British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders

Sleep disorders are common in the general population and even more so in clinical practice, yet are relatively poorly understood by doctors and other health care practitioners. These British Association for Psychopharmacology guidelines are designed to address this problem by providing an accessible up-to-date and evidence-based outline of the major issues, especially those relating to reliable diagnosis and appropriate treatment. A consensus meeting was held in London in May 2009. Those invited to attend included BAP members, representative clinicians with a strong interest in sleep disorders and recognized experts and advocates in the field, including a representative from mainland Europe and the USA. Presenters were asked to provide a review of the literature and identification of the standard of evidence in their area, with an emphasis on meta-analyses, systematic reviews and randomized controlled trials where available, plus updates on current clinical practice. Each presentation was followed by discussion, aimed to reach consensus where the evidence and/or clinical experience was considered adequate or otherwise to flag the area as a direction for future research. A draft of the proceedings was then circulated to all participants for comment. Key subsequent publications were added by the writer and speakers at draft stage. All comments were incorporated as far as possible in the final document, which represents the views of all participants although the authors take final responsibility for the document.

Functional gamma-secretase inhibitors reduce beta-amyloid peptide levels in brain

Converging lines of evidence implicate the beta-amyloid peptide (Ass) as causative in Alzheimer's disease. We describe a novel class of compounds that reduce A beta production by functionally inhibiting gamma-secretase, the activity responsible for the carboxy-terminal cleavage required for A beta production. These molecules are active in both 293 HEK cells and neuronal cultures, and exert their effect upon A beta production without affecting protein secretion, most notably in the secreted forms of the amyloid precursor protein (APP). Oral administration of one of these compounds, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, to mice transgenic for human APP(V717F) reduces brain levels of Ass in a dose-dependent manner within 3 h. These studies represent the first demonstration of a reduction of brain A beta in vivo. Development of such novel functional gamma-secretase inhibitors will enable a clinical examination of the A beta hypothesis that Ass peptide drives the neuropathology observed in Alzheimer's disease.

Transient ischaemic attacks: evaluation and management

Transient ischaemic attacks (TIAs) are temporary focal cerebral or retinal deficits that resolve within 24 hours. Attention should be given to the tempo and localisation of the clinical syndrome, as multiple and hemispheric TIAs are associated with the greatest incidence of early stroke. Evaluation of TIAs depends on the clinical symptoms, physical examination and investigations. Attention should be given to clinical evidence of generalised atherosclerotic disease, as death due to the complications of ischaemic heart disease is the commonest outcome in patients with TIA. Early attention should focus on risk factor modification, with emphasis on the treatment of hypertension and smoking cessation. Antiplatelet therapy should be instituted. Aspirin is the first-line treatment but, if not tolerated, clopidogrel is effective in preventing vascular complications. Anticoagulants are generally reserved for patients with atrial fibrillation and are associated with a significant reduction of stroke risk. The use of statins is becoming more widespread, with emerging evidence of their efficacy in reducing stroke risk. The risk of stroke is greatest in the weeks following TIA and patients should be referred for carotid duplex ultrasonography. Carotid endarterectomy for symptomatic internal carotid artery high grade stenosis virtually abolishes stroke risk in that vascular territory over subsequent years. TIAs should be regarded as an emergency requiring early diagnosis and prompt referral.

The timing of primary orthostatic tremor bursts has a task-specific plasticity

Primary orthostatic tremor is characterized by unsteadiness and shakiness of the legs while standing. It is due to a remarkably strong and regular EMG modulation at approximately 16 Hz that is thought to be of CNS origin. Previous studies have shown that the tremor frequency is the same in all involved muscles and that the time relation between bursts of activity in different muscles may be fixed (e.g. always co-contracting or always contracting in an alternating pattern). Here we have used frequency domain analysis of postural muscle EMG signals in five primary orthostatic tremor patients and in two normal controls to explore the nature of such fixed timing patterns. The timing is found not to relate simply to the relative conduction times for passage of rhythmic bursts from a central oscillation to different muscles. Indeed, although the timing pattern (expressed as phase) of the 16-Hz EMG bursts in different postural muscles remains constant while the subject adopts a certain steady posture, it is different for different subjects and also changes when the same subject adopts a different posture. It seems unlikely that such complex task-dependent timing relations of rhythmic postural muscle activity are due to the primary pathology of primary orthostatic tremor. Instead, we suggest that the abnormally strong peripheral manifestation of a 16-Hz CNS oscillation merely unmasks normal central processes so that the timing patterns may provide a clue to the nature of postural motor control.

Structure-activity relationship of a series of diaminoalkyl substituted benzimidazole as neuropeptide Y Y1 receptor antagonists

A series of benzimidazoles (4) was synthesized and evaluated in vitro as potent and selective NPY Y1 receptor antagonists. Substitution of the piperidine nitrogen of 4 with appropriate R groups resulted in compounds with more than 80-fold higher affinity at the Y receptor compared to the parent compound 5 (R = H). The most potent benzimidazole in this series was 21 (Ki = 0.052 nM).

