PubMed Health⌕ Search

Biomedical subjects

Richard Wennberg

Publications and source records attributed to Richard Wennberg.

At least 19 recordsLinked to original sources
PubMed2006

Bursting activity of neurons in the human anterior thalamic nucleus.

Single unit microelectrode recordings were obtained under local anesthesia in 5 patients who underwent placement of deep brain stimulation electrodes in the anterior thalamic nucleus for control of intractable epilepsy. Of the 261 neurons recorded, 145 were in the anterior nucleus (AN), with the remainder ventral to AN in nucleus cucularis and dorsal dorsomedian nucleus (DM). 126 of the 261 neurons fired in bursts, and of these, 74 cells were analyzed in greater detail to characterize their bursting pattern. The bursts in 70% of the bursting neurons were characterized as low-threshold calcium spike (LTS) mediated bursts, on the basis of their intraburst firing pattern. The bursts of the remainder, although similar to LTS bursts, did not fulfil all of the criteria for an LTS burst and were termed atypical bursting cells. LTS and atypical bursting cells were found both within AN and in the nucleus cucularis and dorsal DM. The LTS bursting observed in these patients may be due to the altered electrophysiological state of the patients studied since LTS bursting in thalamus is usually only observed during sleep. This study describes for the first time the properties of this nucleus in humans and may be important in furthering our knowledge of thalamic mechanisms of epileptogenesis.

Action Potentials↗
PubMed2006

Parietal lobe source localization and sensitivity to hyperventilation in a patient with subclinical rhythmic electrographic discharges of adults (SREDA).

OBJECTIVE: Subclinical rhythmic electrographic discharges of adults (SREDA) is currently considered a benign EEG pattern of uncertain significance. The underlying cortical sources and generating mechanisms are unknown. We performed a source localization analysis of SREDA with the aim of better understanding this unusual EEG pattern. METHODS: Multiple spontaneous episodes of typical SREDA were recorded in a patient during continuous EEG monitoring. Additional SREDA episodes were induced by hyperventilation. Source localization was carried out using statistical non-parametric mapping (SNPM) of low resolution electromagnetic tomography (LORETA). RESULTS: SNPM of both time- and frequency-domain LORETA revealed a widespread biparietal cortical origin of SREDA, the anatomical distribution of which included the parietal operculum and the known vascular watershed areas between anterior, middle and posterior cerebral arteries. Vigorous deep hyperventilation induced SREDA on three of four attempts. Mean duration of the hyperventilation-induced SREDA was approximately three times longer than spontaneous events. CONCLUSIONS: Investigations in this patient with typical SREDA revealed hyperventilation sensitivity and a posterior hemispheric source localization maximal in the parietal cortex bilaterally, in large part overlying the anatomical distribution of the vascular watershed areas. SIGNIFICANCE: The source localization results and sensitivity to hyperventilation suggest some sort of association between cerebral vascular supply and SREDA, as originally proposed by Naquet et al. [Naquet R, Louard C, Rhodes J, Vigouroux M. A propos de certaines décharges paroxystiques du carrefour temporo-pariéto-occipital. Leur activation par l'hypoxie. Rev Neurol 1961;105:203-207.].

Aged↗
PubMed2006

Whiplash and concussion: similar acute changes in middle-latency SEPs.

OBJECTIVE: Middle-latency somatosensory evoked potentials (SEPs) following median nerve stimulation can provide a sensitive measure of cortical function. We sought to determine whether the mechanical forces of whiplash injury or concussion alter normal processing of middle-latency SEPs. METHODS: In a cross-sectional pilot study 20 subjects with whiplash were investigated (50% between 0.5-2 months and 50% between 6-41 months post injury) and compared to 83 healthy subjects using a standard middle-latency SEP procedure. In a subsequent prospective study subjects with either acute whiplash (n=13) or Grade 3 concussion (n=16) were investigated within 48 hours and again three months post injury. RESULTS: In the pilot study the middle-latency SEP component N60 was significantly increased in the ten subjects investigated within two months after whiplash. In contrast, the ten subjects examined more than six months after injury showed normal latencies. In the prospective study N60 latencies were increased after whiplash and concussion when tested within 48 hours of injury. At three months, latencies were improved though still significantly different from controls post whiplash and concussion. CONCLUSIONS: Both whiplash injury and concussion alter processing of the middle-latency SEP component N60 in the acute post traumatic period. The acute changes appear to normalize between three-six months post injury. The SEP similarities suggest that the overlapping clinical symptomatology post whiplash and concussion may reflect a similar underlying mechanism of rotational mild traumatic brain injury.

Adolescent↗
PubMed2005

Effect of ice surface size on collision rates and head impacts at the World Junior Hockey Championships, 2002 to 2004.

OBJECTIVE: To determine if collision rates and head impacts in elite junior hockey differed between games played on the small North American ice surface (85 ft wide), an intermediate-size Finnish ice surface (94 ft wide), and the large standard international ice surface (100 ft wide). DESIGN: Videotape analysis of all games involving Team Canada from the 2002 (large ice, Czech Republic), 2003 (small ice, Canada), and 2004 (intermediate ice, Finland) World Junior Championships. All collisions were counted and separated into various categories (volitional player/player bodychecks, into boards or open ice, plus accidental/incidental player/boards, player/ice, head/stick, head/puck). Further subdivisions included collisions involving the head directly or indirectly and notably severe head impacts. RESULTS: Small, intermediate, and large ice surface mean collisions/game, respectively, were 295, 258, 222, total collisions; 251, 220, 181, volitional bodychecks; 126, 115, 88, into boards; 125, 106, 93, open ice; 71, 52, 44, total head; 44, 36, 30, indirect head; 26, 16, 13, direct head; and 1.3, 0.5, 0.3, severe head (P < 0.05 for small-intermediate ice and intermediate-large ice differences in total collisions; P < 0.005 for small-large ice difference; P < 0.05 for small-intermediate ice differences in head impacts; P < 0.01 for small-large ice differences in total and severe head impacts). CONCLUSIONS: There is a significant inverse correlation between ice size and collision rates in elite hockey, including direct, indirect, and severe head impacts. These findings suggest that uniform usage of the larger international rinks could reduce the risk of injury, and specifically, concussions in elite hockey by decreasing the occurrence of collisions and head impacts.

