Effects of ventral intermediate nucleus deep brain stimulation across multiple effectors in essential tremor

OBJECTIVE

Essential tremor (ET) prominently affects the upper-limbs during voluntary movements, but can also affect the lower-limbs, head, and chin. Although deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of thalamus improves both clinical ratings and quantitative measures of tremor, no study has quantified effects of DBS on tremor across multiple body parts. Our objective was to quantify therapeutic effects of DBS across multiple body parts in ET.

METHODS

We performed quantitative assessment of tremor in ET patients who had DBS for at least one year. We assessed tremor on and off VIM-stimulation using triaxial accelerometers on the upper-limbs, lower-limbs, head and chin during seated and standing tasks.

RESULTS

VIM-DBS significantly reduced tremor, but there was no statistical difference in degree of tremor reduction across the measured effectors. Compared to healthy controls, ET patients treated with DBS showed significantly greater tremor power (4-8 Hz) across all effectors during seated and standing tasks.

CONCLUSIONS

VIM-DBS reduced tremor in ET patients. There was no significant difference in the degree of tremor reduction across the measured effectors.

SIGNIFICANCE

This study provides new quantitative evidence that VIM-DBS is effective at reducing tremor across multiple parts of the body.

Long-term outcome of acute encephalitis of unknown aetiology in adults

Encephalitis is caused by a variety of conditions, including infections of the brain by a wide range of pathogens. A substantial number of cases of encephalitis defy all attempts at identifying a specific cause. Little is known about the long-term prognosis in patients with encephalitis of unknown aetiology, which complicates their management during the acute illness. To learn more about the prognosis of patients with encephalitis of unknown aetiology, patients in whom no aetiology could be identified were examined in a large, single-centre encephalitis cohort. In addition to analysing the clinical data of the acute illness, surviving patients were assessed by telephone interview a minimum of 2 years after the acute illness by applying a standardized test battery. Of the patients with encephalitis who qualified for inclusion (n = 203), 39 patients (19.2%) had encephalitis of unknown aetiology. The case fatality in these patients was 12.8%. Among the survivors, 53% suffered from various neurological sequelae, most often attention and sensory deficits. Among the features at presentation that were associated with adverse outcome were older age, increased C-reactive protein, coma and a high percentage of polymorphonuclear cells in the cerebrospinal fluid. In conclusion, the outcome in an unselected cohort of patients with encephalitis of unknown aetiology was marked by substantial case fatality and by long-term neurological deficits in approximately one-half of the surviving patients. Certain features on admission predicted an unfavourable outcome.

Acute fluid ingestion in the treatment of orthostatic intolerance - important implications for daily practice

BACKGROUND

Rapid water ingestion improves orthostatic intolerance (OI) in multiple system atrophy (MSA) and postural tachycardia syndrome (PoTS). We compared haemodynamic changes after water and clear soup intake, the latter being a common treatment strategy for OI in daily practice.

METHODS

Seven MSA and seven PoTS patients underwent head-up tilt (HUT) without fluid intake and 30 min after drinking 450 ml of water and clear soup, respectively. All patients suffered from moderate to severe OI because of neurogenic orthostatic hypotension (OH) and excessive orthostatic heart rate (HR) increase, respectively. Beat-to-beat cardiovascular indices were measured non-invasively.

RESULTS

In MSA, HUT had to be terminated prematurely in 2/7 patients after water, but in 6/7 after clear soup. At 3 min of HUT, there was an increase in blood pressure of 15.7(8.2)/8.3(2.3) mmHg after water, but a decrease of 11.6(18.9)/8.1(9.2) mmHg after clear soup (P < 0.05). In PoTS, HUT could always be completed for 10 min, but OI subjectively improved after both water and clear soup. The attenuation of excessive orthostatic HR increase did not differ significantly after water and clear soup drinking.

CONCLUSIONS

In MSA, clear soup cannot substitute water for eliciting a pressor effect, but even worsens OI after rapid ingestion. In PoTS, acute water and clear soup intake both result in improvement of OI. These findings cannot solely be explained by difference in osmolarity but may reflect some degree of superimposed postprandial hypotension in widespread autonomic failure in MSA compared to the mild and limited autonomic dysfunction in PoTS.

Horizontal and vertical dimensions of visual extinction: a theta burst stimulation study

After a lesion of the posterior parietal cortex (PPC), the perception of a contra-lesional stimulus in presence of a simultaneous, ipsilesional stimulus may be impaired, a phenomenon referred to as visual extinction. In the present study, visual extinction was transiently induced in healthy subjects by interfering with the function of the right PPC by means of continuous theta burst stimulation (TBS). We investigated to which extent the horizontal and vertical position of visual stimuli influenced the extinction rate. A single TBS train over the right PPC induced a significant increase of left visual extinctions of at least 30 min. Left visual extinction rate was higher when the left sided visual stimulus was presented at a more eccentric position on the horizontal axis (irrespective of right sided visual stimulus position) and in the lower part of the visual field. The results are discussed within the framework of current explanatory models and of putative inter- and intrahemispheric mechanisms directing visuospatial attention.

Mapping of direction and muscle representation in the human primary motor cortex controlling thumb movements

Larger body parts are somatotopically represented in the primary motor cortex (M1), while smaller body parts, such as the fingers, have partially overlapping representations. The principles that govern the overlapping organization of M1 remain unclear. We used transcranial magnetic stimulation (TMS) to examine the cortical encoding of thumb movements in M1 of healthy humans. We performed M1 mapping of the probability of inducing a thumb movement in a particular direction and used low intensity TMS to disturb a voluntary thumb movement in the same direction during a reaction time task. With both techniques we found spatially segregated representations of the direction of TMS-induced thumb movements, thumb flexion and extension being best separated. Furthermore, the cortical regions corresponding to activation of a thumb muscle differ, depending on whether the muscle functions as agonist or as antagonist for flexion or extension. In addition, we found in the reaction time experiment that the direction of a movement is processed in M1 before the muscles participating in it are activated. It thus appears that one of the organizing principles for the human corticospinal motor system is based on a spatially segregated representation of movement directions and that the representation of individual somatic structures, such as the hand muscles, overlap.