Structure-activity relationships of a series of benzothiophene-derived NPY Y1 antagonists: optimization of the C-2 side chain

A series of benzo[b]thiophene-derived NPY-1 receptor antagonists is described. Systematic modification of the C-2 substituent afforded a 1000-fold range in Y1 receptor affinity. Appropriate substitution at the ortho and para positions of the C-2 phenyl ether produced a synergistic effect on Y1 binding affinity, which led to the discovery of the most active ligands, 12t (K(i) = 15 nM), 12u (K(i) = 11 nM), and 12v (K(i) = 13 nM).

Synthesis and evaluation of a series of novel 2-[(4-chlorophenoxy)methyl]benzimidazoles as selective neuropeptide Y Y1 receptor antagonists

A series of novel benzimidazoles (BI) derived from the indole 2 was synthesized and evaluated as selective neuropeptide Y (NPY) Y1 receptor antagonists with the aim of developing antiobesity drugs. In our SAR approach, the (4-chlorophenoxy)methyl group at C-2 was kept constant and a series of BIs substituted with various piperidinylalkyl groups at N-1 was synthesized to identify the optimal spacing and orientation of the piperidine ring nitrogen relative to the benzimidazole. The 3-(3-piperidinyl)propyl in 33 was found to maximize affinity for the Y1 receptor. Because of the critical importance of Arg33 and Arg35 of NPY binding to the Y1 receptor, the incorporation of an additional aminoalkyl functionality to the structure of 33 was explored. Methyl substitution was used to probe where substitution on the aromatic ring was best tolerated. In this fashion, the C-4 was chosen for the substitution of the second aminoalkyl functionality. Synthesis of such compounds with a phenoxy tether using the 4-hydroxybenzimidazole 11 was pursued because of their relative ease of synthesis. Functionalization of the hydroxy group of 45 with a series of piperidinylalkyl groups provided the dibasic benzimidazoles 55-62. Among them, BI 56 demonstrated a Ki of 0.0017 microM, which was 400-fold more potent than 33. To evaluate if there was a stereoselective effect on affinity for these BIs, the four constituent stereoisomers (69-72) of the BI 60 were prepared using the S- and R-isomers of bromide 17. Antagonist activity of these BIs was confirmed by measuring the ability of selected compounds to reverse NPY-induced forskolin-stimulated cyclic AMP. The high selectivity of several BI antagonists for the Y1 versus Y2, Y4, and Y5 receptors was also shown.

Structure-activity relationships of a series of 1-substituted-4-methylbenzimidazole neuropeptide Y-1 receptor antagonists

The characterization of a novel series of NPY-1 receptor antagonists derived from the 4-methylbenzimidazole 4 is described. Appropriate substitution on the piperidyl nitrogen of 4 led to systematic increases in Y-1 receptor affinity, to approximately 50-fold, and to the discovery of the importance of a second basic substituent.

Acute sciatica with an infective cause

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Tremor associated with benign IgM paraproteinaemic neuropathy

The clinical and neurophysiological features of six patients with action tremor of the upper limbs associated with IgM paraproteinaemic neuropathy are described. Symptomatic tremor was confined to the upper limbs and was broadly symmetrical. The frequency of associated rhythmic muscle activity ranged from 2.8 to 5.5 Hz in abductor pollicis brevis and from 3.7 to 5.5 Hz in the forearm flexor muscles. Magnetic brain stimulation, somatosensory evoked potentials (SEPs) and stretch reflex studies did not provide evidence for delayed conduction within central pathways. There was marked slowing of the maximum motor conduction velocities in peripheral nerves. Forearm stretch reflexes were present but their latencies were prolonged. Somatosensory evoked potentials were obtained in the majority of patients, but were delayed. Wrist tremor could be modulated by mechanical perturbations or median nerve electrical shocks. Simple voluntary wrist movements were of normal duration and peak velocity, but the kinematic profile was asymmetric. Each movement was associated with a triphasic EMG pattern in agonist-antagonist-agonist muscles but the durations of the bursts were prolonged and the onset of the second agonist was delayed. These results support the hypothesis that distorted, mistimed peripheral inputs reach a central processor (probably the cerebellum) which although intact is misled into producing tremor in certain parts of the body.

