Case Study
A 31-year-old gravida 1, para 0 woman with a recently diagnosed intracranial mass presented for planned cesarean delivery at 37 weeks’ gestation. On admission, she denied headache, nausea, vomiting, seizure activity, visual changes, and altered level of consciousness. A recent MRI confirmed a 2 × 3 cm lesion consistent with low-grade glioma in the anterior frontal lobe without mass effect. The patient’s medical history was otherwise unremarkable.
The patient requested to be “awake” during the procedure, and a spinal anesthetic was administered on first attempt with a small-gauge atraumatic needle at the L3–L4 interspace after consultation with her neurosurgeon. A T4 surgical level was attained, and a healthy boy was delivered without incident. The patient underwent surgical resection of the glioma (WHO grade II) under general anesthesia 3 weeks later, followed by radiation therapy and chemotherapy.
Key Points
This patient with a known intracranial lesion requested regional anesthesia for her planned cesarean delivery.
Concern for herniation after deliberate or accidental dural puncture (ADP) is often cited as a reason to avoid neuraxial techniques in parturients with intracranial tumors or vascular lesions, even in the absence of clinical and radiographic evidence of increased intracranial pressure.1
This patient had an uneventful spinal anesthetic after a multidisciplinary discussion about her care.
Discussion
Neuraxial anesthesia is considered the technique of choice for cesarean delivery, when feasible, for several reasons, including improved pain management and maternal satisfaction, avoidance of volatile agent–induced uterine relaxation and fetal depression, prevention of intraoperative recall in a high-risk patient population, reduced fetal exposure to the potentially toxic effects of general anesthetics,2 and avoidance of instrumentation of the parturient’s airway. It also allows the patient and her partner to experience the birth of their child. More broadly, the increased use of neuraxial techniques for labor and delivery has been associated with a reduction in airway and aspiration-related morbidity and mortality in serial obstetric safety audits.3
However, the use of spinal or epidural anesthesia for cesarean delivery is not without risks, including the possibility of block failure with subsequent conversion to general anesthesia, high or total spinal, postdural puncture headache (PDPH) in a population at increased risk for this untoward complication, and the less common risks of nerve damage, epidural hematoma, and infection. In patients with clinically significant intracranial pathology, the initiation of neuraxial anesthesia may also carry the risk of significant brain tissue shifts (i.e., herniation) after dural puncture.
Case-by-case assessment by the obstetric anesthesiologist and neurologist or neurosurgeon of the risk of neurologic deterioration with spinal or epidural anesthesia and analgesia in parturients with intracranial lesions is strongly recommended. Although many factors should be taken into consideration, appropriate neuroimaging and knowledge of the following lesion characteristics are paramount: the type of intracranial lesion; its size, location, and growth rate; whether it obstructs CSF flow at or above the foramen magnum; and whether it causes intracranial tissue shifts. This information is required to properly assess the risks of neuraxial or general anesthesia in these patients and to plan accordingly.
Lesion Size, Location, and Growth Rate
Not all intracranial lesions place the patient at risk for complications from neuraxial analgesia and anesthesia. In this Case Study, the tumor is small, without significant mass effect. Its location in an area remote from the foramen magnum and CSF pathways reduces the risks of partial or complete foramen magnum obstruction or ventricular compression, permitting translocation of the CSF from the cranium to the spinal part of the neuraxis after dural puncture. By contrast, intracranial lesions that impede the free flow of CSF and cause obstructive (or noncommunicating) hydrocephalus, such as those located in the posterior fossa, near the third ventricle or cerebral aqueduct, or at the foramen magnum, can place a patient at significant risk of herniation. Similarly, large or fast-growing intracranial lesions exert mass effect and displace the intracranial contents around them; brain tissue rather than CSF will be displaced caudally if there is a sudden loss of CSF from a lumbar dural puncture.
The Monro-Kellie doctrine provides the explanation for these assertions: the total intracranial volume (comprised of brain tissue, CSF, and cerebral blood volume) remains constant within the noncompliant bony skull. This means that an increase in the volume of one element causes a compensatory decrease in the volume of another. If the intracranial volume increases because of a small, remotely located intracranial lesion, the intracranial pressure remains relatively unchanged as long as CSF can be displaced caudally (Figure 46.1). However, once this compensatory mechanism is exhausted or can no longer function because of obstruction, even a small increase in volume from peritumoral edema or bleeding or from a transient increase in intracranial blood or CSF (with physiologic maneuvers such as coughing, vomiting, gagging, or Valsalva) will cause an increase in ICP.
In this patient’s case, the small, slow-growing tumor in the frontal lobe without clinical or radiographic evidence of CSF obstruction or significant mass effect presents a low likelihood of herniation after dural puncture. Therefore, it may be reasonable to proceed with spinal anesthesia with a small-gauge needle, preferably after consultation with a neurologic expert. Even a dural puncture with a large-gauge epidural needle would most likely result in normal flow of CSF rather than herniation of brain tissue in this setting. Similarly, the transient increase in ICP associated with epidural catheter dosing should also be well tolerated (see below).
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