Sleepiness and vigilance tests

Objective assessments of subjective complaints such as sleepiness, tiredness or fatigue using sleepiness and vigilance tests aim to identify its causes and to judge the fitness to drive or to work of the affected person. "Vigilance" comprises wakefulness, alertness and attention and is therefore not merely reciprocal to sleepiness. Since it is a complex phenomenon with several dimensions it is unlikely to be appropriately assessed by one single "vigilance test". One important dimension of vigilance discussed here is wakefulness with its counterpart of overt sleep and the whole spectrum of various levels in between. The transit zone between full wakefulness and overt sleep is mainly characterised by the subjective complaint of sleepiness, which cannot be measured directly. Only the consequences of reduced wakefulness such as a shortened sleep latency, slowed cognitive function and prolonged reaction time can be measured objectively. It is, therefore, more promising to combine a battery of subjective and objective tests to answer a specific question in order to achieve the most appropriate description for a given clinical or medicolegal situation. However even then we must keep in mind that many other important aspects of fitness to drive / fitness to work such as neurological, psychiatric and neuropsychological functions including risk taking behaviour are not covered by vigilance tests. A comprehensive, multidisciplinary approach is essential in such situations.

Loss of exploratory vertical saccades after unilateral frontal eye field damage

Despite their relevance for locomotion and social interaction in everyday situations, little is known about the cortical control of vertical saccades in humans. Results from microstimulation studies indicate that both frontal eye fields (FEFs) contribute to these eye movements. Here, we present a patient with a damaged right FEF, who hardly made vertical saccades during visual exploration. This finding suggests that, for the cortical control of exploratory vertical saccades, integrity of both FEFs is indeed important.

Time course of blood oxygenation level-dependent signal response after theta burst transcranial magnetic stimulation of the frontal eye field

The aim of the current study was to examine the effect of theta burst repetitive transcranial magnetic stimulation (rTMS) on the blood oxygenation level-dependent (BOLD) activation during repeated functional magnetic resonance imaging (fMRI) measurements. Theta burst rTMS was applied over the right frontal eye field in seven healthy subjects. Subsequently, repeated fMRI measurements were performed during a saccade-fixation task (block design) 5, 20, 35, and 60 min after stimulation. We found that theta burst rTMS induced a strong and long-lasting decrease of the BOLD signal response of the stimulated frontal eye field at 20 and 35 min. Furthermore, less pronounced alterations of the BOLD signal response with different dynamics were found for remote oculomotor areas such as the left frontal eye field, the pre-supplementary eye field, the supplementary eye field, and both parietal eye fields. Recovery of the BOLD signal changes in the anterior remote areas started earlier than in the posterior remote areas. These results show that a) the major inhibitory impact of theta burst rTMS occurs directly in the stimulated area itself, and that b) a lower effect on remote, oculomotor areas can be induced.

Isolated mediotegmental lesion causing narcolepsy and rapid eye movement sleep behaviour disorder: a case evidencing a common pathway in narcolepsy and rapid eye movement sleep behaviour disorder

Narcolepsy is usually an idiopathic disorder, often with a genetic predisposition. Symptomatic cases have been described repeatedly, often as a consequence of hypothalamic lesions. Conversely, REM (rapid eye movement) sleep behaviour disorder (RBD) is usually a secondary disorder, often due to degenerative brain stem disorders or narcolepsy. The case of a hitherto healthy man is presented, who simultaneously developed narcolepsy and RBD as the result of an acute focal inflammatory lesion in the dorsomedial pontine tegmentum in the presence of normal cerebrospinal fluid hypocretin-1 levels and in the absence of human lymphocyte antigen haplotypes typically associated with narcolepsy and RBD (DQB1*0602, DQB1*05). This first observation of symptomatic narcolepsy with RBD underlines the importance of the mediotegmental pontine area in the pathophysiology of both disorders, even in the absence of a detectable hypocretin deficiency and a genetic predisposition.

Myoclonus-dystonia, obsessive-compulsive disorder, and alcohol dependence in SGCE mutation carriers

Although myoclonus and dystonia are the hallmarks of myoclonus-dystonia (M-D), psychiatric features, particularly obsessive-compulsive disorder and alcohol dependence, have been reported in three families linked to chromosome 7q21. As the epsilon sarcoglycan (SGCE) gene for M-D was subsequently identified, we evaluated the relationship between psychiatric features and SGCE mutations in these original and two additional families and confirm that OCD and alcohol dependence are associated with manifesting mutated SGCE.

[Non-traumatic acute transverse spinal cord syndromes]

Differential diagnosis of non-traumatic, acute transverse spinal cord syndromes should cover compressive myelopathy (mostly hematomas or tumors), inflammatory myelitis and vascular myelopathies. Since acute pathologies of the spinal cord primarily result in flaccid para- or tetraparesis accompanied by areflexia or hyporeflexia (spinal shock), acute polyradiculoneuritis and the cauda equina syndrome must also be weighed into the differential diagnosis. Paraplegia may ultimately also be of psychogenic origin. The clinical picture is characterized by the rapidity of progression, the possible involvement of pain, and the specific pattern of the deficits. When the latter occurs, localization of the rostrocaudal level and transverse spread are crucial factors. Depending on the affected structure, one differentiates between anterior spinal cord syndromes (anterior spinal artery syndrome, selective involvement of the anterior horn, centromedullary syndromes), long pathway syndrome (isolated in the posterior bundle or combined with pyramidal pathways) and the unilateral Brown-Séquard's syndrome. Infectious myelitis is usually caused by neurotropic viruses or mycoplasmata in conjunction with meningitis or encephalitis; these in turn either induce transverse myelitis accompanied by severe sensomotor deficits or chiefly affect the gray matter, then producing a pattern similar to anterior spinal artery syndrome. In the case of non-infectious inflammatory myelitis, one must differentiate between multiple sclerosis, acute disseminated encephalomyelitis (ADEM), idiopathic transverse myelitis and that of the neuromyelitis optica or Devic's disease. Symptomatic transverse myelitis can also be present in association with connective tissue diseases (e.g. SLE, Behçet's disease, Sjögren's syndrome) or sarcoidosis. Notably, when ischemic spinal infarcts are involved, their onset is frequently painful and their manifestation typically subacute, rather than apoplectiform.