Primary writing tremor

Primary writing tremor (PWT) is considered to be a type of task-specific tremor in which tremor predominantly occurs and interferes with handwriting. We describe the clinical and neurophysiological features of 21 patients (20 male and one female) with PWT. Mean age at tremor onset was 50.1 years. A family history of PWT was obtained from seven patients. Ten patients obtained benefit from drug treatment (mainly propranalol or primidone) and seven responded to alcohol. The writing speeds of the patients (mean +/- SEM: 73.1 +/- 6.6 letters per minute) when using their preferred hand were significantly reduced (Student's t test: P < 0.001) compared with those of healthy control subjects (mean +/- SEM: 127.7 +/- 6.4). Surface polymyography performed during writing showed 4.1-7.3 Hz rhythmic activity predominantly in the intrinsic hand and forearm muscles. Alternating, extensor activation alone, skipping from alternating to extensor activation, and co-contracting EMG patterns were recorded from the flexor and extensor muscles of the forearm. There was no evidence for excessive 'overflow' of this rhythmic EMG activity, as similar activity was detected in comparable muscle groups of healthy control subjects. Accelerometry confirmed that the frequency of PWT ranged from 4.1-7.3 Hz (median 5.5 Hz) and that normal subjects wrote with a 4.0-7.7 Hz oscillation (median 4.6 Hz). Forearm reciprocal inhibition was normal in PWT (n = 13), and thus patients with PWT can be distinguished from those with writer's cramp in whom decreased presynaptic inhibition has been found. Patients were sub-classified as having either type A (n = 11) or B (n = 10) PWT depending on whether tremor appeared during writing (type A: task induced tremor) or whilst writing and adopting the hand position used in writing (type B: positionally sensitive tremor). However, the only differences between these two groups were that a co-contracting EMG pattern and tremor induced by tendon taps to the volar aspect of the wrist were present in type B but not type A cases.

Essential tremor and its variants

Essential tremor is the commonest of movement disorders. Although sometimes prefaced with the term 'benign', it often causes significant disability. Diagnosis is based on the clinical finding of a postural tremor, predominantly affecting the upper limbs, that is absent at rest and not associated with extrapyramidal or cerebellar signs. There are, as yet, no specific anatomical, physiological, biochemical or genetic markers for the condition. Postural limb tremors, clinically indistinguishable from essential tremor, may occur in patients who have, or will later develop, other neurological conditions; whether such patients have essential tremor is a matter of controversy that will only be resolved with a better understanding of the pathophysiology of essential tremor. Positron emission tomography in patients with essential tremor reveals increased cerebellar activity even at rest, a finding that is consistent with the cerebellum having an important role in the generation of tremor. Abnormal cerebellar function has also been invoked to account for the abnormal manner in which patients with essential tremor perform rapid voluntary wrist movements. Molecular genetic studies in hereditary essential tremor have been initiated, but with negative results so far. Several new drug treatments have been tried, but with limited success; the role of thalamic stimulation and botulinum toxin in the treatment of essential tremor remains to be judged.

Exacerbation of postural tremor with emergence of parkinsonism after treatment with neuroleptic drugs

Neuroleptic medication in three patients with prior isolated postural arm tremor led to a conspicuous deterioration; the postural tremor increased in amplitude, tremor appeared at rest, and other signs of mild parkinsonism developed. Withdrawal of neuroleptic drugs led to improvement in tremor and disappearance of parkinsonism. Positron emission tomography showed no reduction in uptake of [18F]dopa into nigrostriatal terminals suggesting that these patients did not have Parkinson's disease. Neuroleptic drugs can convert postural essential arm tremor into that characteristic of Parkinson's disease in patients with no evident nigrostriatal lesion.

The myoclonus in corticobasal degeneration. Evidence for two forms of cortical reflex myoclonus

The clinical and physiological characteristics of myoclonus in 14 patients with corticobasal degeneration are described. The myoclonus was focal, confined to one limb (usually the arm) and was most prominent on voluntary action or in response to sensory stimulation. On clinical inspection, the myoclonus appeared to occur at rest but EMG recordings revealed that apparently spontaneous myoclonus occurred only on a background of more or less continuous muscle activity (responsible for the rigidity and dystonia). The jerks consisted of hypersynchronous short duration bursts of EMG activity coincident in agonists and antagonists. Reflex myoclonus in hand muscles, to stimulation of the median nerve at the wrist, had a latency of approximately 40 ms. In 13 of the 14 patients reflex myoclonus was not associated with enlargement of the cortical sensory evoked potentials (SEPs); the later components of the parietal SEP were poorly formed and dominated by a broad positive wave with a peak latency approximately 45 ms. Prefrontal components of the SEP were relatively preserved, but there were no significant differences between the SEPs evoked from myoclonic and non-myoclonic limbs. Action myoclonus was not preceded by an identifiable cortical wave in the electroencephalogram back-averaged before each jerk. Magnetic, but not electric, brain stimulation evoked repetitive bursts of myoclonus suggesting enhanced cortical excitability. The combination of focal, predominantly distal, hypersynchronous jerks, evidence of enhanced cortical excitability, together with the known cortical pathology in corticobasal degeneration suggests that the myoclonus in these patients may be cortical in origin. Since the latency of reflex myoclonus in corticobasal degeneration is only 1-2 ms longer than the sum of the afferent and efferent times to and from the cortex, we propose the reflex myoclonus is mediated by direct sensory input to motor cortical areas that activate corticospinal tract output. Such myoclonus differs from the typical form of cortical reflex myoclonus in which reflex jerks have a longer latency (50 ms in hand muscles), cortical SEPs are enlarged and action myoclonus is preceded by a cortical discharge. It is proposed that these various forms of cortical myoclonus can be explained by the presence of different cortical relays of sensory information to cortical motor areas. The myoclonus of corticobasal degeneration may represent enhancement of a direct sensory input to the motor cortex. In contrast, the more widely recognized variety of cortical reflex myoclonus may involve abnormal relays through sensory cortex to motor cortex, either directly or via cerebellar-thalamo-cortical projections.

