Hemicrania continua secondary to an ipsilateral brainstem lesion

We describe a 47-year-old woman with a 3-year history of a continuum mild-moderate right-side headache, with exacerbations, associated with stabbing volleys of pain on right orbit-temporal region (10/10) and right eye ptosis and lacrimation with conjunctival injection. The pain was completely abolished with indomethacin (100 mg per day). The diagnosis of hemicrania continua was made according to the International Headache Society (IHS) criteria. The headache presentation was precipitated by a stroke and a right-side brainstem lesion was present at magnetic resonance imaging. This case report shows anatomoclinical evidence of the involvement of brainstem structures on the pathophysiology of hemicrania continua.     

Analysis of the joint crack by simultaneous recording of sound and tension

In order to elucidate the significance of the noise often associated with a chiropractic adjustment, the joint crack has been analyzed using a simultaneous sound and tension recording system. It was found that, during the crack, which is a consistent double-peak wave, a drop in tension occurred immediately after the first sound wave, indicating separation of the articular surfaces (adjustment). The significance of the crack as an integral part of a chiropractic adjustment, where separation of the articular surfaces is desired, is then discussed.     

Detecting faked penile responses to erotic stimuli

Eighteen men were instructed to fake penile responses to discrete sexual stimuli presented auditorily or visually. The same stimuli were presented a second time following instruction on faking. Sexual responses were monitored using a penile plethysmograph (PPG). Further physiological response measures to detect faking attempts included the Galvanic Skin Response (GSR) and respiration (RESP). Faking attempts were found to be more successful to audio than visual stimuli, especially if the stimuli were relatively weaker. Arousal was much more difficult to fake than suppression. The more intense the efforts to fake, and especially following faking instructions, the more transparent the faking efforts. GSR and RESP added measurably to the detection of faked PPG responses which would have appeared otherwise to be genuine responses.     

The cochlear prosthesis. Bringing the world of sound to the deaf

The complexity of coding in the auditory nerve makes it unlikely that a prosthesis for deaf persons can exactly duplicate the normal function of the ear. With recent advances, however, cochlear prostheses can perform some of the frequency-analysis functions of the normal ear. Cochlear prostheses are effective aids to lipreading and allow recognition of some sounds without visual cues, thus enhancing the profoundly deaf person's communication skills substantially.     

Ethnic differences in responses to multiple experimental pain stimuli

A growing body of literature suggests that the experience of clinical pain differs across ethnocultural groups. Additionally, some evidence indicates greater sensitivity to experimentally induced pain among African Americans; however, most studies have included only one pain modality. This study examined ethnic differences in responses to multiple experimental pain stimuli, including heat pain, cold pressor pain, and ischemic pain. Heat pain threshold and tolerance, ratings of repetitive suprathreshold heat, and ischemic and cold pressor pain threshold and tolerance were assessed in 120 (62 African American, 58 white) healthy young adults. Also, several psychological instruments were administered. No ethnic group differences emerged for threshold measures, but African Americans had lower tolerances for heat pain, cold pressor pain and ischemic pain compared to whites. Ratings of intensity and unpleasantness for suprathreshold heat stimuli were significantly higher among African Americans. African Americans reported greater use of passive pain coping strategies and higher levels of hypervigilance. Controlling for passive pain coping did not account for group differences in pain responses, while controlling for hypervigilance rendered group differences in heat pain tolerance and ischemic pain tolerance non-significant. These findings demonstrate differences in laboratory pain responses between African Americans and whites across multiple stimulus modalities, and effect sizes for these differences in pain tolerance were moderate to large for suprathreshold measures. Hypervigilance partly accounted for group differences. Additional research to determine the mechanisms underlying these effects is warranted.     

Hemodynamic responses to noxious stimuli in brain-dead organ donors

The case report presents evidence for the spinal origin of the marked hypertensive reponses to noxious stimuli that may occur in organ donors who fulfill the commonly accepted criteria of brain death. Cardiovascular spinal reflex activity does not invalidate these criteria. For the first time, the catecholamine plasma concentrations have been determined during spinal pressor reflex activity. Circulating epinephrine increased more markedly than norepinephrine in both cases, rising to 4.7 and 44 times the baseline concentration respectively. The relation between plasma norpinephrine and epinephrine suggests involvement of the adrenal medulla in the reflex arc. The literature on spinal hemodynamic reflexes is reviewed.     

