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15.1 Introduction

Chiari malformations, with or without an associated syrinx, as well as syringomyelia from other causes, are frequently first diagnosed in women of a childbearing age. Consequently, many such patients develop justifiable concerns with respect to pregnancy, labour and delivery (Table 15.1). Thoughts about starting a family may also raise questions about possible inheritance of the condition, and genetic aspects of Chiari are therefore covered within Chap. 5 of this monograph. Chiari malformation is also one of the central nervous system abnormalities that can be diagnosed with confidence in the prenatal period, and ultrasonography may be used if there is particular concern about the unborn child, on the part of the mother or the obstetrician (Bianchi et al. 2000; Iruretagoyena et al. 2010).

Table 15.1 Common concerns about Chiari and syringomyelia that arise during pregnancy
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15.2 Pathophysiology

Symptoms of Chiari develop as a result of compression of the medulla and upper spinal cord and disturbance of cerebrospinal fluid (CSF) flow through foramen magnum. The typical Chiari headache is an intense occipital pain or a more generalised, ‘explosive’ headache, usually triggered by Valsalva-like manoeuvres such as coughing or physical activity. A study of 19 Chiari I patients analysed the triggers of their headaches: ten suffered from headaches lasting an average of 11 min, brought on by coughing, sneezing, laughing, sexual activity or other physical efforts. Eight patients had classical occipital headaches but six described frontal pain (Martins et al. 2010).

The pathophysiology of these symptoms probably centres on the pressure differences between the spine and intracranial compartments that come about during and immediately after Valsalva manoeuvres. The possible mechanisms by which disordered flow of CSF through the foramen magnum results in formation of syringomyelia cavities are discussed in Chap. 6. The pathophysiology of Chiari II is likely to be more complex than with Chiari I, but similar mechanisms are likely to operate in the generation of symptoms, although the additional effect of hydrocephalus , in further exacerbating the downward displacement of brainstem structures, has to be borne in mind.

15.3 Valsalva

When a person carries out moderately forceful exhalation against a closed airway (Valsalva manoeuvre), the resultant rise in intrathoracic pressure affects venous return, cardiac output, arterial pressure and heart rate. These effects can occur when the thoracic and abdominal muscles are strongly contracted, such as when a person strains while having a bowel movement or when lifting a heavy weight. Both actions are usually accompanied by involuntary breath holding. The normal physiological response in Valsalva occurs in clear phases. An initial rise in intrathoracic pressure forces blood out of the pulmonary circulation and into the left atrium. At the same time return of systemic blood to the right atrium is impeded. As a consequence the cardiac output is reduced and stroke volume falls. When forced exhalation ceases the pressure on the chest is released, allowing the major intrathoracic vessels to re-expand. Venous blood can also once more enter the heart and exit into these vessels and so cardiac output increases. The pressure changes have a direct effect, positive and negative, on the pressures and blood flow in the unvalved spinal and cerebral venous structures.

During labour, pushing down involves a series of particularly prolonged Valsalva manoeuvres. An inevitable concern, therefore, is whether or not labour might aggravate or complicate the anatomy or pathophysiology of a Chiari and/or an associated syrinx cavity. Theoretically, at worst, there is a potential risk of brainstem compression from forced impaction of the tonsils. At the very least, pressure rises might be expected to aggravate any preexisting symptoms, and they might even cause deterioration in the patient’s neurological state. Spinal or epidural anaesthetics could also introduce new variables into the events of labour for Chiari or syringomyelia patients (Nel et al. 1998). The concerns relate to possible dural puncture and then CSF egress and also physical and pressure alterations in the epidural compartment. Abnormal CSF pressures might influence the effectiveness of the anaesthetic. Inadvertent or intended puncture, in the case of a spinal anaesthetic, of the lumbar theca might, in turn, affect intracranial or intraspinal pressures.

