Chiari, Syringomyelia & Pregnancy

Chiari malformations can come to light – or “present”, to use medical terminology – at any age, from childhood to later life. The most commonly affected age (or “peak incidence”), however, is the early part of adult life. Women are affected more often than men, in a ratio of about two-to-one. This means, that many ladies with Chiari malformation may plan to become pregnant when already knowing that they have a Chiari malformation, with or without an associated syringomyelia.

Most people with Chiari malformation will know, from personal experience, about the so-called “pressure dissociation” headaches that are so characteristic of the condition. Typically brought on by coughing, sneezing, straining, laughing or bending over, these headaches, although short lived, are very intense and unpleasant. Most mothers-to-be will also know about what is involved in childbirth, in terms of “bearing down” – what obstetricians call the “second stage of labour”. It is no wonder, therefore, that both obstetricians and their patients can become concerned that natural childbirth – i.e. a normal “vaginal delivery” – might be an unpleasant experience for the mother, if not even a risky one.

In the past, when approached by obstetricians for help on this matter, neurosurgeons tended to advise against normal delivery, for pregnant ladies who were known to have a Chiari malformation. Caesarean section was favoured instead. In recent years views have changed and it is now often suggested that a pregnancy can be managed along normal obstetric lines. Such advice, however, is dependent upon a full understanding of the individual mother’s neurological condition and the state of her internal anatomy in relation to her Chiari malformation, as well as the state of any associated syringomyelia. In the latter case the size of the cavity may have a bearing upon the advice offered.

Another question that arises in relation to childbirth is the use of epidural anaesthesia. This form of pain control relies upon the spinal nerves being bathed in local anaesthetic, injected outside the membranes lining the spinal canal. From time to time, however, the needle used to inject the anaesthetic can inadvertently puncture these membranes, resulting in leakage of the cerebrospinal fluid which bathes and supports the brain and spinal cord. The resulting loss of buoyancy may cause the brain to “slump” somewhat, causing the cerebellar tonsils to impact further into the foramen magnum. The concern then is that such movement could lead to potentially harmful, even lethal compression of the brain stem. In truth, there is debate amongst neurosurgical experts as to just how great are such risks but obstetric anaesthetists will often seek advice from neurosurgeons on this question.

As ever, the Ann Conroy Trust cannot and does not offer advice to individual patients on matters such as these. We nevertheless hope that these notes will help expectant mothers with Chiari and/or syringomyelia to understand some of the issues in question. The important point is that the health professionals supervising the pregnancy – midwives, obstetricians and anaesthetists – are made aware about the Chiari/syrinx, so that they can liaise with the mother’s neurosurgeon (or an appropriate neurosurgeon) and decide upon the best way of managing the forthcoming birth.