Pre-existing Neurologic Disorders
Neuraxial analgesia/anesthesia should not be automatically denied to pregnant women with preexisting neurologic disorders. Ideally, these patients should be evaluated in a high-risk obstetric clinic during pregnancy. This allows for a thorough history and physical examination to gauge the extent and severity of the problem (particularly the distribution of sensory and motor deficits), time for additional investigations and imaging, and consultation with other experts, if necessary.
Discussion with the patient should include the impact of pregnancy and delivery on the disease process, options for analgesia and anesthesia during labor and delivery, and the risks and benefits of each relative to the disorder. Unfortunately, these patients may be seen for the first time when they are in labor and requesting analgesia.
1. Diabetes Mellitus
These patients may have peripheral neuropathy, but there is no evidence that this will worsen with neuraxial analgesia/anesthesia. Diabetic patients are at increased risk for infection, including epidural abscess.
2. Multiple Sclerosis
About 1 in 1,000 women of childbearing age have multiple sclerosis (MS), a disease that predominantly affects women and is usually diagnosed between 20 and 45 years of age. A normal obstetric course and delivery is anticipated in these patients. Symptoms of the disease may improve during pregnancy, but there is an increased relapse rate after delivery, potentially causing confusion when evaluating neurologic status after a neuraxial block for labor and delivery.
There is inconclusive evidence that spinal anesthesia negatively impacts demyelinating conditions such as MS, but epidural anesthesia is a viable option. Should it be required, general anesthesia is not contraindicated.
3. Myasthenia Gravis
Believed to occur in 1 in 20,000 pregnancies, it commonly affects women in their 30s and is characterized by skeletal muscle weakness that worsens with activity. The response to pregnancy and delivery is variable, with approximately 40% of patients experiencing an exacerbation during pregnancy and 30% postpartum.
Epidural analgesia is not contraindicated for labor and may actually help reduce muscle fatigue. Epidural anesthesia or low dose combined spinal/epidural are useful techniques for cesarean delivery, avoiding an unpredictably high block with spinal anesthesia that could compromise respiratory function, and also avoiding the potential respiratory complications associated with general anesthesia.
4. Human Immunodeficiency Virus (HIV)
Concerns about transmitting the virus into the CNS may prevent HIV-positive obstetric patients from receiving appropriate spinal or epidural anesthesia. This fear is unfounded, as HIV is a neurotropic virus which infects the central nervous system in the early stages of the disease.
Peripheral neuropathy may be present secondary to the disease or as a result of antiretroviral treatment. The extent of the neuropathy should be documented prior to the neuraxial procedure. Postdural puncture headache in HIV-positive patients can be safely treated with an epidural blood patch using autologous blood.
5. Spina Bifida
There are many reports of successful spinal and epidural anesthesia in patients with spina bifida occulta and cystica. However, neuraxial procedures have a higher rate of complications in this population, particularly in patients with spina bifida cystica, and anesthesia providers may be rightfully concerned about performing a neuraxial block. There is an increased risk of accidental dural puncture due to abnormal anatomy, and unpredictable, patchy, or inadequate epidural blocks. Smaller volumes of local anesthetic are recommended for epidural top-ups due to the risk of excessive cranial spread.
A detailed history and physical is important to establish the site of the defect and extent of neurologic dysfunction. Imaging is essential in symptomatic patients or those with cutaneous manifestations in order to establish the presence of a tethered or low-lying spinal cord. A tethered cord may increase the risk of spinal cord injury due to direct trauma with a spinal or epidural needle. It is recommended to perform the block away from the site of the lesion. Associated kyphosis, scoliosis, and previous surgery present additional challenges.
What's the Evidence?
Reynolds, F. “Neurologic Complications of Pregnancy and Neuraxial Anesthesia”. Chestnut's Obstetric Anesthesia: Principles and Practice. 2009.
Zakowski, MI, Ramanathan, S. Neurologic Deficits following Labor and Delivery. A Practical Approach to Obstetric Anesthesia. 2009.
Moen, V, Irestedt, L. “Neurological complications following central neuraxial blockades”. Curr Opin Anesthesiol . vol. 21. 2008. pp. 275-280. (These are all good overviews of the topic from a variety of experts in the field.)
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