15.4 Effects of Pain

In addition to the effects of Valsalva, both the uterine contractions and the pain that they generate are also likely to increase CSF pressure, both inside the cranium and the spinal canal. Measuring the CSF pressure in normal patients during labour has revealed considerable elevations when pain is intense. Pressures may be as high as 70 cm H2O, which is more than three times the upper limit of normal (Mueller and Oro 2005).

15.5 Uncertainties

Yet, despite the recognition that syringomyelia and Chiari symptoms, in particular headaches, get worse with straining and exertion, we know relatively little about the consequences of pregnancy, labour and delivery, in terms of precipitation, worsening or even improvement of maternal symptoms and signs. Nor do we know whether or not a sudden or repeated episodes of a ‘high venous pressure’ event can cause the formation of a syrinx in the first place, but there are clear episodes in some patient’s clinical histories where this may be considered to have been possible, and such episodes may certainly be considered to have possibly aggravated a preexisting syrinx state if La Place’s law is operative. There is, however, no report of such events occurring during pregnancy, labour or delivery.

There is, unfortunately, very little literature and virtually no research to guide either the patients or their obstetricians and anaesthetists on the appropriate management of the Chiari or syringomyelia during pregnancy and labour. Reliable scientific data on the consequences, or potential interactions, of the physiological or interventional events occurring during pregnancy and labour are not available. There is no clear guidance at all in the literature, whether from large studies or case reports which specifically highlight or clearly identify common or uniform problems or pathological sequelae with a normal, or assisted, vaginal delivery and the use of epidural or intrathecal anaesthesia in patients with Chiari or syringomyelia. Nor, indeed, has there been any evidence to demonstrate increased safety or benefit conferred on pregnant mother with these conditions, by employing a Caesarean section .

Neurosurgeons are, nevertheless, frequently asked to advise on what is the best or safest mode of delivery for Chiari and syringomyelia patients. Is a vaginal delivery safe or is a Caesarean section necessary? Is a ‘supported’ delivery, with an epidural, or possibly even a spinal anaesthetic, permissible?

15.6 Literature Review

Women who are diagnosed with Chiari sometimes report that previous pregnancies or births first triggered the onset of their symptoms, or made them worse. One large series of 364 Chiari patients reported 16 female patients who identified pregnancy as an event precipitating their symptoms (Milhorat et al. 1999). Some women, already diagnosed with Chiari, reported that their symptoms became slightly worse during the pregnancy but then resolved spontaneously and fairly quickly after delivery. A further paradox is that in some cases patients’ symptoms actually got better during the pregnancy, for periods at least (Mueller and Oro 2005). Equally, many women, when first diagnosed with Chiari, have already completed pregnancies successfully without having experienced any aggravation of their symptoms.

What publications exist on this subject consist mainly of single case reports, without detailed reference or scientific justification for decisions taken and advice given. There are reports of women with Chiari or syringomyelia undergoing elective Caesarean sections (Castello et al. 1996; Daskalakis et al. 2001), the stated reason for this management decision being the fear that the straining and pushing during delivery would aggravate the Chiari or syringomyelia state One of the earliest reports of Chiari or syringomyelia ‘complicating’ pregnancy and delivery was that of a woman who presented with worsening of her neurological symptoms and who went on to have a Caesarean section (Baker and Stoll 1948). Other published case studies have concluded that, with ‘proper’ management, a normal uncomplicated delivery is possible, without aggravating Chiari or syringomyelia symptoms. Unfortunately, in these different reports, ‘proper’ varied from a normal vaginal delivery to an elective Caesarean section. Vaginal delivery in a Chiari patient has certainly been documented (Parker et al. 2002), and, clearly, it is unlikely that this report represents the first or only patient who has been managed in this way. Indeed, an earlier case was of a woman who underwent a successful operative vaginal delivery, without voluntary maternal expulsive efforts; there were no adverse consequences. A more recent case report was of the successful vaginal delivery, under epidural anaesthesia, in a mother who had Chiari and sickle cell anaemia (Newhouse and Kuczkowski 2007). In another study, of twelve mothers, delivering thirty babies in total, three underwent Caesarean section. Six deliveries were facilitated with epidural anaesthesia and three with spinal anaesthetic (Chantigian et al. 2002). In another group of six patients, only one had a Caesarean section, this under intrathecal anaesthesia. Another two of these six women had epidural anaesthesia for delivery, with no reported related symptoms (Mueller and Oro 2005). A further questionnaire, sent two of seven women with Chiari, who had all completed their pregnancies, revealed that four mothers had received an epidural anaesthetic and that six had undergone vaginal deliveries. There were no Chiari-related complications during delivery. Five women, however, had benefited from foramen magnum decompressive surgery before their vaginal delivery.