Visual exploration behaviour during clock reading in Alzheimer's disease

Eye movement behaviour during visual exploration of 24 patients with probable Alzheimer's disease and 24 age-matched controls was compared in a clock reading task. Controls were found to focus exploration on distinct areas at the end of each clock hand. The sum of these two areas of highest fixation density was defined as the informative region of interest (ROI). In Alzheimer's disease patients, visual exploration was less focused, with fewer fixations inside the ROI, and the time until the first fixation was inside the ROI was significantly delayed. Changes of fixation distribution correlated significantly with the ability to read the clock correctly, but did not correlate with dementia severity. In Alzheimer's disease patients, fixations were longer and saccade amplitudes were smaller. The altered visual exploration in Alzheimer's disease might be related to parietal dysfunction or to an imbalance between a degraded occipito-parietal and relatively preserved occipito-temporal visual network.

Central motor conduction differs between acute relapsing–remitting and chronic progressive multiple sclerosis

OBJECTIVE

To characterize central motor conduction in relation to the clinical deficits and to the disease duration in 90 patients with acute relapsing-remitting MS (RR-MS) and in 51 patients with chronic primary or secondary progressive MS (P-MS).

METHODS

The triple stimulation technique (TST) was used to quantify the central motor conduction failure (expressed by the TST amplitude ratio) and conventional motor evoked potentials (MEPs) were used to measure the central motor conduction time (CMCT).

RESULTS

The TST amplitude ratio was reduced in presence of a clinical motor deficit (p=0.02 for RR-MS, p<0.01 for P-MS), but did not significantly differ in RR-MS and P-MS (p>0.05) when patients with similar clinical motor deficit were compared. The CMCT was not related to the clinical motor deficit in both RR-MS and P-MS. However, the CMCT was markedly prolonged in P-MS, when patients with similar clinical motor deficit and with similar disease duration were compared (p<0.01). The differences were not attributable to differential involvement of the spinal cord, which was similar in RR-MS and P-MS.

CONCLUSIONS

Our results disclose differences between the central motor conduction in RR-MS and P-MS that are not related to disease severity, spinal cord involvement or disease duration.

Hemispheric asymmetry in visuospatial attention assessed with transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) was used to study visuospatial attention processing in ten healthy volunteers. In a forced choice recognition task the subjects were confronted with two symbols simultaneously presented during 120 ms at random positions, one in the left and the other in the right visual field. The subject had to identify the presented pattern out of four possible combinations and to press the corresponding response key within 2 s. Double-pulse TMS (dTMS) with a 100-ms interstimulus interval (ISI) and an intensity of 80% of the stimulator output (corresponding to 110-120% of the motor threshold) was applied by a non-focal coil over the right or left posterior parietal cortex (PPC, corresponding to P3/P4 of the international 10-20 system) at different time intervals after onset of the visual stimulus (starting at 120 ms, 270 ms and 520 ms). Double-pulse TMS over the right PPC starting at 270 ms led to a significant increase in percentage of errors in the contralateral, left visual field (median: 23% with TMS vs 13% without TMS, P=0.0025). TMS applied earlier or later showed no effect. Furthermore, no significant increase in contra- or ipsilateral percentage of errors was found when the left parietal cortex was stimulated with the same timing. These data indicate that: (1) parietal influence on visuospatial attention is mainly controlled by the right lobe since the same stimulation over the left parietal cortex had no significant effect, and (2) there is a vulnerable time window to disturb this cortical process, since dTMS had a significant effect on the percentage of errors in the contralateral visual hemifield only when applied 270 ms after visual stimulus presentation.

Motor evoked potentials from masseter muscle induced by transcranial magnetic stimulation of the pyramidal tract: the importance of coil orientation

BACKGROUND

Reliable recording of motor evoked potentials (MEPs) of the masseter muscle by transcranial magnetic stimulation (TMS) has proved more difficult than from facial or intrinsic hand muscles. Up to now it was unclear whether this difficulty was due to methodological and/or anatomical reasons.

METHODS

The mechanism of pyramidal cell activation in masseter MEPs was investigated by using magnetic and electric transcranial stimulation. Analysing the effect of magnetic coil positioning and orientation over the scalp, and scrutinizing the masseter recording technique to avoid compound motor action potential (CMAP) contamination from facial muscles, an optimized method of masseter MEPs was developed.

RESULTS

In particular, an antero-lateral inducing current orientation in the stimulating coil, approximately paralleling the central sulcus, proved clearly more effective for the masseter muscles than the postero-lateral orientation (P=0.005) found optimal for intrinsic hand muscles. The thus evoked masseter MEPs by transcranial magnetic stimulation (TMS) were found to be identical in shape, amplitude and latency as those evoked by transcranial electric stimulation (TES), evidencing a direct rather than trans-synaptic activation of the pyramidal cells.

CONCLUSIONS

We conclude that in TMS evoked MEPs of masseter muscles, the direct stimulation of the pyramidal tract is more easily achieved than the trans-synaptic activation, which is in contrast to the intrinsic hand muscles. We hypothesize that the presynaptic projections to pyramidal cells of the masticatory muscles are less abundant than in hand muscles, and are therefore less accessible to trans-synaptic stimulation.

Double-pulse transcranial magnetic stimulation over the frontal eye field facilitates triggering of memory-guided saccades

The study investigated the influence of double-pulse transcranial magnetic stimulation (dTMS) on memory-guided saccade triggering. Double pulses with interstimulus intervals (ISIs) of 35, 50, 65 or 80 ms were applied over the right frontal eye field (FEF) and as control over the occipital cortex. A significant dTMS effect was found exclusively for contralateral saccades; latency of memory-guided saccades was reduced after FEF stimulation with an ISI of 50 ms compared to latency without stimulation. This effect proved to be specific for the ISI of 50 ms over the FEF because control stimulation with the same ISI over the occipital cortex had no significant effect on latency of memory-guided saccades. The results of our study showed that, by using an appropriate ISI, dTMS is able to facilitate contralateral saccade triggering by stimulating the FEF. This suggests that TMS interferes specifically with saccade triggering mechanisms, probably by acting on presaccadic neurons of the FEF.

Restless legs syndrome: a clinical study of 55 patients

BACKGROUND

Restless legs syndrome (RLS) is a common sleep disorder. In 1995, clinical criteria for the diagnosis of RLS were defined.

OBJECTIVE

To describe the clinical spectrum in a series of unselected RLS patients meeting the new diagnostic criteria.

