Biomedical subjects

Mark D Holmes

Publications and source records attributed to Mark D Holmes.

23 records · Page 2Linked to original sources

PubMed2003

Identifying potential surgical candidates in patients with evidence of bitemporal epilepsy.

PURPOSE: To determine which patients with evidence of medically refractory bitemporal epilepsy are potentially good candidates for surgical therapy. METHODS: We reviewed 42 adults with intractable seizures who were found to have bitemporal ictal onsets, based on scalp video-EEG long-term monitoring (LTM). All underwent invasive LTM before surgery. Surgical outcomes were classified as seizure free, >75% reduction in seizures, or <75% reduction in seizures, >or=1 year after resection. We related the following factors to outcome: (a). >75% preponderance of interictal scalp EEG discharges to one temporal region; (b). magnetic resonance imaging (MRI) findings; (c). lateralizing deficits on verbal or visual reproduction memory testing; and (d). memory failure with injection contralateral to side of surgery on Wada testing. RESULTS: Twenty-six (62%) of 42 patients had unilateral ictal onsets based on intracranial studies. Seizure freedom (occurring in 64% of this group), or >75% seizure reduction (found in 12% of subjects) occurred only when at least one of the following three factors was concordant with the side of surgery: preponderance of interictal scalp EEG discharges, unilateral temporal lesion on MRI, or lateralizing verbal or visual reproduction memory deficits on neuropsychological tests (p = 0.004). Seven subjects with bilateral ictal onsets based on intracranial studies had resections based on preponderance of seizures to one side, or other lateralizing noninvasive abnormality. Five of these (all of whom had >or=80% of seizures originating from one side) had >75% reduction in seizures. CONCLUSIONS: Invasive monitoring to pursue possible surgical therapy for patients with surface EEG evidence of bitemporal epilepsy may be justified only when some lateralizing feature is found in other noninvasive assessments.

Adolescent↗

PubMed2003

Vagal nerve stimulation induces intermittent hypocapnia.

PURPOSE: To study whether respiratory alteration caused by vagal nerve stimulation (VNS) can change end-tidal carbon dioxide (EtCO2) levels. METHODS: We performed polygraphic recordings including capnographic monitoring during daytime sleep on adults with VNS therapy. RESULTS: Ten of 13 patients showed VNS-induced alterations in the frequency or amplitude of respiration. Five patients had a consistent increase in respiratory rate with a simultaneous, consistent and significant decrease (p < 0.01; 5-22%) in EtCO2 during VNS. Three subjects showed occasional decreases in EtCO2 during VNS, and two showed no clearly detectable VNS-related EtCO2 changes. CONCLUSIONS: Our findings suggest that VNS may alter brain CO2 levels through changes in respiration. Because carbon dioxide (CO2) has potent effects on various brain functions, it is possible that these transient CO2 changes may have an effect on the state transitions between interictal and preictal states.

Adult↗

PubMed2002

Interleukin-1beta and tumour necrosis factor-alpha increase microvascular leakage in the guinea pig trachea.

OBJECTIVE: Airway microvascular leakage is considered to be an important component of airway inflammation in asthma. In the present study we examined the effect of interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNFalpha) on airway microvascular leakage in vivo. METHODOLOGY: Tracheal Evans blue extravasation was examined in an isolated tracheal segment, in anaesthetized mechanically ventilated guinea pigs. Baseline tracheal microvascular leakage was measured in five animals. As a control group for aerosol challenge, the isolated tracheal segment (n = 5) underwent saline aerosol challenge. To test whether a combination of IL-1beta (10 ng/mL) and TNFalpha (100 ng/mL) induced Evans blue extravasation, the trachea was exposed to an aerosol of these cytokines (n = 5). As a positive control the tracheal segment was challenged with histamine aerosol (5 x 10(-2) mol) (n = 3). All aerosol challenges were for 1 min. RESULTS: TNFalpha and IL-1beta aerosol challenge significantly increased Evans blue extravasation (28.9 +/- 1.6 microg/g wet tissue, mean +/- SE) compared to saline challenge (13.8 +/- 3.0 microg/g; P < 0.05). Tracheal dye extravasation without aerosol challenge, was not significantly different from saline-challenged animals (17.5 +/- 2.9 and 13.8 +/- 3.0 microg/g, respectively). Histamine significantly increased Evans blue extravasation (50.1 +/- 4.8 microg/g; P < 0.05) compared to saline challenge. CONCLUSION: Pro-inflammatory cytokines, TNFalpha and IL-1beta are able to induce significant microvascular leakage in the guinea pig trachea.

Administration, Inhalation↗

PubMed2002

Do nonspecific focal EEG slowing and epileptiform abnormalities favor one hemisphere?

PURPOSE: Several EEG-based studies suggest that epileptiform activity originates from the left more than the right hemisphere. In contrast, other pathophysiologies such as stroke lateralize relatively symmetrically. Study of focal slowing and other EEG abnormalities allows assessment of favoring as well as referral and interpretation bias. METHODS: The 1,331 consecutive adult EEG reports were reviewed for epileptiform discharges (EDs) and nonepileptiform focal slowing. Side of slowing or EDs, interpreting electoencephalographer, and whether the patient was undergoing long-term monitoring or routine EEG were tallied. Results were statistically analyzed. RESULTS: Focal slowing occurred symmetrically; EDs favored the left hemisphere (p < 0.01). CONCLUSIONS: The left hemisphere may be more prone to epileptiform abnormalities in adults, but not to the nonspecific pathophysiologic processes that cause slowing. These findings suggest that potential interpretation bias does not influence left hemispheric favoring of EDs and instead may implicate a biologic etiology.

Adult↗

PubMedDate not supplied

Metastability, instability, and state transition in neocortex.

Mesoscopic patterns of neural activity were sought in multichannel EEGs of rabbits that were trained to respond to conditioned stimuli (CSs) in visual, auditory and somatic modalities. Spatiotemporal patterns were sought of oscillations in the beta and gamma ranges. The techniques required for preprocessing EEGs in search of global patterns were diametrically opposed to those needed for localization of modular EEG signals. Frames were found in the form of intermittent spatial patterns of phase and amplitude modulation (AM and PM) of carrier waves in beta and gamma ranges that served to classify EEG frames with respect to CSs. A model based on the intentional action-perception cycle is proposed to complement the information processing model.

Animals↗