15.7 Recommendations

Unfortunately, even when all reports are combined, the number of cases commented upon is still too few for us to be able to draw definitive conclusions (Chantigian et al. 2002; Mueller and Oro 2005). Based on what literature there is, there appears to be no convincing evidence that vaginal delivery aggravates a syringomyelia or Chiari state. We can draw reassurance from the case reports of patients with untreated Chiari or syringomyelia who have delivered vaginally without any complications or concerns.

Despite this, when faced with the question of delivery management in Chiari or syringomyelia patients, most neurosurgeons have usually tended to ‘play safe’ and recommended a Caesarean section. Even so, patients should at least have been given the benefit of a full discussion, with their obstetrical team, neurosurgeon or neurologist, as to the benefits of a section, as against a normal vaginal delivery. Clearly, if the patient with Chiari or syringomyelia develops worsening neurological symptoms during a trial of normal vaginal delivery, then moving on to a Caesarean section may well be the safest and quickest route to follow.

There is no evidence to suggest that a patient who has previously undergone an adequate decompression of a Chiari malformation is in a situation different from that of a ‘normal’ patient and that she cannot or should not have a normal vaginal delivery. If the foramen magnum has been adequately decompressed in a patient with Chiari, and any associated syringomyelia cavity has subsequently collapsed, there is no reason to avoid a normal vaginal delivery or to impose a Caesarean section upon this mother.

There is no evidence to generate anxiety concerning the use of an epidural anaesthetic during labour. A spinal anaesthetic, with its dural breach and resultant changes in CSF pressure, might at first appear to be inadvisable on the grounds that it could aggravate the craniospinal pressure dissociation in a patient with an untreated Chiari malformation (Nel et al. 1998). The method has, however, been employed without complication in a patient with a corrected Chiari (Landau et al. 2003).

15.8 Summary

All in all, in considering this topic at this time, it is clear that important data elements are missing and there is obviously scope for future research (Table 15.2). This information should not prove impossible to collate, and it constitutes essential data, if rational and scientific recommendations are to be made, to aid patients with Chiari or syringomyelia and to advise obstetricians and midwives with respect to pregnancy and labour. At present, however, in terms of providing general advice, we can suggest the following guidelines:

Table 15.2 Missing data elements regarding mothers with Chiari and/or syringomyelia
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  • In patients with proven and untreated Chiari malformation, with or without syringomyelia, and in cases of syringomyelia from other causes, care should be taken to avoid any factor that may significantly elevate intracranial or intrathecal pressure.

  • In this regard the importance of pain in labour, as a cause of considerable increases in CSF pressure, should be borne in mind. Effective pain management would appear to be important in reducing CSF pressure. There is, however, no evidence to favour general over regional anaesthesia for pain relief.

  • No uniform recommendations are possible with respect to a particular mode of delivery as there is no current scientific or literature support to indicate that any mode of delivery, in terms of Chiari or syringomyelia, treated or untreated, is safer or less likely to cause harm than another.

  • Decisions made should therefore be interdisciplinary and inclusive of all the parturition practitioners – obstetrician, neurosurgeon and/or neurologist, anaesthetist and midwife – and in full discussion with the patient. Discussions should accurately reflect and recognise the current, limited state of knowledge on this subject.

  • The mother who develops, during pregnancy or delivery, severe Valsalva headaches or other neurological symptoms, which might point to a Chiari or syringomyelia state, should be investigated as soon as practicable after the birth.