METHODS

We prospectively assessed by questionnaire and clinical assessment the characteristics of 55 consecutive RLS patients (35 women, 20 men; mean age = 62 +/- 16 years).

RESULTS

In 27% of the patients, RLS started before the age of 20 years (early-onset RLS). Sensory disturbances were painful in 56% of patients and felt in legs (98%), arms (35%), and 'internally' (45%). Motor disturbances included 'dyskinesias while awake' (36%). Insomnia (58%) was commoner than hypersomnia (24%). In 67% of the patients, no etiology of RLS was found (idiopathic RLS). Early-onset RLS was more commonly familial (p = 0.01) and associated with 'growing pains' (p = 0.005) than late-onset RLS. Patients with RLS and hypersomnia were younger (p = 0.01) and less commonly had painful sensations (p = 0.04) than patients with RLS and insomnia. Patients with idiopathic RLS were younger (p = 0.004), and less commonly had insomnia (p = 0.01) than patients with symptomatic RLS.

CONCLUSIONS

RLS is a clinically pleomorphic syndrome, reflecting the contribution of multiple genetic and acquired factors in the pathogenesis of RLS.

Different ipsilateral representations for distal and proximal movements in the sensorimotor cortex: activation and deactivation patterns

Each hemisphere is known to be also involved in controlling the ipsilateral arm, but with an asymmetry favoring the dominant hemisphere. However, the relative role of primary and secondary motor areas in ipsilateral control is not well defined. We used whole brain functional magnetic resonance imaging in healthy human subjects to differentiate between contributions from primary and secondary areas during discrete unilateral distal finger and proximal shoulder movements. It was found that ipsilateral distal movements activated secondary areas only, while sparing or even significantly deactivating the primary sensorimotor cortex. Ipsilateral proximal movements substantially activated both SM1 and secondary areas. A newly defined small territory within the precentral gyrus, extending from the premotor cortex and intruding toward SM1, showed an activation pattern corresponding to secondary motor areas. Finally, the effects of hemispheric dominance were confirmed, but attributed exclusively to secondary areas. These new imaging findings agree well with functional requirements as well as established anatomical and neurophysiological data.

The triple stimulation technique to study central motor conduction to the lower limbs

OBJECTIVE

To quantify the percentage of motor units of a foot muscle that can be activated by transcranial magnetic stimulation (TMS) in normal subjects and patients.

METHODS

We adapted the recently described triple stimulation technique (TST) for recordings from abductor hallucis (AH). Conventional motor evoked potentials (MEPs) of this muscle are usually small and variable in shape, because of an important temporal desynchronization of the TMS induced spinal motor neuron discharges. The TST allows 'resynchronization' of these discharges and thereby a quantification of the proportion of motor units activated by TMS. The lower limb (LL-) TST was applied to 33 sides of 18 normal subjects and 51 sides of 46 patients with multiple sclerosis, amyotrophic lateral sclerosis, or spinal cord disorders.

RESULTS

In healthy subjects, the LL-TST demonstrated that TMS achieves activation of virtually all motor neurons supplying the AH. In 33 of 51 patient sides, abnormal LL-TST responses suggested corticospinal conduction failures of various degrees. The LL-TST was 2.54 times more sensitive to detect central conduction failures than the conventional LL-MEPs. Combining the LL-TST with TST of the upper limbs further increased the sensitivity to detect a conduction failure by 1.50 times.

CONCLUSION

The LL-TST markedly improves the examination of corticospinal pathways.

Quantification of upper motor neuron loss in amyotrophic lateral sclerosis

OBJECTIVE

To quantitatively estimate upper motor neuron (UMN) loss in ALS.

METHODS

We used the recently developed triple stimulation technique (TST) to study corticospinal conduction to 86 abductor digiti minimi muscles of 48 ALS patients. This method employs a collision technique to estimate the proportion of motor units activated by a transcranial magnetic stimulus. At the same time, it yields an estimate of lower motor neuron (LMN) integrity.

RESULTS

The TST disclosed and quantified central conduction failures attributable to UMN loss in 38 sides of 24 patients (subclinical in 15 sides), whereas conventional motor evoked potentials detected abnormalities in only 18 sides of 12 patients (subclinical in two sides). The increased sensitivity of the TST to detect UMN dysfunction was particularly observed in early cases. Increased central motor conduction times (CMCT) occurred exclusively in sides with conduction failure. In sides with clinical UMN syndromes, the TST response size (but not the CMCT) correlated with the muscle weakness. In sides with clinical LMN syndromes, the size of the peripherally evoked compound muscle action potentials correlated with the muscle weakness.

CONCLUSION

The TST is a sensitive method to detect UMN dysfunction in ALS. It allows a quantitative estimate of the UMN loss, which is related to the functional deficit. Therefore, the TST has a considerable impact on diagnostic certainty in many patients. It will be suited to follow the disease progression and therapeutic trials.

Polyneuropathy attributes: a comparison between patients with anti-MAG and anti-sulfatide antibodies

Thirty-two patients with a peripheral neuropathy and paraproteinemia were tested for IgM antibodies against myelin-associated protein (MAG) and sulfatide by means of enzyme-linked immunosorbent assay. Nine patients (28 %) had increased anti-sulfatide IgM antibodies and showed a chronic, slowly progressive, distally pronounced, and symmetric polyneuropathy with sensory to sensory-motor impairment, ataxia, hyporeflexia, and axonal involvement in electrophysiological studies. Ten patients (31 %) with increased anti-MAG antibodies had a similar, homogeneous polyneuropathy syndrome but presented with demyelinating features. A weak cross-reactivity between anti-MAG and anti-sulfatide antibodies was present in only three patients. In conclusion, although the two neuropathy groups clearly differed in their electrophysiological features, their clinical presentation was rather similar.

