Martin Nogues

Acute CNS infection by Trypanosoma cruzi (Chagas' disease) in immunosuppressed patients

Acute CNS involvement by Trypanosoma cruzi is uncommon. We report 2 immunosuppressed patients, 1 adult who developed an acute meningoencephalitis, and 1 child who presented with the tumor-like form of the disease. Both patients acquired the disease through blood transfusion. Blood donors migrating from endemic areas can transmit the disease in nonendemic countries if they are not routinely screened for antibodies to T cruzi.

Heart rate variability response to mental arithmetic stress in patients with schizophrenia: Autonomic response to stress in schizophrenia

BACKGROUND The vulnerability-stress hypothesis is an established model of schizophrenia symptom formation. We sought to characterise the pattern of the cardiac autonomic response to mental arithmetic stress in patients with stable schizophrenia. METHODS We performed heart rate variability (HRV) analysis on recordings obtained before, during, and after a standard test of autonomic function involving mental stress in 25 patients with DSM-IV schizophrenia (S) and 25 healthy individuals (C). RESULTS Patients with schizophrenia had a normal response to the mental arithmetic stress test. Relative contributions of low-frequency (LF) HRV and high-frequency (HF) HRV influences on heart rate in patients were similar to controls both at rest (LF 64+/-19% (S) vs. 56+/-16% (C); HF 36+/-19% (S) vs. 44+/-16% (C), t=1.52, p=0.136) and during mental stress, with increased LF (S: 76+/-12%, C: 74+/-11%) and decreased HF (S: 24+/-12%, C: 26+/-11%) in the latter study condition. Whilst healthy persons recovered the resting pattern of HRV immediately after stress termination (LF 60+/-15%, HF 40+/-15%, F=18.5, p<0.001), in patients HRV remained unchanged throughout the observed recovery period, with larger LF (71+/-17%) and lower HF (29+/-17%) compared with baseline (F=7.3, p=0.013). CONCLUSIONS Patients with schizophrenia exhibit a normal response to the mental arithmetic stress test as a standard test of autonomic function but in contrast with healthy individuals, they maintain stress-related changes of cardiac autonomic function beyond stimulus cessation.

Involuntary movements and abnormal spontaneous EMG activity in syringomyelia and syringobulbia

Objective: To describe different types of involuntary movements and abnormal spontaneous electromyographic (EMG) activity in patients with syringomyelia. Background: A comprehensive study on involuntary movements in patients with syringomyelia has not yet been undertaken, to these authors’ knowledge. Methods: One hundred adult patients with syringomyelia were examined over the last 15 years. Involuntary movements were videotaped and evaluated by two independent observers. Electromyographic recordings were made using bipolar surface electrodes. The H-reflex recovery curve was obtained after stimulation of the median nerve at the elbow and recording from the flexor carpi radialis. Results: Involuntary movements or abnormal postures were observed in 22 patients. Three patients showed segmental spinal myoclonus, nine minipolymyoclonus, and four propriospinal myoclonus. Five patients had unilateral or bilateral hand postural tremor (8–10 Hz). Focal or segmental dystonia was observed in three patients. Electromyography showed spontaneous bursts of grouped action potentials synchronous in muscles innervated by the same spinal segment, synchronous firing of neurogenic motor unit potentials, or continuous motor unit activity. Increased H-reflex responses to conditioning stimuli were found in patients with spinal myoclonus. Long latency responses were obtained during peripheral nerve stimulation in four patients. Four patients had rigidity and abnormal upper limb posture. Respiratory synkinesis was observed in three patients. One patient developed inverse masticatory muscle activity. Conclusions: Patients with syringomyelia showed a wide spectrum of involuntary movements. An increased excitability of spinal motor neurons was probably the basic underlying mechanism.

Limb-kinetic apraxia in corticobasal degeneration: clinical and kinematic features.

