Functional MRI of oropharyngeal air-pulse stimulation.

Although the posterior oral cavity and oropharynx play a major role in swallowing, their central representation is poorly understood. High-field functional magnetic resonance imaging of the brain was used to study the central processing of brief air-pulses, delivered to the peritonsillar region of the lateral oropharynx, in six healthy adults. Bilateral air-pulse stimulation was associated with the activation of a bilateral network including the primary somatosensory cortex and the thalamus, classic motor areas (primary motor cortex, supplementary motor area, cingulate motor areas), and polymodal areas (including the insula and frontal cortex). These results suggest that oropharyngeal stimulation can activate a bilaterally distributed cortical network that overlaps cortical regions previously implicated in oral and pharyngeal sensorimotor functions such as tongue movement, mastication, and swallowing. The present study also demonstrates the utility of air-pulse stimulation in investigating oropharyngeal sensorimotor processing in functional brain imaging experiments.

No indication of brain reorganization after unilateral ischemic lesions of the auditory cortex.

We used magnetoencephalography to study contralesional auditory reorganization in three men with chronic unilateral ischemic lesions of the auditory cortex. Although no response was found over the lesioned hemisphere, processing in the unaffected hemisphere was indistinguishable vs healthy controls. In contrast to sensorimotor and language systems, the auditory system seems to lack contralateral reorganization, presumably because patients are typically not aware of hearing deficits and thus do not perform training.

Conjoined lumbosacral nerve roots: current aspects of diagnosis.

Conjoined lumbosacral nerve roots (CLNR) are the most common anomalies involving the lumbar nerve structures which can be one of the origins of failed back syndromes. They can cause sciatica even without the presence of a additional compressive impingement (such as disc herniation, spondylolisthesis or lateral recess stenosis), and often congenital lumbosacral spine anomalies (such as bony defects) are present at the "conjoined sheaths". This congenital anomaly has been reported in 14% of cadaver studies, but myelographic or computed tomographic studies have revealed an incidence of approximately 4% only. Diagnostic methods such as magnetic resonance imaging (MRI) are helpful for determination of the exact anatomical relations in this context. We present five typical cases of conjoined nerve roots observed during a 1 year period, equivalent to 6% of our out-patients without a history of surgical treatment on the lumbar spine. In all cases with suspicious radiological findings MRI or lumbar myelography combined with CT and multiplanar reconstructions is recommended.

[Phantom pain after eye enucleation]. / Phantomschmerz nach Enucleatio bulbi.

BACKGROUND: Phantom pain is a well known and extensively documented complication after limb amputation. Nearly all surgical disciplines have to deal with phantom symptoms related to different anatomical regions and organs but limited data is available about phantom eye pain (PEP) after enucleation. Only one pilot study is present in literature. It was the aim of this study to analyze a group of patients with a standardized surgical procedure of enucleation concerning the incidence of PEP and its relation to further preoperative and postoperative data. PATIENTS AND METHODS: A standardized questionnaire was sent to all enucleation patients with primary orbital implant performed between 1/1/1986 and 12/31/1995 at Münster University. Data of 94 patients could be analyzed with regard to PEP, perioperative pain symptoms and further ophthalmological and surgical data. RESULTS: 24 of 94 patients reported PEP after enucleation. The frequency of PEP was less than once per month in the majority of patients (71%). 2 of 24 patients suffered from PEP on more than 4 days/month. Perioperative pain symptoms (ocular pain [OP], preoperative and postoperative headache) were reported with a higher proportion (each p<0.0025) in patients with PEP compared to those not affected by PEP. All patients with a preoperative history of OP longer than 5 years and 75% of patients with OP longer than 12 months of pre-enucleation OP were affected by PEP. CONCLUSIONS: Phantom eye pain is present in nearly 1/4 of patients after enucleation and is significantly related to other perioperative pain symptoms.

Neuroimaging evidence for cortical involvement in the preparation and in the act of swallowing.

This study employed whole head magnetoencephalography and synthetic aperture magnetometry to investigate the cortical topography of the preparation and the execution of volitional and reflexive water swallowing and of a simple tongue movement. Concerning movement execution, activation of the mid-lateral primary sensorimotor cortex was strongly lateralized to the left during volitional water swallowing, less strongly lateralized to the left during reflexive water swallowing, and not lateralized at all during tongue movement. In contrast, the preparation for both volitional water swallowing and tongue movement showed a bilateral activation of the primary sensorimotor cortex. No activation was seen prior to reflexive water swallowing. Activation of the left insula and frontal operculum was observed only during both the preparation and the execution of volitional water swallowing. These new findings suggest a left hemispheric dominance for the cortical control of swallowing in humans.

Phantom eye syndrome: Its prevalence, phenomenology, and putative mechanisms.

This study presents data on the clinical characteristics and possible mechanisms of the phantom eye syndrome in 112 patients after removal of one eye. The prevalence of phantom eye pain was 26%, nonpainful phantom sensations 29%, and visual hallucinations 31%. Headaches and preoperative eye pain were associated with the presence of phantom experiences. These results suggest that pain is an important cofactor for the development of phantom eye phenomena.