Degradation chemistry of gemcitabine hydrochloride, a new antitumor agent

The anti-tumor agent gemcitabine hydrochloride, a beta-difluoronucleoside, is remarkably stable in the solid state. In 0.1 N HCI solution at 40 degrees C, deamination of gemcitabine occurs, yielding its uridine analogue. Approximately 86% of the initial gemcitabine remains after 4 weeks under these conditions. Cleavage of the N-glycosidic bond of gemcitabine or conversion to its alpha-anomer in 0.1 N HCI solution is not observed over a 4-week period. However, this work has shown that gemcitabine hydrochloride anomerizes in 0.1 N NaOH at 40 degrees C. Approximately 72% of the initial gemcitabine remains after 4 weeks under the basic conditions used. Uridine hydrolysis products are also formed under these conditions. The anormerization reaction, which is unusual under basic conditions, has been confirmed by characterization of the chromatographically isolated alpha-anomer by NMR and mass spectrometry. A mechanism involving an acyclic intermediate is proposed.

Rapid wrist movements in patients with essential tremor. The critical role of the second agonist burst

Ballistic wrist flexion movements towards 15, 30 and 60 degrees visual targets were studied in a group of 17 patients with hereditary essential tremor. Compared with age-matched normal subjects (n = 16), there were three main kinematic differences: patients overshot the target a little more; the kinematic profile of their movements was more 'asymmetric' due to higher peak decelerations; and their movements initiated tremor. Ballistic movements performed by patients with essential tremor were associated with a triphasic pattern of agonist-antagonist-agonist muscle activity similar to that of normal subjects. The duration and size of each EMG burst was normal. The onset latency of the antagonist EMG burst was also normal, but the onset of the second agonist EMG burst was delayed. The delay in the onset of the second agonist EMG activity resulted in unopposed action of the antagonist muscle in the second half of each movement. As a result, deceleration occurred too rapidly as the hand returned past the target leading to a series of damped oscillations around the point of aim. The onset latency of the second agonist EMG burst correlated significantly with the tremor period; the longer the period the later the burst. We speculate that the delay in the second agonist burst reflects an abnormality in the timing of anticipatory muscle activity in essential tremor and that this may involve cerebellar mechanisms.

Modulation of postural tremors at the wrist by supramaximal electrical median nerve shocks in essential tremor, Parkinson's disease and normal subjects mimicking tremor

The response of postural wrist tremors to supramaximal median nerve stimulation was examined in patients with hereditary essential tremor (n = 10) and Parkinson's disease (n = 9), and in normal subjects mimicking wrist tremor (n = 8). The average frequency of on-going tremor was the same in all three groups. Supramaximal peripheral nerve shocks inhibited and then synchronised the rhythmic electromyographic (EMG) activity of all types of tremor. The duration of inhibition ranged from 90 to 210ms, varying inversely with the frequency of on-going tremor. There was no significant difference in mean duration of inhibition or in the timing of the first peak after stimulation on the average rectified EMG records between the three groups. The degree to which supramaximal peripheral nerve shocks could modulate the timing of rhythmic EMG bursts in the forearm flexor muscles was also quantified by deriving a resetting index. No significant difference in mean resetting index of the three groups was found. These results suggest that such studies cannot be used to differentiate between the common causes of postural wrist tremors.

Postural electromyographic responses in the arm and leg following galvanic vestibular stimulation in man

Application of a small (around 1 mA), constant electric current between the mastoid processes (galvanic stimulation) of a standing subject produces enhanced body sway in the approximate direction of the ear behind which the anode is placed. We examined the electromyographic (EMG) responses evoked by such stimulation in the soleus and in the triceps brachii muscles. For soleus, subjects stood erect, with their eyes closed, leaning slightly forward. The head was turned approximately 90 degrees to the right or left relative to the feet. In averaged records (n = 40), current pulses of 25 ms or longer modulated the EMG in a biphasic manner: a small early component (latency 62 +/- 2.4 ms, mean +/- SEM) was followed by a larger late component (latency 115 +/- 5.2 ms) of opposite sign, which was appropriate to produce the observed body sway. The early component produced no measurable body movement. Lengthening the duration of the stimulus pulse from 25 to 400 ms prolonged the late component of the response but had little effect on the early component. Short- and long-latency EMG responses were also evoked in the triceps brachii muscle if subjects stood on a transversely pivoted platform and had to use the muscle to maintain their balance in the anteroposterior plane by holding a fixed handle placed by the side of their hip. The latency of the early component was 41 +/- 2.6 ms; the latency of the late component was 138 +/- 4.3 ms and was again of appropriate sign for producing the observed body sway. Galvanic stimulation evoked no comparable responses in either triceps brachii or soleus muscles if these muscles were not being used posturally.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of postural wrist tremors by magnetic stimulation of the motor cortex in patients with Parkinson's disease or essential tremor and in normal subjects mimicking tremor