Brain Concussion↗
PubMed2005

Phase synchronization measurements using electroencephalographic recordings: what can we really say about neuronal synchrony?

Phase synchrony analysis is a relatively new concept that is being increasingly used on neurophysiological data obtained through different methodologies. It is currently believed that phase synchrony is an important signature of information binding between distant sites of the brain, especially during cognitive tasks. Electroencephalographic (EEG) recordings are the most widely used recording technique for recording brain signals and assessing phase synchrony patterns. In this study, we address the suitability of phase synchrony analysis in EEG recordings. Using geometrical arguments and numerical examples, employing EEG and magnetoencephalographic data, we show that the presence of a common reference signal in the case of EEG recordings results in a distortion of the synchrony values observed, in that the amplitudes of the signals influence the synchrony measured, and in general destroys the intended physical interpretation of phase synchrony.

Action Potentials↗
PubMed2004

Collision frequency in elite hockey on North American versus international size rinks.

OBJECTIVE: Body impact or collision is the risk factor underlying all sports-related concussions. This study sought to determine whether collision rates in elite hockey differ between games played on North American size rinks as compared to games played on larger international size ice surfaces. METHODS: Videotapes of games from the 2001 and 2002 National Hockey League Stanley Cup finals, World Junior championships and the 2002 Winter Olympics were analyzed, with all collisions counted and separated into various categories (player/player bodycheck, player/player into boards, player/boards, player/ice, head/stick, head/puck). Further subdivisions included collisions involving the head directly or indirectly. Twenty-two games were analyzed, 11 played on the small ice and 11 on the big ice. RESULTS: Significantly more collisions of all types (in all categories and subdivisions within categories) were found to occur on the smaller North American ice surface (P value differences from 0.01 to 0.00001). CONCLUSIONS: The results of this study showed significantly fewer collisions of all types in elite hockey games played on the international size ice surface. The comparison groups studied here did differ in some aspects other than ice size and so replication of the findings with even more closely matched groups will be needed before definitive conclusions can be drawn. However, if these findings are replicable, it would suggest that a change to uniform usage of the larger international rinks, with no rule changes or other alterations in the game, could provide direct primary prevention to reduce the number of collisions, and, by extension, concussions, that occur in the sport.

Athletic Injuries↗
PubMed2004

Bilateral horizontal gaze palsy in presumed paraneoplastic brainstem encephalitis associated with a benign ovarian teratoma.

A 28-year-old woman with a previous history of recurrent benign ovarian teratoma developed a bilateral horizontal gaze palsy, a right facial paresis, and bilateral trigeminal hypesthesia. Magnetic resonance imaging disclosed high signal in the rostral pons. Results of all other laboratory studies, including those for antineuronal antibodies (anti-Hu, anti-Yo, anti-Ri, anti-Tr, anti-Ma1, anti-Ma2, and anti-CV2/CRMP5), were negative. Pelvic ultrasound revealed a residual mass in the left ovary, which was confirmed as teratoma on surgical pathological examination. Complete neurologic recovery occurred within two weeks of surgical removal of the teratoma and treatment with intravenous corticosteroids and immunoglobulin. This case demonstrates that a search for an occult neoplasm is extremely important in the diagnosis of presumed paraneoplastic encephalitis even if antineuronal antibodies are not found.

Adult↗
PubMed2003

Panic attack semiology in right temporal lobe epilepsy.

BACKGROUND: Panic attack semiology as a manifestation of epileptic seizures may lead to difficulties and delay in diagnosis. We present a case series to demonstrate the association of ictal panic and anxiety symptoms with partial seizures lateralized to the right temporal lobe. METHODS: From 112 consecutive patients with intractable temporal lobe epilepsy (59 right, 53 left) referred for video-EEG monitoring, five patients were identified whose seizures had been diagnosed as panic attacks in the past. Their ictal symptomatology included feelings of panic and impending doom, hyper-ventilation, palpitation, diaphoresis, shortness of breath and generalized paresthesiae. Ictal panic was not identified in 72 patients with extra temporal epilepsy investigated during the same period. RESULTS: EEG documented a right anterior to mid-temporal focus in all five patients. Brain MRI or pathology showed right mesial temporal sclerosis in four and a right temporal ganglioglioma in one. Ictal tachycardia was documented with EEG-EKG recording in the latter patient, prior to right anterior temporal lobectomy and amygdalohippocampectomy. Reinvestigation of this patient five years later for recurrent seizures, no longer associated with panic symptomatology, showed right temporal ictal onsets with seizure spread to the left temporal lobe, now associated with ictal bradycardia. CONCLUSIONS: Our case series provides further evidence to support a relationship between panic attack symptomatology and ictal involvement of the right mesial temporal region [Published with video sequences].

Adult↗