for EEG measurements of voluntary finger movement.nnnRESULTSnWe found: (a) from 5 s before to movement onset a relatively weak interaction around 20 Hz between left and right motor areas where the contralateral side leads the ipsilateral side; and (b) approximately 2-4 s after movement, a stronger interaction also at 20 Hz in the opposite direction.nnnCONCLUSIONSnIt is possible to reliably detect brain interaction during movement from EEG data.nnnSIGNIFICANCEnThe method allows unambiguous detection of brain interaction from rhythmic EEG/MEG data.

Asymmetric spatiotemporal patterns of event-related desynchronization preceding voluntary sequential finger movements: a high-resolution EEG study

OBJECTIVEnTo study spatiotemporal patterns of event-related desynchronization (ERD) preceding voluntary sequential finger movements performed with dominant right hand and nondominant left hand.nnnMETHODSnNine subjects performed self-paced movements consisting of three key strokes with either hand. Subjects randomized the laterality and timing of movements. Electroencephalogram (EEG) was recorded from 122 channels. Reference-free EEG power measurements in the beta band were calculated off-line.nnnRESULTSnDuring motor preparation (-2 to -0.5s with respect to movement onset), contralateral preponderance of event-related desynchronization (ERD) (lateralized power) was only observed during right hand finger movements, whereas ERD during left hand finger movements was bilateral.nnnCONCLUSIONSnFor right-handers, activation on the left hemisphere during left hand movements is greater than that on the right hemisphere during right hand movements.nnnSIGNIFICANCEnWe provide further evidence for motor dominance of the left hemisphere in early period of motor preparation for complex sequential finger movements.

Neuroimaging of neuronal circuits involved in tic generation in patients with Tourette syndrome

Objective: To identify brain regions generating tics in patients with Tourette syndrome using sleep as a baseline. Methods: We used [15O]H2O PET to study nine patients with Tourette syndrome and nine matched control subjects. For patients, conditions included tic release states and sleep stage 2; and for control subjects, rest states and sleep stage 2. Results: Our study showed robust activation of cerebellum, insula, thalamus, and putamen during tic release. Conclusion: The network of structures involved in tics includes the activated regions and motor cortex. The prominent involvement of cerebellum and insula suggest their involvement in tic initiation and execution.

Open-label dose-escalation study of oral 1-octanol in patients with essential tremor.

Twenty-one single oral doses of 1-octanol were given to patients with essential tremor (ET) in an open-label dose-escalation study. The drug was well tolerated up to 64 mg/kg. The main side effect was an unusual taste. No overt intoxication was seen. There was evidence for efficacy, with a significant reduction in tremor amplitude as measured by accelerometry and handwriting that was maximal at 2 hours. Higher doses may produce more sustained benefit.

Clinico-Pathological Correlation in Progressive Ataxia and Palatal Tremor: A Novel Tauopathy

Palatal tremor (PT) is an uncommon movement disorder that has been subdivided into essential and symptomatic forms. A distinct subgroup of the symptomatic form presents with progressive ataxia and PT. The histopathology of progressive ataxia and PT has not been previously determined. This study consisted of a clinical review, histopathology, and electron microscopy of the brain of a man with progressive ataxia and PT. The inferior olivary hypertrophy was symmetrical and homogenous, and no focal pathologic lesions could be identified in the brainstem. Insoluble tau deposits were found in neurons, exclusively infratentorially. We present the clinical and pathological evaluation of a case of progressive ataxia and PT that provide evidence for a unique form of 4R tauopathy.

Remission of Gilles de la Tourette Syndrome after Heat-Induced Dehydration

Heat has been reported to exert variable effects on people with Gilles de la Tourette syndrome (TS). At age 24 years, a 32-year-old right-handed man with TS experienced a marked reduction in tics for two years after undergoing dehydration by entering a hot tub at 103°F (39.4°C) to 104°F (40.0°C) for 3 to 4 hours. On the Yale Global Tic Severity Scale (YGTSS) he scored 55 seven months before dehydration and 13 one month after dehydration. An intense heat exposure and dehydration led to an apparent remission in tics. The remission continued without the use of prescribed or nonprescribed medications or substances for two years until tics returned in the worst ever exacerbation after a tetanus immunization. The heat exposure may have altered at least temporarily his thermostat for normal heat-loss mechanisms through dopaminergic pathways from the anterior hypothalamus to the basal ganglia and the substantia nigra. Whether or not that mechanism or some other mechanism relevant to the heat exposure and/or dehydration is at play, the sudden and marked improvement in his tics needs further attention. Prospective testing of the heat and dehydration effect on tics should be pursued.

S93 Review and update on intraoperative clinical neurophysiology

The last one to make it to the operating room (OR) after surgery and anesthesia, intraoperative neuromonitoring (IONM) has now matured into a standard-of-care addition to most surgeries on parts of the central and peripheral nervous system that involve monitorable structures (such as sensory and motor pathways) and/or subject to elicitable responses (such as after-discharges or evoked potentials). Despite such maturation, many challenges remain, including full acceptance of necessity by the other main players in the OR, which can compromise the highly delicate anesthesia requirements of IONM that often run counter of other needs in the OR (such as light anesthesia and only certain agents to make sure cortical functions remain adequate to record evoked potentials or avoidance of full paralysis to allow sufficient muscle activity either for motor evoked potential monitoring or making motor nerve injury detectable by allowing meaningful EMG activity). In addition to discussing some of the main practical challenges IONM faces today, this review and update also aims to bring the audience up to speed regarding some of the newer techniques and protocols, as well as providing a practical overview of this rapidly growing and changing field with regards to the most important and currently approved methods.

S94 Update on technological advancements in invasive neurophysiological activity monitoring and deep-brain stimulation

Over the past decade technological advances have created entirely new opportunities for studying and understanding neural circuits and brain activities. Meanwhile the expansion of therapeutic scope of Deep Brain Stimulation has continuously happened together with the improvement in precision of stimulation and neurosurgical implantation techniques. The standard open-loop setup of high-frequency (HF) DBS utilizes permanent HF electrical pulse train, where electrical stimulation is administered continuously to the target areas irrespectively of the ongoing neural dynamics. Recent studies demonstrate that an adaptive, closed-loop DBS setup might be preferable over the open-loop setup. This presentation summarizes the technological advancements in closed-loop DBS system designs. We will discuss state-of-the-art implantable multielectrode technologies, requirements checklist for clinical practice, current issues, electronics designs as well as field potential and single unit activity based biomarkers with particular interest on Phase-amplitude coupling.

Clinical Reasoning: A 57-year-old man with jaw spasms

A 57-year-old man presented with spasms of his left jaw. Two years prior, he had developed left-sided facial numbness followed by development of left-sided shock-like pain and then involuntary and repetitive movements of the jaw-closing muscles. Jaw muscle contractions were episodic, interfered with chewing and talking, and led to frequent tongue biting. Individual spasms varied from seconds to minutes and he reported that function in between episodes was normal, although his wife felt he spoke with reduced mouth opening. He sometimes awoke with a bloody tongue, suggesting that contractions occurred during waking and sleep. He had no history of premonitory sensation or relief associated with the spasms. He reported no difficulty swallowing.