Sensitization of trigeminal caudalis neuronal responses to intraoral acid and salt stimuli and desensitization by nicotine

In human studies, repeated intraoral application of strong acidic or salt stimuli induces irritation that progressively increases across trials (sensitization), whereas irritation elicited by nicotine progressively decreases (desensitization). We investigated whether nociceptive neurons in trigeminal subnucleus caudalis (Vc) exhibit increasing or decreasing patterns of firing to the intraoral application of these irritants. In rats anesthetized with halothane and thiopental, single-unit recordings were made from nociceptive neurons in superficial layers of dorsomedial Vc that responded to mechanical and noxious thermal and chemical stimulation of the tongue. NaCl (5M), citric acid (300 mM), pentanoic acid (300 mM) or nicotine (600 mM) were separately delivered to the tongue by constant flow (0.32 ml/min) for 15 or 25 min. NaCl, citric acid and pentanoic acid each elicited a progressive, significant increase in Vc neuronal firing over the initial 10 min to a plateau level that was maintained for the stimulus duration. Nicotine induced a significant increase in firing rate of Vc neurons within 6 min, followed by a decline back to the baseline level over the ensuing 10 min. Following a rest period, reapplication of nicotine no longer activated Vc neurons, indicative of self-desensitization. We additionally tested for nicotine cross-desensitization to acid. After recording the responses of Vc neurons to pentanoic acid and noxious heat, nicotine was then applied for 15 min. Post-nicotine responses to pentanoic acid were markedly reduced (to 13% of control), indicative of cross-desensitization; responses to noxious heat were also reduced to a lesser degree (to 71% of control). The progressive increase in Vc neuronal firing elicited by NaCl and acid, and the decline in firing after initial nicotinic excitation, resemble psychophysical patterns of sensitization and desensitization, respectively, and support the involvement of Vc neurons in the signaling of oral irritant sensations.     

Single trial variability of EEG and fMRI responses to visual stimuli

Recent EEG-fMRI studies have suggested a novel method of data fusion which uses single trial (ST) estimates of event-related potentials in the fMRI analysis. This is potentially very powerful, but rests on the assumption that the ST variability observed in EEG is reflected in the fMRI signal. The current study investigated this assumption and compared two different data processing strategies for each modality. Five subjects underwent separate EEG and fMRI sessions with checkerboard stimuli at two contrasts. EEG data were preprocessed using wavelet denoising and independent component analysis (ICA), whilst the general linear model and ICA were used for fMRI. Amplitudes and latencies of the P1 and N2 components of the visual evoked potential (VEP) were calculated for each trial. For fMRI, the amplitudes and latencies of the ST haemodynamic responses (HR) were calculated. Within modality, the results for the two processing methods were significantly correlated in the majority of data sets. Across modality, the average amplitudes of the VEPs and HRs were also significantly correlated. Examination of ST variability demonstrated that the amplitudes of the mean VEPs and HRs are both influenced by the latency variability of the ST responses to a greater extent than the amplitude variability. For high contrast stimuli the latency variability in EEG and fMRI was significantly correlated, with a similar trend seen for the low contrast stimuli. The results confirm the validity of examining both the EEG and fMRI signals on an ST basis and suggest an underlying neuronal origin in both modalities.     

脑干听觉诱发电位波幅声强函数曲线的研究

背景:脑干听觉诱发电位(brainstemauditoryevokedpotential,BAEP)波Ⅴ与波Ⅰ波幅的比值Ⅴ/Ⅰ具有重要的诊断价值,但波幅与声强的关系尚缺乏系统研究。目的:研究BAEP波幅与声强之间的函数关系,得出波Ⅴ与波Ⅰ波幅的比值Ⅴ/Ⅰ测定的合适给声强度范围。设计:以诊断为依据的横断面研究。地点和对象:从菏泽医学专科学校2000级,临床证实无耳疾在校学生中随机选取50人,其中男28人,女22人,平均年龄20岁,进行BAEP测试。干预:使用YJC-A型诱发电位肌电图测试仪依次选用55,75,95,100,105,110,115,120,125dB疏密交替波短声给声刺激,分别测试双耳BAEP。主要观察指标:测定各声强下波Ⅰ、波Ⅲ、波Ⅴ的波幅以及Ⅴ/Ⅰ比值和Ⅴ/Ⅲ比值,并求出相应波幅与声强关系曲线。结果:波幅-声强函数曲线表明:①波Ⅰ、波Ⅲ、波Ⅴ波幅均随声强增大而增大。②波Ⅲ、波Ⅴ曲线陡度在90dB以前较大、90dB以后较平缓;波Ⅰ陡度远大于前者,几乎呈直线上升。③波Ⅲ与波Ⅴ近于平行。④Ⅴ/Ⅰ直线下降,与波Ⅰ几乎成反变关系;Ⅴ/Ⅲ近乎平坦直线。⑤90dB前,Ⅴ/Ⅰ大于1,随声强降低,Ⅴ/Ⅰ迅速增大,远大于1;90dB后,Ⅴ/Ⅰ接近于1,且较稳定。结论:在临床评价Ⅴ/Ⅰ比值结果时,若在<100dB范围内给声刺激易出现假阴性结果,在100～120dB声强范围内选取给声强度进     