The effect of magnetic brain stimulation on postural wrist tremor was studied in 10 patients with Parkinson's disease, 12 with hereditary essential tremor, and 10 normal subjects who mimicked tremor by making rapid alternating wrist movements. In all patients and normal subjects, magnetic brain stimulation over the contralateral motor cortex at an intensity approximately 10% above threshold produced the following sequence of events: (1) a small direct electromyographic (EMG) response, followed by (2) suppression of the rhythmic EMG activity responsible for the tremor, before (3) reappearance of the tremor time-locked to the stimulus. It is concluded that magnetic brain stimulation over the motor cortex can modulate the oscillatory mechanisms responsible for the generation of postural tremors. Group analysis revealed that the time to reappearance of rhythmic EMG activity varied significantly with the period of parkinsonian postural tremors, but not with the period of essential or mimicked tremors. Magnetic stimulation also significantly shortened the period of parkinsonian postural tremors, but did not influence the period of essential or mimicked tremors. These behavioral differences indicate differences in the pathophysiological mechanisms underlying parkinsonian postural tremor and essential tremor.

Motor responses evoked by magnetic brain stimulation in psychogenic limb weakness: diagnostic value and limitations

The latencies and amplitudes of responses evoked by magnetic brain stimulation (magnetic evoked potentials, MEP) in the first dorsal interosseus and the anterior tibial (TA) muscles were investigated in 15 patients with psychogenic limb weakness and in 50 patients with limb weakness due to established organic central nervous system disease. Of the patients with psychogenic limb weakness, 3 presented with upper limb monopareses, 2 with lower limb monoparesis, 4 with hemipareses, 4 with parapareses and 2 with paraparesis. All patients with psychogenic weakness had MEP in arm and leg muscles with latencies within the normal range. MEP amplitudes were also normal except for 1 patient in whom the response amplitude in the TA of the plegic limb was reduced. In patients with limb weakness due to established organic disease, MEP were frequently but not invariably abnormal. In patients with plegic (i.e. completely paretic, MRC grade 0) muscles due to organic disease, MEP always were clearly abnormal. Normal MEP were sometimes elicited from paretic muscles, more commonly in association with cerebral hemisphere lesions than with spinal lesions. We conclude that psychogenic limb weakness is associated with normal MEP. However, normal MEP in mildly paretic muscles do not definitely exclude organic pathology.

"Resetting" of postural tremors at the wrist with mechanical stretches in Parkinson's disease, essential tremor, and normal subjects mimicking tremor

The response of postural wrist tremors to brief mechanical displacements was compared in two groups of patients, one with classical hereditary essential tremor (n = 18) and another with typical Parkinson's disease (n = 13). These groups were compared with an additional group of normal subjects mimicking wrist tremor (n = 9). The degree to which brief mechanical displacements of the wrist produced by torque pulses of three different sizes could modulate the timing of rhythmic electromyographic bursts in the forearm flexor muscles was quantified by deriving a resetting index, which could range between 0 (no phase resetting) and 1 (complete phase resetting). In all three groups of subjects studied, the resetting index varied significantly with the size of the mechanical perturbation and, in an inverse fashion, with the ongoing tremor amplitude. When due allowance for these factors was made, the difference in mean resetting indexes between the three groups of patients and subjects was reduced to the extent that no definitive statement could be made as to whether brief mechanical perturbations had more effect on essential tremor than parkinsonian tremor. The method is therefore unlikely to be useful in differentiating the common causes of postural wrist tremors.

Primary orthostatic tremor: further observations in six cases

The clinical and physiological features of six new patients with primary orthostatic tremor are described. We suggest that use of the term primary orthostatic tremor be confined to the clinical syndrome in which unsteadiness when standing is the predominant complaint and accompanied by characteristic electrophysiological findings of a rapid (frequency around 16 Hz), regular leg tremor which is not influenced by peripheral feedback, is synchronous between homologous leg muscles, and in certain postures of the upper limbs, between muscles of the arm and leg. The fast frequency of muscle activity in primary orthostatic tremor of the legs causes unsteadiness when standing (presumably due to partially fused muscle contraction) but only a fine ripple of muscle activity is visible. In contrast, the slower frequency of other leg tremors, for example essential tremor, results in obvious leg movement which is evident in many leg postures, is variable over time and can be reset by a peripheral nerve stimulus. Essential tremor and orthostatic tremor do not respond to the same therapies, suggesting differences in the pharmacological profiles of the two conditions. Accordingly, there are clinical, physiological and pharmacological differences between primary orthostatic and essential tremor. Whether these factors are sufficient to regard these tremors as separate conditions is discussed.

