Ichiro Nakajima

Pupil dilation response to noxious stimulation: Effect of varying nitrous oxide concentration

OBJECTIVE This report examines the pain-related pupil dilation response (PDR), tracking it across mixture concentrations of nitrous oxide (N(2)O) in oxygen (O(2)) and relating its variation to change in long latency somatosensory evoked potentials (SEPs) and visual analogue scale (VAS) pain report. METHODS We varied mixture concentrations of N(2)O in O(2) (0%, 10%, 30%, and 50%), measuring PDR, SEP and VAS responses to painful electrical fingertip stimulation at high and low intensities in 15 volunteers. RESULTS Mixed effect model statistical analyses revealed that: (1) PDR increased significantly with stimulus intensity and constricted significantly with mixture concentration; (2) SEP and VAS decreased significantly with increasing mixture concentration; (3) PDR correlated with SEP amplitude and VAS across mixture concentrations; (4) subjects differed significantly in: (a) baseline PDR and SEP amplitudes, (b) rate of change of these measures across mixture concentrations; and (5) VAS increased significantly with stimulus intensity and decreased significantly with mixture concentration without significant individual differences. CONCLUSIONS The findings support the hypothesis that the pain-related PDR is a complex brain-mediated response rather than a simple sympathetic reflex. SIGNIFICANCE PDR may provide a useful indicator for studying the central processing of noxious stimuli and the effects of analgesic interventions.

Cortical potentials associated with voluntary biting movement in humans

We compared the distribution of Bereitschaftspotentials (BPs) on both sides of the scalp preceding jaw biting movements in order to identify the relationship between the cortical regions and the activation of the masseter muscle in 10 healthy subjects. The BPs were recorded from the midline-central, central and temporal areas of the scalp according to the international 10-20 system, preceding self-paced biting on one side. The cortical negative potentials began 1.0 approximately 1.5 s before the EMG onset of the masseter muscle. All of these negative potentials could be considered to be BPs, and the additional negative slope component (NS) occurred 70 approximately 80 ms before the EMG onset of the masseter muscle. The BPs were detected from all the recorded regions of the scalp, while the NS was observed only from the bilateral temporal area. The amplitudes of BPs and NSs were largest in the temporal areas (T3 and T4) that were ipsilateral to the biting. The rates of occurrence of NS at T3 and T4 ipsilateral temporal areas were 80% and 60%, respectively. These results suggest that unilateral biting movements may be controlled mainly from the ipsilateral hemisphere.

Contingent negative variations associated with command swallowing in humans

OBJECTIVE To clarify the role of the cerebral cortex in the swallowing movement, the difference between the waveforms of contingent negative variation (CNV) for the command swallowing and movement-related cortical potential (MRCP) obtained during the volitional swallowing task in humans was investigated. METHODS Subjects were instructed to swallow their saliva as quickly as possible in response to a sound signal 4s after the onset of a self-paced breath holding in the command swallowing task or to swallow it while holding their breath for 4s in the volitional swallowing task. RESULTS CNV and MRCP appeared at five recording areas 1.5 and 2.0s before the onset of the suprahyoid muscle activation determined by the electromyography (EMG) during the command swallowing and volitional swallowing tasks, respectively. The CNV amplitude during the command swallowing task was significantly higher than the MRCP amplitude during the volitional swallowing task (p<0.01). However, the suprahyoid muscle activities during both tasks were not significantly different (p>0.05). CONCLUSIONS These results indicated that CNV may reflect the activities of the prefrontal cortex, in addition to the supplementary motor area, suggesting that the processing of the cue to swallow activates brain areas more widely than the volitional swallowing itself. SIGNIFICANCE It is possible to clarify the cognitive functions associated with command swallowing by analyzing CNV.

Contingent Negative Variations Associated with Jaw Opening in Humans

We examined the relationship between contingent negative variation (CNV) amplitude and digastric muscle activity in jaw-opening motor task. Subjects were instructed to open their jaws in response to a sound stimulus following a visual warning stimulus. Electroencephalograms were averaged by using the visual stimulus pulse as a trigger. Bilateral CNVs were clearly recorded at several cortical locations, with a tendency for larger amplitudes at temporal placements.