Hemispheric asymmetry in cortical control of memory-guided saccades. A transcranial magnetic stimulation study

To study the temporal organisation of memory-guided saccade control we used single-pulse transcranial magnetic stimulation (TMS) over the left posterior parietal (PPC) and prefrontal cortex (PFC) in eight healthy subjects. TMS was applied either following presentation of a visual target, i.e. 160, 260, and 360 ms after the flashed point, or during the period of memorisation, i.e. between 700 and 1500 ms, or finally 100 ms after extinguishing of the central fixation point (i.e. 2100 ms after the target presentation). Latency of memory-guided saccades and the percentage of error in amplitude (PEA) was measured and compared with results without stimulation.TMS over the left PPC 100 ms after the extinguishing of the central fixation point significantly increased memory-guided saccade latency bilaterally. Furthermore, stimulation over the left PFC had a significant effect on the PEA of contralateral memory-guided saccades when applied during the period of memorisation, i.e. between 700 and 1500 ms.In a previous study using identical methodology [13: Müri RM, Vermersch SI, Rivaud S, Gaymard B, Pierrot-Deseilligny C. Effects of single-pulse transcranial magnetic stimulation over the prefrontal and posterior parietal cortices during memory-guided saccades in humans. Journal of Neurophysiology 1996;76:2102-2106], we found that TMS over the right PPC increased the contralateral PEA when applied 260 ms after the flash, the effects on saccade latency after right PPC stimulation or on the PEA after right PFC stimulation being similar to those observed here. Taken together, these results show that (1) a hemispheric asymmetry in the preparation of memory-guided saccade amplitude during the early phase of sensorimotor integration exists, (2) memory-guided saccade triggering is controlled by PPC on both sides, and (3) PFC on both sides are involved in spatial working memory performance.

Primary open-angle glaucoma is associated with sleep apnea syndrome

INTRODUCTION

The etiology of primary open-angle glaucoma remains unclear. Various risk factors, including vascular abnormalities, have been associated with this disease. Sleep-associated diseases, like sleep apnea syndrome, might also represent a risk factor. Sleep apnea syndrome is characterized by repetitive upper airway obstructions during sleep, inducing hypoxia and sleep disruption with the risk of cardiovascular and neurological sequelae. In this study, we determined the prevalence of sleep apnea syndrome in primary open-angle glaucoma patients.

METHODS

Overnight transcutaneous finger oximetry was performed in 30 consecutive patients having primary open-angle glaucoma. We assessed the oximetry disturbance index during night sleep, a parameter used to diagnose sleep apnea syndrome and to grade its severity.

RESULTS

Sleep apnea syndrome was more prevalent among primary open-angle glaucoma patients compared to normal historic controls of the same age and sex distribution (chi(2) = 9.35, d.f. = 3, p < 0.025). The oximetry disturbance index grade was significantly larger in the primary open-angle glaucoma group compared to normal controls (U = 3, 352, p = 0.01). According to the oximetry disturbance index, 20% (6/30) of primary open-angle glaucoma patients had sleep apnea syndrome.

CONCLUSION

Primary open-angle glaucoma is associated with sleep apnea syndrome. Early recognition and treatment of sleep apnea syndrome are important to avoid cardiovascular and neurological complications.

[Nocturnal measurements of intraocular pressure in patients with normal-tension glaucoma and sleep apnea syndrome]

BACKGROUND

About half of all normal-tension glaucoma patients and about one third of all primary open-angle glaucoma patients have sleep apnea syndrome. If sleep apnea syndrome causes some cases of glaucoma, the optic nerve damage could result from repetitive nocturnal hypoxias or from repetitive intraocular pressure elevations at the end of the apneas. In this study, we determined the intraocular pressure at the end of long apneas.

PATIENTS AND METHODS

In three patients having sleep apnea syndrome and normal-tension glaucoma we recorded in a sleep laboratory during at least six hours of sleep the respiration (oxymetry, nasal and oral air flow, and inductive plethysmography). The intraocular pressure was measured with a pneumatonometer at predetermined times and compared to the values measured at the end of prolonged apneas.

RESULTS

The intraocular pressure during normal respiration was in the first patient 19.5 +/- 1.0 mm Hg OD and 19.3 +/- 1.7 mm Hg OS, in the second patient 25.0 +/- 4.2 respectively 25.5 +/- 4.9 mm Hg and in the third one 22 +/- 1.0 respectively 21.3 +/- 1.3 mm Hg. At the end of prolonged apneas the intraocular pressure was in the first patient 19.0 +/- 0.0 mm Hg OD and 19.5 +/- 0.7 mm Hg OS, in the second patient 26.5 +/- 0.6 and 26.8 +/- 0.1 mm Hg and in the third one 20.0 +/- 0.0 respectively 21.0 +/- 0.0 mm Hg. The difference between intraocular pressures during normal respiration and at the end of prolonged apneas was not significant (p > 0.1 for each comparison, paired t-test).

CONCLUSIONS

We did not find an increase of intraocular pressure at the end of prolonged apneas compared to periods of normal respiration in patients with sleep apnea syndrome and normal-tension glaucoma. If sleep apnea syndrome causes some cases of glaucoma, it seems more probable that the the optic nerve is damaged by the repetitive hypoxias. Alternatively, an unknown factor might induce both, sleep apnea syndrome and normal-tension glaucoma.

Sleepiness-related accidents in sleep apnea patients

The frequency of motor vehicle and working accidents was analyzed by means of a strictly anonymous questionnaire in 156 patients with sleep apnea syndrome (SAS) and in 160 age-gender matched controls. In the SAS group 12.4% of all drivers had motor vehicle accidents as compared to 2.9% in the control group (p<0.005). The motor vehicle accident rate was 13.0 per million km in patients with more severe SAS (AHI > 34/h, n=78) as compared to 1.1 in patients with milder SAS (AHI 10-34/h, n=78) (p<0.05), and 0.78 in control group (p<0.005), respectively. The accident rates in both patients and the control group were also greater than the rate of 0.02 "accidents due to sleepiness" per one million km in the Swiss driving population as reported by official statistics. During treatment with nasal continuous airway pressure (nCPAP) in 85 SAS patients, the motor vehicle accident rate dropped from 10.6 to 2.7 per million km (p<0.05). We conclude that patients with moderate to severe SAS have an up to fifteen-fold risk increase of motor vehicle accidents that constitutes a serious and often underestimated hazard on the roads, which can be reduced by adequate treatment.

