Respiratory disturbances during sleep in syringomyelia and syringobulbia

Past, present, and future of sleep medicine research in Latin America

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Sleep medicine is a relatively young field with exponential growth in development and research in the last decades. Parallel to the advances in the United States, Latin America also had its beginnings in sleep medicine housed in neuroscience laboratories. Since the very first Latin American meeting in 1985, and the first sleep society in 1993, sleep research has undergone significant development in subsequent years. From contributions in animal research that allowed understanding of the activity of the brain during sleep to the studies that improved our knowledge of sleep disorders in humans, Latin America has become a scientific hub for expansion of sleep research. In this article, we present a historical account of the development of sleep medicine in Latin America, the current state of education and the achievements in research throughout history, and the latest advances in the trending areas of sleep science and medicine. These findings were presented during World Sleep Society meeting in Vancouver in 2019 and complement the work on sleep societies and training published by Vizcarra-Escobar et al in their article "Sleep societies and sleep training programs in Latin America" (J Clin Sleep Med. 2020;16(6):983-988).

Stridor during sleep: description of 81 consecutive cases diagnosed in a tertiary sleep disorders center

Study Objectives

To describe the characteristics of stridor during sleep (SDS) in a series of adults identified by video-polysomnography (V-PSG).

Methods

Retrospective clinical, V-PSG, laryngoscopic, and therapeutic data of patients diagnosed with SDS in a tertiary referral sleep disorders center between 1997 and 2017.

Results

A total of 81 patients were identified (56.8% males, age 61.8 ± 11.2 years). Related etiologies were multiple system atrophy (MSA), amyotrophic lateral sclerosis, spinocerebellar ataxia type 1, anti-IgLON5 disease, fatal familial insomnia, brainstem structural lesions, vagus nerve stimulation, recurrent laryngeal nerve injury, the effect of radiotherapy on the vocal cords, cervical osteophytes, and others. Stridor during wakefulness coexisted in 13 (16%) patients and in MSA was only seen in the parkinsonian form. Laryngoscopy during wakefulness in 72 (88.9%) subjects documented vocal cord abductor impairment in 65 (90.3%) and extrinsic lesions narrowing the glottis in 2 (2.4%). The mean apnea–hypopnea index (AHI) was 21.4 ± 18.6 and CT90 was 11.5 ± 19.1. Obstructive AHI > 10 occurred in 52 (64.2%) patients and central apnea index >10 in 2 (2.4%). CPAP abolished SDS, obstructive apneic events and oxyhemoglobin desaturations in 58 of 60 (96.7%) titrated patients with optimal pressure of 9.0 ± 2.3 cm H20. Tracheostomy in 19 (23.4%) and cordotomy in 3 (3.7%) subjects also eliminated SDS.

Conclusions

SDS in adults is linked to conditions that damage the brainstem, recurrent laryngeal nerve, and vocal cords. V-PSG frequently detects obstructive sleep apnea and laryngoscopy usually shows vocal cord abductor dysfunction. CPAP, tracheostomy, and laryngeal surgery abolish SDS.

Syringobulbia: A delayed complication following spinal cord injury - case report

CONTEXT

Syringobulbia is a very rare progressive disorder of central nervous system, with several possible underlying conditions. Rarely, it is also encountered as a late complication of syringomyelia.

FINDINGS

In the present manuscript, a case of a paraplegic patient, due to traumatic spinal cord injury (thoracolumbar fracture), presenting after years progressively developing symptoms of the lower cranial nerves and upper extremities, owed to syringomyelia and syringobulbia, the surgical treatment applied and its outcomes are described. We performed a syringo-peritoneal shunting procedure using a T-tube. The patient's symptoms resolved postoperatively and the cavity's size was reduced to a great degree.

CONCLUSION/CLINICAL RELEVANCE

The late appearance of cranial nerve deficits or symptoms-signs of the upper extremities in a patient with traumatic thoracic spinal cord injury should raise suspicion that post-traumatic syringomyelia or syringobulbia has occurred. In such cases, radiologic evaluation and early surgical drainage of the cyst as a means of preventing significant delayed neurologic deficit is advocated.