Assessment of quality and interpretation of panoramic radiographs obtained in the Lao People’s Democratic Republic as part of a teleradiology collaboration with Japan

As part of quality assessment of a teleradiology program we evaluated the validity of patient information received, the quality of panoramic radiography imaging in Laos, and the ability of a Laotian radiologist to detect temporomandibular joint abnormalities. The amount of patient information gathered from 2,021 scans of panoramic radiographs was evaluated by triage before image diagnosis. Among the radiographs from 2,021 patients, primary triage indicated that there was insufficient information for 794 (39.3%) patients. Secondary triage to assess imaging failure included 1,227 radiographs, four of which were excluded from imaging diagnosis because of unacceptable image flaws. In total, 2,446 joints from 1,223 radiographs were evaluated for temporomandibular joint abnormalities in order to compare the image interpretation abilities of Laotian and Japanese radiologists. The kappa coefficient was 0.836 (P < 0.01) for the agreement between the two observers in detecting temporomandibular joint abnormalities on radiographs. We conclude that additional efforts are needed in order to overcome the challenges of maintaining quality in imaging techniques and diagnoses in Laos.

Characteristics of lower-jaw-position sensation with respect to oral-jaw functions in patients with cerebral palsy

Abstract In order to investigate the effects of desensitization which is induced by the application of a vibration stimulus simulating massage to patients with cerebral palsy (CP) on the lower-jaw-position sensation, we compared the masticatory-muscle sensation of patients with CP with that of healthy adults without functional abnormalities of the jaw and oral cavity who were used as control subjects, using a lower-jaw-position sensation discrimination test. The subjects of the study were eight patients with CP and eight healthy adults as control subjects. The following findings were obtained. 1)When the discrimination ability in healthy adults was compared between before and after the stimulus application, it was significantly higher after the stimulus application when the interincisal distance was smaller (9.5mm) than that with the reference stick. 2)When the discrimination ability of patients with CP was compared between before and after the stimulus application, it was significantly lower after the stimulus application when the interincisal distance was smaller (9.5mm) than that with the reference stick. Thus, results for the patients with CP are contrary to those for healthy adults; this is because of the appearance of the tonic vibration reflex in CP patients, which results in a decrease in the activity of γ-motor neurons. The threshold value of muscle sensation was increased by the application of vibration stimulus. Consequently, the discrimination ability of the patients with CP increased.

Relationship between reaction time for mandibular movement and the level of muscular discharge of the masticatory muscles in a reaction time task in patients with cerebral palsy

Abstract We hypothesized that patients with Cerebral Palsy (CP) are affected by the preparatory process in the central nervous system for initiating a jaw movement. We tested this hypothesis on 13 in patients with CP (average: 36.9 years old) and 13 in healthy adults (average: 34.7 years old) as subjects. We recorded the muscular discharge of the masticatory muscles from the time a warning stimulus was presented to the time an instruction stimulus was presented during the reaction time (RT) with the open mouth movements in patients with CP. The following results were obtained. The RT for executing the open mouth movements is significantly longer in the CP subjects than in the healthy subjects. In the CP subjects during the movement task, the level of muscular discharge of the masticatory muscles in the 1-s period before presentation of a warning stimulus was significantly lower than that in the 1-s period or in the period from 1s to 2s after the presentation of the warning stimulus. The other side, In the healthy subjects, no change in the muscular discharge of the masticatory muscles was observed. However, In the CP subjects and in the healthy subjects during the nonmovement task, no change in the level of muscular discharge of the masticatory muscles in each period was observed. A significant correlation was observed between the percent change of the level of muscular discharge of the masseter muscle (or the digastric muscle) and RT for the open mouth movement. From the results of this study, as one of the reasons for the difficulty in executing smooth voluntary movements in the oromandibular region in individuals with CP, we consider that the movement is delayed because the period of preparation of the movement is significantly prolonged in individuals with CP although they started the preparation of the movement at an earlier period than in individuals who do not have CP.

