Arnold Chiari malformations (ACM) are a group of congenital anomalies with herniation of the cerebellum through the foramen magnum and downward displacement of the lower pons and medulla (1). Type I ACM, which presents typically in adulthood, relates to cerebellar and cervical spinal cord involvement and can be associated with syringomyelia (2). The most common clinical manifestations are headaches, pain in the neck and upper extremities, ataxia, nystagmus, vertigo, upper extremity atrophy, and eventually bulbar symptoms and respiratory impairment with inspiratory stridor, reflecting tenth nerve palsy (3). Seizures have also recently been associated with type I ACM (4). Patients are more likely to be symptomatic if the tonsillar herniation is larger than 5 mm (5) and are invariably symptomatic if it is more than 12 mm (6) on sagittal magnetic resonance imaging (MRI). Increased intracranial pressure (ICP) has been reported (2) in type I ACM with syringomyelia. It has been suggested that increased brain turgor in these patients may occur, which could interfere with cerebrospinal fluid (CSF) absorption resulting in increased ICP (7).
Type II ACM, which presents in infancy, is associated with myelomeningocele. Symptoms include stridor, episodic apnea, depressed or absent gag reflex, nystagmus, and spastic upper extremity weakness. A ventriculoperitoneal shunt is often placed to treat hydrocephalus while repairing the myelomeningocele. Type III ACM involves caudad displacement of the cerebellum and brainstem into a high cervical myelomeningocele, and type IV consists of cerebellar hypoplasia without herniation.
There are no firm recommendations regarding anesthetic management of parturients with ACM. Fear of herniation should probably not be of concern for patients having had surgical decompression; however, few reports of neuraxial anesthesia for Cesarean delivery have been published. We describe the successful use of spinal anesthesia for Cesarean delivery in a patient with a surgically corrected type I ACM.
A 31-yr-old, gravida 2 para 1, 65 kg, 155 cm parturient was scheduled for a repeat Cesarean delivery at 37 wk gestational age. She had undergone cardiac surgical repair of an atrial septal defect in 1983 and has been asymptomatic since then. Nonetheless, because of her cardiac history, an elective Cesarean delivery with a vertical abdominal incision was performed uneventfully under general anesthesia in 1991.
In 1999, she was diagnosed with partial temporal lobe epilepsy and treated with carbamazepine (Tegretol®, Novartis, Basal, Switzerland). She was further investigated because of one generalized seizure and complaints of headaches, vertigo, and nausea. Vertical nystagmus was found on neurological examination. Type I ACM with cerebellar tonsils descending to C3 without syringomyelia was diagnosed by MRI. She underwent surgical osteodural decompression of C0-1-C2 with satisfactory CSF flow. Follow-up revealed exacerbation of the vertigo with gait instability and headaches. Normal CSF circulation was found on a repeat computed tomography scan. Switching the antiepileptic treatment to lamotriginum (Lamictal®) improved symptoms but nystagmus persisted.
The obstetric plan for this pregnancy was an elective Cesarean delivery because of the previous Cesarean delivery, for which the patient was requesting neuraxial anesthesia. After consulting with the neurosurgical team, it was determined that a spinal anesthetic was not contraindicated because a dural puncture should neither impair CSF flux nor precipitate bulbar compression.
The course of this pregnancy had been unremarkable except for an asymptomatic gestational thrombocytopenia. When she was admitted to the labor room, her platelet count was 90,000/mL. Neurological examination confirmed a persisting nystagmus and hyperreflexia of the lower limbs. Her baseline blood pressure (BP) on arrival into the operating room was 125/70 mm Hg. Spinal anesthesia was performed in the sitting position at the L2-3 space with a 27-gauge Whitacre needle. The procedure was uneventful, with no paresthesiae or pain on injection of 12.5 mg of hyperbaric bupivacaine and 25 μg of fentanyl. The smallest BP measure over the next 20 min was 100/50 mm Hg, and she received a total of 20 mg of ephedrine and 100 μg phenylephrine IV. A healthy female baby of 2930 g was delivered 28 min after the spinal injection. Apgar scores were 9/10/10; umbilical arterial and venous cord blood pH value measures were 7.19 and 7.37, respectively.