Current concepts regarding the organisation of the motor system indicate the existence of a frontoparietal circuit involved in prehension and manipulation, whose damage may result in a motor behavioural disorder strongly resembling the one originally described as limb‐kinetic apraxia. To determine the specific clinical and kinematic features of this distinctive praxic disorder, 5 patients with corticobasal degeneration (apraxic group), 5 with Parkinsons disease (nonapraxic group), and 10 control subjects were studied by a comprehensive apraxic battery, three‐dimensional motion analysis of manipulative movements and motor evoked potentials. A mathematical model [quality of movement coefficient (QMC)] was applied to quantify differential kinematic characteristics between elementary motor deficits and the praxic disorder. Transcranial magnetic stimulation was used to evaluate corticomotoneural projections and cortical inhibition. All five patients in the apraxic group exhibited a unilateral praxic deficit characterised by derangement of fractionated and segmental finger movements. QMC was significantly greater in apraxic than in nonapraxic patients (P < 0.02), revealing a chaotic movement with marked interfinger uncoordination. Conventional transcranial magnetic stimulation parameters were within normal limits in both groups of patients; however, the silent period was significantly shorter in the apraxic limb when compared with control subjects (P < 0.001). Limb‐kinetic apraxia is a distinctive disorder affecting the performance of finger and hand postures and movements over and above a corticospinal or basal ganglion deficit. Disruption of the frontoparietal circuit devoted to grasping and manipulation, together with defective cortical inhibition, which would also interfere with the selection and control of hand muscle activity, are the most likely underlying physiopathological mechanisms of limb‐kinetic apraxia in patients with corticobasal degeneration.

Periodic limb movements in syringomyelia and syringobulbia.

Twenty‐six patients with syringomyelia were studied with polysomnography to determine the frequency of periodic limb movements (PLM) and its relationship to the presence of a Chiari anomaly, the severity of corticospinal tract involvement, and localization of the syrinx. Sixteen patients showed PLM in stages I and II of non‐REM sleep and three PLM also while awake. There were no statistically significant differences in overall disability, corticospinal signs, presence of an associated Chiari anomaly, and disease duration between patients with and without PLM, although there was a trend for patients with PLM to have more severe disease. There was preservation of the lumbosacral enlargement of the spinal cord by the syrinx in all patients with PLM. The latency delay between lower and upper limb muscles was suggestive of conduction along propriospinal pathways. Syringomyelia may lead to an abnormal state of spinal hyperexcitability favoring the appearance of PLM. Detailed magnetic resonance image studies of patients with different localizations of the syrinx cavities may help to determine which tracts are involved in the production of PLM.

Breathing control in neurological diseases

Abstract. Control of ventilation depends on a brainstem neuronal network that controls activity of the motor neurons innervating the respiratory muscles. This network includes the pontine respiratory group and the dorsal and ventral respiratory groups in the medulla, which contain neurons that fire primarily during inspiration, post-inspiration, or expiration. The ventral respiratory group includes the pre-Bötzinger complex, which contains neurokinin-1 receptor immunoreactive neurons critical for respiratory rhythmogenesis. Structural and degenerative disorders affecting this network produce abnormalities of respiration, including sleep apnea and various patterns of dysrhythmic breathing, not infrequently associated with disturbances of cardiovagal and sympathetic vasomotor control. This emphasizes the important interactions between the respiratory and cardiovascular control networks in the medulla. Common disorders associated with impaired cardiorespiratory control include brainstem stroke or compression, syringobulbia, Chiari malformation, high cervical spinal cord injuries, and multiple system atrophy. This review focuses on the functional organization of the respiratory control network and common causes of impaired control of respiration.

Respiratory disturbances during sleep in syringomyelia and syringobulbia

Objective: To determine the frequency and types of abnormalities of respiratory control during sleep in syringomyelia and syringobulbia and to provide a basis to predict patients at risk of sudden death. Methods: Thirty patients (15 male and 15 female; mean age 39.0 ± 12.6 years) with communicating syringomyelia were divided into two groups: those with evidence of syringobulbia (17 patients) and those without compromise of the medulla or syringomyelia (13 patients). Patients were studied with pulmonary function studies and polysomnography. Respiratory center sensitivity to CO2 (rebreathing technique) was measured in 9 patients. Results: Severely affected patients had mild-to-moderate restriction and individual patients had bilateral diaphragmatic or vocal cord palsy, abnormal respiratory rhythm, prolonged inspiratory time, or an abnormal respiratory response to CO2. Very prolonged central, obstructive, and mixed sleep apneas with low O2 saturation values and a fixed heart rate were recorded in most patients with syringobulbia. Five patients developed severe respiratory complications and died during a follow-up period of 10 years. Respiratory abnormalities failed to correlate with syrinx size. Conclusions: Severe abnormalities in respiratory rhythm generation during sleep occur in patients with syringobulbia. The respiratory disturbances are not due to muscle weakness and they are not correlated with the size of the cavity. The combination of dysphagia and dysphonia in patients with longstanding syringomyelia and syringobulbia predicted likelihood of respiratory disturbances during sleep.