Characteristics of sensing lower-jaw-position in patients with cerebral palsy during laughing gas-induced sedation

Abstract To clarify the effects of the applied during sedation with nitrous oxide (hereafter referred to as laughing gas) on the ability of muscles attached to the lower jaw to sense lower-jaw-position and on the sensation of muscle spindles attached to the lower jaw in patients with cerebral palsy (CP) using healthy adult subjects without functional abnormalities of the jaws and oral cavities as control subjects (hereafter referred to as healthy subjects). Experiments were performed under the following conditions: for each subject, before the inhalation of laughing gas (LG) and oxygen (air-inhalation condition: referred to as without LG inhalation) and during the inhalation of LG and oxygen (inhalation condition of LG and oxygen under LG-induced sedation: referred to as during LG inhalation). Subjects in the experiments were eight CP patients and eight healthy people as controls. The ability to discriminate lowerjaw- position was estimated by asking the subjects to determine whether the diameter of a test stick was larger or smaller than that of a reference stick after performing the following tasks: a) holding a reference stick between the central teeth of their upper and lower jaws for 5s, and b) replacing the reference stick with a test stick and holding it at the same position for 5s, and the test stick was then removed. The following findings were obtained. 1)In comparing discrimination ability in the absence of LG-induced sedation and that during LG-induced sedation of healthy control subjects, the rate of mis-estimation (RME) was significantly larger during LG-induced sedation than in the absence of LG-induced sedation for a test stick diameter (10.5mm or 11.0mm) larger than the reference stick diameter (10.0mm) (P 0.05). 2)In comparing discrimination ability in the absence of LG-induced sedation and that during LG-induced sedation of CP patients, RME was significantly smaller during LG-induced sedation than in the absence of LG-induced sedation, when the test stick diameter (9.5mm) was smaller than the reference stick diameter (P 0.05). These results indicate that neural functions are inhibited at the upper level of the central nervous system in CP patients, leading to the attenuation of sustained increase in muscle tonus that is characteristic of CP patients. In summary, it seems that the LG has some inhibitory effect on the activity of γ-motor neurons innervating muscle spindles attached to the lower jaw via the upper level of the central nervous system and that this inhibitory effect contributes to an improvement in the discrimination ability.

Study on the relationship between sensation of the mandibular position and the oral dysfunctions in the cerebral palsy patients

Abstract The ability to discriminate the sensation of the mandibular position in the cerebral palsy (CP) patients was studied and the relationship between this ability to discriminate the sensation of the mandibular position and the oral dysfunctions was evaluated. Interdental dimension discrimination tests (IDD test) were performed in order to evaluate the ability to discriminate the sensation of the mandibular position in 18 CP patients and in 15 healthy individuals. Using the test result, points of subjective equality (PSE) and difference limen (DL) were obtained. In addition, the oral dysfunction index was used to evaluate the oral dysfunctions of the CP patients. The results obtained are as follows 1) PSE in the CP patients was significantly lower than that in the healthy individuals. 2) No significant difference was observed in DL between the CP patients and healthy individuals. 3) A significant correlation was observed between PSE and ODI in the CP patients.

873 PUPIL DILATION RESPONSE TO NOXIOUS STIMULATION: EFFECT OF VARYING STIMULUS PATTERN

In this study, we aimed that hypnosis can be used as a method of pain control in pre, post surgical periods and during operation. We performed hypnosis on a cholecystectomy case who is 55 years old woman. She had a diagnosis with cholecystolithiasis and cholestasis. The patient was prepared for surgical operation by using hypnosis. This hypnosis method is called as Awareness Under Conscious Hypnosis (AUCH) contains three steps as MAYA (Making Acceptance with Your Awareness), induction and auto-hypnosis. Before or during operation no medicament was used for anesthesia and sedation. She did not feel any pain or discomfort during the incisions, tractions, cauterizations and sewing. She was painless with only hypnosis during and after operation. She was conscious, cooperative and quite happy during her surgery and sometimes she also volunteered to sing songs, tell stories. Her blood pressure was about 135/85mmHg and heart rate was 80−90/bpm during the operation duration. She was painless, very comfortable in dressing and walking and had no restriction in her movements after operation. This condition continued while she was staying at the hospital. She well cured and went home in 40 hours whereas the usual curing time is about 4 days for this kind of operations. As it is seen in this case, hypnosis can be used as a reliable and effective method for pain control in surgical operations. This makes us eager to study on hypnosis in pain control.