Neonatal-onset brainstem reticular reflex myoclonus following a prenatal brain insult: generalized myoclonic jerk and a brainstem lesion

Brainstem reticular reflex myoclonus (BRRM) is characterized by sudden, generalized, shock-like movements that can be elicited by sensory stimulation. We present a boy, born after 35 weeks gestation, who was diagnosed with neonatal-onset BRRM. Within 1 hr of birth, the patient showed spasticity and generalized clonic movements of all limbs elicited with tactile stimulation anywhere on the body. Surface electromyography showed co-contraction of agonistic and antagonistic muscles, revealing that his generalized clonic movements were tremulous myoclonus in nature. Brain magnetic resonance imaging (MRI) at 21 hrs after birth disclosed high-intensity lesions in the Rolandic area, thalamus, basal ganglia, and brainstem, including the dorsal pons and medulla, the center of BRRM, in T1-weighted images. Follow-up MRI at 1 month revealed dramatic improvement in the pontine lesion. The patient showed gradual remission of the characteristic movements, which disappeared at 1 year of age, but the patient died unexpectedly at 1 year and 3 months. In conclusion, neonatal BRRM arises as a result of severe brainstem injury, and the associated lesions may only be seen temporarily on MRI taken soon after birth.     

多频稳态诱发电位与听性脑干反应对成人感音神经性耳聋听阈的评估比较

目的:比较多频稳态诱发电位(ASSR)与短声听性脑干反应(ABR)对成人感音神经性聋患者听阈的评估.方法:对102例成人感音神经性聋患者分别测试ASSR反应阈、ABR反应阈和纯音测听,比较ASSR反应阈和ABR反应阈与纯音听阈的相关性,从而评估二者对行为听阈预测的准确性.结果:ASSR反应阈、ABR反应阈和行为听阈之间均有较高的相关性.二者在高频与行为听阈相关性较接近.但在低频,ASSR的相关性较ABR高.结论:ASSR和ABR均可用作感音神经性聋患者客观听阈的评估,但ASSR较ABR有更大的优势.     

Brain responses to dynamic facial expressions of pain

The facial expression of pain is a prominent non-verbal pain behaviour, unique and distinct from the expression of basic emotions. Yet, little is known about the neurobiological basis for the communication of pain. Here, subjects performed a sex-discrimination task while we investigated neural responses to implicit processing of dynamic visual stimuli of male or female faces displaying pain or angry expressions, matched on expression intensity and compared to neutral expression. Stimuli were presented in a mixed blocked/event-related design while blood oxygenation level dependent (BOLD) signal was acquired using whole-brain functional magnetic resonance imaging (fMRI) at 1.5 Tesla. Comparable sustained responses to pain and angry faces were found in the superior temporal sulcus (STS). Stronger transient activation was also observed to male expression of pain (Vs neutral and anger) in high-order visual areas (STS and fusiform face area) and in emotion-related areas including the amygdala (highest peak t-value=10.8), perigenual anterior cingulate cortex (ACC), and SI. Male pain compared to anger expression also activated the ventromedial prefrontal cortex, SII/posterior insula and anterior insula. This is consistent with the hypothesis that the implicit processing of male pain expression triggers an emotional reaction characterized by a threat-related response. Unexpectedly, several areas responsive to male expression, including the amygdala, perigenual ACC, and somatosensory areas, showed a decrease in activation to female pain faces (Vs neutral). This sharp contrast in the response to male and female faces suggests potential differences in the socio-functional role of pain expression in males and females.     

The diagnosis of brainstem death and its implications

The concept of brainstem death is relatively new and has been developed in response to advances in medical treatment such as mechanical ventilation. The idea that it is the same as death of the whole person has been tested in medical research and legally, which has provided evidence to support the withdrawal of advanced medical treatment and for discussion of organ donation.