Postoperative analgesia was provided with patient-controlled analgesia with IV morphine, and the patient was monitored for 48 h in the intermediate care unit, with no exacerbation of her neurological status. She was discharged 7 days later and was extremely satisfied with the anesthetic procedure. One month postpartum, her neurological symptoms remained stable. This is the first report of a spinal anesthetic for Cesarean delivery in an epileptic patient with an operated type I ACM.
The use of neuraxial anesthesia in patients with type I ACM with or without syringomyelia has been reported in several cases of obstetric deliveries (8–12) and in one small retrospective case series (13). In two case reports, the ACM was unknown at the time of delivery and only diagnosed subsequently because of adverse neurological outcomes (8,10). In the first case, spinal anesthesia was performed for Cesarean delivery; a postdural puncture headache was unsuccessfully treated with a blood patch on Day 6 postpartum, and subsequent MRI resulted in the diagnosis of type I ACM. After prolonged steroid therapy, the postdural puncture headache resolved (10). In the second case, an inadvertent dural puncture during labor analgesia was complicated two weeks later by nystagmus and oscillopsia; a type I ACM was diagnosed and treated with decompressive surgery (8). Since then, two publications reported the uneventful use of epidural anesthesia for Cesarean deliveries in women with diagnosed type 1 ACM: one with pregnancy-induced hypertension (9) and the other with symptomatic syringomyelia (11). In women with syringomyelia, most published cases report the use of general anesthesia, chosen over regional anesthesia mainly because of medico-legal concerns and fear of CSF pressure fluctuations (14–17). However, once again, neurological complications reported after anesthetic procedures in association with syringomyelia seem to have revealed unknown asymptomatic neuropathies rather than having presented as complications of neuraxial anesthesia per se(18,19).
Our patient had undergone surgical decompression of a type I ACM without syringomyelia. She was also diagnosed with partial epilepsy with one episode of generalized seizure. It has been hypothesized that cerebral microdysgenesias or, alternatively, cerebellar dysfunction, could underlie epileptogenesis in subjects with type I ACM (20,21). She had had a successful surgical repair of an atrial septal defect. The association of ACM with congenital cardiac defects is not described in the literature.
After seeking neurosurgical advice to confirm that a dural puncture in this case would neither cause herniation of the cerebellum nor adversely alter ICP, we elected to perform a spinal rather than an epidural anesthetic. Our belief was that spinal anesthesia would reduce the risk of local anesthetic toxicity and avoid the risk of CSF leakage during an inadvertent wet tap. In addition, a single shot spinal anesthetic with hyperbaric bupivacaine and only fentanyl may be more beneficial in the detection of neurologic disturbances when compared with an epidural that required a repeated dosing. Theoretical concerns with spinal anesthesia (or inadvertent dural puncture) in uncorrected or symptomatic patients with type I ACM are because of the potential for (a) compression of structures at the level of foramen magnum, (b) increased ICP or obstructive hydrocephalus, and (c) intramedullary cervical cord syndrome.
If the type I ACM had not been surgically corrected, and there had been no increased ICP, an epidural anesthetic would have been the technique of choice. With signs of increased ICP, general anesthesia would be preferable over any type of regional anesthetic. However, with the need to perform rapid-sequence induction, provide hyperventilation, avoid neck hyperextension that might further compress the brainstem, and because of the risk of possible vocal cord paralysis and stridor caused by traction on cranial nerves, general anesthesia for type I ACM with increased ICP can be particularly challenging.
The unlikely possibility of tentorial herniation with bulbar compression requiring an urgent surgical intervention after spinal anesthesia was discussed with the patient, as were the usual risks of spinal headache and peripheral neurological impairment involving the lower limbs. These risks and the necessity for repeated neurological evaluations and assessments of sensory-motor function in the immediate postanesthetic period and the following 48 hours were understood and accepted by the patient.
The successful management of this case, including a multidisciplinary approach, suggests that spinal anesthesia can be considered in women with corrected type I ACM.
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