Medically Challenging Cases

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Symptomatic Arnold Chiari Malformation in a Gravid Female

Authors: Dr. Christopher S. Manfred (Department of Anesthesiology, Dartmouth Hitchcock Medical Center) and Dr. Brian Sites (Department of Anesthesiology, Dartmouth Hitchcock Medical Center)

Introduction

This is a case of a symptomatic Arnold Chiari malformation in a gravid female with a suspected difficult airway. The patient is a 28 year-old Gravida 1 Para 0 who was referred from an outside institution. Her past medical history is significant for a previously unknown asymptomatic Type I Arnold Chiari malformation that recently became symptomatic after a motor vehicle accident one year prior. Since the accident she has experienced headaches, upper extremity/neck paresthesias, and multiple pre-syncopal events while performing her activities of daily living. She is no longer able to cough, defecate, or extend her neck without becoming symptomatic. She is pregnant and has been evaluated by neurosurgery with the recommendation of delaying any surgical intervention until after delivery. Her obstetrical team was going to schedule a primary elective c-section in order to prevent her from pushing. An anesthesiology consultation was obtained and the patient was suspected to be a difficult airway. She was thus transferred to a tertiary care facility for further care.

Case Report

The patient was seen in the anesthesia pre-admission testing clinic for evaluation. On further questioning it was uncovered that the patient experienced symptoms including mild upper extremity paresthesias, occipital headaches, and dizziness, and syncopal events. She would become symptomatic with minor extensions of her neck, with supine positioning, during valsalva maneuvers (such as having bowel movements, coughing, or laughing), or with minimal exertion. Her pregnancy has been otherwise uncomplicated. On review of systems, she has been troubled by persistent GERD throughout pregnancy that is being treated with antacids. The only other medicine she takes is a daily multi-vitamin. She has not had a previous anesthetic and denies family history of anesthetic complications or malignant hyperthermia. On physical exam, the patient was a thin gravid female. Paresthesias and headaches were able to be elicited with minor neck extension and supine positioning. She had a Mallampati IV airway with less than 2 finger breadths mouth opening, prominent front incisors, 2 finger breadths thyromental distance, inability to extend her jaw, and was unable to extend her neck secondary due to Chiari symptoms. The rest of her physical exam was unremarkable. After discussion with the patient regarding risks and benefits to the different methods of providing anesthesia for a c-section, the plan was formulated to attempt a single shot spinal block with the smallest diameter needle available. In the event a spinal block was unable to be performed, a general anesthetic with an awake fiber optic intubation was planned. The night prior to the patient’s scheduled c-section, she presented in early spontaneous labor and was taken to the operating room for a c-section. The anesthesia team on at that time was able to successfully place a spinal bloc using a 25G pencil-point needle (after one unsuccessful attempt with a 27G pencil-point) containing 1.5ml of hyperbaric 0.75% bupivacaine with an epinephrine wash, 100 mcg of preservative free morphine sulfate, and 10 mcg of fentanyl. The patient experienced minor symptoms during delivery of the infant, but otherwise remained asymptomatic throughout the procedure.

Discussion

This case was difficult for a number of reasons. First, given the fact the patient has a severely symptomatic Chiari malformation that is currently unable to be corrected due to her gravid status, she is at increased risk of herniation of cerebellar/brainstem tissue into her spinal canal with minor increases in ICP or with decreases in her spinal CSF pressure. Secondly, the patient appeared to have an extremely difficult airway exam which would require a careful awake fiber optic intubation. Upon review of the available literature, there are multiple case reports of women with this condition who underwent successful neuraxial or general anesthesia, but none were reported to be as severely symptomatic as our present patient. It was felt that an attempt at epidural anesthesia was contraindicated due to the increased risk of adverse neurological outcome in the event of an unintentional dural puncture with an 18G tuohy needle. Further, a general anesthetic would likely be greatly complicated by her airway status. Coughing during an awake fiber optic intubation could pose a distinct risk of herniation. The anesthesia team felt that the best anesthetic would be a single shot spinal block performed by the most experienced practitioner and with the smallest diameter pencil-point (non-cutting) needle. Little if any CSF should be lost, and the technique would actually be adding volume to the dural sac. The risk of CSF leak/post dural puncture headache with subsequent neurological deterioration would thus be minimized. Further, the patient would be awake, protecting her own airway, and able to report any changes in her neurological status.

References

Semple DA, McClure JH. Arnold-chiari malformation in pregnancy. Anaesthesia. 1996 Jun; 51(6):580-2 Nel MR, Robson V, Robinson PN. Extradural anesthesia for caesarean section in a patient with syngriomyelia and Chairi type-I anomaly. Br J Anaesth. 1998 Apr; 80(4):512-5 Landau R, Giraud R, Delrue V, Kern C. Spinal anesthesia for cesarean delivery in a woman with surgically corrected type-I Arnold Chiari malformation. Anesth analg. 2003 Jul; 97(1):252-5 Chantigian RC, Koehn MA, Ramin KD, Warner MA. Chairi I malformation in parturients. J Clin Anesth. 2002 May; 14(3):201-5