Abnormalities of respiratory control and the respiratory motor unit.

Background:Control of ventilation depends on a brainstem neuronal network that controls activity of the motor neurons innervating the respiratory muscles. This network includes the pontine respiratory group and the dorsal and ventral respiratory groups in the medulla. Neurologic disorders affecting these areas or the respiratory motor unit may lead to abnormal breathing. Review Summary:The brainstem respiratory network contains neurons critical for respiratory rhythmogenesis; this network receives inputs from peripheral and central chemoreceptors sensitive to levels of carbon dioxide (PaCO2) and oxygen (PaO2) and from forebrain structures that control respiration as part of integrated behaviors such as speech or exercise. Manifestations associated with disorders of this network include sleep apnea and dysrhythmic breathing frequently associated with disturbances of cardiovagal and sympathetic vasomotor control. Common disorders associated with impaired cardiorespiratory control include brainstem stroke or compression, syringobulbia, Chiari malformation, high cervical spinal cord injuries, and multiple system atrophy. By far, neuromuscular disorders are the more common neurologic conditions leading to respiratory failure. Conclusions:Respiratory dysfunction constitute an early and relatively major manifestation of several neurologic disorders and may be due to an abnormal breathing pattern generation due to involvement of the cardiorespiratory network or more frequently to respiratory muscle weakness.

Depressive symptoms are related to decreased low-frequency heart rate variability in older adults with decompensated heart failure.

Background/Aims: Depression has been associated with increased mortality among individuals with heart failure, but the mechanism for this association is unsettled. Depression is often found to result in autonomic dysfunction which, if present in heart failure, might help explain worsened outcomes. Methods: This study was a cross-sectional evaluation of the relationship between depressive symptoms and cardiac autonomic function, as assessed by short-term heart rate variability (HRV) analysis in aged patients with acute/decompensated heart failure of coronary origin (CHF). A 21-item Hamilton Depression score and measures of short-term HRV were obtained in 31 inpatients ≧65 years of age, 24–72 h after admission to the coronary care unit with a diagnosis of CHF. Results: Clinical depression was present in 22.6% of participants. In the sample as a whole, increasing depressive symptoms were associated with decreased low-frequency HRV. Conclusion: These results may be important in light of recent indications that decreased low-frequency HRV is a predictor of mortality in patients with heart failure.

Disruption of spatial organization and interjoint coordination in Parkinson's disease, progressive supranuclear palsy, and multiple system atrophy

Patients with basal ganglia diseases may exhibit ideomotor apraxia. To define the nature of the impairment of the action production system, we studied a repetitive gesture of slicing bread by three‐dimensional computergraphic analysis in eight nondemented patients with Parkinsons disease in the “on” state, five with progressive supranuclear palsy and four with multiple system atrophy. Two patients with Parkinsons disease and two with progressive supranuclear palsy showed ideomotor apraxia for transitive movements on standard testing. A Selspott II system was used for kinematic analysis of wrist trajectories and angular motions of the shoulder and elbow joints. Patients with Parkinsons disease, progressive supranuclear palsy, and even some with multiple system atrophy exhibited kinematic deficits in the spatial precision of movement and velocity‐curvature relationships; in addition, they failed to maintain proper angle/angle relationships and to apportion their relative joint amplitudes normally. Spatial disruption of wrist trajectories was more severe in patients with ideomotor apraxia. We posit that the basal ganglia are part of the parallel parieto‐frontal circuits devoted to sensorimotor integration for object‐oriented behavior. The severity and characteristics of spatial abnormalities of a transitive movement would therefore depend on the location and distribution of the pathologic process within these circuits.