Surgical Management and Risk Factors of Postoperative Respiratory Dysfunction of Cavernous Malformations Involving the Medulla Oblongata

OBJECTIVE

To evaluate surgical management of cavernous malformations (CMs) involving the medulla oblongata and to predict risk factors of postoperative respiratory dysfunction (RDF).

METHODS

Patient data from individuals who underwent surgical treatment for CMs involving the medulla oblongata were retrospectively reviewed. Patients with postoperative RDF and/or deficits of the cough reflex (CR, ≥7 days) were deemed as having bad respiratory statuses. A binary logistic regression analysis tested the association of preoperative predictors with bad postoperative respiratory status.

RESULTS

The study consisted of 69 patients. Preoperatively, 9 patients (13.0%) had dyspnea, and 4 (5.8%) had hypoxemia. Postoperatively, 11 patients (15.9%) had bad respiratory statuses, including RDF as a respiratory rhythm disorder and/or dyspnea in 6 patients, and ≥7 days of CR deficits in 5 patients. With a mean follow-up duration of 35.3 months, the neurologic status improved in 45 patients (68.2%), remained unchanged in 11 (16.7%), and worsened in 10 (15.1%) relative to the preoperative baseline. A multivariate logistic regression analysis identified that the independent adverse factors of bad postoperative respiratory status were multiple preoperative hemorrhages, large lesion size, and surgical intervention during the chronic period (>8 weeks).

CONCLUSIONS

Postoperative RDF and CR deficits could commonly occur in patients with CMs involving the medulla oblongata. However, patients with fewer preoperative hemorrhages, small lesion size, and operation within 8 weeks of the last bleeding are prone to be associated with a reduced possibility of bad postoperative respiratory status.

Obstructive sleep apnoea associated with syringomyelia

Coexistence of obstructive sleep apnoea and syringomyelia is quite rare. This article discusses three cases of coexisting obstructive sleep apnoea and syringomyelia and looks at the possible mutual influences between the two diseases.

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.

Unilateral ablation of pre-Botzinger complex disrupts breathing during sleep but not wakefulness

RATIONALE

In adult rats, bilateral ablation of pre-Bötzinger complex (preBötC) neurokinin 1-expressing (NK1R) neurons leads to a progressive and irreversible disruption in breathing pattern, initially during sleep, eventually resulting in an ataxic breathing pattern during wakefulness.

OBJECTIVES

Here we determine whether ablation of fewer preBötC NK1R neurons leads to a persistent pattern of disordered breathing during sleep but not during wakefulness.

METHODS

Adult male Sprague-Dawley rats (n = 12) were instrumented to record diaphragmatic, abdominal, and neck EMG, and EEG. Fourteen days later, a second surgery was performed to stereotaxically microinject into the preBötC on one side the toxin saporin conjugated to substance P (SP-SAP), which selectively ablates NK1R neurons.

MEASUREMENTS AND MAIN RESULTS

Postinjection, rats were monitored within a plethysmograph until they were killed (Days 21-51). At Days 6-9 post-unilateral SP-SAP injection, respiratory pattern during sleep, particularly REM sleep, became increasingly disordered, characterized by an increase in frequency of central sleep apnea and hypopneas (36.8 +/- 7.4 episodes/h of REM vs. 6 +/- 2.0 episodes/h in preinjection controls; P < 0.05), whereas breathing during resting wakefulness remained stable. Unlike bilateral SP-SAP-injected rats, an ataxic breathing pattern did not develop during wakefulness. Rats that were monitored up to 51 days post-SP-SAP injection continued to have sleep-disordered breathing; breathing during wakefulness remained relatively stable. Histologic analysis of the ventrolateral medulla confirmed that NK1R neurons within the preBötC on the injected but not on the contralateral side of the medulla were ablated.

CONCLUSIONS

Gradual loss of preBötC NK1R neurons may be an underlying factor of sleep-disordered breathing, in particular of central sleep apnea.