Axonal polyneuropathy in obstructive sleep apnoea.

Chronic hypoxaemia in chronic obstructive pulmonary disease is a well known risk factor for polyneuropathy but the impact of intermittent hypoxaemia on peripheral nerve function has not been established so far. A case-control study was performed to evaluate the prevalence of polyneuropathy in obstructive sleep apnoea (OSA). Out of 24 patients with OSA, 17 (71%) had clinical signs of polyneuropathy versus seven (33%) out of 21 matched controls. The mean amplitude of the sural sensory nerve action potential was smaller in the OSA group than in the control group, indicating axonal nerve damage. The differences were significant and could not be attributed to other known risk factors for polyneuropathy. The severity of axonal damage in patients with OSA correlated with the percentage of the night time with an O(2) saturation below 90%. It is assumed that recurrent intermittent hypoxaemia in OSA is an independent risk factor for axonal damage of peripheral nerves.

Functional reorganization of the human primary somatosensory cortex after acute pain demonstrated by magnetoencephalography.

The somatosensory system is capable of functional reorganization following peripheral denervation or training. Studies on human amputees with phantom limb pain provided evidence that these reorganizational changes are modulated through nociceptive input. In the present study we used magnetoencephalographic recordings of six healthy volunteers to assess whether acute pain by itself causes a reorganization of the primary somatosensory cortex. After the induction of an intense experimental pain at the thenar of the left hand by intradermal injection of capsaicin, the extent of the cortical hand representation and the distance between the hand representation and the localization of the lip decreased. A likely mechanism for this acute reorganization is that pain induced hyperresponsiveness of the left thenar to tactile input from neighboring body sites.

Time course of focal slow wave activity in transient ischemic attacks and transient global amnesia as measured by magnetoencephalography.

In this longitudinal study multichannel MEG was used to localize and to quantify focal pathological spontaneous neuromagnetic activity in six patients with transient ischemic attacks (TIA) and two patients with transient global amnesia (TGA). Slow (2-6 Hz) and beta (14-30 Hz) activity were monitored up to 10 weeks. Results were compared with normative data, and changes over time were statistically analyzed. MEG detected pathological activity that persisted clinical symptoms. Focal slow activity originating from sensorimotor (TIA) and mesiotemporal (TGA) cortices exceeded normal values up to 14 times during the first hours after the attack and recovered to normal within 11 days. Focal beta activity was not useful to monitor the time course of TIA or TGA.

Cortical asymmetries of the human somatosensory hand representation in right- and left-handers.

Hemispheric asymmetry is known for higher brain functions like language and attention. We tested whether such an asymmetry also exists in the representation of elementary sensory functions. Magnetic source imaging was used to compare the cortical somatosensory hand representation in seven right- and five left-handed individuals. In all right-handers the representation of the dominant hand was larger than the contralateral one in the corresponding hemispheres. In contrast, only two out of five left-handers revealed a larger representation of the dominant left hand compared to the right one. In agreement with previous findings on the lateralization of language and attention, there is a strong correlation between handedness and the extent of the cortical hand representation in right-, but not in left-handers. We conclude that a profound functional hemispheric asymmetry also exists in primary sensory cortices.

Focal slow and beta brain activity in patients with multiple sclerosis revealed by magnetoencephalography.

In multiple sclerosis (MS) inflammatory infiltrations cause white matter lesions. Magnetoencephalography (MEG) offers the opportunity to localize abnormal electric activity of neurons with a high spatio-temporal resolution. In this study, we investigated patients with MS in order to find if abnormal cortical activity is associated with (subcortical) MS lesions using simultaneous bilateral recording of biomagnetic activity. Eight patients suffering from definite laboratory-supported MS with mainly somatosensory deficits and multiple bihemispheric plaques revealed by MRI were included in the study. To obtain normative data, 8 healthy volunteers were investigated following the same measuring protocol. Spontaneous magnetic brain activity was recorded using a 2x37-channel biomagnetic system (BTI, USA). Offline analysis included digital filtering (to separately investigate slow and beta wave activity), a Principle Component Analysis and the Dipole Density Plot. Localization results were inserted into MR images using our contour fit procedure. The dipole distribution in the brain was quantified and compared between the groups by statistical analysis. In all MS patients, the maximum of focal abnormal activity was localized in cortical areas adjacent to the fiber lesions. In the healthy subjects, no focal abnormal brain activity could be found. However, the standardized maximum concentrations of dipoles were significantly higher in the MS patients than in the healthy control group both in the slow and in the beta wave analysis. These results let assume that subcortical lesions can occur together with abnormal cortical neuronal activity. The results are discussed in respect to their impact on the interpretation of the analysis of spontaneous magnetic brain activity.

Lipoprotein-X in patients with cirrhosis: its relationship to cholestasis and hypercholesterolemia.