[Normal values and age-related changes in magneto-electric evoked compound muscle potentials]

A number of 57 normal subjects was investigated using transcranial magnetic stimulation of the motor cortex and transcutaneous magnetic stimulation of the spinal nerve root in order to obtain normative data for central and peripheral motor latencies. Under standardized conditions (site of stimulation, stimulus intensity, degree of voluntary tonic background activation) muscle compound action potentials were recorded from different muscles of the upper and lower extremity: M. biceps brachii, M. extensor carpi radialis, M. interosseus dorsalis I, M. vastus medialis, M. tibialis anterior, and M. extensor digitorum brevis. Onset latency, peak to peak amplitude (% of maximal M-wave), duration and configuration of the muscle compound action potentials were evaluated (Fig. 1 and Tab. 1-6). Central and peripheral motor latencies were determined by stimulation over two different points of the neuraxis (cortex/cervical or lumbar nerve roots). Central motor latencies were calculated by subtracting the peripheral conduction time from the onset latency of the fastest cortically evoked muscle response. Not only the peripheral but also the central motor latencies were found to increase in higher ages (Tab. 6). This has to be taken into account when elderly patients are examined for diagnosis of disorders of the descending motor tracts.

Wilson's disease: normalisation of cortically evoked motor responses with treatment

A newly diagnosed patient with Wilson's disease is reported in whom the only clearly pathological neurophysiological findings before treatment were abnormal electromyographic (EMG) responses evoked by transcranial magnetic brain stimulation. Serial examinations over 10 months following commencement of treatment with D-penicillamine revealed normalisation of EMG responses. Pathophysiologically, the initially abnormal EMG responses probably resulted from reversible impairment of impulse propagation along cortico-motor-neuronal pathways and/or a reduced excitability of cortical cells due to impaired function of the basal ganglia.

The hyperekplexias and their relationship to the normal startle reflex

The startle response to unexpected auditory and somaesthetic stimulation was studied in 8 patients with hereditary or symptomatic hyperekplexia. It was abnormal in its resistance to habituation and in its exaggerated motor response. Both noise and taps to the face and head elicited a normal early blink response, separate from the subsequent true startle reflex. The earliest reflex EMG activity recorded after the blink was in sternocleidomastoid. EMG activity in masseter, and trunk and limb muscles followed later. This pattern of muscle recruitment suggests a brainstem origin for the abnormal startle responses. In addition, the abnormal startle responses exhibited disproportionately long latencies to the intrinsic hand and foot muscles and relatively slow recruitment of caudal muscles. The pattern of muscle recruitment was similar between patients, irrespective of the absolute latency of the response, and regardless of whether stimulation was auditory or somaesthetic. This suggests that auditory and somaesthetic afferents converge on a common brainstem efferent system, and that this system forms the final common pathway for abnormal startle responses of differing latency. The characteristics of this efferent system differ from those previously described in brainstem reticular reflex myoclonus, but are similar to those described in the normal auditory startle reflex in man. This suggests that the abnormal startle response in hyperekplexia, and the normal startle reflex represent pathological and physiological activity in the same brainstem efferent system.

New observations on the normal auditory startle reflex in man

The latency and pattern of muscle recruitment in the startle response elicited by unexpected auditory stimulation was determined in 12 healthy subjects. Reflex EMG activity was recorded first in orbicularis oculi. This was of similar latency to the normal auditory blink reflex and, unlike the generalized startle response, persisted despite the frequent presentation of the test stimulus. It is argued that this early latency activity in orbicularis oculi represents a normal auditory blink reflex and is not part of the generalized auditory startle reflex. With the exception of this early latency activity in orbicularis oculi, the relative latencies of both cranial and distal muscles in the auditory startle response increased with the distance of their respective segmental innervations from the caudal brainstem. Thus the earliest EMG activity was recorded in sternocleidomastoid. The recruitment of caudal muscles was relatively slow and the latencies of the intrinsic hand muscles were disproportionately long. The pattern of recruitment of cranial muscles suggests a brainstem origin for the normal startle response. Studies on the auditory startle reflex in animals are reviewed in the light of this finding.