Brainstem respiratory control: substrates of respiratory failure of multiple system atrophy

Multiple system atrophy may manifest with severe respiratory disorders, including sleep apnea and laryngeal stridor, which reflect a failure of automatic control of respiration. This function depends on a pontomedullary network of interconnected neurons located in the parabrachial/Kölliker Fuse nucleus in the pons, nucleus of the solitary tract, and ventrolateral medulla. Neurons in the preBötzinger complex expressing neurokinin-1 receptors are critically involved in respiratory rhythmogenesis, whereas serotonergic neurons in the medullary raphe and glutamatergic neurons located close to the ventral medullary surface are involved in central chemosensitivity to hypercapnia, hypoxia, or both. Pathological studies using selective neurochemical markers indicate that these neuronal groups are affected in multiple system atrophy. This finding may provide potential anatomical substrates for the respiratory manifestations of the disease.

Neuromuscular disorders and sleep

Neuromuscular disorders are caused by the primary involvement of the motor unit. In these patients, sleep-disordered breathing (SDB) due to respiratory muscle weakness is often encountered during sleep. Because there is a tendency to overlook this disorder, all patients with neuromuscular disorders should be questioned about SDB. Overnight polysomnography is the best investigation for SDB and nocturnal desaturations. In the management of these patients, noninvasive intermittent positive pressure ventilation results in improvement of SDB and breathing.

Characteristics of sleep apnea syndrome in tetraplegic patients

OBJECTIVE

To include a larger number of tetraplegics than in previous studies, in order to more reliably characterize the pathogenesis and predisposing factors of sleep apnea in tetraplegia.

METHODS

Sleep breathing data and oxymetric values were investigated in 50 randomly selected tetraplegic patients and discussed in context with age, gender, BMI, neck circumference, type and height of lesion, time after injury, spirometric values and medication. A non-validated short questionnaire on daytime complaints was added.

RESULTS

Thirty-one patients out of 50 had an RDI > or =15, defined as sleep disordered breathing (SDB); 24 of them combined with an apnea index of 5 or more, these cases were diagnosed as sleep apnea syndrome (SAS). SAS was apparent in 55% and 20% of the studied men and women, respectively. Regression analyses showed no significant correlation between RDI and lesion level, ASIA impairment scale or spirometric values. In contrast, a significant correlation between RDI and age, BMI, neck circumference and time after injury could be shown. Kruskal-Wallis test for dichotomous non-parametric factors, such as gender, cardiac medication and daytime complaints, showed significant differences with regard to RDI. In contrast to able-bodied people with SAS, daytime complaints were only present in tetraplegic patients with severe pathology (RDI>40).

CONCLUSION

Incidence of SAS is high in tetraplegia, particularly in older male patients with large neck circumference, long standing spinal cord injury and under cardiac medication. As tetraplegics with RDI between 15 and 40 reported no daytime complaints and often have normal BMI, these tetraplegics are not clinically suspicious for SAS. The increased use of cardiac medication in tetraplegics with SAS may implicate a link between SAS and cardiovascular morbidity, one of the leading causes of death in tetraplegia.

Syringomyelia with syringobulbia presenting only with paralysis of 9th and 10th cranial nerves

We report a case of syringomyelia with syringobulbia, in a patient who presented only with involvement of the 9th and 10th cranial nerves.

Postural tachycardia syndrome in syringomyelia: response to fludrocortisone and beta-blockers

Orthostatic intolerance is occasionally reported by patients with syringomyelia and is usually attributed to vestibular symptoms or neurogenic orthostatic hypotension. Postural tachycardia syndrome has not been previously described in syringomyelia. A patient with long-standing syringomyelia and a Chiari type I anomaly developed disabling "panic-like" attacks associated to orthostatic intolerance five years after posterior fossa decompression and shunting of the syrinx. A head-up tilt test showed an early phase of postural orthostatic tachycardia followed by progressive arterial hypotension and bradycardia as seen in neurally mediated syncope. A magnetic resonance imaging scan showed a collapsed syrinx from the 3rd cervical to the 12th thoracic vertebra without syringobulbia. Fludrocortisone and beta-blockers led to resolution of symptoms. Partial sympathetic denervation of the legs in syringomyelia might explain the occasional occurrence of postural tachycardia syndrome. Postural tachycardia syndrome may be included as a possible cause of orthostatic symptoms in syringomyelia patients.