Task-dependent effects on motor-evoked potentials and on the following silent period

The silent period (SP) after transcranial stimulation is used as a diagnostic tool in various central nervous system disorders although no standardized experimental setup has been established. The aim of this study was to demonstrate the influence of an isotonic compared to an isometric experimental condition. The SP after transcranial magnetic brain stimulation in the biceps brachii and brachioradialis muscle was up to 130% longer when elicited during a maintain-position (isotonic) task as compared to a maintain-force task (isometric) when stimulus intensities of 5% to 25% above threshold were used. The mean SP duration in these muscles was positively correlated to the mean contraction time in both tasks. However, no such relationship was observed for the trials within the individual subjects. We speculate that the invariably longer SP of the maintain-position task was due to the different "motor set" which predictively determined the muscle behavior after the stimulus. In the maintain-position trials, the stimulus-induced long-lasting flexion movement is counteracted by a motor set aiming to relax the elbow flexors immediately after the stimulus. In the maintain-force task the contraction twitch is short and a force drop below the preset level must be prevented by a motor set aiming to contract the elbow flexors immediately after the stimulus. The latter may increase the synaptic input to the motoneuron pool and facilitate the reoccurrence of the electromyogram terminating the SP. At high-stimulus intensities the SP duration increased in both tasks, and the task-dependent differences disappeared. Therefore, when using the SP duration for diagnostic purposes, isometric conditions and high-stimulus intensities should be used.

Facial nerve dysfunction in hereditary motor and sensory neuropathy type I and III

Facial nerve function was studied in 19 patients with hereditary motor and sensory neuropathy type I (HMSN I) and 2 patients with hereditary motor and sensory neuropathy type III (HMSN III, Déjérine-Sottas), and compared to that in 24 patients with Guillain-Barré syndrome (GBS). The facial nerve was stimulated electrically at the stylomastoid fossa, and magnetically in its proximal intracanalicular segment. Additionally, the face-associated motor cortex was stimulated magnetically. The facial nerve motor neurography was abnormal in 17 of 19 HMSN I patients and in both HMSN III patients, revealing moderate to marked conduction slowing in both the extracranial and intracranial nerve segments, along with variable reductions of compound muscle action potential (CMAP) amplitudes. The facial nerve conduction slowing paralleled that of limb nerves, but was not associated with clinical dysfunction of facial muscles, because none of the HMSN I patients had facial palsy. Conduction slowing was most severe in the HMSN III patients, but only slight facial weakness was present. In GBS, conduction slowing was less marked, but facial weakness exceeded that in HMSN patients in all cases. We conclude that involvement of the facial nerve is common in HMSN I and HMSN III. It affects the intra- and extracranial part of the facial nerve and is mostly subclinical.

Supervisors' use of social power with graduate supervisees in speech-language pathology

This investigation discusses social power as an identifiable and measurable aspect of the supervisory process in speech-language pathology (SLP). This study examined the use of French and Raven's (1959) types of social power by 61 clinical supervisors with their 69 beginning and 69 advanced graduate supervisees from 14 university programs. Both supervisors' and supervisees' perceptions of supervisors' use of expert, referent, coercive, legitimate, and reward power were obtained with modified versions of the Rahim Leader Power Inventory (RLPI) (Rahim, 1988). The supervisors' perceptions of their use of the five types of social power with beginning supervisees were not significantly different from the beginning supervisees' perceptions. By contrast, the study yielded discrepant perceptions of supervisors' use of social power with advanced supervisees. Further, supervisors reported differential use of power with supervisees with different amounts of clinical experience. Yet, the perceptions of beginning and advanced supervisees did not differ relative to supervisors' use of any of the five types of social power. These findings can sensitize clinical supervisors to the sources of social power inherent in their practice.

Eyelid, conjunctival, and corneal findings in sleep apnea syndrome

OBJECTIVE

To determine the prevalence of eyelid, conjunctival, and corneal findings in patients with sleep apnea syndrome (SAS).

DESIGN

Case series.

PARTICIPANTS

Seventy-two white patients referred for evaluation of suspected SAS.

INTERVENTION

Complete examination of eyelids, conjunctiva, and cornea, including videokeratography.

MAIN OUTCOME MEASURES

Spearman rank correlations were determined between the respiratory disturbance index (RDI) during night sleep, a value used to diagnose and grade SAS, and tear film break-up time, eyelid distraction distance, presence or absence of ocular irritation symptoms, blepharoptosis, floppy eyelids, lacrimal gland prolapse, keratoconus, and endothelial dystrophy. Each correlation was controlled for age and body mass index.

RESULTS

According to the RDI, 44 (61 %) of the 72 patients had SAS. The RDI correlated positively with the eyelid distraction distance (P = 0.05), presence or absence of floppy eyelids (P = 0.01), and lacrimal gland prolapse (P = 0.01), and correlated negatively with tear film break-up time (P = 0.02). None of our patients with floppy eyelids had corneal abnormalities. One patient with SAS had bilateral keratoconus; another had bilateral Fuch endothelial dystrophy.

CONCLUSIONS

Sleep apnea syndrome was significantly associated with reduced tear film break-up time, floppy eyelids, and lacrimal gland prolapse. However, ocular irritation symptoms and corneal involvement were rare among patients with SAS. These findings do not confirm previous studies that reported a high prevalence of corneal involvement in floppy eyelid syndrome.

High prevalence of glaucoma in patients with sleep apnea syndrome

OBJECTIVE

To determine the prevalence of glaucoma in sleep apnea syndrome (SAS), an entity characterized by repetitive upper airway obstructions during sleep, inducing hypoxia and sleep disruption with the risk of cardiovascular and neurologic sequelae.

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 114 white patients consecutively referred for polysomnographic evaluation of suspected SAS.

INTERVENTION

Complete ophthalmologic examination, including computerized perimetry and simultaneous stereoscopic optic disc photographs.

MAIN OUTCOME MEASURES

Spearman rank correlations between the respiratory disturbance index during night sleep (RDI), a value used to diagnose and grade SAS, and visual acuity, intraocular pressure (IOP), visual field indices, presence or absence of glaucomatous optic disc changes, and diagnosis of glaucoma. Each correlation was controlled for age and body mass index. To compare proportions of patients harboring glaucoma, the binomial test was used.

RESULTS

Sixty-nine (60.5%) of the 114 patients had an RDI > or =10, which indicates SAS. Three patients had primary open-angle glaucoma, and two had normal-tension glaucoma. All patients with glaucoma had SAS. The observed prevalence of glaucoma in patients with SAS (5 of 69, 7.2%) was significantly higher than expected in a white population (2%) (P = 0.01). The RDI correlated positively with IOP (P = 0.025), visual field loss variance (P = 0.03), glaucomatous optic disc changes (P = 0.001), and diagnosis of glaucoma (P = 0.01).