Variability of cortically evoked motor responses in multiple sclerosis

The calculated central motor conduction time (CMCT), onset latency variability (expressed as the mean consecutive difference; MCD) and amplitude (expressed as percentage of maximum peripheral M wave size) of electromyographic (EMG) responses in the first dorsal interosseous (FDI) muscle following magnetic motor cortex stimulation were investigated in 20 normal subjects and 21 patients with multiple sclerosis (MS). EMG responses were present in all patients studied. CMCT was prolonged (greater than 8.1 msec; the mean CMCT for normals plus 3 S.D.) in 19 out of 42 muscles (12 patients). Onset latency variability was increased (greater than 1.1 msec; mean plus 3 S.D. for normals) in 20 out of 42 muscles (14 patients). Maximal response amplitudes varied between 5% and 67% and were not significantly different from the normal group (range 16-64%). In 3 patients, increased onset latency variability was the only neurophysiological abnormality. Prolonged CMCT was the sole abnormal finding in only 1 patient. Abnormally large onset latency variability was associated with the clinical finding of both impaired fine finger movements and increased finger jerks. Abnormal CMCT was associated with increased finger jerks only. This study confirms the findings of prolonged CMCT in multiple sclerosis. The additional finding of abnormal variability in response latencies which correlates with the clinical signs suggests that this variability may also be a useful measure of pyramidal tract function.

Central motor pathways in patients with mirror movements

Central motor pathways were investigated in three patients with congenital mirror movements using magnetic motor cortex stimulation. Response thresholds, amplitudes and latencies were normal. The projection of the corticomotoneuronal pathways was assessed by placing the coil over the vertex and comparing the size of responses in the first dorsal interosseous (FDI) muscles evoked by anticlockwise and clockwise [corrected] coil currents. In normal subjects, right FDI responses are larger with anticlockwise currents than with clockwise [corrected] currents at the same stimulation strength and vice versa. In two out of three patients with congenital mirror movements, this sensitivity of response amplitude to coil current direction was reversed. The third patient with congenital mirror movements and a fourth patient with acquired mirror movements had responses which were normally sensitive to current direction. These findings support the hypothesis that some cases of congenital mirror movements may be due to abnormal projection of corticomotoneuronal pathways.

Coil placement in magnetic brain stimulation related to skull and brain anatomy

The influence of coil position on the size of electromyographic responses evoked by transcranial magnetic brain stimulation was systematically evaluated. The position of the stimulation coil (11.6 cm outer diameter, Novametrix) was recorded by constructing individual grids on the skull surface using extracranial bony landmarks and was then related to underlying cerebral sulci by analysis of magnetic resonance images of the brain and skull. The largest responses in the right first dorsal interosseus (FDI) muscle, when using anticlockwise coil currents as viewed from above, were found, on average (5 subjects), to occur with the coil centred 2 cm behind and left of the vertex. For the right tibialis anterior (TA) muscle the largest responses were obtained, on average, with the coil centred around a point 4 cm anterior to and 4 cm left of the vertex. Between individuals, the optimal coil position for responses in a particular muscle varied up to 2 cm. This variability could be explained by the variability in the relationship between the central sulcus and the extracranial bony landmarks of each individual. Responses could be obtained whenever the windings of the coil passed over the appropriate region of the motor cortex, providing evidence that magnetically evoked responses do originate from activation of the precentral gyrus. The size of the cortically evoked responses for a given stimulus intensity depended on the direction of the coil currents passing over the motor area. For FDI muscles, the largest responses were obtained when the coil currents passed over the lateral part of the motor strip from forwards behind and transversely to the central sulcus.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal conduction in corticospinal pathways in Wilson's disease: investigation of nine cases with magnetic brain stimulation

Electromyographic (EMG) responses evoked by transcranial magnetic brain stimulation were studied in nine patients with Wilson's disease (WD). Six of the nine patients had prolonged central motor latencies (CMLs), reduced amplitude, or absent responses in at least one of the examined muscles. In one patient, abnormal EMG responses normalized following treatment with penicillamine. Pathophysiologically abnormal EMG responses might result from a potentially reversible impairment of corticomotoneuronal pathways and/or a reduced excitability of motoneurons due to basal ganglia dysfunction. The possible pathophysiological mechanisms are discussed.

Technical approaches to hemisphere-selective transcranial magnetic brain stimulation

Clinical application of transcranial magnetic brain stimulation is mainly used to determine central motor conduction times. With the stimulation coil (Magstim 200, Novametrix) centered conventionally over the midline of the skull convexity and using high stimulus intensities, which are often required in pathological states, the motor cortices of both hemispheres are usually activated simultaneously. Under this condition it is not possible to determine from which hemisphere the descending excitatory volleys to a particular motoneurone pool originate and how the input to the lower motoneurons is organized (uni-/bilateral, ipsi-/contralateral). This limitation can be overcome by two different techniques for selective stimulation of the motor cortex of one hemisphere without coactivation of the other even when using maximal stimulus intensities: 1. A large 12 cm (outer diameter) stimulation coil could be used for selective stimulation when a) the magnetic field radiated over the non-stimulated hemisphere is modified by using a prototype coil shield covering the half of the coil over the nonstimulated hemisphere in combination with b) placing the coil away from the midline towards the preferentially excited hemisphere. The coil shield consists of a sheet of a nickel iron alloy which alters the time course of the induced currents by reducing the initial rate of current intensity change (dI/dt). 2. The use of a smaller 6.5 cm (outer diameter) coil also provided a useful tool for selective stimulation of one hemisphere but was restricted to subjects with low excitation thresholds. In subjects with high excitation thresholds the described use of the large stimulation coil is advisable.