Lipoprotein-X (Lp-X) is an abnormal low-density lipoprotein frequently found in liver disease. It is regarded as the most sensitive and specific biochemical parameter for the diagnosis of intra- and extrahepatic cholestasis. Moreover, Lp-X is supposed to contribute to the development of hypercholesterolemia in cholestatic liver disease, because it fails to inhibit de novo cholesterol synthesis. This investigation will focus on the relationship between the presence of Lp-X and serum lipid concentrations in cirrhosis. The significance of Lp-X in the diagnosis of cholestasis, compared with alkaline phosphatase (AP), gamma-glutamyl transferase (GGT), and bilirubin levels, will be assessed as well. The present cross-sectional study includes 212 patients with histopathologically proven cirrhosis. The detection of Lp-X and the quantification of -, beta-, and pre-beta-cholesterol was based on agar gel electrophoresis and polyanion precipitation. For the characterization of liver function, the concentrations of albumin and bilirubin, the activities of liver enzymes, and coagulation times were assessed. In a subgroup of 40 individuals, liver biopsies were re-evaluated to confirm or exclude intrahepatic cholestasis. As a result, there was no association between the appearance of Lp-X and total cholesterol concentrations. While all patients with Lp-X showed intrahepatic cholestasis (predictive value of the positive test = 1), only 16 of 28 patients with cholestasis formed Lp-X (sensitivity = 0.57). The activities of AP and of GGT, as well as the concentrations of bilirubin, were strongly elevated in most patients, with and without cholestasis. The predictive values of AP, GGT, and bilirubin were 0.77, 0.69, and 0.74 for the positive test and 0.5, 0, and 0.6 for the negative test, respectively. We conclude that Lp-X is not related to hypercholesterolemia in cirrhosis. The positive, but not the negative, Lp-X test has high predictive value for the diagnosis of cholestasis in cirrhosis. The biochemical parameters traditionally used for the assessment of extrahepatic cholestasis, AP, GGT, and bilirubin, do not support the diagnosis of intrahepatic cholestasis caused by cirrhosis.

Motor, somatosensory and auditory cortex localization by fMRI and MEG.

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) were performed in six subjects during self-paced finger movement performance, tactile somatosensory stimulation and binaural auditory stimulation using identical stimulation paradigms. Both functional imaging modalities localized brain activity in adjacent areas of anatomically correct cortex. The mean distances measured between fMRI activity and the corresponding MEG dipoles were 10.1 mm (motor), 10.7 mm (somatosensory), 13.5 mm (auditory right hemisphere) and 14.3 mm (auditory left hemisphere). The distances found may reflect the correlation between electrophysiological and hemodynamic responses due to the different underlying substrates of neurophysiology measured by fMRI and MEG: BOLD contrast vs neuronal biomagnetic activity.

Peripheral autonomic potentials in primary headache and drug-induced headache.

Autonomic functions of different primary headache types have been investigated in several studies, most of them analyzing cardiovascular reflex mechanisms or biochemical changes. The results are contradictory; only in tension-type headache and in cluster headache has a sympathetic hypofunction been shown in a preponderance of studies. We analyzed the peripheral autonomous potentials (PAPs) in different primary headache types and in drug-induced headache and compared the results with those of healthy subjects and of patients with low back pain. Latencies of PAPs were significantly increased in all headache types but not in low back pain; amplitudes of PAPs did not show significant differences compared to healthy subjects. Patients with a long duration of drug abuse had increased PAP latencies, whereas patients with a high number of migraine attacks per year had decreased latencies. Our data suggest that sympathetic hypofunction as measured by PAP latencies is a general phenomenon in headache but not in all pain syndromes. Drug abuse leads to an increase of this hypofunction. While measuring PAPs is not an appropriate method by which to differentiate between headache disorders, it allows assessment of autonomic disturbances in primary and drug-induced headache.

Prostaglandin analog mechanisms are not effective in refractory chronic cluster headache.

Prostaglandin E analogs have been shown to be effective in the treatment of refractory trigeminal neuralgia in patients with multiple sclerosis. Prostaglandin E inhibits the functions of T lymphocytes which are involved in the pathophysiology of cluster headache. Therefore, a double-blind, placebo-controlled, crossover study on the efficacy of misoprostol in chronic refractory cluster headache was performed. Eight patients were treated with 600 micrograms misoprostol and with placebo for a 2-week period. No differences in attack frequency, intensity, global impression, and side effects could be detected, suggesting that prostaglandin E analogs are not effective in the treatment of chronic cluster headache.

Cluster headache after orbital exenteration.

A 37-year-old man developed an ipsilateral headache which fulfilled the criteria for cluster headache after orbital extenteration because of a traumatic lesion of the bulb. The headache could be treated successfully by drugs usually applied in the therapy of cluster headache. Six similar cases of cluster headache after orbital exenteration could be identified in the literature suggesting that the eye itself is not necessarily part of the pathogenesis of cluster headache. We hypothesize that orbital exenteration can cause cluster headache by lesions of sympathetic structures. Possibly, these mechanisms are similar to those of sympathetic reflex dystrophy (Sudeck-Leriche syndrome) causing pain of the limbs.