CONCLUSIONS

Patients with SAS constitute a high-risk population for glaucoma and should therefore be screened for glaucoma.

Rapid cortical motor output map changes assessed by the triple stimulation technique

The amplitudes of motor evoked potentials (MEPs) were mapped by transcranial magnetic stimulation (TMS) using the triple stimulation technique (TST) in 11 normal individuals. Stimuli were given while the subjects were (a) distracted, (b) concentrating on their target (recorded) hand, and (c) concentrating on their contralateral hand. Within seconds, the proportion of excited motor units increased, similarly in all subjects, by an average of 70% from (a) to (b), and by 48% from (a) to (c). At the optimal stimulation site, results obtained with the TST were compared to those of conventional MEPs. The TST proved superior in detecting the rapid changes of the motor output caused by the non-specific mental tasks studied.

A clinical study of motor evoked potentials using a triple stimulation technique

Amplitudes of motor evoked potentials (MEPs) are usually much smaller than those of motor responses to maximal peripheral nerve stimulation, and show marked variation between normal subjects and from one stimulus to another. Consequently, amplitude measurements have low sensitivity to detect central motor conduction failures due to the broad range of normal values. Since these characteristics are mostly due to varying desynchronization of the descending action potentials, causing different degrees of phase cancellation, we applied the recently developed triple stimulation technique (TST) to study corticospinal conduction to 489 abductor digiti minimi muscles of 271 unselected patients referred for possible corticospinal dysfunction. The TST allows resynchronization of the MEP, and thereby a quantification of the proportion of motor units activated by the transcranial stimulus. TST results were compared with those of conventional MEPs. In 212 of 489 sides, abnormal TST responses suggested conduction failure of various degrees. By contrast, conventional MEPs detected conduction failures in only 77 of 489 sides. The TST was therefore 2.75 times more sensitive than conventional MEPs in disclosing corticospinal conduction failures. When the results of the TST and conventional MEPs were combined, 225 sides were abnormal: 145 sides showed central conduction failure, 13 sides central conduction slowing and 67 sides both conduction failure and slowing. It is concluded that the TST is a valuable addition to the study of MEPs, since it improves detection and gives quantitative information on central conduction failure, an abnormality which appears to be much more frequent than conduction slowing. This new technique will be useful in following the natural course and the benefit of treatments in disorders affecting central motor conduction.

Role of the prefrontal cortex in the control of express saccades. A transcranial magnetic stimulation study

Single pulse transcranial magnet stimulation (TMS) was applied in five subjects during a saccadic gap task, i.e. with a temporal gap of 200 ms between the extinguishing of the central fixation point and the appearance of the lateral target. In all subjects, a significant increase of contralateral express saccades was found when TMS was applied over the dorsolateral prefrontal cortex (DPFC) at the end of the gap of 200 ms. Earlier stimulation over the DPFC during the gap had no significant effect. Furthermore, stimulation over the posterior parietal cortex with the same time intervals, and stimulation during a no gap task had no significant influence on express saccades. These results suggest that TMS is capable of interfering specifically with the functioning of the DPFC, probably by inhibition of this region. Possibly such stimulation of the DPFC reduces the inhibition by this region onto the superior colliculus, which results in a facilitation of express saccades.

Dependence of the transcranially induced silent period on the 'instruction set' and the individual reaction time

OBJECTIVES AND METHODS

We looked for influences of the experimental condition on the silent period (SP) from transcranial motor cortex stimulation and analyzed how the instruction given to the subject, as well as the individual reaction time, might affect the duration of the SP in the biceps brachii muscle.

RESULTS

The duration of the SP was found to critically depend on the subject's voluntary reaction of the target muscle immediately after the stimulus. With low stimulus intensity and low background force, the duration of the silent period was significantly longer in 10 of 13 subjects (P = 0.002) when they were instructed to relax quickly after the stimulus rather than to maintain the the force at a constant level. A significant shortening of the SP (P = 0.02) was observed when the subjects were instructed to perform a rapid contraction of the target muscle in reaction to the cortical stimulus. With low stimulus intensity and high background force, the same influence of the instruction set was found in 6 of 13 subjects. When the subjects were left without precise instruction, the SP duration was unpredictable. In 10 subjects, the SP corresponded to that obtained with the instruction to maintain the force at a constant level. However, in 3 subjects it was prolonged to the value observed in the 'relax' instruction. With greater stimulus intensities, the effect of the instruction set on the SP duration was generally smaller. A significant prolongation was nevertheless found at low background forces with rapid relaxation (P < 0.001), and a significant shortening was found at high background forces with rapid contraction (P < 0.001) after the stimulus. The SP duration observed with 20% of maximal voluntary contraction (MVC) significantly correlated with the individual reaction time. No such correlation was found for the SP obtained with 80% MVC. The SP was slightly longer at 20% MVC, as compared to 80% MVC within each instruction group. This effect was significant (P < 0.05) at low stimulus intensities.

CONCLUSIONS

Therefore, when assessing the SP duration for diagnostic purposes, not only the stimulus intensity but also the background force and the voluntary reaction must be standardized. Furthermore, great stimulus intensities and high background forces should be used to minimise the effects of instruction set and individual reaction time.

Task-dependent facilitation of motor evoked potentials during dynamic and steady muscle contractions

Task-dependent differences in the facilitation of motor evoked potentials (MEPs) following cortex stimulation were studied in a proximal (deltoid) and a distal muscle (abductor digiti minimi; ADM) in 23 healthy subjects during both dynamic and steady contractions of the target muscle under isometric and under nonisometric conditions. In the deltoid, MEP amplitudes were significantly greater if stimulation was performed during dynamic contractions than during steady contractions, despite equal background electromyographic levels just prior to the stimulus. The same task-specific extra facilitation of deltoid MEP amplitudes was also found with magnetic stimulation of the brain stem instead of the cortex in 3 subjects. In the ADM, no such task-dependent extra facilitation of MEPs during dynamic contractions was found. It is concluded that in the deltoid, during dynamic contractions, a greater proportion of the spinal motoneurons is close to depolarization threshold (greater "subliminal fringe") whereas the number of firing motoneurons is similar to that during steady contraction. The lack of task-dependent extra facilitation of MEPs in the ADM is explained by the predominant recruitment principle for force gradation in small hand muscles, which is in contrast to the predominant frequency principle used in proximal muscles.