Clinical use of the magnetic stimulator in the investigation of peripheral conduction time

The application of rapidly changing magnetic fields (magnetic stimulation) over the neck or lower back elicits EMG responses in the muscles of the arm or leg respectively. Such responses have stable onset latencies but their amplitudes vary depending on the position of the coil over the neck or lower back. Supramaximal responses could not be obtained. Comparison of onset latencies with estimates of peripheral conduction time using a conventional F-wave technique suggest that the site of excitation of the motor axons is about 1.3 msec conduction time distal to the cervical motoneurons and 3 msec distal to the lumbosacral motoneurons. Response configuration after paravertebral magnetic stimulation was similar to that of the standard electrically evoked M-wave in the small hand muscles but not in lower limb muscles. Responses in lower limb muscles after paravertebral magnetic stimulation may consist of additional F-wave and H-reflex components. The possible clinical role of paravertebral magnetic stimulation in the investigation of peripheral and central motor pathways is discussed in the light of these findings.

Safety and efficacy of acetarsol suppositories in unresponsive proctitis

In a prospective open study, 10 patients with intractable proctitis were treated with acetarsol suppositories (250 mg b.d. for 4 weeks) and were monitored clinically, biochemically and toxicologically. Proctitis resolved symptomatically and sigmoidoscopically within 2 weeks in nine patients; one patient was unaffected. The only side-effect was of transient thrombocytosis in a single patient. Maximal blood and urinary arsenic concentrations occurred after 1 week's treatment with a total inorganic arsenic in the hazardous range in six patients; subsequent concentrations fell despite continuing therapy and at 4 weeks potentially hazardous values persisted in only two patients. Continued renal excretion and diminished absorption across an improved rectal mucosa is thought to be responsible for this paradox. Arsenic levels fell rapidly when acetarsol was withdrawn and were indistinguishable from pretreatment values within 4 weeks. Short-term acetarsol therapy offers a useful additional measure when local steroids have failed to control ulcerative proctitis; it appears to be safe and formal controlled comparisons with other therapeutic options are therefore legitimate.

The significance of plasma phytanic acid levels in adults

The presence of phytanic acid in tissues and plasma has been considered diagnostic of heredopathia atactica polyneuritiformis (Refsum's disease), but recently slightly raised plasma phytanic acid levels have been reported in other conditions. Forty two normal people were found to have a phytanic acid level of 0-33 mumol/l. Fourteen patients with heredopathia atactica polyneuritiformis had a plasma phytanic acid level before treatment of 992-6400 mumol/l. Five patients with retinitis pigmentosa but not heredopathia atactica polyneuritiformis had plasma levels of 38-192 mumol/l. It was concluded that some patients with retinitis pigmentosa without heredopathia atactica polyneuritiformis but a raised plasma phytanic acid may represent a group of patients with a disease or diseases as yet uncharacterised apart from the retinal condition.

Investigation of unilateral facial weakness: magnetic stimulation of the proximal facial nerve and of the face-associated motor cortex

Twenty-four patients with unilateral facial weakness of various aetiologies were investigated using a magnetic stimulator to stimulate the proximal segment of the facial nerve directly (short latency response) and also to activate the facial motoneurons bilaterally via corticonuclear pathways by placing the stimulating coil over the motor cortex (long latency responses). Electromyographic recordings were taken from both mentalis muscles using concentric needle electrodes. Seventeen patients were investigated at various times after onset of idiopathic facial palsy (Bell's palsy). In the acute stage (less than 5 days after onset) short and long latency responses on the paretic side were abnormal, being absent in all but one patient, in whom the short latency response was delayed. These abnormal responses were the earliest neurographic correlate for nerve conduction block. In 4 out of 9 patients seen up to 30 days after onset of palsy, trans-synaptically evoked long latency responses were absent. In patients examined more than 2 months after onset, long latency responses could always be obtained and, in 5 of 8 patients, short latency responses could also be elicited, indicating a return of the direct excitability of the nerve. Five patients with cerebral hemisphere lesions causing mild unilateral facial weakness had absent long latency responses when stimulating over the affected hemisphere, but normal bilateral long latency responses following stimulation over the unaffected cerebral hemisphere; short latency responses were normal. Magnetic stimulation of the brain and of the facial nerve can differentiate between central and peripheral causes of unilateral facial weakness and may prove useful in the early assessment of the degree of conduction block in Bell's palsy.