Functional organisation of saccades and antisaccades in the frontal lobe in humans: a study with echo planar functional magnetic resonance imaging

The cortical activation pattern of saccades and antisaccades (versus rest) in the frontal lobe was analysed using an echo planar imaging (EPI) technique in 10 healthy subjects. Statistical analysis of activity in the dorsolateral prefrontal cortex disclosed a significantly greater activation during antisaccades in this region than during saccades. On the other hand, activity in the frontal eye fields was not statistically different in both tasks. These results confirm the important role of the dorsolateral prefrontal cortex for the correct performance of antisaccades obtained by studies in humans with isolated lesions of the dorsolateral prefrontal cortex.

[X-chromosomal bulbospinal muscular atrophy (Kennedy syndrome)]

Two brothers with slowly progressive weakness and congenital nystagmus are presented. DNA analysis confirmed X-linked recessive bulbospinal muscular atrophy (XBSMA, Kennedy's disease) by demonstration of increased size of a CAG-triplet repeat on the androgen receptor gene on the X-chromosome. XBSMA is characterized by almost symmetrical muscular atrophy, weakness and fasciculations predominantly of bulbar, facial and proximal muscles of the extremities, with onset in the third to fifth decade. Tendon reflexes are depressed and pyramidal signs are absent. Sensory symptoms are clinically rare, but sensory nerve action potentials are frequently abnormal. Additional symptoms are important for differential diagnosis, and include postural tremor, gynecomastia, diabetes mellitus, testicular atrophy and impotence. Differentiation of this hereditary disorder from treatable conditions such as multifocal motor neuropathy or amyotrophic lateral sclerosis is essential. Though life expectancy is normal, patients become disabled in the course of the disease and need supportive care. Periodic testing for diabetes is recommended, and genetic counseling should be provided for patients and their relatives.

Developmental background and outcome in patients with nonepileptic versus epileptic seizures: a controlled study

PURPOSE

This study was designed to evaluate the relevance of developmental emotional stress factors, which are considered to influence emotional functioning, as contributing factors in the development of psychogenic symptoms.

METHODS

Ten patients with nonepileptic seizures (non-ESs) (frequently referred to as psychogenic seizures), in whom diagnosis had been confirmed by a placebo-infusion test (PT), and 10 control patients with complex partial seizures (ESs) were evaluated with regard to developmental background by using structured in-depth interviews performed by a single interviewer blinded to the diagnosis. In addition, outcome assessment in the non-ES group after PT was done.

RESULTS

There were no significant differences between groups in developmental psychosocial stress or in any single developmental stress factor. Six months after PT, the outcome was favorable in patients with non-ES: six were seizure free, and two had a considerable reduction in frequency of seizures.

CONCLUSIONS

Our research indicates the following: (a) a high incidence of developmental stress factors and functional disturbances may be found in patients with non-ESs and ESs; (b) assessment of developmental emotional stress and functional disturbances as a basis for validating the diagnosis of non-ES should be treated with caution; (c) use of PT followed by supportive information about the nonepileptic origin of the attacks may have a positive therapeutic effect or help to introduce psychotherapeutic treatment.

Optic neuropathy associated with sleep apnea syndrome

OBJECTIVE

The study aimed to determine ocular abnormalities in sleep apnea syndrome (SAS), an entity characterized by repetitive upper airway obstructions during sleep, inducing hypoxia and sleep disruption with the risk of cardiovascular and neurologic sequelae.

DESIGN

The study design was a case series.

PARTICIPANTS

Nine patients referred for evaluation of suspected SAS participated.

INTERVENTION

Complete ophthalmologic examination, including computerized perimetry, was performed.

MAIN OUTCOME MEASURES

Correlations between the respiratory disturbance index (RDI) during night sleep, a value used to diagnose and to grade SAS, and visual field indices using the Spearman rank correlation coefficient (r(s)) were measured.

RESULTS

One patient was excluded from the statistical analysis because of optic nerve drusen with constricted visual fields, another because of tilted discs with corresponding temporal visual field defects. All three patients with severe SAS and one patient with moderate SAS had relative nasal arcuate visual field defects; two patients with severe SAS also had paracentral relative defects. One patient with normal polysomnographic result and two patients with mild or moderate SAS had normal visual fields. The RDI correlated positively with the mean visual field defect (r(s) = 0.81, P < 0.05) and with the visual field loss variance (r(s) = 0.78, P < 0.05). The clinical ophthalmologic examination results were normal in all seven patients. In two of the three patients with severe SAS treated with continuous positive airway pressure (CPAP), visual field defects remained stable over 18 months. The patient with optic nerve drusen also had severe SAS and was, therefore, treated with CPAP. His constricted visual fields improved dramatically after treatment.

CONCLUSIONS

Visual fields of patients with SAS showed defects consistent with an optic neuropathy. The CPAP therapy seems to stabilize or even reverse visual field defects.

Recording of electrical brain activity in a magnetic resonance environment: distorting effects of the static magnetic field

The technical limitations of electroencephalography (EEG) and flashed visually-evoked potentials (VEP) recordings in the static magnetic field of the MR system were systematically studied. A main artifact occurring in the magnetic field was found to be correlated with the heart cycle and had amplitudes in the range of EEG and VEP signals. For VEP recordings, a substantial reduction of this effect was achieved by subtraction of the averaged artifact from the averaged composed signal (VEP and artifact) resulting in the VEP signal alone. However, for continuous EEG recordings, there is no such solution, since the observed effect is not sufficiently constant in amplitude, and the standard deviation of the amplitude of the effect is often larger than the EEG amplitude.

[Ocular myositis]

We report a young woman presenting with "painful diplopia" caused by inflammation of external eye muscles affecting both eyes sequentially. Orbital MRI disclosed swelling, signal hyperintensity and enhancement of isolated eye muscles. Corticosteroid treatment led to a complete remission within a few days. The compiled data of a literature review enclosing 52 sufficiently documented patients diagnosed as orbital myositis is reported with respect to clinical features, laboratory findings, associated disease, value of imaging procedures (CT,MRI). Therapeutic aspects and differential diagnosis are reviewed.